Kappa index in the diagnostic work-up of autoimmune encephalitis.

BACKGROUND: The 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. METHODS: Charts 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. RESULTS: We 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. CONCLUSIONS: The 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.

New insights into neuropathology and pathogenesis of autoimmune glial fibrillary acidic protein meningoencephalomyelitis.

Anti-glial fibrillary acidic protein (GFAP) meningoencephalomyelitis (autoimmune GFAP astrocytopathy) is a new autoimmune central nervous system (CNS) disease diagnosable by the presence of anti-GFAP autoantibodies in the cerebrospinal fluid and presents as meningoencephalomyelitis in the majority of patients. Only few neuropathological reports are available and little is known about the pathogenic mechanisms. We performed a histopathological study of two autopsies and nine CNS biopsies of patients with anti-GFAP autoantibodies and found predominantly a lymphocytic and in one autopsy case a granulomatous inflammatory phenotype. Inflammatory infiltrates were composed of B and T cells, including tissue-resident memory T cells. Although obvious astrocytic damage was absent in the GFAP-staining, we found cytotoxic T cell-mediated reactions reflected by the presence of CD8+/perforin+/granzyme A/B+ cells, polarized towards astrocytes. MHC-class-I was upregulated in reactive astrocytes of all biopsies and two autopsies but not in healthy controls. Importantly, we observed a prominent immunoreactivity of astrocytes with the complement factor C4d. Finally, we provided insight into an early phase of GFAP autoimmunity in an autopsy of a pug dog encephalitis that was characterized by marked meningoencephalitis with selective astrocytic damage with loss of GFAP and AQP4 in the lesions.Our histopathological findings indicate that a cytotoxic T cell-mediated immune reaction is present in GFAP autoimmunity. Complement C4d deposition on astrocytes could either represent the cause or consequence of astrocytic reactivity. Selective astrocytic damage is prominent in the early phase of GFAP autoimmunity in a canine autopsy case, but mild or absent in subacute and chronic stages in human disease, probably due to the high regeneration potential of astrocytes. The lymphocytic and granulomatous phenotypes might reflect different stages of lesion development or patient-specific modifications of the immune response. Future studies will be necessary to investigate possible implications of pathological subtypes for clinical disease course and therapeutic strategies.

Increased Intrathecal B and Plasma Cells in Patients With Anti-IgLON5 Disease: A Case Series.

BACKGROUND AND OBJECTIVES: Despite detection of autoantibodies, anti-IgLON5 disease was historically considered a tau-associated neurodegenerative disease, with limited treatment options and detrimental consequences for the patients. Observations in increasing case numbers hint toward underlying inflammatory mechanisms that, early detection provided, open a valuable window of opportunity for therapeutic intervention. We aimed to further substantiate this view by studying the CSF of patients with anti-IgLON5. METHODS: We identified 11 patients with anti-IgLON5 from our database and compared clinical, MRI, and CSF findings with a cohort of 20 patients with progressive supranuclear palsy (PSP) (as a noninflammatory tauopathy) and 22 patients with functional neurologic disorder. RESULTS: Patients with anti-IgLON5 show inflammatory changes in routine CSF analysis, an increase in B-lymphocyte frequency, and the presence of plasma cells in comparison to the PSP-control group and functional neurologic disease controls. Patients with intrathecal plasma cells showed a clinical response to rituximab. DISCUSSION: Our findings indicate the importance of inflammatory mechanisms, in particular in early and acute anti-IgLON5 cases, which may support the use of immune-suppressive treatments in these cases. The main limitation of the study is the small number of cases due to the rarity of the disease.

Cerebrospinal fluid neopterin as a biomarker of treatment response to Janus kinase inhibition in Aicardi-Goutières syndrome.

