Systematic review: clinical characteristics of anti-N-methyl-D-aspartate receptor encephalitis

Background

The number of reported cases of anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis has gradually increased since its discovery in 2007, while there are no uniform treatment guidelines.

Objective

To summarize the clinical characteristics of patients with anti-NMDAR encephalitis and to analyze the factors affecting the disease prognosis.

Methods

A systematic analysis of medical records was conducted, and PubMed, Embase, and Cochrane Library were searched from January 1, 2011, to December 31, 2021. Data were extracted, analyzed, and recorded in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.

Results

This study included 472 case reports. Most patients had prodromal symptoms of about 2 weeks, including psychiatric symptoms (53.2%), flu-like symptoms (51.5%), and seizures (23.9%), among others. Poor prognoses were associated with patients who had autonomic instability (p = 0.010), central hypoventilation (p = 0.014), and ICU support (p = 0.002). Patients with a higher age of onset were more likely to develop central hypoventilation (OR 1.024, CI 1.006-1.042, p = 0.009), cognitive impairment (OR 1.023, CI 1.009-1.037, p = 0.001), and memory impairment (OR 1.034, CI 1.017-1.050, p < 0.001), whereas patients with a lower age were more likely to have seizures (OR 0.979, CI 0.965-0.993, p = 0.003). In this study, 97.0% of patients received immunotherapy, with the most commonly used treatment regimen being intravenous methylprednisolone (IVGC) and intravenous immunoglobulin (IVIG). When compared with other treatment regimens, the IVGC+IVIG regimen (p < 0.001) resulted in better prognoses.

Conclusion

When encountering patients with fever, headache, and initial psychiatric symptoms of unknown etiology, clinicians should test their CSF for antibodies to distinguish autoimmune encephalitis. Patients with autonomic instability, central hypoventilation, and ICU support had poorer prognoses. Clinicians should be aware that older patients are more likely to develop central hypoventilation, cognitive impairment, and memory impairment, while younger patients are more likely to develop seizures. The IVGC+IVIG treatment regimen has better prognoses than others. This study includes case reports, which have obvious selection bias, and there are no unified standards to measure the severity of the disease. Therefore, in the future, larger samples and randomized controlled trials are needed to evaluate the efficacy of different treatment regimens.

Myelinating Co-Culture as a Model to Study Anti-NMDAR Neurotoxicity

Anti-NMDA receptor (NMDAR) encephalitis is frequently associated with demyelinating disorders (e.g., multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein-associated disease (MOGAD)) with regard to clinical presentation, neuropathological and cerebrospinal fluid findings. Indeed, autoantibodies (AABs) against the GluN1 (NR1) subunit of the NMDAR diminish glutamatergic transmission in both neurons and oligodendrocytes, leading to a state of NMDAR hypofunction. Considering the vital role of oligodendroglial NMDAR signaling in neuron-glia communication and, in particular, in tightly regulated trophic support to neurons, the influence of GluN1 targeting on the physiology of myelinated axon may be of importance. We applied a myelinating spinal cord cell culture model that contains all major CNS cell types, to evaluate the effects of a patient-derived GluN1-specific monoclonal antibody (SSM5) on neuronal and myelin integrity. A non-brain reactive (12D7) antibody was used as the corresponding isotype control. We show that in cultures at the late stage of myelination, prolonged treatment with SSM5, but not 12D7, leads to neuronal damage. This is characterized by neurite blebbing and fragmentation, and a reduction in the number of myelinated axons. However, this significant toxic effect of SSM5 was not observed in earlier cultures at the beginning of myelination. Anti-GluN1 AABs induce neurodegenerative changes and associated myelin loss in myelinated spinal cord cultures. These findings may point to the higher vulnerability of myelinated neurons towards interference in glutamatergic communication, and may refer to the disturbance of the NMDAR-mediated oligodendrocyte metabolic supply. Our work contributes to the understanding of the emerging association of NMDAR encephalitis with demyelinating disorders.

Association between clinical factors and orofacial dyskinesias in anti-N-methyl-D-aspartate receptor encephalitis

BACKGROUND AND PURPOSE

We aimed to determine whether demographic information, clinical characteristics, laboratory tests, and imaging features are associated with orofacial dyskinesias (OFLD) in patients with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis.

