A 38-year-old woman describes vertigo triggered by loud noises and by straining during bowel movements, along with hearing her own voice and pulse loudly in the affected ear. Audiometry shows a low-frequency air-bone gap with normal acoustic reflexes and a normal tympanic membrane. Which investigation will confirm the diagnosis?

• A Stapedial reflex decay audiometry
• B MRI of the internal auditory canals with contrast
• C High-resolution CT of the temporal bone ✓
• D Exploratory middle ear exploration

Explanation

Sound- and pressure-induced vertigo (Tullio and Hennebert phenomena) with autophony, a low-frequency air-bone gap despite normal acoustic reflexes, and an intact tympanic membrane defines superior semicircular canal dehiscence syndrome, a third-window lesion. High-resolution CT of the temporal bone with reformats in the plane of the superior canal demonstrates the bony dehiscence over the arcuate eminence and is diagnostic. MRI evaluates retrocochlear masses but does not reliably show thin bony defects. Reflex decay and surgical exploration are unnecessary once imaging confirms the defect.

Reference: Cummings Otolaryngology: Head and Neck Surgery, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.