anti-NMDAR Autoimmune Encephalitis Research Articles

Seizures in a healthy 20-year-old woman.

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is the most common type of autoimmune encephalitis. The initial presentation can vary from subtle mental status changes to more severe symptoms such as seizures, coma, or death. This case report outlines the interdisciplinary and collaborative approach to diagnosing and treating a patient with anti-NMDAR autoimmune encephalitis.

Electroencephalographic patterns and their association with functional prognosis in anti-NMDA autoimmune encephalitis

Autoimmune encephalitis is a rare disease with low incidence and prevalence but carries high rates of disability and potential fatality. To determine whether the presence of abnormal electroencephalographic patterns in patients with anti-NMDAR autoimmune encephalitis affects functional prognosis at 3 months. A retrospective, observational, analytical, longitudinal-cross-sectional study was conducted with a retrospective cohort. Out of a total of 44 patients with anti-NMDAR autoimmune encephalitis, concerning electroencephalographic findings, 19 patients had a normal EEG result (43.2%), 18 had cortical dysfunction (40.9%), 7 had epileptiform reports (15.9%), and only 1 had a Delta Brush report (2.3%). The functional outcome of patients at 3 months measured by the modified Rankin Scale (mRS) was as follows: 3 patients without disability (6.8%), 6 patients with mild disability (13.6%), 17 patients with mild to moderate disability (38.6%), 9 patients with moderate to severe disability (20.5%), 1 patient bedridden (2.3%), and 2 deceased (5.6%). In our study, no association was found between an abnormal electroencephalographic pattern and a worse functional prognosis at 3 months in patients with autoimmune encephalitis. Although the electroencephalogram analyzed is the initial one, it would be necessary to assess later whether the persistence of abnormalities in the electroencephalogram is related to a greater number of sequelae and disabilities.

Impact of Clinical Progression on Brain Volume Changes in Patients with Anti-NMDAR Autoimmune Encephalitis

Impact of Clinical Progression on Brain Volume Changes in Patients with Anti-NMDAR Autoimmune Encephalitis

Structural and functional mechanisms of anti-NMDAR autoimmune encephalitis.

Autoantibodies against neuronal membrane proteins can manifest in autoimmune encephalitis, inducing seizures, cognitive dysfunction and psychosis. Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is the most dominant autoimmune encephalitis; however, insights into how autoantibodies recognize and alter receptor functions remain limited. Here we determined structures of human and rat NMDARs bound to three distinct patient-derived antibodies using single-particle electron cryo-microscopy. These antibodies bind different regions within the amino-terminal domain of the GluN1 subunit. Through electrophysiology, we show that all three autoantibodies acutely and directly reduced NMDAR channel functions in primary neurons. Antibodies show different stoichiometry of binding and antibody-receptor complex formation, which in one antibody, 003-102, also results in reduced synaptic localization of NMDARs. These studies demonstrate mechanisms of diverse epitope recognition and direct channel regulation of anti-NMDAR autoantibodies underlying autoimmune encephalitis.

Electroencephalographic outcomes and predictors of epilepsy in autoimmune encephalitis