METHODS

In this retrospective study, patients who were diagnosed with anti-NMDAR encephalitis were enrolled. All patients' factors, including demographic information, clinical characteristics, laboratory tests, and imaging features, were obtained at the time of hospitalization. The neurological function was assessed using the modified Rankin scale (mRS). Univariate and multivariate logistic regressions were used to examine the associations between clinical factors and OFLD.

RESULTS

In total, 119 patients (median age: 28.0 [19.0-41.0] years; 67 females) were recruited. Of 119 patients, 44 (37.0%) had OFLD. OFLD was associated with increased mRS at admission, serum sodium, lumbar puncture pressure, female biologic sex, fever, psychiatric symptoms, seizures, impaired consciousness, autonomic dysfunction, and central hypoventilation in univariate logistic regression, respectively. Multivariate regression analysis revealed that female biologic sex (odds ratios [OR], 4.73; 95% confidence interval [CI], 1.27-17.64; p = .021), increased mRS at admission (OR, 2.09; 95% CI, 1.18-3.71; p = .011), psychiatric symptoms (OR, 7.27; 95% CI, 1.20-43.91; p = .031), and seizures (OR, 5.11; 95% CI, 1.22-21.43; p = .026) were associated with OFLD, after adjusting for confounding factors.

CONCLUSIONS

Our analysis suggests that the following clinical factors are associated with OFLD: female biologic sex, increased mRS at admission, psychiatric symptoms, and seizures.

Long-term seizure outcomes in patients with autoimmune encephalitis: A prospective observational registry study update

OBJECTIVE

To update and evaluate long-term seizure outcomes in patients with autoimmune encephalitis (AE) based on a large cohort study with long follow-up.

METHODS

In this prospective observational registry study, we analyzed data from patients with AE mediated by common types of neuronal surface antibodies (anti-NMDAR, anti-LGI1/Caspr2, anti-GABA_B R). All patients were recruited from the Department of Neurology at the West China Hospital between October 2011 and June 2019, and data were collected prospectively on their demographic and clinical characteristics, treatment strategy, and seizure outcomes with a median follow-up of 42 months (range 6-93 months). Potential risk factors associated with seizure recurrence were also assessed.

RESULTS

Of 320 AE patients, 75.9% had acute seizures, among whom more than 90% of patients had their last seizure within 12 months of disease onset. During our follow-up, 21 (9.3%) patients experienced seizure recurrence. Patients with anti-GABA_B R encephalitis had a higher cumulative incidence of seizure recurrence than those with anti-NMDAR (log-rank P = 0.03) or anti-LGI1/Caspr2 encephalitis (log-rank P = 0.04). Among patients with anti-NMDAR encephalitis, women had a significantly higher cumulative incidence of seizure recurrence than men (log-rank P = 0.01). Interictal epileptiform discharges (IEDs) or seizures captured on continuous EEG in the acute phase were identified as potential risk factors for seizure recurrence (P=0.04; P=0.007). Among 163 patients with ≥ 24 months of follow-up, five (3.1%) showed persistent seizures and required ongoing anti-seizure medications (ASMs) despite aggressive immunotherapy.

SIGNIFICANCE

Seizure recurrence occurred in a small number of patients and chronic epilepsy occurred in 3.1% of patients during prolonged follow-up. Across all types of AE, risk factors for seizure recurrence were IEDs or seizures captured on EEG in the acute phase; for anti-NMDAR encephalitis, female sex was also a risk factor.

Case Report: Cotard's Syndrome in Anti-N-methyl D-aspartate (NMDA) Receptor (Anti-NMDAR) Encephalitis

Cotard's syndrome is uncommon psychopathology among patients with psychotic illnesses. Limited cases had been reported regarding the occurrence of this syndrome in anti-NMDAR encephalitis which itself is a relatively new disease that often presents with florid psychotic symptoms. This poses difficulties in differentiating it from a primary psychiatric illness. Late recognition of anti-NMDAR encephalitis can lead to death as it can progress to autonomic instability in its natural course of illness. We report a patient who first presented with psychotic symptoms with initial negative findings from baseline investigations. Further investigation revealed anti NMDAR antibodies in the cerebrospinal fluid. Prompt treatment was initiated and despite early poor response to the first-line treatment with the development of allergic reaction, our patient recovered completely after 1 month of hospitalization. This case report aims to highlight the importance of early detection of anti-NMDAR encephalitis and the possibility of uncommon psychopathology such as Cotard's syndrome occurring in this disease.

