Clinical relevance of voltage-gated potassium channel–complex antibodies in children

Comparison of B Cell Variable Region Gene Segment Characteristics in Neuro-autoantibodies

Autoimmune pediatric neurologic diseases have variable phenotypes and presentations, making diagnosis challenging. The pathologic mechanisms are also distinct, including cell-mediated and Ab-mediated autoimmunity, paraneoplastic syndromes, and postinfectious processes. In recent years a number of studies have described the characteristics of the autoantibodies involved in a number of these diseases. Some of the described Abs use a restricted set of variable gene segments. We sought to compare the Ab characteristics of autoantibodies related to some of the more common disorders to discover whether specific Ab signatures are universally associated with neuroautoimmune diseases. We initially performed a literature review to summarize the Ab characteristics of autoantibodies related to some of the more common disorders, including N-methyl-d-aspartate receptor (NMDAR) and leucine-rich, glioma-inactivated 1 (LGI-1). Next, we performed data analysis from selected studies that sequenced Ig genes to further characterize NMDAR and LGI-1 autoantibodies including CDR3 length distribution, variable gene sequence usage, and isotype use. We found that CDR3 length of NMDAR autoantibodies was normally distributed whereas the CDR3 length distribution of LGI-1 autoantibodies was skewed, suggesting that there is no global structural restriction on types of autoantibodies that can cause encephalitis. We also found that IgG1-IgG3 were the main NMDAR autoantibody isotypes detected, while IgG4 was the major isotype used in autoantibodies from LGI-1 encephalitis. These findings are useful for our understanding of autoimmune encephalitis and will help facilitate better diagnosis and treatment of these conditions in the future.

CHI3L1 in the CSF is a potential biomarker for anti-leucine-rich glioma inactivated 1 encephalitis

Objective

Anti-leucine-rich glioma inactivated 1(LGI1) encephalitis is one rare autoimmune encephalitis which is accompanied by inflammatory responses. (Anti-leucine-rich glioma inactivated 1 (anti-LGI1) encephalitis is an autoimmune disease mediated by inflammatory responses.)This study aimed to investigate the Chitinase 3-like 1(CHI3L1) in anti-LGI1encephalitis patients and evaluate its association with modified Rankin Scale (mRS) score in anti-LGI1 encephalitis at admission and 6 months follow-up.(This study looked into the relationship between Chitinase 3-like 1 (CHI3L1) and the modified Ranking Scale (mRS) score in anti-LGI1 encephalitis patients at admission and 6 months later.).

Methods

Thirty-five patients with anti-LGI1 encephalitis and 22 patients with non-inflammatory neurological disease were enrolled in this study. (We enrolled 35 patients with anti-LGI1 encephalitis and 22 patients with non-inflammatory neurological disease.)Cerebrospinal fluid (CSF) and serum levels of CHI3L1 were measured by enzyme-linked immunosorbent assay. (We quantified CHI3L1 in the serum and cerebrospinal fluid (CSF) by performing an enzyme-linked immunosorbent assay.)Patients were evaluated for mRS score at admission and at 6 months follow-up.(We recorded the mRS score of the patients at admission and 6 months later.).

Results

CHI3L1 levels in CSF and serum were highly elevated in patients with anti-LGI1 encephalitis at admission compared those with the controls.(At admission, patients with anti-LGI1 encephalitis had elevated CHI3L1 levels in the CSF and serum.) Additionally, patients presenting with cognitive impairment had significantly higher CSF CHI3L1 levels and mRS scores than those without cognitive impairment symptoms. Patients presenting with only faciobrachial dystonic seizures at admission had lower CSF CHI3L1 levels than those with other symptoms. Finally, CSF CHI3L1 levels were positively correlated with CSF lactate levels.

Conclusion

CHI3L1 level in CSF is correlated with the severity and prognosis of anti-LGI1 encephalitis. (CSF CHI3L1 levels are correlated with the severity and prognosis of anti-LGI1 encephalitis.).

The serum metabolomic profile of a distinct, inflammatory subtype of acute psychosis

A range of studies suggest that a proportion of psychosis may have an autoimmune basis, but this has not translated through into clinical practice-there is no biochemical test able to accurately identify psychosis resulting from an underlying inflammatory cause. Such a test would be an important step towards identifying who might require different treatments and have the potential to improve outcomes for patients. To identify novel subgroups within patients with acute psychosis we measured the serum nuclear magnetic resonance (NMR) metabolite profiles of 75 patients who had identified antibodies (anti-glycine receptor [GlyR], voltage-gated potassium channel [VGKC], Contactin-associated protein-like 2 [CASPR2], leucine-rich glioma inactivated 1 [LGI1], N-methyl-D-aspartate receptor [NMDAR] antibody) and 70 antibody negative patients matched for age, gender, and ethnicity. Clinical symptoms were assessed using the positive and negative syndrome scale (PANSS). Unsupervised principal component analysis identified two distinct biochemical signatures within the cohort. Orthogonal partial least squared discriminatory analysis revealed that the serum metabolomes of NMDAR, LGI1, and CASPR2 antibody psychosis patients were indistinct from the antibody negative control group while VGKC and GlyR antibody patients had significantly decreased lipoprotein fatty acids and increased amino acid concentrations. Furthermore, these patients had more severe presentation with higher PANSS scores than either the antibody negative controls or the NMDAR, LGI1, and CASPR2 antibody groups. These results suggest that a proportion of patients with acute psychosis have a distinct clinical and biochemical phenotype that may indicate an inflammatory subtype.

Autoimmune Epilepsy - Novel Multidisciplinary Analysis, Discoveries and Insights

Epilepsy affects ~50 million people. In ~30% of patients the etiology is unknown, and ~30% are unresponsive to anti-epileptic drugs. Intractable epilepsy often leads to multiple seizures daily or weekly, lasting for years, and accompanied by cognitive, behavioral, and psychiatric problems. This multidisciplinary scientific (not clinical) 'Perspective' article discusses Autoimmune Epilepsy from immunological, neurological and basic-science angles. The article includes summaries and novel discoveries, ideas, insights and recommendations. We summarize the characteristic features of the respective antigens, and the pathological activity in vitro and in animal models of autoimmune antibodies to: Glutamate/AMPA-GluR3, Glutamate/NMDA-NR1, Glutamate/NMDA-NR2, GAD-65, GABA-R, GLY-R, VGKC, LGI1, CASPR2, and β2 GP1, found in subpopulations of epilepsy patients. Glutamate receptor antibodies: AMPA-GluR3B peptide antibodies, seem so far as the most exclusive and pathogenic autoimmune antibodies in Autoimmune Epilepsy. They kill neural cells by three mechanisms: excitotoxicity, Reactive-Oxygen-Species, and complement-fixation, and induce and/or facilitate brain damage, seizures, and behavioral impairments. In this article we raise and discuss many more topics and new insights related to Autoimmune Epilepsy. 1. Few autoimmune antibodies tilt the balance between excitatory Glutamate and inhibitory GABA, thereby promoting neuropathology and epilepsy; 2. Many autoantigens are synaptic, and have extracellular domains. These features increase the likelihood of autoimmunity against them, and the ease with which autoimmune antibodies can reach and harm these self-proteins. 3. Several autoantigens have 'frenetic character'- undergoing dynamic changes that can increase their antigenicity; 4. The mRNAs of the autoantigens are widely expressed in multiple organs outside the brain. If translated by default to proteins, broad spectrum detrimental autoimmunity is expected; 5. The autoimmunity can precede seizures, cause them, and be detrimental whether primary or epiphenomenon; 6. Some autoimmune antibodies induce, and associate with, cognitive, behavioral and psychiatric impairments; 7. There are evidences for epitope spreading in Autoimmune Epilepsy; 8. T cells have different 'faces' in the brain, and in Autoimmune Epilepsy: Normal T cells are needed for the healthy brain. Normal T cells are damaged by autoimmune antibodies to Glutamate/AMPA GluR3, which they express, and maybe by additional autoantibodies to: Dopamine-R, GABA-R, Ach-R, Serotonin-R, and Adrenergic-R, present in various neurological diseases (summarized herein), since T cells express all these Neurotransmitter receptors. However, autoimmune and/or cytotoxic T cells damage the brain; 9. The HLA molecules are important for normal brain function. The HLA haplotype can confer susceptibility or protection from Autoimmune Epilepsy; 10. There are several therapeutic strategies for Autoimmune Epilepsy.

