The development of periventricular lesions in chronic relapsing experimental allergic encephalomyelitis in guinea-pigs: a light and scanning electron microscopic study.

Periventricular lesions in the centrum semiovale are the most frequent changes in the brain in chronic relapsing experimental encephalomyelitis in guinea-pigs. They are generally distributed symmetrically at the lateral angle of the ventricular wall. The number of lesions and their size increases in anterior-posterior direction. Typically periventricular lesions in the later chronic stages are similar to those in multiple sclerosis. Earlier lesions generally originate in the depth of the white matter and secondarily, by extension, reach the ventricular surface. Lesions developing at later stages after sensitization may also originate from the ventricular wall and extent into the centrum semiovale. In these latter, severe structural changes in the ventricular ependyma may generally be found. Increased intracranial pressure in these animals may be one of the possible mechanisms leading to the peculiar topographical distribution of the periventriuclar lesions.