Figure 2.

Central nervous system (CNS) axons are myelinated by oligodendrocytes (upper part: Healthy myelin). In RR-MS, during relapse, oligodendrocytes and myelin sheaths are destroyed (middle part: Acute demyelination). In disease remission the new oligodendrocytes generated from a widespread population of oligodendrocyte precursors put new myelin sheaths around the demyelinated axons (lower part, left side: Remyelination). Disease progression occurs when remyelination fails (lower part, right side: Chronic demyelination, axonal degeneration).