Clinical characteristics and outcomes of patients with Herpes Simplex Encephalitis in Vietnam: a retrospective study.

BACKGROUND: Herpes simplex encephalitis (HSE) is an important central nervous infection with severe neurological sequelae. The aim of this study was to describe clinical characteristic and outcomes of patients with HSE in Vietnam. METHODS: This was a retrospective study of 66 patients with herpes simplex encephalitis who admitted to the National Hospital for Tropical Diseases, Hanoi, Vietnam from 2018 to 2021. The detection of herpes simplex virus (HSV) in cerebrospinal fluid was made by the real-time PCR assay. We reported the clinical manifestation on admission and evaluated clinical outcomes at the hospital discharge by modified Rankin Scale (mRS). Multivariate logistic regression analysis was used to analyze the independent risk factors of severe outcomes. RESULTS: Of the 66 patients with laboratory confirmed HSE, the median age was 53 years (IQR 38-60) and 44 patients (69.7%) were male. The most common manifestations included fever (100%), followed by the consciousness disorder (95.5%). Other neurological manifestation were seizures (36.4%), memory disorders (31.8%), language disorders (19.7%) and behavioral disorders (13.6%). Conventional magnetic resonance imaging (MRI) showed 93.8% patients with temporal lobe lesions, followed by abnormalities in insula (50%), frontal lobe (34.4%) and 48.4% of patients had bilateral lesions. At discharge, 19 patients (28.8%) completely recovered, 15 patients (22.7%) had mild sequelae, 28 patients (42.4%) had moderate to severe sequelae. Severe neurological sequelae were memory disorders (55.8%), movement disorders (53.5%), language disorders (30.2%). Multivariate logistic regression analysis showed that Glasgow score decrement at admission, seizures, and time duration from onset of symptoms to the start of Acyclovir treatment > 4 days were independent factors associated with severe outcomes in HSE patients. CONCLUSION: Glasgow score decrement, seizures and delay treatment with Acyclovir were associated with the poor outcome of patients with HSE.

Herpes Simplex Virus Encephalitis in Patients With Autoimmune Conditions or Exposure to Immunomodulatory Medications.

BACKGROUND AND OBJECTIVES: Among infectious etiologies of encephalitis, herpes simplex virus type 1 (HSV-1) is most common, accounting for ∼15%-40% of adult encephalitis diagnoses. We aim to investigate the association between immune status and HSV encephalitis (HSVE). Using a US Medicaid database of 75.6 million persons, we evaluated the association between HSVE and autoimmune conditions, exposure to immunosuppressive and immunomodulatory medications, and other medical comorbidities. METHODS: We used the US Medicaid Analytic eXtract data between 2007 and 2010 from the 29 most populated American states. We first examined the crude incidence of HSVE in the population. We then age and sex-matched adult cases of HSVE with a sufficient enrollment period (12 months before HSVE diagnosis) to a larger control population without HSVE. In a case-control analysis, we examined the association between HSVE and exposure to both autoimmune disease and immunosuppressive/immunomodulatory medications. Analyses were conducted with conditional logistic regression progressively adjusting for sociodemographic factors, Charlson Comorbidity Index, and non-autoimmune comorbidities. RESULTS: Incidence of HSVE was ∼3.01 per 105 person-years among adults. A total of 951 HSVE cases and 95,100 age and sex-matched controls were compared. The HSVE population had higher rates of medical comorbidities than the control population. The association of HSVE and autoimmune conditions was strong (adjusted odds ratio (OR) 2.6; 95% CI 2.2-3.2). The association of HSVE and immunomodulating medications had an OR of 2.2 (CI 1.9-2.6), also after covariate adjustment. When both exposures were included in regression models, the associations remained robust: OR 2.3 (CI 1.9-2.7) for autoimmune disease and 2.0 (CI 1.7-2.3) for immunosuppressive and immunomodulatory medications. DISCUSSION: In a large, national population, HSVE is strongly associated with preexisting autoimmune disease and exposure to immunosuppressive and immunomodulatory medications. The role of antecedent immune-related dysregulation may have been underestimated to date.

Herpes simplex encephalitis due to a mutation in an E3 ubiquitin ligase.

