Possible mechanisms for horizontal gaze deviation and lateropulsion in the lateral medullary syndrome.

We report a patient who developed conjugate horizontal gaze deviation and ipsipulsion of saccades from a lateral medullary infarction. Recent evidence suggests that the gaze deviation may result from increased inhibition of the ipsilateral vestibular nucleus and ipsipulsion of saccades from decreased excitation of the contralateral ocular premotor areas of the brainstem reticular formation. Interruption of the olivocerebellar pathways may account for both of these ocular motor abnormalities.