Clinical features, investigations, and outcomes of pediatric limbic encephalitis: A multicenter study

OBJECTIVES

To describe the clinical presentation, investigations, management, and disease course in pediatric autoimmune limbic encephalitis (LE).

METHODS

In this retrospective observational study, from the UK Childhood Neuroinflammatory Disease network, we identified children from six tertiary centers with LE <18 years old between 2008 and 2021. Clinical and paraclinical data were retrieved from medical records.

RESULTS

Twenty-five children fulfilling LE criteria were identified, with median age of 11 years (IQR 8, 14) and median follow-up of 24 months (IQR 18, 48). All children presented with seizures; 15/25 (60%) were admitted to intensive care. Neuroimaging demonstrated asymmetric mesial temporal changes in 8/25 (32%), and extra-limbic changes with claustrum involvement in 9/25 (38%). None were positive for LGI1/CASPR2 antibodies (Abs), 2/25 were positive for serum anti-NMDAR Abs, and 2/15 positive for anti-Hu Abs; one died from relapsing neuroblastoma. Two children had serum and CSF anti-GAD antibodies. Initial immune therapy included steroids in 23/25 (92%), intravenous immunoglobulin (IVIg) in 14/25 (56%), and plasma exchange in 7/25 (28%). The commonest second-line treatment was rituximab in 15/25 (60%). Median duration of hospital admission was 21 days (IQR 11, 30). At last follow-up, 13/25 (52%) had refractory seizures and 16/25 (64%) had memory impairment. Six children (24%) had modified Rankin Scale (mRS) scores ≥3. There was no significant difference in mRS, or long-term cognitive and epilepsy outcomes in those who received rituximab versus those who did not.

INTERPRETATION

A diagnosis of autoimmune LE was associated with significant morbidity and adverse outcomes in this pediatric cohort.

Developing Consensus in the Assessment and Treatment Pathways for Autoimmune Encephalitis in Child and Adolescent Psychiatry

Children with a diagnosis of Autoimmune Encephalitis (AE) frequently require multi-disciplinary care in order to mobilize the assessment and treatment necessary for recovery. Institutional and provider practice differences often influence the diagnostic workup and treatment pathways made available to patients. There are a variety of provider coalitions in pediatric rheumatology, internal medicine, and neurology that have been making meaningful progress toward the development of consensus in assessment and treatment approaches to patient care. However, child psychiatry is currently underrepresented in this work in spite of the high psychiatric symptom burden seen in some young patients. The need for consensus is often made visible only with inter-institutional dialogue regarding patient care trajectories. We aim to review key updates in the assessment and treatment of children and adolescents with autoimmune encephalitis during the acute phase, with or without catatonia, and to outline provider perspectives by comparing current treatment models in the United States, Canada, and Europe.

Clinical Features and Outcomes in Pediatric Autoimmune Encephalitis Associated With CASPR2 Antibody

Background: Contactin-associated protein-like 2 (CASPR2) neurological autoimmunity has been associated with various clinical syndromes involving central and peripheral nervous system. CASPR2 antibody-associated autoimmune encephalitis is mostly reported in adults. Analysis of the clinical presentation and prognostic data of CASPR2 antibody-associated autoimmune encephalitis in children remains important. Methods: A single-center retrospective review of children diagnosed with CASPR2 antibody-associated autoimmune encephalitis from June 1st, 2018 to October 31st, 2020. Results: Six patients were identified. The median age was 12 years (range 1.8-14), with an overall male predominance of 83% (5/6). Commonest clinical features were psychiatric symptoms (6/6), movement disorders (4/6), altered consciousness (3/6), sleep disorders (3/6), and headache (3/6). Four patients (4/6) received first-line therapy alone (steroids combined with intravenous immunoglobulins), and two patients (2/6) received second-line therapy (rituximab, mycophenolate mofetil, or cyclophosphamide). All patients showed no peripheral nervous system involvement. One patient had comorbidities with systemic lupus erythematosus. No evidence of neoplastic disease was found in the whole cohort. All patients had favorable outcomes (modified Rankin Score 0-2) with recurrence rate at 0%, respectively. Conclusion: CASPR2 antibody-associated autoimmune encephalitis is rare in children. Our findings suggest that this type of encephalitis seems to occur more frequently in older children. Patients respond well to immunotherapy and usually demonstrate a favorable clinical outcome. Associated tumors are extremely rare.

Neuropsychiatric Disorders Due to Limbic Encephalitis: Immunologic Aspect

Limbic encephalitis (LE) is a rare cause of encephalitis presenting as an acute and subacute onset of neuropsychiatric manifestations, particularly with memory deficits and confusion as core features, along with seizure occurrence, movement disorders, or autonomic dysfunctions. LE is caused by neuronal antibodies targeting the cellular surface, synaptic, and intracellular antigens, which alter the synaptic transmission, especially in the limbic area. Immunologic mechanisms involve antibodies, complements, or T-cell-mediated immune responses in different degree according to different autoantibodies. Sensitive cerebrospinal fluid markers of LE are unavailable, and radiographic findings may not reveal a typical mesiotemporal involvement at neurologic presentations; therefore, a high clinical index of suspicions is pivotal, and a neuronal antibody testing is necessary to make early diagnosis. Some patients have concomitant tumors, causing paraneoplastic LE; therefore, tumor survey and treatment are required in addition to immunotherapy. In this study, a review on the molecular and immunologic aspects of LE was conducted to gain awareness of its peculiarity, which we found quite different from our knowledge on traditional psychiatric illness.

Clinical characteristics of patients double positive for CASPR2 and LGI1-antibodies

OBJECTIVES

This study described the clinical characteristics of autoimmune neurological diseases with dual seropositive antibodies of CASPR2 and LGI1.

PATIENTS AND METHODS

Three patients, with antibodies targeting both CASPR2 and LGI1 (EUROIMMUN, FA 112d-1, Germany), hospitalized in Department of Neurology, Xuanwu Hospital, Capital Medical University from June 2016 to June 2019 were collected in this study. We summarized the clinical characteristics of patients with CASPR2 and LGI1 antibodies from a targeted literature review.

RESULTS

Three patients reported were all middle-aged and elderly male with diverse neurological symptoms, including seizures, psychological abnormalities, limb weakness and hyperhidrosis. Interestingly, three patients displayed three different clinical syndromes (isolated epilepsy, Morvan syndrome and limbic encephalitis, respectively). White blood cell and glucose in Cerebrospinal fluid (CSF) were normal and CSF for protein was slightly elevated. Electromyography (EMG) showed abnormal spontaneous firing in case 2. Brain magnetic resonance imaging (MRI) revealed bilateral hyper-intensity of the temporal lobe on T2 and FLAIR sequence in case 3. Cancer screening program of patient 2 showed thymoma. Cell based assay was positive in serum for both LGI1 and CASPR2 antibodies, while these antibodies were negative in CSF. They were treated with glucocorticoid or intravenous immunoglobulin (IVIG). Followed up for 6 months to 1 year, all patients got remission to different extent.

CONCLUSION

Through the detailed analysis of three patients, the combination of both antibodies contributes to a broad spectrum of neurological symptoms in the central, peripheral, and autonomic nervous systems. The patients with same antibodies can have different clinical syndromes. Early tumor screening and immunotherapy will improve the prognosis of the disease.

