Neuroanatomy USMLE Step 1 Practice Question
A 64-year-old hypertensive diabetic man presents with acute onset diplopia, right ptosis, and right medial rectus weakness. Pupillary responses remain intact. Vital signs show BP 158/92 mmHg, HR 88/min, RR 16/min, temp 37.2°C, SpO2 98% on room air. MRI reveals a small acute infarct in the right midbrain with restricted diffusion on DWI. Extraocular movements are otherwise preserved. Which cranial nerve is most likely affected?
Answer choices
- ATrochlear nerve (CN IV)
- BVestibulocochlear nerve (CN VIII)
- COculomotor nerve (CN III)Correct answer
- DFacial nerve (CN VII)
- EAbducens nerve (CN VI)
- FAccessory nerve (CN XI)
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