Japanese encephalitis-induced anti-N-methyl-d-aspartate receptor encephalitis: A hospital-based prospective study

ObjectivesA hospital-based prospective study was performed to determine: 1) whether Japanese encephalitis (JE) normally triggers anti-N-methyl-d-aspartate receptor (NMDAR) immunoglobulin G (IgG) synthesis, especially in monophasic JE patients; and 2) the incidence of JE-induced anti-NMDAR encephalitis in pediatric patients with JE.MethodsWe detected the level of anti-NMDAR IgG in the serum and cerebral spinal fluid (CSF) of JE patients within one week of onset. If patients relapsed during the convalescence phase, we detected JE virus RNA in the CSF and anti-NMDAR IgG in both the serum and CSF. For patients who did not relapse during the convalescence phase, serum was collected and anti-NMDAR IgG was detected during the 30–60-day course of the disease.ResultsWe enrolled 65 JE patients, who were negative for anti-NMDAR IgG in the serum and CSF during the acute phase, of which 63 patients were successfully followed up. Five patients relapsed during the convalescence phase, for whom JE virus RNA in the CSF was negative and excluded latent JE reactivation. The distinctive symptoms of four younger patients were choreoathetosis, whereas the psychiatric and behavioral manifestations were the distinctive symptoms experienced by the teenager. Anti-NMDAR IgG in the CSF of three patients was positive and they were diagnosed with anti-NMDAR encephalitis. The other two patients were negative for anti-NMDAR IgG in both the serum and CSF. For the 58 patients who did not relapse during the convalescence phase, anti-NMDAR IgG was negative in the serum of all patients at 30–60 days during the course of the disease.ConclusionsJE does not typically trigger anti-NMDAR IgG synthesis. Besides anti-NMDAR IgG, other unknown autoantibodies can also cause autoimmune encephalitis in the convalescence phase of JE. The incidence of JE-induced autoimmune encephalitis in pediatric patients with JE was 7.9%, and the incidence of JE-induced anti-NMDAR encephalitis was 4.7%.     

Suppression of synaptic plasticity by cerebrospinal fluid from anti-NMDA receptor encephalitis patients

The functional effects of cerebrospinal fluid (CSF) from patients with anti-NMDA receptor (NMDAR) encephalitis on the NMDAR-mediated synaptic plasticity were evaluated by using mouse hippocampus slices. Anti-NMDAR antibody detection system was established by immunostaining recombinant NMDAR heteromers expressed in HEK cell culture as well as native NMDARs in cultured hippocampal neurons. Under a complete blind manner for the clinical information, CSF and sera collected from 36 pre-diagnosed patients were tested for anti-NMDAR antibodies. With this test, thirteen patients were diagnosed as anti-NMDAR encephalitis. CSF positive for anti-NMDAR antibodies suppressed induction of long-term potentiation (LTP) at Schaffer collateral-CA1 synapses in mouse hippocampal slices. LTP induction was not suppressed by CSF collected from herpes simplex virus (HSV) encephalitis or non-encephalitis control patients. Antibody absorption with NMDAR-expressing HEK cell culture reversed the suppression of LTP by anti-NMDAR encephalitis patients' CSF, confirming that anti-NMDAR antibodies suppressed LTP. The present experiments firmly support the proposal that the anti-NMDAR encephalitis autoantibody is responsible for cognitive disorders like amnesia accompanying this disease.     

Anti-<Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="SmallCaps">d</Emphasis>-aspartate receptor encephalitis: a common cause of encephalitis in the intensive care unit

Anti-N-methyl-d-aspartate receptor encephalitis (anti-NMDAR encephalitis) is the most common type of immune-mediated encephalitis. This study aimed to assess the incidence and mortality of anti-NMDAR encephalitis in intensive care unit (ICU) to evaluate the clinical manifestations, laboratory findings, managements and outcomes, and to compare these characteristics with patients with non-anti-NMDAR encephalitis admitted to ICU. Patients admitted to the neurological ICU with suspected encephalitis were included between January 1, 2012 and July 31, 2015. Cerebrospinal fluid (CSF) of enrolled patients was screened for anti-NMDAR antibodies using a cell-based assay. 72 critically ill patients with encephalitis of uncertain etiology were investigated, and 16 patients were positive for anti-NMDAR antibodies in CSF. Compared to patients with non-anti-NMDAR encephalitis, patients with anti-NMDAR encephalitis were younger, more likely to present with the psychiatric symptoms, dyskinesia, and autonomic dysfunction, and had longer ICU stays. The abnormal movements were so difficult to control that complicated the management. The outcome was favorable in ten patients 1 year after the disease onset, and the mortality was as high as 25 % overall. The incidence of anti-NMDAR encephalitis is high among critically ill patients with encephalitis of uncertain etiology. Controlling dyskinesia proved to be a challenge. Persistent dysautonomias were additional difficult to manage confounders. Same points being highlighted in this study may aid clinicians in the management of patients with anti-NMDAR encephalitis in intensive care practice.     

