Neuropathology in Huntington's disease (HD) known to project to areas that process olfactory information raises the questions of which olfactory function, if any, is most affected in HD, and how to explain such dysfunction in terms of olfactory sensitivity and cognition. These questions were studied by comparing HD patients and controls (matched for age, gender, and education) on absolute detection, intensity discrimination, quality discrimination, short-term recognition memory, and lexical- and picture-based identification for odor. Taste or vision were used as comparison modalities. The results suggest that whereas odor-recognition memory is not affected in patients with HD, these patients have impaired olfactory functioning with respect to absolute detection, intensity discrimination, quality discrimination, and identification. The three latter impairments were significantly explained by poor detection sensitivity. Odor identification was the function most affected. (JINS, 1995, I, 281–290.)

We compared 7 mildly affected Huntington's disease (HD) patients to 7 age- and education-matched healthy controls (NC) on an odor detection test, the California Odor Learning Test, and the California Verbal Learning Test. Results demonstrated that odor detection sensitivity, but not group membership, accounted for significant variance in total olfactory learning. Both groups learned fewer items in the olfactory modality compared to the verbal modality, but retained a similar amount following a delay. No group differences were demonstrated for verbal recognition discriminability, but the HD group demonstrated significantly impaired odor recognition discriminability. Finally, odor detection provided excellent classification sensitivity and specificity between the patients and controls, suggesting that olfactory testing may provide a sensitive measure of the early disease process in HD. (JINS, 1999, 5, 609–615.)