Magnetic resonance imaging in the diagnosis of acute disseminated encephalomyelitis (ADEM)

Purpose: This study evaluates how the use of MRI contributes to the diagnosis of acute disseminated encephalomyelitis (ADEM). Methods: The study population consisted of 56 patients (29 males, 27 females) ranging in age from 1 to 70 years, who were followed clinically and neuroradiologically for a period of 1.5 to 2 years. Results: In this group, the ADEM lesions were iso-hypointense in T-1-weighted images and hyperintense in long TR sequences. They almost always were multiple, bilateral, and asymmetrical in size and morphology. In 33 patients, contrast administration revealed contrast enhancement of all the lesions. In 10 patients some lesions enhanced, while others did not. In 5 cases, only a single lesion showed enhancement. Conclusions: The diagnosis of ADEM should be considered in patients with neurologic symptoms when MR displays multifocal bilateral asymmetrical white matter lesions, especially when all enhance simultaneously. Differential diagnosis from multiple sclerosis is very difficult, because ADEM and MS may exhibit similar clinical and MRI features. Correct diagnosis ultimately depends on long-term follow-up.