Regeneration of myelin in multiple sclerosis

Abstract

The myelinated fibers in the plaques of multiple sclerosis were studied by a histochemical procedure which permits the distinction between myelin like that of peripheral nerves and the myelin of the central nervous system. In 5 instances, nerve fibers encased in periphera myelin were present within such plaques. These were associated with cells like those in peripheral nerves and with collagen and reticulin fibers. No such fibers were present in the normal tissues of these cases or of normal cases. The suggestion is made that this peripheral myelin had regenerated to cover axons which were still intact after the original central myelin about them had degenerated. It is further suggested that this was accomplished by specialized mesenchymal cells which took. origin from primitive mesenchymal cells, possibly microglial precursors. This interpretation overcomes many difficulties associated with the concept of the neurecto-dermal Schwann cell thought to be present only in peripheral nerves and to be the only cell capable of producing peripheral myelin. The regeneration of myelin may play a role in the clinical remissions of multiple sclerosis, but other factors appear to be more important.