Neuropathological spectrum of anti-IgLON5 disease and stages of brainstem tau pathology: updated neuropathological research criteria of the disease-related tauopathy.

Anti-IgLON5 disease is a unique condition that bridges autoimmunity and neurodegeneration. Since its initial description 10 years ago, an increasing number of autopsies has led to the observation of a broader spectrum of neuropathologies underlying a particular constellation of clinical symptoms. In this study, we describe the neuropathological findings in 22 patients with anti-IgLON5 disease from 9 different European centers. In 15 patients (68%), we observed a hypothalamic and brainstem-predominant tauopathy of varying severity in which the original research neuropathological criteria were readily applicable. This pathology was observed in younger patients (median age at onset 61 years) with a long disease duration (median 9 years). In contrast, in 7 (32%) patients, the originally described brainstem tauopathy was nearly absent or only minimal in the form of delicate threads, despite mild-to-moderate neurodegenerative features, consistent clinical symptoms and the presence of anti-IgLON5 antibodies in CSF and serum. These patients were older at onset (median 79 years) and had shorter disease duration (median < 1 year). Overall, about one-third of the patients showed concomitant TDP-43 pathology within the regions affected by tau pathology and/or neurodegeneration. Based on these observations and in view of the spectrum of the tau burden in the core regions involved in the disease, we propose a simple staging system: stage 1 mild neurodegeneration without overt or only minimal tau pathology, stage 2 moderate neurodegeneration and mild/ moderate tauopathy and stage 3 prominent neurodegeneration and tau pathology. This staging intends to reflect a potential (age- and time-dependent) progression of tau pathology, supporting the current notion that tau accumulation is a secondary phenomenon related to the presence of anti-IgLON5 antibodies in the CNS. Finally, we adapt the original research criteria of the anti-IgLON5 disease-related tauopathy to include the spectrum of pathologies observed in this larger postmortem series.

Neurologic complications in herpes simplex encephalitis: clinical, immunological and genetic studies.

Patients with herpes simplex virus (HSV) encephalitis (HSE) often develop neuronal autoantibody-associated encephalitis (AE) post-infection. Risk factors of AE are unknown. We tested the hypotheses that predisposition for AE post-HSE may be involved, including genetic variants at specific loci, human leucocyte (HLA) haplotypes, or the blood innate immune response against HSV, including type I interferon (IFN) immunity. Patients of all ages with HSE diagnosed between 1 January 2014 and 31 December 2021 were included in one of two cohorts depending on whether the recruitment was at HSE onset (Spanish Cohort A) or by the time of new neurological manifestations (international Cohort B). Patients were assessed for the type of neurological syndromes; HLA haplotypes; blood type I-IFN signature [RNA quantification of 6 or 28 IFN-response genes (IRG)] and toll-like receptor (TLR3)-type I IFN-related gene mutations. Overall, 190 patients (52% male) were recruited, 93 in Cohort A and 97 in Cohort B. Thirty-nine (42%) patients from Cohort A developed neuronal autoantibodies, and 21 (54%) of them developed AE. Three syndromes (choreoathetosis, anti-NMDAR-like encephalitis and behavioural-psychiatric) showed a high (≥95% cases) association with neuronal autoantibodies. Patients who developed AE post-HSE were less likely to carry the allele HLA-A*02 (4/21, 19%) than those who did not develop AE (42/65, 65%, P = 0.0003) or the Spanish general population (2005/4335, 46%, P = 0.0145). Blood IFN signatures using 6 or 28 IRG were positive in 19/21 (91%) and 18/21 (86%) patients at HSE onset, and rapidly decreased during follow-up. At Day 21 after HSE onset, patients who later developed AE had higher median IFN signature compared with those who did not develop AE [median Zs-6-IRG 1.4 (0.6; 2.0) versus 0.2 (-0.4; 0.8), P = 0.03]. However, a very high median Zs-6-IRG (>4) or persistently increased IFN signature associated with uncontrolled viral infection. Whole exome sequencing showed that the percentage of TLR3-IFN-related mutations in patients who developed AE was not different from those who did not develop AE [3/37 (8%) versus 2/57 (4%), P = 0.379]. Multivariate logistic regression showed that a moderate increase of the blood IFN signature at Day 21 (median Zs-6-IRG >1.5 but <4) was the most important predictor of AE post-HSE [odds ratio 34.8, interquartile ratio (1.7-691.9)]. Altogether, these findings show that most AE post-HSE manifest with three distinct syndromes, and HLA-A*02, but not TLR3-IFN-related mutations, confer protection from developing AE. In addition to neuronal autoantibodies, the blood IFN signature in the context of HSE may be potentially useful for the diagnosis and monitoring of HSE complications.

