Mechanisms of autoimmune encephalitis

PURPOSE OF REVIEW

To provide an overview of the pathogenic mechanisms involved in autoimmune encephalitides mediated by antibodies against neuronal surface antigens, with a focus on NMDAR and LGI1 encephalitis.

RECENT FINDINGS

In antibody-mediated encephalitides, binding of IgG antibodies to neuronal surface antigens results in different pathogenic effects depending on the type of antibody, IgG subclass and epitope specificity. NMDAR IgG1 antibodies cause crosslinking and internalization of the target, synaptic and brain circuitry alterations, as well as alterations of NMDAR expressing oligodendrocytes, suggesting a link with white matter lesions observed in MRI studies. LGI1 IgG4 antibodies, instead, induce neuronal dysfunction by disrupting the interaction with cognate proteins and altering AMPAR-mediated signaling. In-vitro findings have been corroborated by memory and behavioral changes in animal models obtained by passive transfer of patients' antibodies or active immunization. These models have been fundamental to identify targets for innovative therapeutic strategies, aimed at counteracting or preventing antibody effects, such as the use of soluble ephrin-B2, NMDAR modulators (e.g., pregnenolone, SGE-301) or chimeric autoantibody receptor T cells (CAART) in models of NMDAR encephalitis.

SUMMARY

A deep understanding of the pathogenic mechanisms underlying antibody-mediated encephalitides is crucial for the development of new therapeutic approaches targeting brain autoimmunity.

NMDA Receptors in Health and Diseases: New Roles and Signaling Pathways-Anti-N-Methyl-D-Aspartate Receptor (NMDAR) Autoantibodies as Potential Biomarkers of Fatigue in Patients with Rheumatic Diseases

Fatigue is a widespread and complex symptom with motor and cognitive components; it is diagnosed predominantly by questionnaire. We recently published a correlation between anti-N-methyl-D-aspartate receptor (NMDAR) antibodies and fatigue in patients with SLE (systemic lupus erythematosus). In the present study, we examined whether this association also applies to patients with other rheumatic diseases. Serum samples of 88 patients with different rheumatic diseases were analyzed for the presence of anti-NR2 antibodies and Neurofilament light chain (NfL) protein. The severity of fatigue was determined according to the FSMC questionnaire (Fatigue Scale for Motor and Cognitive Functions) and correlated with the circulating antibody titer and NfL level accordingly. Positive titers of anti-NR2 antibodies were detected in patients with both autoimmune and non-autoimmune rheumatic diseases. These patients suffer predominantly from severe fatigue. The circulating NfL level did not correlate with the anti-NR2 titer and the fatigue severity in all patient groups. The association of severe fatigue with circulating anti-NR2 antibodies in patients with rheumatic diseases, independently from the main disease, suggests an individual role of these autoantibodies in fatigue pathophysiology. Thus, the detection of these autoantibodies might be a helpful diagnostic tool in rheumatic patients with fatigue.

A Soluble PrPC Derivative and Membrane-Anchored PrPC in Extracellular Vesicles Attenuate Innate Immunity by Engaging the NMDA-R/LRP1 Receptor Complex

Nonpathogenic cellular prion protein (PrPC) demonstrates anti-inflammatory activity; however, the responsible mechanisms are incompletely defined. PrPC exists as a GPI-anchored membrane protein in diverse cells; however, PrPC may be released from cells by ADAM proteases or when packaged into extracellular vesicles (EVs). In this study, we show that a soluble derivative of PrPC (S-PrP) counteracts inflammatory responses triggered by pattern recognition receptors in macrophages, including TLR2, TLR4, TLR7, TLR9, NOD1, and NOD2. S-PrP also significantly attenuates the toxicity of LPS in mice. The response of macrophages to S-PrP is mediated by a receptor assembly that includes the N-methyl-d-aspartate receptor (NMDA-R) and low-density lipoprotein receptor-related protein-1 (LRP1). PrPC was identified in EVs isolated from human plasma. These EVs replicated the activity of S-PrP, inhibiting cytokine expression and IκBα phosphorylation in LPS-treated macrophages. The effects of plasma EVs on LPS-treated macrophages were blocked by PrPC-specific Ab, by antagonists of LRP1 and the NMDA-R, by deleting Lrp1 in macrophages, and by inhibiting Src family kinases. Phosphatidylinositol-specific phospholipase C dissociated the LPS-regulatory activity from EVs, rendering the EVs inactive as LPS inhibitors. The LPS-regulatory activity that was lost from phosphatidylinositol-specific phospholipase C-treated EVs was recovered in solution. Collectively, these results demonstrate that GPI-anchored PrPC is the essential EV component required for the observed immune regulatory activity of human plasma EVs. S-PrP and EV-associated PrPC regulate innate immunity by engaging the NMDA-R/LRP1 receptor system in macrophages. The scope of pattern recognition receptors antagonized by S-PrP suggests that released forms of PrPC may have broad anti-inflammatory activity.

Current Status of Biomarkers in Anti-N-Methyl-D-Aspartate Receptor Encephalitis

The discovery of biomarkers in rare diseases is of paramount importance to allow a better diagnosis, improve predictions of outcomes, and prompt the development of new treatments. Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a rare autoimmune disorder associated with the presence of antibodies targeting the GluN1 subunit of the NMDAR. Since it was discovered in 2007, large efforts have been made towards the identification of clinical, paraclinical, and molecular biomarkers to better understand the immune mechanisms that govern the course of the disease as well as to define predictors of treatment response and long-term outcomes. However, most of these biomarkers are still in an exploratory phase, with only a few candidates reaching the final phases of the always-complex process of biomarker development, mainly due to the low incidence of the disease and its recent description. Clinical and paraclinical markers are probably the most widely explored in anti-NMDAR encephalitis, five of them combined in a clinical score to predict 1 year outcome. On the contrary, soluble molecules, such as persistent antibody positivity, antibody titers, cytokines, and other inflammatory mediators, have been proposed as biomarkers of clinical activity, inflammation, prognosis, and treatment response, but further studies are required for their clinical validation including larger and more homogenous cohorts of patients. Similarly, genetic susceptibility biomarkers are still in the exploratory phase and, therefore, weak conclusions can for now only be achieved. Thus, further studies are warranted to define biomarkers and unravel the underlying mechanisms driving rare diseases such as anti-NMDAR encephalitis. Future international collaborative studies with prospective designs that enable the enrollment of large cohorts will allow for the identification and validation of novel biomarkers for clinical decision-making.

Autoantibodies in neurological disease

The realization that autoantibodies can contribute to dysfunction of the brain has brought about a paradigm shift in neurological diseases over the past decade, offering up important novel diagnostic and therapeutic opportunities. Detection of specific autoantibodies to neuronal or glial targets has resulted in a better understanding of central nervous system autoimmunity and in the reclassification of some diseases previously thought to result from infectious, 'idiopathic' or psychogenic causes. The most prominent examples, such as aquaporin 4 autoantibodies in neuromyelitis optica or NMDAR autoantibodies in encephalitis, have stimulated an entire field of clinical and experimental studies on disease mechanisms and immunological abnormalities. Also, these findings inspired the search for additional autoantibodies, which has been very successful to date and has not yet reached its peak. This Review summarizes this rapid development at a point in time where preclinical studies have started delivering fundamental new data for mechanistic understanding, where new technologies are being introduced into this field, and - most importantly - where the first specifically tailored immunotherapeutic approaches are emerging.

Chronic presence of blood circulating anti-NMDAR1 autoantibodies impairs cognitive function in mice

High titers of anti-NMDAR1 autoantibodies in brain cause anti-NMDAR1 encephalitis that displays psychiatric symptoms of schizophrenia and/or other psychiatric disorders in addition to neurological symptoms. Low titers of anti-NMDAR1 autoantibodies are reported in the blood of a subset of the general human population and psychiatric patients. Since ~0.1–0.2% of blood circulating antibodies cross the blood-brain barriers and antibodies can persist for months and years in human blood, it is important to investigate whether chronic presence of these blood circulating anti-NMDAR1 autoantibodies may impair human cognitive functions and contribute to the development of psychiatric symptoms. Here, we generated mice carrying low titers of anti-NMDAR1 autoantibodies in blood against a single antigenic epitope of mouse NMDAR1. Mice carrying the anti-NMDAR1 autoantibodies are healthy and display no differences in locomotion, sensorimotor gating, and contextual memory compared to controls. Chronic presence of the blood circulating anti-NMDAR1 autoantibodies, however, is sufficient to impair T-maze spontaneous alternation in the integrity of blood-brain barriers across all 3 independent mouse cohorts, indicating a robust cognitive deficit in spatial working memory and/or novelty detection. Our studies implicate that chronic presence of low titers of blood circulating anti-NMDAR1 autoantibodies may impair cognitive functions in both the general healthy human population and psychiatric patients.

