Acute disseminated encephalomyelitis: a follow-up study in Taiwan

Background

Acute‐disseminated encephalomyelitis (ADEM) is a demyelinating disorder of the central nervous system, whose epidemiology, clinical presentations and functional outcome are incompletely understood in Asian populations.

Objective

To assess the clinical presentations, predisposing factors and functional outcome of ADEM in Taiwan.

Methods

50 patients initially diagnosed with ADEM (male, 19; female, 31) were enrolled from 1991 to 2005. Diagnosis of ADEM or multiple sclerosis was established during a follow‐up period of 2–120 months. 8 adult patients were noted to have taken the immunomodulatory drug, levamisole, within 3 months before onset of symptoms. The remaining 42 patients (male, 17; female, 25) were categorised by age as children (<16 years, n = 12), young adults (16–49 years, n = 21) and elderly adults (⩾50 years, n = 9). The clinical manifestations, predisposing factors and radiological findings were compared between different age groups and adult patients with or without levamisole use. Functional outcome was compared by a log‐rank test.

Results

Preceding upper respiratory tract infection was evident in 21 (50%) patients and only one young‐adult patient had received Rubella vaccine immunisation. The frequency of fever was higher in children (p = 0.04) and psychiatric symptoms were more prevalent in elderly patients (p = 0.03). Functional recovery was faster in children than in adults (p = 0.002). Initial Expanded Disability Status Scale score (odds ratio (OR) 1.9, p = 0.03) and no fever (OR 0.04, p = 0.06) were associated with poor outcome (modified Rankin scale ⩾2). After a mean (SD) follow‐up of 31.8 (9.9) months, 4 (9.5%) patients developed multiple sclerosis (3 (25%) children, 1 (4.7%) young adult, p = 0.03). The neurological disability, radiological and cerebrospinal fluid findings did not differ between patients with and without levamisole use. One elderly adult patient previously receiving levamisole developed multiple sclerosis of relapse‐remitting type after a mean follow‐up period of 36.9 months.

Conclusion

The clinical presentations, functional outcome and risk of developing multiple sclerosis differed between different age groups. Functional recovery was faster in children than in adults. Poor functional outcome was related to initial high Expanded Disability Status Scale score and absence of fever.Acute disseminated encephalomyelitis (ADEM) is a monophasic inflammatory demyelinating disorder of the central nervous system (CNS). Pathogenesis is suspected to be an autoimmune response to myelin, which is triggered by infection or immunisation via molecular mimicry.^1,2 Thus, ADEM may be the clinical counterpart to experimental allergic encephalomyelitis (EAE).³ The exact incidence is not known, but it was reported that the incidence of ADEM among persons aged <20 years residing in San Diego County, California was approximately 0.4/10⁵/year.⁴ More studies have been conducted in paediatric populations than in elderly adults and most reported series were Caucasians.^5,6,7,8 Few large series of ADEM have been published in Asian populations.⁹We thus assessed the precipitating factors, clinical presentations, cerebrospinal fluid (CSF) and radiological findings, and long‐term outcome in a cohort of ethnic Taiwanese patients with ADEM in different age groups, and attempted to determine the prognostic factors for poor functional outcome.