Encephalitis is a rare and potentially fatal manifestation of herpes simplex type 1 infection. Following genome-wide genetic analyses, we identified a previously uncharacterized and very rare heterozygous variant in the E3 ubiquitin ligase WWP2, in a 14-month-old girl with herpes simplex encephalitis. The p.R841H variant (NM_007014.4:c.2522G > A) impaired TLR3 mediated signaling in inducible pluripotent stem cells-derived neural precursor cells and neurons; cells bearing this mutation were also more susceptible to HSV-1 infection compared to control cells. The p.R841H variant increased TRIF ubiquitination in vitro. Antiviral immunity was rescued following the correction of p.R841H by CRISPR-Cas9 technology. Moreover, the introduction of p.R841H in wild type cells reduced such immunity, suggesting that this mutation is linked to the observed phenotypes.

Effect of resveratrol on herpesvirus encephalitis: Evidences for its mechanisms of action.

BACKGROUND: Herpes simplex virus type 1 (HSV-1)-induced herpes simplex encephalitis (HSE) has a high mortality rate in clinically immunocompromised patients, while recovered patients often experience neurological sequelae due to neuroinflammation. Nucleoside drugs and nucleoside analogues such as acyclovir and ganciclovir are mainly used in clinical treatment, and the emergence of resistant viral strains makes the development of new anti-herpesvirus encephalitis drugs urgent. Resveratrol is a multifunctional, plant-derived bioactive compound and its antiviral potential is attracting much attention. PURPOSE: This study aimed to investigate the anti-HSV-1 mechanism of resveratrol in microglial cells and in the HSE mouse model. METHODS: The antiviral effect of resveratrol on HSV-1 infection was investigated by plaque assay, virus titer, immunofluorescence, Western blot and time-of-addition assay. The influence of resveratrol on stimulator of interferon gene (STING)/Nuclear Factor kappa B (NF-κB) signaling pathway-mediated neuroinflammation was examined by Western blot, RT-qPCR and ELISA. The interaction between resveratrol and STING/heat shock protein 90 beta (HSP90ß) was evaluated by molecular modeling, co-immunoprecipitation, and drug affinity responsive target stability assay. The therapeutic effect of resveratrol on HSE was evaluated in the HSE mouse model by analyzing weight loss, neurodegenerative symptoms and histopathological scores. RESULTS: Resveratrol inhibited the early process of HSV-1 infection, and interfered with the STING/NF-κB signaling pathway to attenuate HSV-1-induced neuroinflammation and microglial M1 polarization, independent of its classical target Sirtuin1. Mechanistically, resveratrol completely bound to Glu515 and Lys491 of HSP90ß, thus disrupting the HSP90ß-STING interaction and promoting STING degradation. Resveratrol also significantly alleviated viral encephalitis and neuroinflammation caused by HSV-1 in the HSE mouse model. CONCLUSION: Resveratrol acted as a non-classical HSP90ß inhibitor, binding to the STING-HSP90ß interaction site to promote STING degradation and attenuate HSV-1-induced encephalitis and neuroinflammation. These findings suggest the alternative strategy of targeting HSP90ß and resveratrol-mediated inhibition of HSP90ß as a potential antiviral approach.

Neonatal herpes simplex virus encephalitis with intracranial bleeding in a newborn baby with concurrent rhesus incompatibility.

We report a baby with neonatal herpes simplex virus (HSV) encephalitis concurrent with Rrhesus (Rh) incompatibility. He was delivered by a Ggravida 2 mother with a history of miscarriage in her previous pregnancy at a gestation age of 4 months. She had Bblood group 0 and Rrhesus negative. The baby was noticed to have jaundice on day one1 of life accompanied by generalised petechiae on the face and upper chest. A full blood picture revealed severe anaemia and severe thrombocytopaenia and HSV 1/2 IgM was positive. MRI of the brain showed multiple extensive haemorrhagic lesions on the frontal-temporal regions.

Acyclovir dosing in herpes encephalitis: A scoping review.