Encephalitis with Autoantibodies against the Glutamate Kainate Receptors GluK2.

OBJECTIVE: The objective of this study was to report the identification of antibodies against the glutamate kainate receptor subunit 2 (GluK2-abs) in patients with autoimmune encephalitis, and describe the clinical-immunological features and antibody effects. METHODS: Two sera from 8 patients with similar rat brain immunostaining were used to precipitate the antigen from neuronal cultures. A cell-based assay (CBA) with GluK2-expressing HEK293 cells was used to assess 596 patients with different neurological disorders, and 23 healthy controls. GluK2-ab effects were determined by confocal microscopy in cultured neurons and electrophysiology in GluK2-expressing HEK293 cells. RESULTS: Patients' antibodies precipitated GluK2. GluK2 antibody-specificity was confirmed by CBA, immunoprecipitation, GluK2-immunoabsorption, and GluK2 knockout brain immunohistochemistry. In 2 of 8 samples, antibodies reacted with additional GluK2 epitopes present in GluK1 or GluK3; in both, the reactivity was abrogated after GluK2 immuno-absorption. Six of 8 patients developed acute encephalitis and clinical or magnetic resonance imaging (MRI) features of predominant cerebellar involvement (4 presenting as cerebellitis, which in 2 patients caused obstructive hydrocephalus), and 2 patients had other syndromes (1 with cerebellar symptoms). One of the samples showed mild reactivity with non-kainate receptors (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors [AMPAR] and N-methyl-D-aspartate receptors [NMDAR]) leading to identify 6 additional cases with GluK2-abs among patients with anti-AMPAR (5/71) or anti-NMDAR encephalitis (1/73). GluK2-abs internalized GluK2 in HEK293 cells and neurons; these antibody-effects were reversible in neurons. A significant reduction of GluK2-mediated currents was observed in cells treated with patients' GluK2 serum following the time frame of antibody-mediated GluK2 internalization. INTERPRETATION: GluK2-abs associate with an encephalitis with prominent clinicoradiological cerebellar involvement. The antibody effects are predominantly mediated by internalization of GluK2. ANN NEUROL 2021;90:107-123.

Higher Solar Irradiance Is Associated With a Lower Incidence of Coronavirus Disease 2019.

We studied the relationship between the incidence of coronavirus disease 2019 (COVID-19), demographical, and climatological measurements in different regions across the world. Lower solar irradiance and higher population density were independent predictors of greater COVID-19 outbreaks. Further studies on the potential protective effect of sunlight over COVID-19 are warranted.

Electroconvulsive therapy in N-methyl-d-aspartate receptor encephalitis: A retrospective cohort and scoping review of literature.

Neuropsychiatric symptoms in N-methyl-d-aspartate receptor encephalitis (NMDARE) have led some to pursue empiric trials of electroconvulsive therapy (ECT). A scoping review identified 39 patients diagnosed with NMDARE undergoing ECT. Separately, a retrospective cohort was reviewed to characterize 21 patients. Clinical improvement was attributed to ECT in 49% of patients in the scoping review and 19% of patients in the retrospective cohort; timing of immunotherapies was a confounding factor. Worsening of clinical course following ECT was reported in 28% of patients in the scoping review and 38% of patient in the retrospective review. There is currently insufficient data supporting a beneficial effect of ECT in NMDARE.

MOG Antibodies Restricted to CSF in Children With Inflammatory CNS Disorders.

OBJECTIVES: To assess the clinical significance of myelin oligodendrocyte glycoprotein antibodies (MOG-abs) restricted to CSF in children with inflammatory CNS disorders. METHODS: Patients included 760 children (younger than 18 years) from 3 multicenter prospective cohort studies: (A) acquired demyelinating syndromes, including acute disseminated encephalomyelitis (ADEM); (B) non-ADEM encephalitis; and (C) noninflammatory neurologic disorders. For all cases, paired serum/CSF samples were systematically examined using brain immunohistochemistry and live cell-based assays. RESULTS: A total of 109 patients (14%) had MOG-abs in serum or CSF: 79 from cohort A, 30 from B, and none from C. Of these, 63 (58%) had antibodies in both samples, 37 (34%) only in serum, and 9 (8%) only in CSF. Children with MOG-abs only in CSF were older than those with MOG-abs only in serum or in both samples (median 12 vs 6 vs 5 years, p = 0.0002) and were more likely to have CSF oligoclonal bands (86% vs 12% vs 7%, p = 0.0001) and be diagnosed with multiple sclerosis (6/9 [67%] vs 0/37 [0%] vs 1/63 [2%], p < 0.0001). DISCUSSION: Detection of MOG-abs in serum or CSF is associated with CNS inflammatory disorders. Children with MOG-abs restricted to CSF are more likely to have CSF oligoclonal bands and multiple sclerosis than those with MOG-abs detectable in serum.

