[Convergence-retraction nystagmus associated with vascular disorders of the brainstem]

We report two cases of convergence-retraction nystagmus due to cerebral infarction and hemorrhage. Magnetic resonance imaging disclosed a small area of abnormal signal in the thalamo-mesencephalic junction in each patient. This lesion appeared to include the rostral interstitial nucleus of the medial longitudinal fasciculus (rostral iMLF). The precise oculography of nystagmus in these patients demonstrated the fast adductive movements and slow exponential tract of abduction. The velocity of the fast phase was equal to or less than that of ordinary saccadic eye movements. The time constant of the slow phase was about 0.3 second. These characteristics are identical to those of pineal tumor cases.