Recovery of positional nystagmus after benign paroxysmal positional vertigo fatigue.

Abstract

In benign paroxysmal positional vertigo (BPPV), positional nystagmus is generally weaker when the Dix-Hallpike test is repeated. This phenomenon is known as BPPV fatigue. The positional nystagmus induced by the Dix-Hallpike test can be observed again when time has passed. There has been no study regarding the length of time required to recover the positional nystagmus. The purpose of this study was to examine whether positional nystagmus recovers within 30min after the disappearance of the nystagmus by BPPV fatigue. This was a prospective observational study. Twenty patients with posterior canal type of BPPV (canalolithiasis of the posterior canal) were included. Dix-Hallpike tests were performed three times for each patient. A second Dix-Hallpike test was performed immediately after the first Dix-Hallpike test. A third Dix-Hallpike test was performed 30min after the second Dix-Hallpike test. We recorded positional nystagmus induced by the Dix-Hallpike tests and analyzed maximum slow-phase eye velocity (SPEV) of the positional nystagmus. The average maximum SPEV of positional nystagmus induced by the second Dix-Hallpike test (4.8°/s) was statistically lower than that induced by the first Dix-Hallpike test (48.0°/s); this decrease was caused by BPPV fatigue. There was no statistical difference between average maximum SPEV of positional nystagmus induced by the first Dix-Hallpike test and that induced by the third Dix-Hallpike test (41.6°/s); this indicates that the effect of BPPV fatigue disappeared. The effect of BPPV fatigue disappears within 30min. A second Dix-Hallpike test should be performed at least 30min after the first.