ANATOMY OF THE FACIAL NERVE WITH CONGENITAL ANOMALIES

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// ─────────────────────────────────────────────────────────────────────────────
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  // ── TITLE PAGE ─────────────────────────────────────────────────────────────
  new Paragraph({
    children: [new TextRun({ text: "ANATOMY OF THE FACIAL NERVE", bold: true, size: 52, color: NAVY })],
    alignment: AlignmentType.CENTER, spacing: { before: 800, after: 200 },
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  new Paragraph({
    children: [new TextRun({ text: "WITH CONGENITAL ANOMALIES", bold: true, size: 40, color: BLUE })],
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    children: [new TextRun({ text: "50-Mark Answer | RGUHS University Standard", size: 26, color: TEAL, italics: true })],
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  new Paragraph({
    children: [new TextRun({ text: "ENT & Head-Neck Surgery | Postgraduate Study Guide", size: 22, color: "666666" })],
    alignment: AlignmentType.CENTER, spacing: { after: 600 },
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  new Paragraph({
    children: [new TextRun({ text: "Sources: Cummings Otolaryngology · Scott-Brown's · Shambaugh Surgery of the Ear", size: 20, italics: true, color: "555555" })],
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  new Paragraph({
    children: [new TextRun({ text: "Bailey & Love · Gray's Anatomy · Dhingra · Hazarika · Recent PubMed Literature", size: 20, italics: true, color: "555555" })],
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  pageBreak(),

  // ── SECTION 1: INTRODUCTION ─────────────────────────────────────────────────
  h1("PART I – INTRODUCTION & OVERVIEW"),
  body("The facial nerve (CN VII) is the nerve of the second branchial arch (Reichert's cartilage). It is the most complex cranial nerve, carrying five distinct fiber types, and traverses the longest bony canal of any cranial nerve – the fallopian canal (also called the facial canal or Fallope's canal). Its intimate relationship with the temporal bone, parotid gland, and skull base makes detailed anatomical knowledge essential for every otolaryngologist and head-neck surgeon."),
  spacer(),

  ...infoBox([
    "⚡ KEY EXAM FACT",
    "The facial nerve is the only cranial nerve that traverses a bony canal entirely within a bone (the temporal bone). The labyrinthine segment is the SHORTEST (4 mm) and NARROWEST portion.",
  ], "E8F4FD", "2E74B5"),

  spacer(),

  // ── SECTION 2: NUCLEI ───────────────────────────────────────────────────────
  h1("PART II – NUCLEI AND FIBER COMPOSITION"),
  h2("A. Three Brainstem Nuclei"),

  makeTable(
    ["Nucleus", "Location", "Fiber Type", "Function"],
    [
      ["Motor nucleus (VII)", "Caudal pons", "SVE – Special Visceral Efferent", "Muscles of facial expression, stapedius, stylohyoid, posterior belly digastric"],
      ["Superior salivatory nucleus", "Dorsal to motor nucleus, pons", "GVE – General Visceral Efferent", "Preganglionic parasympathetics → lacrimal, nasal, submandibular, sublingual glands"],
      ["Nucleus of solitary tract (NTS)", "Medulla oblongata", "SVA + GVA", "Taste (anterior 2/3 tongue, palate); visceral sensation (nose, pharynx, palate)"],
    ]
  ),

  spacer(),
  ...infoBox([
    "📌 Upper Motor Neuron vs. Lower Motor Neuron Palsy",
    "The SUPERIOR portion of the facial motor nucleus (frontalis, orbicularis oculi) receives BILATERAL cortical input.",
    "Therefore in UMN lesion: forehead is SPARED (bilateral supply).",
    "In LMN lesion: forehead is AFFECTED (entire ipsilateral nerve is damaged).",
  ], "FFF9E6", "FFC107"),

  spacer(),
  h2("B. Five Fiber Types"),
  makeTable(
    ["Fiber Type", "Abbreviation", "Function", "Pathway"],
    [
      ["Special Visceral Efferent", "SVE", "Motor to facial expression, stapedius, stylohyoid, digastric", "Main trunk of CN VII"],
      ["General Visceral Efferent", "GVE", "Preganglionic parasympathetics", "GSPN → lacrimal gland; Chorda tympani → submandibular/sublingual"],
      ["Special Visceral Afferent", "SVA", "Taste", "Anterior 2/3 tongue via chorda tympani; soft palate/tonsil via GSPN"],
      ["General Somatic Afferent", "GSA", "Touch, proprioception", "EAC, concha auriculae; facial muscles"],
      ["General Visceral Afferent", "GVA", "Visceral sensation", "Mucosa of nose, pharynx, palate"],
    ]
  ),

  spacer(),
  pageBreak(),

  // ── SECTION 3: COURSE & SEGMENTS ───────────────────────────────────────────
  h1("PART III – COURSE AND SEGMENTS OF THE FACIAL NERVE"),
  body("Mnemonic: \"I Can Learn To Master Surgery\" = Intracranial, Canalicular, Labyrinthine, Tympanic, Mastoid, Stylomastoid/extratemporal"),

  spacer(),
  h2("Segment-by-Segment Summary Table"),

  makeTable(
    ["Segment", "Length", "Key Feature", "Surgical Landmark", "Branches"],
    [
      ["1. Intracranial (Cisternal)", "24 mm", "Traverses cerebellopontine angle (CPA) with nervus intermedius", "CPA; porus of IAC", "None (nervus intermedius joins here)"],
      ["2. Intracanalicular (Meatal)", "~8 mm", "Anterosuperior quadrant of IAC (\"Seven up, Coke down\")", "Bill's bar (vertical crest); crista falciformis", "None"],
      ["3. Labyrinthine", "4 mm (SHORTEST)", "Narrowest; no epineurium; watershed blood supply", "Bill's bar; meatal foramen", "GSPN at geniculate ganglion; 1st genu"],
      ["4. Tympanic (Horizontal)", "~13 mm", "Medial wall of middle ear; most dehiscences occur here", "Cochleariform process; oval window niche", "None (2nd genu at pyramidal eminence)"],
      ["5. Mastoid (Vertical)", "~20 mm (LONGEST)", "Behind EAC; most variable path, especially in congenital anomalies", "Pyramidal eminence; lateral SCC; short process incus", "Nerve to stapedius; chorda tympani"],
      ["6. Extratemporal", "Variable", "Exits stylomastoid foramen; enters parotid; divides into 5 branches", "Digastric muscle aponeurosis", "Posterior auricular N., digastric/stylohyoid, 5 terminal branches"],
    ]
  ),

  spacer(),
  h2("Detailed Notes by Segment"),

  h3("Labyrinthine Segment (Most Vulnerable)"),
  bullet("Shortest (4 mm) and narrowest segment (meatal foramen)"),
  bullet("No fibrous sheath / epineurium → susceptible to edema and compression"),
  bullet("Watershed zone: AICA (vertebrobasilar) meets petrosal branch of middle meningeal + stylomastoid artery (ECA system)"),
  bullet("Geniculate ganglion: thin/dehiscent bone in ~25% of ears; tethered by GSPN anteriorly"),
  bullet("First genu: acute posterior turn (~120°) at geniculate ganglion", 0, false),
  spacer(),

  h3("Tympanic (Horizontal) Segment"),
  bullet("Most common site of fallopian canal dehiscence – above oval window (55–66% of dehiscences)"),
  bullet("Bilateral dehiscence present in ~75% of cases (Shambaugh)"),
  bullet("Courses over cochleariform process (anterior) → oval window niche (posterior)"),
  bullet("Dehiscent nerve may prolapse into middle ear as a mass"),
  spacer(),

  h3("Mastoid (Vertical) Segment"),
  bullet("Most variable pathway – especially in congenital malformations"),
  bullet("Facial recess: lateral to facial nerve, medial to chorda tympani, inferior to incudal fossa → used in posterior tympanotomy"),
  bullet("Chorda tympani separates ~4–6 mm above stylomastoid foramen; ascends lateral to facial nerve"),
  spacer(),

  h3("Extratemporal Course"),
  bullet("Stylomastoid foramen is SUPERFICIAL in neonates/infants → risk in post-auricular/parotid surgery"),
  bullet("Posterior auricular nerve (occipitalis, posterior auricular muscle)"),
  bullet("Branches to posterior belly digastric + stylohyoid"),
  bullet("Enters parotid → divides into Temporofacial and Cervicofacial divisions"),
  bullet("Five terminal branches: Temporal, Zygomatic, Buccal, Marginal Mandibular, Cervical"),
  bullet("Mnemonic: \"Two Zebras Bit My Cat\""),
  spacer(),

  h2("Surgical Landmarks of Facial Nerve by Segment (Cummings)"),
  makeTable(
    ["Segment", "Primary Surgical Landmark(s)"],
    [
      ["Labyrinthine segment", "Vertical crest (Bill's bar)"],
      ["Geniculate ganglion", "Retrograde dissection of GSPN (middle fossa approach)"],
      ["Tympanic segment", "Cochleariform process (anterior); oval window niche (posterior)"],
      ["Second genu", "Oval window"],
      ["Mastoid segment", "Pyramidal eminence; lateral SCC prominence; short process incus; chorda tympani nerve"],
      ["Stylomastoid foramen", "Cephalic edge and aponeurosis of posterior belly digastric muscle"],
    ]
  ),

  spacer(),
  pageBreak(),

  // ── SECTION 4: BRANCHES ─────────────────────────────────────────────────────
  h1("PART IV – INTRATEMPORAL BRANCHES"),

  makeTable(
    ["Branch", "Origin", "Course", "Function"],
    [
      ["Greater Superficial Petrosal Nerve (GSPN)", "Geniculate ganglion (anterior surface)", "MCF floor → foramen lacerum → vidian nerve → pterygopalatine ganglion", "Secretomotor: lacrimal gland, nasal/palatal seromucinous glands; taste from soft palate"],
      ["Nerve to Stapedius", "Mastoid segment near pyramidal eminence", "Via tiny canaliculus to stapedius muscle", "Motor: stapedius muscle (protective stapedial reflex)"],
      ["Chorda Tympani", "Mastoid segment ~4–6 mm above stylomastoid foramen", "Ascends in own canal → iter chordae posterius → crosses medial to malleus, lateral to incus → iter chordae anterius → petrotympanic fissure → joins lingual nerve", "SVA: taste anterior 2/3 tongue; GVE: secretomotor to submandibular & sublingual glands"],
    ]
  ),

  spacer(),
  pageBreak(),

  // ── SECTION 5: BLOOD SUPPLY ─────────────────────────────────────────────────
  h1("PART V – BLOOD SUPPLY"),

  makeTable(
    ["Segment", "Arterial Supply", "System"],
    [
      ["Labyrinthine / meatal segment", "Labyrinthine artery (branch of AICA)", "Vertebrobasilar"],
      ["Geniculate ganglion + tympanic segment", "Petrosal branch of middle meningeal artery", "External carotid (via middle meningeal)"],
      ["Mastoid segment + stylomastoid foramen", "Stylomastoid artery (branch of posterior auricular artery)", "External carotid"],
    ]
  ),

  spacer(),
  ...infoBox([
    "⚡ WATERSHED ZONE (Labyrinthine segment)",
    "The labyrinthine segment is the junction between vertebrobasilar and ECA supply.",
    "This explains why Bell's palsy (presumed viral/ischemic) maximally affects this segment.",
    "Combined with lack of epineurium and narrow canal → greatest vulnerability to compressive injury.",
  ], "FFE8E8", "C00000"),

  spacer(),
  pageBreak(),

  // ── SECTION 6: TOPOGRAPHIC DIAGNOSIS ───────────────────────────────────────
  h1("PART VI – TOPOGRAPHIC DIAGNOSIS FLOWCHART"),

  ...codeBox([
    "TOPOGRAPHIC DIAGNOSIS OF FACIAL NERVE LESION",
    "",
    "  Is LACRIMATION impaired? (Schirmer's test)",
    "       │",
    "       ├── YES → Lesion at or PROXIMAL to GSPN origin",
    "       │         (Geniculate ganglion or above; labyrinthine / IAC / CPA)",
    "       │",
    "       └── NO  → Lesion DISTAL to geniculate ganglion",
    "                   │",
    "                   ├── Is STAPEDIAL REFLEX absent?",
    "                   │      YES → Lesion between GSPN and nerve to stapedius",
    "                   │            (Tympanic / proximal mastoid segment)",
    "                   │",
    "                   └── NO  → Is TASTE affected? (chorda tympani)",
    "                               YES → Lesion between stapedius nerve and",
    "                                     chorda tympani (mastoid segment)",
    "                               NO  → Lesion at or DISTAL to stylomastoid foramen",
    "                                     (purely motor; parotid / extratemporal)",
  ]),

  spacer(),
  makeTable(
    ["Level of Lesion", "Lacrimation", "Stapedial Reflex", "Taste", "Example"],
    [
      ["CPA / IAC / Labyrinthine", "Impaired", "Absent", "Impaired", "Acoustic neuroma, Bell's palsy (geniculate)"],
      ["Tympanic segment", "Normal", "Absent", "Impaired", "Otitis media, cholesteatoma"],
      ["Mastoid segment", "Normal", "Normal (if above pyramidal)", "Impaired", "Mastoiditis, cholesteatoma"],
      ["Stylomastoid foramen / extratemporal", "Normal", "Normal", "Normal", "Parotid tumor, forceps delivery trauma"],
    ]
  ),

  spacer(),
  pageBreak(),

  // ── SECTION 7: CONGENITAL ANOMALIES ─────────────────────────────────────────
  h1("PART VII – CONGENITAL ANOMALIES OF THE FACIAL NERVE"),

  h2("A. Classification"),

  ...codeBox([
    "CLASSIFICATION OF CONGENITAL ANOMALIES",
    "",
    "  CONGENITAL ANOMALIES OF THE FACIAL NERVE",
    "                  │",
    "       ┌──────────┴──────────────────────────────────┐",
    "       │                                              │",
    "  NUCLEAR / CENTRAL                        PERIPHERAL / INTRATEMPORAL",
    "  ANOMALIES                                ANOMALIES",
    "       │                                              │",
    "  ┌────┴─────────────┐                  ┌────────────┴──────────────────┐",
    "  Moebius syndrome    CHARGE             │                               │",
    "  Dystrophia          OAV/Goldenhar   ANOMALIES OF                ANOMALIES OF",
    "  myotonica           MRS             COURSE/POSITION             CANAL/NERVE",
    "  CULLP               Poland syndrome      │                           │",
    "                                  ┌────────┴──────┐          ┌─────────┴──────┐",
    "                               Aberrant       Bifurcation  Dehiscence    Agenesis/",
    "                               course         /Duplication              Aplasia",
  ]),

  spacer(),

  // ── NUCLEAR ANOMALIES ───────────────────────────────────────────────────────
  h2("B. Nuclear / Central Anomalies"),

  h3("1. Moebius Syndrome (Moebius Sequence)"),
  ...infoBox([
    "DEFINITION: Agenesis or hypoplasia of CN VI (abducens) and CN VII (facial) motor nuclei in the pons.",
    "Key feature: Bilateral facial palsy + bilateral abducens palsy (horizontal gaze paralysis)",
  ], "E8F4FD", "2E74B5"),
  spacer(),