BackgroundAn abnormal EEG is pivotal in diagnosis, exclusion of mimickers and prognosticating epilepsy in Autoimmune Encephalitis (AE). However, little is known about the short and long term electroencephalographic outcomes and predictors of epilepsy in AE. This study aims to describe the seizure characteristics and electrophysiological markers of various AE subtypes and assess the clinical and electrophysiological predictors of autoimmune epilepsy. MethodsClinical features and EEGs in 74 patients (acute phase=39 and post-acute phase defined after a minimum eight weeks after acute phase=35) of AE fulfilling the proposed criteria were reviewed in their respective acute phases and at six months follow-up. ResultsThe mean age of presentation (N = 74, 45 females) was 21.8 (21.8 ± 17.0) years. 38 (51 %) patients were <18 years. Seizures were present in 55 (74 %) patients with poor response to ASMs (p = 0.039). 39 (52.7 %) EEGs were abnormal in acute phase. Anti-NMDAR AE had most frequently abnormal EEG (63.4 %). Poor background reactivity and theta range slowing were most common abnormalities. FIRDA, EDB and delta range slowing were seen in seropositive AE (P = 0.003). Mutism, psychiatric features and incontinence correlated with abnormal EEG (p = 0.013, p = 0.028 and p = 0.025). Background slowing and epileptiform discharges predicted worse cognitive scores at follow-up (p = 0.012). Eight (11.9 %) patients developed epilepsy. Status epilepticus at presentation (p = 0.009), seronegative status (p = 0.0020), delayed initiation of immunotherapy (p = 0.012), abnormal MRI (p = 0.003) and abnormal EEG (p = 0.004) at onset indicate development of autoimmune epilepsy ConclusionsFIRDA, EDB and delta range slowing with refractory seizures suggest AE. Epileptiform abnormalities, status epilepticus and seronegativity predict autoimmune epilepsy.

Kappa index in the diagnostic work-up of autoimmune encephalitis

BackgroundThe presence of inflammatory changes in the cerebrospinal fluid (CSF), including immunoglobulin intrathecal synthesis (IS), can support the diagnosis of autoimmune encephalitis (AE) and allow prompt treatment. The main aim of our study was to calculate the Kappa index as a marker of IS, in patients with AE. MethodsCharts of patients undergoing a diagnostic work-up for suspected AE between 2009 and 2023 were reviewed and the Graus criteria applied. CSF and serum kappa free light chains were determined using the Freelite assay (The Binding Site Group) and the turbidimetric Optilite analyzer. ResultsWe identified 34 patients with “definite” AE (9 anti-NMDAR AE and 25 limbic AE) and nine patients with “possible” AE. Five patients (15%) with definite AE had pleocytosis and twelve (34%) showed CSF-restricted oligoclonal bands (OCB) at isoelectric focusing. The Kappa index was >6 in 29.4% and > 3 in 50% of the definite AE patients. It was elevated (>3) in 36.4% of patients with definite AE who resulted negative to OCB testing and was the only altered parameter suggestive of an ongoing inflammatory process in the CNS in three definite AE patients with otherwise normal CSF findings (i.e. normal cell count and protein levels, no OCBs). In the possible AE group, one patient had a Kappa index >3 in the absence of OCB. ConclusionsThe Kappa index could be useful, as a more sensitive marker of IS and as a supportive marker of neuroinflammation, in the diagnostic work-up of suspected AE.

Contribution of cerebrospinal fluid antibody titers and sex to acute cerebral blood flow in patients with anti-NMDAR autoimmune encephalitis.

The objective of this study was to elucidate the contribution of cerebrospinal fluid (CSF) antibody titers (AT) and sex to acute cerebral blood flow (CBF) in patients diagnosed with anti-N-methyl-d-aspartate receptor autoimmune encephalitis (NMDAR AE). Forty-five patients diagnosed with NMDAR AE were recruited from December 2016 to January 2023. The acute CBF in patients with NMDAR AE at the early stage of the disease was analyzed using arterial spin labeling. The groups were compared based on CSF AT and sex. The connectivity of the CBF in the region of interest was also compared between groups. The patients with different CSF AT exhibited varied brain regions with CBF abnormalities compared to the healthy subjects (p = 0.001, cluster-level FWE corrected). High antibody titers (HAT) in CSF contributed to more brain regions with CBF alterations in female patients than in female patients with low antibody titers (LAT) in CSF (p = 0.001, cluster-level FWE corrected). Female patients with HAT in CSF displayed more decreased CBF in the left post cingulum gyrus, left precuneus, left calcarine, and left middle cingulum gyrus than the male patients with the same AT in CSF (p = 0.001, cluster-level FWE corrected). All patients with NMDAR AE showed increased CBF in the left putamen (Putamen_L) and left amygdala (Amygdala_L) and decreased CBF in the right precuneus (Precuneus_R), which suggests that these are diagnostic CBF markers for NMDAR AE. CSF AT and sex contributed to CBF abnormalities in the patients diagnosed with NMDAR AE. Altered CBF might potentially serve as the diagnostic marker for NMDAR AE.

