Background Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disorder in which the use of immunotherapy and the long-term outcome have not been defined. Methods In this multi-institutional observational study (2007-2012), all patients with GluN1 antibodies were assessed at symptom onset and 4, 8, 12, 18, and 24 months using the modified Rankin Scale (mRS). Treatment included first-line immunotherapy (steroids, intravenous immunoglobulin, plasmapheresis), second-line immunotherapy (rituximab, cyclophosphamide), and tumor removal. Predictors of outcome were determined at the Universities of Pennsylvania and Barcelona using generalized linear mixed models with binary distribution. Results 577 patients (1-85 years, median 21) were studied, 212 were children (<18 years). Treatment effects and outcome were assessable in 501 (median follow-up 24 months): 472 (94%) underwent first-line immunotherapy or tumor removal, resulting in improvement within four weeks in 251 (53%). Of 221 patients who failed first-line therapy, 125 (57%) received second-line immunotherapy resulting in better outcome than those who did not (OR 2·69, CI 1·24-5·80, p=0·012). During the first 24 months, 394/501 reached good outcome (mRS 0-2; median 6 months), and 30 died. At 24 month follow-up 204/252 (81%) had good outcome. Outcomes continued to improve for up to 18 months after symptom onset. Predictors of good outcome were early treatment (OR 0·62, CI 0·50-0·76, p<0·0001) and lack of ICU admission (OR 0.12, CI 0·06-0·22,p<0·0001). 45 patients had one or multiple relapses (representing a 12% risk within 2 years); 46/69 (67%) relapses were milder than previous episodes (p<0·0001). In 177 children, predictors of good outcome and the magnitude of effect of second-line immunotherapy were comparable to those of the entire cohort. Conclusions Patients with anti-NMDAR encephalitis respond to immunotherapy. Second-line immunotherapy is usually effective when first-line therapies fail. Recovery can take more than 18 months.

Encephalitis is a severe inflammatory disorder of the brain with many possible causes and a complex differential diagnosis. Advances in autoimmune encephalitis research in the past 10 years have led to the identification of new syndromes and biomarkers that have transformed the diagnostic approach to these disorders. However, existing criteria for autoimmune encephalitis are too reliant on antibody testing and response to immunotherapy, which might delay the diagnosis. We reviewed the literature and gathered the experience of a team of experts with the aims of developing a practical, syndrome-based diagnostic approach to autoimmune encephalitis and providing guidelines to navigate through the differential diagnosis. Because autoantibody test results and response to therapy are not available at disease onset, we based the initial diagnostic approach on neurological assessment and conventional tests that are accessible to most clinicians. Through logical differential diagnosis, levels of evidence for autoimmune encephalitis (possible, probable, or definite) are achieved, which can lead to prompt immunotherapy.

Summary Background Some encephalitides or seizure disorders once thought idiopathic now seem to be immune mediated. We aimed to describe the clinical features of one such disorder and to identify the autoantigen involved. Methods 15 patients who were suspected to have paraneoplastic or immune-mediated limbic encephalitis were clinically assessed. Confocal microscopy, immunoprecipitation, and mass spectrometry were used to characterise the autoantigen. An assay of HEK293 cells transfected with rodent GABAB1 or GABAB2 receptor subunits was used as a serological test. 91 patients with encephalitis suspected to be paraneoplastic or immune mediated and 13 individuals with syndromes associated with antibodies to glutamic acid decarboxylase 65 were used as controls. Findings All patients presented with early or prominent seizures; other symptoms, MRI, and electroencephalography findings were consistent with predominant limbic dysfunction. All patients had antibodies (mainly IgG1) against a neuronal cell-surface antigen; in three patients antibodies were detected only in CSF. Immunoprecipitation and mass spectrometry showed that the antibodies recognise the B1 subunit of the GABAB receptor, an inhibitory receptor that has been associated with seizures and memory dysfunction when disrupted. Confocal microscopy showed colocalisation of the antibody with GABAB receptors. Seven of 15 patients had tumours, five of which were small-cell lung cancer, and seven patients had non-neuronal autoantibodies. Although nine of ten patients who received immunotherapy and cancer treatment (when a tumour was found) showed neurological improvement, none of the four patients who were not similarly treated improved (p=0.005). Low levels of GABAB1 receptor antibodies were identified in two of 104 controls (p<0.0001). Interpretation GABAB receptor autoimmune encephalitis is a potentially treatable disorder characterised by seizures and, in some patients, associated with small-cell lung cancer and with other autoantibodies. Funding National Institutes of Health.

1) These findings indicate that "juvenile acute nonherpetic encephalitis" or a subset of this disorder is mediated by an antibody-associated immune response against NR1/NR2 heteromers of the NMDA receptor (NMDAR). 2) Our patients' clinical features emphasize that anti-NMDAR encephalitis is severe but potentially reversible and may precede by years the detection of an ovarian teratoma. 3) Although recovery may occur without tumor removal, the severity and extended duration of symptoms support tumor removal.