Neuropsychological Sequelae, Quality of Life and Adaptive Behavior in Children and Adolescents with Anti-NMDAR Encephalitis: A Narrative Review

Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is a rare autoimmune illness characterized by a constellation of often severe, but treatable, psychiatric and neurological symptoms. Whereas symptoms such as psychosis and bizarre and abnormal motor behavior are common in adults, pediatric patients typically present with behavioral changes, irritability and sleep dysfunction. The recovery phase is usually slow and may be associated with longstanding adaptive, behavioral and neuropsychological problems. Very few studies explored the cognitive and adaptive sequelae in children with anti-NMDAR encephalitis. The present review article suggests that, although most children and adolescents return to their daily life and previous activities, they may have a low quality of life and show neuropsychological sequelae involving language, memory, especially verbal memory, and attentional resources, even after several months from the hospital discharge. In particular, the available results reveal difficulties in cognitive skills involving executive functions. This impairment is considered the “core” of the cognitive profile of young patients with anti-NMDAR encephalitis. On the other hand, some cognitive skills, such as general intelligence, show good overall recovery over time. Additional neuropsychological research evaluating larger samples, more homogenous methods and longitudinal studies is required.

Seroprevalence of Anti- N-methyl-D-aspartate receptor antibodies in children with seizures of unknown cause

BACKGROUND

Anti- N-methyl-D-aspartate receptor (NMDAR) antibodies were found most probably to be accompanied by seizures, particularly in children and sometimes it may be the sole presenting feature. Therefore, testing these antibodies in children with seizure of unexplained cause might be helpful to identify the spectrum of these antibody-mediated disorders. The objective of this study was to determine the frequency of anti-NMDAR antibodies in patients who presented with seizures of unknown cause.

METHODS

A case-control study was conducted in two hospitals in Medical City Complex-Baghdad in 2019. Children aged 2-18 years who manifested seizures solely without identified causes were recruited over a period of ten months, with an additional sex- and age-matched control group (forty children in each group). Serum was tested in both groups for anti-NMDAR antibodies.

RESULTS

In the study group, males predominated in ages younger than 5 years. The mean age was 6.6 years and the mean duration since their seizures` onset was 2 months. In contrast to male patients, female patients manifested more focal seizures. Only 5 patients (12.5%) were positive for Anti- NMDAR antibodies, in contrast to no one in the control group. Significantly, most of the seropositive patients were females (4, 80%) and showed focal types of seizures (4, 80%).

CONCLUSIONS

This is a preliminary epidemiological study about the prevalence of anti-NMDAR antibodies in a sample of pediatric patients with isolated seizures of unknown cause. Anti-NMDAR antibodies were found to be prevalent in a relatively small proportion of children who presented with seizures of unknown causes. Demographic characteristics of the patients with variable testing status were found to be nearly comparable to the results from other related studies.

Leptospira Triggered Anti-N-Methyl-d-Aspartate Receptor Encephalitis

Primary neuroleptospirosis although rare but has been reported in the literature in the form of case reports and case series. However, there are no reports of autoimmune encephalitis triggered by leptospirosis in the literature, although four cases of acute disseminated encephalomyelitis, which is also considered to have autoimmune etiology have been reported. We are reporting an adolescent girl, who developed anti-N-methyl-d-aspartate receptor encephalitis after the resolution of systemic symptoms of leptospirosis. Her symptoms including neuropsychiatric and extrapyramidal features and sleep disturbances resolved completely after immunotherapy. As recently autoimmune encephalitis triggered by various infections are getting reported more frequently around the world, the clinicians need to consider this clinical possibility, even in patients with leptospirosis, who develop neurological symptoms while systemic clinical features are subsiding. Early recognition and timely administration of immunotherapy have the potential to completely reverse the neurological symptoms.

Search for Viral Infections in Cerebrospinal Fluid From Patients With Autoimmune Encephalitis

Background

It has been reported that virus-mediated brain tissue damage can lead to autoimmune encephalitis (AE) characterized by the presence of antibodies against neuronal surface antigens. In the study, we investigate the presence of viruses in cerebrospinal fluid (CSF) from patients with AE using reverse transcription polymerase chain reaction (RT-PCR)/PCR and shotgun metagenomics.

