Delayed MR imaging changes in acute disseminated encephalomyelitis

BACKGROUND AND PURPOSE: White matter lesions on MR images obtained from pat ients with acute disseminated encephalomyelitis (ADEM) have been reported t o appear shortly after symptom onset, and their resolution has been claimed to parallel recovery. To elucidate the temporal evolution of these lesions and to associate the changes on MR images to the patients' clinical condit ion, we performed serial MR imaging on patients with ADEM, METHODS: Several consecutive T2-weighted and fluid-attenuated inversion rec overy scans were obtained from four previously healthy adult patients with ADEM within the first days after the onset of symptoms and again during the recovery period. MR imaging was done first on a weekly to biweekly basis a nd later at 1- to 2-month intervals for up to 8 months. RESULTS: MR scans of three of these patients did not show any specific abno rmalities until several weeks after the onset of the disease. As the lesion s later appeared, their number increased during the recovery period. CONCLUSION: MR imaging performed during the first days after the onset of t he disease may not reveal any pathologic findings. The appearance of the AD EM-associated MR imaging changes may be associated with recovery rather tha n decline. It remains to be studied whether the new MR imaging techniques r eveal the lesions associated with ADEM faster than the conventional T2-weig hted imaging.