PART 5 — CRANIAL NERVES

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Study use: Rapid cranial-nerve anatomy, reflexes, skull exits, localization, common palsies, neuralgias, skull-base syndromes, brainstem syndromes, and emergency red flags. Management points are intentionally concise and should be interpreted with the full clinical context.

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Priority Guide: 🔴 Core / Must Know | 🟠 Important | 🟡 Additional

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🎯 High-Yield Overview

• Pupillary light reflex: II in → III out; corneal reflex: V1 in → VII out; gag reflex: IX in → X out.
• LR6 SO4, all the rest III is the central ocular-motor rule.
• Painful pupil-involving CN III palsy → think compressive aneurysm; CN VI palsy can occur with raised ICP.
• Trigeminal neuralgia: brief electric-shock facial pain with trigger zones → carbamazepine/oxcarbazepine.
• Bell palsy: ipsilateral upper + lower facial weakness; central facial weakness usually spares the forehead.
• Facial nerve traverses the parotid and is at surgical risk, but CN IX carries the parotid secretomotor pathway.
• Vestibular schwannoma: progressive unilateral SNHL + tinnitus; MRI IAC/CPA; bilateral tumors → NF2 spectrum.
• Jaw and LMN tongue deviate toward the lesion; uvula deviates away from a vagal lesion.
• Cavernous sinus: III, IV, V1, V2, VI + sympathetic fibers; jugular foramen: IX, X, XI.
• Wallenberg: nucleus ambiguus IX/X → dysphagia + hoarseness; medial medulla: XII palsy.

1. CRANIAL-NERVE MASTER MAP, EXITS, REFLEXES & EXAM

2. CN I & II — OLFACTION, VISION & PUPILLARY AFFERENT PATHWAY

3. CN III, IV & VI — OCULAR MOTOR PALSY + HORNER LOCALIZATION

4. CN V, TRIGEMINAL NEURALGIA & CAVERNOUS SINUS

5. CN VII — FACIAL NERVE, BELL PALSY, RAMSAY HUNT & PAROTID

6. CN VIII — VESTIBULOCOCHLEAR NERVE & VESTIBULAR SCHWANNOMA