Neurological, psychiatric, and sleep investigations after treatment of anti-leucine-rich glioma-inactivated protein 1 (LGI1) encephalitis in Spain: a prospective cohort study.

BACKGROUND: Anti-leucine-rich glioma-inactivated protein 1 (LGI1) encephalitis is an autoimmune disorder that can be treated with immunotherapy, but the symptoms that remain after treatment have not been well described. We aimed to characterise the clinical features of patients with anti-LGI1 encephalitis for 1 year starting within the first year after initial immunotherapy. METHODS: For this prospective cohort study, we recruited patients with anti-LGI1 encephalitis as soon as possible after they had received conventional immunotherapy for initial symptoms; patients were recruited from 21 hospitals in Spain. Patients were excluded if they had an interval of more than 1 year since initial immunotherapy, had pre-existing neurodegenerative or psychiatric disorders, or were unable to travel to Hospital Clínic de Barcelona (Barcelona, Spain). Patients visited Hospital Clínic de Barcelona on three occasions-the first at study entry (visit 1), the second 6 months later (visit 2), and the third 12 months after the initial visit (visit 3). They underwent neuropsychiatric and videopolysomnography assessments at each visit. Healthy participants who were matched for age and sex and recruited from Hospital Clínic de Barcelona underwent the same investigations at study entry and at 12 months. Cross-sectional comparisons of clinical features between groups were done with conditional logistic regression, and binary logistic regression was used to assess associations between cognitive outcomes at 12 months and clinical features before initial immunotherapy and at study entry. FINDINGS: Between May 1, 2019, and Sept 30, 2022, 42 participants agreed to be included in this study. 24 (57%) participants had anti-LGI1 encephalitis (mean age 63 years [SD 12]; 13 [54%] were female and 11 [46%] were male) and 18 (43%) were healthy individuals (mean age 62 years [10]; 11 [61%] were female and seven [39%] were male). At visit 1 (median 88 days [IQR 67-155] from initiation of immunotherapy), all 24 patients had one or more symptoms; 20 (83%) patients had cognitive deficits, 20 (83%) had psychiatric symptoms, 14 (58%) had insomnia, 12 (50%) had rapid eye movement (REM)-sleep behaviour disorder, nine (38%) had faciobrachial dystonic seizures, and seven (29%) had focal onset seizures. Faciobrachial dystonic seizures were unnoticed in four (17%) of 24 patients and focal onset seizures were unnoticed in five (21%) patients. At visit 1, videopolysomnography showed that 19 (79%) patients, but no healthy participants, had disrupted sleep structure (p=0·013); 15 (63%) patients and four (22%) healthy participants had excessive fragmentary myoclonus (p=0·039), and nine (38%) patients, but no healthy participants, had myokymic discharges (p=0·0051). These clinical and videopolysomnographic features led to additional immunotherapy in 15 (63%) of 24 patients, which resulted in improvement of these features in all 15 individuals. However, at visit 3, 13 (65%) of 20 patients continued to have cognitive deficits. Persistent cognitive deficits at visit 3 were associated with no use of rituximab before visit 1 (odds ratio [OR] 4·0, 95% CI 1·5-10·7; p=0·0015), REM sleep without atonia at visit 1 (2·2, 1·2-4·2; p=0·043), and presence of LGI1 antibodies in serum at visit 1 (11·0, 1·1-106·4; p=0·038). INTERPRETATION: Unsuspected but ongoing clinical and videopolysomnography alterations are common in patients with anti-LGI1 encephalitis during the first year or more after initial immunotherapy. Recognising these alterations is important as they are treatable, can be used as outcome measures in clinical trials, and might influence cognitive outcome. FUNDING: Fundació La Caixa.

CD19-Directed CAR T-Cells in a Patient With Refractory MOGAD: Clinical and Immunologic Follow-Up for 1 Year.

OBJECTIVES: In MOG antibody-associated disease (MOGAD), relapse prevention and the treatment approach to refractory symptoms are unknown. We report a patient with refractory MOGAD treated with CD19-directed CAR T-cells. METHODS: CD19-directed CAR T-cells (ARI-0001) were produced in-house by lentiviral transduction of autologous fresh leukapheresis and infused after a conventional lymphodepleting regimen. RESULTS: A 18-year-old man developed 2 episodes of myelitis associated with serum MOG-IgG, which were followed by 6 episodes of left optic neuritis (ON) and sustained the presence of MOG-IgG over 6 years despite multiple immunotherapies. After the sixth episode of ON, accompanied by severe residual visual deficits, CAR T-cell treatment was provided without complications. Follow-up of cell counts showed complete depletion of CD19+ B cells at day +7; reconstituted B cells at day +141 showing a naïve B-cell phenotype, and low or absent memory B cells and plasmablasts for 1 year. MOG-IgG titers have remained undetectable since CAR T-cell infusion. The patient had an early episode of left ON at day +29, when MOG-IgG was already negative, and since then he has remained free of relapses without immunotherapy for 1 year. DISCUSSION: This clinical case shows that CD19-directed CAR T-cell therapy is well-tolerated and is a potential treatment for patients with refractory MOGAD. CLASSIFICATION OF EVIDENCE: This provides Class IV evidence. It is a single observational study without controls.

