A 32-year-old man with acute left Bell palsy complains that sounds seem unpleasantly loud in his left ear since the weakness began. The symptom is explained by involvement of which branch of the facial nerve?

• A Chorda tympani
• B Nerve to stapedius ✓
• C Greater petrosal nerve
• D Communicating branch to the lesser petrosal nerve

Explanation

Stapedius damps movements of the stapes and protects the inner ear from loud sound. Paralysis of the muscle removes this damping, producing hyperacusis on the affected side. The nerve to stapedius arises from the facial nerve near the second genu at the level of the pyramidal eminence. Chorda tympani conveys taste and submandibular secretomotor fibers, while the greater petrosal nerve mediates lacrimation, neither of which affects sound damping.

Reference: BD Chaurasia's Human Anatomy, Volume 3, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.