Dynamics of the vestibulo-ocular reflex in patients with the horizontal semicircular canal variant of benign paroxysmal positional vertigo.
OBJECTIVE
Two types of direction-changing positional nystagmus, the geotropic and apogeotropic variants, are observed in patients with the horizontal semicircular canal (HSCC) type of benign paroxysmal positional vertigo (H-BPPV). In this study, we assessed the dynamics of the vestibulo-ocular reflex (VOR) of the HSCC in patients with H-BPPV.


METHODS
Patients were rotated about the earth-vertical axis at frequencies of 0.1, 0.3, 0.5, 0.7 and 1.0 Hz with a maximum angular velocity of 50 degrees/s. Eye movements were recorded on a video imaging system using an infrared charge-coupled device (CCD) camera, and our new technique for analyzing the rotation vector of eye movements in three dimensions was used.


RESULTS
In the patients with geotropic positional nystagmus, there were no differences in VOR gain between rotation to the affected and unaffected sides at frequencies of 0.1-1.0 Hz. Although no differences in VOR gain at frequencies of 0.3-1.0 Hz were noticed in patients with apogeotropic positional nystagmus, the VOR gain at 0.1 Hz was significantly smaller on rotation to the affected compared to the unaffected side.


CONCLUSIONS
The results indicate that cupulolithiasis in the HSCC affected the dynamics of the HSCC-ocular reflex at 0.1 Hz, but not at higher frequencies, and that canalolithiasis in the HSCC does not change the VOR gain of the HSCC at any frequency. It is suggested that cupulolithiasis causes transient impairment of HSCC function by means of its mechanical restriction of movements of the cupula.
Sekine
Kazunori
K
Department of Otolaryngology, University of Tokushima School of Medicine, Tokushima, Japan. seky@clin.med.tokushima-u.ac.jp
Imai
Takao
T
Nakamae
Koji
K
Miura
Katsuyoshi
K
Fujioka
Hiromu
H
Takeda
Noriaki
N
D000328:Adult; D000368:Aged; D004584:Electronystagmography; D005260:Female; D018522:Gravitropism / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000503:physiopathology*; D009760:Nystagmus, Physiologic / Q000502:physiology*; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D012665:Semicircular Canals / Q000503:physiopathology*; D014717:Vertigo / Q000503:physiopathology*; D014724:Vestibular Function Tests / Q000379:methods