Infrequent patterns in cerebrospinal fluid isofocusing test: Clinical significance and contribution of IgG index and Reiber diagram to their interpretation

Cerebrospinal fluid (CSF) isoelectrofocusing (IEF) is considered as the gold standard for detecting an intrathecal synthesis of IgG, which is a hallmark of multiple sclerosis (MS). This corresponds to the presence of CSF-restricted IgG oligoclonal bands (OCB) (typically type 2 pattern). Moreover, this technique can also detect a systemic immune reaction with passive transfer of IgG (type 3 and 4 patterns) for which the clinical relevance is less understood. The aim of our study was to determine the frequency and disease associations of IEF type 3 and 4 patterns and to investigate the potential usefulness of including quantitative data (IgG index and Reiber Diagram) in interpreting such IEF profiles.Among 544 patients who underwent CSF IEF (Hydragel CSF isofocusing kit, Sebia®, France) in our Laboratory during a six-year-period, those who presented type 3 or 4 patterns were selected. Clinical data and results of other immunological tests were analyzed for 27 patients followed in the Neurological Department.Frequencies of type 3 and type 4 patterns were relatively low (2.3 % and 3.4 % respectively). Among patients with type 3 pattern included in our study (n = 10), 5 were diagnosed with MS. For the 5 other patients, the diagnosis was a clinically isolated syndrome (CIS) (2 cases), a probable auto-immune encephalitis (2 cases) and a possible genetic neurodegenerative disease (1 case). MS patients had an IgG index >0.7 and fell into area 4 of Reiber diagram while non-MS patients had an IgG index <0.7 and fell into area 1, except the last case. Regarding type 4 pattern (n = 17), the diagnoses were as follows: MS (3), CIS (4), Neuromyelitis optica spectrum disorders with positive anti-AQP4 antibodies (3) and anti-NMDAR autoimmune encephalitis (1). The remaining cases had central nervous system impairment related to vascular, metabolic or tumoral etiologies (3) or peripheral nervous system impairment (3). In this group (type 4 pattern), IgG index was <0.7 in 15/17 cases. Interpretation using Reiber diagram showed an abnormal blood-brain barrier for 8/17 patients.Type 3 and 4 IEF patterns are infrequently observed in routine neurology practice. It is important for the diagnostic laboratory professional as well as for the neurologist to understand their clinical relevance. Our findings highlight the contribution of quantitative evaluation of CSF (IgG index, Reiber diagram) for the interpretation of such situations. Despite the small size of our study population, our results emphasize the importance of reporting the exact type of IEF pattern and not only the positivity or not of OCB.

Anti-NMDAR Autoimmune Encephalitis in a Paediatric Patient with a Rare Clinical Presentation with Isolated Symptoms of Psychosis

Anti-NMDAR Autoimmune Encephalitis in a Paediatric Patient with a Rare Clinical Presentation with Isolated Symptoms of Psychosis

Post-Abortum NMDA Encephalitis (P5-5.010)

