Remyelination in Multiple Sclerosis with Peripheral Type Myelin

Unusually large areas of remyelination occurred in demyelinated plaques within the spinal cord of a patient with longstanding multiple sclerosis (MS). The regenerated myelin was indistinguishable from that of the peripheral nerves by optical and electron microscopy. The myelinforming cells within the spinal cord, morphologically identical to the Schwann cells, could be traced to the spinal nerve roots. At the periphery of the remyelinated zones, astrocytic processes were present adjacent to the regenerated peripheral type myelinated fibers similar to those normally seen in the nerve roots close to the spinal cord. In addition, Rosenthal fibers were frequently seen in such zones. There was no appreciable clinical improvement in this patient attributable to the remyelination. The mechanism of such focal remyelination in this otherwise typical case of MS remains obscure.