Acute demyelination, neuropathological diagnosis, and clinical evolution

A retrospective analysis of 14 patients who presented with a progressively expanding mass lesion(s) shown at biopsy/autopsy to represent acute demyeli nation was carried out. The aims of this study were to determine the optima l neuropathological approach to diagnosis and to determine the clinical evo lution of this condition. Subsequent investigations and clinical outcome st udies confirmed MS in 10 cases. Two patients had received an incorrect neur opathologic diagnosis of astrocytoma resulting in cranial irradiation. Key histologic parameters in establishing a diagnosis of acute demyelination we re a predominance of lipid filled macrophages, macrophage alignment along a xons, and an absence of oligodendroglial inclusions. Axonal injury was pres ent in all cases and a lymphocytic/plasma cell infiltrate was sparse in are as of demyelination. Neuroimaging revealed single lesions in 10 patients an d multiple lesions in 4 patients. Two patients were lost to follow-up, 3 di ed within 18 months of diagnosis, 8 had a relapsing remitting clinical cour se, and 1 patient had a chronic progressive course. In conclusion, a dense lymphocytic and plasma cell infiltrate is unusual in acute human demyelination. Although axonal injury is a frequent histologic finding in acute demyelination, it does not preclude a favorable clinical outcome.