Vertical and horizontal integrator failure in a ponto-medullary infarction: A possible role for paramedian tract neurons.

Gaze-evoked nystagmus is caused by a "leaky" neural integrator, which fails to maintain eccentric gaze positions after centrifugal eye movements. It is usually observed as the result of toxic, metabolic or paraneoplastic disorders, rather than single structural lesions. We demonstrate a case of an omnidirectional gaze-evoked nystagmus due to an ischemic paramedian ponto-medullar infarction. The most probable explanation is a damage of paramedian tract neurons, which have been recently recognized as a site of neural integration.