3-DIMENSIONAL ANALYSIS OF SPONTANEOUS NYSTAGMUS IN PERIPHERAL VESTIBULAR LESIONS

The direction of spontaneous nystagmus was recorded in three dimension s with scleral dual search coils in three patients after vestibular ne urectomy and in seven patients with vestibular neuritis. The rotation vectors of the spontaneous nystagmus clustered along the sensitivity v ector of the lateral semicircular canal (SCC). The direction of the sp ontaneous nystagmus after resection of the whole eighth nerve was not different from that after resection of only the superior branch of the vestibular nerve. Deviations from this direction were observed only a fter resection of the inferior vestibular nerve and in one patient wit h vestibular neuritis. The absence of nystagmus components in directio n of the vertical SCC reflects an anisotropy of oculomotor efferents o f the vestibule-ocular reflex are rather than a lesion limited to the lateral SCC afferents. Therefore, the three-dimensional analysis of sp ontaneous nystagmus does not permit accurate localization of a periphe ral vestibular lesion.