An adult-onset multiphasic disseminated encephalomyelitis (MDEM) presenting favorable response to steroid therapy.

A 64-year-old man presented with acute onset of generalized seizure and encephalopathy. FLAIR images of brain MRI showed multifocal high-intensity lesions of the white matter. Within few days after the treatment with intravenous methylprednisolone (1,000 mg/day for 3 days), amelioration of clinical symptoms and recovery of MRI findings were observed. Six months after the withdrawal of oral steroid therapy, recurrent lesions were observed at the same locations as initially revealed on admission. Due to the concomitant development of peripheral lymphocytosis, a brain biopsy was performed from a right frontal lesion. Histological findings suggested extensive demyelination accompanied by infiltration of inflammatory lymphocytes and macrophages. In spite of the temporary remission after re-initiation of oral steroid therapy, reduction of oral steroid dosage resulted in new lesion formation apart from the initial locations. Based upon clinical features, MRI findings and histological examination, he was diagnosed with multiphasic disseminated encephalomyelitis (MDEM). Acute disseminated encephalomyelitis (ADEM) is one of common causes of demyelinating disease among children. However, multiphasic form of ADEM is particularly rare in adult patients. Here we reported a rare case of adult-onset MDEM, in which clinical, radiological and histological features were described, and efficacy of steroid therapy was highlighted.