Altered EEG markers of synaptic plasticity in a human model of NMDA receptor deficiency: Anti-NMDA receptor encephalitis

Plasticity of synaptic strength and density is a vital mechanism enabling memory consolidation, learning, and neurodevelopment. It is strongly dependent on the intact function of N-Methyl-d-Aspartate Receptors (NMDAR). The importance of NMDAR is further evident as their dysfunction is involved in many diseases such as schizophrenia, Alzheimer's disease, neurodevelopmental disorders, and epilepsies. Synaptic plasticity is thought to be reflected by changes of sleep slow wave slopes across the night, namely higher slopes after wakefulness at the beginning of sleep than after a night of sleep. Hence, a functional NMDAR deficiency should theoretically lead to altered overnight changes of slow wave slopes. Here we investigated whether pediatric patients with anti-NMDAR encephalitis, being a very rare but unique human model of NMDAR deficiency due to autoantibodies against receptor subunits, indeed show alterations in this sleep EEG marker for synaptic plasticity. We retrospectively analyzed 12 whole-night EEGs of 9 patients (age 4.3-20.8 years, 7 females) and compared them to a control group of 45 healthy individuals with the same age distribution. Slow wave slopes were calculated for the first and last hour of Non-Rapid Eye Movement (NREM) sleep (factor 'hour') for patients and controls (factor 'group'). There was a significant interaction between 'hour' and 'group' (p = 0.013), with patients showing a smaller overnight decrease of slow wave slopes than controls. Moreover, we found smaller slopes during the first hour in patients (p = 0.022), whereas there was no group difference during the last hour of NREM sleep (p = 0.980). Importantly, the distribution of sleep stages was not different between the groups, and in our main analyses of patients without severe disturbance of sleep architecture, neither was the incidence of slow waves. These possible confounders could therefore not account for the differences in the slow wave slope values, which we also saw in the analysis of the whole sample of EEGs. These results suggest that quantitative EEG analysis of slow wave characteristics may reveal impaired synaptic plasticity in patients with anti-NMDAR encephalitis, a human model of functional NMDAR deficiency. Thus, in the future, the changes of sleep slow wave slopes may contribute to the development of electrophysiological biomarkers of functional NMDAR deficiency and synaptic plasticity in general.

Case Report: Antibodies to the N-Methyl-D-Aspartate Receptor in a Patient With Multiple Sclerosis

The association between multiple sclerosis and anti-N-Methyl-D-Aspartate receptor encephalitis is limited to merely a few case reports, and the exploration of the pathogenic mechanisms underlying the overlap of these two disease entities is very limited. Therefore, case reports and literature review on N-Methyl-D-aspartate receptor antibody in patients with multiple sclerosis are unusual and noteworthy. A young female had the first episode of paresthesia and motor symptoms with positive anti-N-Methyl-D-Aspartate receptor antibody and recovered after immunotherapy, and at the first relapse, the patient developed disorders of consciousness with positive anti-N-Methyl-D-Aspartate receptor antibody, findings of magnetic resonance imaging showed features of autoimmune encephalitis, which was also controlled by immunotherapy. At the second relapse, anti-N-Methyl-D-Aspartate receptor antibody turned negative while oligoclonal bands presented positive, and findings of magnetic resonance imaging showed features of multiple sclerosis. Afterwards, we followed the patient after receiving disease modifying treatment to monitor the efficacy and safety of teriflunomide. Based on literature review, demyelinating diseases patients with anti-neuronal antibody have complex, diverse and atypical symptoms; therefore, high attention and increased alertness are necessary for neurologists. Conclusively, anti-neuronal antibody may present in many neuroinflammatory conditions, and diagnostic criteria should be used with caution if the clinical presentation is atypical, and neurologists should not rely excessively on laboratory tests to diagnose neurological diseases. Timely and comprehensive examination and consideration as well as early standardized treatment are the key factors to reduce patient recurrence and obtain a good prognosis.

Autoimmune encephalitis mediated by B-cell response against N-methyl-d-aspartate receptor

Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is a neuropsychiatric disease characterized by an antibody-mediated autoimmune response against NMDAR. Recent studies have shown that anti-NMDAR antibodies are involved in the pathophysiology of the disease. However, the upstream immune and inflammatory processes responsible for this pathogenic response are still poorly understood. Here, we immunized mice against the region of NMDA receptor containing the N368/G369 amino acids, previously implicated in a pathogenic response. This paradigm induced encephalopathy characterized by blood-brain barrier opening, periventricular T2-MRI hyperintensities and IgG deposits into the brain parenchyma. Two weeks after immunization, mice developed clinical symptoms reminiscent of encephalitis: anxiety- and depressive-like behaviours, spatial memory impairment (without motor disorders) and increased sensitivity to seizures. This response occurred independently of overt T-cell recruitment. However, it was associated with B220+ (B cell) infiltration towards the ventricles, where they differentiated into CD138+ cells (plasmocytes). Interestingly, these B cells originated from peripheral lymphoid organs (spleen and cervical lymphoid nodes). Finally, blocking the B-cell response using a depleting cocktail of antibodies reduced the severity of symptoms in encephalitis mice. This study demonstrates that the B-cell response can lead to an autoimmune reaction against NMDAR that drives encephalitis-like behavioural impairments. It also provides a relevant platform for dissecting encephalitogenic mechanisms in an animal model, and enables the testing of therapeutic strategies targeting the immune system in anti-NMDAR encephalitis.

Influence of methodological and patient factors on serum NMDAR IgG antibody detection in psychotic disorders: a meta-analysis of cross-sectional and case-control studies

BACKGROUND

Antibodies targeting the N-methyl-D-aspartate receptor (NMDAR) have been detected in patients with psychosis. However, studies measuring the IgG subclass in serum have provided variable estimates of prevalence, and it is unclear whether these antibodies are more common in patients than controls. Because these inconsistencies could be due to methodological approaches and patient characteristics, we aimed to investigate the effect of these factors on heterogeneity.

METHODS

We searched Web of Science and Ovid (MEDLINE and PsycINFO) for cross-sectional and case-control studies published between Jan 1, 2000, and May 5, 2019, that reported NMDAR IgG antibody seropositivity in patients with psychosis. Pooled proportions and odds ratios (ORs) were derived using random-effects models. We estimated between-study variance (τ²) and the proportion of observed variance due to heterogeneity (I²). We then used univariable random-effects meta-regression analysis to investigate the effect of study factors on heterogeneity of proportions and ORs. Our protocol was registered on PROSPERO (CRD42018099874).

FINDINGS

Of 1276 articles in the initial search, 28 studies were eligible for inclusion, including 14 cross-sectional studies and 14 case-control studies. In cross-sectional studies, NMDAR IgG antibodies were detected in 0·73% (95% CI 0·09-1·38; I² 56%; p=0·026) of patients with psychosis, and in case-control studies, patients with psychosis were not significantly more likely to be seropositive than healthy individuals (OR 1·57, 95% CI 0·78-3·16; I² 15%; p=0·20). Meta-regression analyses indicated that heterogeneity was significantly associated with assay type across both study designs, illness stage in cross-sectional studies, and study quality in case-control studies. Compared with studies using a fixed cell-based assay, cross-sectional and case-control studies using the live method yielded higher pooled prevalence estimates (0·36% [95% CI -0·23 to 0·95] vs 2·97% [0·70 to 5·25]) and higher ORs (0·65 [0·33 to 1·29] vs 4·43 [1·73 to 11·36]). In cross-sectional studies, the prevalence was higher in exclusively first-episode samples than in multi-episode or mixed samples (2·18% [0·25 to 4·12] vs 0·16% [-0·31 to 0·63]), and in case-control studies, higher ORs were reported in low-quality studies than in high-quality studies (3·80 [1·47 to 9·83] vs 0·72 [0·36 to 1·42]).

