A Unique Shape of Brainstem Lesion that Caused Orthostatic Hypotension in Anti-NMDAR Encephalitis

After experiencing upper respiratory-tract symptoms, a 41-year-old woman developed encephalitis with consciousness disturbance and respiratory failure. She had external ophthalmoplegia and facial diplegia. Magnetic resonance imaging revealed a brainstem lesion with spared longitudinal pontine bundles. Abnormal findings of the brainstem auditory-evoked potentials and blink reflex supported brainstem damage. The patient was positive for anti-N-methyl-D-aspartate receptor (NMDAR) antibodies. Repeated immunological treatments improved her symptoms, but severe orthostatic hypotension emerged. A head-up tilt test revealed no arginine vasopressin response to hypotension. The atypical symptoms of this case highlighted that the brainstem is one of the pivotal regions in anti-NMDAR encephalitis.

Clinical characteristics of autoimmune disorders in the central nervous system associated with myasthenia gravis

Myasthenia gravis (MG) is occasionally associated with autoimmune diseases in the central nervous system (CNS), such as neuromyelitis optica spectrum disorder (NMOSD), multiple sclerosis (MS), Morvan syndrome, and anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Here, we report five original cases associated with autoimmune disorders in the CNS among 42 patients with MG in a single tertiary hospital in Japan (11.9%). In four of these five cases, the second disease developed when the preceding disease was unstable. Accurate diagnosis of the newly developing disease may be difficult in such cases, because some neurological symptoms can be seen in both disorders. This implies the great importance of recognizing the possible co-occurrence of MG and disorders in the CNS. In addition, a comprehensive review of the literature revealed distinct clinical characteristics depending on the associated disease in the CNS, including thymic pathology and temporal relationship between MG and associated CNS disorders. Notably, NMOSD usually develops after the onset of MG and thymectomy, in clear contrast to MS. Thymoma is highly prevalent among patients with Morvan syndrome, in contract to cases with NMOSD and MS. The analysis of clinical characteristics, representing the first such investigation to the best of our knowledge, suggests different pathogeneses of these autoimmune diseases in the CNS, and provides significant implications for clinical practice.

Association of Anti N-methyl-D-aspartate (NMDA) Receptor Encephalitis with Chediak-Higashi Syndrome

BACKGROUND

Neurological manifestations of Chediak-Higashi syndrome mainly include peripheral neuropathy, ataxia, tremors, cranial nerve palsies, intellectual decline and seizures.

CASE CHARACTERISTICS

A 2 years 10 month old girl with silvery hair syndrome presented with sub-acute onset behavioral issues, ataxia and multiple type abnormal movements. Cerebrospinal fluid examination was positive for Anti NMDA receptor antibodies. Hair shaft examination and peripheral blood film findings were suggestive of Chediak Higashi syndrome.

MESSAGE

Anti NMDA receptor encephalitis may be associated with Chediak Higashi Syndrome.

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.

NMDAR encephalitis presenting as akinesia in a patient with Parkinson disease

We describe the case of a woman with Parkinson disease who developed an N-methyl-d-aspartate receptor antibody-mediated encephalitis. As a novelty, the encephalitis presentation mimicked a worsening of the pre-existing extrapyramidal syndrome, manifesting mainly as severe bradykinesia and, eventually, akinesia. Brain MRI was normal, whereas cerebrospinal fluid (CSF) analysis disclosed unique-to-CSF oligoclonal bands. Prompt identification and timely immunotherapy led to a complete recovery.

Clinical Profile and Neuropsychiatric Outcome in Children with Anti-NMDAR Encephalitis

Six children with anti-NMDAR encephalitis were followed-up for 6 to 24 months. They presented with seizures, neuropsychiatric symptoms and movement disorder, particularly orofacial dyskinesia and choreoathetosis. Immunosuppressive therapy resulted in varying degrees of improvement; none relapsed. Expressive aphasia was the last symptom to regress.