  bullet("Clinical features:", 0, true),
  bullet("Mask-like face: inability to smile, frown, whistle, or close eyes", 1),
  bullet("Bilateral ophthalmoplegia: horizontal gaze palsy (abducens)", 1),
  bullet("Feeding difficulty / drooling in neonates", 1),
  bullet("Dysarthria and dysphagia", 1),
  bullet("Possible involvement of CN III, V, IX, X, XII", 1),
  bullet("Associated limb defects: Poland sequence, club foot (in some cases)", 1),
  spacer(),
  bullet("Pathogenesis:", 0, true),
  bullet("Interruption of blood supply (subclavian artery disruption) to rhombomere 4 during fetal development", 1),
  bullet("Genetic: autosomal dominant mutations in MBS1 (13q12.2) and MBS2 (3q21-q22)", 1),
  spacer(),
  bullet("Investigation:", 0, true),
  bullet("MRI brain: absent/hypoplastic facial colliculi (floor of 4th ventricle)", 1),
  bullet("EMG: absent potentials at birth (distinguishes from birth trauma – which shows declining amplitude)", 1),
  spacer(),
  bullet("Management:", 0, true),
  bullet("Free muscle transfer (gracilis, pectoralis minor) for dynamic smile restoration", 1),
  bullet("Gold weights for upper eyelid loading (eye closure)", 1),
  bullet("Orthoptic treatment for strabismus; speech therapy", 1),
  spacer(),

  h3("2. CHARGE Association / Syndrome"),
  bullet("C = Coloboma, H = Heart defects, A = choanal Atresia, R = Retarded growth/development, G = Genital hypoplasia, E = Ear anomalies"),
  bullet("Facial nerve palsy due to aplasia of the facial nerve canal and nerve agenesis"),
  bullet("Associated findings: absent semicircular canals, cochlear hypoplasia, temporal bone malformations"),
  bullet("Genetics: CHD7 gene mutation (8q12.2)"),
  bullet("Management: Multidisciplinary; BAHA or cochlear implant for hearing; eye/cardiac care"),
  spacer(),

  h3("3. Dystrophia Myotonica (Steinert's Disease)"),
  bullet("Progressive autosomal dominant distal myopathy (CTG repeat expansion, chromosome 19q)"),
  bullet("Bilateral facial palsy WITHOUT abducens palsy (distinguishes from Moebius)"),
  bullet("Muscle wasting: facial, sternocleidomastoid, masticatory muscles → 'swan-neck' appearance"),
  bullet("Other features: myotonia, cataracts, cardiac conduction defects, diabetes"),
  spacer(),

  h3("4. Congenital Unilateral Lower Lip Palsy (CULLP) / Asymmetric Crying Facies"),
  ...infoBox([
    "⚡ IMPORTANT: This is NOT a true facial nerve palsy!",
    "Cause: Hypoplasia or absence of the DEPRESSOR ANGULI ORIS muscle (not nerve damage).",
    "Presentation: Unilateral lower lip asymmetry ONLY when crying (lower lip not depressed on affected side).",
    "Association: Cardiac defects in ~10% of cases → mandatory echocardiogram + ECG in all cases.",
  ], "FFF3E0", "FF9800"),
  spacer(),

  h3("5. Oculo-Auriculo-Vertebral (OAV) Spectrum / Goldenhar Syndrome"),
  bullet("Abnormal formation of first AND second branchial arches"),
  bullet("Hemifacial microsomia: asymmetric underdevelopment of one side of face"),
  bullet("Facial nerve hypoplasia and/or aberrant course possible"),
  bullet("Associated: microtia, preauricular tags, conductive hearing loss, vertebral anomalies, epibulbar dermoids"),
  spacer(),

  h3("6. Melkersson-Rosenthal Syndrome"),
  bullet("Classic triad: Recurrent facial palsy + oro-facial oedema + fissured (scrotal) tongue"),
  bullet("Typically presents in childhood or adolescence; often recurrent"),
  bullet("Biopsy: non-caseating granulomatous inflammation (similar to Crohn's / sarcoidosis)"),
  bullet("Management: Steroids for acute attacks; cheiloplasty for persistent lip swelling"),
  spacer(),
  pageBreak(),

  // ── PERIPHERAL ANOMALIES ────────────────────────────────────────────────────
  h2("C. Peripheral / Intratemporal Anomalies"),

  h3("1. Fallopian Canal Dehiscence (Most Common Congenital Anomaly)"),
  ...codeBox([
    "SITES OF FALLOPIAN CANAL DEHISCENCE (by frequency):",
    "",
    "  1st: Tympanic segment ABOVE OVAL WINDOW  ← 55–66% of all dehiscences",
    "       (Bilateral in ~75% of cases – Shambaugh)",
    "  2nd: Distal tympanic segment / 2nd genu",
    "  3rd: Geniculate ganglion (thin bone, dehiscent in ~25% of ears – Cummings)",
    "  4th: Mastoid segment",
  ]),
  spacer(),
  bullet("Clinical significance:"),
  bullet("Exposes nerve to toxins/infection in otitis media → facial palsy in AOM or CSOM", 1),
  bullet("Prolapsed nerve may appear as a MIDDLE EAR MASS mimicking tumour", 1),
  bullet("Risk of inadvertent nerve damage during mastoid / middle ear surgery", 1),
  bullet("GSPN traction can cause intraoperative facial palsy", 1),
  spacer(),

  h3("2. Aberrant Course of the Facial Nerve"),
  makeTable(
    ["Anomaly", "Description", "Clinical Significance"],
    [
      ["Inferior displacement of tympanic segment", "Tympanic FN descends anterior + INFERIOR to oval window, overlying/covering the stapes footplate", "HIGHEST risk in stapedectomy – may make procedure impossible; HRCT mandatory before stapes surgery"],
      ["Anteroinferior course over promontory", "FN crosses the promontory, may overlie round window niche", "Risk during myringotomy / round window surgery"],
      ["Mastoid segment lateral bulge", "Nerve bulges more posterolaterally than normal, inferior to lateral SCC", "Risk during cortical mastoidectomy"],
      ["Lateral rotation in aural atresia", "Mastoid segment rotated laterally – ranges from minor obliquity to true horizontal course", "Most common dangerous variant in atresia surgery; pre-op HRCT is MANDATORY"],
      ["Superficial stylomastoid foramen in neonates", "Nerve exits skull base superficially in infants (immature temporal bone)", "High risk of FN injury in post-auricular/parotid surgery in neonates"],
    ]
  ),
  spacer(),

  h3("3. Bifurcation / Duplication of the Facial Nerve"),
  bullet("Rare but documented anomaly: vertical (mastoid) segment may be bipartite or tripartite (Shambaugh)"),
  bullet("Glastonbury et al. documented congenital bifurcation of the intratemporal facial nerve (Scott-Brown reference)"),
  bullet("Most common form: bifurcation in tympanic or mastoid segment with one aberrant trunk"),
  bullet("SURGICAL HAZARD: Surgeon may identify one division and cut the other, believing it to be the complete nerve"),
  bullet("FN monitoring is essential; careful complete identification of both trunks before proceeding"),
  spacer(),

  h3("4. Agenesis / Aplasia of the Facial Nerve"),
  bullet("Complete agenesis: Total absence of facial nerve – associated with complete aural atresia, microtia, first/second arch anomalies"),
  bullet("Partial aplasia / hypoplasia: Greatly reduced caliber nerve; presents as congenital facial paresis (partial, not complete palsy)"),
  bullet("Stenosis of fallopian canal: Narrow canal with hypoplastic nerve → intermittent episodic facial paresis (Shambaugh)"),
  bullet("Isolated facial nerve agenesis reported (Jervis & Bull, J Laryngol Otol 2001)"),
  spacer(),

  h3("5. Facial Nerve Anomalies in Congenital Aural Atresia (Most Clinically Important)"),

  ...codeBox([
    "FACIAL NERVE IN CONGENITAL AURAL ATRESIA",
    "",
    "  Congenital Aural Atresia",
    "          │",
    "          ├── MILD (Grade I): FN usually normal position",
    "          │",
    "          ├── MODERATE (Grade II): FN may be anteriorly displaced",
    "          │",
    "          └── SEVERE / COMPLEX (Grade III):",
    "                      │",
    "                      ├── Mastoid FN ROTATED LATERALLY (most common)",
    "                      ├── Ranging from minor obliquity → true horizontal course",
    "                      ├── Absence of vertical segment of FN canal",
    "                      ├── Bifid vertical segment",
    "                      └── FN crossing middle ear cavity (rare, catastrophic risk)",
  ]),

  spacer(),
  bullet("Pre-operative HRCT temporal bone is MANDATORY before any atresia repair surgery"),
  bullet("Intraoperative continuous FN EMG monitoring mandatory in ALL atresia cases"),
  bullet("Surgery deferred to age 5–6 to allow temporal bone maturation"),
  spacer(),

  h3("6. Chorda Tympani Anomalies"),
  bullet("Absence of the chorda tympani nerve"),
  bullet("Aberrant course: passes LATERAL to malleus instead of medial"),
  bullet("Late separation: chorda may not branch from main trunk until the level of the lateral SCC"),
  bullet("Extratemporal separation: chorda re-enters via its own separate bony canal"),
  bullet("Absence of chorda tympani should be distinguished from superior chorda: both are documented congenital variants"),
  spacer(),
  pageBreak(),

  // ── SECTION 8: CLINICAL TABLE ───────────────────────────────────────────────
  h1("PART VIII – CLINICAL CORRELATION TABLE"),

  makeTable(
    ["Anomaly", "Key Clinical Feature", "Investigation", "Management"],
    [
      ["Moebius Syndrome", "Bilateral FN + abducens palsy; mask face; feeding difficulty", "MRI (absent facial colliculi); EMG (absent potentials)", "Free muscle transfer; gold weight eyelid implant; speech therapy"],
      ["CHARGE Syndrome", "FN palsy + deafness + coloboma + choanal atresia", "HRCT/MRI temporal bone; CHD7 genetics", "Multidisciplinary; BAHA/cochlear implant"],
      ["Aural Atresia + FN anomaly", "Conductive HL; FN risk during surgery", "HRCT temporal bone (MANDATORY pre-op); Jahrsdoerfer score", "FN monitoring in all cases; atresia repair age 5–6"],
      ["Fallopian Canal Dehiscence", "Often asymptomatic; FN palsy in AOM; middle ear mass", "HRCT; intraoperative recognition", "FN monitoring; avoid instrument trauma; close follow-up in otitis media"],
      ["Tympanic FN inferior to oval window", "Risk during stapedectomy", "HRCT pre-stapedectomy", "Abandon procedure if recognised intra-op; seek senior help"],
      ["Bifid mastoid FN", "Risk of iatrogenic palsy in mastoid surgery", "HRCT; FN monitoring", "Careful complete identification; mandatory EMG monitoring"],
      ["CULLP (Asymmetric Crying Facies)", "Crying lower lip asymmetry only; normal rest of FN", "ECG + echocardiogram (cardiac defects 10%)", "Reassurance; cardiac evaluation; no FN surgery needed"],
      ["Melkersson-Rosenthal", "Recurrent palsy + lip/face oedema + fissured tongue", "Biopsy (granulomas); exclude Crohn's/sarcoid", "Steroids for acute attack; long-term doxycycline considered"],
    ]
  ),

  spacer(),
  pageBreak(),

  // ── SECTION 9: NEONATAL TABLE ───────────────────────────────────────────────
  h1("PART IX – NEONATAL FACIAL PALSY – DEVELOPMENTAL CAUSES"),
  body("(Based on Scott-Brown's Otorhinolaryngology Table 112.8)"),
  spacer(),

  makeTable(
    ["Syndrome / Condition", "Key Clinical Characteristics"],
    [
      ["Moebius Syndrome", "Agenesis of CN VI + VII nuclei. Bilateral facial palsy + abducens palsy + possible other CN involvement"],
      ["Dystrophia Myotonica", "Progressive familial distal myopathy. Bilateral facial palsy WITHOUT abducens palsy. Muscle + extramuscular wasting; 'swan-neck'"],
      ["Albers-Schönberg Disease (Osteopetrosis)", "Bony canal stenosis causing blindness, deafness and facial paralysis. Presents later in childhood (not usually at birth)"],
      ["Melkersson-Rosenthal Syndrome", "Recurrent facial palsy + facial oedema + fissured tongue"],
      ["CHARGE Association", "Colobomata, heart defects, choanal atresia, retarded growth, genital hypoplasia, ear abnormalities"],
      ["Oculo-auriculo-vertebral Syndrome (Goldenhar)", "Abnormal formation of first and second branchial arches; hemifacial microsomia"],
      ["Congenital Unilateral Lower Lip Palsy (CULLP)", "Hypoplasia of depressor anguli oris muscle. Cardiac defects in 10% of cases"],
    ]
  ),

  spacer(),
  ...infoBox([
    "📌 Distinguishing Congenital vs. Birth Trauma Facial Palsy (Neonatal)",
    "Birth trauma (forceps injury): EMG shows PRESENT potentials at birth → progressive amplitude decline.",
    "Congenital / developmental: EMG shows ABSENT potentials from birth.",
    "Prognosis of neonatal birth trauma palsy: >90% complete recovery.",
    "Any neonate with FN palsy should have brainstem response audiometry (cochlear nucleus abnormalities in some developmental disorders).",
  ], "E8F4FD", "2E74B5"),

  spacer(),
  pageBreak(),

  // ── SECTION 10: RECENT ADVANCES ─────────────────────────────────────────────
  h1("PART X – RECENT ADVANCES (2021–2026)"),

  h3("1. Aberrant FN in Congenital Hearing Loss (2024)"),
  body("Hammami B et al. (Indian J Otolaryngol Head Neck Surg, 2024; PMID: 39130285) documented that aberrant intratemporal facial nerve courses are significantly more common in children with congenital hearing loss. They recommend mandatory pre-operative HRCT evaluation before cochlear implantation in all congenital malformation cases."),
  spacer(),

  h3("2. Cochlear Implantation with Facial Nerve Deformity (2024)"),
  body("Zou X et al. (Lin Chuang Er Bi Yan Hou, 2024; PMID: 38686480) documented cochlear implantation via retro-facial approach in congenital microtia with severe facial nerve deformity. This surgical technique is now an option when the standard approach is precluded by aberrant FN anatomy."),
  spacer(),

  h3("3. CHARGE Syndrome Otopathology (2022)"),
  body("da Costa Monsanto R et al. (Otolaryngol Head Neck Surg, 2022; PMID: 33874787) performed comprehensive temporal bone histopathology in CHARGE syndrome, confirming absent semicircular canals, cochlear hypoplasia, and agenesis of the intratemporal facial nerve canal as consistent findings, supporting aggressive hearing rehabilitation with BAHA or cochlear implant."),
  spacer(),

  h3("4. Facial Nerve Imaging Advances (2023)"),
  body("Ottaiano AC et al. (Semin Ultrasound CT MR, 2023; PMID: 37055142) reviewed complete imaging anatomy of the facial nerve. Key findings: (a) congenital abnormalities are best assessed by HRCT for canal anomalies; (b) gadolinium MRI is complementary for nerve pathology; (c) the five intratemporal segments must be systematically evaluated. HRCT remains the gold standard for pre-surgical mapping of the fallopian canal."),
  spacer(),

  h3("5. Intraoperative Neuromonitoring (IONM) – Current Standard"),
  body("Continuous EMG-based facial nerve monitoring (orbicularis oculi + orbicularis oris) is now the standard of care in all parotid, mastoid, and cochlear implant surgeries – particularly critical in patients with known congenital anomalies or craniofacial syndromes (Scott-Brown Best Clinical Practice). FN monitoring does not replace anatomical knowledge but shortens the surgical learning curve and reduces iatrogenic injury."),
  spacer(),

  h3("6. Genetics of Moebius Syndrome"),
  body("Mouse models of rhombomere 4 vascular disruption reproduce the Moebius phenotype, supporting the vascular disruption hypothesis. Chromosomal loci identified: MBS1 (13q12.2) and MBS2 (3q21-22). PLCL1 and REV3L gene mutations have been identified in some familial cases."),
  spacer(),
  pageBreak(),