Methods

CSF samples collected from 200 patients with encephalitis were tested for the presence of antibodies against antiglutamate receptor (NMDAR), contactin-associated protein 2 (CASPR2), glutamate receptors (type AMPA1/2), leucine-rich glioma-inactivated protein 1 (LGI1), dipeptidyl aminopeptidase-like protein 6 (DPPX), and GABA B receptor, and those found positive were further analyzed with real-time RT-PCR/PCR for common viral neuroinfections and shotgun DNA- and RNA-based metagenomics.

Results

Autoantibodies against neuronal cells were detected in CSF from 8 individuals (4% of all encephalitis patients): 7 (3.5%) had anti-NMDAR and 1 (0.5%) had anti-GABA B. RT-PCR/PCR identified human herpes virus type 1 (HSV-1; 300 copies/mL) and the representative of Enterovirus genus (550 copies/mL) in 1 patient each. Torque teno virus (TTV) was found in another patient using metagenomic analysis, and its presence was confirmed by specific PCR.

Conclusions

We detected the presence of HSV, TTV, and Enterovirus genus in CSF samples from 3 out of 8 AE patients. These findings support the concept of viral involvement in the pathogenesis of this disease.

A Pounding Problem: A Case of Recurrent Headache Caused by Anti-NMDA Receptor Encephalitis

BACKGROUND

Anti-N-methyl-d-aspartate receptor (Anti-NMDAR) encephalitis is a serious autoimmune disease in which antibody production against the NMDA receptor results in profound neurotransmitter dysregulation. Patients may present with a wide variety of symptoms, including psychosis, orofacial dyskinesias, dysautonomia, hallucinations, mental status changes, seizures, and headaches.

CASE REPORT

A previously healthy 25-year-old woman presented on several occasions to the Emergency Department with a severe pounding headache that initially responded well to treatment. She later developed signs consistent with meningoencephalitis along with altered mental status and neuropsychiatric changes. She was diagnosed with anti-NMDAR encephalitis after hospitalization. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Anti-NMDAR encephalitis is an under-recognized condition with diverse presentations. Recurrent headaches that improve with treatment may be an early sign of this disorder. Anti-NMDAR encephalitis should be considered in patients with recurrent undifferentiated headaches, and an appropriate work-up should be performed. Early recognition and diagnosis of this condition is critical to optimize favorable patient outcomes, as delays to diagnosis may lead to fatalities and long-term neurologic sequelae.

Evaluation of the proposed anti-N-methyl-d-aspartate receptor encephalitis clinical diagnostic criteria in psychiatric patients

OBJECTIVE

The gold standard for diagnosing anti-NMDAR encephalitis is demonstration of the antibody in CSF. Clinical diagnostic criteria have been proposed for when this is not available in a timely manner which is evaluated, in this study, for a psychiatric population.

METHODS

This study retrospectively assessed the proposed criteria in patients presenting to psychiatric services for the first time with known anti-NMDAR antibody status. Antibody-positive cases were derived from the literature (conception to December 2019) and a state-wide (Queensland, Australia) cohort. Antibody-negative cases were derived from a service-wide (Metro South, Queensland, Australia) cohort of psychiatric cases which underwent antibody testing for routine organic screening. Sensitivity and specificity were calculated at 1 week following admission and the point of discharge.

RESULTS

The proposed criteria were applied to 641 cases (500 antibody-positive and 141 antibody-negative), demonstrating a sensitivity which increased from around 19% after 1 week to 49% by the point of discharge. Specificity was 100% at both time points. The mean average time to become positive using the proposed criteria was 19.5 days compared to 34.9 days for return of antibody testing.

CONCLUSIONS

High specificity of the proposed criteria, seen in this study, suggests that cases which are positive can be considered for expedited commencement of treatment. However, if clinical suspicion is high despite criteria being negative, it is essential to test CSF for anti-NMDAR antibody.

Anti-NMDAR Encephalitis: A Multidisciplinary Approach to Identification of the Disorder and Management of Psychiatric Symptoms

BACKGROUND

The novelty of anti-NMDA receptor encephalitis, for which somatic treatments have only recently been developed, has led to a lack of information on assessment and treatment of its variable behavioral manifestations.