Investigating the 2023 MOGAD Criteria in Children and Adults With MOG-Antibody Positivity Within and Outside Attacks.

BACKGROUND AND OBJECTIVES: The 2023 criteria for myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) perform well in adults but have not been assessed in children. METHODS: This prospective observational nationwide study includes children and adults with demyelinating syndromes or encephalitis, whose serum or CSF was found MOG-immunoglobulin G (IgG) positive at Institut d'Investigacions Biomèdiques August Pi i Sunyer-Hospital Clínic of Barcelona (Spain). Exclusion criteria were lack of clinical information and follow-up <1 year, and serum unavailable for antibody testing. The primary outcome was to assess the accuracy of the 2023 MOGAD criteria, using as gold standard the most plausible diagnosis after a follow-up >1 year. MOGAD criteria were retrospectively applied assessing core syndromes, supportive clinical-radiological features, and MOG-IgG titers. Patients tested ≤3 months of a disease attack (acute phase) or afterward (remission) were considered separately. The positive predictive value (PPV) of the criteria (true-positive [patients classified as MOGAD and MOGAD diagnosis last follow-up] divided by total positive [all patients classified as MOGAD]), and its 95% CI, was calculated with the Wilson procedure. RESULTS: A total of 257 patients (133 children) were included in the study (median age 15 years [interquartile range 6-38], 54% female). Among 202 patients assessed during a disease attack, 158 (78%) had high MOG-IgG serum titers, 36 (18%) low titers, and 8 (4%) antibodies only in CSF. No differences were identified between patients with high and low titers, but those with low titers were more likely to have an alternative diagnosis at last follow-up (2/36 [6%] vs 0/158, p = 0.012). Supportive features were present in 230 of 257 (89%) patients, regardless of age, MOG-IgG titers, and core syndromes except for optic neuritis in adults whose assessment with orbital MRI was not systematic. Overall, 240 of 257 (94%) patients were well classified by the MOGAD criteria (e.g., 236 eventually having MOGAD and 4 alternative diagnoses), and 17 were wrongly classified (e.g., 11 eventually having MOGAD and 6 alternative diagnoses). Although the criteria classified better during disease attacks than during remissions (187 [96%] vs 49 [89%] serum MOG-IgG-positive patients were well-classified, p = 0.038), the PPV was high in both settings (99% [95% CI 97-100] vs 98% [95% CI 89-100]). DISCUSSION: The 2023 MOGAD criteria correctly identified most children and adults with MOGAD. The highest accuracy occurred when they were applied during disease attacks. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that the 2023 MOGAD criteria accurately identify adults and children with MOGAD.

Searching for Neuronal Antibodies in Psychiatric Diseases: Uncertain Findings and Implications.

In recent years, neurology and psychiatry journals have been inundated with reports on individual symptoms of autoimmune encephalitis (AE) that are described as distinct entities such as autoimmune psychosis, obsessive-compulsive disorders, or depression. It is unquestionable that for AE the demonstration of antibodies against neuronal-surface proteins is intrinsically linked to distinct disorders (some defining new diseases) that are usually treatment-responsive and associate with comorbidities that vary according to the antigen. By contrast, for psychiatric diseases, the apparent detection of antibodies has not defined any disorder or affected the diagnosis and treatment of patients. Although these studies frequently use anti-N-methyl-D-aspartate receptor encephalitis to rationalize the findings, they rarely adopt the same rigorous investigations or address the clinical and pathogenic significance of the antibodies or discuss the limitations related to the biological sample or antibody-testing techniques. It is imperative to consider (1) some antibodies (GAD65, TPO) occur in serum of 8%-13% of healthy people; (2) VGKC antibodies are not useful unless LGI1 or CASPR2 are investigated; (3) commercial-clinical testing for Ma2, Zic4, and SOX1 antibodies causes a high number of false-positive results; (4) GlyR antibodies have unclear disease specificity when examined only in serum; and (5) the significance of antibodies against unknown antigens of endothelium, astrocytes, myelin fibers, or granule cells of hippocampus and cerebellum is questioned by the lack of disease specificity and appropriate controls. These limitations and problems are a frequent cause of neurologic consultations. Here we discuss some of these problems, emphasizing the importance of clinical judgment over antibody findings.

mRNA COVID-19 Vaccination Does Not Exacerbate Symptoms or Trigger Neural Antibody Responses in Multiple Sclerosis.

