Morphometric and topographical studies of small neurons in sporadic amyotrophic lateral sclerosis spinal gray matter

Little attention has been paid to the degeneration of small neurons in ALS spinal gray matter. The purpose of the present paper was to undertake morphometric and quantitative analysis of the spinal gray matter of 15 ALS patients and compare findings to those of five controls. A significant reduction of small neurons in the anteromedial and intermediate parts of the gray matter were detected in ALS spinal cords with diffuse myelin pallor in the ventral aspects of the anterolateral columns outside the corticospinal tracts, and the number of small neurons in these areas was decreased significantly depending on the intensity of the myelin pallor. There were no significant alterations in the number of small neurons in the corresponding areas of ALS spinal cords without diffuse myelin pallor or in those of controls. In the posterior parts of the gray matter, there were no significant differences in the number of small neurons among ALS patients and controls. These findings strongly suggest that diffuse myelin pallor in the ventral aspects of anterolateral columns in ALS spinal cords is derived from the degeneration of small neurons in the anteromedial and intermediate parts of the gray matter.