Balo's concentric sclerosis. Report of two patients with magnetic resonance imaging follow-up.

Balo's concentric sclerosis was diagnosed antemortem in 2 patients, by magnetic resonance (MR) imaging showing striking concentric alternating rings in 1 patient and by characteristic histopathological features in the other. The course of the lesions and the concentric pattern were followed by MR imaging for 3 years and 18 months, respectively. One patient demonstrated spontaneous remission that has not been reported in Balo's disease. Balo's disease may not have a fulminant course as described in the past and the MR appearance of the chronic lesion may resemble that of a chronic multiple sclerosis plaque.