METHOD

In this article, we discuss 4 challenging cases of anti-NMDAR encephalitis, focusing on the importance of a multidisciplinary approach to identification and management of the disorder and the necessity of close collaboration in the acute hospital setting for management of the behavioral symptoms.

CONCLUSION

The cases we discuss highlight some of the medication and nonpharmacologic treatment strategies that may facilitate management of psychiatric symptoms, both while the medical workup is ongoing and after the diagnosis has been confirmed.

NMDAR Encephalitis Associated With Acute Chikungunya Virus Infection: A New Trigger?

Background: Anti-NMDAR encephalitis is the most frequent cause of autoimmune encephalitis. Chikungunya (CHIK) is an arbovirus responsible for outbreaks of fever, cutaneous rash and arthritis in underdeveloped countries, and a trigger for autoimmunity. Case Presentation: We report a five-year-old male patient with fever, myalgia, headache and conjunctivitis for 5 days. After 1 week he developed tonic-clonic seizures and evolved with dystonia and oromandibular dyskinesia followed by onset of focal motor seizures, decreased level of consciousness, dysautonomia and central apnea. Brain MRI was normal, CSF analysis revealed 15 cells, protein 16.6 mg/dL and glucose 68 mg/dL. Anti-NMDAR antibodies were detected in serum and CSF after 3 weeks of symptom onset. CHIK serology was positive for both IgM and IgG, suggesting a recent infection. Dengue and Zika serologies were negative. CSF PCR for herpes viruses and arboviruses (CHIK, Dengue and Zika) were negative. Conclusion: We report the occurrence of anti-NMDAR encephalitis after acute CHIK infection. The biphasic course, positivity for both CHIK IgM and IgG and negative CHIK CSF PCR results, as well as a dramatic response to immunotherapy suggest an immune-mediated pathogenesis. Because of the global epidemic of CHIK infection and unknown mechanisms involving CHIK and autoimmunity, patients with acute CHIK infections and neurological manifestations should be considered for antineuronal antibody testing.

Anti-NMDA receptor encephalitis: a case study and illness overview

Anti-N-methyl D-aspartate (NMDA) receptor (anti-NMDAR) encephalitis is among one of the most common autoimmune encephalitides. However, variations in clinical presentation and nonsequential multiphasic course often lead to delays in diagnosis. The mild encephalitis (ME) hypothesis suggests a pathogenetic mechanism of low-level neuroinflammation sharing symptom overlap between anti-NMDAR encephalitis and other psychiatric disorders including schizophrenia. Clinical symptoms of anti-NMDAR encephalitis may mimic schizophrenia and psychotic spectrum disorders or substance-induced psychosis. Although initially described in association with ovarian teratomas in women, anti-NMDAR encephalitis has been reported in individuals without paraneoplastic association, as well as in males. It can affect all age groups but is usually lower in prevalence in individuals greater than 50 years old, and it affects females more than males. Clinical evaluation is supported by laboratory workup, which includes cerebrospinal fluid (CSF) assays. The latter often reveals lymphocytic pleocytosis or oligoclonal bands with normal to elevated CSF protein. CSF testing for anti-NMDAR antibodies facilitates diagnostic confirmation. Serum anti-NMDAR antibody assays are not as sensitive as CSF assays. Management includes symptomatic treatment and immunotherapy.

A case report: anti-NMDA receptor encephalitis

N-methyl-d-aspartate receptor (NMDAR) antibody encephalitis is a potentially fatal autoimmune syndrome in which there is antibody production against the NMDAR causing profound dysregulation of neurotransmission. The syndrome is frequently associated with ovarian teratomas and women are disproportionately affected. Patients most often present with a constellation of neuropsychiatric signs and symptoms, including memory loss, hallucinations, and decreased level of consciousness. This condition is lethal if left untreated. Immunotherapy and surgical resection of the culprit malignancy often results in the rapid resolution of symptoms.

