Detecting subtle clinical abnormalities in the ‘premanifest’ phase of Huntington’s disease (HD) is of importance in the development of instruments to monitor early therapeutic intervention trials. The current study examined changes in motor function, cognition and behaviour over a period of seven years in premanifest carriers of the HD gene mutation. Twenty-nine carriers without unequivocal motor signs of HD and 43 non-carrier controls were prospectively examined four times. The assessments consisted of the Unified Huntington’s Disease Rating Scale (UHDRS) and an extensive neuropsychological test battery addressing global cognitive function, memory, language and executive function. Rate of Change (RoC) analysis was performed to measure longitudinal differences between carriers and non-carriers. Carriers performed consistently worse on executive function (Symbol Digit Modalities Test (SDMT), Stroop, Trail Making Test (TMT) and WAIS-R arithmetic). Over the years, carriers showed a decline in memory and concentration function (Wechsler Memory Scale (WMS)) and in motor function (UHDRS motor scale). Changes over time could be particularly ascribed to carriers converting to manifest HD. These results demonstrate that standardized motor assessments and objective memory and concentration tasks are sensitive to change over a period of 7 years, specifically in carriers converting to manifest HD. Executive tasks also showed subtle cognitive abnormalities in premanifest HD, but a decline over time could not be demonstrated.
Increased iron levels have been demonstrated in the basal ganglia of manifest Huntington’s disease (HD). An excess in iron accumulation correlates with MRI T2-weighted hypointensity. Determination of the amount of hypointensities in the basal ganglia in the premanifest phase of HD may give more insight in the role of iron in the pathogenesis of HD. Therefore, the present study assessed whether the degree of hypointensities on T2-w MRI in the basal ganglia of premanifest gene carriers differs from non-carriers. Seventeen HD gene carriers without clinical motor signs and 15 non-carriers underwent clinical evaluation and MRI scanning. The amount of T2-w hypointensities was determined using a computer-assisted quantitative method that classified each pixel in the basal ganglia as hypointense or not, resulting in a total of hypointense pixels for each individual. Carriers showed an increased amount of hypointensities in the basal ganglia compared to non-carriers. More hypointensities were furthermore associated with a higher UHDRS total motor score, a longer CAG repeat length and a greater probability of developing symptoms within 5 years. We concluded that the increased amount of hypointensities in the basal ganglia of premanifest carriers of the HD gene may reflect excessive iron deposition and a role for iron in the neuropathology of HD. Furthermore, this phenomenon is associated with clinical and biological disease characteristics. An increased amount of hypointensities on T2-w MRI in the basal ganglia may be considered a biomarker for HD.