Atrophic cell processes of large motor neurons in the anterior horn in amyotrophic lateral sclerosis: observation with silver impregnation method.

Investigation of silver-stained lumbar anterior horns in four autopsied cases of sporadic amyotrophic lateral sclerosis (ALS) revealed frequent extremely small cell processes originating from large motor neurons. Their perikarya were usually smaller in size than those of normal-looking ones and almost invariably had central chromatolysis-like changes, suggesting an intimate pathomorphological relationship between the perikarya and their processes. Although it was difficult to determine whether these small processes were atrophic dendrites or shrunken axons, some were recognized as dendrites from their multiple branchings and some were identified as axons from their tapering configuration followed by widening of the distal portion. Aggregates of lipofuscin were almost always present in the perikaryal portion from which an atrophic process arose. In addition, the somewhat argentophilic slender cytoplasm which in normal neurons separates lipofuscin from the cell surface and merges with the proximal part of a process, was prominently attenuated. The small processes were more frequently observed in cases with many spheroids and chromatolytic neurons. The change in the proximal portion of the processes may implicate some disturbance of functional connection between the soma and the cell processes in ALS.