Seizures in Children

Epilepsy is one of the most common neurologic disorders seen in children, with the highest incidence in the first year of life. Diagnostic accuracy can be challenging because many seizure mimics must be considered. Electroencephalography and neuroimaging can be critical in determining etiology and syndrome. Genetic testing is a high-yield endeavor, particularly in early-life epilepsies. Up to one-fourth of children with epilepsy will develop drug-resistant seizures. Comorbidities are very common in children with epilepsy, including intellectual disability in 25% and learning disability and attention-deficit/hyperactivity disorder in a significant minority. These comorbidities must be recognized and addressed as part of the child's overall care.

A Tale of Two Brothers: Familial Voltage-Gated Potassium Channel Autoimmune Encephalitis

This is the first reported case of familial voltage-gated potassium channel (VGKC) autoimmune encephalitis. The symptoms of autoimmune encephalitis can mimic infectious encephalitis with headache, fatigue, and neuropsychiatric symptoms. Autoimmunity is emerging as a distinct cause of encephalitis in the children. Prompt recognition, diagnosis, and treatment are important to prevent brain damage. Two brothers presented two years apart with different symptoms. The explanation for their distinct symptoms lies in the multifactorial development of autoimmunity. The presentation of autoimmune encephalitis can depend on the offending antibodies. The most common are antibodies against the N-methyl-D-aspartic acid (NMDA) receptor and the VGKC complex. Antibodies to the VGKC complex are divided into three different groups depending on their antigenic target: leucine-rich glioma-inactivated protein 1 (LGI1), contactin-associated protein-like 2 (CASPR2), or neither. Anti-VGKC antibodies in children are associated with neuroinflammation and encephalitis. Autoimmunity to LGI1 and CASPR2 antigens is associated with distinct human leukocyte antigen (HLA) alleles. Different HLA isotypes are involved in antigen processing and presentation and can lead to a genetic predisposition to autoimmunity. VGKC autoimmune encephalitis can present with memory changes, psychiatric symptoms, and motor abnormalities. Both brothers presented with these symptoms in their own unique way. Efficient diagnosis and immunosuppression helped improve their outcomes.

Infectious and Autoimmune Causes of Encephalitis in Children

BACKGROUND AND OBJECTIVES

Encephalitis can result in neurologic morbidity and mortality in children. Newly recognized infectious and noninfectious causes of encephalitis have become increasingly important over the past decade.

METHODS

We retrospectively reviewed medical records from pediatric patients in Houston diagnosed with encephalitis in both an urban and rural catchment area between 2010 and 2017. We conducted an investigation to understand the etiology, clinical characteristics, and diagnostic testing practices in this population.

RESULTS

We evaluated 231 patients who met the case definition of encephalitis, among which 42% had no recognized etiology. Among those with an identified etiology, the most common were infectious (73; 31%), including viral (n = 51; 22%), with the most frequent being West Nile virus (WNV; n = 12), and bacterial (n = 19; 8%), with the most frequent being Bartonella henselae (n = 7). Among cases of autoimmune encephalitis (n = 60; 26%), the most frequent cause was anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis (n = 31). Autoimmune causes were seen more commonly in female (P < .01) patients. Testing for herpes simplex virus and enterovirus was nearly universal; testing for anti-NMDAR encephalitis, WNV, and Bartonella was less common.

CONCLUSIONS

WNV was the most common infectious cause of encephalitis in our pediatric population despite lower testing frequency for WNV than herpes simplex virus or enterovirus. Increasing testing for anti-NMDAR encephalitis resulted in frequent identification of cases. Increased awareness and testing for WNV and Bartonella would likely result in more identified causes of pediatric encephalitis. Earlier etiologic diagnosis of encephalitides may lead to improve clinical outcomes.

CASPR2 autoimmunity in children expanding to mild encephalopathy with hypertension

OBJECTIVE

To delineate autoimmune disease in association with contactin-associated protein 2 (CASPR2) antibodies in childhood, we reviewed the clinical phenotype of children with CASPR2 antibodies.

METHODS

Retrospective assessment of patients recruited through laboratories specialized in autoimmune CNS disease.

RESULTS

Ten children with serum CASPR2 antibodies were identified (age at manifestation 18 months to 17 years). Eight children with CASPR2 antibody titers from ≥1:160 to 1:5,120 had complex autoimmune diseases with an age-dependent clinical phenotype. Two children with structural epilepsy due to CNS malformations harbored nonspecific low-titer CASPR2 antibodies (serum titers 1:80). The clinical symptoms of the 8 children with high-titer CASPR2 antibodies were general weakness (8/8), sleep dysregulation (8/8), dysautonomia (8/8) encephalopathy (7/8), neuropathic pain (7/8), neuromyotonia (3/8), and flaccid paresis (3/8). Adolescents (3/8) showed pain, neuromyotonia, and encephalopathy, whereas younger children (5/8) displayed severe hypertension, encephalopathy, and hormonal dysfunction mimicking a systemic disease. No tumors were identified. Motor symptoms remitted with immunotherapy. Mild behavioral changes persisted in 1 child, and autism spectrum disorder was diagnosed during follow-up in a young boy.

CONCLUSION

High-titer CASPR2 antibodies are associated with Morvan syndrome in children as young as 2 years. However, CASPR2 autoimmunity mimics systemic disease and hypertensive encephalopathy in children younger than 7 years. The outcome following immunotherapy was mostly favorable; long-term behavioral impairment may occur in younger children.

Pediatric autoimmune encephalitis: Recognition and diagnosis

Objective

The aims of this study were (1) to describe the incidence of autoimmune encephalitis (AIE) and acute disseminated encephalomyelitis (ADEM) in children, (2) to validate the currently used clinical criteria to diagnose AIE, and (3) to describe pitfalls in the diagnosis of pediatric autoimmune (AI) and inflammatory neurologic disorders.

Methods

This study cohort consists of 3 patient categories: (1) children with antibody-mediated AIE (n = 21), (2) children with ADEM (n = 32), and (3) children with suspicion of an AI etiology of their neurologic symptoms (n = 60). Baseline and follow-up clinical data were used to validate the current guideline to diagnose AIE. In addition, patient files and final diagnoses were reviewed.

Results

One-hundred three of the 113 included patients fulfilled the criteria of possible AIE. Twenty-one children had antibody-mediated AIE, of whom 19 had anti-N-methyl-D-aspartate receptor (NMDAR), 1 had anti–α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, and 1 had anti–leucine-rich glioma-inactivated protein 1 encephalitis. Finally, 34 children had ADEM, and 2 children had Hashimoto encephalopathy. Mean incidence rates were 1.54 children/million (95% CI 0.95–2.35) for antibody-mediated AIE and 2.49 children/million (95% CI 1.73–3.48) for ADEM. Of the other 48 children, treating physicians' diagnoses were reviewed. In 22% (n = 6) of children initially diagnosed as having an AI/inflammatory etiology (n = 27), no support for AI/inflammation was found.

Conclusion

Besides anti-NMDAR encephalitis and ADEM, other AIEs are rare in children. The current guideline to diagnose AIE is also useful in children. However, in children with nonspecific symptoms, it is important to review data critically, to perform complete workup, and to consult specialized neuroinflammatory centers.

Clinical approach to the diagnosis of autoimmune encephalitis in the pediatric patient

Objective

Autoimmune encephalitis (AE) is an important and treatable cause of acute encephalitis. Diagnosis of AE in a developing child is challenging because of overlap in clinical presentations with other diseases and complexity of normal behavior changes. Existing diagnostic criteria for adult AE require modification to be applied to children, who differ from adults in their clinical presentations, paraclinical findings, autoantibody profiles, treatment response, and long-term outcomes.

Methods

A subcommittee of the Autoimmune Encephalitis International Working Group collaborated through conference calls and email correspondence to consider the pediatric-specific approach to AE. The subcommittee reviewed the literature of relevant AE studies and sought additional input from other expert clinicians and researchers.

Results

Existing consensus criteria for adult AE were refined for use in children. Provisional pediatric AE classification criteria and an algorithm to facilitate early diagnosis are proposed. There is also discussion about how to distinguish pediatric AE from conditions within the differential diagnosis.