BACKGROUND: Herpes encephalitis, a rare yet potentially fatal viral infection, is treated exclusively with acyclovir, the sole antiviral medication used for this condition. Acyclovir recommended dose is 10 mg/kg/dose intravenous every 8 hours; however, it is unclear what body weight should be utilized in obese patients. Using the ideal body weight may result in subtherapeutic ineffective concentrations, while utilizing the actual body weight might result in acyclovir induced adverse effects, either nephrotoxicity or neurotoxicity or both. OBJECTIVE: The objective of this scoping review is to explore existing evidence regarding acyclovir dosing for obese patients afflicted with herpes encephalitis. METHODS: MEDLINE, EMBASE, Scopus, Web of Science, and CINAHL databases were searched on 26 May 2023, with no language restrictions. Two independent reviewers utilized the Covidence software to carry out the screening and selection of the articles. A total of 22 articles were included in the current review. RESULTS: The prevalence of acyclovir-associated nephrotoxicity ranged from 13% to 21%, while the prevalence of neurotoxicity was not clearly defined. However, there is lack of evidence regarding what may arise from subtherapeutic concentrations. An approach has been suggested to help clinicians to give the most appropriate acyclovir dose to herpes encephalitis patients. Patients with normal kidney function could receive the normal doses based on actual weight if normal weight and based on adjusted body weight if obese. On the other hand, if the patients are experiencing augmented renal clearance, they could receive up to the maximum recommended doses. CONCLUSION: Overall, there is a lack of consistency on which body weight to use to calculate acyclovir dose in obese patients. So it is recommended that further studies compare the concentration of intravenous acyclovir between obese and nonobese patients and relating the resultant concentration with patient outcomes.

Herpes simplex virus infection induces necroptosis of neurons and astrocytes in human fetal organotypic brain slice cultures.

BACKGROUND: Herpes simplex virus (HSV) encephalitis (HSE) is a serious and potentially life-threatening disease, affecting both adults and newborns. Progress in understanding the virus and host factors involved in neonatal HSE has been hampered by the limitations of current brain models that do not fully recapitulate the tissue structure and cell composition of the developing human brain in health and disease. Here, we developed a human fetal organotypic brain slice culture (hfOBSC) model and determined its value in mimicking the HSE neuropathology in vitro. METHODS: Cell viability and tissues integrity were determined by lactate dehydrogenase release in supernatant and immunohistological (IHC) analyses. Brain slices were infected with green fluorescent protein (GFP-) expressing HSV-1 and HSV-2. Virus replication and spread were determined by confocal microscopy, PCR and virus culture. Expression of pro-inflammatory cytokines and chemokines were detected by PCR. Cell tropism and HSV-induced neuropathology were determined by IHC analysis. Finally, the in situ data of HSV-infected hfOBSC were compared to the neuropathology detected in human HSE brain sections. RESULTS: Slicing and serum-free culture conditions were optimized to maintain the viability and tissue architecture of ex vivo human fetal brain slices for at least 14 days at 37 °C in a CO2 incubator. The hfOBSC supported productive HSV-1 and HSV-2 infection, involving predominantly infection of neurons and astrocytes, leading to expression of pro-inflammatory cytokines and chemokines. Both viruses induced programmed cell death-especially necroptosis-in infected brain slices at later time points after infection. The virus spread, cell tropism and role of programmed cell death in HSV-induced cell death resembled the neuropathology of HSE. CONCLUSIONS: We developed a novel human brain culture model in which the viability of the major brain-resident cells-including neurons, microglia, astrocytes and oligodendrocytes-and the tissue architecture is maintained for at least 2 weeks in vitro under serum-free culture conditions. The close resemblance of cell tropism, spread and neurovirulence of HSV-1 and HSV-2 in the hfOBSC model with the neuropathological features of human HSE cases underscores its potential to detail the pathophysiology of other neurotropic viruses and as preclinical model to test novel therapeutic interventions.

Mice with type I interferon signaling deficiency are prone to epilepsy upon HSV-1 infection.

Viral encephalitis continues to be a significant public health concern. In our previous study, we discovered a lower expression of antiviral factors, such as IFN-ß, STING and IFI16, in the brain tissues of patients with Rasmussen's encephalitis (RE), a rare chronic neurological disorder often occurred in children, characterized by unihemispheric brain atrophy. Furthermore, a higher cumulative viral score of human herpes viruses (HHVs) was also found to have a significant positive correlation with the unihemispheric atrophy in RE. Type I IFNs (IFN-I) signaling is essential for innate anti-infection response by binding to IFN-α/ß receptor (IFNAR). In this study, we infected WT mice and IFNAR-deficient A6 mice with herpes simplex virus 1 (HSV-1) via periocular injection to investigate the relationship between IFN-I signaling and HHVs-induced brain lesions. While all mice exhibited typical viral encephalitis lesions in their brains, HSV-induced epilepsy was only observed in A6 mice. The gene expression matrix, functional enrichment analysis and protein-protein interaction network revealed four gene models that were positively related with HSV-induced epilepsy. Additionally, ten key genes with the highest scores were identified. Taken together, these findings indicate that intact IFN-I signaling can effectively limit HHVs induced neural symptoms and brain lesions, thereby confirming the positive correlation between IFN-I signaling repression and brain atrophy in RE and other HHVs encephalitis.