Rituximab for Treatment of Refractory Anti-NMDA Receptor Encephalitis in a Pediatric Patient

Anti-N-methyl d-aspartate receptor (anti-NMDAR) encephalitis is a devastating disease that is increasingly being identified in both children and adults with psychosis, language disturbances, behavioral changes, and motor deficits. Currently no consensus guidelines exist for the optimal management of patients with this disease, although intravenous immune globulin (IVIG) therapy is often considered first-line pharmacotherapy. We present a case of an otherwise healthy 4 year-old-child who presented with seizures, loss of age-appropriate language skills, and behavioral changes, in whom anti-NMDAR was subsequently diagnosed. After marked intolerance to corticosteroid therapy and inadequate clinical response to IVIG, immunotherapy with rituximab was initiated. The patient had rapid return of language skills and complete resolution of dyskinesia after a single rituximab infusion, with no residual deficits at her 6-month follow-up visit. Early intervention in patients with anti-NMDAR encephalitis is of paramount importance for successful outcomes and baseline recovery. Only approximately half of patients respond to first-line immunotherapy, necessitating further evaluation of alternative therapies and the development of a treatment algorithm for practitioners. This case report builds upon previous findings illustrating rapid symptom resolution after rituximab infusion and adds to the available body of evidence for management of pediatric patients with anti-NMDAR.

Diagnostic pitfalls in a young Romanian ranger with an acute psychotic episode

The identification and distinction of the pathological conditions underlying acute psychosis are often challenging. We present the case of a 35-year-old ranger who had no history of acute or chronic infectious disease or any previous neuropsychiatric symptoms. He arrived at the Psychiatry Clinic and was admitted as an emergency case, displaying bizarre behavior, hallucinations, paranoid ideation, and delusional faults. These symptoms had first appeared 7 days earlier. An objective examination revealed abnormalities of behavior, anxiety, visual hallucinations, choreiform, and tic-like facial movements. After the administration of neuroleptic and antidepressant treatment, he showed an initial improvement, but on day 10 entered into a severe catatonic state with signs of meningeal irritation and was transferred to the intensive care unit. An electroencephalogram showed diffuse irritative changes, raising the possibility of encephalitis. Taking into consideration the overt occupational risk, Borrelia antibody tests were prescribed and highly positive immunoglobulin (Ig)M and IgG titers were obtained from serum, along with IgG and antibody index positivity in cerebrospinal fluid. In parallel, anti-N-methyl-D-aspartate receptor antibodies and a whole battery of other autoimmune encephalitis markers showed negative. A complex program of treatment was applied, including antibiotics, beginning with ceftazidime and ciprofloxacin - for suspected aspiration bronchopneumonia - and thereafter with ceftriaxone. A gradual improvement was noticed and the treatment continued at the Infectious Disease Clinic. Finally, the patient was discharged with a doxycycline, antidepressant, and anxiolytic maintenance treatment. On his first and second control (days 44 and 122 from the disease onset), the patient was stable with no major complaints, Borrelia seropositivity was confirmed both for IgM and IgG while the cerebrospinal fluid also showed reactivity for IgG on immunoblot. On the basis of the putative occupational risk, acute psychotic episode, and the success of antibiotic therapy, we registered this case as a late neuroborreliosis with atypical appearance.

Does MAP2 have a role in predicting the development of anti-NMDAR encephalitis associated with benign ovarian teratoma? A report of six new pediatric cases

Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is a potentially fatal neurologic syndrome in which patients present with a spectrum of central nervous system deficits. Sixty percent of the cases can be attributed to the presence of tumors, most often ovarian teratomas. This report examines 6 pediatric patients who presented with neurologic deficits associated with the presence of such tumors. These cases illustrate a perplexing phenomenon, where benign teratomas could have a possible association with anti-NMDAR encephalitis. The purpose of this study was to compare the histology and immunohistochemistry of tumors associated with this syndrome to ovarian teratomas found in patients presenting with no neurologic symptoms. After obtaining institutional review board approval, 57 cases of ovarian teratomas were identified at our institution over 12 years. Six patients were identified with anti-NMDAR encephalitis. A panel of immunostains, including S100, GFAP, MAP2, and NeuN was applied to patients' tumor sections as well as the 6 controls from age-matched patients. No qualitative histologic or immunohistochemical differences were seen between the study cases and control group. Because no qualitative differences were identified between the study cases and the control group, testing of paired serum and cerebrospinal fluid remains the best method for diagnosis of anti-NMDAR encephalitis. Tumor banking with molecular analysis of ovarian teratomas, including whole-genome sequencing and comparative genomic hybridization between ovarian tissue saved from patients with and without anti-NMDAR encephalitis, is necessary to fully understand the etiopathogenesis of anti-NMDAR encephalitis.