Neuropsychological abnormalities in cerebellar syndromes--fact or fiction?

In recent years, theoretical considerations and a large number of empirical investigations have been published in support of a cerebellar involvement in cognitive processing. This chapter aims at a critical evaluation of the neuropsychological findings from clinical studies of patients with cerebellar syndromes. The discussion will mainly consider data from patients with selective cerebellar dysfunction, as data from patients with combined cerebellar and extracerebellar damage are of limited value for the issue of a cerebellar involvement in cognition. Early clinical observations indicated that degenerative diseases or selective cerebellar lesions did not necessarily give rise to general intellectual impairment such as dementia. Recent neuropsychological evidence based on standardized testing does not yet provide a clear picture. Deficits in motor learning or temporal processing are consistently observed in patients with cerebellar syndromes, while the cerebellum does not appear to be critically involved in general intellectual capacities or memory. Deficits in frontal lobe function, visuospatial processing or nonmotor skill learning have been reported in several studies, but have not been replicated in others. Such discrepancies may relate to a number of methodological problems. Future neuropsychological studies should take such methodological issues into account by using patients with selective cerebellar dysfunction, adequately matched clinical and non-clinical comparison groups, and theory-driven iesl batteries comprising a wide range of tests.