WAIS-R features of preclinical Huntington's disease: implications for early detection.

BACKGROUND/AIMS: The main purpose of the study was to determine whether the predicted age of onset of Huntington's disease (HD) affects cognitive function as measured by the Wechsler Adult Intelligence Scale-Revised (WAIS-R). The subscales and subtests, and their potential selectivity were examined in preclinical HD (30 mutation carriers and 34 noncarriers) with no motor or neuropsychiatric signs of HD.

METHODS: The predicted age of onset in mutation carriers was calculated by a regression equation allowing this group to be divided according to whether onset was predicted as within 12 years (HD+CLOSE) or longer than this (HD+DISTANT).

RESULTS: The HD+CLOSE group scored significantly lower on Verbal, Performance, and Full Scale IQ compared to noncarriers and performed significantly lower on 7 of the 11 WAIS-R subtests, with low average scores in language abilities, attention, abstract thinking, problem solving, visuospatial ability, and psychomotor speed.

CONCLUSION: These low average scores affect general intelligence and functioning of HD+CLOSE carriers and are likely to reflect dysfunction of frontal cortex and frontostriatal circuits more than a decade before manifest symptoms. Our findings support a continuous linear model of slow cognitive decline in HD.