Janus kinase (JAK) 1 inhibition represents a precision medicine approach in the treatment of Aicardi-Goutières syndrome (AGS), through targeting of type I interferon-mediated cell signalling. Blood interferon mRNAseq has been proposed as a biomarker of disease with utility in therapeutic monitoring. Objective cerebrospinal fluid (CSF) biomarkers tracking treatment efficacy are currently lacking. Here, we report a retrospective case series of 13 patients (median age 6y, range 2y 6mo-17y; five females, eight males) with AGS demonstrating significantly elevated CSF neopterin levels at first sampling (median 200nmol/L, range 45-2024nmol/L), compared to 13 age-matched controls with non-inflammatory neurological conditions (median 23nmol/L, range 5-34nmol/L, p<0.001). Five patients with AGS treated with JAK inhibitors demonstrated a median 81.5% reduction of CSF neopterin (range -36% to -88% change from baseline), compared to eight untreated patients with AGS demonstrating a median 7% reduction in CSF neopterin (range -63% to +117% change) (p=0.047). Our data indicate a biological effect of JAK inhibitors, and the potential role of CSF neopterin as a biomarker of treatment response.

Α case of seronegative autoimmune encephalitis associated with human herpesvirus-7 (HHV-7).

In the last 10 years, an increased number of patients presenting with acute encephalitis is being observed, a finding that is attributed to autoimmune mechanisms. Despite the fact that autoantibodies usually target the neuronal cell surface or synaptic proteins in the central nervous system (CNS), in many cases these remain undetectable, constituting a future diagnostic and therapeutic challenge. Human herpesvirus-7 (HHV-7) is proven to be a neurotropic virus, causing various neurological complications mostly in the adult population. We present the case of a 10-year-old girl, with confirmed active HHV-7 infection of the CNS, who developed acute seronegative autoimmune encephalitis. To our best knowledge, there is no literature concerning pediatric cases of autoimmune encephalitis following HHV-7 infection.

Autoimmune Glial Fibrillary Acidic Protein Astrocytopathy in Children: A Retrospective Analysis of 35 Cases.

Objective: To analyze the clinical manifestations, imaging, electroencephalography, treatment, and prognosis of 35 cases of autoimmune glial fibrillary acidic protein astrocytopathy (GFAP-A) in children. Methods: Children hospitalized in the Department of Neurology, Hunan Children's Hospital, China, between January 2015 and June 2021, owing to autoimmune diseases of the central nervous system were subjected to a cell-based assay (CBA). The assay identified 40 children positive for GFAP-immunoglobulin (Ig)G antibodies in the serum and/or the cerebrospinal fluid. Based on clinical manifestations and imaging characteristics, five children who were only positive for GFAP-IgG antibodies in serum were excluded, and the remaining 35 children were diagnosed with autoimmune GFAP-A. The clinical data derived from the 35 children were retrospectively analyzed. Results: A total of 35 children, including 23 males and 12 females with a mean age of 6.3 ± 0.6 years, manifested clinical symptoms of fever (62.9%), headache (42.9%), convulsions (42.9%), abnormal mental behavior (51.4%), disorders of consciousness (54.3%), visual disturbance (22.9%), ataxia (11.4%), paralysis (40%), and autonomic dysfunction (25.7%). One child exhibited only the clinical symptom of peripheral facial nerve palsy. Eleven out of 35 children were also positive for other antibodies. In addition to the common overlapping autoimmune syndromes, one case of autoimmune GFAP-A also manifested as Bickerstaff's brainstem encephalitis. Linear periventricular enhancement upon MRI was significantly less frequent in children (8.5%) than in adults. In pediatric patients, MRI contrast enhancement was principally seen in the meninges and brain lobes. Although repeated relapse (17.1%) and sequelae symptoms (20%) occurred in some cases, most children showed a favorable prognosis. Spearman's rank correlation showed that the antibody titer was not significantly associated with the severity of the initial disease conditions. Conclusions: The disease diagnosis in children seropositive for GFAP antibodies only should receive a comprehensive diagnosis based on their clinical symptoms, imaging, electroencephalographic characteristics, and treatment responses. Some patients with relapses should receive repeated gamma globulin and corticosteroid therapy or the addition of immunosuppressants to their therapeutic regimen, and slow-dose tapering of corticosteroids and extended treatment are recommended for patients with overlapping autoimmune syndromes.

The changing spectrum of antibody-mediated encephalitis in China.

