Objective characteristics of nystagmus in patients with posterior semicircular canal benign paroxysmal positional vertigo

Abstract

Objective: To analyze and discuss the parameters and clinical significance of nystagmus in patients with benign positional paroxysmal vertigo (BPPV) of posterior semicircular canal. Methods: The subjects of the study were 564 BPPV patients diagnosed with posterior semicircular canal canalithis (PSC-can) from January 2016 to July 2017 in Tianjin No.1 Central Hospital, including 186 males and 378 females, with a median age of 57 years. The induced nystagmus in Dix-Hallpike test was recorded by video nystagmuo graph(VNG), and the direction, latency, duration time and intensity characteristics of nystagmus were compared with the position of hanging and sitting.SPSS17.0 software was used for statistical analysis. Results: Vertical torsional nystagmus was both induced with the position of hanging and sitting during Dix-Hallpike test. The vertical direction of the induced nystagmus was upward and downward respectively. The latency, duration time and intensity of lesion side were L(2.65±1.92; 1.44±1.24), D(14.90±10.46; 15.28±8.06), and P(29.75±21.26; 14.08±9.48). The latency and intensity in hanging position were higher than those of sitting. The intensity rate was about 2∶1, with statistically significant difference (t=13.831, and 17.296, P all<0.01). The direction of the induced nystagmus was opposite to turning in HSC-Can BPPV. The intensity turning to normal side was larger than lesion side obviously. The intensity rate was about 2∶1, the difference was statistically significant (t=17.296, P<0.01). There was no statistical difference of nystagmus during time between the two positions(t=-0.735, P>0.05). Conclusions: The nystagmus intensity rate in Dix-Hallpike test between hanging and sitting position of lesion side in PSC-Can is 2∶1, which conforms to the Ewald's law. The direction, latency and intensity of nystagmus can be used as a reference index for the localization diagnosis of PSC-Canotolith.