Adjunctive Intravenous Immunoglobulin and Glucocorticoid Therapy in Severe Herpes Simplex Encephalitis with Excellent Outcome Begs for Larger Trials Evaluating Immunomodulatory Therapy.

BACKGROUND Despite the preponderance of evidence of immune-driven pathophysiology of disease in herpes simplex virus-1 (HSV-1) encephalitis, current treatment paradigms do not officially recommend adjunctive immunomodulatory therapy in addition to acyclovir. This may in part explain the poor long-term outcomes in patients with severe HSV encephalitis. This report is of a 21-year-old man presenting with a 4-day history of nausea, headache, and fever and a diagnosis of HSV-1 encephalitis. CASE REPORT We describe the case of a young male with clinically and radiographically severe HSV-1 encephalitis diagnosed by PCR of cerebrospinal fluid (CSF), who demonstrated immediate improvement upon treatment with intravenous immunoglobulin (IVIG, 0.5 g/kg daily ×3 days) in addition to acyclovir and dexamethasone therapy. Acyclovir therapy was extended beyond 21 days due to persistently positive HSV-1 CSF PCR. He developed N-methyl-D-aspartate (NMDA) receptor antibodies at 6 weeks, but his long-term outcome far exceeded expectations. While some of his neurological deficits appear to be permanent, he is living a normal life. CONCLUSIONS Overwhelming evidence demonstrates that brain injury due to HSV encephalitis is driven by immune reactions stimulated by HSV rather than HSV itself. Nevertheless, use of immunomodulatory therapy such as glucocorticoids and IVIG are left to the discretion of individual clinicians rather than being recommended in treatment guidelines, which instead recommend acyclovir therapy. The present case highlights the potential role of immunomodulatory therapy with IVIG in HSV encephalitis and the importance of early diagnosis and treatment.

The immunobiology of herpes simplex virus encephalitis and post-viral autoimmunity.

Herpes simplex virus encephalitis (HSE) is the leading cause of non-epidemic encephalitis in the developed world and, despite antiviral therapy, mortality and morbidity is high. The emergence of post-HSE autoimmune encephalitis reveals a new immunological paradigm in autoantibody-mediated disease. A reductionist evaluation of the immunobiological mechanisms in HSE is crucial to dissect the origins of post-viral autoimmunity and supply rational approaches to the selection of immunotherapeutics. Herein, we review the latest evidence behind the phenotypic progression and underlying immunobiology of HSE including the cytokine/chemokine environment, the role of pathogen-recognition receptors, T- and B-cell immunity and relevant inborn errors of immunity. Second, we provide a contemporary review of published patients with post-HSE autoimmune encephalitis from a combined cohort of 110 patients. Third, we integrate novel mechanisms of autoimmunization in deep cervical lymph nodes to explore hypotheses around post-HSE autoimmune encephalitis and challenge these against mechanisms of molecular mimicry and others. Finally, we explore translational concepts where neuroglial surface autoantibodies have been observed with other neuroinfectious diseases and those that generate brain damage including traumatic brain injury, ischaemic stroke and neurodegenerative disease. Overall, the clinical and immunological landscape of HSE is an important and evolving field, from which precision immunotherapeutics could soon emerge.

Unmasking bipolarity in recurrent depressive disorder following herpes simplex virus triggered n-methyl-D-aspartate encephalitis.

OBJECTIVE: Herpes simplex virus (HSV) infection triggered n-methyl-D-aspartate (NMDA) encephalitis can lead to varied neuropsychiatric manifestations, including movement disorders and manic symptoms. HSV is known to affect the same brain regions as in secondary mania. METHOD: We present a 35-year-old female diagnosed with recurrent depressive disorder (RDD) who developed NMDA encephalitis triggered by HSV infection. RESULT: HSV-triggered NMDA encephalitis led to a manic switch in a woman with RDD on antidepressants, along with the new onset of dyskinetic movements. CONCLUSION: A neurological insult predisposed our patient to the variable effects of antidepressant drugs.

The split apparent diffusion coefficient sign: A novel magnetic resonance imaging biomarker for cortical pathology with possible implications in autoimmune encephalitis.