  // ── SECTION 11: EXAM SUMMARY ─────────────────────────────────────────────────
  h1("PART XI – QUICK REVISION SUMMARY (RGUHS EXAM)"),

  h2("Key Numbers to Remember"),
  makeTable(
    ["Parameter", "Value", "Note"],
    [
      ["Intracranial segment", "24 mm", "Traverses CPA"],
      ["Labyrinthine segment", "4 mm", "SHORTEST; no epineurium; NARROWEST"],
      ["Tympanic segment", "~13 mm", "Most dehiscences here; above oval window"],
      ["Mastoid segment", "~20 mm", "LONGEST intratemporal; most variable"],
      ["Fallopian canal dehiscence above OW", "55–66% of dehiscences", "Bilateral in 75%"],
      ["Geniculate ganglion bone dehiscence", "~25% of ears", "Vulnerability in temporal bone fractures"],
      ["Stylomastoid foramen surface in neonates", "Superficial", "Risk in neonatal parotid/post-auricular surgery"],
      ["Neonatal FN trauma recovery", ">90% complete", "Good prognosis with conservative management"],
    ]
  ),

  spacer(),
  h2("High-Yield Facts"),
  bullet("Facial nerve: Only CN to traverse a complete bony canal within a bone", 0, true),
  bullet("UMN palsy: Forehead SPARED (bilateral cortical supply to superior FN nucleus)", 0, true),
  bullet("Most common site of dehiscence: Tympanic segment ABOVE oval window", 0, true),
  bullet("Most common congenital anomaly in practice: Lateral rotation of mastoid FN in aural atresia", 0, true),
  bullet("Moebius: CN VI + VII nuclear agenesis; bilateral; EMG absent from birth", 0, true),
  bullet("CULLP: NOT true FN palsy; depressor anguli oris hypoplasia; check heart in 10%", 0, true),
  bullet("FN in IAC: \"Seven up, Coke down\" (VII anterosuperior; cochlear anteroinferior)", 0, true),
  bullet("Topographic diagnosis: Proximal → GSPN (lacrimation) → stapedius → chorda tympani → purely motor", 0, true),
  bullet("All congenital craniofacial/atresia cases: MANDATORY intraoperative FN monitoring", 0, true),
  bullet("Pre-stapedectomy HRCT: Must rule out tympanic FN inferior to oval window", 0, true),
  spacer(),

  // ── REFERENCES ───────────────────────────────────────────────────────────────
  pageBreak(),
  h1("REFERENCES"),
  body("1. Cummings CW et al. Cummings Otolaryngology Head and Neck Surgery, 7th Ed. Elsevier. Chapter 126 (Facial Nerve – Anatomy, Injury, Repair); Chapter 135 (Imaging of the Temporal Bone)."),
  body("2. Scott-Brown's Otorhinolaryngology Head & Neck Surgery, 8th Ed. (Gleeson M et al.). CRC Press. Volume 2 – Chapters on Facial Nerve Anatomy, Pediatric Facial Palsy, and Skull Base."),
  body("3. Shambaugh GE, Glasscock ME. Surgery of the Ear, 6th Ed. Chapter 2 (Anatomy of the Facial Nerve) and Chapter 13 (Anomalies of the Facial Canal)."),
  body("4. Gray's Anatomy for Students, 4th Ed. Elsevier. Chapter on Head and Neck – Facial Nerve."),
  body("5. Bailey & Love's Short Practice of Surgery, 28th Ed. CRC Press."),
  body("6. Dhingra PL, Dhingra S. Diseases of Ear, Nose and Throat & Head and Neck Surgery, 8th Ed. Elsevier India."),
  body("7. Hazarika P. Textbook of ENT & Head-Neck Surgery: Clinical & Practical. CBS Publishers."),
  body("8. Ottaiano AC, Gomez GD, Freddi TAL. The Facial Nerve: Anatomy and Pathology. Semin Ultrasound CT MR. 2023 Apr. [PMID: 37055142]"),
  body("9. Hammami B, Kharrat I, Ayed MB. Aberrant Course of the Intratemporal Facial Nerve in Children with Congenital Hearing Loss. Indian J Otolaryngol Head Neck Surg. 2024 Aug. [PMID: 39130285]"),
  body("10. da Costa Monsanto R, Knoll RM, de Oliveira Penido N. Otopathologic Abnormalities in CHARGE Syndrome. Otolaryngol Head Neck Surg. 2022 Feb. [PMID: 33874787]"),
  body("11. Zou X, Xue S, Wei X. Cochlear implantation through retro-facial approach with congenital microtia malformation with facial nerve deformity: a case report. Lin Chuang Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 2024 May. [PMID: 38686480]"),

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          children:[new TextRun({ text:"50-Mark Answer  |  RGUHS University Standard", font:FONT, size:26, bold:true, color:C.white })],
          alignment:AlignmentType.CENTER,
        }),
        new Paragraph({
          children:[new TextRun({ text:"ENT & Head-Neck Surgery  –  Postgraduate Study Guide", font:FONT, size:22, italics:true, color:C.ltblue })],
          alignment:AlignmentType.CENTER, ...sp(60,0),
        }),
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      shading:{ type:ShadingType.SOLID, color:C.navy, fill:C.navy },
      margins:{ top:180, bottom:180, left:400, right:400 },
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    width:{ size:100, type:WidthType.PERCENTAGE },
    borders:noBorders,
    ...sp(200,300),
  }),
  new Paragraph({
    children:[new TextRun({ text:"Sources:", font:FONT, size:22, bold:true, color:C.navy })],
    alignment:AlignmentType.CENTER, ...sp(0,40),
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  new Paragraph({
    children:[new TextRun({ text:"Cummings Otolaryngology  ·  Scott-Brown's (Vol 1 & 2)  ·  Shambaugh Surgery of the Ear", font:FONT, size:21, italics:true, color:"444444" })],
    alignment:AlignmentType.CENTER, ...sp(0,40),
  }),
  new Paragraph({
    children:[new TextRun({ text:"Stell & Maran's Head & Neck Surgery  ·  Dhingra ENT  ·  Hazarika ENT  ·  Zakir Hussain ENT", font:FONT, size:21, italics:true, color:"444444" })],
    alignment:AlignmentType.CENTER, ...sp(0,40),
  }),
  new Paragraph({
    children:[new TextRun({ text:"PubMed Recent Literature (2021–2026)", font:FONT, size:21, italics:true, color:"444444" })],
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  pbr(),
);

// ════════════════════ PART I: INTRODUCTION ═══════════════════════════════════
add(
  h1("PART I — INTRODUCTION"),
  body("The facial nerve (CN VII) is the nerve of the second branchial arch (Reichert's cartilage). It is the most complex cranial nerve, carrying five distinct fiber types, and it traverses the longest intrabony canal of any cranial nerve — the fallopian canal (facial canal). Its intimate anatomical relationship with the temporal bone, parotid gland, middle ear, and skull base makes its detailed knowledge indispensable for every otolaryngologist and head & neck surgeon."),
  gap(),
  infoBox("⚡ CORE CONCEPT",
    [
      "Facial nerve = nerve of the 2nd branchial arch (Reichert's cartilage).",
      "Carries 5 fiber types through 6 anatomical segments.",
      "Only cranial nerve that traverses a complete bony canal entirely within a single bone.",
      "Labyrinthine segment = SHORTEST (4 mm) and NARROWEST portion of the fallopian canal.",
    ], C.ltblue, C.blue),
  gap(),

// ════════════════════ PART II: NUCLEI ════════════════════════════════════════
  h1("PART II — NUCLEI AND FIBER COMPOSITION"),
  h2("A.  Three Brainstem Nuclei"),
  tbl(
    ["Nucleus","Location","Fiber Type","Function"],
    [
      ["Motor nucleus (VII)","Caudal pons","SVE – Special Visceral Efferent","Facial expression, stapedius, stylohyoid, post. belly digastric"],
      ["Superior salivatory nucleus","Dorsal to motor nucleus, pons","GVE – General Visceral Efferent","Preganglionic parasympathetics → lacrimal, nasal, submandibular, sublingual glands"],
      ["Nucleus of solitary tract (NTS)","Medulla oblongata","SVA + GVA","Taste (anterior 2/3 tongue, soft palate); visceral sensation (nose, pharynx, palate)"],
    ], C.navy, { colWidths:[22,20,22,36] }
  ),
  gap(),
  infoBox("📌 UMN vs. LMN Palsy — Why forehead is spared in UMN lesions",
    [
      "Superior facial motor nucleus (frontalis, orbicularis oculi) receives BILATERAL cortical input.",
      "Inferior nucleus (lower face) receives ONLY ipsilateral input.",
      "UMN (supranuclear) lesion → forehead SPARED   |   LMN lesion → entire face AFFECTED.",
    ], C.ltyell, C.amber),
  gap(),
  h2("B.  Five Fiber Types"),
  tbl(
    ["Fiber Type","Abbrev.","Function","Pathway"],
    [
      ["Special Visceral Efferent","SVE","Motor to muscles of facial expression","Main trunk CN VII"],
      ["General Visceral Efferent","GVE","Secretomotor (parasympathetic)","GSPN → lacrimal; Chorda tympani → submandibular/sublingual"],
      ["Special Visceral Afferent","SVA","Taste","Ant. 2/3 tongue via chorda tympani; palate/tonsil via GSPN"],
      ["General Somatic Afferent","GSA","Touch, proprioception","EAC, concha, facial muscles"],
      ["General Visceral Afferent","GVA","Visceral sensation","Mucosa of nose, pharynx, palate"],
    ], C.teal),
  gap(),
  pbr(),

// ════════════════════ PART III: SEGMENTS ══════════════════════════════════════
  h1("PART III — COURSE AND SEGMENTS"),
  body([bld("Mnemonic: "), reg('"I Can Learn To Master Surgery" = Intracranial · Canalicular · Labyrinthine · Tympanic · Mastoid · Stylomastoid (extratemporal)')]),
  gap(),

  // Master flowchart
  divider("COMPLETE COURSE OF THE FACIAL NERVE — FLOWCHART"),
  flowBox([
    "  MOTOR CORTEX  (precentral gyrus)",
    "        │  Corticobulbar fibres",
    "        │  (bilateral → upper face;  ipsilateral → lower face)",
    "        ▼",
    "  ┌─────────────────────────────────────────────────────────────────┐",
    "  │  BRAINSTEM NUCLEI  (Motor, SSN, NTS)  — Caudal pons + Medulla  │",
    "  └─────────────────────────────────────────────────────────────────┘",
    "        │",
    "  ══════╪═══════════════════════════════════════════════════════════",
    "   [1]  │  INTRACRANIAL (CISTERNAL) SEGMENT       Length: 24 mm",
    "        │  Pons → Porus of IAC  |  Traverses CPA",
    "        │  Nervus intermedius joins here",
    "  ══════╪═══════════════════════════════════════════════════════════",
    "        │",
    "   [2]  │  INTRACANALICULAR (MEATAL) SEGMENT      Length: ~8 mm",
    "        │  Porus → Fundus of IAC",
    "        │  Position: ANTEROSUPERIOR quadrant",
    "        │  Mnemonic: 'Seven UP,  Coke DOWN'",
    "        │  Landmark: Bill's Bar (vertical crest) separates VII from",
    "        │            superior vestibular nerve at fundus",
    "  ══════╪═══════════════════════════════════════════════════════════",
    "        │",
    "   [3]  │  LABYRINTHINE SEGMENT  ← SHORTEST (4 mm) & NARROWEST",
    "        │  Fundus IAC → Geniculate Ganglion",
    "        │  Passes between cochlea and vestibule",
    "        │  No epineurium; watershed blood supply zone",
    "        │  ➤ 1st GENU  (acute posterior turn ~120°)",
    "        │  ➤ GSPN exits at geniculate ganglion",
    "  ══════╪═══════════════════════════════════════════════════════════",
    "        │",
    "   [4]  │  TYMPANIC (HORIZONTAL) SEGMENT          Length: ~13 mm",
    "        │  Geniculate ganglion → 2nd genu",
    "        │  Medial wall of middle ear",
    "        │  Passes over: Cochleariform process → Oval window niche",
    "        │  Most common site of fallopian canal dehiscence",
    "  ══════╪═══════════════════════════════════════════════════════════",
    "        │",
    "   [5]  │  MASTOID (VERTICAL) SEGMENT  ← LONGEST  Length: ~20 mm",
    "        │  2nd genu → Stylomastoid foramen",
    "        │  Behind EAC; anterior to sigmoid sinus",
    "        │  ➤ Nerve to stapedius (near pyramidal eminence)",
    "        │  ➤ Chorda tympani (4–6 mm above stylomastoid foramen)",
    "        │  ➤ Facial recess (posterior tympanotomy space)",
    "  ══════╪═══════════════════════════════════════════════════════════",
    "        │",
    "  STYLOMASTOID FORAMEN  (exit from temporal bone)",
    "        │",
    "   [6]  │  EXTRATEMPORAL SEGMENT",
    "        ├── Posterior auricular nerve (occipitalis, post. auricular m.)",
    "        ├── Branch to digastric (post. belly) + stylohyoid",
    "        └── Enters PAROTID GLAND",
    "                    │",
    "          ┌─────────┴──────────────┐",
    "    TEMPOROFACIAL div.       CERVICOFACIAL div.",
    "          │                         │",
    "    Temporal  Zygomatic       Buccal  Marginal  Cervical",
    "    branch    branch          branch  Mandibular branch",
    "                                      branch",
    "  ─────────────────────────────────────────────────────────────────",
    "  Mnemonic for 5 branches:  'Two Zebras Bit My Cat'",
    "  T=Temporal  Z=Zygomatic  B=Buccal  M=Marginal mandibular  C=Cervical",
  ]),
  gap(),

  h2("Segment Summary Table  (Cummings / Shambaugh)"),
  tbl(
    ["Segment","Length","Key Feature","Fallopian Canal / Landmark","Main Branch"],
    [
      ["1. Intracranial (Cisternal)","24 mm","Traverses CPA; nervus intermedius joins","Porus of IAC","—"],
      ["2. Meatal (Intracanalicular)","~8 mm","Anterosuperior quadrant IAC","Bill's bar (vertical crest)","—"],
      ["3. Labyrinthine","4 mm (SHORTEST)","Narrowest; no epineurium; watershed zone","Meatal foramen; geniculate fossa","GSPN; 1st genu"],
      ["4. Tympanic (Horizontal)","~13 mm","Medial wall middle ear; most dehiscences here","Cochleariform process; oval window","2nd genu"],
      ["5. Mastoid (Vertical)","~20 mm (LONGEST)","Most variable path; behind EAC","Pyramidal eminence; lateral SCC","Nerve to stapedius; Chorda tympani"],
      ["6. Extratemporal","Variable","Enters parotid; 5 terminal branches","Digastric aponeurosis","Post. auricular N.; 5 branches"],
    ], C.navy, { colWidths:[22,12,25,25,16] }
  ),
  gap(),

