Spontaneous inversion of nystagmus without a positional change in the horizontal canal variant of benign paroxysmal positional vertigo.

OBJECTIVE We investigated the neuro-otological findings, including nystagmus, and the clinical course of patients with the horizontal canal variant of benign paroxysmal positional vertigo (HC-BPPV), who showed spontaneous inversion of nystagmus without a positional change. Furthermore, we speculated on the possible mechanism of spontaneous inversion of nystagmus without a positional change. PATIENTS AND METHODS The characteristics of spontaneous inversion of positional nystagmus without a positional change were analyzed in 7 patients with HC-BPPV. RESULTS All patients were diagnosed as having HC-BPPV. During the positional test, the spontaneous inversion of nystagmus was observed in the same head position in all patients. Spontaneous inversion was observed on both sides in 5 patients, and only on 1 side in 2 patients. All patients presented with geotropic nystagmus in the first phase, and ageotropic nystagmus in the second phase. CONCLUSIONS The coexistence of cupulolithiasis and canalolithiasis appears to be a possible mechanism of the spontaneous inversion of positional nystagmus.