INTERPRETATION

Higher estimates of NMDAR IgG antibody prevalence have been obtained with the live cell-based assay, and studies using this method find that seropositivity is more common in patients with psychosis than in controls. The effects of illness stage and study quality on heterogeneity were not consistent across study designs, and we provide clear recommendations for clinicians and researchers regarding interpreting these findings.

FUNDING

None.

Clinical analysis of a patient simultaneously positive for antibodies of myelin oligodendrocyte glycoprotein and anti-N-methyl-D-aspartate receptor: A case report

RATIONALE

Myelin oligodendrocyte glycoprotein (MOG) antibody (MOG-Ab) disease (MOG-AD) is a type of demyelinating disease of the central nervous system characterized by a high frequency of optic neuritis (ON) attacks. anti-Nmethyl-D-aspartate receptor (NMDAR) encephalitis (anti-NMDARe) is an autoimmune disorder characterized by memory deficits, conscious disturbance, and seizures. Cases of simultaneous occurrence of MOG-Ab and anti-NMDARe antibody (anti-NMDARe-Ab) are rarely reported and could be mistaken for overlapping MOG-antibody disease (MOG-AD) and NMDARe. The diagnosis of such patients is challenging.

PATIENT CONCERNS

We report the case of a 37-year-old man who presented with recurrent headaches for 3 months and worsening symptoms over 2 weeks. He had a history of ON. He had a generalized seizure after 7 days in the hospital.

DIAGNOSIS

Brain magnetic resonance imaging (MRI) and cerebrospinal fluid tests showed no apparent abnormalities. Repeat MRI showed slight lesions 7 days later, and cerebrospinal fluid tests showed the simultaneous occurrence of MOG-Ab and anti-NMDARe-Ab.

INTERVENTIONS

He completely recovered after treatment with low doses of oral corticosteroids.

OUTCOMES

Two months and 2 years follow-up showed that his condition was stable.

LESSONS

The co-occurrence of MOG-Ab and anti-NMDAR-Ab does not indicate the co-occurrence of MOG-AD and anti-NMDARe. Laboratory findings should be combined with the clinical features to achieve an accurate and suitable diagnosis.

Synapse and Receptor Alterations in Two Different S100B-Induced Glaucoma-Like Models

Glaucoma is identified by an irreversible retinal ganglion cell (RGC) loss and optic nerve damage. Over the past few years, the immune system gained importance in its genesis. In a glaucoma-like animal model with intraocular S100B injection, RGC death occurs at 14 days. In an experimental autoimmune glaucoma model with systemic S100B immunization, a loss of RGCs is accompanied by a decreased synaptic signal at 28 days. Here, we aimed to study synaptic alterations in these two models. In one group, rats received a systemic S100B immunization (n = 7/group), while in the other group, S100B was injected intraocularly (n = 6–7/group). Both groups were compared to appropriate controls and investigated after 14 days. While inhibitory post-synapses remained unchanged in both models, excitatory post-synapses degenerated in animals with intraocular S100B injection (p = 0.03). Excitatory pre-synapses tendentially increased in animals with systemic S100B immunization (p = 0.08) and significantly decreased in intraocular ones (p = 0.04). Significantly more N-methyl-d-aspartate (NMDA) receptors (both p ≤ 0.04) as well as gamma-aminobutyric acid (GABA) receptors (both p < 0.03) were observed in S100B animals in both models. We assume that an upregulation of these receptors causes the interacting synapse types to degenerate. Heightened levels of excitatory pre-synapses could be explained by remodeling followed by degeneration.

An Elderly Case of Paraneoplastic Anti-NMDA Receptor Encephalitis Associated with Small-cell Lung Cancer Expressing NR1 Subunits

A 61-year-old Japanese man presented with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. NR1 antibodies were detected in his cerebrospinal fluid. Chest computed tomography revealed lung tumor. The patient was diagnosed with paraneoplastic anti-NMDAR encephalitis associated with lung cancer and treated with two cycles of intravenous high-dose methylprednisolone and one cycle of intravenous immunoglobulin. However, he died one year later without improvement. An autopsy confirmed small-cell lung cancer (SCLC). Immunohistochemistry revealed the expression of NR1 subunits in the tumor cells, suggesting that SCLC may trigger NR1 autoimmunity though the expression of NR1 subunits as onconeural antigens, expanding the phenotypic spectrum of paraneoplastic neurological syndrome associated with SCLC.

Cryptococcus Meningitis Can Co-occur with Anti-NMDA Receptor Encephalitis

We herein report a 50-year-old man with alcoholic cirrhosis who developed loss of consciousness and tremor of the upper limbs. Magnetic resonance imaging findings were suggestive of limbic encephalitis with bilateral hippocampal damage, and a cerebrospinal fluid (CSF) examination confirmed anti-N-methyl-D-aspartate (NMDA) and anti-glutamate receptor antibodies. Despite initial corticosteroid therapy, meningeal irritation symptoms appeared, owing to the development of cryptococcal meningitis (CM), diagnosed by the detection of cryptococcal capsular polysaccharide antigen in the follow-up CSF analysis. Cerebral infarction with reversible stenosis of major cerebral arteries during the clinical course was also observed. Following administration of antifungals and corticosteroids, the number of cells in the CSF gradually declined, and NMDA receptor antibodies disappeared. Our study demonstrates the unique coexistence of CM with anti-NMDA receptor encephalitis in adults.

Autoimmune Encephalitis: NMDA Receptor Encephalitis as an Example of Translational Neuroscience

Autoimmune encephalitis (AE) is a group of disorders causing synaptic receptor dysfunction with a broad range of neurological symptoms that has been historically difficult to differentiate clinically. Today, AE represents an excellent example of the rapid determination of the cause of a disease and the ability to identify potential treatments using relatively simple basic science techniques of investigation. Of the number of autoimmune encephalitides identified thus far, one of the best examples of the impact of basic science studies on disease management is NMDA receptor mediated autoimmune encephalitis (NMDAr-AE). In this review, we will provide an overview of the epidemiology of NMDAr-AE, clinical features and treatments, and the basic science tools and techniques that were used to identify the cause, correlate symptoms to underlying pathophysiology, and to understand the mechanism of disease pathology.

Clinical Characterization of Definite Autoimmune Limbic Encephalitis: A 30-case Series

Objective Limbic encephalitis (LE) is an inflammatory condition of the limbic system that has an acute or subacute onset. Several types of antibodies are related to the onset of LE, including anti-N-methyl D-aspartate receptor (NMDAR) antibodies and voltage-gated potassium channel (VGKC)-complex antibodies. However, the characteristics and prevalence of LE remain unclear, especially in Asian cohorts, due to the rarity. We aimed to survey their characteristics. Materials and Methods Data of 30 cases clinically defined as "definite autoimmune LE" (based on the standard criteria) were retrospectively collected. These patients were categorized into four subtypes: NMDAR (+) (n=8), VGKC (+) (n=2), antibodies related to paraneoplastic syndrome (n=2), and an antibody-negative group (uncategorized) (n=18). Results LE is rare in Japan, and affected only 30 of 16,759 hospital patients (0.2%) over a ten-year period. The NMDAR (+) group showed distinctive symptoms, while the other three groups had similar indications. Brain MRI indicated significant medial temporal lobe atrophy at one year follow up after discharge. The prevalence of cognitive dysfunction as a complication was 64% (9/14). First-line immunotherapy resulted in a good outcome. A drastic improvement was seen from 4.0±1.1 to 1.1+ on the modified Rankin Scale. A good treatment outcome was observed in all groups (NMDAR, VGKC, and uncategorized), suggesting the importance of an early clinical diagnosis and the early initiation of treatment. Furthermore, we reviewed 26 cases that were clinically diagnosed as definitive autoimmune LE in previous case reports. Conclusion Our findings show that the establishment of a clinical diagnosis based on the clinical criteria of definitive autoimmune LE is important for the initiation of immunotherapy.