Late relapse of anti-N-methyl-d-aspartate receptor encephalitis with amusia and transiently reduced uptake in 123I-iomazenil single-photon emission computed tomography

IntroductionAnti-N-methyl-d-aspartate receptor (NMDAR) encephalitis has a high relapse rate at approximately 10–20%. Most relapses occur within 2 years from onset, and 5 years after onset is rare. We report a case of anti-NMDAR encephalitis relapse with amusia 10 years after the initial encephalitis and discuss the usefulness of ¹²³I-iomazenil single-photon emission computerized tomography (IMZ-SPECT) for its diagnosis.CaseA 13-year-old left-handed girl presented with a depressed level of consciousness and focal to bilateral tonic-clonic seizures. Cerebrospinal fluid (CSF) analysis showed a mildly increased white blood cell count, elevated neopterin levels, and positive oligoclonal bands. Brain MRI was normal. IMZ-SPECT revealed reduced uptake in the right frontoparietal region. She received intravenous pulse methylprednisolone (IVMP) and high-dose intravenous immunoglobulin for autoimmune encephalitis; her symptoms resolved without neurological deficits. At 23 years old, she had mild right-sided numbness, dysarthria, amusia, and tonic-clonic seizures. Although the CSF analysis and brain MRI were normal, IMZ-SPECT revealed reduced uptake, indicating a relapse of encephalitis. IVMP administration resolved the symptoms. After discharge, the initial and relapse CSF analysis revealed anti-NMDAR antibodies.ConclusionAn anti-NMDAR encephalitis relapse 10 years after onset has never been reported. IMZ-SPECT may help in the diagnosis of anti-NMDAR encephalitis.     

Absent anti-N-methyl-D-aspartate receptor NR1a antibodies in herpes simplex virus encephalitis and varicella zoster virus infections

Purpose: A 2012 report and subsequent case series described anti-N-methyl-D-aspartate receptor (NMDAR) antibodies in patients during the acute phase and relapse of herpes simplex virus 1 (HSV1) encephalitis (HSV1E). However, the prevalence of this phenomenon is unknown and systematic studies on other viral infections of the nervous system are missing. Materials and methods: We retrospectively analyzed serial cerebrospinal fluid (CSF) and serum samples of consecutive patients treated for neurological HSV1, HSV2 and varicella zoster virus (VZV) infections in our tertiary care university hospital between 2003 and 2013 for the presence of antibodies directed against the NR1a subunit of the NMDAR using indirect immunofluorescence. Results: In total, 88 patients with the following infections were identified through an electronic database search: HSV1 (24 with encephalitis), HSV2 (6 with meningitis, 3 with encephalitis and 1 with myelitis), or VZV (3 with meningitis, 33 with encephalitis, 17 with radiculitis and 1 with myelitis). Two patients with HSV1E and HSV2E, respectively, experienced a clinical relapse. Clinical follow-up was for up to 85 months, and repetitive serum and CSF analyses for up to 43 months. However, at no time did any of the 88 patients exhibit anti-NMDAR NR1a antibodies. Conclusions: In this study, we did not detect anti-NMDAR NR1a antibodies in serial CSF and serum samples of HSV1E patients or patients with other viral infections (HSV2 and VZV). However, the presence of antibodies directed against other epitopes of the NMDAR and other neuronal cell surface antigens cannot be excluded, necessitating further studies.     

Anti-N-Methyl-D-Aspartate Receptor Encephalitis in Korea: Clinical Features,Treatment, and Outcome

Background and Purpose

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is the most common type of autoimmune synaptic encephalitis and it often responds to treatment. We analyzed the clinical characteristics of anti-NMDAR encephalitis in Korea.

Methods

Serum and/or cerebrospinal fluid (CSF) of adult patients (aged ≥18 years) with encephalitis of undetermined cause were screened for anti-NMDAR antibodies using a cell-based indirect immunofluorescence assay. The patients came from 41 university hospitals.

