A histometrical study on the globus pallidus in Huntington's disease.

Pathological change of the globus pallidus (GP) in 6 cases of Huntington's disease (HD) was examined histometrically by comparison with 10 normal control cases. All but 1 case of HD were in late stages of the disease. Total neuronal count, area of GP, and neuronal cell density were measured in 5 selected regions of coronal sections taken along the antero-posterior axis. Contrary to the findings of previous reports, no neuronal depletion was recognized in HD in any region despite marked atrophy of tissue bulk. The atrophy was more severe in the external segment (GPe) than in the internal segment (GPi). Reactive astrocytosis and fibrillary gliosis were observed in the atrophic lesions. These results indicate that atrophy of the GP can be attributed to striato-pallidal fiber loss and not to neuronal depletion even in the late stages. These findings support the hypothesis that loss of striato-GPe fibers plays the most important role in choreic movements in HD. It remains to be determined whether the pallidal neurons are also preserved in the end stage of the disease.