Facial Nerve LMN Palsy — MFDS Part 1 MCQ

Instant feedback + full explanation. One question, done properly.

EasyAnatomy (Head & Neck)Facial Nerve LMN PalsyMFDS Part 1

A patient has weakness of the entire left side of the face. They cannot wrinkle the left side of the forehead, close the left eye tightly or elevate the left corner of the mouth. Which cranial nerve has been affected?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Facial nerve (VII)

The affected nerve is the facial nerve (cranial nerve VII). Weakness of the ipsilateral forehead, eye closure and corner of the mouth indicates paralysis of the entire set of muscles of facial expression, as occurs with a lower motor neurone facial nerve lesion. Orbicularis oculi weakness prevents tight eye closure, while weakness of the perioral facial muscles produces mouth drooping. The trigeminal nerve supplies facial sensation and muscles of mastication; the hypoglossal nerve supplies the tongue; the glossopharyngeal nerve contributes to pharyngeal and posterior tongue functions; and the abducens nerve supplies the lateral rectus muscle. None accounts for combined forehead, eyelid and mouth weakness.

Reference: University Hospitals of Leicester NHS Trust. Treating facial weakness affecting your eye caused by Bell’s palsy. Last reviewed December 2025. https://yourhealth.leicestershospitals.nhs.uk/library/musculoskeletal-specialist-surgery-mss/ophthalmology/1705-treating-facial-weakness-affecting-your-eye-caused-by-bell-s-palsy/file