<h3>Objective:</h3> To present a case series of two patients who developed NMDAR encephalitis after elective abortion. <h3>Background:</h3> Anti-NMDAR encephalitis has been associated with several preceding triggers, most commonly tumors and HSV encephalitis. Recognizing other triggers is important to elevate clinical suspicion when evaluating patients with acute encephalitis symptoms. Although cases have been reported of NMDA encephalitis during pregnancy, to our knowledge only one other case preceded by an abortive procedure was published. <h3>Design/Methods:</h3> N/A <h3>Results:</h3> Two patients, aged 20 and 27 years old, with no previous neurological history developed anti-NMDAR encephalitis after undergoing an elective abortion. Symptoms started 2 weeks after the procedure and was described as an acute psychosis. Diagnosis of anti-NMDAR encephalitis was confirmed with antibody titer testing in the CSF and serum. Both patients had positive Anti-NMDAR antibody titer in CSF; one patient also had positive antibody testing in the serum. Hospital stay of both patients was complicated by catatonia, with one patient requiring prolonged ICU stay due to severe dysautonomia. Patients were treated with a 5-day course of IVIG and made a full recovery. Cancer workup was done with transvaginal ultrasound, and CT chest, abdomen and pelvis on initial presentation and was negative at the time of presentation. In serial CT scans, one of the patients developed a thymoma six months after the onset and underwent surgical removal of the lesion with complete resolution of the symptoms. <h3>Conclusions:</h3> These cases suggests that anti-NMDAR autoimmune encephalitis may be correlated with recent abortion. Recognizing this possible relation might indicate that termination of pregnancy in these patients may not lead to improvement of the neurological condition. It is important to note that this association should not preclude investigations for underlying malignancy. Further population studies need to be performed to confirm abortion as a possible trigger and underlying pathophysiology of this neurological condition. <b>Disclosure:</b> Dr. Aleyadeh has nothing to disclose. Dr. Nascimento Andrade has nothing to disclose. Dr. Shaikh has nothing to disclose. Dr. Bose has nothing to disclose. Dr. Umeton has nothing to disclose.

Severity of Hospitalized Children with Anti-NMDAR Autoimmune Encephalitis.

Background: Information on the clinical characteristics and severity of autoimmune encephalitis with antibodies against the N-methyl-d-aspartate receptor (NMDAR) in children is attracting more and more attention in the field of pediatric research. Methods: In this retrospective cohort study, all cases (n = 67) were enrolled from a tertiary children's hospital, from 2017 to 2020. We compared severe cases that received intensive care unit (ICU) care with nonsevere cases that did not receive ICU care and used machine learning algorithm to predict the severity of children, as well as using immunologic and viral nucleic acid tests to identify possible pathogenic triggers. Results: Mean age of children was 8.29 (standard deviation 4.09) years, and 41 (61.19%) were girls. Eleven (16.42%) were admitted to the ICU, and 56 (83.58%) were admitted to neurology ward. Ten individual parameters were statistically significant differences between severe cases and nonsevere cases (P < .05), including headache, abnormal mental behavior or cognitive impairment, seizures, concomitant tumors, sputum/blood pathogens, blood globulin, blood urea nitrogen, blood immunoglobulin G, blood immunoglobulin M, and number of polynucleated cells in cerebrospinal fluid. Random forest regression model presented that the overall prediction power of severity reached 0.806, among which the number of polynucleated cells in cerebrospinal fluid contributed the most. Potential pathogenic causes exhibited that the proportion of mycoplasma was the highest, followed by Epstein-Barr virus. Conclusion: Our findings provided evidence for early identification of autoimmune encephalitis in children, especially in severe cases.

Brain MRI volumetric changes in the follow-up of patients with anti-NMDAr encephalitis

