Neuropsychological stability over two years in asymptomatic carriers of the Huntington's disease mutation.

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Abstract
This study examined whether neuropsychological changes emerge over time in asymptomatic adults who have the Huntington's disease mutation. We also evaluated whether scores on cognitive tests or psychological symptom scales varied as a function of CAG repeat length or proximity to disease onset. Twenty two healthy "mutation positive" and 37 "mutation negative" adults completed cognitive tests and psychological rating scales before disclosure of their genetic test results and on an annual basis thereafter. Repeated measures ANOVAs analysed differences between the two groups over three assessments. Correlations of cognitive and psychological symptom test scores with estimated number of years to disease onset and CAG repeat length were computed. The two groups did not differ at study entry; nor did they differ in the rate of change over time. Tests of sustained attention and mental speed correlated with estimated years to disease onset, but not with repeat length. As a group, clinically asymptomatic adults with the Huntington's disease mutation do not display neuropsychological deficits when studied over a two year interval. However, persons who are likely nearing clinical onset of Huntington's disease may develop minor deficits in selected cognitive domains before they reach threshold for diagnosis.