Clinical and Magnetic Resonance Features of the Classic and Akinetic-Rigid Variants of Huntington's Disease

We studied 32 patients with confirmed Huntington's disease (HD); six (mean age, 31.7 years) had the akinetic-rigid form and 26 (mean age, 46.1 years) had the classic hyperkinetic form. Clinical examination included a count of abnormal involuntary movements, motor self-sufficiency evaluation by the Physical Disability Rating Scale, cognitive function assessment by the Mini-Mental State examination, and a verbal fluency test. Magnetic resonance imaging permitted measurement of bicaudate diameter, a sensitive indicator of caudate atrophy in HD. Patients with the akinetic-rigid form of HD were younger and had earlier disease onset than those with the classic form of HD. All patients with akinetic-rigid HD (group 1) had striatal hyperintensity on T2-weighted magnetic resonance images; seven patients with classic HD (group 2) had a similar abnormality. Groups 1 and 2 were in fact similar in all other respects, except that the number of abnormal involuntary movements was greater in group 2. Groups 1 and 2 together had significantly younger age at onset, lower Mini-Mental State Examination score, more severe motor disability, worse verbal fluency test result, and greater bicaudate diameter than the 19 patients with classic HD without magnetic resonance signal abnormality (group 3) and appear to be a uniform population, distinct from group 3. The abnormalities on magnetic resonance images indicated greater striatal damage in groups 1 and 2, which could be the neuroanatomic substrate of their greater motor and cognitive compromise.