  h2("Surgical Landmarks by Segment  (Cummings Table 126.1)"),
  tbl(
    ["Segment","Primary Surgical Landmark(s)"],
    [
      ["Labyrinthine segment","Vertical crest — Bill's Bar"],
      ["Geniculate ganglion","Retrograde dissection of GSPN (middle fossa approach)"],
      ["Tympanic segment (anterior)","Cochleariform process (transmastoid)"],
      ["Tympanic segment (posterior)","Oval window niche"],
      ["Second genu","Oval window"],
      ["Mastoid segment","Pyramidal eminence · lateral SCC · short process of incus · chorda tympani"],
      ["Stylomastoid foramen","Cephalic edge and aponeurosis of posterior belly of digastric"],
    ], C.teal, { firstColHeader:true }
  ),
  gap(),

  h2("Detailed Segment Notes"),

  h3("Labyrinthine Segment — Most Vulnerable"),
  bull("Shortest (4 mm) and narrowest (meatal foramen ~0.7 mm) — edema → compression easily"),
  bull("No fibrous sheath / epineurium: no barrier to injury, no vascular plexus"),
  bull("Watershed zone: AICA (vertebrobasilar) vs. petrosal branch of middle meningeal + stylomastoid artery (ECA)"),
  bull("Geniculate ganglion: overlying bone is thin and dehiscent in ~25% of ears"),
  bull("1st genu: acute posterior turn (120°) — tethered by GSPN anteriorly"),
  bull("Significance: explains why Bell's palsy maximally affects this segment (ischaemic + compressive)"),
  gap(),

  h3("Tympanic (Horizontal) Segment"),
  bull("Dehiscence above oval window in 55–66% of all dehiscences (bilateral in ~75% — Shambaugh)"),
  bull("Prolapsed nerve may present as a middle ear mass mimicking a glomus tumour"),
  bull("Key relationships: cochleariform process anteriorly; oval window niche posteriorly"),
  bull("2nd genu forms at pyramidal eminence just inferior to lateral SCC"),
  gap(),

  h3("Mastoid (Vertical) Segment"),
  bull("Most variable pathway — especially in congenital malformations (atresia, syndromes)"),
  bull("Facial recess: lateral to FN, medial to chorda tympani, below incudal fossa → used in posterior tympanotomy"),
  bull("Chorda tympani separates 4–6 mm above stylomastoid foramen; ascends in own canal (lateral + anterior)"),
  bull("Chorda crosses middle ear: medial to malleus neck, lateral to long process of incus"),
  gap(),

  h3("Extratemporal Course"),
  bull("Stylomastoid foramen is SUPERFICIALLY positioned in neonates/infants (incomplete mastoid development)"),
  bull("Risk of facial nerve injury in post-auricular incisions and parotid surgery in neonates"),
  bull("Within parotid: divides into temporofacial and cervicofacial divisions"),
  bull("Five terminal branches — 'Two Zebras Bit My Cat': Temporal, Zygomatic, Buccal, Marginal Mandibular, Cervical"),
  gap(),
  pbr(),

// ════════════════════ PART IV: BRANCHES ═══════════════════════════════════════
  h1("PART IV — INTRATEMPORAL BRANCHES"),
  tbl(
    ["Branch","Origin","Course","Function"],
    [
      ["Greater Superficial Petrosal Nerve (GSPN)","Geniculate ganglion (anterior surface)","MCF floor groove → foramen lacerum → vidian nerve → pterygopalatine ganglion","Secretomotor: lacrimal gland, nasal/palatine seromucinous glands; taste from soft palate"],
      ["Nerve to Stapedius","Mastoid segment near pyramidal eminence","Tiny canaliculus → stapedius muscle","Motor: stapedius (acoustic/stapedial reflex) — absence causes hyperacusis"],
      ["Chorda Tympani","Mastoid segment ~4–6 mm above stylomastoid foramen","Ascends → iter chordae posterius → crosses medial to malleus, lateral to incus → iter chordae anterius (canal of Huguier) → petrotympanic fissure → joins lingual nerve","SVA: taste anterior 2/3 tongue; GVE: secretomotor to submandibular + sublingual glands"],
    ], C.navy, { colWidths:[22,20,33,25] }
  ),
  gap(),
  pbr(),

// ════════════════════ PART V: BLOOD SUPPLY ════════════════════════════════════
  h1("PART V — BLOOD SUPPLY"),
  tbl(
    ["Segment","Arterial Supply","System"],
    [
      ["Intracranial + Labyrinthine (meatal)","Labyrinthine artery (branch of AICA)","Vertebrobasilar"],
      ["Geniculate ganglion + Tympanic segment","Petrosal branch of middle meningeal artery","External carotid (via middle meningeal)"],
      ["Mastoid segment + Stylomastoid foramen","Stylomastoid artery (branch of posterior auricular artery)","External carotid"],
    ], C.green
  ),
  gap(),
  infoBox("⚡ WATERSHED ZONE — Clinical Significance",
    [
      "Labyrinthine segment = junction of vertebrobasilar and ECA supply.",
      "Also lacks epineurium → NO vascular plexus collateral.",
      "This combination explains the maximum vulnerability of this segment in Bell's palsy,",
      "temporal bone fractures, and viral neuritis — leading to ischaemia + compression injury.",
    ], C.ltred, C.red),
  gap(),
  pbr(),

// ════════════════════ PART VI: TOPOGRAPHIC DIAGNOSIS ═════════════════════════
  h1("PART VI — TOPOGRAPHIC DIAGNOSIS"),
  divider("TOPOGRAPHIC DIAGNOSIS FLOWCHART  (Dhingra / Hazarika)"),
  flowBox([
    "  FACIAL PALSY — DETERMINE LEVEL OF LESION",
    "",
    "  Step 1: Is LACRIMATION impaired?  (Schirmer's test)",
    "           │",
    "           ├── YES ──▶  Lesion at or PROXIMAL to GSPN",
    "           │            (Geniculate ganglion, labyrinthine, meatal, CPA, or brainstem)",
    "           │",
    "           └── NO  ──▶  Go to Step 2",
    "",
    "  Step 2: Is STAPEDIAL REFLEX absent?  (Impedance audiometry)",
    "           │",
    "           ├── YES ──▶  Lesion between GSPN and nerve to stapedius",
    "           │            (Tympanic / proximal mastoid segment)",
    "           │",
    "           └── NO  ──▶  Go to Step 3",
    "",
    "  Step 3: Is TASTE impaired?  (Chorda tympani — electrogustometry)",
    "           │",
    "           ├── YES ──▶  Lesion between nerve to stapedius and chorda tympani",
    "           │            (Mastoid segment, distal to pyramidal eminence)",
    "           │",
    "           └── NO  ──▶  Purely MOTOR palsy",
    "                        Lesion at or distal to stylomastoid foramen",
    "                        (Parotid / extratemporal / traumatic)",
  ]),
  gap(),
  tbl(
    ["Level of Lesion","Lacrimation","Stapedial Reflex","Taste","Common Cause"],
    [
      ["CPA / IAC / Labyrinthine","Impaired","Absent","Impaired","Vestibular schwannoma; Bell's palsy; herpes zoster oticus"],
      ["Tympanic segment","Normal","Absent","Impaired","Otitis media; cholesteatoma; trauma"],
      ["Mastoid segment","Normal","Normal","Impaired","Mastoiditis; cholesteatoma; fracture"],
      ["Stylomastoid / extratemporal","Normal","Normal","Normal","Parotid tumour; forceps injury; Bell's palsy (distal)"],
    ], C.teal
  ),
  gap(),
  pbr(),

// ════════════════════ PART VII: CONGENITAL ANOMALIES ═════════════════════════
  h1("PART VII — CONGENITAL ANOMALIES OF THE FACIAL NERVE"),

  // Classification flowchart
  divider("CLASSIFICATION — FLOWCHART"),
  flowBox([
    "  CONGENITAL ANOMALIES OF FACIAL NERVE",
    "                     │",
    "        ┌────────────┴─────────────────────────────────────┐",
    "        │                                                    │",
    "  NUCLEAR / CENTRAL                           PERIPHERAL / INTRATEMPORAL",
    "  (Brainstem origin)                          (Canal & nerve anomalies)",
    "        │                                                    │",
    "   ┌────┴─────────────────────┐          ┌──────────────────┴───────────────┐",
    "   │                          │          │                                  │",
    "  Moebius syndrome         CHARGE      COURSE / POSITION          CANAL / NERVE",
    "  Dystrophia myotonica     OAV Synd.        │                          │",
    "  Poland syndrome          MRS          ┌───┴────────┐          ┌─────┴──────────┐",
    "  CULLP                                 │            │          │                │",
    "                                  Aberrant    Bifurcation  Dehiscence       Aplasia /",
    "                                  course      /Duplication  (Fallopian      Agenesis",
    "                                  patterns                   canal)",
  ]),
  gap(),

  // ── NUCLEAR ANOMALIES ───────────────────────────────────────────────────────
  h2("A.  Nuclear / Central Anomalies"),

  h3("1.  Moebius Syndrome (Moebius Sequence)"),
  banner("DEFINITION: Agenesis / hypoplasia of CN VI (abducens) + CN VII (facial) motor nuclei in the pons", C.navy),
  gap(80),
  tbl(
    ["Feature","Details"],
    [
      ["Cranial nerves affected","CN VI + VII (bilateral, rarely unilateral); CN III, V, IX, X, XII in some cases"],
      ["Facial features","Mask-like face; cannot smile, frown, whistle, or close eyes; drooling"],
      ["Ocular","Bilateral horizontal gaze palsy (abducens) — distinguishing feature"],
      ["Speech / feeding","Dysarthria, dysphagia, feeding difficulty in neonates"],
      ["Associated limb defects","Poland sequence (chest/upper limb); talipes equinovarus (club foot)"],
      ["Pathogenesis","Rhombomere 4 vascular disruption during fetal development (subclavian artery disruption theory)"],
      ["Genetics","MBS1 (13q12.2); MBS2 (3q21-q22); PLCL1; REV3L gene mutations in familial cases"],
      ["Investigation","MRI: absent/hypoplastic facial colliculi on floor of 4th ventricle; EMG: ABSENT potentials at birth"],
      ["Management","Free muscle transfer (gracilis/pectoralis minor) for smile; gold weight eyelid implant; speech therapy"],
    ], C.blue, { firstColHeader:true, colWidths:[25,75] }
  ),
  gap(),
  infoBox("📌 Key Distinction from Birth Trauma Palsy",
    [
      "Birth trauma → EMG shows PRESENT potentials at birth with progressive amplitude decline.",
      "Moebius / congenital → EMG shows ABSENT potentials from birth (no nucleus).",
      "All neonates with facial palsy should have brainstem response audiometry (ABR).",
    ], C.ltyell, C.amber),
  gap(),

  h3("2.  CHARGE Syndrome"),
  body([bld("Acronym: "), reg("C=Coloboma · H=Heart defects · A=choanal Atresia · R=Retarded growth · G=Genital hypoplasia · E=Ear anomalies")]),
  bull("Facial nerve palsy: due to aplasia of fallopian canal and facial nerve agenesis"),
  bull("Temporal bone: absent semicircular canals, cochlear hypoplasia (Mondini-type)"),
  bull("Genetics: CHD7 gene mutation (8q12.2) — autosomal dominant"),
  bull("Management: multidisciplinary; BAHA or cochlear implant; cardiac surgery; ophthalmology"),
  gap(),

  h3("3.  Dystrophia Myotonica (Steinert's Disease)"),
  bull("Progressive autosomal dominant myopathy — CTG repeat expansion, chromosome 19q13"),
  bull("Bilateral facial palsy WITHOUT abducens palsy — distinguishes from Moebius"),
  bull("Wasting: facial, SCM, masticatory muscles → characteristic 'hatchet face' / 'swan-neck'"),
  bull("Other features: myotonia, cataracts, cardiac conduction defects, diabetes, intellectual disability"),
  gap(),

  h3("4.  Congenital Unilateral Lower Lip Palsy (CULLP) / Asymmetric Crying Facies"),
  infoBox("⚡ IMPORTANT — NOT a true facial nerve palsy!",
    [
      "Cause: Hypoplasia or ABSENCE of the depressor anguli oris muscle (not nerve damage).",
      "Presentation: Lower lip asymmetry ONLY during crying — the lower lip on the affected side",
      "  does NOT depress. Rest of facial nerve function is completely NORMAL.",
      "Cardiac defects in ~10% of cases → mandatory echocardiogram + ECG in ALL cases.",
      "Prognosis: Excellent — resolves spontaneously or is cosmetically acceptable long-term.",
    ], C.ltred, C.red),
  gap(),

  h3("5.  Oculo-Auriculo-Vertebral (OAV) Spectrum / Goldenhar Syndrome"),
  bull("Abnormal formation of BOTH first and second branchial arches"),
  bull("Hemifacial microsomia: asymmetric underdevelopment of one side of face"),
  bull("Facial nerve hypoplasia and/or aberrant course of mastoid segment"),
  bull("Associated: microtia, aural atresia, preauricular tags, vertebral anomalies, epibulbar dermoids"),
  bull("Unilateral conductive hearing loss common; management: bone-anchored hearing aid (BAHA) / atresia repair"),
  gap(),

  h3("6.  Melkersson-Rosenthal Syndrome"),
  bull("Classic triad: (i) Recurrent facial palsy + (ii) Oro-facial oedema + (iii) Fissured (scrotal) tongue"),
  bull("Typically presents in childhood/adolescence; relapses and remissions"),
  bull("Biopsy: non-caseating granulomatous inflammation (identical to sarcoid/Crohn's histology)"),
  bull("Management: corticosteroids for acute attacks; long-term doxycycline or hydroxychloroquine; cheiloplasty for persistent labial swelling"),
  gap(),

  h3("7.  Poland Syndrome"),
  bull("Ipsilateral absence of pectoralis major + upper limb defects"),
  bull("Facial nerve nucleus may be hypoplastic → ipsilateral facial weakness (rare association)"),
  bull("Pathogenesis: subclavian artery disruption (similar to Moebius)"),
  gap(),
  pbr(),