Conclusions

Diagnosing AE is based on the combination of a clinical history consistent with pediatric AE and supportive diagnostic testing, which includes but is not dependent on antibody testing. The proposed criteria and algorithm require validation in prospective pediatric cohorts.

Association of Leucine-Rich Glioma Inactivated Protein 1, Contactin-Associated Protein 2, and Contactin 2 Antibodies With Clinical Features and Patient-Reported Pain in Acquired Neuromyotonia

Questions

Which specific targets of voltage-gated potassium channel–complex antibodies are found in acquired neuromyotonia, and are these antibodies associated with additional clinical features of tumors, pain, or autonomic or central disorders?

Findings

This cohort study combined with a patient-led survey found that antibodies to the extracellular aspects of leucine-rich glioma inactivated protein, contactin-associated protein 2, and contactin 2 were variably present in 45% of patients with neuromyotonia. Paresthesia and various pain manifestations were common in neuromyotonia, and the type and severity of pain were found to exert a substantial influence on quality of life.

Meaning

Antibodies to voltage-gated potassium channel–complex proteins are not found in all patients with neuromyotonia and do not individually relate to specific clinical features, but the presence of pain and its effects on quality of life need greater recognition.

Importance

Although acquired autoimmune neuromyotonia (NMT) is associated with voltage-gated potassium channel (VGKC)–complex antibodies, to date there has been no systematic study of autoantibodies to the specific antigens leucine-rich glioma inactivated protein 1 (LGI1), contactin-associated protein 2 (CASPR2), and contactin 2 together with the full clinical syndrome, particularly pain and autonomic and central nervous system involvement.

Objectives

To study the full spectrum of clinical features and serum autoantibodies in patients with NMT, including the effects of pain on quality of life.

Design, Setting, and Participants

A cohort study of clinical features and serologic testing in 38 patients with electrophysiologically-confirmed NMT, reviewed clinically between February 2007 and August 2009, in the Universities of Sydney and Kagoshima and followed up across 2 to 4 years. Association of NMT with quality of life was researched in an independent, patient-led, online pain survey conducted from April 2012 to May 2012. Serologic analyses were performed in 2012, and final data analysis was performed in 2016.

Main Outcomes and Measures

Clinical data and scores on the modified Rankin Scale (mRS), which measures disability on a range of 0 to 6, with 0 indicating normal and 6 indicating death, before and after treatments were combined with CASPR2, LGI1, and contactin 2 antibody status.

Results

Among the 38-person NMT cohort, 25 (65.8%) were male and the median (range) age was 55 (12-85) years. Twenty-three (60.5%) were Japanese and 15 (39.5%) were of white race/ethnicity. Symptomatic treatments (mainly antiepileptic drugs) were used in most patients with mild disease (12 patients with mRS <3), whereas immunotherapies were successful in most patients with mRS scores greater than 2. Autoantibodies to VGKC-complex antigens (17 patients [45%]), bound to CASPR2 (5 [13%]), contactin 2 (5 patients, 1 with CASPR2 [13%]), LGI1 (2 [5%]), or both LGI1 and CASPR2 (6 [16%]). The last group of 6 patients had high mRS scores (mean [SD], 3.8 [1.7]), thymoma (4 patients), pain (5 patients), autonomic (6 patients) and sleep (5 patients) disturbance, suggesting Morvan syndrome. The 56 responders to the independent patient-led survey reported pain that could be severe, anatomically widespread, and that often resulted in unemployment, domestic problems, and poor quality of life.

Conclusions and Relevance

The cohort study detailed underrecognized aspects of the clinical and serologic spectrum of NMT. The heterogeneity of clinical features and of specific antibodies limit associations, but the common existence of thymoma, pain, and autonomic and central nervous system features, often with both LGI1 and CASPR2 antibodies, should be better recognized to more completely address the range of comorbidities and consequences of the disease regarding quality of life.

LGI1 and CASPR2 neurological autoimmunity in children

The clinical phenotype of leucine-rich glioma-inactivated protein 1 (LGI1) and contactin-associated proteinlike 2 (CASPR2) autoimmunity is well defined in adults. Data for children are limited (<10 cases). Among 13,319 pediatric patients serologically tested for autoimmune neurological disorders (2010-2017), 264 were seropositive for voltage-gated potassium channel-complex-IgG (radioimmunoprecipitation). Only 13 (4.9%) were positive by transfected cell-binding assay for LGI1-IgG (n = 7), CASPR2-IgG (n = 3), or both (n = 3). This is significantly less than in adults. Encephalopathy, seizures, and peripheral nerve hyperexcitability were common, as was coexisting autoimmunity. No faciobrachial dystonic seizures or cancers were identified. Functional neurologic disorders were frequently the initial diagnosis, and immunotherapy appeared beneficial. Ann Neurol 2018;84:473-480.

Pediatric autoimmune encephalitis in Denmark during 2011-17: A nationwide multicenter population-based cohort study

BACKGROUND

The incidence of pediatric autoimmune encephalitis (AIE) is unknown. Our aim was to assess the incidence of pediatric AIE in Denmark 2011-17.

METHODS

In a nationwide population-based setting, we retrieved data on all children tested for AIE before age 18 years. We reviewed medical records in a) children with AIE antibodies (n = 18) to assess whether children fulfilled the AIE consensus criteria, b) children tested negative for AIE antibodies who were registered with an AIE diagnostic code to estimate the incidence of "antibody negative but probable AIE", and c) a reference cohort (n = 596) to determine the positive predictive value of International Classification of Diseases (ICD) codes used for anti-NMDAR encephalitis.

RESULTS

375 children were tested for AIE 2011-17 (median age 11.1 years; 54% girls); 18 children (5%) had AIE antibodies (percentage tested positive): CSF GAD₆₅-IgG (3.1%), plasma NMDAR-IgG (2.8%), CSF NMDAR-IgG (1.8%), plasma GAD₆₅-IgG (1.0%), and plasma CASPR2-IgG (0.4%). Five children fulfilled the criteria for probably/definite anti-NMDAR encephalitis (incidence: 0.07/100,000 person-years; 95% CI = 0.03-0.17), and 4 children with anti-GAD₆₅ associated AIE (incidence = 0.055/100,000 person-years, 95% CI = 0.021-0.15). The incidence of "antibody negative but probable AIE" was 0.055/100,000 person-years (95% CI = 0.021-0.15). The positive predictive value of ICD diagnostic codes used for anti-NMDAR encephalitis was 8%.

CONCLUSIONS

We diagnosed only children with anti-NMDAR, anti-GAD₆₅, and "antibody negative but probable AIE". Before examining AIE antibodies, clinical presentation, paraclinical studies (CSF, EEG, and MRI), and incidence of pediatric AIEs should be considered. Updating the ICD to include AIE codes is warranted.

Understanding Childhood Neuroimmune Diseases of the Central Nervous System

Immune-mediated diseases of the central nervous system (CNS) in childhood are a heterogeneous group of rare conditions sharing the inflammatory involvement of the CNS. This review highlights the growing knowledge of childhood neuroimmune diseases that primarily affect the CNS, outlining the clinical and diagnostic features, the pathobiological mechanisms and genetics, current treatment options, and emerging challenges. The clinical spectrum of these conditions is increasingly expanded, and the underlying mechanisms of dysregulation of the immune system could vary widely. Cell-mediated and antibody-mediated disorders, infection-triggered and paraneoplastic conditions, and genetically defined mechanisms can occur in previously healthy children and can contribute to different stages of the disease. The careful evaluation of the clinical presentation and temporal course of symptoms, the specific neuroimaging and immunological findings, and the exclusion of alternative causes are mandatory in clinical practice for the syndromic diagnosis. A common feature of these conditions is that immunotherapeutic agents could modulate the clinical course and outcomes of the disease. Furthermore, specific symptomatic treatments and comprehensive multidisciplinary care are needed in the overall management. We focus on recent advances on immune-mediated demyelinating CNS disorders, autoimmune encephalitis, interferonopathies, and possible neuroimmune disorders as Rasmussen encephalitis. Better knowledge of these conditions could allow prompt diagnosis and targeted immunotherapy, to decrease morbidity and mortality as well as to improve clinical outcomes, reducing the burden of the disease due to possible long-term neuropsychiatric sequelae. Persisting controversies remain in the rigorous characterization of each specific clinical entity because of the relative rarity in children; moreover, in a large proportion of suspected neuroimmune diseases, the immune "signature" remains unidentified; treatment guidelines are mostly based on retrospective cohort studies and expert opinions; then advances in specific molecular therapies are required. In the future, a better characterization of specific immunological biomarkers may provide a useful understanding of the underlying pathobiological mechanisms of these conditions in order to individualize more tailored therapeutic options and paradigms. Multicenter collaborative research on homogeneous groups of patients who may undergo immunological studies and therapeutic trials could improve the characterization of the underlying mechanisms, the specific phenotypes, and tailored management.

