Demyelinating Diseases

Published on 06/06/2015 by admin

Filed under Pediatrics

Last modified 06/06/2015

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78 Demyelinating Diseases

Demyelinating diseases are acquired autoimmune disorders affecting the central nervous system (CNS) in children and adolescents. Presenting with acute neurologic symptoms, these disorders are often difficult to distinguish from each other because of considerable overlap in the clinical presentation, paraclinical tests (e.g., cerebrospinal fluid [CSF] analysis), and neuroimaging features. Although some disorders, such as acute disseminated encephalomyelitis (ADEM), can be self-limited with a generally favorable prognosis, other demyelinating diseases, including multiple sclerosis (MS) and neuromyelitis optica (NMO), are chronic relapsing conditions that are potentially disabling.

Clinical Presentation and Differential Diagnosis

Acute Disseminated Encephalomyelitis

Historically, ADEM was defined by the development of neurologic symptoms after a vaccination or a viral or bacterial infection. In 2007, an International Pediatric MS Study Group (IPMSSG) proposed working definitions for demyelinating disorders in children. ADEM is currently defined as a first demyelinating or inflammatory event in which the child is polysymptomatic and encephalopathic. Encephalopathy can be mild (e.g., confusion or irritability) but must be present to distinguish ADEM from a clinically isolated syndrome (described below). Although a preceding illness or infection is identifiable in approximately 75% of children (with an average latency between the febrile illness and neurologic symptoms of 7-14 days), such an event is not required for the diagnosis. Magnetic resonance imaging (MRI) of the brain typically reveals multiple large (>1-2 cm) asymmetric lesions affecting the supra- and infratentorial white matter that are easily visualized using T2-weighted and fluid-attenuated inversion recovery (FLAIR) sequences. Symmetric gray matter involvement of the thalami and basal ganglia and confluent spinal cord lesions have also been described in ADEM. CSF analysis may demonstrate an elevated white blood cell (WBC) count or protein or the presence of oligoclonal bands, although the latter is more frequent in MS. The presence of encephalopathy, a preceding illness or vaccination, large asymmetric white matter lesions on MRI, symmetric gray matter involvement, and CSF WBC greater than 50 cells/mm are highly suggestive of ADEM rather than a first attack of MS. The clinical and radiographic involvement may fluctuate for the first 3 months. Thereafter, relapses may occur in the same (recurrent ADEM) or a different (multiphasic) CNS site but must meet the diagnostic criteria for ADEM described above to differentiate these conditions from MS.