A mouse model of seizures in anti-N-methyl-d-aspartate receptor encephalitis

OBJECTIVE

Seizures develop in 80% of patients with anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis, and these represent a major cause of morbidity and mortality. Anti-NMDAR antibodies have been linked to memory loss in encephalitis; however, their role in seizures has not been established. We determined whether anti-NMDAR antibodies from autoimmune encephalitis patients are pathogenic for seizures.

METHODS

We performed continuous intracerebroventricular infusion of cerebrospinal fluid (CSF) or purified immunoglobulin (IgG) from the CSF of patients with anti-NMDAR encephalitis or polyclonal rabbit anti-NMDAR IgG, in male C57BL/6 mice. Seizure status during a 2-week treatment was assessed with video-electroencephalography. We assessed memory, anxiety-related behavior, and motor function at the end of treatment and assessed the extent of neuronal damage and gliosis in the CA1 region of hippocampus. We also performed whole-cell patch recordings from the CA1 pyramidal neurons in hippocampal slices of mice with seizures.

RESULTS

Prolonged exposure to rabbit anti-NMDAR IgG, patient CSF, or human IgG purified from the CSF of patients with encephalitis induced seizures in 33 of 36 mice. The median number of seizures recorded in 2 weeks was 13, 39, and 35 per mouse in these groups, respectively. We observed only 18 brief nonconvulsive seizures in 11 of 29 control mice (median seizure count of 0) infused with vehicle (n = 4), normal CSF obtained from patients with noninflammatory central nervous system (CNS) conditions (n = 12), polyclonal rabbit IgG (n = 7), albumin (n = 3), and normal human IgG (n = 3). We did not observe memory deficits, anxiety-related behavior, or motor impairment measured at 2 weeks in animals treated with CSF from affected patients or rabbit IgG. Furthermore, there was no evidence of hippocampal cell loss or astrocyte proliferation in the same mice.

SIGNIFICANCE

Our findings indicate that autoantibodies can induce seizures in anti-NMDAR encephalitis and offer a model for testing novel therapies for refractory autoimmune seizures.

The psychopathology of NMDAR-antibody encephalitis in adults: a systematic review and phenotypic analysis of individual patient data

BACKGROUND

Early immunotherapy administration improves outcomes in patients with N-methyl-D-aspartate receptor (NMDAR)-antibody encephalitis. As most patients with NMDAR-antibody encephalitis present to psychiatrists, the psychopathology of NMDAR-antibody encephalitis needs to be clearly defined to encourage accurate clinical identification and prompt treatment.

METHODS

For this systematic review, we searched PubMed for all studies published in English between Jan 1, 2005, and Oct 7, 2017, to identify individually reported adult patients (≥18 years) who satisfied consensus criteria for definite NMDAR-antibody encephalitis. After generating a list of 50 fine-grained, lower-level features, we extracted psychopathological data in addition to demographic and aetiological data. The lower-level features were later ordered within higher-level categories. As a means of quality control, we filtered the data according to proxy markers of psychiatric involvement in their description. Subsequently, we compared lower-level features from individual patient data with operationalised psychiatric syndromes using a constrained combination approach and principal component analysis, and did a network analysis to explore the inter-relationships between multiple lower-level features. The review protocol was prospectively registered with PROSPERO, number CRD42017068981.

FINDINGS

Of 1096 records identified in PubMed, 333 satisfied inclusion criteria and described 1100 patients in total with NMDAR-antibody encephalitis. The psychopathology of 505 (46%) patients with reported psychiatric symptoms was described in more detailed terms than only psychiatric or behavioural. 464 (91%) of the 505 patients were from papers in which patient data were reported individually. The remainder of the analyses focused exclusively on these 464 patients. Median age was 27 years (IQR 22-34), 368 (79%) of 464 patients were female and in 147 (32%), NMDAR-antibody encephalitis was associated with ovarian teratoma. The five higher-level categories into which the 464 patients most frequently grouped were behaviour (316 [68%]), psychosis (310 [67%]), mood (219 [47%]), catatonia (137 [30%]), and sleep disturbance (97 [21%]). The overall pattern of lower-level features was statistically stable across subgroups classified by age, sex, pregnancy association, presence of ovarian teratoma, prior herpes simplex virus encephalitis, and isolated psychiatric presentations (two-way ANOVA p=0·6-0·9). Constrained combination and principal component analyses found that mixtures of mood and psychosis syndromes fit each patient better than any single diagnosis alone, particularly for the patients in the psychiatric-described subgroup (mean ΔAkaike information criterion -0·04 in non-psychiatric-described subgroup vs 0·61 in psychiatric-described subgroup). The overlapping nature of the higher-level features was also enriched upon analysis of the psychiatric-described data (221 [67%] of 329 overlaps in non-psychiatric-described subgroup vs 96 [81%] of 118 overlaps in psychiatric-described subgroup, p=0·0052). Network analysis confirmed that the features were closely related and consistent between individual patients; the psychiatric-described subgroup had a markedly high and narrow range of closeness centralities (92% above 0·93 in psychiatric-described subgroup vs 51% above 0·93 in the non-psychiatric group).