Catatonia in children and adolescents: New perspectives

INTRODUCTION

Catatonia is a rare and severe psychomotor condition in children and adolescents. In the current report, we aimed to review the recent literature.

METHOD

Using a PRISMA approach, we searched MEDLINE between 1982 and 2017 using the keywords 'CATATONIA' and 'CHILD' or 'ADOLESCENT'. In total, we reviewed 130 reports (controlled study, N=4; clinical chart, N=23; case report, N=54; and editorial/review, N=42).

RESULTS

Several aspects seem to be age specific: (1) although the clinical presentation resembles that in adults, some symptoms are important in children and adolescents (e.g., psychomotor regression). (2) Associated disorders are similar to that found in adults; however, schizophrenia is more frequently observed than mood disorder. Additionally, a history of neurodevelopmental disorders maybe encountered. (3) Morbidity and mortality are among the worst in child psychiatry. (4) Underlying organic conditions are highly prevalent (>20% of the cases), and their search is warranted because some diagnoses may result in specific treatments (e.g., immune-suppressor therapy for autoimmune conditions). (5) Symptomatic approaches - high dose of benzodiazepines and electroconvulsive therapy (ECT) - are as efficient in children or adolescents as they are in adults, but this finding needs to be acknowledged because a resistance against the use of ECT or high-dose medication exists among child psychiatrists.

DISCUSSION

Recent advances in child and adolescent catatonia research have offered major improvements in understanding catatonia and in new therapeutic opportunities. The syndrome is rare, but these advances need to be acknowledged in order to direct patients to centers that have developed a specific expertise.

Brain-relevant antibodies in first-episode psychosis: a matched case-control study

BACKGROUND

There has been much recent excitement about the possibility that some cases of psychosis may be wholly due to brain-reactive antibodies, with antibodies to N-methyl-D-aspartate receptor (NMDAR) and the voltage-gated potassium channel (VGKC)-complex reported in a few patients with first-episode psychosis (FEP).

METHODS

Participants were recruited from psychiatric services in South London, UK, from 2009 to 2011 as part of the Genetics and Psychosis study. We conducted a case-control study to examine NMDAR and VGKC-complex antibody levels and rates of antibody positivity in 96 patients presenting with FEP and 98 controls matched for age and sex. Leucine-rich glioma inactiviated-1 (LGI1) and contactin-associated protein (CASPR) antibodies were also measured. Notably, patients with suspicion of organic disease were excluded.

RESULTS

VGKC-complex antibodies were found in both cases (n = 3) and controls (n = 2). NMDAR antibody positivity was seen in one case and one control. Either LGI1-Abs or CASPR2-Abs were found in three cases and three controls. Neuronal antibody staining, consistent with the above results or indicating potential novel antigens, was overall positive in four patients but also in six controls. Overall, antibody positivity was at low levels only and not higher in cases than in controls.

CONCLUSIONS

This case-control study of the prevalence of antibodies in FEP does not provide evidence to support the hypothesis that FEP is associated with an immune-mediated process in a subgroup of patients. Nevertheless, as other bio-clinical factors may influence the effect of such antibodies in a given individual, and patients with organic neurological disease may be misdiagnosed as FEP, the field requires more research to put these findings in context.

Circulating neural antibodies in unselected children with new-onset seizures

OBJECTIVE

The role of autoimmunity and neural antibodies is increasingly recognized in different forms of seizures and epilepsy. Their prevalence in new-onset epilepsy has also recently been the focus of several clinical cohorts in the adult and pediatric population, with positive titers in 10-11% of cases. Our aim was to determine the seropositivity at the first seizure onset in a non-selective group of children.

METHOD

We conducted a prospective multicenter cohort study recruiting children aged 0-16 years with new-onset seizures presenting at the In- and Outpatient Pediatric Neurology Departments of three Children's Hospitals in Switzerland between September 2013 and April 2016. Neural antibodies were screened within the first 6 months of a first seizure and when positive, repeated at 1 month and 6 months follow-up.

RESULTS

A total of 103 children were enrolled with a mean age at presentation of 5 years (range 1 day-15 years 9 months). The majority (n = 75) presented with generalized seizures and 6 had status epilepticus lasting > 30 min. At the time of onset, 55% of patients had fever, 24% required emergency seizure treatment and 27% hospitalization. Epilepsy was diagnosed at follow-up in 18%. No specific antibody was found. Serum antibodies against the VGKC complex, without binding to the specific antigens LGI1 and CASPR2, were found in two patients. Four patients harbored not otherwise characterized antibodies against mouse neuropil.

INTERPRETATION

Specific neural antibodies are rarely found in an unselected population of children that present with a first seizure. Applying an extensive neuronal antibody profile in a child with new-onset seizures does not appear to be justified.

Autoimmune Movement Disorders in Children

Over the last decade, there have been significant advances in the identification, characterization, and treatment of autoimmune neurologic disorders in children. Many of these diseases include a typical movement disorder that can be a powerful aid to diagnosis. Frequently, movement disorders in autoimmune conditions are the sole or among a few presenting symptoms, allowing for earlier diagnosis of an underlying malignancy or systemic autoimmune disease. Given that early detection and treatment with immunotherapy may confer improved outcomes, recognizing these patterns of abnormal movements is essential for child neurologists. The purpose of this review is to summarize the clinical characteristics, diagnosis, and treatment of movement disorders that occur in pediatric autoimmune disorders.

Clinical presentation of anti-N-methyl-d-aspartate receptor and anti-voltage-gated potassium channel complex antibodies in children: A series of 24 cases

OBJECTIVE

The symptomatology and paraclinical findings of antibody-mediated encephalitis, a relatively novel disorder, are still being characterized in adults and children. A high index of suspicion is needed in order to identify these cases among children presenting with various neurological symptoms. The aim of this study is to examine the clinical, demographic and laboratory findings and outcome of children with anti-NMDAR and anti-VGKC encephalitis for any typical or distinctive features.

METHODS

Cases diagnosed with anti-N-Methyl d-aspartate receptor (NMDAR) and anti-voltage gated potassium channel (VGKC) antibody-mediated encephalopathy in four major child neurology centers are described.

RESULTS

In four years, 16 children with NMDAR and 8 children with VGKC antibody-associated disease were identified in the participating centers. The most frequent initial manifestation consisted of generalized seizures and cognitive symptoms in both groups. Movement abnormalities were frequent in anti-NMDAR patients and autonomic symptoms, in anti-VGKC patients. Cerebrospinal fluid (CSF) protein, cell count and IgG index were normal in 9/15 anti-NMDAR and 5/8 anti-VGKC patients tested. EEG and MRI findings were usually nonspecific and non-contributory. The rate and time of recovery was not related to age, sex, acute or subacute onset, antibody type, MRI, EEG or CSF results. Treatment within 3 months of onset was associated with normal neurological outcome.

CONCLUSIONS

Our results suggest anti-NMDAR and VGKC encephalopathies mostly present with non-focal neurological symptoms longer than 3 weeks. In contrast with adult cases, routine CSF testing, MRI and EEG did not contribute to the diagnosis in this series.

