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Purpose of Review: Serum IgG autoantibodies against the myelin oligodendrocyte glycoprotein (MOG) are present in atypical demyelinating disorders such as neuromyelitis optica spectrum disorders (NMOSD) or acute disseminated encephalomyelitis. Whereas the role of aquaporin-4 antibodies as diagnostic markers for NMOSD is meanwhile well established, the role of MOG antibodies is less clear., Recent Findings: Initial studies suggested that MOG antibodies are associated with a more benign disease course than aquaporin-4antibodies. However, recent findings challenged this view. Data from the two largest cohorts of adult MOG antibody-positive patients with the longest clinical follow-up published so far indicate that the majority of patients develop a recurrent disease course with optic neuritis as the most frequent symptom, particularly in women. Frequent attacks are often associated with accumulating damage and functional impairment. The clinical spectrum of acquired demyelinating syndromes associated with MOG antibodies seems to be broader as anticipated in prior studies, with only a third of patients fulfilling the current diagnostic criteria for NMOSD., Summary: MOG antibodies are associated with an increasing spectrum of age and sex-dependent clinical phenotypes, only partly overlapping with NMOSD and multiple sclerosis and with a high risk of a recurrent disease course.

Elucidating pathophysiologic mechanisms underlying the spectrum of pediatric-onset CNS demyelinating diseases, particularly those that may distinguish multiple sclerosis (MS) from other entities, promises to both improve diagnostics and guide more-informed therapeutic decisions. Observations that pediatric- and adult-onset MS share the same genetic and environmental risk factors support the view that these conditions represent essentially the same illness manifesting at different ages. Nonetheless, special consideration must be given when CNS inflammation manifests in early life, at a time when multiple organs (including immune and nervous systems) are actively maturing. CSF analysis in pediatric-onset MS points to chronic CNS inflammation, supported by observations from limited pathologic material available for study. Emerging results implicate abnormalities in both effector and regulatory T cell subsets, and potentially immune senescence, in children with MS. Although CNS-directed antibodies (including antibodies recognizing myelin antigens; Kir4.1) can be documented in pediatric-onset MS, their pathophysiologic significance (as in adults) remains unclear. This is in contrast to the presence of serum and/or CSF antibodies recognizing aquaporin-4, which, when measured using validated cell-based assays, supports the diagnosis of a neuromyelitis optica spectrum disorder, distinct from MS. Presence of anti-myelin oligodendrocyte glycoprotein antibodies documented with similar cell-based assays may also be associated with pathophysiologically distinct disease phenotypes in children. The substantial impact of pediatric-onset MS on normal brain development and function underscores the importance of elucidating both the immunobiology and neurobiology of disease. Ongoing efforts are aimed at developing and validating biological measures that define pathophysiologically distinct monophasic and chronic forms of pediatric CNS demyelination., (© 2016 American Academy of Neurology.)

Major advances have been made in the clinical and radiologic characterization of children presenting with the different forms of an acquired inflammatory demyelinating syndrome (ADS) such as acute disseminating encephalomyelitis, neuromyelitis optica spectrum disorders, and clinically isolated syndromes. Nevertheless, a proportion of cases that present with similar symptoms are due to a broad spectrum of other inflammatory disorders affecting the white matter, primary CNS tumors, or neurometabolic diseases. The clinician therefore has to be aware of the different forms of ADS, the risk factors for a chronic-relapsing course, and features that indicate an alternative diagnosis. The goal of this article is therefore to provide an outline of a pathway for evaluating pediatric patients with a presumed inflammatory demyelinating disorder and discussing the spectrum of the more common differential diagnoses., (© 2016 American Academy of Neurology.)

Neuromyelitis optica (NMO) is a severe autoimmune disease of the CNS characterized by recurrent inflammatory events primarily involving the optic nerves and spinal cord. NMO is infrequent in children, but early recognition is important to start adequate treatment. In this article, we review the evolving diagnostic criteria of NMO and provide an update on the clinical and neuroimaging spectrum of the disorder in pediatric patients, including current knowledge on immunopathogenesis and treatment recommendations for children with NMO., (© 2016 American Academy of Neurology.)

