Neuropsychiatric and Cognitive Symptoms in Spinocerebellar Ataxia: Relationship to Neuropathological Differences

The autosomal dominant spinocerebellar ataxias (SCA) are a heterogeneous group of disorders associated with progressive degeneration of the cerebellum and other brain regions to varying degrees. Neuropsychiatric and cognitive symptoms are now considered to be well established clinical features of the SCA's, and one central area of research is to examine clinical differences in neuropsychiatric and cognitive symptoms between SCA subtypes and their relationship to underlying neuropathological features. Among the most common SCA subtypes (SCA 1,2,3 and 6), memory impairment and depression occur most frequently in patients with SCA3, possibly related to relatively greater dysfunction of frontal-subcortical circuits through degeneration of the basal ganglia. In contrast, patients with SCA6 are less frequently depressed and demonstrate normal performance on measures of intelligence, attention, verbal and non-verbal memory, and executive functions. This implies that non-motor cognitive functions are less commonly affected in SCA6 possibly due to the more restricted expression pattern of the mutated calcium channel gene in this disorder. Patients with SCA2 demonstrate impairment in multiple cognitive domains including verbal memory and frontal lobe functions suggesting a more generalized process. These findings highlight the importance of evaluating all patients presenting with progressive ataxia for neuropsychiatric and cognitive symptoms.