Evaluation and Management of Autoimmune Encephalitis: A Clinical Overview for the Practicing Child Psychiatrist

Medical conditions that present with psychiatric symptoms are becoming increasingly well-recognized in response to the emergence of the field of neuroimmunology. As the availability of testing for novel antineuronal antibodies has increased, so too has the clinical awareness of this diagnostic spectrum. Psychiatrists may have little exposure to this area of expertise, yet may be called on to assist in the diagnosis and treatment of patients with complex neuropsychiatric syndromes secondary to autoimmune encephalitis. This article summarizes the evaluation and management of patients with autoimmune encephalitis and describes emerging patterns in phenotype recognition.

Autoantibody-Associated Movement Disorders in Children: Proven and Proposed

Movement disorders secondary to autoantibodies in children represent a rapidly expanding group of conditions. Once considered to be limited to poststreptococcal Sydenham's chorea or rare cases of childhood systemic lupus erythematosus, a variety of antibody-related movement abnormalities are now seen as part of noninfectious autoimmune encephalitis or within an expanding list of postinfectious disorders. In this article, several proposed autoantibody-mediated movement disorders in children are reviewed. In each one, there is a hypothesized antibody biomarker that is believed to be pathogenic and cause the clinical symptoms. As will be discussed, in some, such as anti-NMDA receptor encephalitis, the strength of supporting evidence is strong. In others, antibodies have been identified, but their role as the pathophysiological mechanism remains undetermined. Lastly, there are proposed disorders, such as PANDAS, that are controversial on both a clinical and autoimmune basis.

Autoimmune encephalitis associated with voltage-gated potassium channels-complex and leucine-rich glioma-inactivated 1 antibodies - a national cohort study

BACKGROUND AND PURPOSE

The aim of this study was to describe clinical and paraclinical characteristics of all Danish patients who tested positive for anti-voltage-gated potassium channels (VGKC)-complex, anti-leucine-rich glioma-inactivated 1 (LGI1) and anti-contactin-associated protein-2 antibodies in the serum/cerebrospinal fluid between 2009 and 2013 with follow-up interviews in 2015 and 2016.

METHODS

We evaluated antibody status, symptoms leading to testing, course of disease, suspected diagnosis and time of admission as well as diagnosis and treatment. All magnetic resonance imaging, electroencephalography and ¹⁸ F-fluorodeoxyglucose positron emission tomography scans were re-evaluated by experts in the field.

RESULTS

A total of 28/192 patients tested positive for VGKC-complex antibodies by radioimmunoassay and indirect immunofluorescence; 17 had antibodies to LGI1 and 6/7 of the available cerebrospinal fluids from these patients were seropositive. These 17 patients all had a clinical phenotype appropriate to LGI1 antibodies. The remaining 11 were LGI1 negative (n = 4) or not tested (n = 7). Of these, two had a phenotype consistent with limbic encephalitis. The remaining phenotypes were Guillain-Barré syndrome, Creutzfeldt-Jakob disease, neuromyotonia and anti-N-methyl-D-aspartate receptor encephalitis. Magnetic resonance imaging abnormalities were demonstrated in 69% of the LGI1-positive patients. Two patients with normal magnetic resonance imaging demonstrated temporal lobe hypermetabolism using ¹⁸ F-fluorodeoxyglucose positron emission tomography. Abnormal electroencephalography recordings were found in 86% of the patients. Upon follow-up (median 3.2 years), the median modified Rankin Scale score of anti-LGI1-positive patients was 2 and only two patients reported seizures in the past year.

CONCLUSIONS

Patients diagnosed with anti-LGI1 autoimmune encephalitis increased significantly from 2009 to 2014, probably due to increased awareness. In contrast to seropositive anti-VGKC-complex patients, all anti-LGI1-positive patients presented with a classical limbic encephalitis. The majority of patients recovered well.

Intracellular and non-neuronal targets of voltage-gated potassium channel complex antibodies

OBJECTIVES

Autoantibodies against the extracellular domains of the voltage-gated potassium channel (VGKC) complex proteins, leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-2 (CASPR2), are found in patients with limbic encephalitis, faciobrachial dystonic seizures, Morvan's syndrome and neuromyotonia. However, in routine testing, VGKC complex antibodies without LGI1 or CASPR2 reactivities (double-negative) are more common than LGI1 or CASPR2 specificities. Therefore, the target(s) and clinical associations of double-negative antibodies need to be determined.

METHODS

Sera (n=1131) from several clinically defined cohorts were tested for IgG radioimmunoprecipitation of radioiodinated α-dendrotoxin (¹²⁵I-αDTX)-labelled VGKC complexes from mammalian brain extracts. Positive samples were systematically tested for live hippocampal neuron reactivity, IgG precipitation of ¹²⁵I-αDTX and ¹²⁵I-αDTX-labelled Kv1 subunits, and by cell-based assays which expressed Kv1 subunits, LGI1 and CASPR2.

RESULTS

VGKC complex antibodies were found in 162 of 1131 (14%) sera. 90 of these (56%) had antibodies targeting the extracellular domains of LGI1 or CASPR2. Of the remaining 72 double-negative sera, 10 (14%) immunoprecipitated ¹²⁵I-αDTX itself, and 27 (38%) bound to solubilised co-expressed Kv1.1/1.2/1.6 subunits and/or Kv1.2 subunits alone, at levels proportionate to VGKC complex antibody levels (r=0.57, p=0.0017). The sera with LGI1 and CASPR2 antibodies immunoprecipitated neither preparation. None of the 27 Kv1-precipitating samples bound live hippocampal neurons or Kv1 extracellular domains, but 16 (59%) bound to permeabilised Kv1-expressing human embryonic kidney 293T cells. These intracellular Kv1 antibodies mainly associated with non-immune disease aetiologies, poor longitudinal clinical-serological correlations and a limited immunotherapy response.

CONCLUSIONS

Double-negative VGKC complex antibodies are often directed against cytosolic epitopes of Kv1 subunits and occasionally against non-mammalian αDTX. These antibodies should no longer be classified as neuronal-surface antibodies. They consequently lack pathogenic potential and do not in themselves support the use of immunotherapies.

Methodological Challenges in Protein Microarray and Immunohistochemistry for the Discovery of Novel Autoantibodies in Paediatric Acute Disseminated Encephalomyelitis

Acute disseminated encephalomyelitis (ADEM) is a rare autoimmune-mediated demyelinating disease affecting mainly children and young adults. Differentiation to multiple sclerosis is not always possible, due to overlapping clinical symptoms and recurrent and multiphasic forms. Until now, immunoglobulins reactive to myelin oligodendrocyte glycoprotein (MOG antibodies) have been found in a subset of patients with ADEM. However, there are still patients lacking autoantibodies, necessitating the identification of new autoantibodies as biomarkers in those patients. Therefore, we aimed to identify novel autoantibody targets in ADEM patients. Sixteen ADEM patients (11 seronegative, 5 seropositive for MOG antibodies) were analysed for potential new biomarkers, using a protein microarray and immunohistochemistry on rat brain tissue to identify antibodies against intracellular and surface neuronal and glial antigens. Nine candidate antigens were identified in the protein microarray analysis in at least two patients per group. Immunohistochemistry on rat brain tissue did not reveal new target antigens. Although no new autoantibody targets could be found here, future studies should aim to identify new biomarkers for therapeutic and prognostic purposes. The microarray analysis and immunohistochemistry methods used here have several limitations, which should be considered in future searches for biomarkers.

Pediatric Autoimmune Epileptic Encephalopathies

Pediatric autoimmune epileptic encephalopathies are predominantly characterized by the presence of autoantibodies to the surface of neuronal proteins, for example, N-methyl-d-aspartate (NMDA) receptor antibodies, but also include diseases with non-cell surface antibodies (eg, anti-Hu, glutamic-acid decarboxylase antibodies). In some cases with distinct clinical and para-clinical features, an autoimmune epileptic encephalopathy can be diagnosed without the presence of an antibody and will also respond favorably to immunotherapy. In this review, we summarize the common presentations of pediatric autoimmune epileptic encephalopathies, treatments, and outcomes, and report recent findings in the field of epilepsy, encephalopathy, and the immune system.