Results

Of the 721 patients screened, 40 were identified with anti-NMDAR antibodies and clinical details of 32 patients were obtained (median age, 41.5 years; 15 females). Twenty-two patients (68.8%) presented with psychiatric symptoms, 16 (50%) with seizures, 13 (40.6%) with movement disorders, 15 (46.9%) with dysautonomia, 11 (34.4%) with memory disturbance, and 11 (34.4%) with speech disturbance. Magnetic resonance imaging, electroencephalography, and CSF examinations yielded nonspecific findings. Tumor information was only available for 22 patients: 5 patients had tumors, and 2 of these patients had ovarian teratomas. Twenty-two patients received immunotherapy and/or surgery, and therapeutic responses were analyzed in 21 patients, of which 14 (66.7%) achieved favorable functional outcomes (score on the modified Rankin Scale of 0-2).

Conclusions

This study investigated the clinical characteristics of adult anti-NMDAR encephalitis in Korea. Currently, elderly patients who do not have tumors are commonly diagnosed with this condition. Understanding the detailed clinical characteristics of this disease will improve the early detection of anti-NMDAR encephalitis in patients both young and old.     

Arterial spin labeling perfusion imaging in an infant with anti-N-methyl-D-aspartate receptor encephalitis: A case report

BackgroundAnti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is an autoimmune encephalitis characterized by complex neuropsychiatric syndromes and the presence of cerebrospinal fluid (CSF) antibodies against NMDAR. The characteristics of anti-NMDAR encephalitis in children, particularly infants, are unclear due to difficulties in neurologic assessment such as psychiatric symptoms. Additionally, subtle or non-specific findings of conventional magnetic resonance imaging (MRI) make early diagnosis even more difficult. Herein, we present the first case of infant anti-NMDAR encephalitis in which perfusion imaging demonstrated marked abnormalities and the absence of conventional MRI findings.Case presentationThe patient was an 11-month-old boy who was admitted because of seizure and prolonged fever. He presented with involuntary movements of the mouth and tongue. Brain MRI showed no morphological abnormalities, but three-dimensional arterial spin labeling (ASL) perfusion imaging showed reduced blood flow in the left temporal and frontal regions and the right cerebellum. After that, a positive anti-NMDAR antibody test result was received. Despite treatment with IVIG and methylprednisolone, the involuntary movements and autonomic dysfunction gradually became more prominent. After rituximab administration, the clinical symptoms improved slightly, and follow-up MRI revealed diffuse brain atrophy and improvement in the balance of brain perfusion.ConclusionsTo the best of our knowledge, this is the first case report of infantile anti-NMDAR encephalitis in which cerebral blood flow was evaluated using three-dimensional ASL perfusion imaging. Indeed, our case, which showed abnormalities only in ASL perfusion imaging, suggests that CBF assessment could aid in the early diagnosis of anti-NMDAR encephalitis in infants.     

晚发型抗N-甲基-D-天冬氨酸受体脑炎临床特征分析

目的分析晚发型抗N-甲基-D-天冬氨酸受体(NMDAR)脑炎的临床特征。方法收集2010-01-01—2019-05-01于郑州大学第一附属医院住院确诊为抗NMDAR脑炎的患者临床资料,分析晚发型(≥50岁)患者数据,并与早发型(18~49岁)患者进行对比。结果18例晚发型患者中,男11例(61%),发病年龄50~84岁。晚发型患者中,9例(50%)患者出现前驱症状,精神行为异常是最常见的首发症状(44%)和临床表现(78%);头颅磁共振提示脑实质炎性病变9例(9/17,53%);脑脊液检验结果异常17例(94%);合并肿瘤4例(22%),均非畸胎瘤。相比于早发组患者,晚发组患者有更高的自主神经功能障碍比例(72%vs 45%,P=0.032),更高的岛叶病变比例(67%vs 27%,P=0.047),更高的脑脊液蛋白升高比例(56%vs 28%,P=0.023),以及更高的脑脊液鞘内IgG合成率升高比例(73%vs 44%,P=0.041)。晚发组合并肿瘤均非畸胎瘤,早发组合并肿瘤均为畸胎瘤(P=0.001)。结论相比早发型抗NMDAR脑炎患者,晚发型患者更易出现岛叶病变,更易出现脑脊液炎症反应,其发病机制可能与畸胎瘤不相关。     

