Why Continuous Nystagmus Monitoring Matters During Treatment of Posterior Canal BPPV?

A 71-year-old woman presented on March 18, 2025, with a 2-day history of vertigo triggered by head position changes relative to gravity, such as rising from the supine position or transitioning to left lateral recumbency. The left Dix-Hallpike test (DHT) elicited left torsional upbeating positional nystagmus lasting less than 60 seconds, suggesting periampullary left posterior semicircular canalolithiasis. The left Epley maneuver was performed. On re-evaluation 1 hour later, spontaneous right-beating horizontal nystagmus was observed, indicating canalith jam. Therapeutic head shaking for approximately 30 seconds reversed the spontaneous nystagmus to left-beating. Subsequently, a supine roll test elicited geotropic horizontal positional nystagmus on lateral rolls to the left and right (stronger on leftward roll than rightward), indicating left horizontal semicircular canalolithiasis in the non-ampullary arm, which was treated with the Gufoni maneuver. Twenty-four hours later, no spontaneous nystagmus was elicited. The left DHT then elicited slow crescendo-decrescendo downbeating nystagmus with a right torsional component, indicating a switch to non-ampullary arm left posterior semicircular canalolithiasis. A mastoid-augmented demi-Semont maneuver was performed several times, followed by 1 hour of forced prolonged positioning at 45 degrees to the patient's right. The left DHT was negative after 4 hours, and the patient was asymptomatic. Diagnosis: 1. Left posterior semicircular canal benign paroxysmal positional vertigo (BPPV) due to periampullary canalolithiasis. 2. Treatment-related complications involving left horizontal canal switch with canalith jam and ipsilateral canal switch to left non-ampullary arm posterior semicircular canalolithiasis.