DYSFUNCTION OF PONTINE OMNIPAUSE NEURONS CAUSES IMPAIRED FIXATION - MACROSACCADIC OSCILLATIONS WITH A UNILATERAL PONTINE LESION

Macrosaccadic oscillations of eyes (MSG) are regarded as a form of sac cadic dysmetria secondary to cerebellar dysfunction. They are usually conjugate, horizontal, and symmetric in both directions of gaze. Using magnetic search coils, we studied a patient with MSO that developed f ive years following head injury and involved synchronously horizontal, vertical, and torsional planes. The MSO were characterized by directi onal preponderance and were associated with ipsilateral pontine lesion , We propose a disturbance of fixation mechanisms due to unilateral di sinhibition of sac cadic burst neurons in three planes, This could ari se from either primary or secondary dysfunction of omnipause neurons, due to impaired input from the contralateral superior colliculus. The delayed onset is suggestive of denervation supersensitivity as the und erlying pathophysiology.