CSF findings in patients with voltage gated potassium channel antibody associated limbic encephalitis

Recently, a new subtype of limbic encephalitis (LE) has been described, serologically characterized by the presence of antibodies against voltage gated potassium channels (VGKC, to be called VGKC-LE). Only little is known about CSF findings in this new disorder. Here we report the results of 29 lumbar punctures in 17 patients with VGKC-LE. Slight pleocytosis, mainly consisting of lymphocytes and monocytes, and elevated total protein concentrations were present in 41 and 47%, respectively. Intrathecal immunoglobulin (Ig) synthesis as defined by the presence of CSF-specific oligoclonal IgG bands, an increased IgG index, or an elevated IgG, IgA, or IgM ratio, was not detected in any of the patients, but dysfunction of the blood-CSF barrier was found in 35%. CSF findings were normal in 23%. Conclusions: Unlike paraneoplastic LE, VGKC-LE is not frequently associated with intrathecal Ig production or markedly elevated white cell counts. Thus, normal CSF findings do not preclude the disease. VGKC-Ab should, therefore, be determined whenever LE is clinically suspected, irrespective of the presence or absence of inflammatory CSF changes.     

A case of anti-NMDAR (N-methyl-D-aspartate receptor) encephalitis: a rehabilitation perspective

Anti-NMDAR (N-Methyl-D-Aspartate Receptor) Encephalitis is a rare occurring autoimmune disease that is mediated by antibodies against the NR1 subunit of the NMDA receptor. While this condition has a known predilection for young females with ovarian tumors, heightened awareness has led to increasing recognition of this condition in other population groups as well. Afflicted patients typically evolve through a multi-staged course of neurological, behavioral, cognitive and physical deficits. The diverse nature of this condition often necessitates a multi-disciplinary team for management. As the recovery of patients with anti-NMDAR encephalitis is often protracted, the role of the rehabilitation is important particularly beyond its acute stages. We describe a case of anti-NMDAR encephalitis in a 17-year-old girl who presented to our rehabilitation centre for management in the gradual recovery phase of her condition. This case illustrates the multiple challenges faced in the rehabilitation of such a patient.     

抗NMDA受体脑炎45例特点和临床转归分析

目的探讨本组抗NMDA受体脑炎患者的临床特点。方法收集北京丰台右安门医院和北京宣武医院神经内科2012年10月至2015年4月收治的45例抗NMDA受体脑炎患者的临床资料,分析病例特点,随访病情转归。结果本组的45例患者年龄为14~61岁,平均年龄32.2±13.24岁;男性27例,其中3例(11%)合并肿瘤。女性18例,其中5例(28%)合并卵巢畸胎瘤。23例(51%)出现前驱症状。本组45例临床症状表现为精神症状(91%)、癫痫发作(76%)、不自主运动(42%)、中枢性低通气(24%)、意识水平下降(47%)及自主神经功能障碍(40%)。脑脊液(CSF)常规、生化检查阳性率为89%,所有患者CSF抗NMDA受体抗体阳性。脑电图(EEG)多表现为双额、颞、中央导联为主的轻度(21%)至中度(59%)慢波。53%患者头颅CT平扫或MRI检查有异常表现,多见于额颞叶T2-Flair异常信号。所有患者均给予激素和丙种球蛋白治疗,6例患者接受环磷酰胺或吗替麦考酚治疗。除1例失访,44例患者预后良好(MRS评分0-2分)者占86%。结论抗NMDAR脑炎发病男性并不少见,肿瘤合并率低。以精神行为异常、癫痫发作、CSF抗NMDA受体抗体阳性为其主要临床特点。绝大部分患者EEG异常,并与病情严重程度相关。79%患者一线免疫治疗效果良好。8例合并肿瘤患者病情严重且预后不良,畸胎瘤摘除术不能完全预防该病发生,但能减轻病情严重程度。     

抗N-甲基-D-天冬氨酸受体脑炎的抗体检测及临床意义

目的探讨抗N-甲基-D-天冬氨酸受体(NMDAR)脑炎的抗体检测意义及临床特征。方法选取本院收治的脑炎病人35例及对照组30例,分析临床资料,采用转染细胞间接免疫荧光法检测两组患者其血清及脑脊液抗NMDAR机体结果抗NMDAR抗体检测仅1例边缘叶脑炎患者结果阳性,该患者腑脊液细胞数增多、蛋白轻度升高、脑电图见双侧慢波、其余检查无异常。精神症状及意识水平障碍明显,免疫治疗有效。结论抗NMDAR脑炎发病率低,临床表现复杂多样,怀疑该病时需行抗NMDAR抗体检测。     

