Cognitive impairment in spinocerebellar degeneration.

It has been reported that patients with spinocerebellar degenerations (SCDs) have cognitive dysfunction as well as limb and truncal ataxia, dysarthria and dysphagia. We review cognitive dysfunction in common types of SCD, including spinocerebellar ataxia types 1, 2, 3, 6, and 17, dentatorubral-pallidoluysian atrophy, Friedreich's ataxia, and multiple system atrophy. There are few studies that address cognitive function in SCD. Although there are few comparison studies among the various SCDs, cognitive dysfunction may be more common and severe in spinocerebellar ataxia type 17 and dentatorubral-pallidoluysian atrophy. While cognitive dysfunction in SCD appears to represent frontal dysfunction, the mechanisms of cognitive dysfunction have not been directly clarified. Nevertheless, various lesions, including those in the cerebrocerebellar circuitry, cortico-striatal-thalamocortical circuitry, and the frontal lobe, may influence cognitive function to various degrees for each disease.