Unilateral lesion of the paramedian pontine reticular formation: Loss of rapid eye movements with preservation of vestibulo-ocular reflex and pursuit

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Abstract
A 55-year-old man had a spontaneous hemorrhage into the pontine tegmentum causing a saccadic gaze palsy with slowing and truncation of all rapid eye movements to the left, and a paralysis of the left lateral rectus muscle. There was no gaze-paretic nystagmus to the left. The vestibulo-ocular reflex and pursuit movements were preserved. In analogy to ocular motor deficits found after experimental lesions in the monkey the authors postulate involvement of the left paramedian pontine reticular formation (PPRF) and the left abducens fasciculus. The location of pathology in the CT scan is consistent with such a hypothesis. The following conclusions can be drawn: (1) The PPRF is not necessary for holding ipsilateral gaze, and (2) smooth pursuit movements and the vestibule-ocular reflex are not mediated by the PPRF.