Which single finding on positional testing best distinguishes cupulolithiasis from canalithiasis as the mechanism of BPPV?

• A Latency of more than 5 seconds before onset of nystagmus
• B Presence of severe nausea accompanying the nystagmus
• C Nystagmus that persists as long as the provocative head position is maintained, without fatiguing ✓
• D Reversal of nystagmus direction when returning to the sitting position

Explanation

In cupulolithiasis, otoconia are deposited directly on the cupula of the affected canal, making it density abnormal and deflected throughout the entire time the head stays in the provocative position. The nystagmus therefore persists and does not fatigue. In canalithiasis, free-floating otoconia keep moving briefly, so nystagmus is transient, typically lasting less than 60 seconds. Latency, nausea, and transient reversal on sitting occur in both variants.

Reference: Cummings Otolaryngology: Head and Neck Surgery, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.