NEUROPSYCHOLOGICAL TEST-PERFORMANCE IN PATIENTS WITH DOMINANTLY INHERITED SPINOCEREBELLAR ATAXIA - RELATIONSHIP TO ATAXIA SEVERITY

To determine whether the cognitive status of patients with dominantly inherited spinocerebellar ataxia (DSCA) might be related to neurologic severity, we administered a comprehensive neuropsychological test bat tery to 43 patients with DSCA, ranging in ataxia severity from mild to end-stage. As compared with the controls, the mildly ataxic patients scored normally or close to normal as a group on all of the neuropsych ological tests. In contrast, approximately one-half of the moderately and all of the severely ataxic patients showed poor performance, indep endent of age, Hamilton Rating Scale for Depression score, or educatio n, on the Wisconsin Card Sorting Test, suggesting impaired executive s ystem function. In addition, a subgroup of these patients had a neurop sychological profile suggestive of mild generalized cognitive impairme nt. We conclude that DSCA is not a homogeneous group of disorders with respect to cognitive status and that the neurologic severity of the d isorder is a major factor. Impaired executive system function could be explained by damage to olivopontocerebellar system control over cereb ral cortical function or to damage to other neuronal systems (especial ly cholinergic) that degenerate in parallel with the olivopontocerebel lar system.