Disturbance of smooth pursuit caused by infarction of occipitoparietal cortex.

Two distinct deficits of ocular smooth pursuit could be demonstrated using two types of visual stimulus motion in a patient who had suffered bilateral occipitoparietal lobe infarction. First, in response to constant-velocity (zero acceleration) target motion, smooth pursuit gain (eye velocity/target velocity) was mildly impaired for tracking to the right but near normal for tracking to the left. For example, for a target moving at 28.5 degrees/sec, gain was 0.65 to the right but 0.85 to the left. Second, in response to high-acceleration sinusoidal target motion, there was a deficit in maximum eye acceleration for targets moving right and left. The patient was unable to accelerate his eyes faster than 48 degrees/sec2 to the right and 95 degrees/sec2 to the left (normal is more than 300 degrees/sec2). It is suggested that smooth pursuit should be routinely tested using stimuli with a wide range of accelerations.