Ocular motor disorders associated with cerebellar lesions: pathophysiology and topical localization

A number of ocular motor abnormalities can be correlated with damage in specific parts of the cerebellum, especially the vestibulo-cerebellum (flocculus, paraflocculus, nodulus, uvula), and the dorsal vermis and the underlying (posterior) fastigial nuclei. These abnormalities of eye movements reflect both immediate, on-line and long-term adaptive functions of the cerebellum. Various types of image-stabilizing reflexes are in the province of the flocculus (and probably paraflocculus) including pursuit, vestibulo-ocular reflex (VOR) cancellation, and holding the eye steady for fixation, both immediately after saccades and in eccentric positions of gaze. The nodulus (and ventral uvula) modulates "low-frequency" aspects of vestibular responses and hence controls the duration (time constant) of the VOR. The dorsal vermis and underlying (posterior) fastigial nuclei participate in the control of the size of the saccadic pulse of innervation and hence saccadic accuracy. Here we review the eye signs that reflect abnormalities of these clearly defined cerebellar functions. We will also discuss less well localized but presumed cerebellar eye signs and consider a potential role for the cerebellum in the control of both dynamic and static ocular alignment.