INTRODUCTION: MRI is the imaging modality of choice for assessing patients with encephalopathy. In this context, we discuss a novel biomarker, the "split ADC sign," where the cerebral cortex demonstrates restricted diffusion (high DWI signal and low ADC) and the underlying white matter demonstrates facilitated diffusion (high or low DWI signal and high ADC). We hypothesize that this sign can be used as a biomarker to suggest either acute encephalitis onset or to raise the possibility of an autoimmune etiology. MATERIALS AND METHODS: A full-text radiological information system search of radiological reports was performed for all entities known to produce restricted diffusion in the cortex excluding stroke between January 2012 and June 2022. Initial MRI studies performed upon onset of clinical symptoms were screened for the split ADC sign. RESULTS: 25 subjects were encountered with a positive split ADC sign (15 female; median age = 57 years, range 18-82). Diagnosis included six herpes simplex encephalitis, three peri-ictal MRI changes, eight PRES, two MELAS, and six autoimmune (3 anti-GABAAR, two seronegative, and one anti-Ma2/Ta). Subjects were imaged at a mean 1.8 days after the onset of symptoms (range 0-8). DISCUSSION: We present a novel visual MRI biomarker, the split ADC sign, and highlight its potential usefulness in subjects with encephalopathy to suggest acute disease onset or to raise the possibility of an autoimmune etiology when location-based criteria are applied. When positive, the sign was present on the initial MRI and can therefore be used to help focus further clinical and laboratory workup.

Encefalitis autoinmune posherpética. Caso clínico pediátrico / Autoimmune post-herpes simplex encephalitis. A pediatric clinical case report

La encefalitis por virus herpes simple (VHS) es una causa frecuente de encefalitis grave y potencialmente fatal. La encefalitis autoinmune posherpética (EAPH) afecta a un porcentaje de los pacientes que han presentado encefalitis herpética (EH) y se caracteriza por la aparición de nuevos síntomas neurológico/psiquiátricos, y/o por el empeoramiento de los déficits adquiridos durante la infección viral dentro de un lapso temporal predecible. Se produce por un mecanismo no relacionado con el VHS, sino por fenómenos autoinmunes, y es susceptible de tratamiento con inmunomoduladores. Se presenta el caso de un varón de 5 años de edad con EAPH que requirió tratamiento inmunomodulador, de primera y segunda línea, con buena evolución y remisión de los síntomas.

Herpes simplex virus (HSV) encephalitis is a common cause of severe and potentially fatal encephalitis. Autoimmune post-herpes simplex encephalitis (AIPHSE) affects a percentage of patients who developed herpes simplex encephalitis (HSE) and is characterized by the onset of new neurological/psychiatric symptoms and/or worsening of deficits acquired during the herpes infection within a predictable time frame. It is caused by a mechanism not related to HSV, but by autoimmune conditions, and is susceptible to treatment with immunomodulators. Here we describe the case of a 5-year-old boy with AIPHSE who required first- and second-line immunomodulatory treatment, with an adequate course and remission of symptoms.

Herpes Simplex Virus Encephalitis after Recovery from Coronavirus Disease 2019: A Rare Case Report.

An 85-year-old woman was diagnosed with coronavirus disease 2019 (COVID-19). The patient was treated with dexamethasone, and the infection was cured. She later developed a low-grade fever and fell unconscious. Positivity for herpes simplex virus deoxyribonucleic acid polymerase chain reaction (HSV-DNA PCR) was detected in the cerebrospinal fluid, so she was diagnosed with HSV encephalitis. The patient was treated with antiviral drugs and recovered from the HSV encephalitis. This case suggests that, in patients with COVID-19 and disorders of consciousness, the possibility of HSV encephalitis should be considered along with COVID-19 encephalitis.

A case of successful hormone therapy for refractory hypotension following viral encephalitis: Case report.

