A 32-year-old man develops a left lower motor neuron facial palsy. He complains that ordinary sounds appear unpleasantly loud and distorted in the left ear. This symptom indicates that the lesion lies:

• A Distal to the origin of the chorda tympani
• B Proximal to the origin of the nerve to stapedius ✓
• C At the stylomastoid foramen
• D In the tympanic segment distal to the geniculate ganglion

Explanation

Hyperacusis results from paralysis of the stapedius muscle, which normally damps stapes movement and protects against loud sound. The nerve to stapedius arises from the descending (mastoid) segment of the facial nerve, so a lesion proximal to its origin abolishes the stapedial reflex and produces hyperacusis. A lesion at the stylomastoid foramen or distal to the chorda tympani spares the stapedius branch entirely, so hyperacusis cannot occur with those lesions.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.