Objectives: To describe the clinical, CSF, and radiologic findings and long-term follow-up in a cohort of patients with acute disseminated encephalomyelitis (ADEM), and to determine possible prognostic factors for progression to MS.
Methods: Forty adults (28 women, mean age 33.5 years) diagnosed with ADEM were analyzed. Clinical symptoms, cranial MRI and CSF findings, and the response to a standardized treatment during the acute phase of the disease were analyzed by chart review. The final diagnosis of ADEM or clinically definite MS was established upon follow-up examination after 8 to 137 months. The patients with ADEM and MS were compared to detect differences between the two groups.
Results: Fifteen patients had a preceding infection (n = 14) or immunization (n = 1). The most frequent clinical signs were motor deficit (80%), followed by sensory deficits, brainstem signs, and ataxia. CSF findings were highly variable; normal results were present in 20% of patients. Oligoclonal bands were positive in 65% of patients. Ninety-five percent of all patients improved during the acute phase of the disease. Upon follow-up, 14 patients had developed clinically definite MS. Of the 26 patients with the final diagnosis of ADEM, two patients had died, nine had minor deficits, three had moderate deficits, and 12 patients had no remaining symptoms. Patients with the final diagnosis of ADEM were older, and more often had a preceding infection, clinical signs of brainstem involvement, a higher CSF albumin fraction, and infratentorial lesions.
Conclusions: Many patients initially diagnosed with ADEM develop clinically definite MS upon long-term follow-up. The authors found no useful diagnostic criteria for the differentiation of a first episode of MS from monophasic ADEM. The term ADEM may still be employed as a description of a clinical syndrome, but should not be used as a distinct entity until reliable diagnostic criteria have been developed.