Clinical manifestations of patients with CASPR2 antibodies

Contactin-associated protein-like 2 antibody-associated autoimmune encephalitis in children: case reports and systematic review of literature

OBJECTIVES

To ascertain the clinical characteristics of pediatric patients with contactin-associated protein-like 2 (CASPR2) antibody-associated autoimmune encephalitis (AEs).

METHODS

Two cases of CASPR2 antibody-associated AEs have been reported. In addition, a systematic search of literature published between January 2010 and March 2022 through six online databases was conducted to identify the pediatric patients with CASPR2 antibody-associated AEs. Data on demographics, clinical symptoms, laboratory examinations, imaging, treatment, and outcome were collected.

RESULTS

Our updated literature search yielded 1,837 publications, of which 21 were selected, and 40 patients in this study met the diagnostic criteria for AE. There were 25 males and 15 females with a mean age of 9.2 years. The most common presenting symptoms are psychiatric symptoms (72.5%), sleep changes (62.5%), and movement disorders (60%). The psychiatric symptoms included mood changes (39.1%), behavior changes (25%), and hallucination (7.5%). In total, 23 cases (57.5%) combined with autonomic dysfunction, such as gastrointestinal dysmotility, cardiovascular-related symptoms, and sweating. No tumors were observed in children. Thirty-eight patients received first-line immunotherapy, and eight received first-line and second-line immunotherapy. All patients had a good clinical response to immune therapy. Mean mRS at onset was 3.4; It was 0.88 at the last follow-up. There was no recurrence during follow-up.

CONCLUSION

Psychiatric symptoms, sleep disorders, movement disorders, and cardiovascular-related symptoms are the most common presentation in pediatric patients with CASPR2 antibody-associated AEs. Tumor, particularly with thymoma, is uncommon in children diagnosed with CASPR2 antibody-associated AEs. In addition, prompt diagnosis and immunotherapy can relieve symptoms and improve the prognosis.

Seronegative autoimmune encephalitis: clinical characteristics and factors associated with outcomes

Seronegative autoimmune encephalitis is autoimmune encephalitis without any identifiable pathogenic antibody. Although it is a major subtype of autoimmune encephalitis, many unmet clinical needs exist in terms of clinical characteristics, treatments and prognosis. In this institutional cohort study, patients diagnosed with seronegative autoimmune encephalitis with available 2-year outcomes were analysed for the disease course, 2-year outcome prediction system, effect of immunotherapy, necessity of further immunotherapy at 6 or 12 months and pattern of brain atrophy. Seronegative autoimmune encephalitis was subcategorized into antibody-negative probable autoimmune encephalitis, autoimmune limbic encephalitis and acute disseminated encephalomyelitis. Poor 2-year outcome was defined by modified Rankin scale scores 3-6, and the 2-year serial data of Clinical Assessment Scales in Autoimmune Encephalitis score was used for longitudinal data analyses. A total of 147 patients were included. The frequency of achieving a good 2-year outcome (modified Rankin scale 0-2) was 56.5%. The antibody-negative probable autoimmune encephalitis subtype exhibited the poorest outcomes, although the baseline severity was similar among the subtypes. The RAPID score, consisting of five early usable clinical factors, refractory status epilepticus, age of onset ≥60 years, probable autoimmune encephalitis (antibody-negative probable autoimmune encephalitis subtype), infratentorial involvement and delay of immunotherapy ≥1 month, was associated with poorer 2-year outcomes. Any immunotherapy was associated with clinical improvement in the patients with low risk for poor 2-year outcomes (RAPID scores 0-1), and the combination immunotherapy of steroid, immunoglobulin, rituximab and tocilizumab was associated with better outcomes in the patients with high risk for poor 2-year outcomes (RAPID scores 2-5). In patients with persistent disease at 6 months, continuing immunotherapy was associated with more improvement, while the effect of continuing immunotherapy for more than 12 months was unclear. In the longitudinal analysis of MRI, the development of cerebellar atrophy indicated poor outcomes, while the absence of diffuse cerebral atrophy or medial temporal atrophy indicated the possibility of a good outcome. This study provides information about the clinical characteristics and courses, the effect of immunotherapy and its duration, and prognostic factors in seronegative autoimmune encephalitis.

Immunity, Ion Channels and Epilepsy

Epilepsy is a common chronic neurological disorder in modern society. One of the major unmet challenges is that current antiseizure medications are basically not disease-modifying. Among the multifaceted etiologies of epilepsy, the role of the immune system has attracted considerable attention in recent years. It is known that both innate and adaptive immunity can be activated in response to insults to the central nervous system, leading to seizures. Moreover, the interaction between ion channels, which have a well-established role in epileptogenesis and epilepsy, and the immune system is complex and is being actively investigated. Some examples, including the interaction between ion channels and mTOR pathways, will be discussed in this paper. Furthermore, there has been substantial progress in our understanding of the pathophysiology of epilepsy associated with autoimmune encephalitis, and numerous neural-specific autoantibodies have been found and documented. Early recognition of immune-mediated epilepsy is important, especially in cases of pharmacoresistant epilepsy and in the presence of signs of autoimmune encephalitis, as early intervention with immunotherapy shows promise.

Autoimmune Encephalitis in COVID-19 Infection: Our Experience and Systematic Review of the Literature

The neurologic complications of COVID-19 infection are frequent in hospitalized patients; a high percentage of them present neurologic manifestations at some point during the course of their disease. Headache, muscle pain, encephalopathy and dizziness are among the most common complications. Encephalitis is an inflammatory condition with many etiologies. There are several forms of encephalitis associated with antibodies against intracellular neuronal proteins, cell surfaces or synaptic proteins, referred to as autoimmune encephalitis. Several case reports published in the literature document autoimmune encephalitis cases triggered by COVID-19 infection. Our paper first presents our experience in this issue and then systematically reviews the literature on autoimmune encephalitis that developed in the background of SARS-CoV-2 infections and also discusses the possible pathophysiological mechanisms of auto-immune-mediated damage to the nervous system. This review contributes to improve the management and prognosis of COVID-19-related autoimmune encephalitis.