BACKGROUND AND OBJECTIVE: In people with multiple sclerosis (pwMS), concern for potential disease exacerbation or triggering of other autoimmune disorders contributes to vaccine hesitancy. We assessed the humoral and T-cell responses to SARS-CoV-2 after mRNA vaccination, changes in disease activity, and development of antibodies against central or peripheral nervous system antigens. METHODS: This was a prospective 1-year longitudinal observational study of pwMS and a control group of patients with other inflammatory neurologic disorders (OIND) who received an mRNA vaccine. Blood samples were obtained before the first dose (T1), 1 month after the first dose (T2), 1 month after the second dose (T3), and 6 (T4), 9 (T5), and 12 (T6) months after the first dose. Patients were assessed for the immune-specific response, annualized relapse rate (ARR), and antibodies to onconeuronal, neural surface, glial, ganglioside, and nodo-paranodal antigens. RESULTS: Among 454 patients studied, 390 had MS (22 adolescents) and 64 OIND; the mean (SD) age was 44 (14) years; 315 (69%) were female; and 392 (87%) were on disease-modifying therapies. Antibodies to the receptor-binding domain were detected in 367 (86%) patients at T3 and 276 (83%) at T4. After a third dose, only 13 (22%) of 60 seronegative patients seroconverted, and 255 (92%) remained seropositive at T6. Cellular responses were present in 381 (93%) patients at T3 and in 235 (91%) patients at T6 including all those receiving anti-CD20 therapies and in 79% of patients receiving fingolimod. At T3 (429 patients) or T6 (395 patients), none of the patients had developed CNS autoantibodies. Seven patients had neural antibodies that were already present before immunization (3 adult patients with MS had MOG-IgG, 2 with MG and 1 with MS had neuronal cell surface antibodies [unknown antigen], and 1 with MS had myelin antibody reactivity [unknown antigen]. Similarly, no antibodies against PNS antigens were identified at T3 (427 patients). ARR was lower in MS and not significantly different in patients with OIND. Although 182 (40%) patients developed SARS-CoV-2 infection, no cases of severe COVID-19 or serious adverse events occurred. DISCUSSION: In this study, mRNA COVID-19 vaccination was safe and did not exacerbate the autoimmune disease nor triggered neural autoantibodies or immune-mediated neurologic disorders. The outcome of patients who developed SARS-CoV-2 infection was favorable.

The diagnosis of anti-LGI1 encephalitis varies with the type of immunodetection assay and sample examined.

Detection of Leucine-rich glioma inactivated 1 (LGI1) antibodies in patients with suspected autoimmune encephalitis is important for diagnostic confirmation and prompt implementation of immunomodulatory treatment. However, the clinical laboratory diagnosis can be challenging. Previous reports have suggested that the type of test and patient's sample (serum or CSF) have different clinical performances, however, there are no studies comparing different diagnostic tests on paired serum/CSF samples of patients with anti-LGI1 encephalitis. Here, we assessed the clinical performance of a commercial and an in house indirect immunofluorescent cell based assays (IIF-CBA) using paired serum/CSF of 70 patients with suspected anti-LGI1 encephalitis and positive rat brain indirect immunohistochemistry (IIHC). We found that all (100%) patients had CSF antibodies when the in house IIF-CBA was used, but only 88 (83%) were positive if the commercial test was used. In contrast, sera positivity rate was higher with the commercial test (94%) than with the in house assay (86%). If both serum and CSF were examined with the commercial IIFA-CBA, 69/70 (98.5%) patients were positive in at least one of the samples. These findings are clinically important for centers in which rat brain IIHC and in house IIFA-CBA are not available. Moreover, the observation that all patients with anti-LGI1 encephalitis have antibodies in CSF is in line with the concept that these antibodies are pathogenic.

CSF Biomarkers in COVID-19 Associated Encephalopathy and Encephalitis Predict Long-Term Outcome.