  // ── PERIPHERAL ANOMALIES ────────────────────────────────────────────────────
  h2("B.  Peripheral / Intratemporal Anomalies"),

  h3("1.  Fallopian Canal Dehiscence  —  Most Common Congenital Anomaly"),
  divider("SITES OF DEHISCENCE (by frequency)"),
  flowBox([
    "  FALLOPIAN CANAL DEHISCENCE",
    "",
    "  Rank   Site                                   Frequency",
    "  ────   ────────────────────────────────────   ─────────",
    "  1st    Tympanic segment ABOVE oval window     55–66%",
    "         (Bilateral in ~75% of cases — Shambaugh)",
    "  2nd    Distal tympanic segment / 2nd genu     ~20%",
    "  3rd    Geniculate ganglion (thin/absent bone) ~25% of ears overall (Cummings)",
    "  4th    Mastoid segment                        Uncommon",
    "",
    "  Clinical Consequences:",
    "  ● Exposes nerve to toxins / infection in otitis media → FN palsy in AOM / CSOM",
    "  ● Prolapsed nerve → MIDDLE EAR MASS (mimics glomus tumour or cholesteatoma)",
    "  ● Surgical hazard: inadvertent drill/instrument trauma during mastoidectomy",
    "  ● GSPN traction at geniculate → intraoperative facial palsy (middle fossa surgery)",
  ]),
  gap(),

  h3("2.  Aberrant Course of the Facial Nerve"),
  tbl(
    ["Anomaly","Description","Clinical Significance"],
    [
      ["Inferior displacement of tympanic segment (MOST IMPORTANT)","Tympanic FN descends ANTERIOR and INFERIOR to oval window; may overlie / cover the stapes footplate entirely","Highest surgical risk during stapedectomy — procedure may be impossible; HRCT mandatory before stapes surgery"],
      ["Anteroinferior course over promontory","Nerve crosses the promontory, may overlie round window niche","Risk during myringotomy and round window membrane procedures"],
      ["Mastoid segment posterior bulge","Nerve bulges more posterolaterally than normal inferior to lateral SCC","Risk during cortical mastoidectomy; easy to drill into nerve"],
      ["Lateral rotation in aural atresia","Mastoid segment rotated laterally — minor obliquity to true horizontal course","Most dangerous variant in atresia surgery; HRCT pre-op MANDATORY; FN monitoring mandatory"],
      ["Superficial stylomastoid foramen (neonates)","Nerve exits skull base superficially (immature mastoid = no mastoid tip yet)","High risk of FN injury in post-auricular incision and parotid surgery in neonates"],
    ], C.navy, { colWidths:[22,43,35] }
  ),
  gap(),

  h3("3.  Bifurcation / Duplication of the Facial Nerve"),
  bull("Rare but documented: vertical (mastoid) segment may be BIPARTITE or even TRIPARTITE — Shambaugh"),
  bull("Glastonbury et al.: congenital bifurcation of the intratemporal facial nerve (referenced in Scott-Brown)"),
  bull("Most common form: the nerve divides into two trunks in the tympanic or mastoid segment"),
  bull("One trunk may take an aberrant course; both are functional"),
  bull("SURGICAL HAZARD: Surgeon identifies one division, sections the other believing it to be a vessel or band"),
  bull("Mandatory: FN monitoring + careful complete identification of both trunks before drilling proceeds"),
  gap(),

  h3("4.  Agenesis / Aplasia / Hypoplasia of the Facial Nerve"),
  bull("Complete agenesis: total absence of facial nerve — associated with complete aural atresia, microtia, and severe first/second arch anomalies"),
  bull("Partial aplasia / hypoplasia: reduced calibre nerve → congenital facial paresis (not complete palsy)"),
  bull("Canal stenosis: narrow fallopian canal with hypoplastic nerve → INTERMITTENT EPISODIC facial paresis — Shambaugh"),
  bull("Isolated facial nerve agenesis has been reported (Jervis & Bull, J Laryngol Otol 2001; cited in Scott-Brown)"),
  gap(),

  h3("5.  Facial Nerve Anomalies in Congenital Aural Atresia  —  Most Clinically Important"),
  divider("FACIAL NERVE IN CONGENITAL AURAL ATRESIA — FLOWCHART"),
  flowBox([
    "  CONGENITAL AURAL ATRESIA  (Jahrsdoerfer Classification context)",
    "",
    "  Grade I (Mild)",
    "   └── FN usually in normal position; minor anomalies only",
    "",
    "  Grade II (Moderate)",
    "   └── FN may be anteriorly displaced; monitor carefully",
    "",
    "  Grade III (Severe / Complex)  — HIGHEST RISK",
    "   ├── Mastoid FN rotated LATERALLY (most common anomaly in atresia)",
    "   │       Range: minor obliquity → true horizontal course",
    "   ├── Vertical segment of FN canal absent",
    "   ├── Bifid vertical segment (bipartite)",
    "   ├── FN crossing middle ear cavity (rare; catastrophic iatrogenic risk)",
    "   └── Stylomastoid foramen in abnormal / anterior position",
    "",
    "  Pre-op Protocol:",
    "  ✔ HRCT temporal bone (MANDATORY before ANY atresia surgery)",
    "  ✔ Jahrsdoerfer scoring — score ≥7 acceptable for surgical repair",
    "  ✔ Intraoperative continuous FN EMG monitoring (mandatory)",
    "  ✔ Surgery deferred to age 5–6 years (temporal bone maturation)",
  ]),
  gap(),

  h3("6.  Chorda Tympani Anomalies"),
  bull("Absence of the chorda tympani nerve (congenital ageusia for anterior tongue)"),
  bull("Aberrant course: passes LATERAL to malleus instead of medial (surgical trap during ossiculoplasty)"),
  bull("Late separation: chorda does not branch from main trunk until level of lateral SCC (instead of usual 4–6 mm above stylomastoid foramen)"),
  bull("Extratemporal separation: chorda separates outside temporal bone, re-enters via own separate bony canal"),
  bull("Double chorda: two separate chorda tympani nerves described in rare case reports"),
  gap(),
  pbr(),

// ════════════════════ PART VIII: CLINICAL TABLE ═══════════════════════════════
  h1("PART VIII — CLINICAL CORRELATION TABLE"),
  tbl(
    ["Anomaly","Key Clinical Feature","Key Investigation","Management Priority"],
    [
      ["Moebius Syndrome","Bilateral FN + abducens palsy; mask face; drooling","MRI brain (absent facial colliculi); EMG (absent potentials)","Free muscle transfer; gold weight; speech therapy"],
      ["CHARGE Syndrome","FN palsy + deafness + coloboma + choanal atresia","HRCT/MRI temporal bone; CHD7 gene test","Multidisciplinary; BAHA/CI for hearing"],
      ["Aural Atresia + FN anomaly","Conductive HL; high iatrogenic FN risk","HRCT temporal bone (MANDATORY); Jahrsdoerfer score","FN monitoring all cases; defer surgery to age 5–6"],
      ["Fallopian Canal Dehiscence","Often silent; FN palsy in otitis media; middle ear mass","HRCT; intraoperative recognition","FN monitoring; avoid trauma; urgent treat AOM/CSOM"],
      ["Tympanic FN below oval window","Obstructed view of stapes; risk in stapedectomy","HRCT before ALL stapes surgery","Abandon stapedectomy; senior surgeon input"],
      ["Bifid mastoid FN","Risk of inadvertent FN palsy in mastoidectomy","HRCT; continuous FN EMG monitoring","Identify both trunks completely before drilling"],
      ["CULLP (Asymmetric Crying Facies)","Unilateral lower lip asymmetry on crying ONLY; rest of FN normal","ECG + Echocardiogram (cardiac defects 10%)","Reassurance; cardiac referral; no FN surgery"],
      ["Melkersson-Rosenthal","Recurrent FN palsy + lip oedema + fissured tongue","Labial biopsy (non-caseating granulomas)","Steroids acute; long-term doxycycline/HCQ"],
    ], C.navy, { colWidths:[22,28,28,22] }
  ),
  gap(),
  pbr(),

// ════════════════════ PART IX: NEONATAL TABLE ═════════════════════════════════
  h1("PART IX — NEONATAL FACIAL PALSY: DEVELOPMENTAL CAUSES"),
  body([itl("Based on Scott-Brown's Otorhinolaryngology, Table 112.8 (Vol 2)")]),
  gap(),
  tbl(
    ["Syndrome / Condition","Key Clinical Characteristics"],
    [
      ["Moebius Syndrome","Agenesis of CN VI + VII nuclei. Bilateral facial + abducens palsy. Other CNs may be involved."],
      ["Dystrophia Myotonica (Steinert's)","Bilateral facial palsy WITHOUT abducens palsy. Muscle wasting, swan-neck appearance."],
      ["Albers-Schönberg Disease (Osteopetrosis)","Dense bone stenoses FN canal → blindness, deafness, facial palsy. Presents in childhood."],
      ["Melkersson-Rosenthal Syndrome","Recurrent facial palsy + oro-facial oedema + fissured tongue."],
      ["CHARGE Association","Coloboma + heart defects + choanal atresia + growth retardation + genital hypoplasia + ear anomalies."],
      ["Oculo-Auriculo-Vertebral (OAV/Goldenhar)","Abnormal 1st + 2nd arch formation. Hemifacial microsomia, microtia, FN anomaly."],
      ["CULLP (Asymmetric Crying Facies)","Hypoplasia of depressor anguli oris muscle; lower lip asymmetry; cardiac defects ~10%."],
    ], C.teal, { colWidths:[30,70] }
  ),
  gap(),
  pbr(),

// ════════════════════ PART X: RECENT ADVANCES ════════════════════════════════
  h1("PART X — RECENT ADVANCES  (2021 – 2026)"),

  h3("1.  Aberrant FN in Congenital Hearing Loss  (2024)"),
  body("Hammami B et al. (Indian J Otolaryngol Head Neck Surg, 2024; PMID: 39130285) demonstrated that aberrant intratemporal facial nerve courses are significantly more prevalent in children with congenital hearing loss. Pre-operative high-resolution CT evaluation is now recommended before cochlear implantation in all congenital malformation cases to map FN position."),
  gap(),

  h3("2.  Retro-Facial Cochlear Implantation in Facial Nerve Deformity  (2024)"),
  body("Zou X et al. (Lin Chuang Er Bi Yan Hou, 2024; PMID: 38686480) documented successful cochlear implantation via retro-facial approach in a patient with severe congenital microtia and facial nerve deformity that precluded the standard approach. This confirms the retro-facial route as a viable option when FN anatomy is severely anomalous."),
  gap(),

  h3("3.  CHARGE Syndrome Temporal Bone Histopathology  (2022)"),
  body("da Costa Monsanto R et al. (Otolaryngol Head Neck Surg, 2022; PMID: 33874787) performed comprehensive temporal bone histopathology in CHARGE syndrome, confirming absent semicircular canals, cochlear hypoplasia, and agenesis of the intratemporal facial nerve canal as consistent pathological findings, supporting early aggressive hearing rehabilitation."),
  gap(),

  h3("4.  Imaging Protocol for Facial Nerve Assessment  (2023)"),
  body("Ottaiano AC et al. (Semin Ultrasound CT MR, 2023; PMID: 37055142) reviewed imaging anatomy of all facial nerve segments. Key conclusions: (a) HRCT is best for bony canal anomalies; (b) gadolinium-enhanced MRI is best for nerve pathology; (c) both are complementary and should be used together in congenital cases. Systematic evaluation of all five intratemporal segments is recommended."),
  gap(),

  h3("5.  Intraoperative Facial Nerve Monitoring — Current Standard of Care"),
  body("Continuous EMG-based FN monitoring (orbicularis oculi + orbicularis oris) is now the standard of care in all parotid, mastoid, and cochlear implant surgeries. It is ESPECIALLY critical in patients with known congenital anomalies or craniofacial syndromes (Scott-Brown Best Clinical Practice 2022). Monitoring shortens the surgical learning curve and reduces iatrogenic injury rates."),
  gap(),

  h3("6.  Genetics of Moebius Syndrome — Updated Understanding"),
  body("Mouse models of rhombomere 4 vascular disruption (PLCL1 gene) reproduce the Moebius phenotype, strongly supporting the vascular disruption hypothesis over pure nuclear aplasia. Loci: MBS1 (13q12.2) and MBS2 (3q21-q22). REV3L and PLCL1 gene mutations are identified in familial cases, opening the path for genetic counselling in affected families."),
  gap(),

  h3("7.  AI-Assisted Pre-Operative FN Mapping  (Emerging)"),
  body("Deep learning models trained on high-resolution temporal bone CT datasets are being developed to automatically segment and map the facial nerve canal pre-operatively, aiming to flag anomalies (aberrant course, dehiscence, bifurcation) before surgery. Early studies show >90% accuracy for canal segmentation. Clinical deployment is anticipated within 2–3 years."),
  gap(),
  pbr(),

// ════════════════════ PART XI: QUICK REVISION ════════════════════════════════
  h1("PART XI — QUICK REVISION  (RGUHS Exam Ready)"),

  h2("Key Numbers to Memorise"),
  tbl(
    ["Parameter","Value","Significance"],
    [
      ["Intracranial segment","24 mm","Traverses CPA — acoustic neuroma territory"],
      ["Labyrinthine segment","4 mm","Shortest; narrowest; no epineurium"],
      ["Tympanic segment","~13 mm","Most dehiscences; most iatrogenic injuries in cholesteatoma"],
      ["Mastoid segment","~20 mm","Longest intratemporal; most variable; posterior tympanotomy site"],
      ["Dehiscence above oval window","55–66% of ears","Bilateral in 75% (Shambaugh)"],
      ["Geniculate ganglion dehiscence","~25% of ears","Vulnerable in temporal bone fractures"],
      ["FN position in IAC","Anterosuperior","'Seven UP, Coke DOWN'"],
      ["Chorda tympani origin","4–6 mm above stylomastoid foramen","Branches off mastoid segment"],
      ["CULLP cardiac association","~10%","Mandatory cardiac workup"],
      ["Neonatal FN trauma recovery",">90% complete","Excellent prognosis conservative Rx"],
    ], C.navy
  ),
  gap(),

  h2("10 High-Yield RGUHS Exam Points"),
  bull("Facial nerve = nerve of 2nd branchial arch (Reichert's cartilage)", 0, true),
  bull("UMN palsy: forehead SPARED (bilateral cortical supply to superior nucleus)", 0, true),
  bull("Most common dehiscence site: tympanic segment ABOVE oval window (55–66%)", 0, true),
  bull("Most common dangerous congenital variant: lateral rotation of FN in aural atresia", 0, true),
  bull("Moebius = nuclear aplasia (CN VI + VII); bilateral; EMG absent from birth", 0, true),
  bull("CULLP = NOT true FN palsy; depressor anguli oris hypoplasia; 10% cardiac → echo mandatory", 0, true),
  bull("FN in IAC = anterosuperior quadrant — 'Seven up, Coke down'", 0, true),
  bull("Topographic order: Lacrimation (GSPN) → Stapedius reflex → Taste (chorda) → Motor only", 0, true),
  bull("ALL congenital craniofacial / atresia cases = MANDATORY intraoperative FN monitoring", 0, true),
  bull("Pre-stapedectomy HRCT = must rule out tympanic FN inferior to oval window", 0, true),
  gap(),
  pbr(),

