Recurrence of acute disseminated encephalomyelitis at the previously affected brain site

Background: Acute disseminated encephalomyelitis (ADEM) is a usually monoph asic demyelinating disorder of the central nervous system. Recurrences pose a diagnostic challenge because they can be overlooked or suggest an altern ative diagnosis. Objective: To examine the frequency, nature, and outcome of recurrent ADEM. Design: Review of the medical records of patients diagnosed in our institut ion as having ADEM between January 1, 1983, and May 31, 1998. Recurrences w ere defined as appearance of new symptoms and signs at least 1 month after the previous episode. Results: Five (24%) of 21 patients with ADEM developed recurrent disease ep isodes. In all, diagnosis was confirmed by brain biopsy. One patient had 4 disease episodes, 2 had 3, and the other 2 each had 2. Recurrence appeared 1.5 to 32 months after initial presentation and involved the same brain ter ritory in 6 of 9 recurrences in 3 of 5 patients. In 2 patients, recurrences included neuropsychiatric signs. A good response to corticosteroid therapy was observed in 10 of 13 of treated ADEM attacks: in 3 of the 4 treated in itial events and in 7 of 9 recurrences. Conclusions: Recurrent ADEM may be more prevalent than previously recognize d. Patients who relapse tend to have more than 1 recurrence that usually in volves, clinically and radiologically, a brain territory that was affected before and can simulate a space-occupying lesion that requires histologic d iagnosis. Neuropsychiatric features may be the main presentation of a relap se. Since recurrent ADEM is a corticosteroid-responsive condition, awarenes s and early diagnosis are mandatory.