Acute Disseminated Encephalomyelitis: Clinical Features, Pathophysiology, and Clinical Management
Omar Hussein and Alireza Minagar
ADEM is a presumably immune-mediated multifocal or diffuse inflammatory demyelinating disease of the brain and the spinal cord that, often but not always, occurs para-infection or postvaccination. It affects children more commonly than adults but that might be attributed to the more clearly defined diagnostic criteria available for children more than adults who might also have pre-existing white matter lesion(s) secondary to a different pathology leading to underscoring adult ADEM . From certain viewpoints, ADEM resembles MS and other demyelinating diseases; however, significant differences do exist. ADEM occurs worldwide and usually males and females are affected equally, unlike relapsing-remitting MS that is more common among females. However few studies suggested slight male predominance [2-4]. A cornerstone landmark for the diagnosis of ADEM, especially in children, is encephalopathy in the absence of fever along with other manifestation . This is attributed to the early involvement of the cortical gray matter in the course of the disease unlike most other demyelinating conditions in which cortical involvement usually occurs latter as the disease progresses. Gray matter involvement also causes dystonia and other movement disorders . ADEM rarely exists in multiphasic and recurrent forms, but if occurred, encephalopathy remains the cornerstone. To date, there is no unique biomarker that exists to distinguish ADEM from other demyelinating or non-demyelinating conditions making it mostly a diagnosis of exclusion . Pathological differences also do exist between the different autoimmune demyelinating conditions according to biopsy and postmortem tissue analysis . Neuroimaging is, somehow, helpful as ADEM usually presents as multifocal larger lesions or less commonly as a single large confluent white and deep
O. Hussein, MD • A. Minagar, MD (*)
A. Minagar, J.S. Alexander (eds.), Inflammatory Disorders of the Nervous System, Current Clinical Neurology, DOI 10.1007/978-3-319-51220-4_7
gray matter bilateral symmetrical lesion involving the basal ganglia and the thalami that, sometimes but not always, enhance. Despite of this, tumefactive MS and different brain tumors especially gliomas can mimic this presentation making the diagnosis and early initiation of treatment a dilemma. Recently, advances in neuroimaging including MR perfusion, spectroscopy, and susceptibility images have been used to try to differentiate between these conditions. Large randomized studies still lack regarding these attempts. The cornerstone in the treatment of ADEM is early initiation of pulse steroid therapy followed by oral taper. It is crucial to differentiate ADEM from other autoimmune demyelinating conditions as usually ADEM does not require long-term immune modulation or immune suppression, but in some cases, this remains difficult and thus requires close follow-ups for any relapses or new lesions to appear. In some mimicking conditions like lymphoma, early pulse steroid therapy without reaching a definite diagnosis might create a real challenge as this might mask the diagnosis of lymphoma even if brain biopsy is performed later on. Thus, in such challenging suspicious cases, brain biopsy is recommended.