Posterolateral Face Involvement with Ipsilateral (Homo-lateral) Hemiplegia

Understanding the Clinical Pattern

Primary Diagnosis: Opalski Syndrome (Submedullary Syndrome)

Definition

Mechanism

• Standard Wallenberg syndrome affects the lateral medulla above the pyramidal decussation → corticospinal tract not yet crossed → contralateral hemiplegia (which is typically absent since the pyramids are medial and spared).
• In Opalski syndrome, the lesion extends caudally into the lower medulla, below the level of the pyramidal decussation — i.e., into the submedullary/upper cervical region where the corticospinal tract has already crossed → damage here produces ipsilateral UMN hemiplegia.

"When ipsilateral hemiplegia is associated with symptoms of a lateral medullary syndrome, it corresponds to the submedullary syndrome of Opalski. The ipsilateral hemiplegia is due to the caudal extension of the lesion of the lower medulla involving the corticospinal tract after the pyramidal decussation." — Localization in Clinical Neurology, 8e

Etiology

• Steno-occlusive disease of the vertebral artery (VA)
• Vertebral artery dissection
• Compromise of medullary penetrating arteries

Full Clinical Picture of Lateral Medullary (Wallenberg) Syndrome + Opalski

Why Posterolateral Face Specifically?

• Ipsilateral facial loss of pain and temperature (tactile sense preserved — main sensory nucleus is in pons)
• The classic crossed sensory pattern: ipsilateral face + contralateral body (due to already-crossed spinothalamic tract)

Differential Diagnosis

1. Classic Wallenberg Syndrome (Lateral Medullary Syndrome)

• Same ipsilateral face + contralateral body sensory loss
• No hemiplegia (pyramids spared — medial medulla)
• Cause: PICA or vertebral artery occlusion
• Key distinguishing feature from Opalski: absence of ipsilateral motor deficit

2. Hemimedullary Syndrome (Babinski-Nageotte Syndrome)

• Combined lateral + medial medullary infarction simultaneously
• Ipsilateral face loss (CN V) + contralateral hemiplegia (medial medulla, above decussation) + ipsilateral tongue palsy (CN XII) + ipsilateral Horner + ipsilateral cerebellar signs
• Caused by proximal VA occlusion (before PICA and anterior spinal artery branches)

3. Medial Medullary Syndrome (Dejerine Syndrome)

• Contralateral hemiplegia (pyramids — above decussation)
• Contralateral loss of position/vibration (medial lemniscus)
• Ipsilateral tongue palsy (CN XII)
• No face involvement (spinal V tract spared)
• Cause: anterior spinal artery or VA medial branch occlusion

4. Lateral Pontomedullary Syndrome (AICA Territory)

• All Wallenberg features +
• Ipsilateral facial weakness (CN VII involvement)
• Ipsilateral tinnitus/hearing loss (CN VIII)
• No hemiplegia (unless extended)

5. Complete Unilateral Medullary Infarction (Reinhold Syndrome / Total Lateral Medullary Syndrome)

• All of Wallenberg + extension → crosses medial structures too
• Can have ipsilateral hemiplegia via submedullary mechanism

6. Cervical Cord (C1–C2) Lesion

• Ipsilateral hemiplegia (below decussation)
• Ipsilateral face involvement if ascending V tract involved
• But: typically no vestibular, cerebellar, or autonomic features of Wallenberg

7. Multiple Sclerosis / Demyelination

• Can produce any combination of brainstem signs
• Young patient, relapsing course, MRI lesions elsewhere

Imaging & Diagnostic Approach

• Axial DWI: hyperintense signal in the lateral medulla (Wallenberg) with extension toward the cervicomedullary junction (Opalski)
• MRA or CT angiography: vertebral artery stenosis/dissection
• If VA dissection suspected: fat-sat MRI of neck

DWI MRI: Hyperintensity (blue arrow) in right posterolateral medulla — Wallenberg syndrome. In Opalski, lesion extends more caudally.

Cross-sectional neuroanatomy: PICA territory and lateral medullary infarction subtypes. Opalski syndrome corresponds to extension into submedullary levels.

Summary Table: Key Differentials

• Localization in Clinical Neurology, 8e — Chapter 15, Opalski (Submedullary) Syndrome, p. 930
• Adams and Victor's Principles of Neurology, 12th ed. — Lateral Medullary Syndrome, p. 816
• Neuroanatomy through Clinical Cases, 3rd ed. — Table 14.7, Focal Vascular Syndromes of the Medulla

CN V (Trigeminal Nerve) — Full Distribution, Onion-Skin & Balaclava Patterns

Part 1: CN V Anatomy & Nuclear Complex

Four Nuclei of CN V

Scheme of the trigeminal nuclei — I = ophthalmic, II = maxillary, III = mandibular. — Adams & Victor's Principles of Neurology, 12e

Part 2: Three Peripheral Divisions & Their Distribution

Peripheral sensory distribution of CN V — Localization in Clinical Neurology, 8e

V1 — Ophthalmic Division

• Exits skull via superior orbital fissure
• Runs through the lateral wall of cavernous sinus
• Branches: frontal (supraorbital + supratrochlear), lacrimal, nasociliary
• Supplies:
  • Forehead and scalp up to lambdoidal suture
  • Upper eyelid, conjunctiva, cornea
  • Nose (dorsum, tip, nasal mucosa)
  • Frontal, sphenoidal, ethmoidal sinuses
  • Dura of anterior fossa, falx, tentorium (meningeal branch)
  • Mediates corneal reflex (afferent limb)

