A 68-year-old presents with episodic vertigo triggered by head position changes. Dix-Hallpike test shows a latency of 2–3 seconds before onset of upbeat-torsional nystagmus beating toward the lower ear, lasting 15–30 seconds, and fatiguing with repeated testing. This pattern localizes the pathology to:
- A Left anterior (superior) semicircular canal
- B Right posterior semicircular canal (with Dix-Hallpike right positive) ✓
- C Horizontal semicircular canal
- D Vestibular nerve
Explanation
The described Dix-Hallpike findings — latency of 2–3 seconds, upbeat-torsional nystagmus beating toward the undermost (right) ear, short duration (15–30 s), and fatigability — are the classic hallmarks of canalith repositioning pathology in the posterior semicircular canal (PSC-BPPV), specifically the right PSC when right Dix-Hallpike is positive. The posterior canal is the most commonly affected canal (80–90% of BPPV cases) because of its dependent anatomical position. Horizontal canal BPPV produces direction-changing geotropic or apogeotropic nystagmus in supine roll testing.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.