Patients with coronavirus disease 2019 (COVID-19) frequently develop acute encephalopathy and encephalitis, but whether these complications are the result from viral-induced cytokine storm syndrome or anti-neural autoimmunity is still unclear. In this study, we aimed to evaluate the diagnostic and prognostic role of CSF and serum biomarkers of inflammation (a wide array of cytokines, antibodies against neural antigens, and IgG oligoclonal bands), and neuroaxonal damage (14-3-3 protein and neurofilament light [NfL]) in patients with acute COVID-19 and associated neurologic manifestations (neuro-COVID). We prospectively included 60 hospitalized neuro-COVID patients, 25 (42%) of them with encephalopathy and 14 (23%) with encephalitis, and followed them for 18 months. We found that, compared to healthy controls (HC), neuro-COVID patients presented elevated levels of IL-18, IL-6, and IL-8 in both serum and CSF. MCP1 was elevated only in CSF, while IL-10, IL-1RA, IP-10, MIG and NfL were increased only in serum. Patients with COVID-associated encephalitis or encephalopathy had distinct serum and CSF cytokine profiles compared with HC, but no differences were found when both clinical groups were compared to each other. Antibodies against neural antigens were negative in both groups. While the levels of neuroaxonal damage markers, 14-3-3 and NfL, and the proinflammatory cytokines IL-18, IL-1RA and IL-8 significantly associated with acute COVID-19 severity, only the levels of 14-3-3 and NfL in CSF significantly correlated with the degree of neurologic disability in the daily activities at 18 months follow-up. Thus, the inflammatory process promoted by SARS-CoV-2 infection might include blood-brain barrier disruption in patients with neurological involvement. In conclusion, the fact that the levels of pro-inflammatory cytokines do not predict the long-term functional outcome suggests that the prognosis is more related to neuronal damage than to the acute neuroinflammatory process.

Neurofilament Light Chain Levels in Anti-NMDAR Encephalitis and Primary Psychiatric Psychosis.

BACKGROUND AND OBJECTIVES: An important challenge in diagnosing anti-NMDA receptor (NMDAR) encephalitis (NMDARe) is differentiating it from a first episode of psychosis (FEP) caused by a psychiatric disease (pFEP). CSF antibody testing distinguishes these diseases, but spinal taps are difficult to obtain in psychiatric facilities. A separate problem is the lack of biomarkers of NMDARe severity and outcome. Here we assessed the performance of neurofilament light chain (NfL) testing in these settings. METHODS: In this observational study, NfL levels were determined with single-molecule array in patients with NMDARe, pFEP, herpes simplex encephalitis (HSE), and healthy participants (HC), with the last 2 groups used as controls. Receiver operating characteristic (ROC) analyses were performed to assess the prediction accuracy of serum NfL (sNfL) levels for NMDARe and pFEP and to obtain clinically useful cutoffs. RESULTS: One hundred eighteen patients with NMDARe (33 with isolated psychosis at presentation), 45 with pFEP, 36 with HSE, and 36 HC were studied. Patients with NMDARe with seizures/status epilepticus, intensive care unit admission, and CSF pleocytosis (>20 white blood cells/µL) and without early immunotherapy were more likely to have higher NfL (mainly in CSF) than individuals with NMDARe without these features. NfL levels at diagnosis of NMDARe did not correlate with outcome at 1-year follow-up assessed with the modified Rankin Scale. Patients with NMDARe had significantly higher sNfL than individuals with pFEP and HC and lower sNfL than patients with HSE. ROC analysis of sNfL between NMDARe with isolated psychosis and pFEP provided an area under the curve of 0.93 (95% CI 0.87-0.99) and an sNfL cutoff ≥15 pg/mL to distinguish these disorders (sensitivity 85%, specificity 96%, positive likelihood ratio 19.3). Forty-three of 45 (96%) patients with pFEP had sNfL<15 pg/mL, whereas only 5 of 33 (15%) with NMDARe with isolated psychosis were below this cutoff (risk estimation NMDARe vs pFEP: odds ratio 120.4 [95% CI 21.8-664], p < 0.001). None of the patients with HSE and 35 of 36 (97%) HC had sNfL<15 pg/mL. DISCUSSION: NfL measured at diagnosis of NMDARe associated with features of disease severity but not with long-term outcome. Young patients with FEP and sNfL ≥15 pg/mL had a 120 times higher chance of having NMDARe than those with pFEP. This cutoff correctly classified 96% of patients with pFEP and 85% of patients with NMDARe with isolated psychosis. Patients with FEP of unclear etiology and sNfL ≥15 pg/mL should undergo CSF NMDAR antibody testing.

Clinical characterisation of patients in the post-acute stage of anti-NMDA receptor encephalitis: a prospective cohort study and comparison with patients with schizophrenia spectrum disorders.