Cerebrospinal fluid oligoclonal bands and progression of disability in multiple sclerosis

Antibody-mediated inflammation is believed to contribute to tissue injury in multiple sclerosis (MS). The majority of patients with MS have oligoclonal bands (OCB), corresponding to antibodies against a variety of antigens, in their cerebrospinal fluid (CSF). The relation of CSF OCB and disease progression in MS is uncertain. To investigate whether there is a relation between CSF OCB and a more aggressive disease course of MS, 143 patients with definite MS according to the Poser diagnostic criteria and CSF analysis at time of diagnosis were followed over a period of 5 years. There were no differences in presence or number of CSF OCB between patients with significant worsening of disability and stable patients. There were no differences in presence or number of CSF OCB between patients with stable relapsing-remitting MS and patients developing secondary progression during follow-up. The presence or number of CSF OCB does not seem to influence early disease progression in MS.     

Gray matter atrophy and corresponding impairments in connectivity in patients with anti-N-methyl-D-aspartate receptor encephalitis

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a severe autoimmune disease that is commonly accompanied by cognitive impairment and various neurological and psychiatric symptoms, advanced image analyses help explore the pathogenesis of this disease. Therefore, this study aimed to explore specific structural and functional alterations and their relationship with the clinical symptoms of anti-NMDAR encephalitis. In this study, twenty-two patients with anti-NMDAR encephalitis after the acute stage and 29 controls received cognitive assessments and magnetic resonance imaging. Grey matter atrophy was measured using voxel-based morphometry, and functional alterations in abnormal regions were subsequently investigated using resting state functional connectivity (RSFC). Finally, correlation analyses were performed to explore the associations between imaging alterations and cognitive assessments. The patients demonstrated significant gray matter atrophy in the bilateral triangle part of the inferior frontal gyrus (triIFG.L and triIFG.R) and right precuneus, decreased RSFC between triIFG.L and bilateral Heschl gyrus (HES), decreased RSFC between triIFG.R and HES.R, decreased RSFC between right precuneus and left cerebellum, and increased RSFC between triIFG.R and left superior frontal gyrus. Further correlation analyses showed that the gray matter volume in triIFG.R and decreased RSFC between triIFG.L and HES.R were associated with decreased memory scores, whereas decreased RSFC between triIFG.R and HES.R was marginally correlated with the disease course in patients. In conclusion, this study suggests that cognitive impairments in patients with anti-NMDAR encephalitis may be mainly associated with gray matter atrophy and abnormal RSFC in the triIFG. These findings provide new insights into anti-NMDAR encephalitis pathogenesis and help explore potential treatments.

     

Serial and prolonged EEG monitoring in anti-N-Methyl-d-Aspartate receptor encephalitis

ObjectiveTo describe serial electroencephalographic (EEG) findings of three patients with anti-NMDAR encephalitis.MethodsThree women (age 15–34 years) with confirmed anti-NMDAR encephalitis underwent serial EEG recordings. Continuous EEG for 72 h was performed in one case and 3-day video-EEG monitoring was obtained in two cases.ResultsGeneralized rhythmic delta activity (GRDA) was found in all patients. GRDA persisted for hours, but was not continuous on a 24-h EEG recording, disclosed no frequency, voltage or field evolution, and was not seen on the first EEG of two patients. Extreme delta brush was noted in two patients who presented more severe disease. One patient presented seizures, which were electrographically and clinically different from the GRDA pattern and from dyskinetic movements.ConclusionsSerial or continuous EEG may be necessary to detect GRDA in anti-NMDAR patients. To avoid unnecessary treatment, this pattern should not be interpreted as indicative of ictal activity, unless there is evidence of its ictal nature.SignificanceOur findings may contribute to the diagnosis of anti-NMDAR encephalitis in cases with characteristic clinical picture.     

Altered perception might be a symptom of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis

ABSTRACT

Most patients with N-methyl-D-aspartate receptor (NMDAR) encephalitis initially present with psychiatric symptoms. Although a delayed diagnosis may lead to a poor outcome, psychiatric symptoms that could differentiate anti-NMDAR encephalitis from other psychoses have not been fully investigated. We evaluated two patients with anti-NMDAR encephalitis who were observed by psychiatrists from onset throughout the course of disease. Both patients exhibited disorientation, memory deficits, perceptual disturbances, hallucinations, and mood liability. Among those, altered perceptions were most prominent - in particular, altered time perceptions without disorganization syndrome. The information obtained for these patients may help clinicians differentiate anti-NMDAR encephalitis from other psychoses, e.g., schizophrenia.     

