Anatomy & Histology · patient case question
Which cranial nerve is affected?
Patient case: Unilateral Facial Weakness
demo: 49-year-old male
chief: “I woke up and the right side of my face was drooping.”
history: Recent upper respiratory infection. No prior neurologic events.
meds: None
findings: Drooping of the right corner of the mouth with inability to purse the lips or retain fluid. Forehead wrinkling and eye closure are preserved on the affected side. No sensory deficit. Nerve pathway illustrated below.
Show answer and explanation
Correct answer: D. Facial nerve (CN VII)
- A. The trigeminal nerve is sensory to the face and motor to the muscles of mastication; a lesion would produce numbness, which is absent here.
- B. CN XII moves the tongue; a lesion causes tongue deviation toward the affected side.
- C. CN IX contributes to swallowing and taste from the posterior third of the tongue, not facial expression.
- D. Correct. CN VII supplies all the muscles of facial expression. The absence of any sensory loss confirms the trigeminal nerve is intact.
Note: Preserved forehead movement and eye closure point to a central (upper motor neuron) lesion — the forehead has bilateral cortical input. Bell's palsy, a lower motor neuron lesion, paralyzes the whole half of the face including the forehead. Preserved eye closure is a red flag for stroke and warrants urgent medical referral.
Practice Anatomy & Histology questions Anatomy & Histology study notes