Ocular flutter associated with a lesion of the right upper pontine tegmentum.

Ocular flutter is a relatively rare eye movement disorder characterized by intermittent bursts of conjugate horizontal saccades without an intersaccadic interval. Its anatomical and neurophysiological basis remains controversial. Here we present a case of ocular flutter in which the flutter declined as the clinical stage of the associated ailment declined, until it eventually disappeared. Radiological examination revealed a tiny lesion in the right upper pontine tegmentum that included areas of the reticular formation, superior cerebellar peduncle and locus ceruleus. Because the lesion occupied the upper part of the paramedian pontine reticular formation, it did not contain omnipause neurons, which would seem to contradict a previously hypothesized explanation for ocular flutter: loss of pause cell control over saccadic burst neurons. On the other hand, we found no lesion in the area of the deep cerebellar nuclei; instead, the lesion was in the path of the projection from the fastigial nucleus to the brainstem saccadic generator. This is consistent with the idea that, in this case, there is impaired control by the cerebellar fastigial nucleus, especially of the horizontal saccadic system.