重症抗N-甲基-D-天冬氨酸受体脑炎的临床特点及预后分析

目的探讨重症抗N-甲基-D-天冬氨酸受体(NMDAR)脑炎的临床特点及预后。方法回顾性分析9例重症抗NMDAR脑炎患者的临床资料。结果 9例患者(女7例,男2例)均入住ICU治疗;平均发病年龄27.7岁;平均病程22.4 d,ICU平均住院时间50.9 d。主要临床表现有发热(7例)、精神行为异常(9例)、癫痫发作(9例)、意识障碍(8例)、运动功能异常(7例)、自主神经功能障碍(9例)及低通气(6例)。3例合并畸胎瘤。所有患者CSF抗NMDAR抗体均阳性,6例血清抗NMDAR抗体阳性,7例CSF-Ig A升高。3例患者头颅MRI示颞叶或海马异常信号。5例患者EEG示异常慢波。9例患者接受糖皮质激素、丙种球蛋白或血浆置换等免疫调节治疗。5例患者完全恢复,4例患者症状改善伴残留症状。结论重症抗NMDAR脑炎常表现为进展迅速的精神行为改变、癫痫等症状,还有意识障碍、运动障碍、自主神经功能障碍,合并肿瘤并不多见。多数重症抗NMDAR脑炎患者积极免疫治疗预后较好。     

Hyperammonemia in a case of herpes simplex and anti-N-methyl-d-aspartate receptor encephalitis

Herpes simplex encephalitis (HSE) is a widely accepted risk factor for anti N-methyl-d-aspartate receptor (NMDAR) encephalitis. Association of inherited metabolic disease has never been reported in a patient with HSE and anti-NMDAR encephalitis. Herein, we report a case of pediatric HSE complicated by development of anti-NMDAR encephalitis; this patient showed subsequent recurrent, unexplained episodes of encephalopathy associated with hyperammonemia. The patient was diagnosed with lysinuric protein intolerance (LPI), a rare inborn metabolic disorder. Although it would be difficult to make conclusions regarding the casual link of HSE and anti-NMDAR encephalitis with LPI from a single case, there have been many reports that autoimmune diseases and immunologic abnormalities are frequently associated with LPI. Thus, we speculate that LPI may contribute to the development of anti-NMDAR encephalitis following HSE.     

Real-world experience of assessing antibodies against the N-methyl-D-aspartate receptor (NMDAR-IgG) in psychiatric patients. A retrospective single-centre study

ObjectiveTo evaluate the frequency of anti-NMDAR encephalitis in a secondary mental health service and investigate the challenges of its diagnosis in routine clinical practice.MethodsPatients whose electronic health records registered an indication for NMDAR-IgG assessment were selected and seropositive patients were reviewed.ResultsIn 1661 patients assessed for NMDAR-IgG over 12 years, the positivity rate was 3.79% (95% confidence interval [CI]: 2.87–4.70%). The working diagnosis at assessment was new onset psychosis in 38.7% and a chronic psychotic syndrome in 34.0%. Among seropositive patients, 30 (47.6%, 95%CI: 35.8–59.7%) had a final alternative diagnosis different from encephalitis after a median period of 49 months from onset. Patients with a final diagnosis of encephalitis were more frequently female (27/35 vs 13/30, p = 0.011) than other seropositive patients and had more frequently an acute (34/35 vs 11/30, p < 0.001), fluctuating (21/23 vs 4/27, p < 0.001) or agitated (32/32 vs 10/26, p < 0.001) presentation. Nine encephalitic patients received specialized follow-up for chronic neuropsychiatric problems including learning disabilities, organic personality disorder, anxiety, fatigue, obsessive–compulsive and autism-like disorder.ConclusionsIn a psychiatric setting, NMDAR-IgG seropositivity rates were low with a positive predictive value for encephalitis around 50% when screened patients had chronic presentations and absence of other diagnostic criteria for encephalitis or psychosis of autoimmune origin. Chronic neuropsychiatric problems in anti-NMDAR encephalitis are not uncommon, so better diagnostic and treatment strategies are still needed.