A 35-year-old woman with unilateral hearing loss, tinnitus and episodic vertigo undergoes a Short Increment Sensitivity Index (SISI) test. She scores 85% at 1000 Hz. This result localizes the lesion to the:

• A Cochlea (outer hair cell disease) ✓
• B Internal auditory meatus
• C Ossicular chain
• D Cerebral auditory cortex

Explanation

SISI measures the ability to detect 1 dB intensity increments superimposed on a continuous tone. A score above about 70% is positive and indicates recruitment, the abnormally rapid growth of loudness typical of cochlear (outer hair cell) lesions such as Meniere disease. Retrocochlear lesions like vestibular schwannoma produce poor increment detection and low scores, killing distractor B.

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

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Written and medically reviewed by the StethoPrep medical team.