[Small cerebellar vascular lesion can produce isolated conjugate deviation of the eyes]

The cerebellum has almost never been considered responsible for conjugate deviation of the eyes (CDE). A few cases of CDE caused by cerebellar lesions without the involvement of the brainstem have been reported, but the lesions were too large to evaluate their localization in the cerebellum. In this report, we describe 2 cases of isolated CDE caused by small cerebellar vascular lesions and a case of CDE and staggering gait that occurred following cerebellar infarction. We further describe cases of head rotation without CDE and those of vertigo without CDE or head rotation due to a similar small lesion. Case 1: A 73-year-old woman with rheumatism was brought to our department because of sudden-onset of difficulty in looking to the right. She was admitted 3 hours after onset; at admission she was alert and well-oriented and denied both vertigo and nausea. Neurologic examination revealed CDE to the left; however, no limb ataxia was detected. Diffusion-weighted MRI showed a small infarction in the white matter of the right PICA area near the vermis. Her CDE disappeared spontaneously within 2 days. Case 2: A 79-year-old man with hypertension exhibited CDE to the right without vertigo or ataxia following a small hemorrhage in the cerebellan area mentioned in Case 1. Case 3: A 65-year-old man with hypertension presented with CDE to the right and staggering gait after a small infarction in an area lateral to that mentioned above. The first 2 cases suggest that a small cerebellar vascular lesion can produce isolated CDE to the side contralateral to the lesion. The region responsible for CDE in these cases was located in the white matter of the PICA area near the vermis, although similar lesions in Cases 4 and 5 produced no CDE.