Prevalence and clinical characteristics of serum neuronal cell surface antibodies in first-episode psychosis: a case-control study

BACKGROUND

Psychosis is a common presenting feature in antibody-mediated encephalitis, for which prompt recognition and treatment usually leads to remission. We aimed to investigate whether people with circumscribed schizophrenia-like illnesses have such antibodies-especially antibodies against the N-methyl-D-aspartate receptor (NMDAR)-more commonly than do healthy controls.

METHODS

We recruited patients aged 14-35 years presenting to any of 35 mental health services sites across England with first-episode psychosis, less than 6 weeks of treatment with antipsychotic medication, and a score of 4 or more on at least one selected Positive and Negative Syndrome Scale (PANSS) item. Patients and controls provided venous blood samples. We completed standardised symptom rating scales (PANSS, ACE-III, GAF) at baseline, and tested serum samples for antibodies against NMDAR, LGI1, CASPR2, the GABAA receptor, and the AMPA receptor using live cell-based assays. Treating clinicians assessed outcomes of ICD diagnosis and functioning (GAF) at 6 months. We included healthy controls from the general population, recruited as part of another study in Cambridge, UK.

FINDINGS

Between Feb 1, 2013, and Aug 31, 2014, we enrolled 228 patients with first-episode psychosis and 105 healthy controls. 20 (9%) of 228 patients had serum antibodies against one or more of the neuronal cell surface antibodies compared with four (4%) of 105 controls (unadjusted odds ratio 2·4, 95% CI 0·8-7·3). These associations remained non-significant when adjusted for current cigarette smoking, alcohol consumption, and illicit drug use. Seven (3%) patients had NMDAR antibodies compared with no controls (p=0·0204). The other antibodies did not differ between groups. Antibody-positive patients had lower PANSS positive, PANSS total, and catatonia scores than did antibody-negative patients. Patients had comparable scores on other PANSS items, ACE-III, and GAF at baseline, with no difference in outcomes at 6 months.

INTERPRETATION

Some patients with first-episode psychosis had antibodies against NMDAR that might be relevant to their illness, but did not differ from patients without NMDAR antibodies in clinical characteristics. Our study suggests that the only way to detect patients with these potentially pathogenic antibodies is to screen all patients with first-episode psychosis at first presentation.

FUNDING

Medical Research Council.

Pediatric Anti-N-Methyl-d-Aspartate Receptor Encephalitis: A Review with Pooled Analysis and Critical Care Emphasis

PURPOSE

Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is being recognized with increasing frequency among children. Given the paucity of evidence to guide the critical care management of these complex patients, we provide a comprehensive review of the literature with pooled analysis of published case reports and case series.

METHODS

We performed a comprehensive literature search using PubMed, Scopus, EMBASE, and Web of Science for relevant published studies. The literature search was conducted using the terms NMDA, anti-NMDA, Anti-N-methyl-d-aspartate, pediatric encephalitis, and anti-NMDAR and included articles published between 2005 and May 1, 2016.

RESULTS

Forty-eight references met inclusion criteria accounting for 373 cases. For first-line treatments, 335 (89.8%) received high-dose corticosteroids, 296 received intravenous immunoglobulin (79.3%), and 116 (31%) received therapeutic plasma exchange. In these, 187 children (50.1%) had a full recovery with only minor deficits, 174 patients (46.7%) had partial recovery with major deficits, and 12 children died. In addition, 14 patients were reported to require mechanical ventilation.

CONCLUSION

Anti-NMDA encephalitis is a formidable disease with great variation in clinical presentation and response to treatment. With early recognition of this second most common cause of pediatric encephalitis, a multidisciplinary approach by physicians may provide earlier access to first- and second-line therapies. Future studies are needed to examine the efficacy of these current therapeutic strategies on long-term morbidity.

Paediatric brainstem encephalitis associated with glial and neuronal autoantibodies

AIM

Central nervous system (CNS) autoantibodies have been reported in a range of neuroimmune diseases, but there has not been a systematic evaluation of autoantibodies in paediatric patients with brainstem encephalitis.

METHOD

Serum samples from 57 children (40 male, 17 female, median age 12y, range 0.6-18y) with a diagnosis of brainstem encephalitis were tested retrospectively for antibodies to GQ1b, aquaporin-4 (AQP4), myelin oligodendrocyte glycoprotein (MOG), N-methyl-D-aspartate receptor, LGI1, CASPR2, glycine receptor (GlyR), DPPX, and the voltage gated potassium channel (VGKC)-complex.

RESULTS

Disease localized to the brainstem was seen in 19 patients: Bickerstaff's brainstem encephalitis (n=14) and clinically isolated syndrome (n=5). Polyfocal presentation was seen in 38 children, with predominantly white matter disease in 18 patients and grey matter in 20 patients. CNS surface antibodies were found in 22/57 patients (two patients with double positivity): GQIb (n=6), NMDAR (n=7), GlyR (n=5), MOG (n=5), and one AQP4. Three patients were positive for VGKC-complex antibodies. All patients were negative for antibodies to DPPX and the VGKC-complex antigens LGI1, CASPR2, and contactin-2. Although there were some partial differences in the presentations, the clinical features and outcomes did not relate clearly to the presence or absence of specific antibodies.

INTERPRETATION

As determined retrospectively, 39% of patients had cell surface antibodies. The results did not suggest any relationship with treatment or outcomes obtained but it is possible that specific antibody detection could be a helpful guide to more intensive immunotherapies in some cases.

Antibody-Mediated Autoimmune Encephalitis in Childhood

BACKGROUND

The differential diagnosis of encephalitis in childhood is vast, and evaluation for an etiology is often unrevealing. Encephalitis by way of autoimmunity has long been suspected, as in cases of acute disseminated encephalomyelitis; however, researchers have only recently reported evidence of antibody-mediated immune dysregulation resulting in clinical encephalitis.

MAIN FINDINGS

These pathologic autoantibodies, aimed at specific neuronal targets, can result in a broad spectrum of symptoms including psychosis, catatonia, behavioral changes, memory loss, autonomic dysregulation, seizures, and abnormal movements. Autoimmune encephalitis in childhood is often quite different from adult-onset autoimmune encephalitis in clinical presentation, frequency of tumor association, and ultimate prognosis. As many of the autoimmune encephalitides are sensitive to immunotherapy, prompt diagnosis and initiation of appropriate treatment are paramount.

CONCLUSIONS

Here we review the currently recognized antibody-mediated encephalitides of childhood and will provide a framework for diagnosis and treatment considerations.

Autoantibodies to neuronal antigens in children with focal epilepsy and no prima facie signs of encephalitis

OBJECTIVE

There is increasing awareness of neuronal autoantibodies and their impact on the pathogenesis of epilepsy. We investigated children with focal epilepsy in order to provide an estimate of autoantibody frequency within a pediatric population without prima facie evidence of encephalitis using a broad panel of autoantibodies. This was done to assess the specificity of antibodies and to see whether antibodies might be of modifying influence on the course of focal epilepsies.

METHOD

We searched for autoantibodies in 124 patients with focal epilepsy (1-18 years; mean 10; 6 years). Sera were tested using a broad panel of surface and intracellular antigens.

RESULTS

We found autoantibodies in 5/124 patients (4%): high-positive GAD65 antibodies (n = 1), low-positive GAD65 antibodies (N = 1), VGKC complex antibodies not reactive with LGI1 or CASPR2 (n = 3). We did not find any distinctive features distinguishing antibody positive patients from those without antibodies.

CONCLUSIONS

The antibodies found in this cohort are probably neither disease-specific nor pathogenic. This has been suggested before for these antigenic targets. Moreover, they do not seem to modify disease severity in the antibody-positive epilepsy patients.

