A quantitative investigation of the substantia nigra in Huntington's disease

To elucidate the quantitative and topographical changes of neurons in the substantia nigra in Huntington's disease (HD), sections from 4 HD patients and 8 age-matched control subjects were stained with cresyl violet and the numbers and localization of pigmented and nonpigmented neurons in the substantia nigra were examined. This study revealed a decrease of about 40% (p less than 0.01 or p less than 0.05) in neuronal number and a shrinkage of both pigmented and nonpigmented neurons in the substantia nigra in HD. Pigmented neuron number was decreased markedly in the ventral cell group. Loss of the neurons occurred in the medial and lateral thirds, but relative sparing of the neurons was seen in the central part of the substantia nigra. In contrast, loss of nonpigmented neurons was relatively uniform in the substantia nigra although it was more severe in the central part. We conclude that a primary neuronal degeneration occurs in the substantia nigra in HD.