RATIONALE: Refractory hypotension is a life-threatening condition that can result from various causes. We report a rare case of refractory hypotension following herpes simplex virus type 1 encephalitis that was successfully treated with hormone therapy. PATIENT CONCERNS: The patient was a 66-year-old male who was admitted to the hospital because of fever, chills, convulsions, and impaired consciousness. He developed respiratory failure and was intubated. Cerebrospinal fluid metagenomic sequencing confirmed herpes simplex virus type 1 infection. He received piperacillin-tazobactam for anti-infection, acyclovir for antiviral therapy, and dexamethasone for anti-inflammatory therapy. He had repeated episodes of hypotension despite fluid resuscitation and vasopressor therapy. DIAGNOSIS: The diagnosis of herpes simplex virus type 1 encephalitis complicated by refractory hypotension was based on the patient's epidemiological history, clinical manifestations, laboratory tests, and imaging studies. Cerebrospinal fluid examination was the most important diagnostic method, which could detect viral nucleic acids. Head magnetic resonance imaging showed a large recent lesion in the right temporal-parietal and insular lobes. INTERVENTIONS: The treatment of refractory hypotension mainly included anti-infection, antiviral, anti-inflammatory, and hormone therapy. Hormone therapy used methylprednisolone shock treatment until tapering withdrawal. Other treatments included fluid resuscitation, vasopressors, anticonvulsants, etc. OUTCOMES: The patient's blood pressure stabilized after receiving methylprednisolone shock treatment, and his mean arterial pressure increased from 73 mm Hg to 92 mm Hg within 24 hours. Three months later, the patient's blood pressure was normal without medication, and he had a good social and physical recovery. LESSONS: This case illustrates the possible role of hormone therapy in restoring blood pressure in patients with refractory hypotension following viral encephalitis. It suggests that adrenal insufficiency or autonomic dysfunction may be involved in the pathophysiology of this condition. Further studies are needed to confirm the efficacy and safety of hormone therapy in this setting.

Case report: severe course of encephalitis of unknown origin.

The exact cause of encephalitis is still unclear in many cases, although the common etiological factors of this process are viruses such as herpes simplex virus and rabies virus, and also bacteria, fungi, parasites, several medicines and autoimmune diseases. Herein, we report a case of a 56-year-old man with a history of amnestic syndrome, impaired consciousness, somnolence throughout the day, headache, dizziness and hypertension, who was admitted to hospital with suspected neurological disease, and imaging features that were consistent with encephalitis of unknown etiology. Methods which were used to examine patient: cerebrospinal fluid testing, PCR examinations for viruses, testing of antibodies against surface antigens, magnetic resonance imaging of the head, psychiatric consultation, oncology consultation. The objective of this study is to demonstrate a case about an uncommon neurologic condition, which every clinician might meet in clinical practice. In this type of cases, the use of steroids such as dexamethasone and methylprednisolone might lead to a full recovery.

Neurological syndromes and potential triggers associated with antibodies to neuronal surface antigens.

BACKGROUND: Autoantibodies against surface neuronal antigens have been associated with specific neurological presentations including autoimmune encephalitis (AE), with variable association with neoplasia and infections. METHODS: We described the phenotype and environmental associations of patients with neurological syndromes associated with antibodies against neuronal surface antigens who were referred to a tertiary center in the South of Brazil. All patients were tested for neuronal autoantibodies using cell-based assays. Clinical, radiological, and laboratory findings were retrospectively reviewed. RESULTS: We identified 16 patients, 15 had subacute, and one had a progressive disease course. Among patients with subacute onset, 11 (73 %) were N-Methyl-d-Aspartate receptor (NMDAr-IgG)+, 3 (20 %) were Leucine-rich Glioma-Inactivated-1 (LGI1-IgG)+, and 1 (6 %) was positive for Glycine receptor-IgG. The patient with a progressive disease course had antibodies against IgLON5. Most patients had disease onset in spring and summer suggesting environmental factors for the development of AE. Also, we observed a different pattern of brain lesions when NMDAr-IgG encephalitis followed herpes encephalitis and a previously unreported association with Rosai-Dorfman-Destombe disease. All patients with encephalopathy met criteria for possible AE and all proven NMDAr-IgG+ met criteria for NMDAr-IgG encephalitis. However, only one LGI1-IgG+ patient fulfilled clinical criteria for limbic encephalitis. All but one received high-dose intravenous methylprednisolone, 11 also had intravenous human immunoglobulin, and 4 plasma exchange. Furthermore, all patients received second-line immunotherapy. Importantly, most patients improved with immunotherapy, even when initiated later in the disease course. CONCLUSION: We identified seasonal variability associated with neuronal surface antibodies suggesting environmental triggers. Also, we described the coexistence of NMDAr-IgG encephalitis with histiocytosis. In our series, most patients received second-line immunotherapy. We observed neurologic improvement after treatment even in cases of delayed diagnosis. Increasing the recognition and availability of tests and treatments for these conditions is of paramount importance in low- and middle-income countries.