Perspectives on meningoencephalomyelitis of unknown origin.

Meningoencephalomyelitis of unknown origin (MUO) is a heterogeneous group of overlapping central nervous system inflammatory diseases of unknown cause. This article highlights the current understanding of MUO and its phenotypic variants encountered in clinical practice. Diagnostic evaluation of presumptive MUO includes lesion distribution on magnetic resonance imaging and ruling out other acquired diseases. Recent evidence provides further knowledge of immune-mediated processes that underlie the pathogenesis of MUO. Current empiric treatment options include corticosteroids and other adjunctive immunomodulating therapies. As the understanding of neuroimmunology and genetic influences on these disorders evolves, a more targeted treatment approach is becoming attainable.