Neuropathological background of oculomotor disturbances in olivopontocerebellar atrophy with special reference to slow saccade.

Neuropathological findings responsible for abnormal eye movements in olivopontocerebellar atrophy (OPCA) are reported. The material consists of eight sporadic cases and two hereditary cases. The sporadic cases showed impaired smooth pursuit without exception. The hereditary cases showed slow saccade (slow eye movement). Two important neuropathological findings are noted: The first is a systemic degeneration of cerebellifugal oculomotor control (cerebello-fastigio-vestibulo-MLF (medial longitudinal fasiculus) and perihypoglossal nuclei) in both types. Furthermore, neuronal loss of the oculomotor nuclei (oculomotor, trochlear and abducens nuclei) was found only in the hereditary cases. The second is that the hereditary type had a combined degeneration of the zona reticulata of the substantia nigra, the superior colliculus and the pontomedullary reticular formation. A review of the literature showed that all the cases of spino-cerebellar degeneration with slow saccade were hereditary OPCA, and that almost all cases had primary nigral degeneration. The neuropathological background of the oculomotor disturbances in OPCA is discussed.