[A case of midbrain infarction with acute bilateral cerebellar ataxia].

An 81-year-old man was suffered from acute dysarthria and gait disturbance. Bilateral cerebellar ataxia and ataxic dysarthria were the only neurological findings. MRI images revealed an infarction in the lower and medial part of the midbrain. We consider that bilateral ataxia of the present case was caused by the lesion at the decussation of the superior cerebellar peduncle.