Huntington's chorea: Young akinetic variant

The clinical and instrumental work-up to Huntington's chorea is reviewed focussing on two clinical variants: the most common being hyperkinetic and the other, encountered less frequently, the young akinetic variant. The young form presents a typical MR picture of a hypersignal from the neostriatum in long TR sequences. We present our personal series of six cases with a diagnosis of Huntington's chorea confirmed by the presence of other family members with full-blown disease. All patients underwent brain CT and MR with a high field system (1.5 T). Long TR and long and short TE Spin Echo sequences were performed on axial and coronal planes and short TR Spin Echo sequences on axial, sagittal and coronal planes. All patients were young with an average age of 22.5 years. In all cases CT disclosed bilateral atrophy of the head of the caudate nucleus, severe in two patients, moderate in two and average in the remaining two cases. However, CT failed to distinguish this variant from the more common hyperkinetic clinical form. In contrast, MR revealed the characteristic hypersignal in proton density and T2 of the putamen in all cases. The histo-pathological features of these two clinical variants of the disease are discussed as well as the sensitivity and specificity of CT and MR. CT only reveals atrophy of the caudate nucleus head from dilatation of the frontal horns, whereas MR directly displays atrophy of the striatum and occasionally, within the nucleus pallidus. In the young rigid variant MR also discloses the characteristic bilateral hyperintensity of the putamen. This finding is not characteristic per se as it reveals general reactive gliosis, but becomes pathognomonic in this typical location and given its absence in the hyperkinetic variant. In conclusion the authors postulate a possible lesional etiology resulting from degeneration of the medial and lateral striato-pallidal projections.