Contemporary advances in antibody-mediated encephalitis: anti-LGI1 and anti-Caspr2 antibody (Ab)-mediated encephalitides

Encephalitides with antibodies directed against leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (Caspr2) represent two increasingly well characterised forms of autoimmune encephalitis. Both share overlapping and distinct clinical features, are mediated by autoantibodies directed against differing proteins complexed with voltage-gated potassium channels, with unique genetic predisposition identified to date. Herein we summarise disease mechanisms, clinical features, treatment considerations, prognostic factors and clinical outcomes regarding these disorders.

Anti-contactin-associated protein-like 2 antibody-associated encephalitis in children: A case report and literature review

BACKGROUND

Anti-Contactin-associated protein-like 2 (CASPR2) antibody-associated encephalitis is a rare group of autoimmune diseases that causes extensive damage to the central and/or peripheral nervous system.

CASE PRESENTATION

Here, we reported a case of anti-CASPR2 antibody-associated encephalitis in a 12-year-old male patient with symptoms of headache, consciousness disturbance, mental abnormalities, urinary incontinence, fasciculations in the extremity muscles, and involuntary movements. The testing for autoimmune encephalitis-associated antibodies showed that CASPR2-associated antibodies were positive, and electroencephalography showed diffuse slow waves. No tumor was found after screening for malignancies. The child's status significantly improved after receiving immunotherapy with intravenous methylprednisolone and immunoglobulin.

CONCLUSIONS

Anti-CASPR2 antibody-associated encephalitis has been rarely reported in children. It has a complex clinical presentation and a low incidence of tumor. Most pediatric patients have a favorable prognosis and relapse is uncommon.

CASPR2-Related Morvan Syndrome: Autonomic, Polysomnographic, and Neuropsychological Observations

Objective

Morvan syndrome is characterized by central, autonomic, and peripheral hyperexcitability due to contactin-associated protein 2 (CASPR2) antibody. Our objective was to study the clinical spectrum, electrophysiologic, autonomic, polysomnographic, and neuropsychological profile in patients with CASPR2-related Morvan syndrome.

Methods

Serum and CSF samples that were CASPR2 antibody positive from 2016 to 2019 were assessed. Among them, patients with Morvan syndrome diagnosed based on clinical and electrophysiologic basis were included.

Results

Fourteen (M:F = 10:4) patients with Morvan syndrome were included with age at onset of 37.1 ± 17.5 years. The clinical features were muscle twitching (12), insomnia (12), pain (11), paresthesias (9), hyperhidrosis (7), hypersalivation (6), double incontinence (3), spastic speech (2), dysphagia (2), behavioral disturbances (2), seizures (1), and cold intolerance (1). Neurologic examination revealed myokymia (12), hyperactive tendon reflexes (10), and tremor (6). EMG revealed neuromyotonia (12) and increased spontaneous activity (7). Autonomic function tests conducted in 8 patients revealed definite autonomic dysfunction (4), orthostatic hypotension (2), early dysfunction (1), and postural orthostatic tachycardia syndrome (1). Polysomnography findings in 6 patients revealed insomnia (3), absence of deep sleep (1), high-frequency beta activity (1), REM behavior disorder (1), and periodic leg movements (1). Neuropsychological evaluation showed subtle involvement of the left frontal and temporal lobe. Malignancy workup was negative. All patients were treated with steroids. There was complete neurologic resolution in follow-up with persistent neuropathic pain in 5 patients.

Conclusions

This study has contributed to the growing knowledge on CASPR2-related Morvan syndrome. It is important for an increased awareness and early recognition as it is potentially treatable by immunotherapy.

Clinical Character of CASPR2 Autoimmune Encephalitis: A Multiple Center Retrospective Study

Objective

To examine the clinical characteristics of autoimmune encephalitis associated with the contactin-associated protein-2 (CASPR2) antibody.

Materials and Methods

Medical records of all patients diagnosed with CASPR2 antibody-associated encephalitis were retrospectively analysed. Data regarding demographic features, neurological symptoms and signs, laboratory tests, imaging results, treatments, and prognosis were collected.

Results

A total of 25 patients aged from 3 to 79 years old were enrolled in this study, with a median age of 43. Eight of 25 (32%) were female, and 17 of 25 (68%) were male. The median age of symptom onset was 42 years old with the course of disease from onset to hospital admission ranging from 2 days to 6 months (median was 17 days). Six patients (6/25) had fever as an onset symptom. During the course of disease, cognitive disturbance was the most common symptom, which was observed in 17 patients (17/25) in total. Eight patients (8/25) met the criteria for limbic encephalitis. Epileptic seizure occurred in six of these eight patients. Four patients (4/25) were diagnosed as Morvan syndrome. All patients were positive for anti-CASPR2 antibody in the serum (1:10-1:300). In six patients, antibodies were detected both in the blood and CSF (1:32-1:100). White blood cell (WBC) counts in the CSF were elevated in eight patients (8/25). The concentration of proteins in CSF increased in 10 patients (ranging from 480 to 1,337.6 mg/dl), decreased in seven patients (ranging from 23.2 to 130.5 mg/dl) and remained at a normal range in the other eight patients (ranging from 150 to 450 mg/dl). Abnormal electroencephalogram (EEG) activities included slow background activity and epileptic patterns. Abnormal signals in the bilateral hippocampus were detected by magnetic resonance imaging (MRI) in three patients presenting cognitive disturbance. In one patient who had limbic encephalitis, increased metabolism of bilateral basal ganglia and the mesial temporal lobe was revealed by PET-CT. Eleven of 15 patients receiving immunotherapy experienced varying degrees of improvement. Relapse occurred in four of 25 patients (4/25) after 2 months.

Conclusion

CASPR-antibody-mediated autoimmune encephalitis is characterized by diverse clinical manifestations. The most prominent conclusion revealed by this retrospective analysis is the involvement of both central and peripheral nerve systems, as well as a lower relapse rate, a good response to immunotherapy, and favorable short-term prognosis after treatment was also demonstrated. Besides, additional work is necessary to evaluate the long-term prognosis.

