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Acute Disseminated Encephalomyelitis Subgroups Related to Prognosis: Presented at AAN

By Andrew N. Wilner, MD

SEATTLE, Wash -- May 3, 2009 -- Researchers have proposed a new classification of acute disseminated encephalomyelitis that provides prognostic information and identifies subgroups of the disease, it was described here at the American Academy of Neurology (AAN) 61st Annual Meeting.

"One should not rely on the traditional diagnostic criteria of acute disseminated encephalomyelitis, because there are many atypical forms," explained Sabrina Ravaglia, MD, PhD, Institute of Neurology, University of Pavia, Italy, speaking here on April 28. "Examining the subgroups can provide important prognostic information. Patients with pure encephalitis and encephalomyelitis, for example, have the best prognosis, but those with peripheral involvement have the worst."

Dr. Ravaglia and colleagues conducted a prospective study on 116 patients admitted for central nervous system disorders related to an infection or vaccination within the last 30 days. Subjects were treated with high-dose steroids, and intravenous immunoglobulin (IVIG) was added if required. Patients with a history of central nervous system disease, infections, systemic autoimmune disorders, or development of new asymptomatic lesions on follow-up were excluded.

Five syndromes were identified: encephalitis, myelitis, encephalomyelitis, myeloradiculitis, and encephalomyeloradiculitis. Outcome was measured with the Scripps Neurological Rating Scale. Prognostic factors that predicted a good outcome included younger age (50.3 years of age vs 57.2 years of age, P = .029); myelitis, defined as spinal-cord involvement (68% vs 94%, P = .000); lack of peripheral nervous system involvement (13% vs 54%, P = .000); and other measures. Peripheral nervous system involvement was associated with higher onset of disability, higher residual disability, and lack of responsiveness to steroids; however, 50% of patients with peripheral nervous system involvement resistant to steroids benefited from high-dose IVIG.

Patients who failed on steroids were more likely to be older (57.4 years of age vs 51.1 years of age, P = .054), have more cells in the cerebrospinal fluid (CSF) (60.3 vs 24.4, P = .012), have a higher CSF/serum albumin ratio (2.7 vs 1.3, P = .000), and have peripheral nervous system involvement (67% vs 11.8%, P = .000).

Relapses occurred in 31% of patients, occurred within 2 years of the initial event in 90% of subjects, and were usually in the form of myelitis. Peripheral nervous system involvement was also a risk factor for relapse (P = .036), as was myelitis (P = .0001), higher residual disability after the first episode (P = .048), and a higher number of inflammatory cells in the CSF (P = .030).

The classification of postinfectious CNS disorders remains controversial, the research team concluded, but the subgroup distinction allows practitioners to clearly distinguish prognostic factors.

[Presentation title: Acute Disseminated Encephalomyelitis (ADEM): A Prospective Study on 122 Adults. Abstract P03.162]

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