Neuronal autoantibodies in mesial temporal lobe epilepsy with hippocampal sclerosis

OBJECTIVE

Our aim was to investigate the prevalence of neuronal autoantibodies (NAbs) in a large consecutive series with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) and to elucidate the clinical and laboratory clues for detection of NAbs in this prototype of frequent, drug-resistant epilepsy syndrome.

METHODS

Consecutive patients diagnosed with MTLE fulfilling the MRI criteria for HS were enrolled. The sera of patients and various control groups (80 subjects) were tested for eight NAbs after ethical approval and signed consents. Brain tissues obtained from surgical specimens were also investigated by immunohistochemical analysis for the presence of inflammatory infiltrates. The features of seropositive versus seronegative groups were compared and binary logistic regression analysis was performed to explore the differentiating variables.

RESULTS

We found antibodies against antigens, contactin-associated protein-like 2 in 11 patients, uncharacterised voltage-gated potassium channel (VGKC)-complex antigens in four patients, glycine receptor (GLY-R) in 5 patients, N-methyl-d-aspartate receptor in 4 patients and γ-aminobutyric acid receptor A in 1 patient of 111 patients with MTLE-HS and none of the control subjects. The history of status epilepticus, diagnosis of psychosis and positron emission tomography or single-photon emission CT findings in temporal plus extratemporal regions were found significantly more frequently in the seropositive group. Binary logistic regression analysis disclosed that status epilepticus, psychosis and cognitive dysfunction were statistically significant variables to differentiate between the VGKC-complex subgroup versus seronegative group.

CONCLUSIONS

This first systematic screening study of various NAbs showed 22.5% seropositivity belonging mostly to VGKC-complex antibodies in a large consecutive series of patients with MTLE-HS. Our results indicated a VGKC-complex autoimmunity-related subgroup in the syndrome of MTLE-HS.

Clinical utility of seropositive voltage-gated potassium channel-complex antibody

BACKGROUND

Antibodies against voltage-gated potassium channel (VGKC)-complex are implicated in the pathogenesis of acquired neuromyotonia, limbic encephalitis, faciobrachial dystonic seizure, and Morvan syndrome. Outside these entities, the clinical value of VGKC-complex antibodies remains unclear.

METHODS

We conducted a single-center review of patients positive for VGKC-complex antibodies over an 8-year period.

RESULTS

Among 114 patients positive for VGKC-complex antibody, 11 (9.6%) carrying the diagnosis of limbic encephalitis (n = 9) or neuromyotonia (n = 2) constituted the classic group, and the remaining 103 cases of various neurologic and non-neurologic disorders comprised the nonclassic group. The median titer for the classic group was higher than the nonclassic group (p < 0.0001). A total of 90.9% of the patients in the classic and 21.4% in the nonclassic group possessed high (>0.25 nM) VGKC-complex antibody levels (p < 0.0001). A total of 75.0% of the patients in the high-level group had definite or probable autoimmune basis, while nonautoimmune disorders were seen in 75.6% of patients from the low-level group (p < 0.0001). A total of 26.3% of patients were found with active or remote solid organ or hematologic malignancy, but no antibody titer difference was observed among subgroups of absent, active, or remote malignancy. Compared to age-matched US national census, rates of active cancer in our cohort were higher in patients older than 45 years.

CONCLUSIONS

High VGKC-complex antibody titers are more likely found in patients with classically associated syndromes and other autoimmune conditions. Low-level VGKC-complex antibodies can be detected in nonspecific and mostly nonautoimmune disorders. The presence of VGKC-complex antibody, rather than its level, may serve as a marker of malignancy.

The relevance of VGKC positivity in the absence of LGI1 and Caspr2 antibodies

OBJECTIVE

To assess the clinical relevance of a positive voltage-gated potassium channel (VGKC) test in patients lacking antibodies to LGI1 and Caspr2.

METHODS

VGKC-positive patients were tested for LGI1 and Caspr2 antibodies. Patients lacking both antibodies were matched (1:2) to VGKC-negative patients. Clinical and paraclinical criteria were used to blindly determine evidence for autoimmune inflammation in both groups. Patients with an inconclusive VGKC titer were analyzed in the same way.

RESULTS

A total of 1,455 patients were tested by VGKC radioimmunoassay. Fifty-six patients tested positive, 50 of whom were available to be included. Twenty-five patients had antibodies to LGI1 (n = 19) or Caspr2 (n = 6) and 25 patients lacked both antibodies. Evidence for autoimmune inflammation was present in 7 (28%) of the VGKC-positive patients lacking LGI1 and Caspr2, compared to 9 (18%) of the VGKC-negative controls (p = 0.38). Evidence for autoimmune inflammation was mainly found in patients with limbic encephalitis/encephalomyelitis (57%), but not in other clinical phenotypes (5%, p < 0.01). VGKC titers were significantly higher in patients with antibodies to LGI1 or Caspr2 (p < 0.001). However, antibodies to Caspr2 could also be detected in patients with inconclusive low VGKC titer, while many VGKC-positive patients had no evidence for autoimmune inflammation.

CONCLUSIONS

VGKC positivity in the absence of antibodies to LGI1 and Caspr2 is not a clear marker for autoimmune inflammation and seems not to contribute in clinical practice. No cutoff value for the VGKC titer was appropriate to discriminate between patients with and without autoimmune inflammation.

Neuronal antibodies in pediatric epilepsy: Clinical features and long-term outcomes of a historical cohort not treated with immunotherapy

OBJECTIVE

In autoimmune encephalitis the etiologic role of neuronal cell-surface antibodies is clear; patients diagnosed and treated early have better outcomes. Neuronal antibodies have also been described in patients with pediatric epilepsy without encephalitis. The aim was to assess whether antibody presence had any effect on long-term outcomes in these patients.

METHODS

Patients (n = 178) were recruited between 1988 and 1992 as part of the prospective Dutch Study of Epilepsy in Childhood; none received immunotherapy. Healthy age-matched bone-marrow donors served as controls (n = 112). All sera were tested for serum N-methyl-d-aspartate receptor (NMDAR), alpha amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, leucine rich glioma inactivated 1, contactin associated protein like 2 (CASPR2), contactin-2, glutamic acid decarboxylase, and voltage gated potassium channel (VGKC)-complex antibodies by standard techniques. No cerebrospinal fluid (CSF) samples were available. Results were correlated with clinical data collected over 15 years.

RESULTS

Seventeen patients (9.5%) were positive for VGKC complex (n = 3), NMDAR (n = 7), CASPR2 (n = 4), and contactin-2 (n = 3), compared to three (3/112; 2.6%) healthy controls (VGKC complex [n = 1], NMDAR [n = 2]; p = 0.03; Fisher's exact test). Titers were relatively low (≤1:100 for cell-surface antibodies), but 8 (47%) of the 17 positive samples bound to the surface of live hippocampal neurons consistent with a potential pathogenic antibody. Preexisting cognitive impairment was more frequent in antibody-positive patients (9/17 vs. 33/161; p = 0.01). Fourteen antibody-positive patients were treated with standard antiepileptic drugs (AEDs); three (17%) became intractable but this was not different from the 16 (10%) of 161 antibody-negative patients. In 96 patients with available follow-up samples at 6 and/or 12 months, 6 of 7 positive antibodies had disappeared and, conversely, antibodies had appeared for the first time in a further 7 patients.

SIGNIFICANCE

Neuronal antibodies were found at low levels in 9.5% of patients with new-onset pediatric epilepsy but did not necessarily persist over time, and the development of antibodies de novo in later samples suggests they could be due to a secondary response to neuronal damage or inflammation. Moreover, as the response to standard AEDs and the long-term outcome did not differ from those of antibody-negative pediatric patients, these findings suggest that routine neuronal antibody testing is unlikely to be helpful in pediatric epilepsy. However, the higher incidence of preexisting cognitive problems in the antibody-positive group, the CASPR2 and contactin-2 antibodies in 7 of 17 patients, and the binding of 8 of 17 of serum samples to live hippocampal neurons suggest that neuronal antibodies, even if secondary, could contribute to the comorbidities of pediatric epilepsy.