In the past 5 years, the positivity rate of autoimmune encephalitis antibody panels has significantly decreased in patients with clinically suspected encephalitis in an encephalitis center in China. Furthermore, the spectrum of patients with autoantibodies related to autoimmune encephalitis has changed significantly, exhibiting a decreased percentage of patients with anti-N-methyl-d-aspartate receptor antibodies and an increased percentage of patients with infrequently observed autoantibodies. Meanwhile, a small but non-negligible proportion of patients with autoantibodies against cell surface and synaptic proteins exhibited positivity for more than one autoantibody.

Autoimmune glial fibrillary acidic protein astrocytopathy resembling isolated central nervous system lymphomatoid granulomatosis.

We report two patients with meningoencephalomyelitis without evidence of extra central nervous system (CNS) involvement. Brain MRI showed linear perivascular radial gadolinium enhancement patterns and spinal cord MRI showed longitudinal extensive T2-hyperintensity lesions. Pathological findings from brain biopsies were angiocentric T-cell predominant lymphoid infiltrates that lacked Epstein-Barr virus-positive atypical B cells. The patients were initially suspected to have isolated CNS-lymphomatoid granulomatosis (LYG). Thereafter, glial fibrillary acidic protein (GFAP)-immunoglobulin G were detected in their cerebrospinal fluid. This finding suggested autoimmune GFAP astrocytopathy. We speculate there is a link between isolated CNS-LYG and autoimmune GFAP astrocytopathy.

CSF Findings in Acute NMDAR and LGI1 Antibody-Associated Autoimmune Encephalitis.

BACKGROUND AND OBJECTIVES: CSF in antibody-defined autoimmune encephalitis (AE) subtypes shows subtype-dependent degrees of inflammation ranging from rare and often mild to frequent and often robust. AEs with NMDA receptor antibodies (NMDAR-E) and leucine-rich glioma-inactivated protein 1 antibodies (LGI1-E) represent opposite ends of this spectrum: NMDAR-E with typically frequent/robust and LGI1-E with rare/mild CSF inflammation. For a more in-depth analysis, we characterized CSF findings in acute, therapy-naive NMDAR-E and LGI1-E in a multicentric, retrospective, cross-sectional setting. METHODS: Eighty-two patients with NMDAR-E and 36 patients with LGI1-E from the GErman NEtwork for Research of AuToimmune Encephalitis (GENERATE) with lumbar puncture within 90 days of onset and before immunotherapy were included. CSF parameters comprised leukocytes, oligoclonal bands (OCBs), and CSF/serum ratios for albumin, immunoglobulin G (IgG), A (IgA), and M (IgM), the latter 3 converted to Z scores according to Reiber formulas. The MRZ reaction was tested in 14 patients with NMDAR-E and 6 patients with LGI1-E, respectively. RESULTS: CSF was abnormal in 94% of NMDAR-E but only in 36% of LGI1-E patients. Robust quantitative intrathecal immunoglobulin synthesis (IIS, IgG > IgM >> IgA) was characteristic for NMDAR-E, but absent in LGI-E. In NMDAR-E, CSF leukocytes were higher when IIS was present or more pronounced. In addition, in NMDAR-E, CSF leukocytes were lower and IIS occurred less often and if so to a lesser degree at older age. Patients with NMDAR-E with severe functional impairment more often had positive OCBs. In CSF obtained later than 3 weeks of onset, leukocytes were lower. In parallel, the correlation of leukocytes with IIS disappeared as IIS was partially independent of disease duration. The MRZ reaction was positive in 5 (36%) patients with NMDAR-E. All these associations were completely absent in LGI1-E. Here, younger patients showed more blood-CSF barrier dysfunction. In LGI1-E, but not in NMDAR-E, the blood-CSF barrier was more dysfunctional when CSF leukocytes were higher. DISCUSSION: NMDAR-E and LGI-E differ in their typical extent of CSF inflammation. In addition, the patterns formed by the different inflammatory CSF parameters and their relationship with disease severity, age, and disease duration are subtype-characteristic. Moreover, signs for multiple sclerosis-like chronic inflammation are present in a subgroup of patients with NMDAR-E. These CSF patterns might be markers for the different immunopathogeneses of LGI1-E and NMDAR-E.

Autoimmune GFAP astrocytopathy presenting with remarkable CNS hyperexcitability and oculogyric crises.

