the study was designed for the evaluation of diagnostic usefulness of standard electro-oculography (EOG) battery in differentiating the vertigo of central origin from that of peripheral one. Twelve patients of definite posterior fossa lesion
proved
by
MRI or CT scan were selected as a central group and fourteen patients of peripheral vestibulopathy as a peripheral group. Using our laboratory standard methods of EOG battery, age-matched normal values of bithermal caloric responses (fixation
suppression, vestibular paresis, and directional preponderance) and the gains of pursuit and optokinetic nystagmus were obtained.
Abnormal vestibular paresis was found in 12 patients of the peripheral group, but in only one patient of the central. Directional preponderance did not show significant difference between the peripheral and central group(p<0.01).
In peripheral group, the fixation suppression index (percent change in slow-phase velocity with visual fixation during the period of maximum intensity of caloric nystagmus) was 56.8±9.0%, which was no significant difference compared with the
normal
control group(59.4±8.3t, p>0.01±. However, failure of fixation suppression was noted in eleven patients of central group and its mean value of 92.6±7.35, which was significant statistical difference compared with peripheral and control group
(p<0.01
respectively). Defective suppression of caloric nystagmus was more remarkable when then the direction of caloric nystagmus was induced toward the lesion site. Such findings were demonstrated in six patients of eight patients with definite
unilateral
cerebellar hemispheric lesions.
In addition, the gains of pursuit and optokinetic nystagmus were significantly reduced in the patients showing defctive fixation suppeession compared with whom showed normal pattern of fixation suppression (p<0.01).
Therefore, fixation suppression, vestibular paresis, and the gains of pursuit and optokinetic nystagmus would be useful diagnostic paremeters in differntiaging the vertigo of central origin from that of the peripheral.
|