[Analysis of repositioning nystagmus in patients with posterior canal benign paroxysmal positional vertigo].

To conclude the four types of nystagmus in the final position during canalith repositioning procedure (CRP) for posterior canal benign paroxysmal positional vertigo (PC-BPPV), and predict the outcome of CRP therapy. Nystagmus were recorded by an infrared charge-coupled devicecamera when underwent CRP therapy, which observed in the final position and concluded into four types. Two hundred and twenty-three patients were included in our research and the results as follow. ①The nystagmus replicates the initial nystagmus during the Hallpike maneuver, which suggests therapeutic outcome,128 cases in total (57.4%). ②The direction of vertical component is composite while the rotary component is the same, also deeming a successful trial, 35 cases (15.7%). ③The direction of both vertical component and rotary component isreverse to the initial, which indicates a poor response, 36 cases (16.1%). ④Twenty-four cases (10.8%) showed no certain nystagmus but exhibit horizontal nystagmus in roll-test, denoting that the otolith moves to the lateral semicircular. At this appointment, the horizontal nystagmus can resolute after several times of barbecue maneuver. There is a significant difference of the one-time success rate (²=46.198, <0.01) and the mean treatment times (=10.048, <0.01) between cupulolithiasis and canalolithiasis PC-BPPV. Different nystagmus in the final position of CRP maneuver is important in predicting the repositioning outcome. The one-time success rate of canalolithiasis is better than cupulolithiasis.