Clinical Profile and Treatment Response in Patients with CASPR2 Antibody-Associated Neurological Disease

Background:

The clinical spectrum of contactin-associated protein-like 2 (CASPR2) antibody-associated disease is wide and includes Morvan syndrome. Studies describing treatment and long-term outcome are limited.

Aims:

We report the clinical profile and emphasize response to treatment and long-term outcome in eight patients with CASPR2-antibody-associated disease.

Methods:

Clinical, radiological, electrophysiological, treatment, follow-up, and outcome data were collected by retrospective chart review.

Results:

Clinical manifestations included Morvan syndrome (n = 7) and limbic encephalitis (n = 1). None of the patients were positive for LGI1 antibody. Associated features included myasthenia (n = 1), thymoma (n = 1), and dermatological manifestations (n = 4). Patients were treated with intravenous methylprednisolone and plasma exchange during the acute symptomatic phase followed by pulsed intravenous methyl prednisolone to maintain remission. Mean-modified Rankin score at admission (pre-treatment), discharge, and last follow-up were 3.75, 2.5, and 0.42, respectively. One patient with underlying thymoma and myasthenic crisis died. The other seven patients were followed up for a mean duration of 19.71 months. All of them improved completely. Relapse occurred in one patient after 13 months but responded favorably to steroids.

Conclusion:

CASPR2 antibody-associated disease has favorable response to immunotherapy with complete improvement and good outcome. Underlying malignancy may be a marker for poor prognosis.

Recurrent seizures of autoimmune origin: emerging phenotypes

OBJECTIVE

Recurrent seizures of autoimmune origin (AEp) are one of the most frequent causes of recurrent seizures or suspected epilepsy of unknown cause. The aim of this study was to identify specific phenotypes corresponding to AEp.

METHODS

We retrospectively reviewed features of patients with recurrent seizures of unknown cause and investigated for suspected AEp (January 2015-May 2018). Patients were separated in: (1) AEpAb+: AEp with positive autoantibodies; (2) AEpAb-: suspected AEp (inflammatory central nervous system (CNS) profile) without autoantibodies; (3) NAEp: epilepsy without CNS inflammation.

RESULTS

Eighty-nine epileptic patients underwent a CSF antibody detection. From the remaining 57 epileptic patients (32 excluded for a differential diagnosis), 61.4% were considered as AEp. 21% were AEpAb+ (4 NMDAR, 2 GABAbR, 3 GAD-Ab, 2 LGi1, 1 CASPR2), 40.4% AEpAb-, and 38.6% NAE. AE (AEpAb+ and AEpAb-) was significantly associated with antibody prevalence in epilepsy (APE) score ≥ 4 (80%), encephalitic phase (71.4%), psychiatric involvement (64.7%), cognitive impairment (50%), and status epilepticus (41.2%). Within the group of 29 patients without encephalitic phase and with chronic epilepsy (NEPp), 34.5% were defined as AEp. 10.4% were AEpAb+ (2 GAD, 1 CASPR2) and 24.1% were AEpAb-. NEP AEp was associated with non-cerebral autoimmune disorders, short epileptic disease duration, and cognitive impairment.

CONCLUSIONS

Autoimmune cause (AEp) should be assessed in patient suffering from recurrent seizures of unknown cause. Acute encephalitis is clearly the main AEp phenotype. AEp was also defined in more than one-third of chronic epilepsy patients (NEP) of unknown cause. Then, AEp may be combined with other autoimmune comorbidities, a shorter evolution of recurrent seizures, and cognitive impairment.

Teratoma Removal, Steroid, IVIG, Rituximab and Tocilizumab (T-SIRT) in Anti-NMDAR Encephalitis

In anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, we analysed the efficacy of a combined immunotherapy protocol consisting of teratoma removal, steroid, intravenous immunoglobulin (IVIG), rituximab and tocilizumab (T-SIRT). This cohort study included seventy-eight consecutive patients treated for anti-NMDAR encephalitis between Jan 2014 and Oct 2019 in a national referral hospital. Detailed 2-year disease time course was analysed using Clinical Assessment Scale for Autoimmune Encephalitis (CASE) scores at every 2 weeks for 12 weeks from baseline, every month for the next 3 months and then every 3 months. Treatment regimens at each time point were categorized as SI, SIR, or SIRT with/without teratoma removal (T). Adverse events were classified according to the Common Terminology Criteria for Adverse-Events (CTCAE v5.0), where a severe adverse event was defined as an adverse event with CATAE grade 4. In a linear mixed model analysis, using the SIRT regimen was more effective than SIR or SI regimens in lowering CASE scores (P < 0.001 and P = 0.001, respectively). The presence of teratoma (P = 0.001), refractory status epilepticus (P < 0.001) and a higher CASE score at baseline (P < 0.001) predicted a higher CASE score at each time point. Completion of the (T)-SIRT regimen within 1 month of onset resulted in better 1-year improvements in CASE score (P < 0.001) and modified Rankin scale scores (P = 0.001), compared to those of using other regimens within 1 month or delaying teratoma removal for more than 1 month. Pneumonia was a frequent adverse event (52/78, 66.7%) in the whole study population and neutropenia was frequent during SIRT (11/52, 21.2%), but the regimen was well tolerated in most patients. We concluded that the early application of combined immunotherapy consisting of T-SIRT had better efficacy than was found for delayed or partial application of this combination in anti-NMDAR encephalitis.

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.

Diagnostic Value of Structural and Functional Neuroimaging in Autoimmune Epilepsy

Epilepsy is a common nervous system disease, which affects about 70 million people all over the world. In 2017, the International League Against Epilepsy (ILAE) considered immune factors as its independent cause, and the concept of autoimmune epilepsy (AE) was widely accepted. Early diagnosis and timely treatment can effectively improve the prognosis of the disease. However, due to the diversity of clinical manifestations, the expensive cost of autoantibody detection, and the increased prevalence in Western China, the difficulty for clinicians in early diagnosis and treatment has increased. Fortunately, convenient and fast imaging examinations are expected to help even more. The imaging manifestations of AE patients were characteristic, especially the combined application of structural and functional neuroimaging, which improved the diagnostic value of imaging. In this paper, several common autoantibodies associated with AE and their structure and function changes in neuroimaging were reviewed to provide help for neurologists to achieve the goal of precision medicine.

