Postinfectious inflammatory disorders: Subgroups based on prospective follow-up

Background: Acute disseminated encephalomyelitis (ADEM) refers to a monophasic acute multifocal inflammatory CNS disease. However, both relapsing and site-restricted variants, possibly associated with peripheral nervous system (PNS) involvement, are also observed, and a systematic classification is lacking. Objective: To describe a cohort of postinfectious ADEM patients, to propose a classification based on clinical and instrumental features, and to identify subgroups of patients with different prognostic factors. Methods: Inpatients of a Neurologic and Infectious Disease Clinic affected by postinfectious CNS syndrome consecutively admitted over 5 years were studied. Results: Of 75 patients enrolled, 60 fulfilled criteria for ADEM after follow-up lasting from 24 months to 7 years. Based on lesion distribution, patients were classified as encephalitis (20%), myelitis (23.3%), encephalomyelitis (13.3%), encephalomyeloradiculoneuritis (26.7%), and myeloradiculoneuritis (16.7%). Thirty patients (50%) had a favorable outcome. Fifteen patients (25%) showed a relapsing course. Poor outcome was related with older age at onset, female gender, elevated CSF proteins, and spinal cord and PNS involvement. All but two patients received high-dose steroids as first-line treatment, with a positive response in 39 (67%). Ten of 19 nonresponders (53%) benefited from high-dose IV immunoglobulin; 9 of 10 had PNS involvement. The data were not controlled. Conclusions: A high prevalence of "atypical variants" was found in this series, with site-restricted damage or additional peripheral nervous system (PNS) involvement. Prognosis and response to steroids were generally good, except for some patient subgroups. In patients with PNS involvement and steroid failure, a favorable effect of IV immunoglobulin was observed.