INTERPRETATION

The distinctive aspect of NMDAR-antibody encephalitis psychopathology is complexity; core aspects of mood and psychotic disorders consistently coexist within individual patients. Alongside the predominant young female demographic, these psychopathological features could help psychiatrists identify patients who would benefit from cerebrospinal fluid testing and immunotherapies. Well-controlled prospective studies with bespoke inventories are needed to advance this clinically grounded approach.

FUNDING

Wellcome Trust, NIHR Oxford Biomedical Research Centre, NIHR Oxford Health Biomedical Research Centre, British Medical Association Foundation for Medical Research.

[Anti-NMDAR encephalitis associated with relapsing optic neuritis: a case report and differential diagnosis]

Autoimmune encephalitis with antibodies to NMDA receptors, or anti-NMDAR encephalitis, is the most common form of autoimmune encephalitis. The disease is curable, however, the lack of timely therapy can lead to the disability of patients or to the death. Difficulties in the diagnosis of anti-NMDAR encephalitis are caused by the heterogeneity of its manifestations, a possible overlapping with other autoimmune diseases and insufficient awareness about this form of encephalitis. This article presents the literature review and describes the case of anti-NMDAR encephalitis associated with recurrent optic neuritis, which might be an atypical manifestation for this disease. Optic neuritis could not be explained by overlapping with multiple sclerosis or neuromyelitis optica spectrum disorders.

[Anti-NMDA receptor encephalitis. Early diagnosis and treatment in patients with acute-subacute psychotic symptoms]

INTRODUCTION

Encephalitis due to anti-NMDA receptor antibodies is an acute and severe condition, which, if identified and treated quickly, can entail recovery without any sequelae. It is more prevalent in young females and is often associated with an underlying tumour. The initial symptoms are usually of a psychiatric nature, and in a matter of days or weeks take on a characteristic neurological profile.

CASE REPORTS

We report the cases of three women, 17, 23 and 35 years of age, who were admitted to Psychiatry with acute psychotic clinical features. The poor response to antipsychotics, the fluctuations in the level of consciousness, dysautonomia and epileptic seizures were the symptoms that led to the clinical suspicion. The cerebrospinal fluid revealed slight pleocytosis and gave positive for anti-NMDA receptor antibodies in all cases. Only one patient displayed alterations in the magnetic resonance brain scan, and in two cases there was an extreme delta brush electroencephalographic pattern. All three women were diagnosed with an ovarian teratoma which was resectioned within a month. Two of the patients recovered without any sequelae, and the third presents cognitive sequelae six months after being discharged.

CONCLUSIONS

The cases described began with an acute psychotic clinical picture. The atypical psychiatric progression and the neurological symptoms indicated the possible presence of encephalitis. Recognition of the disease and coordination among the different services is essential for early diagnosis and treatment. The systematic analysis of cerebrospinal fluid in patients with a first acute-subacute psychotic episode would help to reach a diagnosis sooner. In young women, a search must always be carried out for an ovarian teratoma or other associated tumour.

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.

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.

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.

Analysis and discussion of the rare complication of autoimmune encephalitis: Two case reports

RATIONALE

Autoimmune encephalitis related to many antibodies against neuronal cell surface or synaptic proteins, it is increasingly recognized as the cause of a variety of neuropsychiatric syndromes.

