In the Dix-Hallpike test for posterior canal BPPV (PC-BPPV), the characteristic nystagmus evoked is:

• A Purely horizontal, beating toward the tested (lower) ear, immediate onset, persistent
• B Downbeat torsional, beats away from the tested ear, no latency, non-fatigable
• C Upbeat torsional, with fast phase rotating toward the tested (lower) ear, latency 2–10 sec, fatigable, duration <60 sec ✓
• D Purely vertical downbeat, direction-changing, persistent regardless of head position

Explanation

Posterior canal canalolithiasis (most common BPPV) produces characteristic upbeat-torsional nystagmus on Dix-Hallpike: fast phase is upbeat (toward ceiling) with a torsional component rotating toward the affected (lower) ear. Key features: latency of 2–10 seconds (time for debris to shift), duration <60 seconds, and fatigability with repeated testing. Purely horizontal nystagmus suggests horizontal canal BPPV (diagnosed by roll test). Persistent direction-changing or purely downbeat nystagmus is a red flag for central pathology.

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

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Written and medically reviewed by the StethoPrep medical team.