The autoimmune GFAP astrocytopathy has been associated with meningoencephalomyelitis that usually responds to glucocorticoids. We report a 20-year-old man that developed an acute and severe meningoencephalomyelitis with remarkable CNS hyperexcitability and oculogyric crises. CSF analysis showed hypoglycorrhachia, pleocytosis, elevated ADA, and CSF-immunofluorescence characteristic of autoimmune GFAP astrocytopathy. MRI showed lesions at thalamus, corpus-callosum, dorsal pons and dentate nucleus with associated myelitis. Immunotherapy led to a full recovery, although MRI activity was observed at follow-up. CNS hyperexcitability, typically seen in other immune-mediated syndromes, represents a novel presenting form to be included as part of the clinical spectrum of this entity.

Intrathecal Antibody Production Against Epstein-Barr, Herpes Simplex, and Other Neurotropic Viruses in Autoimmune Encephalitis.

BACKGROUND AND OBJECTIVES: Neurotropic viruses are suspected to play a role in the pathogenesis of autoimmune diseases of the CNS such as the association between the Epstein-Barr virus (EBV) and multiple sclerosis (MS). A group of autoimmune encephalitis (AE) is linked to antibodies against neuronal cell surface proteins. Because CNS infection with the herpes simplex virus can trigger anti-NMDA receptor (NMDAR) encephalitis, a similar mechanism for EBV and other neurotropic viruses could be postulated. To investigate for previous viral infections of the CNS, intrathecally produced virus-specific antibody synthesis was determined in patients with AE. METHODS: Antibody-specific indices (AIs) against EBV and measles, rubella, varicella zoster, herpes simplex virus, and cytomegalovirus were determined in 27 patients having AE (anti-NMDAR encephalitis, n = 21, and LGI1 encephalitis, n = 6) and in 2 control groups comprising of 30 patients with MS and 21 patients with noninflammatory CNS diseases (NIND), which were sex and age matched. RESULTS: An intrathecal synthesis of antibodies against EBV was found in 5/27 (19%) patients with AE and 2/30 (7%) of the patients with MS. All these patients had also at least 1 additional elevated virus-specific AI. In contrast, in none of the patients with NIND, an elevated virus-specific AI was detected. DISCUSSION: Intrathecally produced antibodies against EBV can be found in patients with AE and MS but only together with antibodies against different neurotropic viruses. Evidence of these antibodies is the result of a polyspecific immune response similar yet distinct from MS response rather than an elapsed infection of the CNS.

Argonaute Autoantibodies as Biomarkers in Autoimmune Neurologic Diseases.

OBJECTIVE: To identify and characterize autoantibodies (Abs) as novel biomarkers for an autoimmune context in patients with central and peripheral neurologic diseases. METHODS: Two distinct approaches (immunoprecipitation/mass spectrometry-based proteomics and protein microarrays) and patients' sera and CSF were used. The specificity of the identified target was confirmed by cell-based assay (CBA) in 856 control samples. RESULTS: Using the 2 methods as well as sera and CSF of patients with central and peripheral neurologic involvement, we identified Abs against the family of Argonaute proteins (mainly AGO1 and AGO2), which were already reported in systemic autoimmunity. AGO-Abs were mostly of immunoglobulin G 1 subclass and conformation dependent. Using CBA, AGO-Abs were detected in 21 patients with a high suspicion of autoimmune neurologic diseases (71.4% were women; median age 57 years) and only in 4/856 (0.5%) controls analyzed by CBA (1 diagnosed with small-cell lung cancer and the other 3 with Sjögren syndrome). Among the 21 neurologic patients identified, the main clinical presentations were sensory neuronopathy (8/21, 38.1%) and limbic encephalitis (6/21, 28.6%). Fourteen patients (66.7%) had autoimmune comorbidities and/or co-occurring Abs, whereas AGO-Abs were the only autoimmune biomarker for the remaining 7/21 (33.3%). Thirteen (61.9%) patients were treated with immunotherapy; 8/13 (61.5%) improved, and 3/13 (23.1%) remained stable, suggesting an efficacy of these treatments. CONCLUSIONS: AGO-Abs might be potential biomarkers of autoimmunity in patients with central and peripheral nonparaneoplastic neurologic diseases. In 7 patients, AGO-Abs were the only biomarkers; thus, their identification may be useful to suspect the autoimmune character of the neurologic disorder. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that AGO-Abs are more frequent in patients with autoimmune neurologic diseases than controls.

