A patient presents with sudden unilateral facial drooping. On examination, the patient IS ABLE to close the eye on the affected side. What does this finding indicate?

Correct answer: C. Upper motor neuron (UMN) lesion — the forehead and eye closure are partially spared

• A. Bilateral facial nerve involvement would cause bilateral drooping — the presentation is unilateral.
• B. Bell's palsy is an LMN lesion where the patient CANNOT close the eye on the affected side — the entire ipsilateral face including the eye is involved. The question states the patient CAN close the eye, ruling out LMN lesion.
• C. CORRECT. The ability to CLOSE THE EYE is the key differentiating finding. The UPPER face (forehead and orbicularis oculi for eye closure) receives BILATERAL cortical input — so a UNILATERAL UMN lesion (stroke, brain tumor) spares eye closure because the contralateral hemisphere compensates. In LOWER motor neuron (LMN) lesions (Bell's palsy, VZV Ramsay Hunt), the peripheral CN VII is damaged and the patient CANNOT close the eye. If the patient CAN close the eye → UMN (central/stroke). If CANNOT close the eye → LMN (peripheral/Bell's).
• D. The trigeminal nerve provides facial sensation, not motor control of facial expression. CN V lesions cause loss of sensation, not facial drooping.