IntroductionAutoimmune anti-NMDAr encephalitis is an antibody-mediated disorder characterized by psychiatric symptoms followed by decreased consciousness, dysautonomia and seizures. The pathophysiology of the disease is related to the internalization of NR1 subtype NMDA receptors and the dysfunction of structures where they are abundant (frontotemporal and insular regions). Some reports suggest the existence of cerebral atrophy in the follow-up of these patients, with conflicting evidence regarding its presence and usefulness as a marker of prognosis. MethodsIn a longitudinal, observational study, all patients with the diagnosis of definite anti-NMDAr autoimmune encephalitis with initial and control MRI studies were included. Conventional MR Brain acquisition was performed using a 3-Tesla Skyra MRI System. Automated brain segmental analysis was performed using the Volbrain volumetry system. The differences between baseline MRI volumetric characteristics and volumetric measures at follow-up was assessed. Results25 patients were included (mean age 26.6, SD 9.6). 44% were females. The mean time between the studies was 24 (SD 21.4, 3–24) months. Significant volume loss was identified in the total brain volume (− 0.02%, p = 0.029), cerebellar volume (− 0.27%, p = 0.048) and brainstem volume (− 0.16%, p = 0.021). ConclusionsThis study supports previous observations regarding volume loss in several brain regions of patients with antiNMDAr encephalitis. Further analyses are required to understand the role of treatment and severe clinical forms, as well as the relationship between volume loss and functional outcome.

P62 Cyclophosphamide and maintenance mycophenolate mofetil for the treatment of anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis in a paediatric patient

BackgroundAnti-NMDAR encephalitis is one of the commonest known types of autoimmune encephalitis with an increasing recognition in the paediatric population.1 2 It is characterised by abnormal behavioural and cognitive symptoms, seizures and movement disorders where treatment failure or failure to treat can result in long term disabilities or mortality.1A 4-year-old patient with a background of autism was admitted to the paediatric intensive care unit (PICU) due to encephalitis with convulsive status epilepticus where he remained intubated for 22 days and was later diagnosed with anti-NMDAR encephalitis. The patient had persistent abnormal choreoathetoid movements and intermittent seizures despite multiple anti-epileptics, two courses of corticosteroids, two courses of intravenous immunoglobulin, two cycles (10 sessions per cycle) of plasmapheresis and a course of weekly rituximab. Due to the lack of response from these initial pharmacological interventions, the use of cyclophosphamide and mycophenolate mofetil was considered. Cyclophosphamide and mycophenolate mofetil inhibits the proliferations of B- and T-lymphocytes3 4 which acts as the basis of its immunosuppressive actions. However, available evidence on the dosing and monitoring information in the paediatric population for this unlicensed indication is limited.Pharmacy ContributionsAfter discussion with the multi-disciplinary team (MDT) with extensive input from the paediatric neurologist, a literature search was conducted to determine an appropriate dosing regimen. As this was an off-label use, the paediatric neurologist and the attending consultant took clinical responsibility. Intravenous cyclophosphamide was started at 750 mg/m2 once a month for three cycles and oral mycophenolate mofetil was started at 600 mg/m2 twice a day as maintenance therapy a week after. The specialist pharmacist explained the individualised treatment plan for the patient to the MDT and ensured measures (hydration and mesna) for the prevention of cyclophosphamide-induced haemorrhagic cystitis were appropriately prescribed on the electronic prescribing system with the appropriate timings of administration. Monitoring parameters to determine adverse effects were closely observed. A local guideline was developed during the treatment cycles to ensure all members of the MDT were following the correct procedures.OutcomeThe patient responded to cyclophosphamide and clinically improved after the completion of three cycles of monthly treatment. Maintenance mycophenolate mofetil was subsequently stopped a month after the last cycle of cyclophosphamide due to neutropenia. A review of the patient one year after first presentation shows the patient is almost back to their baseline.Lessons LearnedAlthough there are potentially serious side effects, cyclophosphamide and mycophenolate mofetil has been successful in the treatment of anti-NMDAR encephalitis. The recovery of this patient required extensive support from the entire MDT.ReferencesNHS England. Clinical Commissioning Policy: Rituximab for second line treatment for anti-NMDAR autoimmune encephalitis (all ages). March 2018.Salvucci A, Devine IM, Hammond D, et al. Pediatric anti-NMDA (N-methyl D-Aspartate) receptor encephalitis. Pediatric Neurology 2014;50:507–510.Summary of Product Characteristics. Cyclophosphamide 1000 mg Powder for Solution for Injection or Infusion. Last updated on eMC on 27-Jun-2017. Available at https://www.medicines.org.uk/emc/product/3525/smpc# [Accessed 04 July 2019]Summary of Product Characteristics. CellCept 1 g/5 mL powder for oral suspension. Last updated on eMC on 16-Mar-2018. Available at https://www.medicines.org.uk/emc/product/1569/smpc [Accessed 04 July 2019]