Disrupted AMPA Receptor Function upon Genetic- or Antibody-Mediated Loss of Autism-Associated CASPR2

Neuropsychiatric disorders share susceptibility genes, suggesting a common origin. One such gene is CNTNAP2 encoding contactin-associated protein 2 (CASPR2), which harbours mutations associated to autism, schizophrenia, and intellectual disability. Antibodies targeting CASPR2 have also been recently described in patients with several neurological disorders, such as neuromyotonia, Morvan's syndrome, and limbic encephalitis. Despite the clear implication of CNTNAP2 and CASPR2 in neuropsychiatric disorders, the pathogenic mechanisms associated with alterations in CASPR2 function are unknown. Here, we show that Caspr2 is expressed in excitatory synapses in the cortex, and that silencing its expression in vitro or in vivo decreases the synaptic expression of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors and the amplitude of AMPA receptor-mediated currents. Furthermore, Caspr2 loss of function blocks synaptic scaling in vitro and experience-dependent homoeostatic synaptic plasticity in the visual cortex. Patient CASPR2 antibodies decrease the dendritic levels of Caspr2 and synaptic AMPA receptor trafficking, and perturb excitatory transmission in the visual cortex. These results suggest that mutations in CNTNAP2 may contribute to alterations in AMPA receptor function and homoeostatic plasticity, and indicate that antibodies from anti-CASPR2 encephalitis patients affect cortical excitatory transmission.

Anti-LGI1, anti-GABABR, and Anti-CASPR2 encephalitides in Asia: A systematic review

AIM

We aim to review the literature to collate and describe features of encephalitides arising from autoantibodies against leucine-rich glioma-inactivated 1 (LGI1), gamma aminobutyric acid receptor (GABABR), and contactin-associated protein-like 2 (CASPR2) in Asian populations and compare them with findings of Western studies.

METHODS

Peer-reviewed articles published till 24 May 2020 were searched, and original, full-text studies from Asia with serum/CSF antibody-based diagnosis and at least 2 patients were selected. Twenty-four studies with 263 patients (139 anti-LGI1, 114 anti-GAGABR, and 10 anti-CASPR2) were included. Data were pooled to produce descriptive information on demographics, clinical characteristics, diagnostics, treatments, and outcome.

RESULTS

The mean age was 54.2 (anti-LGI1), 55.2 (anti-GABABR), and 47.7 years (anti-CASPR2), with an overall male predominance of 62.0%. Commonest clinical features across all types were seizures (87.5%), memory deficits (80.7%), psychiatric disturbances (75.9%), and altered consciousness (52.9%). Four anti-LGI1, 40 anti-GABABR, and 1 anti-CASPR2 patients had tumors. CSF, MRI, and EEG were abnormal in 33.3%, 54.1%, and 75% patients in anti-LGI1; 60.0%, 49.6%, and 85.7% in anti-GABABR; and 50%, 44.4%, and 100% in anti-CASPR2 patients, respectively. 95.6% patients received first-line therapy alone (steroids/IVIG/Plasma therapy), and 4.4% received second-line therapy (rituximab/cyclophosphamide). 91.7%, 63.6%, and 70% of patients had favorable outcomes (modified Rankin Score 0-2) with mortality rates at 2.5%, 23.2%, and 0% in the three types, respectively.

CONCLUSION

Our findings suggest that these disorders present in Asian patients at a relatively young age often with features of seizures, memory deficits, and psychiatric disturbances and usually demonstrate a favorable clinical outcome.

The B cell immunobiology that underlies CNS autoantibody-mediated diseases

A rapidly expanding and clinically distinct group of CNS diseases are caused by pathogenic autoantibodies that target neuroglial surface proteins. Despite immunotherapy, patients with these neuroglial surface autoantibody (NSAb)-mediated diseases often experience clinical relapse, high rates of long-term morbidity and adverse effects from the available medications. Fundamentally, the autoantigen-specific B cell lineage leads to production of the pathogenic autoantibodies. These autoantigen-specific B cells have been consistently identified in the circulation of patients with NSAb-mediated diseases, accompanied by high serum levels of autoantigen-specific antibodies. Early evidence suggests that these cells evade well-characterized B cell tolerance checkpoints. Nearer to the site of pathology, cerebrospinal fluid from patients with NSAb-mediated diseases contains high levels of autoantigen-specific B cells that are likely to account for the intrathecal synthesis of these autoantibodies. The characteristics of their immunoglobulin genes offer insights into the underlying immunobiology. In this Review, we summarize the emerging knowledge of B cells across the NSAb-mediated diseases. We review the evidence for the relative contributions of germinal centres and long-lived plasma cells as sources of autoantibodies, discuss data that indicate migration of B cells into the CNS and summarize insights into the underlying B cell pathogenesis that are provided by therapeutic effects.

Update on IgG4-mediated autoimmune diseases: New insights and new family members

Antibodies of IgG4 subclass are exceptional players of the immune system, as they are considered to be immunologically inert and functionally monovalent, and as such may be part of classical tolerance mechanisms. IgG4 antibodies are found in a range of different diseases, including IgG4-related diseases, allergy, cancer, rheumatoid arthritis, helminth infection and IgG4 autoimmune diseases, where they may be pathogenic or protective. IgG4 autoimmune diseases are an emerging new group of diseases that are characterized by pathogenic, antigen-specific autoantibodies of IgG4 subclass, such as MuSK myasthenia gravis, pemphigus vulgaris and thrombotic thrombocytopenic purpura. The list of IgG4 autoantigens is rapidly growing and to date contains 29 candidate antigens. Interestingly, IgG4 autoimmune diseases are restricted to four distinct organs: 1) the central and peripheral nervous system, 2) the kidney, 3) the skin and mucous membranes and 4) the vascular system and soluble antigens in the blood circulation. The pathogenicity of IgG4 can be validated using our classification system, and is usually excerted by functional blocking of protein-protein interaction.

