In BPPV (benign paroxysmal positional vertigo), the most common variant involves the posterior semicircular canal with canalolithiasis. The Dix-Hallpike manoeuvre triggers a characteristic nystagmus. Which of the following correctly describes the nystagmus direction in posterior canal canalolithiasis (right posterior canal BPPV)?

• A Horizontal nystagmus beating towards the affected (right) ear, sustained throughout the test
• B Torsional nystagmus with the upper pole of the eye beating towards the floor (right-beating), with a brief latency and fatigability ✓
• C Purely vertical downbeat nystagmus indicating central BPPV
• D Torsional nystagmus with the upper pole of the eye beating away from the floor, fatigable but without latency

Explanation

In right posterior canal canalolithiasis with positive right Dix-Hallpike: the characteristic nystagmus has (1) a latency of 2–20 seconds before onset, (2) upbeat-torsional character with the upper pole of the eye beating toward the lowermost (affected right) ear/floor, (3) duration < 60 seconds, and (4) fatigability with repeated testing. This occurs because debris moving away from the crista of the posterior canal (utricle-directed flow) inhibits the posterior canal and activates it via the excitatory projection to ipsilateral inferior oblique and contralateral superior rectus. Purely vertical or non-fatigable nystagmus suggests a central cause.

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

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Written and medically reviewed by the StethoPrep medical team.