The relationship between the extent of local gray/white matter atrophy, genetic load, and clinical impairment was studied in Huntington's disease (HD) by means of voxel-based morphometry. T1-weighted brain images from 33 patients (mean age 49.5, range 25-73 years) with HD duration of 1 to 15 years were analyzed by correlation of each voxel intensity with the number of CAG triplets and the UHDRS-motor score (P < 0.001). The CAG number correlated inversely with gray matter intensity in the caudate nuclei and with white matter intensity in the both postcentral gyri and the right cerebellum. The UHDRS-motor score correlated inversely with the atrophy of both caudates, right hippocampus, calcarine fissure, and with the white matter along the fourth and lateral ventricles. While atrophy of the caudate nucleus was related to a higher number of CAG triplets and higher UHDRS-motor score, atrophy in other parts of the brain covaried with the two parameters differently: higher genetic load was associated with greater loss of cortical somatosensory projections and the worse UHDRS-motor score was accompanied by increased atrophy of the internal capsule, lower brainstem, hippocampus, and visual cortex. According to our results, the genetic load in HD predicts partially the extent of selective gray/white brain matter atrophy, which is then reflected in the severity of motor impairment.

Movement Disorders Center Department of Neurology 1st Medical Faculty Charles University Prague Czech Republic

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