Answers

Acute plaque (A): Minor changes (e.g. oedema) and often difficult to recognize Early chronic active plaque (B): Oedema and macrophages, indicative of an inflammatory disorder of the central nervous system, with some myelin breakdown. Reactive astrocytosis is present Late chronic active plaque (C): Complete loss of myelin. Some macrophages will contain myelin debris and there will be often very mild perivascular inflammation at this stage with enlarged perivascular spaces Chronic inactive plaque (D): Complete loss of myelin with the absence of macrophages Shadow plaque (E): Nearly complete remyelination as a thin myelin with some scattered macrophages and a mild microglial up-regulation.