BACKGROUND: Anti-NMDA receptor (NMDAR) encephalitis is associated with a post-acute stage that is not well known. We aimed to describe the clinical features of this stage, similarities with schizophrenia spectrum disorders, and the factors that predict cognitive-psychiatric outcomes and could serve as prognostic biomarkers. METHODS: In this prospective cohort study, participants (aged 12-60 years) with anti-NMDAR encephalitis during the post-acute stage visited Hospital Clínic de Barcelona (Barcelona, Spain) on three occasions (at study entry [V1], at 6 months [V2], and at 12 months [V3]) and underwent comprehensive neuropsychiatric evaluations. Similar evaluations were done in a group of age-matched participants with schizophrenia spectrum disorders and a group of age-matched and sex-matched healthy participants also recruited from Hospital Clínic de Barcelona. We analysed differences between and within groups in the longitudinal follow-up using multilevel linear mixed-effect models, adjusting for group, age, sex, and socioeconomic status to control for possible confounding. FINDINGS: Between Jan 1, 2017, and Sept 30, 2020, 82 participants were recruited, 28 (34%) with anti-NMDAR encephalitis, 27 (33%) with schizophrenia spectrum disorders, and 27 (33%) healthy participants. Although, by V1 (median 4 months [IQR 3-7] from disease onset), many acute-stage symptoms in participants with anti-NMDAR encephalitis had resolved (acute stage median modified Rankin Scale [mRS] score 5 [IQR 4-5] vs V1 mRS score 2 [1-2]; p<0·0001), 25 (89%) participants showed deficits in at least one cognitive domain. In this group, 15 (68%) of 22 cognitive domain variables were impaired at V1, whereas only eight (36%) were altered at V3 (p=0·016). In participants with schizophrenia spectrum disorders, 11 (50%) of 22 variables (all shared with participants with anti-NMDAR encephalitis) were impaired at V1, without changes at V3. Two acute-stage features of anti-NMDAR encephalitis (ie, decreased consciousness and no improvement within the first 4 weeks of treatment) predicted cognitive domain outcomes, and a visuospatial task (ie, serial biases) at V1 showed potential in predicting learning and memory outcomes. At V1, all psychiatric symptom clusters were similarly altered in participants with anti-NMDAR encephalitis and in those with schizophrenia spectrum disorders, but only those in individuals with anti-NMDAR encephalitis subsequently improved (p=0·031). The greatest cognitive-psychiatric improvement in participants with anti-NMDAR encephalitis occurred between V1 and V2. During this interval, four (14%) participants with anti-NMDAR encephalitis would have met the diagnostic criteria of schizophrenia if CSF antibody findings had not been investigated. INTERPRETATION: The cognitive-psychiatric symptoms of anti-NMDAR encephalitis in the post-acute stage resembled those of stabilised schizophrenia, but only those in participants with anti-NMDAR encephalitis progressively improved, predominantly during V1-V2. These findings are important for clinical trials on anti-NMDAR encephalitis and suggest that prompt cognitive-psychosocial rehabilitation might be a valuable intervention. FUNDING: Instituto Salud Carlos III, NEURON Network of European Funding for Neuroscience Research, National Alliance for Research in Schizophrenia and Affective Disorders, and la Caixa Health-Research Foundation.

Limitations of a Commercial Assay as Diagnostic Test of Autoimmune Encephalitis.

Detection of neuronal surface antibodies (NSAb) is important for the diagnosis of autoimmune encephalitis (AE). Although most clinical laboratories use a commercial diagnostic kit (Euroimmun, Lübeck, Germany) based on indirect immunofluorescence on transfected cells (IIFA), clinical experience suggests diagnostic limitations. Here, we assessed the performance of the commercial IIFA in serum and CSF samples of patients with suspected AE previously examined by rat brain immunohistochemistry (Cohort A). Of 6213 samples, 404 (6.5%) showed brain immunostaining suggestive of NSAb: 163 (40%) were positive by commercial IIFA and 241 (60%) were negative. When these 241 samples were re-assessed with in-house IIFA, 42 (18%) were positive: 21 (9%) had NSAb against antigens not included in the commercial IIFA and the other 21 (9%) had NSAb against antigens included in the commercial kit (false negative results). False negative results occurred more frequently with CSF (29% vs 10% in serum) and predominantly affected GABABR (39%), LGI1 (17%) and AMPAR (11%) antibodies. Results were reproduced in a separate cohort (B) of 54 AE patients with LGI1, GABABR or AMPAR antibodies in CSF which were missed in 30% by commercial IIFA. Patients with discordant GABABR antibody results (positive in-house but negative commercial IIFA) were less likely to develop full-blown clinical syndrome; no significant clinical differences were noted for the other antibodies. Overall, NSAb testing by commercial IIFA led to false negative results in a substantial number of patients, mainly those affected by anti-LG1, GABABR or AMPAR encephalitis. If these disorders are suspected and commercial IIFA is negative, more comprehensive antibody studies are recommended.

Absence of GluD2 Antibodies in Patients With Opsoclonus-Myoclonus Syndrome.