// ════════════════════ REFERENCES ═════════════════════════════════════════════
  h1("REFERENCES"),
  body([bld("1. "), reg("Cummings CW et al. "), itl("Cummings Otolaryngology Head and Neck Surgery"), reg(", 7th Ed. Elsevier. Chapter 126 (Facial Nerve Anatomy, Injury, Repair) and Chapter 135 (Temporal Bone Imaging).")]),
  body([bld("2. "), reg("Gleeson M et al. (Eds). "), itl("Scott-Brown's Otorhinolaryngology Head & Neck Surgery"), reg(", 8th Ed. CRC Press. Volumes 1 & 2 — Facial Nerve Anatomy, Paediatric Facial Palsy (Table 112.8), Skull Base Anatomy.")]),
  body([bld("3. "), reg("Shambaugh GE, Glasscock ME. "), itl("Surgery of the Ear"), reg(", 6th Ed. BC Decker. Chapter 2 (Temporal Bone Anatomy — Facial Nerve) and Chapter 13 (Imaging Anomalies).")]),
  body([bld("4. "), reg("Maran AGD, Stell PM. "), itl("Stell & Maran's Head and Neck Surgery"), reg(", 4th Ed. Butterworth-Heinemann. Facial nerve anatomy and anomalies.")]),
  body([bld("5. "), reg("Dhingra PL, Dhingra S. "), itl("Diseases of Ear, Nose and Throat & Head and Neck Surgery"), reg(", 8th Ed. Elsevier India. Chapter on Facial Nerve.")]),
  body([bld("6. "), reg("Hazarika P. "), itl("Textbook of ENT & Head-Neck Surgery: Clinical & Practical"), reg(". CBS Publishers. Chapter on Facial Nerve Anatomy and Topographic Diagnosis.")]),
  body([bld("7. "), reg("Zakir Hussain M. "), itl("Textbook of Ear, Nose and Throat Diseases"), reg(". Paras Medical Publisher. Facial Nerve Anatomy and Congenital Anomalies.")]),
  body([bld("8. "), reg("Gray's Anatomy for Students"), reg(", 4th Ed. Elsevier. Head and Neck Chapter — Facial Nerve.")]),
  body([bld("9. "), reg("Ottaiano AC, Gomez GD, Freddi TAL. "), itl("The Facial Nerve: Anatomy and Pathology."), reg(" Semin Ultrasound CT MR. 2023 Apr. PMID: 37055142")]),
  body([bld("10. "), reg("Hammami B et al. "), itl("Aberrant Course of the Intratemporal Facial Nerve in Children with Congenital Hearing Loss."), reg(" Indian J Otolaryngol Head Neck Surg. 2024 Aug. PMID: 39130285")]),
  body([bld("11. "), reg("da Costa Monsanto R et al. "), itl("Otopathologic Abnormalities in CHARGE Syndrome."), reg(" Otolaryngol Head Neck Surg. 2022 Feb. PMID: 33874787")]),
  body([bld("12. "), reg("Zou X et al. "), itl("Cochlear implantation through retro-facial approach with congenital microtia and facial nerve deformity."), reg(" Lin Chuang Er Bi Yan Hou. 2024 May. PMID: 38686480")]),
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// ─────────────────────────────────────────────────────────────────────────────
//  BUILD CONTENT ARRAY
// ─────────────────────────────────────────────────────────────────────────────
const C2 = [];
const add = (...items) => items.forEach(it => Array.isArray(it)?it.forEach(x=>C2.push(x)):C2.push(it));

// ═══════════════════════ TITLE PAGE ══════════════════════════════════════════
add(
  gap(600),
  new Paragraph({ children:[bld("ANATOMY OF THE FACIAL NERVE",C.navy)], alignment:AlignmentType.CENTER,
    ...sp(0,120), run:{ font:FONT, size:52 } }),
  new Paragraph({ children:[new TextRun({ text:"ANATOMY OF THE FACIAL NERVE", font:FONT, size:52, bold:true, color:C.navy })],
    alignment:AlignmentType.CENTER, ...sp(0,120) }),
  new Paragraph({ children:[new TextRun({ text:"WITH CONGENITAL ANOMALIES", font:FONT, size:40, bold:true, color:C.blue })],
    alignment:AlignmentType.CENTER, ...sp(0,200) }),
  new Table({ rows:[new TableRow({ children:[new TableCell({
    children:[
      new Paragraph({ children:[new TextRun({ text:"50-Mark Answer  |  RGUHS University Standard", font:FONT, size:26, bold:true, color:C.white })], alignment:AlignmentType.CENTER }),
      new Paragraph({ children:[new TextRun({ text:"ENT & Head-Neck Surgery — Postgraduate Study Guide with Diagrams", font:FONT, size:22, italics:true, color:C.ltblue })], alignment:AlignmentType.CENTER, ...sp(60,0) }),
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  new Paragraph({ children:[new TextRun({ text:"Cummings · Scott-Brown's · Shambaugh · Stell & Maran · Dhingra · Hazarika · Zakir Hussain · PubMed 2021–2026", font:FONT, size:20, italics:true, color:"555555" })], alignment:AlignmentType.CENTER, ...sp(40,600) }),
  pbr(),
);

// ═══════════════════════ PART I: INTRODUCTION ════════════════════════════════
add(
  h1("PART I — INTRODUCTION"),
  body("The facial nerve (CN VII) is the nerve of the second branchial arch (Reichert's cartilage). It is the most complex cranial nerve, carrying five distinct fiber types, and traverses the longest intrabony canal of any cranial nerve — the fallopian canal. Its intimate anatomical relationship with the temporal bone, parotid gland, middle ear, and skull base makes detailed knowledge essential for every otolaryngologist and head & neck surgeon."),
  gap(),
  infoBox("⚡ CORE CONCEPT",["Facial nerve = nerve of 2nd branchial arch (Reichert's cartilage).","Carries 5 fiber types through 6 anatomical segments.","Only cranial nerve to traverse a complete bony canal within a single bone.","Labyrinthine segment = SHORTEST (4 mm) and NARROWEST portion of the fallopian canal."], C.ltblue, C.blue),
  gap(),
);

// ═══════════════════════ PART II: EMBRYOLOGY ═════════════════════════════════
add(
  h1("PART II — EMBRYOLOGY"),
  body("The facial nerve arises from the facioacoustic primordium in the 4th week. By the 5th week of fetal development, the chorda tympani separates from the main trunk. The facial nucleus forms from neuroblasts in the pons, with the 6th nerve nucleus in close proximity. As the pons expands during development, the 6th nucleus ascends — the facial nerve fibres must whirl around the 6th nucleus forming an internal genu. This explains why inflammatory or vascular events at this site (e.g., Moebius syndrome) involve both CN VI and CN VII."),
  gap(),
  h3("Figure 1 — Fetal Facial Nerve at 5 Weeks (Scott-Brown's Fig. 21.1)"),
  imgPara("fig4_fetal_fn_opt.jpg", 4.5),
  caption("Figure 1: Line diagram of the fetal head at 5 weeks showing the facial nerve and second branchial arch.\n(Source: Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 2, Figure 21.1)"),
  gap(),
  h3("Figure 2 — Neonatal Temporal Bone (Scott-Brown's Fig. 21.2)"),
  imgPara("fig5_neonatal_tb_opt.jpg", 4.5),
  caption("Figure 2: Neonatal temporal bone showing absence of mastoid process and incomplete tympanic ring. Note superficial position of stylomastoid foramen — critical for avoiding FN injury in neonatal surgery.\n(Source: Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 2, Figure 21.2)"),
  infoBox("📌 Clinical Significance of Neonatal Temporal Bone",["No mastoid process at birth → stylomastoid foramen is SUPERFICIALLY positioned.","Risk of facial nerve injury in post-auricular incisions and parotid surgery in neonates.","Mastoid process develops over first 2 years of life, gradually deepening the facial nerve."], C.ltyell, C.amber),
  gap(), pbr(),
);

// ═══════════════════════ PART III: NUCLEI & FIBRES ═══════════════════════════
add(
  h1("PART III — NUCLEI AND FIBER COMPOSITION"),
  h2("A.  Three Brainstem Nuclei"),
  tbl(["Nucleus","Location","Fiber Type","Function"],
    [["Motor nucleus (VII)","Caudal pons","SVE – Special Visceral Efferent","Facial expression, stapedius, stylohyoid, posterior belly digastric"],
     ["Superior salivatory nucleus","Dorsal to motor nucleus, pons","GVE – General Visceral Efferent","Preganglionic parasympathetics → lacrimal, nasal, submandibular, sublingual glands"],
     ["Nucleus of solitary tract (NTS)","Medulla oblongata","SVA + GVA","Taste (anterior 2/3 tongue, soft palate); visceral sensation (nose, pharynx, palate)"]],
    C.navy, { colWidths:[22,20,22,36] }),
  gap(),
  infoBox("📌 UMN vs. LMN — Forehead Sparing",
    ["Superior FN nucleus (frontalis, orbicularis oculi) = BILATERAL cortical input.",
     "Inferior FN nucleus (lower face) = ONLY ipsilateral input.",
     "UMN lesion → forehead SPARED   |   LMN lesion → ENTIRE face affected."],
    C.ltyell, C.amber),
  gap(),
  h2("B.  Five Fiber Types"),
  tbl(["Fiber Type","Abbrev.","Function","Pathway"],
    [["Special Visceral Efferent","SVE","Motor to muscles of facial expression","Main trunk CN VII"],
     ["General Visceral Efferent","GVE","Secretomotor (parasympathetic)","GSPN → lacrimal; Chorda tympani → sub-mandibular/sublingual"],
     ["Special Visceral Afferent","SVA","Taste","Ant. 2/3 tongue via chorda tympani; palate/tonsil via GSPN"],
     ["General Somatic Afferent","GSA","Touch, proprioception","EAC, concha, facial muscles"],
     ["General Visceral Afferent","GVA","Visceral sensation","Mucosa of nose, pharynx, palate"]],
    C.teal),
  gap(),

  h3("Figure 3 — Schematic Diagram of CN VII (Localization in Clinical Neurology)"),
  imgPara("fig3_fn_schematic_opt.jpg", 5.2),
  caption("Figure 3: Complete schematic diagram of cranial nerve VII (facial nerve) showing all branches, nuclei, and connections.\n(Source: Localization in Clinical Neurology, 8th Ed., Figure 10-1)"),
  gap(), pbr(),
);

// ═══════════════════════ PART IV: COURSE & SEGMENTS ══════════════════════════
add(
  h1("PART IV — COURSE AND SEGMENTS"),
  body([bld("Mnemonic: "), reg('"I Can Learn To Master Surgery" = Intracranial · Canalicular · Labyrinthine · Tympanic · Mastoid · Stylomastoid (extratemporal)')]),
  gap(),
  divider("COMPLETE COURSE OF THE FACIAL NERVE — FLOWCHART"),
  flowBox([
    "  MOTOR CORTEX  (precentral gyrus)",
    "        │  Corticobulbar fibres",
    "        │  (bilateral → upper face;  ipsilateral → lower face)",
    "        ▼",
    "  ┌──────────────────────────────────────────────────────────────────┐",
    "  │   BRAINSTEM NUCLEI: Motor Nucleus + SSN + NTS  (Caudal pons)    │",
    "  └──────────────────────────────────────────────────────────────────┘",
    "        │",
    "  ══════╪════════════════════════════════════════════════════════════",
    "   [1]  INTRACRANIAL (CISTERNAL) SEGMENT         24 mm",
    "        Pons → Porus of IAC  |  Traverses CPA",
    "        Nervus intermedius joins here",
    "  ══════╪════════════════════════════════════════════════════════════",
    "   [2]  INTRACANALICULAR (MEATAL) SEGMENT        ~8 mm",
    "        Porus → Fundus of IAC  |  ANTEROSUPERIOR quadrant",
    "        'Seven UP,  Coke DOWN'",
    "        Bill's Bar (vertical crest) at fundus",
    "  ══════╪════════════════════════════════════════════════════════════",
    "   [3]  LABYRINTHINE SEGMENT  ← SHORTEST (4 mm) & NARROWEST",
    "        Fundus → Geniculate Ganglion",
    "        Between cochlea and vestibule",
    "        No epineurium · Watershed blood supply zone",
    "        ➤ 1st GENU (acute posterior turn ~120°)",
    "        ➤ GSPN exits here at geniculate ganglion",
    "  ══════╪════════════════════════════════════════════════════════════",
    "   [4]  TYMPANIC (HORIZONTAL) SEGMENT            ~13 mm",
    "        Geniculate ganglion → 2nd genu",
    "        Medial wall of middle ear",
    "        Over: Cochleariform process → Oval window niche",
    "        MOST COMMON site of fallopian canal dehiscence",
    "  ══════╪════════════════════════════════════════════════════════════",
    "   [5]  MASTOID (VERTICAL) SEGMENT  ← LONGEST    ~20 mm",
    "        2nd genu → Stylomastoid foramen",
    "        Behind EAC · Anterior to sigmoid sinus",
    "        ➤ Nerve to stapedius (near pyramidal eminence)",
    "        ➤ Chorda tympani (4–6 mm above stylomastoid foramen)",
    "        ➤ Facial recess (posterior tympanotomy triangle)",
    "  ══════╪════════════════════════════════════════════════════════════",
    "  STYLOMASTOID FORAMEN",
    "   [6]  EXTRATEMPORAL SEGMENT",
    "        → Post. auricular nerve (occipitalis, post. auricular m.)",
    "        → Digastric (post. belly) + stylohyoid",
    "        → PAROTID GLAND → Temporofacial + Cervicofacial divisions",
    "        → Five terminal branches: T · Z · B · M · C",
    "           Mnemonic: 'Two Zebras Bit My Cat'",
  ]),
  gap(),
  h2("Segment Summary Table  (Cummings / Shambaugh)"),
  tbl(["Segment","Length","Key Feature","Landmark","Branch"],
    [["1. Intracranial (Cisternal)","24 mm","CPA traversal; nervus intermedius joins","Porus of IAC","—"],
     ["2. Meatal (Intracanalicular)","~8 mm","Anterosuperior quadrant IAC","Bill's bar (vertical crest)","—"],
     ["3. Labyrinthine","4 mm (SHORTEST)","Narrowest; no epineurium; watershed","Meatal foramen; geniculate ganglion","GSPN; 1st genu"],
     ["4. Tympanic (Horizontal)","~13 mm","Medial wall middle ear; most dehiscences","Cochleariform process; oval window","2nd genu"],
     ["5. Mastoid (Vertical)","~20 mm (LONGEST)","Most variable; behind EAC","Pyramidal eminence; lateral SCC","Nerve to stapedius; Chorda tympani"],
     ["6. Extratemporal","Variable","5 branches in parotid","Digastric aponeurosis","5 terminal branches"]],
    C.navy, { colWidths:[22,12,26,24,16] }),
  gap(),
);

// ── IAC DIAGRAM ──────────────────────────────────────────────────────────────
add(
  h3("Figure 4 — Rotation of Facial Nerve through IAC (Shambaugh Fig. 2-19)"),
  imgPara("fig1_IAC_rotation_opt.jpg", 5.0),
  caption("Figure 4: Rotation of the facial, cochlear, and vestibular nerves as they traverse the internal auditory canal. The facial nerve lies anterosuperiorly ('Seven UP'), the cochlear nerve anteroinferiorly ('Coke DOWN'), and vestibular nerves posteriorly.\n(Source: Shambaugh Surgery of the Ear, Figure 2-19; after Nadol & Schuknecht)"),
  gap(),
);

// ── LABYRINTHINE SEGMENT DIAGRAM ─────────────────────────────────────────────
add(
  h3("Figure 5 — Labyrinthine Segment and IAM Relations (Scott-Brown's Fig. 112.3)"),
  imgPara("fig6_labyrinthine_opt.jpg", 5.0),
  caption("Figure 5: Colour-coded anatomical diagram of the labyrinthine segment. The facial nerve runs laterally, anterior to the superior vestibular nerve in the IAM. This relationship is critical in middle fossa and translabyrinthine approaches. Bill's bar and the crista falciformis are identifiable at the fundus.\n(Source: Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Vol. 2, Figure 112.3)"),
  gap(),
);

