A patient presents with acute onset facial weakness, affecting both the forehead and lower face on one side. She is unable to close her eye or wrinkle her forehead on the affected side. This presentation is most consistent with a lesion of which cranial nerve?

The correct answer to the question "A patient presents with acute onset facial weakness, affecting both the forehead and lower face on one side. She is unable to close her eye or wrinkle her forehead on the affected side. This presentation is most consistent with a lesion of which cranial nerve?" is Option B: Facial nerve (CN VII).

The other options — A) Trigeminal nerve (CN V), C) Vagus nerve (CN X), D) Hypoglossal nerve (CN XII) — are incorrect for this USMLE Exam Prep question. As explained above: Unilateral facial weakness affecting both upper and lower face (inability to wrinkle forehead or close eye) indicates a peripheral lesion of the facial nerve (CN VII), such as in Bell's palsy. A cent…