Anti-N-methyl-D-aspartate receptor encephalitis induced by bilateral ovarian teratomas with distinct histopathologic types: A case report and brief literature review

RATIONALE

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disorder that is most frequently induced by ovarian teratoma in young females. The condition can be controlled and reversed via ovarian tumor resection and immunotherapy. However, anti-NMDAR encephalitis induced by bilateral ovarian teratomas with distinct histopathologic types is rarely reported in the literature.

PATIENT CONCERNS

A 23-year-old woman presented with seizures.

DIAGNOSES

The diagnosis was anti-NMDAR encephalitis associated with ovarian teratomas based on positive anti-NMDAR antibody tests in both the cerebrospinal fluid and serum, and the detection of bilateral ovarian lesions on pelvic computed tomography. The postoperative histopathologic examination confirmed that the left lesion was an immature teratoma, and the right lesion was a mature teratoma.

INTERVENTIONS

We performed surgical resection of the ovarian teratomas and administered immunotherapy for the control of anti-NMDAR encephalitis. Chemotherapy was administered for the immature teratoma.

OUTCOMES

The patient recovered without any postoperative complications. She has been confirmed to be in complete clinical remission, and has not had a recurrence during 18 months of follow-up.

LESSONS

Anti-NMDAR encephalitis induced by bilateral ovarian teratomas of differing histopathologic types (1 immature and 1 mature) is rare. Early diagnosis and treatment with tumor resection, immunotherapy, and chemotherapy are critical for a good prognosis.

The origin of NMDA receptor hypofunction in schizophrenia

N-methyl-d-aspartate (NMDA) receptor (NMDAR) hypofunction plays a key role in pathophysiology of schizophrenia. Since NMDAR hypofunction has also been reported in autism, Alzheimer's disease and cognitive dementia, it is crucial to identify the location, timing, and mechanism of NMDAR hypofunction for schizophrenia for better understanding of disease etiology and for novel therapeutic intervention. In this review, we first discuss the shared underlying mechanisms of NMDAR hypofunction in NMDAR antagonist models and the anti-NMDAR autoantibody model of schizophrenia and suggest that NMDAR hypofunction could occur in GABAergic neurons in both models. Preclinical models using transgenic mice have shown that NMDAR hypofunction in cortical GABAergic neurons, in particular parvalbumin-positive fast-spiking interneurons, in the early postnatal period confers schizophrenia-related phenotypes. Recent studies suggest that NMDAR hypofunction can also occur in PV-positive GABAergic neurons with alterations of NMDAR-associated proteins, such as neuregulin/ErbB4, α7nAChR, and serine racemase. Furthermore, several environmental factors, such as oxidative stress, kynurenic acid and hypoxia, may also potentially elicit NMDAR hypofunction in GABAergic neurons in early postnatal period. Altogether, the studies discussed here support a central role for GABAergic abnormalities in the context of NMDAR hypofunction. We conclude by suggesting potential therapeutic strategies to improve the function of fast-spiking neurons.

Anti-NMDA-receptor antibody in initial diagnosis of mood disorder

Anti-NMDAR encephalitis is increasingly recognized as one etiology of psychiatric symptoms, but there is not enough evidence on patients with mood disorder. We assayed anti-NR1/NR2B IgG antibodies in serum and/or cerebrospinal fluid of 62 patients initially diagnosed with mood disorder by a cell-based assay. We also investigated the specific patient characteristics and psychotic symptoms. At first admission, the patients showed only psychiatric symptoms without typical neurological signs or abnormal examination findings. Four of the 62 patients had anti-NR1/NR2B IgG antibodies. The anti-NR1/NR2B IgG antibody-positive patients showed more super- or abnormal sensitivity (P = 0.00088), catatonia (P = 0.049), and more conceptual disorganization (P < 0.0001), hostility (P = 0.0010), suspiciousness (P < 0.0001), and less emotional withdrawal (P < 0.0001) and motor retardation (P < 0.0001) on the Brief Psychiatric Rating Scale than the antibody-negative patients. During the clinical course, anti-NR1/NR2B IgG antibody-positive patients showed more catatonia (P = 0.0042) and met Graus's criteria for diagnosis of anti-NMDAR encephalitis, but negative patients did not. Immunotherapy was effective for anti-NR1/NR2B IgG antibody-positive patients, and there was the weak relationship (R² = 0.318) between the anti-NR1/NR2B IgG antibody titer in the cerebrospinal fluid and the Brief Psychiatric Rating Scale score.

Autoimmune receptor encephalitis in mice induced by active immunization with conformationally stabilized holoreceptors

Autoimmunity to membrane proteins in the central nervous system has been increasingly recognized as a cause of neuropsychiatric disease. A key recent development was the discovery of autoantibodies to N-methyl-d-aspartate (NMDA) receptors in some cases of encephalitis, characterized by cognitive changes, memory loss, and seizures that could lead to long-term morbidity or mortality. Treatment approaches and experimental studies have largely focused on the pathogenic role of these autoantibodies. Passive antibody transfer to mice has provided useful insights but does not produce the full spectrum of the human disease. Here, we describe a de novo autoimmune mouse model of anti-NMDA receptor encephalitis. Active immunization of immunocompetent mice with conformationally stabilized, native-like NMDA receptors induced a fulminant encephalitis, consistent with the behavioral and pathologic characteristics of human cases. Our results provide evidence for neuroinflammation and immune cell infiltration as components of the autoimmune response in mice. Use of transgenic mice indicated that mature T cells and antibody-producing cells were required for disease induction. This active immunization model may provide insights into disease induction and a platform for testing therapeutic approaches.

Teratoma-associated anti-N-methyl-D-aspartate receptor encephalitis: A case report and literature review

RATIONALE

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disease associated with the NMDA receptor and has a good response to treatment. However, only few cases related to teratoma have been reported. Here, we report a case of teratoma-associated anti-NMDAR encephalitis.

PATIENT CONCERNS

A 25-year-old woman presenting with fever for 20 days and psychiatric symptoms for 9 days was admitted to the hospital. The patient progressed to a minimally conscious state consistent with encephalitis.

DIAGNOSIS

Considering the possibility of autoantibody-mediated encephalitis, laboratory tests were conducted to detect anti-NMDAR antibodies in cerebrospinal fluid and serum. Results confirmed the diagnosis of anti-NMDAR encephalitis. Furthermore, gynecological ultrasound investigation detected teratoma in the left ovary.

INTERVENTIONS

After resection of the teratoma with laparoscopic adnexectom, the patient was treatment with immunosuppressive therapy.

OUTCOMES

The patient recovered gradually and was discharged 2 months after the operation.

LESSONS

Anti-NMDAR encephalitis remains difficult to diagnose because of its vague manifestations, and no clinical practice guidelines for prevention and treatment of the disease have been established yet. The clinical data of a case of teratoma-related anti-NMDAR encephalitis were analyzed, and relevant studies were reviewed.

Neuronal autoantibodies associated with cognitive impairment in melanoma patients

BACKGROUND

Cancer-related cognitive impairment is an important complication in cancer patients, yet the underlying mechanisms remain unknown. Over the last decade, the field of paraneoplastic neurological syndromes has been dramatically changed by the discovery of new neuronal autoantibodies, some of them associated with cognitive impairment. We aimed to assess the prevalence of neuronal autoantibodies in melanoma patients and their association with neurological and cognitive dysfunction.

PATIENTS AND METHODS

A total of 157 consecutive melanoma patients with a median age of 63 years were recruited at the Department of Dermatology, Charité-Universitätsmedizin Berlin and tested for neuronal autoantibodies. A comprehensive neuropsychological assessment was carried out in a selected subgroup of 84 patients after exclusion of patients with confounding factors for a cognitive dysfunction, including brain metastases, relevant medication, and neurological disorders.

