Figure 1.

Demyelination, axonal loss and disease progression in MS. (a) The early stage of relapsing–remitting MS is characterized by transient neurological deficits that return to normal and pathology dominated by demyelination and focal inflammation. However, as the disease progresses, neurological dysfunction becomes fixed and accumulates. The pathological correlate of the progressive phase of the disease is axonal loss. (b) The early events of demyelination and inflammation are believed to contribute to axonal loss by numerous mechanisms, including loss of oligodendrocyte/myelin-derived trophic and structural support. The schematic diagram shows a single oligodendrocyte (black and white) myelinating three axons (axon: purple; myelin: blue). Early in the course of MS, the oligodendrocyte is damaged resulting in the demyelination of the axon. The loss of oligodendrocyte ‘support’ contributes and culminates in the axonal loss as found in progressive MS.