Neuromyelitis optica: a demyelinating disease characterized by acute destruction and regeneration of perivascular astrocytes

Objective: To determine whether there is an astrocyte lesion in NMO and if this differs from astrocyte changes in multiple sclerosis (MS). Methods: Astrocyte pathology in early (still-myelinated) lesions and subacute NMO and MS lesions was examined immunohistochemically and in sections stained for astrocytes using routine histological techniques. Results: Demyelination in early NMO lesions is accompanied by oligodendrocyte apoptosis in a pattern identical to that seen in MS and this is preceded by an abrupt destruction of perivascular astrocytes. Reparative astrogliosis is effected by a population of unipolar, new astrocytes. Evidence of a different type of astrocyte lesion was found in MS. Discussion: The findings add to experimental evidence that the antibody is pathogenic. They also raise the possibility that demyelination in MS may be a bystander effect of an astrocyte lesion, i.e. that MS is not a disease primarily of myelin and oligodendrocytes.