Evidence for sequential degeneration of the neurons in the intermediate zone of the spinal cord in amyotrophic lateral sclerosis: a topographic and quantitative investigation.

To elucidate the degenerating mechanism of the neurons in the intermediate zone of the spinal cord in classical amyotrophic lateral sclerosis (ALS), the spinal neurons in a patient with ALS, whose muscular strength was fairly well preserved up to death, were examined quantitatively and topographically, and compared with the data of advanced ALS patients and age-matched control subjects reported previously. In advanced ALS patients, anterior horn cells completely disappeared and the medium-sized (nuclear area; 71-150 microns 2) and large (nuclear area; greater than 151 microns 2) neurons in the intermediate zone were severely reduced. In the present case, however, the loss of anterior horn cells was severe but the degree was not equal to that of advanced ALS patients, and the neurons in the intermediate zone were quite well preserved. The finding indicates that the primary degeneration may occur in the anterior horn cells and the neurons in the intermediate zone degenerate sequentially in the spinal gray matter in ALS.