Objective: To report 14 patients with immune-mediated relapsing symptoms post-herpes simplex encephalitis (HSE) and to compare the clinical and immunologic features of the teenage and adult group with those of young children., Methods: Prospective observational study of patients diagnosed between June 2013 and February 2015. Immunologic techniques have been reported previously., Results: Among the teenage and adult group (8 patients, median age 40 years, range 13-69; 5 male), 3 had an acute symptom presentation suggesting a viral relapse, and 5 a presentation contiguous with HSE suggesting a recrudescence of previous deficits. Seven patients developed severe psychiatric/behavioral symptoms disrupting all social interactions, and one refractory status epilepticus. Blepharospasm occurred in one patient. Five patients had CSF antibodies against NMDA receptor (NMDAR) and 3 against unknown neuronal cell surface proteins. In 5/6 patients, the brain MRI showed new areas of contrast enhancement that decreased after immunotherapy and clinical improvement. Immunotherapy was useful in 7/7 patients, sometimes with impressive recoveries, returning to their baseline HSE residual deficits. Compared with the 6 younger children (median age 13 months, range 6-20, all with NMDAR antibodies), the teenagers and adults were less likely to develop choreoathetosis (0/8 vs 6/6, p < 0.01) and decreased level of consciousness (2/8 vs 6/6, p < 0.01) and had longer delays in diagnosis and treatment (interval relapse/antibody testing 85 days, range 17-296, vs 4 days, range 0-33, p = 0.037)., Conclusion: In teenagers and adults, the immune-mediated relapsing syndrome post-HSE is different from that known in young children as choreoathetosis post-HSE and is underrecognized. Prompt diagnosis is important because immunotherapy can be highly effective., (© 2015 American Academy of Neurology.)

Objective: A serum antibody against the inward rectifying potassium channel KIR4.1 (KIR4.1-IgG) was recently discovered, which is found in almost half of adult patients with multiple sclerosis. We investigated the prevalence of KIR4.1-IgG in children with acquired demyelinating disease (ADD) of the CNS. We also compared antibody responses to KIR4.1 and myelin oligodendrocyte glycoproteins (MOGs), another potential autoantigen in childhood ADDs., Methods: We measured KIR4.1-IgG by ELISA in children with ADD (n = 47), other neurologic disease (n = 22), and autoimmune disease (n = 22), and in healthy controls (HCs) (n = 18). One hundred six samples were also measured by capture ELISA. Binding of KIR4.1-IgG human subcortical white matter was analyzed by immunofluorescence. Anti-MOG antibodies were measured using a cell-based assay., Results: KIR4.1-IgG titers were significantly higher in children with ADD compared with all control groups by ELISA and capture ELISA (p < 0.0001, p < 0.0001). Overall, 27 of 47 patients with ADD (57.45%) but none of the 62 with other neurologic disease or autoimmune disease or the HCs (0%) were KIR4.1-IgG antibody positive by ELISA. Sera containing KIR4.1-IgG stained glial cells in brain tissue sections. No correlation among KIR4.1-IgG, age, or MOG-IgG was observed in the ADD group., Conclusion: Serum antibodies to KIR4.1 are found in the majority of children with ADD but not in children with other diseases or in HCs. These findings suggest that KIR4.1 is an important target of autoantibodies in childhood ADD.

Objectives: To determine the frequency of KCNQ2 mutations in patients with neonatal epileptic encephalopathy (NEE), and to expand the phenotypic spectrum of KCNQ2 epileptic encephalopathy., Methods: Eighty-four patients with unexplained NEE were screened for KCNQ2 mutations using classic Sanger sequencing. Clinical data of 6 additional patients with KCNQ2 mutations detected by gene panel were collected. Detailed phenotyping was performed with particular attention to seizure frequency, cognitive outcome, and video-EEG., Results: In the cohort, we identified 9 different heterozygous de novo KCNQ2 missense mutations in 11 of 84 patients (13%). Two of 6 missense mutations detected by gene panel were recurrent and present in patients of the cohort. Seizures at onset typically consisted of tonic posturing often associated with focal clonic jerking, and were accompanied by apnea with desaturation. One patient diagnosed by gene panel had seizure onset at the age of 5 months. Based on seizure frequency at onset and cognitive outcome, we delineated 3 clinical subgroups, expanding the spectrum of KCNQ2 encephalopathy to patients with moderate intellectual disability and/or infrequent seizures at onset. Recurrent mutations lead to relatively homogenous phenotypes. One patient responded favorably to retigabine; 5 patients had a good response to carbamazepine. In 6 patients, seizures with bradycardia were recorded. One patient died of probable sudden unexpected death in epilepsy., Conclusion: KCNQ2 mutations cause approximately 13% of unexplained NEE. Patients present with a wide spectrum of severity and, although rare, infantile epilepsy onset is possible.