Fatal familial insomnia: A new case description with early response to immunotherapy

Fatal Familial Insomnia (FFI) is a rare prionopathy with autosomal dominant inheritance. Although it owes its name because insomnia is one of the most frequent and core symptoms, its clinical phenotype can be wide and heterogeneous. This usually makes it necessary to rule out other clinical processes, such as limbic encephalitis or Creutzfeldt Jakob disease, whose symptoms can sometimes overlap. We present the case of a 46-year-old male with a rapidly progressive multidomain cognitive impairment, associated with instability in gait, myoclonus and persistent and progressive insomnia. His mother had died from a genetically determined FFI (D178N mutation). Due to clinical course, an immunomediated encephalopathy was suspected, and immunosuppressive treatment with steroids and immunoglobulins was initiated. The patient showed initial improvement, but later rapidly progressive deterioration until his death 7 months after clinical onset. Cranial magnetic resonance, electroencephalogram and cerebrospinal fluid (CSF) did not show any findings. The antiTPO and antineuronal antibodies were negative. The genetiic study demonstrated the missense mutation c.532G > A (p.Asp178Asn) compatible with FFI. Postmortem study showed synaptic deposits of PrPsc in the entorhinal cortex and in thalamus, which confirmed FFI diagnosis.

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.

Relevance of Surface Neuronal Protein Autoantibodies as Biomarkers in Seizure-Associated Disorders

The detection of neuronal surface protein autoantibody-related disorders has contributed to several changes in our understanding of central nervous system autoimmunity. The clinical presentation of these disorders may be associated (or not) with tumors, and often patients develop an inexplicable onset of epilepsy, catatonic or autistic features, or memory and cognitive dysfunctions. The autoantigens in such cases have critical roles in synaptic transmission and plasticity, memory function, and process learning. For months, patients with such antibodies may be comatose or encephalopathic and yet completely recover with palliative care and immunotherapies. This paper reviews several targets of neuronal antibodies as biomarkers in seizure disorders, focusing mainly on autoantibodies, which target the extracellular domains of membrane proteins, namely leucine-rich glioma-inactivated-1 (LGI1), contactin-associated protein-like 2 (CASPR2), the N-methyl-D-aspartate receptor (NMDAR), γ-aminobutyric acid receptor-B (GABA_BR), the glycine receptor (GlyR), and a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). In order to restore health status, limit hospitalization, and optimize results, testing these antibodies should be done locally, using internationally certified procedures for a precise and rapid diagnosis, with the possibility of initiating therapy as soon as possible.

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.

Investigation of neuronal auto-antibodies in children diagnosed with epileptic encephalopathy of unknown cause

AIM

Cryptogenic forms of epileptic encephalopathies (EE) with their well-known features of drug-resistance, mental deterioration and partial response to immunotherapies are ideal candidates for screening for neuronal autoantibodies (NAA).

METHOD

Fifty consecutive pediatric patients with a diagnosis of EE of unknown cause were included. Nine NAAs were tested by ELISA, RIA or cell-based assays. Clinical features of seronegative and seropositive patients were compared.

RESULTS

NAAs were found in 7/50 (14%) patients. They were N-methyl-d-aspartate receptor in two (4%), glycine receptor in two (4%), contactin-associated protein-like 2 in one (2%), glutamic acid decarboxylase in one (2%) and type A gamma aminobutyric acid receptor in one patient (2%). Furthermore, serum IgGs of two patients negative for well-characterized NAAs, showed strong reactivity with the uncharacterized membrane antigens of live hippocampal neurons. There were no significant differences between seropositive and seronegative patients by means of epilepsy duration, anti-epileptic drug resistance, EE type, types of seizures, seizure frequencies, EEG features or coexisting autoimmune diseases. Some seropositive patients gave good-moderate response to immunotherapy.

DISCUSSION

Potential clues for the possible role of autoimmunity in seropositive patients with EE were atypical prognosis of the classical EE type, atypical progression and unusual neurological findings like dyskinesia.

Absence of Axoglial Paranodal Junctions in a Child With CNTNAP1 Mutations, Hypomyelination, and Arthrogryposis

Leukodystrophies and genetic leukoencephalopathies are a heterogeneous group of heritable disorders that affect the glial-axonal unit. As more patients with unsolved leukodystrophies and genetic leukoencephalopathies undergo next generation sequencing, causative mutations in genes leading to central hypomyelination are being identified. Two such individuals presented with arthrogryposis multiplex congenita, congenital hypomyelinating neuropathy, and central hypomyelination with early respiratory failure. Whole exome sequencing identified biallelic mutations in the CNTNAP1 gene: homozygous c.1163G>C (p.Arg388Pro) and compound heterozygous c.967T>C (p.Cys323Arg) and c.319C>T (p.Arg107*). Sural nerve and quadriceps muscle biopsies demonstrated progressive, severe onion bulb and axonal pathology. By ultrastructural evaluation, septate axoglial paranodal junctions were absent from nodes of Ranvier. Serial brain magnetic resonance images revealed hypomyelination, progressive atrophy, and reduced diffusion in the globus pallidus in both patients. These 2 families illustrate severe progressive peripheral demyelinating neuropathy due to the absence of septate paranodal junctions and central hypomyelination with neurodegeneration in CNTNAP1-associated arthrogryposis multiplex congenita.

