Pseudo-spontaneous nystagmus in lateral semicircular canal benign paroxysmal positional vertigo: Correlation with bow and lean test in a pitch plane.

ObjectivesWe investigated the incidence and characteristics of pseudo-spontaneous nystagmus (PSN) in benign paroxysmal positional vertigo involving the lateral semicircular canal (LC-BPPV) and evaluated the correlation between PSN and the bow and lean test.MethodsWe examined nystagmus in the sitting position using video-oculography goggles in 131 LC-BPPV patients. The positioning test and bow and lean test were also performed. Patients were divided into canalolithiasis and cupulolithiasis groups according to the character of nystagmus. In each group, the incidence and direction of PSN, correlation with the bow and lean test, and treatment outcome were analyzed.ResultsPSN was observed in 25 cases (19.1%) in LC-BPPV patients, 7 of which were canalolithiasis and 18 of which were cupulolithiasis (p = 0.098). Of the 25 patients with PSN, 21 (84%) exhibited nystagmus consistent with the lean test whereas 4 (16%) exhibited nystagmus consistent with the bow test. In patients with PSN, nystagmus was observed in the bow and lean test in all cases (23/23), but in patients without PSN, no nystagmus was observed in 13 cases (13/87) in the bow and lean test (p = 0.048). The number of barbecue maneuvers performed until the end of treatment was 1.4 ± 0.7 in patients with PSN and 1.4 ± 0.9 in those without PSN (p = 0.976).ConclusionWe identified PSN in patients with LC-BPPV irrelevant of subtype. Moreover, all patients with PSN showed nystagmus in the bow and lean test. The direction of PSN was mostly consistent with that of the lean test (21/25, 84%). The presence of PSN was not related to the treatment outcome in this study.