RESULTS

Neuronal autoantibodies were found in 22.3% of melanoma patients. The most frequent antibodies were IgA/IgM anti-NMDAR antibodies. Applying the International Cognition and Cancer Task Force criteria, 36.9% had cognitive impairment, however, with a threefold higher odds in antibody-positive compared with antibody-negative patients (57.1% versus 30.2%, OR = 3.1, 95% CI: 1.1 to 8.6; P = 0.037). In patients with anti-NMDAR antibodies, this impairment increased with higher antibody titers (P = 0.007). Antibody-positive patients had a significantly impaired overall cognitive performance (z-value: -0.38 ± 0.69 versus 0.00 ± 0.56; P = 0.014) as well as significant impairments in tests of memory, attention, and executive function. In a multiple linear regression analysis, autoantibodies were an independent risk factor for cognitive impairment (B = -0.282; 95% CI: -0.492 to -0.071; P = 0.009). Autoantibody seropositivity was associated with immune checkpoint inhibitor treatment and a history of autoimmune diseases.

CONCLUSIONS

A large number of melanoma patients harbor neuronal autoantibodies that are associated with significant cognitive impairment affecting memory, attention, and executive function. Neuronal autoantibodies might represent a pathophysiological factor and possible biomarker in the development of cancer-related cognitive impairment.

[Update on anti-N-methyl-D-aspartate receptor encephalitis]

Autoimmune encephalitis is a group of autoimmune inflammatory disorders affecting both grey and white matter of the central nervous system. Encephalitis with autoantibodies against the N‑methyl-D-aspartate receptor (NMDA-R) is the most frequent autoimmune encephalitis syndrome presenting with a characteristic sequence of psychiatric and neurological symptoms. Treatment necessitates a close interdisciplinary cooperation. This article provides an update on the current knowledge on diagnostic standards, pathogenesis, and treatment strategies for anti-NMDA-R encephalitis from psychiatric and neurological perspectives.

Mouse model of anti-NMDA receptor post-herpes simplex encephalitis

Objective

To develop an endogenous rodent model of postinfectious anti-NMDA receptor (NMDAR) encephalitis.

Methods

Six mice were inoculated intranasally with herpes simplex virus (HSV) 1 and subsequently treated with acyclovir for 2 weeks. Serum was collected at 3, 6, and 8 weeks postinoculation and tested for NMDAR antibodies through a cell-based assay. Eight weeks postinoculation, mice were killed and their brains were sectioned and immunostained with antibodies to postsynaptic density (PSD)-95 and NMDARs. Colocalization of hippocampal PSD-95 and NMDAR clusters, representing postsynaptic membrane NMDARs, was quantified via confocal imaging. Hippocampi were additionally analyzed for NMDAR and PSD-95 protein using Western blot analysis.

Results

Four of 6 mice (67%) developed serum antibodies to NMDARs: 1 at 3 weeks, 1 at 6 weeks, and 2 at 8 weeks postinoculation. As compared to inoculated mice that did not develop NMDAR antibodies, immunofluorescence staining revealed decreased hippocampal postsynaptic membrane NMDARs in mice with serum antibodies at 8 weeks postinoculation. Western blot analysis showed that mice that had NMDAR antibodies at 8 weeks had decreased total NMDAR but not PSD-95 protein in hippocampal extracts (p < 0.05).

Conclusions

Mice inoculated intranasally with HSV-1 developed serum NMDAR antibodies. These antibodies were associated with reduced hippocampal NMDARs, as has been shown in previous models where antibodies from patients with anti-NMDAR encephalitis were infused into mice, paving the way for future studies into the pathophysiology of autoimmune encephalitides.

[Autoimmune encephalitis. Anti-NMDA receptor and new immunophenotypes]

Autoimmune encephalitis (AE) is defined as neurological syndromes of subacute installation of compromise of consciousness, alteration of working memory and psychiatric disorders associated with abnormal movements and epileptic seizures and that are produced by the action of anti-neuronal antibodies. They bind to neurotransmitter receptors or membrane proteins. Antibody to NMDAR is the origin of the majority of cases of AD in children and young adults, followed by anti-LGI1 antibody for presentation in adults. The AE has increased in the last decade, with a large number of new agents described that produce mostly neurological syndromes that involve the central nervous system, with predominance of psychiatric signaling, except in children and the predominant abnormal movements, epileptic seizures and compromise of conscience. They are frequently associated with tumors in adults but in children this association is more infrecuent. All AEs respond to immunomodulatory therapy although in different measures depending on the type of antibody involved. In general, the evolution to improvement is slow and can be completed in months or even in one year or more. In this review, the main EA clinical pictures related to specific antibodies are highlighted, also mentioning recently discovered immunophenotypes.

Anesthesia for patient with anti-N-methyl-D-aspartate receptor encephalitis: A case report with a brief review of the literature

RATIONALE

Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis is an immune-mediated syndrome caused by the production of antibodies against NMDA receptors. As NMDA receptors are important targets of many anesthetic drugs, the perioperative management of patients with anti-NMDA receptor encephalitis is challenging for anesthesiologists.

PATIENT CONCERNS

A 31-year-old woman presented with akinesia and aphasia, which worsened despite steroid therapy.

DIAGNOSIS

Anti-NMDA receptor encephalitis associated with ovarian teratoma.

INTERVENTIONS

Laparoscopic ovarian cystectomy was performed under total intravenous anesthesia (TIVA) with peripheral nerve block (PNB).

OUTCOMES

The patient recovered without postoperative complications or any adverse events after surgery.

LESSONS

Ideal anesthesia for a patient with anti-NMDA receptor encephalitis is still under discussion. We decided to perform TIVA with PNB because the effect of propofol on NMDA receptors is considered less than that of volatile anesthetics; moreover, PNB may reduce the amount of propofol and opioids required for anesthesia. To conclude, TIVA with PNB may be the most appropriate method for anesthesia in a patient with anti-NMDA receptor encephalitis undergoing ovarian cystectomy.

Anti-N-methyl-D-aspartate receptor encephalitis: A case report

RATIONALE

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an auto-immune and paraneoplastic encephalitis with prominent neuropsychiatric manifestations. The N-methyl-D-aspartate receptor is located in the forebrain and hippocampus and plays a role in learning and memory.

PATIENT CONCERNS

A 29-year-old female patient with anti-NMDAR encephalitis, was reported and we also reviewed the literature and summarised the characteristics of the cases.

DIAGNOSES

In the present study, we reported 1 patient with anti-NMDAR encephalitis diagnosed by the detection of anti-NMDAR antibodies in serum and cerebrospinal fluid (CSF).

INTERVENTIONS

The patient received glucocorticoids and anti-epilepsy treatment as well as human immunoglobulin treatment.

OUTCOMES

After treatment, the patient gradually regained consciousness and was discharged after 3 months of rehabilitation. At the follow-up 2 months later, the patient had the sequelae of memory impairment and limb movement disorders.

LESSONS

An accurate early diagnosis and active treatment are crucial to the improvement in the prognosis of patients with anti-NMDAR receptor encephalitis.

Encephalitis with anti-NMDA receptor antibodies: paraneoplastic or non-paraneoplastic?

We report the case of an encephalitis patient with anti-N-methyl-D-aspartate receptor (NMDAR) antibody positivity. Anti-NMDAR encephalitis is a relatively rare autoimmune disease. In our patient, the diagnosis of anti-NMDAR encephalitis was established as late as several months after the first manifestations of the condition. Further development demonstrated that the patient probably suffered from a paraneoplastic form of the disease, although the presence of an underlying tumour was not detected by the available imaging methods at the time of diagnosis. The case is a rarity since the disease usually affects females, and only 5% of adult male patients have a paraneoplastic aetiology.

Massive idiopathic spontaneous hemothorax complicating anti-N-methyl-d-aspartate receptor encephalitis: A case report

RATIONALE

Spontaneous hemothorax is a subcategory of hemothorax which can be life threatening. The etiology of spontaneous hemothorax can be various, and in some rare cases the causes remained unknown. Hence, it is quite difficult to establish the diagnosis. Here, we report a case of spontaneous hemothorax in a young female patient who was recently diagnosed with anti-N-methyl-d-aspartate receptor encephalitis (anti-NMDAR encephalitis).

PATIENT CONCERNS

A 20-year-old female was transferred to emergency department of our hospital from local hospital presented with insomnia, mood lability, tonic-clonic seizure, and decreased level of consciousness.