Pediatric Autoimmune Encephalitis: Case Series From Two Chinese Tertiary Pediatric Neurology Centers

Background and purpose: We retrospectively analyzed the clinical characteristics of children with autoimmune encephalitis (AE) in two Chinese tertiary pediatric neurology centers. We also compared anti-NMDAR encephalitis with and without co-positive MOG antibody, as well as specific autoantibody-positive AE and autoantibody-negative but probable AE.Methods: A retrospective study of children (0–18 years old) with AE in Peking University First Hospital and Children's Hospital Affiliated to Capital Institute of Pediatrics was carried out from May 2012 to January 2017. Demographics, clinical features, laboratory, and imaging findings, outcome, and co-positivity with MOG antibody were analyzed.Results: A total of 103 children had AE, 89 (86.4%) had anti-NMDAR encephalitis, 2 (1.9%) had anti-LGI1 encephalitis, 1 (0.9%) had anti-CASPR2 encephalitis, and 11 (10.7%) were diagnosed as autoantibody-negative but probable AE. Among the 89 children with anti-NMDAR encephalitis, 35 were males and 54 were females. The follow-up time was 1–3 years. A total of 15 cases (15/89, 16.9%) with anti-NMDAR encephalitis had co-positive MOG antibody (serum or cerebrospinal fluid or both). These patients were more likely to experience relapse later in life (P = 0.014). We had two cases with anti-LGI1 encephalitis, that is, one with sleep disorder onset, and the other one with seizure onset, both of whom recovered after treatment. One case with anti-CASPR2 encephalitis was treated with an antiepileptic drug and fully recovered. There were 11 cases diagnosed as autoantibody-negative but probable AE who had relatively poorer outcome than those with autoantibody-positive AE (15.2%, 14/89). However, the difference was not significant (P = 0.08). Only one 12-year-old girl with NMDAR-antibody AE had ovarian teratoma.Conclusion: Most subjects with AE in our Chinese cohort had anti-NMDAR AE, which had relatively good prognosis. Children with anti-LGI1 or anti-CASPR2 encephalitis were rare and showed good response on immunotherapy. Co-positive MOG antibody was relatively common in anti-NMDAR encephalitis, which was related to high relapse rate. In our study, the prognosis of autoantibody-negative but probable AE seemed worse than that of specific autoantibody-positive AE.

Two Case Reports of Neuropsychological Outcomes following Pediatric anti-N-methyl D-aspartate Receptor Autoimmune Encephalitis

ABSTRACTAnti-NMDAR autoimmune encephalitis is a rare neurological condition. Limited existing pediatric case studies have shown mild, but persisting, neuropsychological impairments. This report described neuropsychological functioning in two patients treated for anti-NMDAR autoimmune encephalitis. Patient A is a 16-year-old male (10 months after symptom onset) and Patient B is a 5-year-old female (45 months after symptom onset). Contrary to expectations, their cognitive profiles were largely intact, raising the possibility of minimal cognitive implications for some pediatric patients with this condition. Additional research is needed to identify factors that contribute to better cognitive outcomes in children with anti-NMDAR autoimmune encephalitis.

