Incidence of acute disseminated encephalomyelitis in the Jiangsu province of China, 2008–2011

Chen, Yong; Ma, Fubao; Xu, Yuanling; Chu, Xuhua; Zhang, Jinlin

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated central nervous system (CNS) disorder. 1 It is characterized by an acute encephalopathy with polyfocal neurological deficits. In the absence of specific biological markers the diagnosis of ADEM is still based on clinical features and magnetic resonance imaging (MRI) evidence of widespread demyelination, after ruling out other possible explanations for an acute encephalopathy. 2 In 2007 the International Pediatric Multiple Sclerosis (MS) Study Group proposed a consensus definition for ADEM for application in research and clinical settings. 3 The pathogenesis of ADEM is not fully known, but adhesion molecules, chemokines, matrix metalloproteinase, and other cell factors can play important roles in its occurrence and development. 4 Formerly, ADEM occurred particularly often in children with measles. However, the disease most often follows a nondescript viral or even bacterial infectious illness. Many identifiable infections have been associated with ADEM, such as measles, mumps, rubella, coxsackie, coronavirus, herpes, influenza A and B, hepatitis A and B, human T-lymphotropic virus-1, human immunodeficiency virus, dengue virus, or smallpox. 5 In addition to a known association with infections, vaccinations (e.g. rabies, smallpox or measles vaccines) have also been suggested to increase the risk of ADEM. 6 There have been many recent studies showing no long-term association between vaccinations and ADEM. 7 In recent years, the Expanded Program on Immunization (EPI) has been carried out in China. The type and number of vaccines administered to residents were expanded. The probability of having an abnormal reaction such as ADEM to vaccines is small, but the occurrences of such reactions increased after the EPI, causing widespread public concern. This may reduce public confidence in vaccines. When evaluating the risk of vaccines leading to ADEM or when judging whether ADEM has a causal association with vaccination, epidemiological features and population-level baseline incidence rates, in addition to clinical characteristics and disease diagnosis, must be assessed. A firm measure of the incidence of ADEM is increasingly important.