Acute disseminated encephalomyelitis (ADEM) is an immune-mediated, inflammatory acquired demyelinating syndrome predominantly affecting the white matter of the central nervous system.

We describe a three-year-old boy whose clinical presentation was suspicious for ADEM but whose initial imaging abnormalities were confined to the deep gray matter (without evidence of white matter involvement). His clinical course was fluctuating and repeat imaging one week after presentation demonstrated interval development of characteristic white matter lesions.

Treatment with adjunctive intravenous immunoglobulin and high-dose corticosteroids resulted in significant clinical improvement.

Isolated deep gray matter involvement can precede the appearance of white matter abnormalities of ADEM, suggesting that repeat imaging is indicated in individuals whose findings are clinically suspicious for ADEM but who lack characteristic imaging findings.