DIAGNOSES

The diagnosis of anti-NMDAR encephalitis was established by detection of cerebrospinal fluid (CSF) and serum antibodies to the NMDA receptor. During the hospital stay, the patient developed massive spontaneous hemothorax and was confirmed by closed-tube thoracostomy.

INTERVENTIONS AND OUTCOMES

Video-assisted thoracotomy was performed to evacuate the blood clots and also to obtain pleural biopsy specimen for diagnostic evaluation. However, the reason of hemothorax remained idiopathic. The postoperative status of this patient was uneventful, and she was discharged on postoperative day 45 as her mental status improved markedly.

LESSONS

In this case, the patient had both anti- NMDAR encephalitis and autoimmune thyroid disease. Based on it, we suspected that the patient subjected to severe autoimmune response and inflammatory reaction, which might explain the pathologic changes of parietal pleura and visceral pleura. We recommend the suspicion of spontaneous hemothorax should be considered when the patients with autoimmune diseases present with hemorrhage-related signs or symptoms.

[A case of anti-myelin oligodendrocyte glycoprotein (MOG) and anti-N-methyl-D-aspartate (NMDA) receptor antibody-positive encephalitis with optic neuritis]

A 20-year-old female was hospitalized due to generalized seizure two weeks after an infection. She reported disorientation, neck stiffness and weakness in her legs. MRI FLAIR images and T₂WI on her first visit to our hospital showed hyperintense lesions in the bilateral cingulate gyrus and the medial region of the superior frontal gyrus. Gadolinium (Gd)-enhanced T₁WI showed enhancement in the upper part of the corpus callosum. Examination of her cerebrospinal fluid (CSF) revealed mildly elevated leucocytes. After the administration of high-dose intravenous methylprednisolone, her symptoms partially improved. However, MRI T₂WI at 16 days after admission showed a lesion with a peripheral hypointense rim in the left side of the cingulate gyrus, which had ring enhancement on contrast CT. FLAIR images at 28 days after admission showed the hyperintense lesion spreading in the subcallosal area and the brainstem, and coronal short inversion time inversion recovery (STIR) images demonstrated bilateral optic neuritis. She was treated with steroid pulse therapy and plasma exchange. Thereafter her symptoms improved. The patient's CSF at 27 days after admission tested positive for anti-myelin oligodendrocyte glycoprotein (anti-MOG) antibodies and anti-N-methyl-D-aspartate (anti-NMDA) receptor antibodies. Encephalitis with optic neuritis in a patient with both anti-MOG and anti-NMDA receptor antibodies is very rare. Coexistence of multiple antibodies in the same patient may contribute to the diversity of autoimmune diseases associated with anti-MOG antibodies or anti-NMDA receptor antibodies.

[Proposal of a diagnostic algorithm for autoimmune epilepsy: preliminary investigation of its utility]

The epilepsy syndrome of autoimmune etiology, namely, autoimmune epilepsy has attracted attention in recent years, as was reflected in the new etiology of "immunity" in the Epilepsy Classification of the International League Against Epilepsy (2017). However, no specific tests other than neuronal antibodies have been established. We proposed a diagnostic algorithm for autoimmune epilepsy and preliminarily investigated its clinical utility. We applied this algorithm to 70 patients who were suspected as having autoimmune epilepsy from clinical symptoms and laboratory findings in our institute. At least one of the three neuronal antibodies (antibodies to N-methyl-D-aspartic acid receptor (NMDAR), glutamic acid decarboxylase (GAD), and voltage-gated potassium channels (VGKC) complex) was evaluated. In this two-step algorithm, the patients were initially screened by clinical features and then evaluated by laboratory findings (neuronal antibodies, cerebrospinal fluid (CSF), MRI, FDG-PET). The results of preliminary application of the algorithm are described. One of the three neuronal antibodies was positive in 13 patients. In this preliminary investigation, it was suggested that two or more abnormal findings in the diagnostic tests (CSF, MRI, FDG-PET) favors the diagnosis of autoimmune epilepsy. On the other hand, two patients with a positive neuronal antibody test failed the first step (clinical features), partly because epilepsy was not the major manifestation of autoimmune encephalitis (VGKC complex antibody) or due to a relatively low titer of the antibody (GAD antibody). Recruitment of the patient cohort with comprehensive neuronal antibody testing and multivariate analysis of laboratory findings is warranted for validation and modification of the proposed algorithm.

Anti-NMDA Receptor Encephalitis in a Young Girl with Altered Behaviour and Abnormal Movements

Autoimmune encephalitis is a rare central nervous system disorder in which the patient presents with neuropsychiatric symptoms. We herein present a case of anti-NMDA receptor encephalitis in which the patient initially presented in the psychiatric department. A 14-year girl was brought with complains of irritability, altered behaviour, abnormal movements, self biting, and decreased sleep for the past 10 days. Her condition deteriorated during the admission and she became mute, immobile, and drowsy. Her baseline investigations and CT scan brain were normal. CPK was high and the CSF showed pleocytosis. Autoimmune encephalitis profile showed presence of antibodies against the NMDA receptors. Improvement in the symptoms was noted after treatment with steroids and plasmapharesis. This case report highlights the importance of multidisciplinary approach involving the neurologist, psychiatrist, and immunologist in accurately diagnosing and managing a rare neurological disorder presenting mainly with psychiatric symptoms.

Ion channels in EEG: isolating channel dysfunction in NMDA receptor antibody encephalitis

See Roberts and Breakspear (doi:10.1093/brain/awy136) for a scientific commentary on this article.Neurological and psychiatric practice frequently lack diagnostic probes that can assess mechanisms of neuronal communication non-invasively in humans. In N-methyl-d-aspartate (NMDA) receptor antibody encephalitis, functional molecular assays are particularly important given the presence of NMDA antibodies in healthy populations, the multifarious symptomology and the lack of radiological signs. Recent advances in biophysical modelling techniques suggest that inferring cellular-level properties of neural circuits from macroscopic measures of brain activity is possible. Here, we estimated receptor function from EEG in patients with NMDA receptor antibody encephalitis (n = 29) as well as from encephalopathic and neurological patient controls (n = 36). We show that the autoimmune patients exhibit distinct fronto-parietal network changes from which ion channel estimates can be obtained using a microcircuit model. Specifically, a dynamic causal model of EEG data applied to spontaneous brain responses identifies a selective deficit in signalling at NMDA receptors in patients with NMDA receptor antibody encephalitis but not at other ionotropic receptors. Moreover, though these changes are observed across brain regions, these effects predominate at the NMDA receptors of excitatory neurons rather than at inhibitory interneurons. Given that EEG is a ubiquitously available clinical method, our findings suggest a unique re-purposing of EEG data as an assay of brain network dysfunction at the molecular level.

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.

Fulminant course in a patient with anti-N-methyl-D-aspartate receptor encephalitis with bilateral ovarian teratomas: A case report and literature review

RATIONALE

Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis is an autoimmune disorder that can be controlled and reversed by immunotherapy. The presentation of NMDA receptor encephalitis varies, but NMDA receptor encephalitis is seldom reported in patients with both bilateral teratomas and preexisting brain injury.

PATIENT CONCERNS

A 28-year-old female with a history of traumatic intracranial hemorrhage presented acute psychosis, seizure, involuntary movement, and conscious disturbance with a fulminant course. Anti-NMDA receptor antibody was identified in both serum and cerebrospinal fluid, confirming the diagnosis of anti-NMDA receptor encephalitis. Bilateral teratomas were also identified during tumor survey. DIAGNOSES:: anti-N-methyl-D-aspartate receptor encephalitis.

INTERVENTIONS

Tumor resection and immunotherapy were performed early during the course.

OUTCOMES

The patient responded well to tumor resection and immunotherapy. Compared with other reports in the literature, her symptoms rapidly improved without further relapse.

LESSONS

This case report demonstrates that bilateral teratomas may be related to high anybody titers and that the preexisting head injury may be responsible for lowering the threshold of neurological deficits. Early diagnosis and therapy are crucial for a good prognosis in such patients.

