[Early saturated form of slow phase eye velocity in optokinetic nystagmus in dizzy patients].
The peculiar form of the optokinetic nystagmus (OKN) in the electro-oculogram (EOG) was studied in 26 dizzy patients. The slow phase velocity is saturated below 60 degrees (53.7 +/- 6.5) and keeps steady state level in response to higher stimulus velocities, while the peak velocity rises up to 94.6 +/- 16.5 degrees in healthy subjects. In contrast, the frequency of slow phase nystagmus (200.3 +/- 22.6) ranges within normal limits (218.0 +/- 23.4). These characteristics were significant in the student t-test. In Cohen and Raphan's model, slow phase of OKN is supposed to be composed of two components: one is the direct pathway which is responsible for a initial rapid rise. Another is the indirect pathway which contains the velocity storage integrator and is responsible for a slower rise to a steady state level. According to Waespe et al (1983), the initial rapid rise was severely attenuated and the peak velocity of OKN declined to the preoperated saturation level of OKAN after flocculectomy in monkeys. These findings were remarkably coincident with the present study. Additionally, in 5 cases, neuroradiological studies revealed small lesions in the cerebellum. Thus, it is concluded such form of OKN is suggested to be the small lesion in the cerebellum, especially flocculus.
Yokota
J
J
Department of Neurology, Amakusa Hospital, Saitama, Japan.
D000221:Adaptation, Ocular; D001933:Brain Stem / Q000503:physiopathology; D002531:Cerebellum / Q000503:physiopathology; D004244:Dizziness / Q000503:physiopathology*; D004585:Electrooculography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017120:Nystagmus, Optokinetic; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*