OBJECTIVE: A recent study showed glutamate receptor delta 2 antibodies (GluD2-ab) in sera of patients with opsoclonus-myoclonus syndrome (OMS). Inconsistencies between cerebellar immunoreactivity and expression of GluD2 led us to hypothesize that these antibodies are not biomarkers of OMS. METHODS: Serum of 45 children with OMS (10 [22%] with neuroblastoma), 158 adults with OMS (53 [34%] with tumors), and 172 controls including 134 patients with several types of neurologic disorders, 18 with neuroblastoma without OMS, and 20 healthy participants were investigated. Antibodies were determined with 3 different techniques: (1) rat brain immunohistochemistry, (2) a live cell-based assay using a standard secondary antibody (2-step CBA), and (3) a similar CBA with a secondary and tertiary antibodies (3-step CBA). Two plasmids were used in the CBA studies. Three commercial GluD2-ab and 2 human sera with GluD2-ab served as controls for expression of GluD2. RESULTS: The 3 commercial GluD2-ab showed predominant reactivity with the molecular and Purkinje cell layers (where GluD2 is highly enriched), and were also positive with the indicated CBAs. Substantially milder reactivity with brain tissue and CBA was obtained with the 2 control human sera containing GluD2-ab. None of the 203 patients with OMS and 172 controls showed immunoreactivities consistent with GluD2-abs. Compared with a standard 2-step CBA, the 3-step assay did not improve antibody detection and showed more frequent nonspecific reactivity that was not immunoabsorbed with GluD2. CONCLUSION: We did not find GluD2-ab in a large cohort of patients with OMS. GluD2-ab should not be considered diagnostic biomarkers of OMS.

No Effects of Meteorological Factors on the SARS-CoV-2 Infection Fatality Rate.

OBJECTIVE: Previous studies have shown that meteorological factors may increase COVID-19 mortality, likely due to the increased transmission of the virus. However, this could also be related to an increased infection fatality rate (IFR). We investigated the association between meteorological factors (temperature, humidity, solar irradiance, pressure, wind, precipitation, cloud coverage) and IFR across Spanish provinces ( n = 52) during the first wave of the pandemic (weeks 10-16 of 2020). METHODS: We estimated IFR as excess deaths (the gap between observed and expected deaths, considering COVID-19-unrelated deaths prevented by lockdown measures) divided by the number of infections (SARS-CoV-2 seropositive individuals plus excess deaths) and conducted Spearman correlations between meteorological factors and IFR across the provinces. RESULTS: We estimated 2,418,250 infections and 43,237 deaths. The IFR was 0.03% in < 50-year-old, 0.22% in 50-59-year-old, 0.9% in 60-69-year-old, 3.3% in 70-79-year-old, 12.6% in 80-89-year-old, and 26.5% in ≥ 90-year-old. We did not find statistically significant relationships between meteorological factors and adjusted IFR. However, we found strong relationships between low temperature and unadjusted IFR, likely due to Spain's colder provinces' aging population. CONCLUSION: The association between meteorological factors and adjusted COVID-19 IFR is unclear. Neglecting age differences or ignoring COVID-19-unrelated deaths may severely bias COVID-19 epidemiological analyses.

Cycloid psychosis as a psychiatric expression of anti-NMDAR encephalitis. A systematic review of case reports accomplished with the authors' cooperation.

OBJECTIVE: We reviewed the psychotic symptoms of anti-NMDA receptor encephalitis (NMDARE) to differentiate its presentation from those found in a primary psychiatric disorder. We hypothesized that the cycloid psychosis (CP) phenotype would be a frequent clinical presentation in the psychiatric phase of NMDARE. METHOD: A systematic literature review in PubMed of all case reports published on NMDARE was performed from database inception to March 2020. We included all cases where psychotic symptoms were reported and whose diagnoses were confirmed by the presence of anti-NMDAR antibodies in the cerebrospinal fluid (CSF). An email including a short test (CP phenotype, Perris and Brockington's criteria) was sent to all case report authors asking them to describe the psychotic symptoms. RESULTS: We identified 335 case reports fulfilling our criteria, and the authors of 200 replied. Our analyses were based exclusively on those answers and data extracted from the articles. Median patient age was 25 years (+-11.4), 81% were female, and 39% had an ovarian teratoma. A complete CP phenotype was identified in 175 patients (87%). These were acute psychotic episodes with a sudden onset and a fluctuating clinical pattern mostly characterized by confusion (97%), delusions (75%), hallucinations (69%), motility disturbances (87%), and mood oscillations (80%). CONCLUSION: The complete CP phenotype was frequently the expression of psychotic symptoms in NMDARE. We suggest that patients with a first psychotic episode who initially exhibit the CP phenotype should undergo CSF analysis to determine whether antibodies against neuronal cell surface or synaptic receptors are present to rule out a possible diagnosis of autoimmune encephalitis.