Dark cerebellum on Apparent Diffusion Coefficient maps—an early indicator of fulminant cerebellitis

Fulminant cerebellitis is an important cause of acute severe encephalopathy with raised intracranial pressure in an otherwise healthy child. If the diagnosis is delayed or missed, this can be fatal. Magnetic resonance imaging of the brain helps in early diagnosis. Though signal changes on T2 and fluid attenuation and inversion recovery sequences in fulminant cerebellitis have been described, the findings on diffusion weighted imaging and apparent diffusion coefficient maps have been rarely described in the literature. While the diffusion weighted image shows a bright signal, the apparent deficient coefficient map shows a dark cerebellum. There can be brainstem compression and cerebellar tonsillar herniation. Here we report a young boy with acute onset of coma who had a dark cerebellum on apparent deficient coefficient maps that prompted early treatment with resultant good outcome. Clinical trial number: This study is not a clinical trial. Hence, ‘Clinical trial number: not applicable.’