Eye movement abnormalities in a family with cerebellar vermian atrophy.

We report the oculographic findings in a family whose members have a dominantly inherited, early onset, non-progressive syndrome which includes spontaneous upbeating nystagmus and mild cerebellar ataxia associated with cerebellar vermian atrophy seen on magnetic resonance scanning. Eye movements recorded with electro-oculography and a magnetic scleral search coil revealed severely impaired horizontal and vertical smooth pursuit, optokinetic nystagmus and visual-vestibular interaction, symmetrical horizontal but asymmetrical vertical vestibulo-ocular reflex, and normal saccades. The midline cerebellum appears to be essential for both horizontal and vertical visual tracking and visual modification of the vestibulo-ocular reflex in man.