CHARCOT1 was apparently the first to point out the essential histologic features of sclerotic plaques: the absence of myelin, the presence of axis-cylinders, the fibrous gliosis and the perivascular infiltration with phagocytic cells. This much of his description has been copied in almost every textbook. Two of the other alterations which he clearly recognized have since appeared and disappeared repeatedly in scientific literature: the narrowing and closure of vessels and the loss of axis-cylinders, which, he wrote, "persist in certain number."
Chiefly, apparently, on the basis of the histology of sclerotic plaques Charcot founded the important distinction between secondary and primary degeneration of myelin. Secondary degeneration is the result of the destruction of axis-cylinders, or nerve cells. The neurofibrils disappear distal to the lesion, and the myelin then begins to disintegrate. Primary degeneration is a process which attacks almost all the myelin sheaths in an area of tissue, leaving
PUTNAM TJ, ALEXANDER L. LOSS OF AXIS-CYLINDERS IN SCLEROTIC PLAQUES AND SIMILAR LESIONS. Arch NeurPsych. 1947;57(6):661–672. doi:10.1001/archneurpsyc.1947.02300290021001
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