Epileptic spasms secondary to acute cerebral and cerebellar encephalitis

BACKGROUND

Patients with infection-related acute encephalitis sometimes develop epilepsy in the chronic phase of the disease. Patients with postencephalitic epilepsy usually develop partial seizures due to the lesions generated by the encephalitis. We report a case who developed late-onset epileptic spasms after acute cerebral and cerebellar encephalitis.

CASE REPORT

A 5-year-old girl showed severe tremor, gait ataxia, partial or generalized tonic-clonic seizures, hyperactivity, and panic attacks after a mild enterocolitis. Her cerebellar symptoms disappeared until 3 months after onset, and her seizures were controlled with carbamazepine. However, the seizures reappeared as epileptic spasms 5 months after onset. The anti-NMDA-type glutamate receptor antibody concentration was significantly elevated in her cerebrospinal fluid at 8 days, 10 months, and 15 months after onset. The spasms were resistant to multiple antiepileptic drugs. High-dose methylprednisolone and high-dose immunoglobulin therapies did not show any benefits. Oral pranlukast hydrate was started 17 months after onset. After 3 weeks of the medication, her seizures disappeared, and her behavior also dramatically improved.

CONCLUSION

We presented a rare case of post-encephalitic epilepsy that manifested as epileptic spasms. Pranlukast significantly improved her seizures.

NMDAR (N-methyl-D-aspartate receptor) encephalitis in a patient with MS (multiple sclerosis): a rare and challenging case

We present a rare case of N-methyl-D-aspartate receptor (NMDAR) encephalitis in a 41-year-old Caucasian woman, who initially presented with prominent neuropsychiatric symptoms on the background of pre-existing multiple sclerosis. Here, the authors navigate the muddy water between neurology and psychiatry, describing the caveats of antibody testing with a misdiagnosed case of acute and transient psychotic episode. NMDAR encephalitis in MS is a rare condition, which can be easily confused with a new onset psychotic episode. This case report can be helpful in recognition and diagnosis of this rare condition. Making the right diagnosis is important since it can prevent an unnecessary radical treatment and long-term neuropsychiatric complications.

[Expression, purification and immunoreactivity characterization of extracellular antigenic domains of NMDAR1 protein]

This study aimed to construct prokaryotic recombinant plasmids for expression of the extracellular domains of NMDAR1 protein, purify and characterize the immunoreactivity of the recombinant proteins. Based on the mRNA sequence of human NMDAR1 gene, we predicted the structure of the antigenic domains in the extracellular part of the protein using the "phyre2" software. Primers were designed to amplify the nucleic acid fragments encoding the NMDAR1 extracellular antigenic domains by RT-PCR. The amplified gene fragments were cloned into pCold-SUMO vector to construct the recombinant plasmids which were transformed into Escherichia coli DH5α. The positive colonies harboring the recombinant plasmids were picked and verified by PCR and DNA sequencing. Then, the recombinant plasmids were transformed into E. coli BL21(DE3) strain and induced by IPTG for protein expression. The recombinant proteins were purified by Ni-NTA affinity chromatography. The target proteins were further purified by removing the 6 His-SUMO tag using enzyme excision followed by gel filtration chromatography using AKTA purifier. The purity of the recombinant proteins were evaluated by SDS-PAGE and the immunoreactivity were characterized by Western blotting. Three DNA fragments encoding the extracellular domains of NMDAR1 protein, including NR1-M1 (encoding 19-393 aa), NR1-S1 (encoding 394-544 aa) and NR1-S2 (encoding 663-800 aa), were amplified by RT-PCR. The NR1-S1 and NR1-S2 were linked with G (arginine) and T (threonine) amino acid as a combined fragment. The NR1-M1 and NR1-S1-GT-S2 fragments were cloned into pCold-SUMO vector and two recombinant plasmids, pCold-SUMO-M1 and pCold-SUMO-S1-GT-S2, were generated and expressed in E. coli. SDS-PAGE analysis showed that the recombinant plasmids expressed soluble NR1-M1 and NR1-S1-GT-S2 proteins in bacterial. After affinity chromatography and gel filtration chromatography, we obtained high purity target proteins. Western blotting assay showed that the recombinant proteins NR1-M1 and NR1-S1-GT-S2 can bind specially with their corresponding antibodies, suggesting the recombinant proteins retained antigenic reactivity. We constructed a prokaryotic expression system for expressing the NMDAR1 protein extracellular parts that had immunoreactivity successfully, and the purified proteins can be used for studying NMDAR1 function and testing the autoantibodies.

Increased serum anti-N-methyl-D-aspartate receptor antibody immunofluorescence in psychiatric patients with past catatonia

OBJECTIVE

Anti-N-methyl-D-aspartate receptor (NMDAR) antibody was thought to be the cause of anti-NMDAR encephalitis, with manifestations similar to catatonia and schizophrenia. Anti-NMDAR antibody in neuropsychiatric patients who had catatonia before were investigated in a follow-up evaluation. The intensity of antibody immunofluorescence was quantified and compared with healthy controls.

METHOD

Nineteen patients (eight males and eleven females) agreed to be followed-up. Thirteen had the diagnosis of schizophrenia, two had the diagnosis of major depressive disorder, two had bipolar disorder, one had postpartum depression, and one had herpes simplex encephalitis. No patient had catatonia during the follow-up. Nineteen sex-matched healthy controls were recruited.

RESULTS

Using Mann-Whitney U test, patients had greater intensity of anti-NMDAR antibody immunofluorescence than the healthy controls (121,979 ± 86,526 vs. 47,692 ± 26,102, p = 0.003). No correlation was found between immunofluorescence intensity and catatonia scales or symptom severity scores. Neuropsychiatric patients with past catatonia showed greater anti-NMDAR antibody response than the healthy controls.

CONCLUSION

NMDAR dysfunction might play a role in the mechanism underlying catatonia. Further studies are needed to confirm this finding.

Anti-N-methyl-D-aspartate receptor antibodies are associated with fibromyalgia in patients with systemic lupus erythematosus: a case-control study

OBJECTIVES

The high concordance between systemic lupus erythematosus (SLE) and fibromyalgia (FM) suggests common underlying mechanisms related to pain and distress in both patient groups. Increasing evidence indicates that N-methyl-D-aspartate receptors (NMDARs) play a major role in the induction and maintenance of central sensitisation with chronic pain. In this study, we evaluated the role of anti-NMDAR antibodies in the development of FM in patients with SLE.

METHODS

Sera from 104 patients with SLE, 112 patients with FM, and 110 healthy controls were analysed to detect antibodies to the N-terminus of the 2B subunit of NMDARs (GluN2B). Subjects underwent clinical examination and neuropsychiatric evaluation, and completed a questionnaire regarding FM and neuropsychiatric symptoms.

RESULTS

Of the 104 patients with SLE, 18 (17.3%) had FM. The anti-GluN2B antibody titer was significantly higher in patients with SLE (p<0.001). Among patients with SLE, those with concomitant FM had higher anti-GluN2B antibody titers (p<0.05). The anti-GluN2B antibody titer was associated positively with the tender point count (p=0.016) and the widespread pain index (p=0.005), but not with other symptom measurements. Anti-GluN2B antibody-positive patients with SLE were more likely to have neuropsychiatric systemic lupus erythematosus (NPSLE) and concomitant FM (p<0.05). Multivariate analysis showed that the anti-GluN2B antibody was an independent predictor of concomitant FM and NPSLE.

CONCLUSIONS

To our knowledge, this report is the first to suggest that anti-NMDAR antibodies are associated with the pathogenesis of FM with SLE.