PATIENT CONCERNS

The two pediatric cases were about autoimmune encephalitis with rare complication. One patient was a 11-year-old girl and was diagnosed with Voltage-Gated Potassium Channel complex (VGKC) antibody-mediated encephalitis with rhabdomyolysis; the other was also a 11-year-old girl and was diagnosed with anti- N-methyl-D-aspartate receptor (NMDAR) encephalitis.

DIAGNOSES

Both patients were diagnosed as autoimmune encephalitis with rare complication.

INTERVENTIONS

Intravenous methylprednisolone, oral prednisone and intravenous immunoglobulin was administered to both patients.

OUTCOMES

One patient was discharged after a half month's hospitalization; the other was finally with intestinal function failure, gradually developed multiple organ failure, and eventually died.

LESSONS

The pathogenic mechanism of autoimmune encephalitis associated with autoimmune disease is not fully understood, but may be related to a common immune pathological mechanism with variance in susceptibility caused by genetic or environmental factors.

Late-onset anti-N-methyl-d-aspartate receptor encephalitis in China

PURPOSE

This study aimed to summarize the clinical characteristics and outcome of late-onset anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis in China.

METHOD

All cases of people with a definitive diagnosis of anti-NMDAR encephalitis in West China Hospital between June 2012 and April 2017 were retrospectively reviewed. The demographics, clinical characteristics, and outcome of those patients (age≥45years old) were summarized. Comparisons were conducted between older (≥45years old) and younger (18-44years old) adults.

RESULT

Eighteen (12%) of 151 people were ≥45years old, 9 of whom (50%) were female. Psychiatric symptoms were the most common clinical manifestations of older adults and presented in all individuals. At the last follow-up, 14 (78%) of them had a good outcome (modified Rankin Scale: 0-2) and one (6%) died. Compared with 121 younger adults, older adults had a higher proportion of presenting memory deficit as the initial symptom (17% vs. 2%, p=0.023), longer interval from onset to admission (30 vs. 13days, p=0.013), and longer interval from onset to diagnosis (42.5 vs. 24days, p=0.045). No older adults' condition was accompanied with teratoma compared with 75% of younger adults with tumor (p=0.032). And older adults had a tendency to have a lower rate of positive NMDAR antibody (Ab) in serum (28% vs. 52%, p=0.053).

CONCLUSION

Delayed admission and diagnosis are more common in older adults than in younger adults. A comprehensive consideration of all symptoms and early screening of NMDAR Ab, especially in cerebrospinal fluid, is necessary and beneficial to differential diagnosis.

[Guideline for fecal bacteriotherapy to treat recurrent Clostridium difficile colitis]

We present a case of a 17-year-old female with anti-NMDAR encephalitis probably associated with vaccination against yellow fever. Her symptoms occurred 27 days after vaccination against yellow fever. Anti-NMDAR encephalitis manifested as acute psychosis, memory loss and catatonia following fever with complex partial epileptic seizures. Interictal electroencephalogram showed slow-wave delta background activity with "delta brushes". The diagnosis was confirmed by NMDAR antibody positivity in serum and cerebrospinal fluid. Since ovarian teratoma, as the most common cause of anti-NMDAR encephalitis, did not develop within five years from its onset, the association with vaccination against yellow fever seems to be highly probable.

Long-term neuropsychological outcome following pediatric anti-NMDAR encephalitis

OBJECTIVE

To provide detailed long-term outcome data of children and adolescents following pediatric anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis, to identify neuropsychological impairments, and to evaluate the influence of these factors on quality of life (QoL).

METHODS

All Dutch children diagnosed with anti-NMDAR encephalitis were identified. Patients currently aged 4 years or older were included in the follow-up study, consisting of a visit to our clinic for a detailed interview and a standardized neuropsychological assessment. The following domains were included: attention, memory, language, executive functioning, QoL, and fatigue. Primary outcome measures were z scores on sustained attention, long-term verbal memory, QoL, fatigue, and working memory.

