Pattern of Remyelination in the CNS

Abstract

FOR more than a decade it has been known^1–3 that glial cells are capable of forming new myelin sheaths around demye-linated axons in the central nervous system (CNS) but it is not known whether the new myelin is formed into segments bounded by true nodes and, if it is, whether the internodal length is appropriate to the axon diameter or inappropriately short as in remyelinated peripheral fibres. The different relationship between the myelin forming cell and axon in central and peripheral fibres makes this difficult to predict, Each Schwann cell in the peripheral nervous system (PNS) forms a single internode, whereas in the CNS a single oligo-dendrocyte usually forms a cluster of internodes on adjacent fibres^4,5. We have therefore studied the pattern of remyelination during recovery from acute experimental compression of the spinal cord, a lesion in which myelin destruction with preservation of axon continuity (demyelination) is followed by remyelination which commences in the third week⁶.