UNIMPAIRED VERBAL MEMORY AND OCULOMOTOR CONTROL IN ASYMPTOMATIC ADULTS WITH THE GENETIC-MARKER FOR HUNTINGTONS-DISEASE

Objective.-To determine whether asymptomatic individuals at very high genetic risk for Huntington's disease (HD) have demonstrable cognitive or oculomotor abnormalities. Design.-A case-control study was employe d. Presence of the chromosome-4 DNA marker linked to the HD phenotype was the criterion for HD risk. Setting.-The Baltimore Huntington's Dis ease Project Presymptomatic Testing Program at The Johns Hopkins Unive rsity School of Medicine, Baltimore, Md. Participants.-Seventy-six asy mptomatic adults at risk for HD, voluntarily enrolled for genetic test ing, and determined by clinical examination to be free of major psychi atric disorder or evidence HD. Twenty were determined to be at 95% ris k for HD; 56 were at 15% risk. Measures.-The Hopkins Verbal Learning T est was used to assess verbal learning and memory. Oculomotor function ing was assessed using Novel-Stimulus, Mirror-Stimulus, and Predictive -Saccade paradigms. outcome measures included number of correctly reca lled words, recognition accuracy, and response bias, as well as saccad e latency and number of errors on the Mirror-Stimulus Test. Results.-W ith one exception, all participants performed within the normal range on the Hopkins Verbal Learning Test. In a blind follow-up examination of the individual who performed aberrantly on the Hopkins Verbal Learn ing Test, she exhibited neurologic and psychiatric changes sufficient for a clinical diagnosis of HD. There were no group differences on the tests of oculomotor functioning. Conclusions.-Young, asymptomatic adu lts at very high genetic risk for HD are unimpaired in tests of verbal learning and memory and oculomotor functioning.