The glycerol (dehydration) test performed in suspected Meniere's disease is interpreted as positive when:

• A Caloric response shows unilateral weakness greater than 25 percent
• B Fistula test becomes positive after glycerol administration
• C Electrocochleography shows an SP/AP ratio falling below 0.15
• D Pure tone audiometry shows improvement in hearing thresholds two to three hours after oral glycerol ingestion ✓

Explanation

Oral glycerol, roughly 1.5 ml/kg given with fruit juice, acts as an osmotic agent that temporarily reduces endolymphatic hydrops. A positive test is defined by measurable improvement in pure tone thresholds, especially low frequencies, two to three hours later, confirming hydrops as the cause of the fluctuating hearing loss. Unilateral weakness on calorics reflects chronic vestibular damage and is not the endpoint of this test. The SP/AP ratio rises, not falls, in hydrops.

Reference: Diseases of Ear, Nose and Throat (Dhingra), 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.