Leptomeningeal and adventitial gliosis as a consequence of chronic inflammation.

Astroglial cell bodies and processes identified ultrastructurally and immunocytochemically are described within the subarachnoid and Virchow-Robin spaces of white matter throughout the CNS of Strain 13 guinea-pigs with chronic relapsing experimental allergic encephalomyelitis. These heterotopic astroglial elements, invariably in close proximity to subpial chronically-demyelinated lesions, were derived from subpial astrocytes and extended for great distances perpendicular and circumferential to the underlying white matter. Subpial astrocytes overlying adjacent grey matter regions appeared unaffected. This phenomenon is probably a subpial astrocyte response to inflammation and demyelination and may be related to the protection of damaged white matter against subsequent inflammatory events.