RESULTS

Twenty-eight patients were included. Median Pediatric Cerebral Performance Category at last visit was 1 (interquartile range 1-2, range 1-4), and 64% (18/28) of patients returned consistently to their previous school level. Twenty-two patients were included in the cross-sectional part of the long-term follow-up study. Median follow-up time was 31 months (interquartile range 15-49, range 5-91). There were problems with sustained attention (z = -2.10, 95% confidence interval = -2.71 to -1.46, p < 0.0001) and fatigue (z = -0.96, 95% confidence interval = -1.64 to -0.28, p = 0.008). Cognitive deficits were not correlated with QoL, while fatigue was strongly correlated with QoL (r = 0.82, p < 0.0001).

CONCLUSIONS

Although follow-up is often reported as "good" following pediatric anti-NMDAR encephalitis, many patients have cognitive problems and fatigue, even up until adolescence, resulting in academic achievement problems and lower QoL. For physicians, it is essential to be aware of these problems, to provide valuable advice to patients and caregivers in the acute and follow-up phase, and to consider early neuropsychological counseling.

Unusual case of anti-N-methyl-D-aspartic acid-receptor (NMDA-R) encephalitis and autoimmune polyglandular syndrome (APS)

Anti-N-methyl-D-aspartic acid-receptor (NMDA-R) encephalitis is a novel disease discovered within the past 10 years. It is an autoimmune disease (AD) that has been associated with other ADs, such as Graves' disease. However, association with autoimmune polyglandular syndromes (APS) has not been previously described. A 58-year-old woman presented with altered mental status and an 8-month history of weight loss, apathy and somnolence. Laboratory evaluation confirmed Graves' disease with thyrotoxicosis and type 1 diabetes mellitus. Despite treatment, she continued to have a fluctuating mental status. Further diagnostic evaluation included an abdominal MRI that showed a cystic lobular left adnexal mass. Serum anti-NMDA-R antibodies were positive, raising concern for NMDA-R encephalitis. Bilateral salpingo-oophorectomy was performed, with pathology consistent with cystadenofibroma. She had a favourable recovery with marked clinical improvement. Anti-NMDA-R antibodies were negative 2 months following surgery. The concomitant occurrence of APS and anti-NMDA-R encephalitis suggests a shared mechanism of autoimmune pathophysiology.

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.

An unusual case of refractory status epilepticus in a young lady: anti-NMDA receptor encephalitis

We describe a case of a young lady with anti-NMDA (N-methyl-D-aspartate) receptor encephalitis, who initially presented with status epilepticus. Her seizures and orofacial dyskinesia were refractory to four anticonvulsants. She received intravenous immunoglobulin and a left ovarian tumour (an associated feature) was resected. However, her outcome was poor because of delayed treatment, autonomic dysfunction and complications of prolonged hospitalisation. This case highlights the importance of an early recognition of this rare but increasingly recognised disease.

[Analysis of prodromal phase and prodromal events in anti-N-methyl-D-aspartate receptor encephalitis]

Objective: To analyze prodromal phase and prodromal events of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Methods: Clinical data of 179 patients hospitalized and diagnosed during 2010-2016 including adults and children in Peking Union Medical College Hospital and Beijing Children's Hospital were collected.Patients with prodromal phase or prodromal events were selected.A retrospective analysis of clinical characteristics including prodromal phase or prodromal events, course of disease, brain imaging, laboratory results and therapeutic effect was performed. Results: Prodromal phase was presented in 31.8% (57/179) of patients.Most common symptoms included fever (73.7%) and headache (68.4%). Prodromal phase was prolonged in 6 patients, the longest being 64 days.Among those 6 patients (10.5%), headache and fever were the only symptoms throughout disease courses in 3 cases.Prodromal events were reported in 6.1% (11/179) of patients, including 5 patients after HSV1 encephalitis, 1 after Japanese encephalitis, and 2 after resection of melanocytic nevi. Conclusions: Anti-NMDAR encephalitis can be preceded with prolonged prodromal phase.In some patients prodromal symptoms are the only clinical presentation.Clinical features of those atypical cases suggest that infection may be the precipitating factor.Viral encephalitis including HSV1 encephalitis and Japanese encephalitis may be prodromal events in some cases.