Determinants of cognitive disorders in Autosomal Dominant Cerebellar Ataxia type 1

We assessed neuropsychological performances of 22 patients affected by Autosomal Dominant Cerebellar Ataxia type 1. All subjects completed a comprehensive battery of standardized tests requiring a verbal response, without time constraints. In order to verify the hypothesis that disease severity is the major factor in determining the cognitive status in this syndrome, patients were divided into three groups according to the severity of the clinical picture, as evaluated by the Inherited Ataxias Progression Scale (IAPS). Statistical analysis of the three groups' raw scores showed a significant decrement in patients with more severe clinical pictures on verbal short-term memory tasks. A similar trend, but not significant, was seen for general intelligence tests and verbal learning tasks. The decrement of verbal short-term memory could be related to motor speech problems. On the other hand, the decline of cognitive abilities over the course of the Autosomal Dominant Cerebellar Ataxia type 1 was not homogeneous enough to ensure statistically reliable trends. Therefore, this cross-sectional study suggests that the progression of the disease is a necessary factor in determining cognitive decline, but it is not sufficient. Other disease-related factors (age at onset, genotypic variety) could play a critical role: among these, the size of the expanded CAG repeats is significantly related to a decline of verbal intelligence and short-term memory in SCA2 patients.