A New Classification System for IgG4 Autoantibodies

IgG4 autoimmune diseases are characterized by the presence of antigen-specific autoantibodies of the IgG4 subclass and contain well-characterized diseases such as muscle-specific kinase myasthenia gravis, pemphigus, and thrombotic thrombocytopenic purpura. In recent years, several new diseases were identified, and by now 14 antigens targeted by IgG4 autoantibodies have been described. The IgG4 subclass is considered immunologically inert and functionally monovalent due to structural differences compared to other IgG subclasses. IgG4 usually arises after chronic exposure to antigen and competes with other antibody species, thus "blocking" their pathogenic effector mechanisms. Accordingly, in the context of IgG4 autoimmunity, the pathogenicity of IgG4 is associated with blocking of enzymatic activity or protein-protein interactions of the target antigen. Pathogenicity of IgG4 autoantibodies has not yet been systematically analyzed in IgG4 autoimmune diseases. Here, we establish a modified classification system based on Witebsky's postulates to determine IgG4 pathogenicity in IgG4 autoimmune diseases, review characteristics and pathogenic mechanisms of IgG4 in these disorders, and also investigate the contribution of other antibody entities to pathophysiology by additional mechanisms. As a result, three classes of IgG4 autoimmune diseases emerge: class I where IgG4 pathogenicity is validated by the use of subclass-specific autoantibodies in animal models and/or in vitro models of pathogenicity; class II where IgG4 pathogenicity is highly suspected but lack validation by the use of subclass specific antibodies in in vitro models of pathogenicity or animal models; and class III with insufficient data or a pathogenic mechanism associated with multivalent antigen binding. Five out of the 14 IgG4 antigens were validated as class I, five as class II, and four as class III. Antibodies of other IgG subclasses or immunoglobulin classes were present in several diseases and could contribute additional pathogenic mechanisms.

Autoimmune encephalitis with anti-leucine-rich glioma-inactivated 1 or anti-contactin-associated protein-like 2 antibodies (formerly called voltage-gated potassium channel-complex antibodies)

PURPOSE OF REVIEW

Twenty years since the discovery of voltage-gated potassium channel (VGKC)-related autoimmunity; it is currently known that the antibodies are not directed at the VGKC itself but to two closely associated proteins, anti-leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (Caspr2). Antibodies to LGI1 and Caspr2 give well-described clinical phenotypes. Anti-LGI1 encephalitis patients mostly have limbic symptoms, and anti-Caspr2 patients have variable syndromes with both central and peripheral symptoms. A large group of patients with heterogeneous symptoms are VGKC positive but do not have antibodies against LGI1 or Caspr2. The clinical relevance of VGKC positivity in these 'double-negative' patients is questionable. This review focusses on these three essentially different subgroups.

RECENT FINDINGS

The clinical phenotypes of anti-LGI1 encephalitis and anti-Caspr2 encephalitis have been described in more detail including data on treatment and long-term follow-up. A specific human leukocyte antigen (HLA) association was found in nontumor anti-LGI1 encephalitis, but not clearly in those with tumors. There has been increasing interest in the VGKC patients without LGI1/Caspr2 antibodies questioning its relevance in clinical practice.

SUMMARY

Anti-LGI1 encephalitis and anti-Caspr2 encephalitis are separate clinical entities. Early recognition and treatment is necessary and rewarding. The term VGKC-complex antibodies, lumping patients with anti-LGI1, anti-Caspr2 antibodies or lacking both, should be considered obsolete.

Expanding spectrum of contactin-associated protein 2 (CASPR2) autoimmunity-syndrome of parkinsonism and ataxia

Contactin-associated protein 2 (CASPR2) antibodies are originally associated with Morvan's syndrome and peripheral nerve hyper excitability. Our objective was to study retrospectively the clinical spectrum of CASPR2 antibody-positive patients in our hospital. This is a retrospective observational study. Patients treated at the Amrita Institute of Medical Sciences from May 2013 to April 2016, who were tested positive for CASPR2 antibodies, were included. A total of 1584 samples were tested in the neuroimmunology laboratory during the study period for voltage-gated potassium channel (VGKC) complex antibodies-leucine-rich glioma-inactivated protein 1 (LGI1) and CASPR2 antibodies. Thirty-four were positive for LGI1, 13 were positive for CASPR2, and 7 were for both (total 54-3.4% positivity). Of these 54 cases, 11 were treated in our hospital. Seven were positive for LGI1, three for CASPR2, and one for both. The patient who had both CASPR2 and LGI1 antibody positive had Morvan's syndrome. One patient with CASPR2 had neuromyotonia. The other patient was admitted with status epilepticus with a syndrome of parkinsonism and ataxia. The third patient had encephalopathy and myoclonus with a syndrome of parkinsonism and ataxia. Two of them underwent siddha treatment for other ailments prior to the onset of the disease for other ailments. Our short series shows the expanding spectrum of CASPR2 autoimmunity. Syndrome of parkinsonism and ataxia is an important manifestation of CASPR2 autoimmunity where we can offer a definitive treatment.

Voltage-gated Potassium Channel Antibody Autoimmune Encephalopathy Presenting With Isolated Psychosis in an Adolescent

Antibody-mediated encephalopathies associated with serum or cerebrospinal fluid antibodies directed against neuronal structures may present with a multitude of neuropsychiatric syndromes. Although some of the antibody-driven conditions are now well recognized in adults (eg, N-methyl-D-aspartate receptor antibody encephalitis), the spectrum of neuropsychiatric manifestations in the pediatric population is less clear. Psychosis, confusion, catatonia, and additional behavioral changes, along with seizures, encephalopathy, and movement disorders, may be initial manifestations or concurrent features in all age groups. Psychosis, when present, is often part of a broader spectrum of neurological and neuropsychiatric symptoms for which the diagnosis of autoimmune encephalitis is considered. The authors present the case of an adolescent with an acute and isolated psychotic presentation of voltage-gated potassium channel antibody encephalitis, further expanding the phenotypic spectrum of this specific antibody-mediated disease and raising the possibility that specific immune-mediated processes may define a biological subgroup of psychoses.

