抄録
Spontaneous nystagmus was examined in 38 patients with lateral medullary infarct syndrome. Although horizontal nystagmus is commonly observed in this syndrome, the direction of nystagmus is not always consistent with the side of the lesion. Horizontal nystagmus beats away from the side of infarction in 79% of patients. Meanwhile, torsional nystagmus which is characteristic of this syndrome beats away from the side of infarction (ipsilateral slow phase beats) in all cases. In an investigation of the mechanism of torsional nystagmus, patients were assigned to one of two groups: typical form (lesions of the descending root of the trigeminal nerve) and ventral form (no or incomplete involvement of the root of the trigeminal nerve). Although horizontal nystagmus occurred in both the typical and the ventral form, torsional nystagmus was observed only in the typical form. Furthermore, cerebellar signs were more common within patients with torsional nystagmus than in those of horizontal nystagmus. There-fore, it is suspected that torsional nystagmus in the lateral medullary infarct syndrome may originate not in ventral but in rostral and dorsal lesions of the medulla, including the vestibular nucleus, which is related to torsional and vertical eye movements.
