Benign paroxysmal positional vertigo (BPPV) most commonly involves the posterior semicircular canal. In canalithiasis of the posterior canal, the Dix-Hallpike test produces a characteristic nystagmus. Which of the following ACCURATELY describes the expected nystagmus in right posterior canal canalithiasis on right Dix-Hallpike?

• A Horizontal nystagmus, geotropic (toward ground), immediate onset, no latency, no fatigue
• B Downbeat nystagmus, purely vertical, immediate onset, non-fatigable — characteristic of central BPPV
• C Upbeat-torsional nystagmus with upper pole of eye beating toward the undermost (right) ear, latency 2–40 sec, duration < 1 min, fatigable ✓
• D Horizontal nystagmus, apogeotropic (away from ground), latency 5–20 sec, duration < 1 min

Explanation

In right posterior canal canalithiasis, the Dix-Hallpike test with the right ear down causes otoconia to fall toward the cupula in the posterior canal, producing an upbeat-torsional nystagmus where the upper pole beats toward the undermost (right) ear (geotropic torsional component). Key features: latency 2–40 seconds (free-floating debris delay), duration < 1 minute (debris settles), and fatigability with repeated testing. Purely horizontal nystagmus suggests horizontal canal BPPV; non-fatigable or downbeat nystagmus suggests a central lesion (cerebellum/brainstem).

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

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Written and medically reviewed by the StethoPrep medical team.