A 40-year-old woman with episodic vertigo, fluctuating low-frequency sensorineural hearing loss and aural fullness shows a Short Increment Sensitivity Index (SISI) score of 85% and a narrowed dynamic range on uncomfortable loudness level testing. These findings indicate which underlying phenomenon?

• A Diplacusis of a labyrinthine fistula
• B Tone decay typical of an eighth nerve lesion
• C Abnormal auditory adaptation of a central lesion
• D Loudness recruitment typical of a cochlear lesion ✓

Explanation

Recruitment is abnormally rapid growth of loudness once threshold is exceeded, producing a narrow dynamic range between threshold and discomfort. It reflects outer hair cell dysfunction and is characteristic of cochlear disorders such as Meniere disease. D SISI score above 70% supports a cochlear site of lesion. Tone decay and poor adaptation point to a retrocochlear lesion such as vestibular schwannoma, which is the opposite pattern.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.