Head and neck important topics
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Head & Neck - Important Topics for Medical Exam Preparation
Based on Gray's Anatomy for Students, Cummings Otolaryngology, and Goldman-Cecil Medicine.
1. Triangles of the Neck
Anterior Triangle
- Bounded by: midline of neck (medial), mandible (superior), anterior border of SCM (lateral)
- Subdivisions: submental, submandibular, carotid, muscular triangles
- Contents of carotid triangle: common carotid artery, internal jugular vein, vagus nerve (CN X)
Posterior Triangle
- Bounded by: posterior border of SCM (anterior), anterior border of trapezius (posterior), middle third of clavicle (inferior)
- Contents: accessory nerve [XI], external jugular vein, brachial plexus roots, subclavian artery (apex)
- High-yield: CN XI passes through the posterior triangle - injury causes paralysis of SCM and trapezius
2. Cranial Nerves - Complete Summary
| CN | Name | Exit from Skull | Key Function |
|---|---|---|---|
| I | Olfactory | Cribriform plate | Smell |
| II | Optic | Optic canal | Vision, pupillary light reflex (afferent) |
| III | Oculomotor | Superior orbital fissure | Eye movement (SR, MR, IR, IO), pupil constriction, lid elevation |
| IV | Trochlear | Superior orbital fissure | Superior oblique (eye moves down and in) |
| V | Trigeminal | V1: SOF; V2: Foramen rotundum; V3: Foramen ovale | Face sensation; muscles of mastication (V3 motor) |
| VI | Abducent | Superior orbital fissure | Lateral rectus (abduction) |
| VII | Facial | Stylomastoid foramen | Facial expression; taste ant. 2/3 tongue; lacrimal/submandibular/sublingual glands |
| VIII | Vestibulocochlear | Internal acoustic meatus | Hearing (cochlear) + balance (vestibular) |
| IX | Glossopharyngeal | Jugular foramen | Taste post. 1/3 tongue; parotid gland; stylopharyngeus; carotid body |
| X | Vagus | Jugular foramen | Viscera (thorax/abdomen); soft palate, pharynx, larynx |
| XI | Accessory | Jugular foramen | SCM + trapezius |
| XII | Hypoglossal | Hypoglossal canal | All tongue muscles (intrinsic + hyoglossus, genioglossus, styloglossus) |
(Gray's Anatomy for Students, Tables 8.4 & 8.5)
Cranial Nerve Lesion Mnemonics
| Nerve | Classic Lesion Finding |
|---|---|
| CN III | "Down and out" eye + dilated pupil + ptosis - posterior communicating artery aneurysm |
| CN IV | Can't look down and in - orbital fracture |
| CN VI | Can't abduct - cavernous sinus lesion |
| CN VII (upper motor) | Contralateral lower face paralysis (forehead spared) |
| CN VII (lower motor) | Ipsilateral entire face paralysis (Bell's palsy) |
| CN VIII | Progressive unilateral hearing loss + tinnitus - acoustic neuroma at cerebellopontine angle |
| CN X | Uvula deviates AWAY from the lesion |
| CN XII | Tongue deviates TOWARD the lesion (atrophied side) |
3. Cranial Nerve Reflexes
| Reflex | Afferent (sensory) | Efferent (motor) |
|---|---|---|
| Corneal (blink) reflex | CN V (trigeminal) | CN VII (facial) |
| Gag reflex | CN IX (glossopharyngeal) | CN X (vagus) |
| Pupillary light reflex | CN II (optic) | CN III (oculomotor) |
| Jaw jerk | CN V sensory | CN V motor |
(Gray's Anatomy for Students)
4. Skull Base Foramina - High-Yield
| Foramen/Structure | Contents |
|---|---|
| Cribriform plate | CN I (olfactory) |
| Optic canal | CN II, ophthalmic artery |
| Superior orbital fissure | CN III, IV, V1, VI + ophthalmic veins |
| Foramen rotundum | CN V2 (maxillary) |
| Foramen ovale | CN V3 (mandibular) |
| Foramen spinosum | Middle meningeal artery |
| Foramen lacerum | Internal carotid artery (passing through) |
| Jugular foramen | CN IX, X, XI + sigmoid sinus |
| Hypoglossal canal | CN XII |
| Stylomastoid foramen | CN VII (exits here) |
5. Thyroid & Parathyroid Glands
Thyroid Anatomy
- Located anterior to trachea, below thyroid cartilage
- Two lateral lobes + isthmus (crosses 2nd and 3rd tracheal cartilages)
- Develops from floor of pharynx at foramen cecum of tongue, migrates via thyroglossal duct
- Thyroglossal duct remnant = midline cyst (moves on tongue protrusion; Sistrunk procedure removes the hyoid body too)
Blood Supply
| Vessel | Origin | Supplies |
|---|---|---|
| Superior thyroid artery | First branch of external carotid | Superior pole |
| Inferior thyroid artery | Thyrocervical trunk (subclavian) | Inferior pole |
| Thyroid ima artery | Directly from aorta (variable, 3%) | Isthmus |
Surgical Danger - Recurrent Laryngeal Nerve
- The RLN is the most important structure at risk during thyroidectomy
- Right RLN loops under subclavian artery; left RLN loops under arch of aorta
- Injury = hoarseness (unilateral) or respiratory distress (bilateral)
- Superior laryngeal nerve (external branch) at risk from superior thyroid artery ligation - injury = loss of high-pitched voice (cricothyroid muscle)
Parathyroid Glands
- 4 glands on posterior surface of thyroid
- Superior = from 4th pharyngeal pouch; Inferior = from 3rd pharyngeal pouch (same as thymus - hence more variable position)
- Blood supply: inferior thyroid artery (both superior and inferior glands primarily)
(Gray's Anatomy for Students, p. 1157-1160; Current Surgical Therapy 14e)
