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

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.

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).

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.

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.