Huntington's disease: survival of large striatal neurons in the rigid variant.

A morphometric method was employed to investigate the relationship of rigidity and hyperkinesia to the degree of striatal and nigral nerve cell loss in one patient with the rigid variant of Huntington's disease and four patients with hyperkinetic chorea. Both striatal neuron populations, small and medium-sized neurons and large neurons, were affected in the patients with hyperkinetic chorea, whereas the large neurons were preserved in the patient with the rigid variant. The substantia nigra was slightly involved in each patient. The findings suggest that the rigid variant of Huntington's disease may reflect the unbalanced activity of residual, mostly large, striatal neurons, inhibiting the substantia nigra.