Partial ocular tilt reaction due to unilateral cerebellar lesion.

We report on two patients each with tonic, contraversive partial ocular tilt reactions due to unilateral cerebellar lesions: one patient had had a caudal cerebellar hemorrhage, the other a posterior inferior cerebellar artery territory infarct. Both patients had tonic contraversive conjugate ocular torsion; one had skew deviation; neither had a head tilt. One patient had no specific neurologic deficit apart from the conjugate ocular torsion, which was first suspected because of a deviation of the subjective visual horizontal. These observations imply that the ocular tilt reaction (OTR), a brainstem otolith-ocular reflex of probable utricular origin, is under the inhibitory control of the ipsilateral caudal cerebellum, possibly the nodulus, and that a patient with a cerebellar infarct can present with imbalance as the only neurologic symptom and with conjugate ocular torsion as the only specific neurologic sign.