A patient with Meniere's disease undergoes a glycerol test. A positive result is defined as improvement in pure-tone thresholds by at least 15 dB at two or more frequencies. This test works by which mechanism?
- A Osmotic dehydration of the endolymphatic space ✓
- B Increasing endolymphatic absorption
- C Reducing cochlear blood flow
- D Stabilizing the basilar membrane
Correct answer: A. Osmotic dehydration of the endolymphatic space
Explanation
Glycerol is an osmotic agent that draws fluid out of the endolymphatic space, reducing endolymphatic pressure and hydrops. This temporarily improves cochlear function, measurable as improved hearing thresholds. The test confirms reversible endolymphatic hydrops. It does not primarily increase absorption, reduce blood flow, or stabilize the basilar membrane.
Reference: Cummings Otolaryngology, 7th ed.
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