Voltage-gated Potassium Channel Antibody Autoimmune Encephalopathy Presenting With Isolated Psychosis in an Adolescent

Antibody-mediated encephalopathies associated with serum or cerebrospinal fluid antibodies directed against neuronal structures may present with a multitude of neuropsychiatric syndromes. Although some of the antibody-driven conditions are now well recognized in adults (eg, N-methyl-D-aspartate receptor antibody encephalitis), the spectrum of neuropsychiatric manifestations in the pediatric population is less clear. Psychosis, confusion, catatonia, and additional behavioral changes, along with seizures, encephalopathy, and movement disorders, may be initial manifestations or concurrent features in all age groups. Psychosis, when present, is often part of a broader spectrum of neurological and neuropsychiatric symptoms for which the diagnosis of autoimmune encephalitis is considered. The authors present the case of an adolescent with an acute and isolated psychotic presentation of voltage-gated potassium channel antibody encephalitis, further expanding the phenotypic spectrum of this specific antibody-mediated disease and raising the possibility that specific immune-mediated processes may define a biological subgroup of psychoses.

Afterdischarges following M waves in patients with voltage-gated potassium channels antibodies

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Afterdischarges in patients with VGKC encephalitis.

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Afterdischarges disappeared in accordance with the clinical improvement.

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Afterdischarges might be a sensitive indicator of peripheral nerve hyperexcitability.

Objective

To explore the correlation between afterdischarges in motor nerve conduction studies and clinical motor hyperexcitability in patients with voltage-gated potassium channels (VGKC) antibodies.

Methods

Six patients with positive serum antibodies to contactin-associated protein-like 2 (CASPR2) or/and leucine-rich glioma-inactivated protein 1 (LGI1) were recruited, including 5 with autoimmune encephalitis, and 1 with cramp-fasciculation syndrome. Electromyography (EMG), nerve conduction studies (NCS) and F waves were performed, and afterdischarges were assessed. One patient was followed up.

Results

Five patients had clinical evidence of peripheral motor nerve hyperexcitability (myokymia or cramp), and four of them had abnormal spontaneous firing in concentric needle electromyography (EMG). Prolonged afterdischarges following normal M waves were present in all six patients, including the two patients who had no EMG evidence of peripheral nerve hyperexcitability (PNH). Afterdischarges disappeared after treatment with intravenous immunoglobulin (IVIG).

Conclusion

The afterdischarges in motor nerve conduction study might be a sensitive indicator of peripheral motor nerve hyperexcitability in patients with VGKC antibodies.

Significance

Afterdischarges in motor nerve conduction study might be more sensitive than needle electromyography for detecting peripheral motor nerve hyperexcitability, and could disappear gradually in accordance with clinical improvement and reduction of antibodies.

The Laboratory Diagnosis of Autoimmune Encephalitis

Autoimmune encephalitis is a group of encephalitis syndromes that cause altered mentality, memory decline, or seizures in association with the presence of serum and cerebrospinal fluid (CSF) autoantibodies (auto-Abs). An early diagnosis enables early treatments. The detection of auto-Abs is a confirmatory diagnosis. Tissue-based assay, cell-based immunoassay, and immunoblotting are used to detect various autoantibodies. The CSF test for the presence of antibodies is important because it is more sensitive and reflects disease activity in many autoimmune encephalitis, although antibody tests can be negative even in the presence of autoimmune encephalitis. EEG is often abnormal, but nonspecific. A unilateral or bilateral medial temporal T2 high signal is a common finding in MRI. Fludeoxyglucose-positron emission tomography is sometimes useful for diagnosis in patients with normal MRI.

Autoimmune encephalitis in psychiatric institutions: current perspectives

Autoimmune encephalitis is a rare and newly described group of diseases involving autoantibodies directed against synaptic and neuronal cell surface antigens. It comprises a wide range of neuropsychiatric symptoms. Sensitive and specific diagnostic tests such as cell-based assay are primordial for the detection of neuronal cell surface antibodies in patients' cerebrospinal fluid or serum and determine the treatment and follow-up of the patients. As neurological symptoms are fairly well described in the literature, this review focuses on the nature of psychiatric symptoms occurring at the onset or during the course of the diseases. In order to help the diagnosis, the main neurological symptoms of the most representative synaptic and neuronal cell surface autoantibodies were detailed. Finally, the exploration of these autoantibodies for almost a decade allowed us to present an overview of autoimmune encephalitis incidence in psychiatric disease and the general guidelines for the management of psychiatric manifestations. For the majority of autoimmune encephalitis, the prognosis depends on the rapidity of the detection, identification, and the management of the disease. Because the presence of pronounced psychiatric symptoms drives patients to psychiatric institutions and can hinder the diagnosis, the aim of this work is to provide clues to help earlier detection by physicians and thus provide better medical care to patients.

Tocilizumab in Autoimmune Encephalitis Refractory to Rituximab: An Institutional Cohort Study

A considerable portion of autoimmune encephalitis (AE) does not respond to conventional immunotherapies and subsequently has poor outcomes. We aimed to determine the efficacy of tocilizumab, an anti-interleukin-6 antibody, in rituximab-refractory AE compared with other treatment options. From an institutional cohort of AE, 91 patients with inadequate clinical response to first-line immunotherapy and following rituximab were retrospectively reviewed. Patients were grouped according to their further immunotherapy strategies. Thirty (33.0 %) patients were included in the tocilizumab group, 31 (34.0 %) in the additional rituximab group, and 30 (33.0 %) in the observation group. Outcomes were defined as the favorable modified Rankin Scale scores (≤2) at 1 and 2 months from the initiation of each treatment strategy and at the last follow-up. Favorable clinical response (improvement of the modified Rankin Scale scores by ≥ 2 points or achievement of the mRS scores ≤ 2) at the last follow-up was also analyzed. The tocilizumab group showed more frequent favorable mRS scores at 2 months from treatment initiation and at the last follow-up compared with those at the relevant time points of the remaining groups. The majority (89.5 %) of the patients with clinical improvement at 1 month from tocilizumab treatment maintained a long-term favorable clinical response. No serious adverse effects of rituximab or tocilizumab were reported. Therefore, we suggest that tocilizumab might be a good treatment strategy for treating AE refractory to conventional immunotherapies and rituximab. The tocilizumab-mediated clinical improvement manifests as early at 1 month after treatment initiation.