Analgesic Effect of Intrathecal Administration of Chemokine Receptor CCR2 Antagonist is Related to Change in Spinal NR2B, nNOS, and SIGIRR Expression in Rat with Bone Cancer Pain

The purpose of this study is to investigate the analgesic effect of intrathecal injection of chemokine receptor CCR2 antagonist RS102895, and its effect on spinal expression of N-methyl-D-aspartate (NMDA) receptor NR2B subunit, neuronal nitric oxide synthase (nNOS), and SIGIRR in a rat model of bone cancer pain (BCP). A rat model of BCP was established by intro-tibial inoculation of W256 breast cancer cells. Female SD rats were randomly divided into five groups (n = 10 each): Sham group, Sham + RS102895 group, BCP group, BCP + RS102895 group, and BCP + DMSO group. Rats received intrathecal injections of either RS102895 (3 g/l) 10 μl or 10 % DMSO 10 μl on day 9 to day 20 after operation. Pain thresholds of mechanical stimulation and thermal stimulation of each group were measured one day before and at 3rd, 6th, 9th, 12th, 15th, and 20th days after surgery. Spinal expression of NR2B, nNOS, and SIGIRR was detected by RT-PCR and Western blot. CCR2 antagonist RS102895 can suppress the pain induced by both mechanical and thermal stimulation in rats with BCP. Spinal expression of CCR2, NR2B, and nNOS was significantly up-regulated, while SIGIRR was down-regulated in BCP rats, and intrathecal injection of RS102895 effectively reversed the pattern of NR2B, nNOS, and SIGIRR expression in spinal cord. Analgesic effects of CCR2 antagonist RS102895 in BCP rats may be related to its downregulation of signal transduction pathway of NMDAR/nNOS and upregulation of Toll-interleukin-1 receptor member SIGIRR.

Detection of NMDARs Antibodies in Encephalitis

There is a range of diseases of the brain that are associated with rapidly developing inflammation. These conditions are called encephalitis, and can be caused by infections, or autoimmune disorders when the subject's immune system reacts against host proteins. The most common form of autoimmune encephalitis is associated with antibodies against the NR1 subunit of the N-Methyl-D-Aspartate Receptor (anti-NMDAR-encephalitis). Antibody detection is important for diagnosis, and can be performed only with techniques that preserve the full tertiary structure (conformation) of the antigen. Here, we describe the methods commonly used to detect NMDAR-antibodies with immunohistochemistry on rat brain slices and on live HEK cells transfected with components of the NMDAR.

Postpartum Anti-N-methyl-D-aspartate Receptor Encephalitis: A Case Report and Literature Review

We describe a 24-year-old woman with anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis that developed 3 weeks after normal delivery. She was treated with methylprednisolone, intravenous immunoglobulin, and plasmapheresis, in addition to teratoma excision. However, her recovery was slow, and dysmnesia and mental juvenility persisted even two years after onset. To date, five patients with postpartum anti-NMDAR encephalitis have been reported. All of those patients showed psychotic symptoms and were suspected of having postpartum psychosis in the early period of the encephalitis. Changes in hormonal factors, modification of immune tolerance, or retrograde infection of the ovary may be contributing factors for postpartum anti-NMDAR encephalitis.

Prevalence of serum anti-neuronal autoantibodies in patients admitted to acute psychiatric care

BACKGROUND

Autoimmune encephalitis associated with anti-neuronal antibodies may be challenging to distinguish from primary psychiatric disorders. The significance of anti-neuronal antibodies in psychiatric patients without clear evidence of autoimmune encephalitis is unknown. We investigated the serum prevalence of six anti-neuronal autoantibodies in a cohort of unselected patients admitted to acute psychiatric care.

METHOD

Serum was drawn from 925 patients admitted to acute psychiatric in-patient care. Psychiatric diagnoses were set according to International Classification of Diseases (ICD)-10 criteria. Antibody analysis was performed with an indirect immunofluorescence test for N-methyl d-aspartate receptor (NMDAR) antibodies and five other anti-neuronal autoantibodies of the immunoglobulin (Ig) classes IgA, IgG and IgM isotype.

RESULTS

Anti-neuronal autoantibodies were found in 11.6% of patients: NMDAR antibodies in 7.6%, contactin-associated protein-like 2 (CASPR2) antibodies in 2.5%, glutamic acid decarboxylase-65 (GAD65) antibodies in 1.9%, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antibodies in 0.1%. Leucine-rich glioma-inactivated protein-1 (LGI1) and γ-aminobutyric acid B (GABAB) receptor antibodies were not detected. NMDAR antibodies of class IgG were present in five patients only (0.5%). NMDAR antibodies of all Ig classes were equally prevalent in patients with and without psychosis. There were no significant differences in antibody prevalence in the different diagnostic categories, except for a higher odds ratio of being NMDAR antibody positive for patients without a specific psychiatric diagnosis.

CONCLUSIONS

NMDAR IgG autoantibodies, which are known to be strongly associated with anti-NMDAR encephalitis, were rarely found. CASPR2 and GAD65 antibodies were more frequently encountered in the present study than previously reported. Further research on the clinical significance of anti-neuronal autoantibodies in patients with acute psychiatric symptoms is needed.

[Anti-NMDA Receptor Antibody-Related Encephalitis]

Recently, the search for diagnostic antibody markers has drawn considerable attention in relation to autoimmune encephalitis. Among the antibody markers, the most frequently detected is the anti-N-methyl-D-aspartate receptor (NMDAR)antibody. Patients with this antibody develop characteristic clinical features. This disease tends to affect young women, and starts with psychiatric symptoms followed by seizures, involuntary movements, autonomic failure, and respiratory failure. Nearly half of these female patients have ovarian teratoma. Some of the patients with anti-NMDAR antibody show atypical clinical features. Approximately 4% show only psychiatric symptoms, which might lead to a diagnosis of malignant catatonia. Other reports describe patients experiencing refractory seizures to have the anti-NMDAR antibody. Some of the antibody-positive patients are associated with demyelinating disorders, and some develop anti-NMDAR encephalitis after recovery from herpes simplex encephalitis. It is important to test the anti-NMDAR antibody in these groups since immunotherapy ameliorates their symptoms. The anti-NMDAR antibody binds to the constitutional epitope at the extracellular domain of GluN1 and disrupts its function. Early introduction of immunotherapy together with tumor resection will results in improvement of neurological symptoms.

Redox dysregulation, neuroinflammation, and NMDA receptor hypofunction: A "central hub" in schizophrenia pathophysiology?

Accumulating evidence points to altered GABAergic parvalbumin-expressing interneurons and impaired myelin/axonal integrity in schizophrenia. Both findings could be due to abnormal neurodevelopmental trajectories, affecting local neuronal networks and long-range synchrony and leading to cognitive deficits. In this review, we present data from animal models demonstrating that redox dysregulation, neuroinflammation and/or NMDAR hypofunction (as observed in patients) impairs the normal development of both parvalbumin interneurons and oligodendrocytes. These observations suggest that a dysregulation of the redox, neuroimmune, and glutamatergic systems due to genetic and early-life environmental risk factors could contribute to the anomalies of parvalbumin interneurons and white matter in schizophrenia, ultimately impacting cognition, social competence, and affective behavior via abnormal function of micro- and macrocircuits. Moreover, we propose that the redox, neuroimmune, and glutamatergic systems form a "central hub" where an imbalance within any of these "hub" systems leads to similar anomalies of parvalbumin interneurons and oligodendrocytes due to the tight and reciprocal interactions that exist among these systems. A combination of vulnerabilities for a dysregulation within more than one of these systems may be particularly deleterious. For these reasons, molecules, such as N-acetylcysteine, that possess antioxidant and anti-inflammatory properties and can also regulate glutamatergic transmission are promising tools for prevention in ultra-high risk patients or for early intervention therapy during the first stages of the disease.

Anti-N-Methyl-D-Aspartate Receptor Encephalitis in Children and Adolescents

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disease that is becoming increasingly recognized in the pediatric population. It may be the most common cause of treatable autoimmune encephalitis. The majority of cases of anti-NMDAR encephalitis are idiopathic in etiology, but a significant minority can be attributed to a paraneoplastic origin. Children with anti-NMDAR encephalitis initially present with a prodrome of neuropsychiatric symptoms, often with orofacial dyskinesias followed by progressively worsening seizures, agitation, and spasticity, which may result in severe neurologic deficits and even death. Definitive diagnosis requires detection of NMDAR antibodies in the cerebrospinal fluid. Optimal outcomes are associated with prompt removal of the tumor in paraneoplastic cases, as well as aggressive immunosuppressive therapy. Early detection is essential for increasing the chances for a good outcome. Close follow-up is required to screen for relapse and later onset tumor presentation. The nurse practitioner plays a major role in the research, screening, diagnosis, treatment, follow-up, and rehabilitation of a child or adolescent with anti-NMDAR encephalitis.