Clinical Correlations in Neuroanatomy

Cerebral Vascular Syndromes - Stroke Strikes

Homunculus representation is key for localization. All deficits contralateral unless specified.

⭐ Gerstmann syndrome (acalculia, agraphia, finger agnosia, right-left disorientation) can occur with dominant parietal lobe lesions, often involving the angular gyrus supplied by MCA territory.

Brainstem Syndromes - Brainstem Blues

📌 Rule of 4s: For lesion localization.

• Midbrain Syndromes:
  • Weber's: Ipsilateral CN III palsy; contralateral hemiplegia (corticospinal tract).
  • Benedikt's: Ipsilateral CN III palsy; contralateral ataxia & tremor (red nucleus, medial lemniscus).
  • Parinaud's (Dorsal Midbrain): Vertical gaze palsy (esp. upward), light-near dissociation, convergence-retraction nystagmus.
• Pontine Syndromes:
  • Millard-Gubler: Ipsilateral CN VI & CN VII palsy; contralateral hemiplegia (corticospinal tract).
• Medullary Syndromes:
  • Wallenberg's (Lateral Medullary): Ipsilateral: ataxia, Horner's syndrome, loss of facial pain/temp (CN V), dysphagia, hoarseness (CN IX, X). Contralateral: loss of body pain/temp (spinothalamic tract).

⭐ Wallenberg's syndrome (PICA occlusion) classically spares the corticospinal tract, hence no contralateral hemiplegia is a key distinguishing feature.

Cranial Nerve Lesions - Nerve Wrecks

• CN III (Oculomotor): Eye "down & out", ptosis, mydriasis.
• CN IV (Trochlear): Vertical diplopia (worse looking down/inward), head tilt away from lesion.
• CN VI (Abducens): Horizontal diplopia, failed eye abduction (lateral gaze palsy).
  • 📌 Mnemonic (extraocular muscles): $LR_6SO_4R_3$.
• CN VII (Facial) Palsy:
  • LMN (e.g., Bell's Palsy): Ipsilateral entire half of face paralyzed.
  • UMN: Contralateral lower face paralysis; forehead spared.
• Other Key Lesions:
  • CN V: Trigeminal neuralgia (severe, lancinating facial pain).
  • CN IX/X: Bulbar signs (dysphagia, dysarthria, absent gag reflex, uvula deviates away from lesion).
  • CN XII: Tongue deviates towards side of LMN lesion on protrusion.
• Localizing Value: Patterns of combined CN palsies help pinpoint lesion site (e.g., cavernous sinus, cerebellopontine angle).

⭐ Pupil-sparing CN III palsy often suggests ischemic microvascular damage, whereas pupil involvement (mydriasis) typically indicates a compressive lesion, such as a posterior communicating artery (PCOM) aneurysm, requiring urgent investigation.

Spinal Cord Syndromes - Spinal Shockers

• Brown-Séquard Syndrome (Hemisection):
  • Ipsilateral: UMN paralysis, loss of proprioception/vibration below lesion.
  • Contralateral: Loss of pain/temperature sensation, 2-3 segments below lesion.
• Anterior Cord Syndrome (ASA Occlusion):
  • Bilateral loss: Motor function (corticospinal), pain/temperature (spinothalamic) below lesion.
  • Preserved: Proprioception/vibration (dorsal columns).
• Central Cord Syndrome (Hyperextension Injury, common in elderly):
  • Motor impairment: Upper limbs > lower limbs (sacral sparing often present).
  • Sensory loss variable; often pain/temperature affected at level of lesion (cape-like distribution).
• Posterior Cord Syndrome (e.g., Tabes Dorsalis, Vitamin B12 deficiency):
  • Bilateral loss of proprioception, vibration, and discriminative touch below lesion.
  • Motor function, pain/temperature preserved.
• Sacral Sparing: Indicates incomplete lesion; peripheral fibers of spinothalamic tract (sacral) are spared. Common in central cord syndrome; good prognostic sign.

⭐ The anterior spinal artery (ASA) supplies the anterior two-thirds of the spinal cord, including the corticospinal and spinothalamic tracts. Occlusion leads to Anterior Cord Syndrome. 📌 Mnemonic: "A" for Anterior, "A" for Artery, "A"ll motor and pain/temp gone (mostly).

High‑Yield Points - ⚡ Biggest Takeaways

• Broca's area lesion: expressive aphasia; Wernicke's area lesion: receptive aphasia.
• Subarachnoid hemorrhage: "worst headache of life", often ruptured berry aneurysm.
• Brown-Séquard syndrome: ipsilateral motor/proprioception loss, contralateral pain/temperature loss.
• Parkinson's disease: dopamine depletion in substantia nigra causes TRAP symptoms.
• Horner's syndrome: ptosis, miosis, anhidrosis due to sympathetic chain lesion.
• Bell's palsy (LMN CN VII): ipsilateral facial paralysis; UMN lesion spares forehead.
• Optic chiasm lesion: bitemporal hemianopia.