Adolescent with acute psychosis due to anti-N-methyl-D-aspartate receptor encephalitis: successful recovery

Abstract Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a relatively new autoimmune disorder of the central nervous system. We report the first case of anti-NMDAR autoimmune encephalitis combined with anti-voltage-gated potassium channel (anti-VGKC) antibodies in Lithuania in a 16-year-old girl. The patient was admitted to psychiatry unit because of an acute psychotic episode. She was unsuccessfully treated with antipsychotics, and electroconvulsive therapy was initiated because of her rapidly deteriorating condition. Electroconvulsive therapy improved the patient’s condition even before the initiation of immunomodulatory therapy. The abrupt onset, atypical and severe course of psychosis, poor response to antipsychotic treatment, and signs of flu-like prodromal period led to the search of non-psychiatric causes. Although with considerable delay, she was screened for an autoimmune encephalitis. Positive anti-NMDA receptor antibodies were found in the cerebrospinal fluid, but not in serum. In addition, serum was found positive for antinuclear antibodies and anti-VGKC antibodies but negative for CASPR2 and LGI1 antibodies. The girl was treated with intravenous immunoglobulin and methylprednisolone with satisfactory response, although infrequent orofacial movements, emotional lability, and learning deficits remained upon discharge. The reported case suggests that multiple antibodies could be present, and that electroconvulsive therapy may have a role in symptomatic treatment of autoimmune encephalitis.

Electroencephalographic and fluorodeoxyglucose-positron emission tomography correlates in anti-N-methyl-d-aspartate receptor autoimmune encephalitis

ImportanceAnti-N-methyl-d-aspartate receptor (anti-NMDAR) autoimmune encephalitis is an increasingly recognized cause of limbic encephalitis (LE). Prolonged LE and limbic status epilepticus (LSE) share many features. The ability to distinguish between the two is crucial in directing appropriate therapy because of the potential iatrogenesis associated with immunosuppression and anesthetic-induced coma.ObservationsA 34-year-old woman with recurrent LE developed behavioral changes, global aphasia, and repetitive focal and generalized tonic–clonic seizures. Because asymmetric rhythmic delta patterns recurred on electroencephalography (EEG) despite treatment with nonsedating antiepileptic drugs followed by anesthetic-induced coma, an investigation to distinguish LSE from LE was undertaken. Implanted limbic/temporal lobe depth electrodes revealed no epileptiform activity. Brain single-photon emission computerized tomography (SPECT) showed no hyperperfusion, and brain fluorodeoxyglucose-positron emission tomography (FDG-PET) showed hypermetabolism in the left frontal, temporal, and parietal cortices. Anti-N-methyl-d-aspartate receptor autoimmune encephalitis was diagnosed based detection of anti-NMDAR antibody in the cerebrospinal fluid (CSF). With chronic immunosuppression, the resolution of brain FDG-PET abnormalities paralleled clinical improvement.Conclusions and relevanceThis case of anti-NMDAR autoimmune encephalitis illustrates the challenges of distinguishing prolonged LE from LSE. We discuss the parallels between these two conditions and propose a management paradigm to optimize evaluation and treatment.

P266 Natalizumab is effective in a 5-year-old girl with steroid dependent relapsing ADEM

contact and the ability to walk; kept slight right upper limb hypertonia and occasional chorea. Lab results: minor pleocytosis (11 cells/mm3) on 1st CSF examination, normal CSF immunoelectrophoresis and normal neurotransmitters profile; negative auto-antibodies and complement fractions study; normal extensive metabolic and infectious investigations. 1st MR (D5) normal; 2nd MR (D13) showed T2 hypersignal on cerebellar cortex; 4th MR (D40) revealed atrophy of cerebellar hemispheres and slight cerebral diffuse atrophy. Recently, anti NMDAR antibodies sampling in frozen CSF from 1st lumbar puncture evidenced strong positivity; this study was repeated in blood and CSF, confirming strong positivity. Investigations to exclude occult neoplasia, were negative. The patient was treated with high dose steroids and intravenous imunne globulin. Conclusion: anti-NMDAR auto-immune encephalitis was described recently. Very few cases were reported in children. Our patient is one of the youngest. This disorder should be considered in the differential diagnosis of encephalitis with prominent psychiatric and extrapyramidal symptoms. This disorder, though severe, is frequently associated with a good therapeutic response.