Impaired Rightward Saccades with Preserved Rightward Pursuit Following Right Pontine Ischemic Stroke (.pdf)

"The pontine paramedian reticular formation (PPRF) is the brainstem saccadic generator. Pursuit axons pass through the PPRF but do not synapse there. In macaques, injection into the PPRF of neuronal toxins that spare axons selectively paralyzes saccades. In humans, selective impairment of horizontal and vertical saccades with preserved horizontal pursuit and vestibulo-ocular reflex has been described following cardiac surgery with or without documented systemic hypotension. Imaging has been negative except for one case in which focal FLAIR hyperintensity appeared in the dorsomedial pons unilaterally 10 months after the event. In one autopsied case, there was neuronal necrosis, axonal loss, and astrocytosis in the pontine paramedian reticular formation bilaterally. Ocular motor nuclei and cerebral gaze-generating centers were histologically normal. In a second case3, necropsy pathology was negative, suggesting submicroscopic damage to PPRF inputs as the explanation for saccadic paralysis. We present a patient who developed a selective right horizontal saccadic palsy in conjunction with ipsilateral dorsomedial pontine infarction in the region of the PPRF."