// ── SURGICAL LANDMARKS TABLE ─────────────────────────────────────────────────
add(
  h2("Surgical Landmarks by Segment  (Cummings Table 126.1)"),
  tbl(["Segment","Primary Surgical Landmark(s)"],
    [["Labyrinthine segment","Vertical crest — Bill's Bar"],
     ["Geniculate ganglion","Retrograde dissection of GSPN (middle fossa approach)"],
     ["Tympanic segment (anterior)","Cochleariform process"],
     ["Tympanic segment (posterior)","Oval window niche"],
     ["Second genu","Oval window"],
     ["Mastoid segment","Pyramidal eminence · lateral SCC · short process incus · chorda tympani"],
     ["Stylomastoid foramen","Cephalic edge and aponeurosis of posterior belly digastric"]],
    C.teal, { firstColHeader:true }),
  gap(), pbr(),
);

// ═══════════════════════ PART V: EXTRATEMPORAL BRANCHES ══════════════════════
add(
  h1("PART V — EXTRATEMPORAL BRANCHES AND TERMINAL DIVISIONS"),
  h3("Figure 6 — Facial Nerve Divisions and Terminal Branches"),
  imgPara("fig8_fn_divisions_opt.jpg", 5.5),
  caption("Figure 6: Diagram of the facial nerve and its divisions in relation to the skull. Yellow lines indicate nerve pathways from the parotid to the five terminal branches supplying muscles of facial expression.\n(Source: Tintinalli's Emergency Medicine — Facial Nerve Anatomy)"),
  gap(),
  flowBox([
    "  STYLOMASTOID FORAMEN",
    "         │",
    "         ├─── Posterior Auricular Nerve (occipitalis, post. auricular m.)",
    "         ├─── Branch to posterior belly Digastric",
    "         ├─── Branch to Stylohyoid",
    "         │",
    "         └─── PAROTID GLAND",
    "                     │",
    "          ┌───────────┴────────────────┐",
    "    TEMPOROFACIAL div.          CERVICOFACIAL div.",
    "          │                            │",
    "    ┌─────┴──────┐             ┌───────┴──────────┐",
    "  Temporal    Zygomatic      Buccal   Marginal     Cervical",
    "  branch      branch         branch   Mandibular   branch",
    "     │            │             │     branch          │",
    "  Frontalis   Zygomaticus   Buccinator  Depressor   Platysma",
    "  Orbic.oculi Levator labii  Orbic.oris  anguli oris",
    "  Corrugator                Nasalis     Mentalis",
    "  ─────────────────────────────────────────────────────────────",
    "  Mnemonic: 'Two Zebras Bit My Cat'",
    "  T=Temporal · Z=Zygomatic · B=Buccal · M=Marginal Mandibular · C=Cervical",
  ]),
  gap(), pbr(),
);

// ═══════════════════════ PART VI: INTRATEMPORAL BRANCHES ══════════════════════
add(
  h1("PART VI — INTRATEMPORAL BRANCHES"),
  tbl(["Branch","Origin","Course","Function"],
    [["GSPN (Greater Superficial Petrosal Nerve)","Geniculate ganglion (anterior)","MCF floor → foramen lacerum → vidian nerve → pterygopalatine ganglion","Secretomotor: lacrimal, nasal/palatine glands; taste from soft palate"],
     ["Nerve to Stapedius","Mastoid segment near pyramidal eminence","Canaliculus → stapedius muscle","Motor: stapedius (acoustic reflex) — loss → hyperacusis"],
     ["Chorda Tympani","Mastoid segment ~4–6 mm above stylomastoid foramen","Iter chordae posterius → crosses medial to malleus, lateral to incus → iter chordae anterius → petrotympanic fissure → lingual nerve","Taste: anterior 2/3 tongue; Secretomotor: submandibular + sublingual glands"]],
    C.navy, { colWidths:[22,18,35,25] }),
  gap(),
  h3("Figure 7 — Tympanic Section Showing Facial Nerve (G), Chorda Tympani (C), Cochleariform Process (H)"),
  imgPara("fig9_tympanic_section_opt.jpg", 5.2),
  caption("Figure 7: Histological section showing the facial nerve (G), chorda tympani (C), cochleariform process (H), malleus (A), tympanic membrane (B), incus (D), stapes (F), tensor tympani (I), lateral semicircular canal (M), and internal auditory canal (O).\n(Source: K.J. Lee's Essential Otolaryngology, Figure 13-15)"),
  gap(), pbr(),
);

// ═══════════════════════ PART VII: BLOOD SUPPLY ═══════════════════════════════
add(
  h1("PART VII — BLOOD SUPPLY"),
  tbl(["Segment","Arterial Supply","System"],
    [["Intracranial + Labyrinthine (meatal)","Labyrinthine artery (branch of AICA)","Vertebrobasilar"],
     ["Geniculate ganglion + Tympanic segment","Petrosal branch of middle meningeal artery","External carotid (via middle meningeal)"],
     ["Mastoid segment + Stylomastoid foramen","Stylomastoid artery (branch of posterior auricular artery)","External carotid"]],
    C.green),
  gap(),
  infoBox("⚡ WATERSHED ZONE — Labyrinthine Segment",
    ["Junction of vertebrobasilar and ECA supply + no epineurium + no vascular plexus.",
     "This triple vulnerability explains Bell's palsy predilection for this segment.",
     "Oedema → compression → ischaemia → axonal injury (Sunderland classification).",
     "Treatment implication: steroids within 72 hrs reduce oedema and improve outcomes."],
    C.ltred, C.red),
  gap(), pbr(),
);

// ═══════════════════════ PART VIII: TOPOGRAPHIC DIAGNOSIS ════════════════════
add(
  h1("PART VIII — TOPOGRAPHIC DIAGNOSIS"),
  divider("TOPOGRAPHIC DIAGNOSIS FLOWCHART"),
  flowBox([
    "  FACIAL PALSY — DETERMINE LEVEL OF LESION",
    "",
    "  Step 1: LACRIMATION impaired?  (Schirmer's test / GSPN)",
    "          │",
    "          ├── YES → Lesion at or PROXIMAL to geniculate ganglion",
    "          │         (Labyrinthine, meatal, CPA, or brainstem)",
    "          │",
    "          └── NO  → Step 2",
    "",
    "  Step 2: STAPEDIAL REFLEX absent?  (Impedance audiometry)",
    "          │",
    "          ├── YES → Lesion between GSPN and nerve to stapedius",
    "          │         (Tympanic / proximal mastoid segment)",
    "          │",
    "          └── NO  → Step 3",
    "",
    "  Step 3: TASTE impaired?  (Electrogustometry / chorda tympani)",
    "          │",
    "          ├── YES → Lesion between stapedius nerve and chorda tympani",
    "          │         (Mastoid segment, distal to pyramidal eminence)",
    "          │",
    "          └── NO  → PURELY MOTOR palsy",
    "                    Lesion at or distal to stylomastoid foramen",
    "                    (Parotid / extratemporal / peripheral)",
  ]),
  gap(),
  tbl(["Level of Lesion","Lacrimation","Stapedial Reflex","Taste","Common Cause"],
    [["CPA / IAC / Labyrinthine","Impaired","Absent","Impaired","Vestibular schwannoma; Bell's palsy; herpes zoster oticus"],
     ["Tympanic segment","Normal","Absent","Impaired","Otitis media; cholesteatoma; temporal bone fracture"],
     ["Mastoid segment","Normal","Normal","Impaired","Mastoiditis; cholesteatoma; fracture"],
     ["Stylomastoid / Extratemporal","Normal","Normal","Normal","Parotid tumour; forceps delivery; Bell's palsy (distal)"]],
    C.teal),
  gap(), pbr(),
);

// ═══════════════════════ PART IX: CONGENITAL ANOMALIES ═══════════════════════
add(
  h1("PART IX — CONGENITAL ANOMALIES OF THE FACIAL NERVE"),
  divider("CLASSIFICATION FLOWCHART"),
  flowBox([
    "  CONGENITAL ANOMALIES OF FACIAL NERVE",
    "                    │",
    "       ┌────────────┴────────────────────────────────────┐",
    "       │                                                  │",
    "  NUCLEAR / CENTRAL                       PERIPHERAL / INTRATEMPORAL",
    "  (Brainstem origin)                       (Canal & nerve anomalies)",
    "       │                                                  │",
    "  ┌────┴──────────────────────┐        ┌─────────────────┴────────────────┐",
    "  │                           │        │                                  │",
    " Moebius syndrome            CHARGE  COURSE/POSITION              CANAL/NERVE",
    " Dystrophia myotonica        OAV       │                               │",
    " Poland syndrome             MRS   ┌───┴──────────┐          ┌─────────┴──────────┐",
    " CULLP                           Aberrant     Bifurcation  Dehiscence          Aplasia/",
    "                                 course       /Duplication  (Fallopian          Agenesis",
    "                                 patterns                    canal)",
  ]),
  gap(),
);

// ── NUCLEAR ANOMALIES ─────────────────────────────────────────────────────────
add(
  h2("A.  Nuclear / Central Anomalies"),
  h3("1.  Moebius Syndrome"),
  banner("DEFINITION: Agenesis / hypoplasia of CN VI (abducens) + CN VII (facial) motor nuclei in the pons", C.navy),
  gap(80),
  tbl(["Feature","Details"],
    [["Cranial nerves","CN VI + VII (bilateral, rarely unilateral); CN III, V, IX, X, XII in some cases"],
     ["Facial appearance","Mask-like face; cannot smile, frown, whistle, or close eyes; drooling"],
     ["Ocular","Bilateral horizontal gaze palsy (abducens) — hallmark distinguishing feature"],
     ["Feeding / speech","Dysarthria, dysphagia, feeding difficulty in neonates"],
     ["Limb defects","Poland sequence (chest/upper limb); talipes equinovarus"],
     ["Pathogenesis","Rhombomere 4 vascular disruption (subclavian artery disruption theory)"],
     ["Genetics","MBS1 (13q12.2); MBS2 (3q21-q22); PLCL1 and REV3L gene mutations"],
     ["Investigation","MRI: absent/hypoplastic facial colliculi; EMG: ABSENT potentials at birth"],
     ["Management","Free muscle transfer (gracilis/pectoralis minor); gold weight eyelid; speech therapy"]],
    C.blue, { firstColHeader:true, colWidths:[25,75] }),
  gap(),
  infoBox("📌 Key Distinction: Moebius vs. Birth Trauma Facial Palsy",
    ["Birth trauma → EMG shows PRESENT potentials at birth with progressive amplitude decline.",
     "Moebius / congenital developmental → EMG shows ABSENT potentials from birth (no nucleus)."],
    C.ltyell, C.amber),
  gap(),

  h3("2.  CHARGE Syndrome"),
  body([bld("Acronym: "), reg("C=Coloboma · H=Heart defects · A=choanal Atresia · R=Retarded growth · G=Genital hypoplasia · E=Ear anomalies")]),
  bull("FN palsy: aplasia of fallopian canal and/or facial nerve agenesis"),
  bull("Temporal bone: absent semicircular canals, cochlear hypoplasia (Mondini-type)"),
  bull("Genetics: CHD7 gene mutation (8q12.2)"),
  bull("Management: multidisciplinary; BAHA or cochlear implant; cardiac surgery; ophthalmology"),
  gap(),

  h3("3.  Dystrophia Myotonica"),
  bull("Bilateral facial palsy WITHOUT abducens palsy — distinguishes from Moebius"),
  bull("CTG repeat expansion, chromosome 19q13 — autosomal dominant"),
  bull("'Hatchet face' / 'swan-neck': wasting of facial, SCM, and masticatory muscles"),
  bull("Features: myotonia, cataracts, cardiac conduction defects, diabetes"),
  gap(),

  h3("4.  Congenital Unilateral Lower Lip Palsy (CULLP) / Asymmetric Crying Facies"),
  infoBox("⚡ NOT a true facial nerve palsy!",
    ["Cause: Hypoplasia or ABSENCE of the depressor anguli oris muscle — not the nerve.",
     "Presentation: Lower lip asymmetry ONLY on crying. All other FN functions are NORMAL.",
     "Cardiac defects in ~10% of cases → mandatory echocardiogram + ECG in ALL cases.",
     "Prognosis: Excellent. No facial nerve surgery needed."],
    C.ltred, C.red),
  gap(),

  h3("5.  Oculo-Auriculo-Vertebral Spectrum / Goldenhar Syndrome"),
  bull("Abnormal formation of first AND second branchial arches"),
  bull("Hemifacial microsomia + microtia + aural atresia + FN hypoplasia/aberrant course"),
  bull("Facial nerve may be hypoplastic or have aberrant mastoid course"),
  gap(),

  h3("6.  Melkersson-Rosenthal Syndrome"),
  bull("Classic triad: Recurrent facial palsy + oro-facial oedema + fissured tongue"),
  bull("Biopsy: non-caseating granulomatous inflammation"),
  bull("Management: corticosteroids (acute); doxycycline/hydroxychloroquine (long-term); cheiloplasty"),
  gap(), pbr(),
);

// ── PERIPHERAL ANOMALIES ──────────────────────────────────────────────────────
add(
  h2("B.  Peripheral / Intratemporal Anomalies"),

  h3("1.  Fallopian Canal Dehiscence  —  Most Common Congenital Anomaly"),
  divider("SITES OF DEHISCENCE (by frequency)"),
  flowBox([
    "  FALLOPIAN CANAL DEHISCENCE",
    "",
    "  Rank   Site                                   Frequency",
    "  ─────  ────────────────────────────────────   ─────────",
    "  1st    Tympanic segment ABOVE oval window     55–66%",
    "         Bilateral in ~75% (Shambaugh)",
    "  2nd    Distal tympanic segment / 2nd genu     ~20%",
    "  3rd    Geniculate ganglion (thin/absent bone) ~25% of all ears (Cummings)",
    "  4th    Mastoid segment                        Uncommon",
    "",
    "  Clinical consequences:",
    "  ● FN exposed to infection in AOM/CSOM → facial palsy",
    "  ● Prolapsed nerve → middle ear mass (mimics glomus tumour)",
    "  ● Iatrogenic injury during mastoidectomy / middle ear surgery",
    "  ● GSPN traction → intraoperative facial palsy (middle fossa)",
  ]),
  gap(),

  h3("Figure 8 — Dehiscent Facial Nerve at Oval Window (Shambaugh)"),
  imgPara("fig2_dehiscent_oval_opt.jpg", 5.0),
  caption("Figure 8: Histological section showing a dehiscent facial nerve overhanging the stapes footplate and stapediovestibular articulation. Note the absence of bony covering over the nerve — the most common site of congenital dehiscence.\n(Source: Shambaugh Surgery of the Ear — Facial nerve dehiscent at oval window)"),
  gap(),

  h3("2.  Aberrant Course of the Facial Nerve"),
  tbl(["Anomaly","Description","Clinical Significance"],
    [["Inferior displacement of tympanic segment (MOST IMPORTANT)","Tympanic FN descends ANTERIOR + INFERIOR to oval window; may cover the stapes footplate entirely","Highest risk in stapedectomy — procedure may be impossible. HRCT mandatory before stapes surgery."],
     ["Anteroinferior course over promontory","FN crosses promontory, may overlie round window niche","Risk during myringotomy and round window procedures"],
     ["Mastoid segment posterior bulge","Nerve bulges posterolaterally more than normal","Risk during cortical mastoidectomy"],
     ["Lateral rotation in aural atresia","Mastoid segment rotated laterally — minor obliquity to true horizontal course","MOST dangerous variant in atresia. Pre-op HRCT MANDATORY."],
     ["Superficial stylomastoid foramen (neonates)","Nerve exits superficially (immature mastoid, no mastoid tip)","High risk of FN injury in post-auricular/parotid surgery in neonates"]],
    C.navy, { colWidths:[22,42,36] }),
  gap(),

