Abstract #5805, Date Monday, Feb 21 2000 1:00PM - 12:00PM , Session ,

Vestibular dysfunction in spinocerebellar ataxia

John Harold Anderson , Baris Kazar , Amit Varma , Laura Ranum , John Day , Larry Schut , Christopher Gomez

The autosomal dominant cerebellar ataxias are a group of adult- or juvenile-onset neurodegenerative diseases characterized by progressive dysarthria and incoordination due to degeneration of cerebellar and brainstem neurons. Advances in the genetic understanding of these diseases has established that, despite similar clinical presentations, there are more than 8 genetically distinct subtypes designated as spinocerebellar ataxia (SCA). Clinical observations suggest that eye movements and postural stability are universally but differentially impaired in the SCAs, presumably due to regional differences in brainstem involvement in these diseases. Two aims of the present work were to study vestibular reflexes and eye movements in the SCAs to a) identify abnormalities useful for defining characteristics unique to a given SCA subtype and b) provide a greater understanding of the pathophysiology of the cerebellar ataxias. Patients representing each of the genetically known SCAs were examined. The vestibulo-ocular reflex (VOR) was recorded during whole-body rotations, saccade and pursuit eye movements were recorded while the subjects tracked a laser light, and postural stability was examined with a dynamic posturography protocol. The results showed characteristic patterns of VOR, eye movement, and postural stability abnormalities that were dependent on the SCA subtype. For example, for some SCAs the slow phase eye velocity of the VOR was severely reduced, while for other subtypes (SCA5, 6, 8) it was within or above the normal range. These and other results may help to identify diagnostic features for some SCA subtypes and provide valuable information about selective vulnerability of neurons controlling vestibular reflexes and eye movements. They also might identify traits common to all patients with cerebellar ataxia that will be useful as quantitative measures for evaluating therapeutic trials.

Supported by NIH grant, RO1 NS3721101.