Short-term central adaptation in benign positional paroxysmal vertigo

Abstract

To elucidate the cause, associated factors and clinical implications of the spontaneous reversed nystagmus (SRN) in benign paroxysmal positional vertigo (BPPV), we analyzed the nystagmus in posterior canal (PC) and horizontal canal (HC) BPPV. From 2017 to 2018, 182 consecutive patients with PC (n = 119) and HC (n = 63) BPPV (men = 64, mean age ± SD = 63.9 ± 13.9) were prospectively recruited. The SRN was defined as the following direction-changing nystagmus after the initial positional nystagmus without change of a head position during Dix-Hallpike or head-roll test. The SRN was observed in 56 (56/119, 47.1%) in PC and 43 (43/63, 68.3%) in HC BPPV. The maxSPV of initial positional nystagmus in PC-BPPV with SRN was greater than that without SRN (56.2 ± 39.3°/sec vs. 40.2 ± 34.4°/sec). The duration and Tc of nystagmus of PC-BPPV with SRN were shorter than these without SRN (p = 0.016 and 0.034). In HC-BPPV, the maxSPV of ipsilesional geotropic nystagmus was also greater on the group with SRN than those without SRN (114.3 ± 56.8°/sec vs. 59.3 ± 41.8°/sec, p = 0.003). The estimated cutoff value of maxSPV for spontaneous reversal is 85.5°/sec in PC BPPV and 56.7°/sec in HC BPPV. The SRN did not affect to the treatment outcomes in PC- and HC-BPPV. The SRN is common in both PC- and HC-BPPV. The velocity storage system may contribute these short-term adaptive responses with telescopic strategy to the acute abnormal vestibular asymmetry.