  h3("3.  Bifurcation / Duplication of the Facial Nerve"),
  bull("Rare: vertical (mastoid) segment may be BIPARTITE or TRIPARTITE — Shambaugh"),
  bull("Glastonbury et al.: congenital bifurcation of intratemporal FN (cited in Scott-Brown)"),
  bull("SURGICAL HAZARD: Surgeon sections one division mistaking it for a vessel"),
  bull("Mandatory: FN monitoring + complete identification of both trunks before drilling"),
  gap(),

  h3("4.  Agenesis / Aplasia of the Facial Nerve"),
  bull("Complete agenesis: total absence — seen with complete aural atresia + microtia"),
  bull("Partial aplasia/hypoplasia: reduced calibre → congenital facial paresis (not complete palsy)"),
  bull("Canal stenosis: narrow fallopian canal + hypoplastic nerve → INTERMITTENT EPISODIC facial paresis"),
  bull("Isolated facial nerve agenesis reported (Jervis & Bull, J Laryngol Otol 2001; cited Scott-Brown)"),
  gap(),

  h3("5.  Facial Nerve in Congenital Aural Atresia  —  Most Clinically Important Group"),
  divider("FACIAL NERVE IN AURAL ATRESIA — FLOWCHART"),
  flowBox([
    "  CONGENITAL AURAL ATRESIA — FACIAL NERVE RISK",
    "",
    "  Jahrsdoerfer Grade I (Mild)",
    "   └── FN usually normal position; minor anomalies",
    "",
    "  Jahrsdoerfer Grade II (Moderate)",
    "   └── FN may be anteriorly displaced; monitor closely",
    "",
    "  Jahrsdoerfer Grade III (Severe) — HIGHEST RISK",
    "   ├── Mastoid FN ROTATED LATERALLY (most common anomaly)",
    "   │       Range: minor obliquity → true horizontal course",
    "   ├── Vertical segment of FN canal absent",
    "   ├── Bifid vertical segment (bipartite nerve)",
    "   ├── FN crossing middle ear cavity (rare, catastrophic risk)",
    "   └── Stylomastoid foramen in abnormal/anterior position",
    "",
    "  Pre-operative Protocol:",
    "  ✔ HRCT temporal bone — MANDATORY before ANY atresia surgery",
    "  ✔ Jahrsdoerfer score ≥7 acceptable for surgical repair",
    "  ✔ Intraoperative continuous FN EMG monitoring — MANDATORY",
    "  ✔ Surgery deferred to age 5–6 years (temporal bone maturation)",
  ]),
  gap(), pbr(),
);

// ═══════════════════════ PART X: CLINICAL TABLE ═══════════════════════════════
add(
  h1("PART X — CLINICAL CORRELATION TABLE"),
  tbl(["Anomaly","Key Clinical Feature","Key Investigation","Management Priority"],
    [["Moebius Syndrome","Bilateral FN + abducens palsy; mask face; drooling","MRI brain (absent facial colliculi); EMG","Free muscle transfer; gold weight; speech therapy"],
     ["CHARGE Syndrome","FN palsy + deafness + coloboma + choanal atresia","HRCT/MRI temporal bone; CHD7 gene","Multidisciplinary; BAHA/CI for hearing"],
     ["Aural Atresia + FN anomaly","Conductive HL; high FN iatrogenic risk","HRCT (MANDATORY); Jahrsdoerfer score","FN monitoring; defer surgery to age 5–6"],
     ["Fallopian Canal Dehiscence","Silent OR FN palsy in AOM; middle ear mass","HRCT; intraoperative recognition","FN monitoring; urgent treat infection"],
     ["Tympanic FN below oval window","Obstructed stapes; risk in stapedectomy","HRCT before ALL stapes surgery","Abandon stapedectomy; senior surgeon"],
     ["Bifid mastoid FN","Risk of inadvertent palsy in mastoidectomy","HRCT; FN EMG monitoring","Identify both trunks completely"],
     ["CULLP (Asymmetric Crying Facies)","Lower lip asymmetry on crying ONLY; all else normal","ECG + Echocardiogram (cardiac 10%)","Reassurance; cardiac referral; no FN surgery"],
     ["Melkersson-Rosenthal","Recurrent FN palsy + lip oedema + fissured tongue","Labial biopsy (non-caseating granulomas)","Steroids; doxycycline/HCQ; cheiloplasty"]],
    C.navy, { colWidths:[22,28,25,25] }),
  gap(), pbr(),
);

// ═══════════════════════ PART XI: NEONATAL TABLE ══════════════════════════════
add(
  h1("PART XI — NEONATAL FACIAL PALSY: DEVELOPMENTAL CAUSES"),
  body([itl("Based on Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Table 112.8 (Vol. 2)")]),
  gap(),
  tbl(["Syndrome / Condition","Key Clinical Characteristics"],
    [["Moebius Syndrome","CN VI + VII nuclear agenesis. Bilateral facial + abducens palsy. Other CNs possible."],
     ["Dystrophia Myotonica (Steinert's)","Bilateral facial palsy WITHOUT abducens palsy. Muscle wasting, hatchet face."],
     ["Albers-Schönberg (Osteopetrosis)","Dense bone stenoses FN canal → blindness, deafness, facial palsy. Childhood onset."],
     ["Melkersson-Rosenthal Syndrome","Recurrent facial palsy + oro-facial oedema + fissured tongue."],
     ["CHARGE Association","Coloboma + heart defects + choanal atresia + growth retardation + genital hypoplasia + ear anomalies."],
     ["Oculo-Auriculo-Vertebral (OAV/Goldenhar)","Abnormal 1st + 2nd arch formation. Hemifacial microsomia, microtia, FN anomaly."],
     ["CULLP (Asymmetric Crying Facies)","Depressor anguli oris hypoplasia; lower lip asymmetry; cardiac defects ~10%."]],
    C.teal, { colWidths:[30,70] }),
  gap(), pbr(),
);

// ═══════════════════════ PART XII: HOUSE-BRACKMANN ════════════════════════════
add(
  h1("PART XII — HOUSE-BRACKMANN GRADING (Cummings / AAOHNS)"),
  h3("Figure 9 — House-Brackmann Grading Scale Diagram (Cummings Fig. 171.1)"),
  imgPara("fig7_HB_grade_opt.jpg", 3.0),
  caption("Figure 9: Modified House-Brackmann grading scale showing Grades I–VI with functional criteria including absolute movement, synkinesis, eye closure, resting asymmetry, and absolute paralysis.\n(Source: Cummings Otolaryngology Head and Neck Surgery, Figure 171.1)"),
  gap(),
  tbl(["Grade","Description","Clinical Features"],
    [["I — Normal","Normal function all areas","Symmetric movement; no weakness"],
     ["II — Slight","Slight weakness on close inspection","Normal at rest; slight asymmetry on movement; complete eye closure"],
     ["III — Moderate","Obvious but not disfiguring asymmetry","Obvious weak. on effort; incomplete eye closure; synkinesis possible"],
     ["IV — Moderately Severe","Disfiguring asymmetry","Obvious weakness at rest; incomplete eye closure"],
     ["V — Severe","Barely perceptible movement","Asymmetry at rest; barely perceptible movement"],
     ["VI — Total paralysis","No movement","Complete paralysis; no movement whatsoever"]],
    C.navy),
  gap(), pbr(),
);

// ═══════════════════════ PART XIII: RECENT ADVANCES ══════════════════════════
add(
  h1("PART XIII — RECENT ADVANCES  (2021–2026)"),

  h3("1.  Aberrant FN Course in Congenital Hearing Loss  (2024)"),
  body("Hammami B et al. (Indian J Otolaryngol Head Neck Surg, 2024; PMID: 39130285): Aberrant intratemporal FN courses are significantly more prevalent in children with congenital hearing loss. Pre-operative HRCT is now recommended before cochlear implantation in all congenital malformation cases."),
  gap(),

  h3("2.  Retro-Facial Cochlear Implantation in FN Deformity  (2024)"),
  body("Zou X et al. (Lin Chuang Er Bi Yan Hou, 2024; PMID: 38686480): Cochlear implantation via retro-facial approach was successfully performed in a patient with severe congenital microtia and FN deformity. The retro-facial route is viable when standard anatomy is precluded."),
  gap(),

  h3("3.  CHARGE Syndrome Temporal Bone Histopathology  (2022)"),
  body("da Costa Monsanto R et al. (Otolaryngol Head Neck Surg, 2022; PMID: 33874787): Consistent findings in CHARGE syndrome: absent semicircular canals, cochlear hypoplasia, agenesis of the intratemporal FN canal. Supports early aggressive hearing rehabilitation (CI/BAHA)."),
  gap(),

  h3("4.  Facial Nerve Imaging Protocol  (2023)"),
  body("Ottaiano AC et al. (Semin Ultrasound CT MR, 2023; PMID: 37055142): HRCT is best for bony canal anomalies; gadolinium MRI is best for nerve pathology. Both are complementary and should be used together in all congenital cases. Systematic evaluation of all 5 intratemporal segments is essential."),
  gap(),

  h3("5.  Intraoperative Monitoring — Current Standard of Care"),
  body("Continuous EMG-based FN monitoring (orbicularis oculi + orbicularis oris) is now the standard of care in ALL parotid, mastoid, and cochlear implant surgeries — especially critical in congenital/craniofacial anomaly cases (Scott-Brown 2022 Best Clinical Practice)."),
  gap(),

  h3("6.  Genetics of Moebius Syndrome"),
  body("Mouse models of rhombomere 4 vascular disruption (PLCL1 gene) reproduce the Moebius phenotype. Loci: MBS1 (13q12.2) + MBS2 (3q21-q22). REV3L and PLCL1 mutations identified in familial cases — genetic counselling now feasible."),
  gap(),

  h3("7.  AI-Assisted Pre-Operative FN Mapping (Emerging 2025–2026)"),
  body("Deep learning models trained on high-resolution temporal bone CT datasets can automatically segment and map the fallopian canal, flagging dehiscences, aberrant courses, and bifurcations. Early studies show >90% canal segmentation accuracy. Clinical deployment anticipated 2026–2027."),
  gap(), pbr(),
);

// ═══════════════════════ QUICK REVISION ══════════════════════════════════════
add(
  h1("PART XIV — QUICK REVISION  (RGUHS Exam)"),
  h2("Key Numbers"),
  tbl(["Parameter","Value","Significance"],
    [["Intracranial segment","24 mm","CPA — acoustic neuroma territory"],
     ["Labyrinthine segment","4 mm","SHORTEST; narrowest; no epineurium"],
     ["Tympanic segment","~13 mm","Most dehiscences; most iatrogenic injuries"],
     ["Mastoid segment","~20 mm","LONGEST intratemporal; most variable"],
     ["Dehiscence above oval window","55–66%","Bilateral in 75% (Shambaugh)"],
     ["Geniculate ganglion dehiscence","~25% of ears","Vulnerable in temporal bone fractures"],
     ["FN position in IAC","Anterosuperior","'Seven UP, Coke DOWN'"],
     ["Chorda tympani origin","4–6 mm above stylomastoid foramen","Mastoid segment branch"],
     ["CULLP cardiac association","~10%","Mandatory cardiac workup"],
     ["Neonatal FN trauma recovery",">90% complete","Excellent prognosis"]],
    C.navy),
  gap(),
  h2("10 High-Yield RGUHS Exam Points"),
  bull("FN = nerve of 2nd branchial arch (Reichert's cartilage)", 0, true),
  bull("UMN palsy: forehead SPARED (bilateral cortical supply to superior motor nucleus)", 0, true),
  bull("Most common dehiscence: tympanic segment ABOVE oval window (55–66%)", 0, true),
  bull("Most common dangerous surgical variant: lateral rotation in aural atresia", 0, true),
  bull("Moebius = CN VI + VII nuclear aplasia; bilateral; EMG absent from birth", 0, true),
  bull("CULLP = NOT true FN palsy; depressor anguli oris hypoplasia; 10% cardiac → echo mandatory", 0, true),
  bull("FN in IAC = anterosuperior quadrant — 'Seven UP, Coke DOWN'", 0, true),
  bull("Topographic diagnosis: Lacrimation (GSPN) → Stapedial reflex → Taste → Motor only", 0, true),
  bull("ALL congenital/craniofacial cases: MANDATORY intraoperative FN monitoring", 0, true),
  bull("Pre-stapedectomy HRCT: must exclude tympanic FN inferior to oval window", 0, true),
  gap(), pbr(),
);

// ═══════════════════════ REFERENCES ══════════════════════════════════════════
add(
  h1("REFERENCES"),
  body([bld("1. "), reg("Cummings CW et al. "), itl("Cummings Otolaryngology Head and Neck Surgery"), reg(", 7th Ed. Elsevier. Chapters 126 and 171.")]),
  body([bld("2. "), reg("Gleeson M et al. "), itl("Scott-Brown's Otorhinolaryngology Head & Neck Surgery"), reg(", 8th Ed. CRC Press. Volumes 1 & 2.")]),
  body([bld("3. "), reg("Shambaugh GE, Glasscock ME. "), itl("Surgery of the Ear"), reg(", 6th Ed. BC Decker. Chapters 2 and 13.")]),
  body([bld("4. "), reg("Maran AGD, Stell PM. "), itl("Stell & Maran's Head and Neck Surgery"), reg(", 4th Ed. Butterworth-Heinemann.")]),
  body([bld("5. "), reg("Dhingra PL, Dhingra S. "), itl("Diseases of Ear, Nose and Throat & Head and Neck Surgery"), reg(", 8th Ed. Elsevier India.")]),
  body([bld("6. "), reg("Hazarika P. "), itl("Textbook of ENT & Head-Neck Surgery: Clinical & Practical"), reg(". CBS Publishers.")]),
  body([bld("7. "), reg("Zakir Hussain M. "), itl("Textbook of Ear, Nose and Throat Diseases"), reg(". Paras Medical Publisher.")]),
  body([bld("8. "), reg("Gray's Anatomy for Students"), reg(", 4th Ed. Elsevier.")]),
  body([bld("9. "), reg("Ottaiano AC et al. The Facial Nerve: Anatomy and Pathology. "), itl("Semin Ultrasound CT MR."), reg(" 2023 Apr. PMID: 37055142")]),
  body([bld("10. "), reg("Hammami B et al. Aberrant Course of the Intratemporal Facial Nerve in Children with Congenital Hearing Loss. "), itl("Indian J Otolaryngol Head Neck Surg."), reg(" 2024 Aug. PMID: 39130285")]),
  body([bld("11. "), reg("da Costa Monsanto R et al. Otopathologic Abnormalities in CHARGE Syndrome. "), itl("Otolaryngol Head Neck Surg."), reg(" 2022 Feb. PMID: 33874787")]),
  body([bld("12. "), reg("Zou X et al. Cochlear implantation through retro-facial approach with congenital microtia and facial nerve deformity. "), itl("Lin Chuang Er Bi Yan Hou."), reg(" 2024. PMID: 38686480")]),
  gap(200),
);

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