V2 — Maxillary Division

• Exits skull via foramen rotundum → sphenopalatine fossa → inferior orbital fissure → infraorbital foramen
• Branches: infraorbital, zygomatic, palatine, nasal, superior alveolar
• Supplies:
  • Cheek, lower eyelid, upper lip
  • Upper teeth and gums, hard palate
  • Maxillary sinus, nasal cavity floor
  • Nasopharynx, soft palate

V3 — Mandibular Division

• Mixed nerve (only division with motor fibers)
• Exits skull via foramen ovale
• Branches: auriculotemporal, inferior alveolar (mental nerve), lingual, buccal
• Supplies sensory to:
  • Lower lip, chin, lower jaw, lateral face anterior to ear
  • Lower teeth and gums
  • Anterior 2/3 of tongue (general sensation; taste = chorda tympani/VII)
  • Temporomandibular joint, external ear
• Motor to: masseter, temporalis, medial & lateral pterygoids, tensor tympani, tensor veli palatini, mylohyoid, anterior digastric

Important exception: The angle of the jaw (parotid area) is NOT supplied by CN V — it is supplied by the great auricular nerve (C2–C3). This helps distinguish peripheral CN V lesions from C2–C3 lesions.

Part 3: The Spinal Nucleus — Key to the Two Patterns

• Pars oralis (pons → inferior olive): intraoral/dental sensation
• Pars interpolaris (inferior olive → obex): pain from teeth
• Pars caudalis (obex → C2–C4): pain & temperature from face; continuous with dorsal horn

Part 4: The TWO Patterns of CN V Sensory Loss

Pattern 1 — "Peripheral" or Divisional Pattern (V1/V2/V3 Strips)

• Sensory loss follows the anatomical territory of one division:
  • V1 lesion → forehead, upper lid, cornea
  • V2 lesion → cheek, lower lid, upper lip
  • V3 lesion → lower lip, chin, jaw (sparing angle of jaw)
• All modalities (touch, pain, temperature) affected together
• Arranged in vertical/horizontal strips across the face
• Example causes: trigeminal neuralgia, skull base tumor, Gasserian ganglion lesion, cavernous sinus pathology, herpes zoster (dermatomal)

Pattern 2 — "Onion Skin" / Concentric Pattern (Intramedullary / Nuclear)

The Anatomy Behind It

"The midline facial areas (nose and mouth) are represented rostrally in the spinal nucleus, whereas the more lateral facial sensation fibers terminate in more caudal spinal nucleus regions." — Localization in Clinical Neurology, 8e

• Perioral region (lips, nose, central face) → represented in the rostral spinal nucleus (pons/upper medulla)
• Lateral face (cheeks, temple, ear region) → represented in the caudal spinal nucleus (lower medulla/C1–C2)

The Onion-Skin Pattern

• The innermost ring (perioral — lips, nose, central face) = most rostral nucleus
• The outermost ring (lateral face, temple, preauricular) = most caudal nucleus

Clinical implication

• Perioral numbness = rostral spinal nucleus lesion (high medulla / lower pons) — e.g., small Wallenberg infarct, syringobulbia
• Wide lateral face loss = more caudal involvement — e.g., upper cervical syrinx extending to C2

Pattern 3 — "Balaclava Helmet" Pattern

What it means neurologically

• Spared: Central face (perioral, perinasal) — i.e., areas supplied by C2 (great auricular nerve) that do NOT overlap with CN V
• Lost: Lateral face, scalp, and forehead — CN V territory
• More accurately: refers to sensory loss over the scalp and lateral face extending posteriorly, involving the posterior scalp which has cervical (C2, C3) overlap

In Clinical Use

1. Syringomyelia/Syringobulbia — as the syrinx ascends into the brainstem:
   • Initial caudal involvement of spinal nucleus → lateral face loss
   • Sparing of perioral (rostral nucleus) = balaclava-like distribution
2. Cervical cord lesions at C1–C2 — where C2 dorsal root inputs overlap with the caudal trigeminal nucleus:
   • Saddle-distribution loss at the crown of the scalp + lateral face
   • Perioral area (V3 rostral) spared
3. The "reverse" or "inverted onion skin" — with high cervical cord lesions, sensory loss is maximal laterally (ears, temples, scalp) and the inner perioral region is preserved — giving the appearance of the face wearing a balaclava (the fabric part covering the outside, the central holes remaining sensate).

Key Distinction

Summary Diagram (Conceptual)

FACE (viewed from front):

PERIPHERAL PATTERN:          ONION SKIN PATTERN:         BALACLAVA PATTERN:
  V1 │ V1 │ V1               ╔═══════════════╗             ░░░░░░░░░░░░░
  V2 │ V2 │ V2               ║  ╔═════════╗  ║             ░  ┌─────┐  ░
  V3 │ V3 │ V3               ║  ║ ╔═════╗ ║  ║             ░  │ OK  │  ░
 (vertical strips)           ║  ║ ║PERI-║ ║  ║             ░  │(C/F)│  ░
                             ║  ║ ║ORAL ║ ║  ║             ░  └─────┘  ░
                             ║  ║ ╚═════╝ ║  ║             ░░░░░░░░░░░░░
                             ║  ╚═════════╝  ║          (lateral+scalp lost)
                             ╚═══════════════╝

Reflex Summary

• Localization in Clinical Neurology, 8e — Sensory Portion, p. 741–742; Onion skin pattern, p. 742
• Adams & Victor's Principles of Neurology, 12e — Trigeminal nuclei, p. 1367
• Neuroanatomy through Clinical Cases, 3rd ed. — CN V nuclear lesions