🏥 USMLE Exam Prep

Damage to the uncal region of the temporal lobe, often due to herniation, can compress which cranial nerve, leading to ipsilateral fixed and dilated pupil and 'down and out' gaze?

A Optic nerve (CN II)
B Oculomotor nerve (CN III)
C Trochlear nerve (CN IV)
D Abducens nerve (CN VI)

✓ Correct Answer: Option B

Uncal herniation compresses the ipsilateral oculomotor nerve (CN III). This typically affects the superficial parasympathetic fibers first (causing pupillary dilation) and then motor fibers (resulting in a 'down and out' gaze).

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