Objective To report the clinical, radiological, and immunological association of demyelinating disorders with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Methods Clinical and radiological analysis of a cohort of 691 patients with anti-NMDAR encephalitis. Determination of antibodies to NMDAR, aquaporin-4 (AQP4) and myelin oligodendrocyte glycoprotein (MOG) was performed using brain immunohistochemistry and cell-based assays. Results Twenty-three of 691 patients with anti-NMDAR encephalitis had prominent MRI and/or clinical features of demyelination. Group 1 included 12 patients in whom anti-NMDAR encephalitis was preceded or followed by independent episodes of NMO-spectrum disorder (5 cases, 4 anti-AQP4-positive), or brainstem or multifocal demyelinating syndromes (7 cases, all anti-MOG-positive). Group 2 included 11 patients in whom anti-NMDAR encephalitis occurred simultaneously with MRI and symptoms compatible with demyelination (5 AQ4-positive, 2 MOG-positive). Group 3 (136 controls) included 50 randomly selected patients with typical anti-NMDAR encephalitis, 56 with NMO, and 30 with multiple sclerosis: NMDAR-antibodies were detected only in the 50 anti-NMDAR patients, MOG-antibodies in 3/50 anti-NMDAR and 1/56 NMO patients, and AQP4-antibodies in 48/56 NMO and 1/50 anti-NMDAR patients (p<0.0001 for all comparisons with Groups 1 and 2). Most patients improved with immunotherapy, but compared with anti-NMDAR encephalitis the demyelinating episodes required more intensive therapy and resulted in more residual deficits. Only 1/23 NMDAR patients with signs of demyelination had ovarian teratoma compared with 18/50 anti-NMDAR controls (p=0.011) Interpretation Patients with anti-NMDAR encephalitis may develop concurrent or separate episodes of demyelinating disorders, and conversely patients with NMO or demyelinating disorders with atypical symptoms (e.g., dyskinesias, psychosis) may have anti-NMDAR encephalitis.

Objective: To describe the clinical features and outcome of anti-NMDA receptor (NMDAR) encephalitis in patients $45 years old.Method: Observational cohort study.Results: In a cohort of 661 patients with anti-NMDAR encephalitis, we identified 31 patients $45 years old. Compared with younger adults (18-44 years), older patients were more often male (45% vs 12%, p , 0.0001), had lower frequency of tumors (23% vs 51%, p 5 0.002; rarely teratomas), had longer median time to diagnosis (8 vs 4 weeks, p 5 0.009) and treatment (7 vs 4 weeks, p 5 0.039), and had less favorable outcome (modified Rankin Scale score 0-2 at 2 years, 60% vs 80%, p , 0.026). In multivariable analysis, younger age (odds ratio [OR] Conclusions: Anti-NMDAR encephalitis is less severe in patients $45 years old than in young adults, but the outcome is poorer in older patients. In this age group, delays in diagnosis and treatment are more frequent than in younger patients. The frequency of underlying tumors is low, but if present they are usually carcinomas instead of teratomas in younger patients. Early and aggressive immunotherapy will likely improve the clinical outcome. Anti-NMDA receptor (NMDAR) encephalitis is an autoimmune disorder that usually affects children and young adults, resulting in severe neuropsychiatric symptoms that often respond to treatment. [1][2][3][4] Experience with older patients is limited to a single case report 5 and series comprising patients of all ages, but no further information is available. We report a detailed clinical analysis of 31 patients $45 years old and describe several novel features associated with this age group.METHODS Patients with immunoglobulin G antibodies against the NR1 subunit of NMDAR were identified from a series of 661 cases with anti-NMDAR encephalitis.2 Detailed information on patients $45 years old, either as individual cases or age group, has not been reported previously. We used 45 years as the cutoff age because a similar threshold has been used in other autoimmune neurologic disorders, like myasthenia gravis. Clinical information was obtained by the authors or referring physicians at the acute stage of the disease.2 Follow-up information was obtained at regular intervals after symptom onset; neurologic status was assessed with the modified Rankin Scale (mRS) score. 6 Initial treatment was considered a failure if no sustained improvement occurred within 4 weeks after initiation of immunotherapy or tumor removal, and if the mRS score remained $4.2 Serum and CSF antibody studies were conducted as reported. Demographic information and symptoms were analyzed with the Fisher exact test, Fisher-Freeman-Halton test, or Mann-Whitney U test when appropriate, comparing these 31 patients with 338 recently reported patients (aged 18-44 years).

The stroke-like episodes in MELAS may reflect neuronal hyperexcitability, which increases energy demand and creates energy imbalance between energy requirement and adequate availability of adenosine triphosphate due to oxidative phosphorylation defect particularly in the susceptible neuronal population, causing cortical necrosis. The episodic nature of stroke-like episodes is unexplained.

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