6. Scalp Layers - "SCALP" Mnemonic
| Layer | Detail |
|---|---|
| S - Skin | Thick, hair-bearing |
| C - Connective tissue (dense) | Contains vessels and nerves; vessels cannot retract here - scalp wounds bleed profusely |
| A - Aponeurosis (epicranial / galea aponeurotica) | |
| L - Loose areolar tissue | "Danger zone" - infections spread here; connects to cavernous sinus via emissary veins |
| P - Pericranium | Periosteum of skull |
Scalp Nerve Supply
- Supratrochlear + Supra-orbital nerves (V1, ophthalmic) - anterior scalp
- Auriculotemporal nerve (V3, mandibular) - lateral scalp/temple
- Greater occipital nerve (C2 posterior ramus) - large area of posterior scalp
- Lesser occipital nerve (C2 anterior ramus) - posterior to ear
- Great auricular nerve (C2, C3) - posterior auricular area
Scalp Arterial Supply
- Anterior: supratrochlear and supra-orbital arteries (from ophthalmic artery - internal carotid system)
- Lateral: superficial temporal artery (terminal branch of external carotid)
- Posterior: occipital + posterior auricular arteries (external carotid)
7. Dural Venous Sinuses
| Sinus | Location | Receives |
|---|---|---|
| Superior sagittal | Superior border of falx cerebri | Superior cerebral veins + CSF |
| Inferior sagittal | Inferior margin of falx cerebri | Cerebral veins from falx |
| Straight sinus | Falx cerebri + tentorium junction | Inferior sagittal + great cerebral vein |
| Transverse sinus | Occipital bone | Confluence of sinuses |
| Sigmoid sinus | Petrous bone | Transverse sinus → internal jugular vein |
| Cavernous sinus | Body of sphenoid | Ophthalmic veins; CN III, IV, V1, V2, VI pass through walls |
High-yield: Emissary veins lack valves - infections from face (danger triangle) can spread to cavernous sinus
Cavernous sinus thrombosis: presents with proptosis, chemosis, CN III/IV/VI palsies, fever - danger area is upper lip/nose triangle
8. Facial Nerve [VII] - Key Details
- Intracranial course: internal acoustic meatus
- Intratemporal: facial canal in petrous bone → gives off greater petrosal nerve (lacrimal gland), nerve to stapedius, chorda tympani (sublingual/submandibular glands + ant. 2/3 tongue taste)
- Extracranial: exits stylomastoid foramen → passes through parotid gland → divides into 5 terminal branches: Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical ("To Zanzibar By Motor Car")
Upper vs lower motor neuron lesion of VII:
- UMN (cortical/stroke): forehead spared (bilateral cortical representation of forehead)
- LMN (Bell's palsy, parotid tumor, temporal bone fracture): forehead involved (entire ipsilateral face paralyzed)
9. Parotid Gland - High-Yield
- Largest salivary gland; located anterior to ear
- Facial nerve [VII] passes through parotid (but does not supply it)
- Parotid gland is supplied by the auriculotemporal nerve (CN V3) - carries parasympathetic fibers from CN IX → otic ganglion → auriculotemporal nerve
- Frey's syndrome (auriculotemporal nerve syndrome): sweating of cheek during eating after parotid surgery - misdirected regeneration of parasympathetic fibers to sweat glands
- Parotid duct (Stensen's duct) opens at the upper 2nd molar level
10. External Carotid Artery Branches
Mnemonic: "Some Anatomy Lessons Freaks Out Poor Students"
| Branch | Supplies |
|---|---|
| Superior thyroid | Superior pole thyroid |
| Ascending pharyngeal | Pharynx |
| Lingual | Tongue |
| Facial | Face |
| Occipital | Posterior scalp |
| Posterior auricular | Behind ear |
| Superficial temporal | Terminal branch - lateral scalp |
| Maxillary | Terminal branch - deep face, teeth, dura (middle meningeal) |
11. Neck Fascia - Clinical Importance
- Investing layer: surrounds all neck structures; splits to enclose SCM and trapezius
- Pretracheal fascia: encloses thyroid, trachea, esophagus; limits spread of infection
- Prevertebral fascia: covers vertebral column and deep muscles; retropharyngeal abscesses spread here
- Carotid sheath: contains common/internal carotid artery, internal jugular vein, vagus nerve (CN X)
Summary of High-Yield Exam Facts
- Danger triangle of face (nose to mouth corners) - venous drainage to cavernous sinus via ophthalmic veins; no valves
- Pterion - thinnest skull bone; underlies middle meningeal artery; traumatic epidural hematoma
- Pharyngeal arches - Arch 1: V3 (trigeminal); Arch 2: VII (facial); Arch 3: IX (glossopharyngeal); Arch 4 and 6: X (vagus)
- Thyroglossal duct cyst - midline, moves with tongue protrusion and swallowing
- Branchial cyst - anterior triangle, along anterior SCM border, from 2nd branchial cleft remnant
- Ludwig's angina - submandibular space infection; airway emergency
- Waldeyer's ring - tonsils (palatine + pharyngeal/adenoid + lingual) around pharynx; lymphoid tissue
- Larynx: CN X (recurrent laryngeal) innervates all intrinsic muscles EXCEPT cricothyroid (superior laryngeal, external branch, CN X)
Sources: Gray's Anatomy for Students (9780323934237); Cummings Otolaryngology Head and Neck Surgery (9780323612173); Goldman-Cecil Medicine (9780323930345)
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