A patient presents with episodic vertigo lasting seconds, triggered by lying down and rolling to the right. Dix-Hallpike test on the right produces upbeat-torsional geotropic nystagmus with a latency of 5 seconds that fatigues after 30 seconds. The canal most likely involved and the mechanism are:

• A Right horizontal canal; cupulolithiasis
• B Left anterior canal; cupulolithiasis
• C Right posterior canal; canalolithiasis ✓
• D Right superior canal; canalolithiasis

Explanation

The Dix-Hallpike test on the right producing upbeat-torsional nystagmus (fast phase upward with torsional component toward the lower — right — ear) with a 2–20 second latency and fatigability over repeated testing is the classic presentation of right posterior canal BPPV due to canalolithiasis (free-floating otolith debris in the canal lumen). Canalolithiasis is more common than cupulolithiasis and explains the latency (time for debris to reach the ampulla) and fatigability (debris disperses with repeated testing). Cupulolithiasis produces persistent non-fatigable nystagmus.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.