Seizures and Epilepsies due to Channelopathies and Neurotransmitter Receptor Dysfunction: A Parallel between Genetic and Immune Aspects

Despite intensive research activity leading to many important discoveries, the pathophysiological mechanisms underlying seizures and epilepsy remain poorly understood. An important number of specific gene defects have been related to various forms of epilepsies, and autoimmunity and epilepsy have been associated for a long time. Certain central nervous system proteins have been involved in epilepsy or acute neurological diseases with seizures either due to underlying gene defects or immune dysfunction. Here, we focus on 2 of them that have been the object of particular attention and in-depth research over the past years: the N-methyl-D-aspartate receptor and the leucin-rich glioma-inactivated protein 1 (LGI1). We also describe illustrative examples of situations in which genetics and immunology meet in the complex pathways that underlie seizures and epilepsy.

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.

Autoantibodies in Neuropsychiatric Disorders

Little is known about the etiology of neuropsychiatric disorders. The identification of autoantibodies targeting the N-methyl-d-aspartate receptor (NMDA-R), which causes neurological and psychiatric symptoms, has reinvigorated the hypothesis that other patient subgroups may also suffer from an underlying autoimmune condition. In recent years, a wide range of neuropsychiatric diseases and autoantibodies targeting ion-channels or neuronal receptors including NMDA-R, voltage gated potassium channel complex (VGKC complex), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R), γ-aminobutyric acid receptor (GABA-R) and dopamine receptor (DR) were studied and conflicting reports have been published regarding the seroprevalence of these autoantibodies. A clear causative role of autoantibodies on psychiatric symptoms has as yet only been shown for the NMDA-R. Several other autoantibodies have been related to the presence of certain symptoms and antibody effector mechanisms have been proposed. However, extensive clinical studies with large multicenter efforts to standardize diagnostic procedures for autoimmune etiology and animal studies are needed to confirm the pathogenicity of these autoantibodies. In this review, we discuss the current knowledge of neuronal autoantibodies in the major neuropsychiatric disorders: psychotic, major depression, autism spectrum, obsessive-compulsive and attention-deficit/hyperactivity disorders.

Rituximab treatment for autoimmune limbic encephalitis in an institutional cohort

OBJECTIVE

To determine efficacy and safety of rituximab treatment as a second-line immunotherapy treatment for autoimmune limbic encephalitis (ALE) and to determine factors associated with functional improvement and favorable outcome following rituximab treatment.

METHODS

We recruited 80 patients with ALE who were treated with rituximab as a second-line immunotherapy from the Korea Autoimmune Synaptic and Paraneoplastic Encephalitis Registry and reviewed 81 patients without rituximab as a control. We grouped patients according to the detection or type of antibodies; in addition, we evaluated clinical, laboratory, first-line immunotherapy, and rituximab treatment profiles and defined main outcomes as improvements on the modified Rankin Scale (mRS) score and a favorable mRS score (0-2) at the last follow-up.

RESULTS

Functional improvement occurred more frequently in the rituximab group compared to the control group. In the rituximab group, 30 (37.5%) patients had synaptic autoantibodies, 15 (18.8%) in the paraneoplastic autoantibodies, and 35 (43.8%) were antibody-negative. The effect of rituximab was the same regardless of autoantibody status. Additional monthly rituximab therapy and partial response to first-line immunotherapies were associated with mRS score improvements, as well as favorable mRS scores. mRS scores of 4-6 as the worst neurologic status predicted an unfavorable mRS score. There were no reported serious infusion-related or infectious adverse effects of rituximab.

CONCLUSIONS

Rituximab is effective and safe as a second-line immunotherapy for ALE, regardless of autoantibody status. Additional monthly rituximab therapy might potentiate the efficacy of rituximab.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that rituximab improves mRS scores for patients with autoimmune limbic encephalitis who fail first-line therapy.

Prevalence of antineuronal antibodies in patients with encephalopathy of unknown etiology: Data from a nationwide registry in Korea

We aimed to evaluate the prevalence of antineuronal antibodies in a nationwide cohort of patients with encephalopathy of unknown etiology. We screened 1699 patients with idiopathic encephalopathy who were referred from 70 hospitals across Korea for autoimmune synaptic and classic paraneoplastic antibodies. Those with cerebellar degeneration, sensory polyneuropathy or other paraneoplastic syndromes without encephalopathy were not included in this study. One-hundred and four patients (6.12%) had antibody-associated autoimmune encephalopathy. Autoimmune synaptic antibodies were identified in 89 patients (5.24%) and classic paraneoplastic antibodies were identified in 16 patients (0.94%). The patients with antibody-associated autoimmune encephalopathy comprised a small but significant portion of the total number of patients with encephalopathy of unknown cause.

Effect of Immunotherapy on Seizure Outcome in Patients with Autoimmune Encephalitis: A Prospective Observational Registry Study

Objective

To evaluate the seizure characteristics and outcome after immunotherapy in adult patients with autoimmune encephalitis (AE) and new-onset seizure.

Methods

Adult (age ≥18 years) patients with AE and new-onset seizure who underwent immunotherapy and were followed-up for at least 6 months were included. Seizure frequency was evaluated at 2–4 weeks and 6 months after the onset of the initial immunotherapy and was categorized as “seizure remission”, “> 50% seizure reduction”, or “no change” based on the degree of its decrease.

Results

Forty-one AE patients who presented with new-onset seizure were analysed. At 2–4 weeks after the initial immunotherapy, 51.2% of the patients were seizure free, and 24.4% had significant seizure reduction. At 6 months, seizure remission was observed in 73.2% of the patients, although four patients died during hospitalization. Rituximab was used as a second-line immunotherapy in 12 patients who continued to have seizures despite the initial immunotherapy, and additional seizure remission was achieved in 66.6% of them. In particular, those who exhibited partial response to the initial immunotherapy had a better seizure outcome after rituximab, with low adverse events.

Conclusion

AE frequently presented as seizure, but only 18.9% of the living patients suffered from seizure at 6 months after immunotherapy. Aggressive immunotherapy can improve seizure outcome in patients with AE.