Opsoclonus-myoclonus in Aicardi-Goutières syndrome.

Aicardi-Goutières syndrome (AGS) is a rare genetic neuroinflammatory disorder caused by abnormal upregulation of type 1 interferon signalling. Opsoclonus-myoclonus syndrome is a rare autoimmune phenotype demonstrating a disturbance in the humoral immune response mostly seen in the context of paraneoplastic or postinfectious states, although its pathophysiology is incompletely understood. We report the first three children described with AGS demonstrating transient opsoclonus and myoclonus after irritability and/or developmental regression, suggesting a pathological association. We describe the presentation, clinical features, progress, cerebrospinal fluid (CSF) inflammatory markers, electroencephalogram (EEG), and magnetic resonance imaging (MRI) findings in these children. Two patients had developmental regression but demonstrated a positive response to JAK1/2 inhibition clinically and on serial examination of CSF inflammatory markers. These findings suggest that AGS should be considered in children presenting with opsoclonus-myoclonus, and that the association between AGS and opsoclonus-myoclonus further supports the role of immune dysregulation as causal in the rare neurological phenomenon opsoclonus and myoclonus. What this paper adds There is a phenotypic association between opsoclonus-myoclonus syndrome and Aicardi-Goutières syndrome. There is clinical evidence of immune dysregulation in the pathogenesis of opsoclonus and myoclonus.

Cerebrospinal Fluid IL-17A Could Predict Acute Disease Severity in Non-NMDA-Receptor Autoimmune Encephalitis.

Introduction: Most of our knowledge into autoimmune encephalitis (AE) comes from N-Methyl-D-Aspartate Receptor (NMDAR) encephalitis. The concentrations of cytokines in cerebrospinal fluid (CSF) including IL-17A have been found to be increased and associated with poor outcome. However, data on the cytokine concentration in CSF and its correlation with outcome is lacking for other types of AE. Objective: To report the concentrations of CSF sIL-2R, IL-6, IL-8, IL-10 and IL-17A and to correlate it with acute disease severity and the 1-year outcome in non-NMDAR AE. Methods: We measured the CSF concentration of each cytokine in 20 AE patients, and compared IL-6 and IL-17A concentrations with 13 patients with CNS demyelinating diseases and 20 non-inflammatory controls. Patients were > 18yr and had at least 1-year clinical follow-up. Intracellular and NMDAR antibody (Ab) -mediated encephalitis were excluded. A mRS ≤ 2 was retained as a 1-year good outcome. Results: The IL-17A concentration in CSF was higher in AE patients than in both control groups (p<0.01). No difference was observed in CSF concentration of IL-6 between groups. At disease onset, a high CSF IL-17A concentration correlated with a high modified Rankin Scale (p<0.05), a high Clinical Assessment Scale for Autoimmune Encephalitis score (p<0.001) and ICU admission (p<0.01). There was no correlation between the concentration of all CSF cytokines and the 1-year clinical outcome. Conclusion: Our results show that CSF IL-17A could be interesting to assess initial severity in non-NMDAR AE. Thus, CSF IL-17A could be an interesting therapeutic target and be useful to assess early selective immunosuppressive therapy.

Assessing the role of a tissue-based assay in the diagnostic algorithm of autoimmune encephalitis.

Tissue-based assay (TBA) is a widely-used method to detect neural autoantibodies, but the diagnostic accuracy for autoimmune encephalitis (AE) has not yet been adequately measured. We retrospectively evaluated the sensitivity and specificity of an indirect immunofluorescence TBA (IIF-TBA) in 159 patients with suspected AE. Serum and cerebrospinal fluid (CSF) specimens were collected and tested from December 2012 to September 2020. In the paired sample analysis, serum testing showed higher sensitivity than CSF, while the latter had higher specificity. Based on these results, we clarify the advantages of using a TBA as the principal screening method for patients with suspected AE.

Prospective Quantification of CSF Biomarkers in Antibody-Mediated Encephalitis.

OBJECTIVE: To determine whether neuronal and neuroaxonal injury, neuroinflammation, and synaptic dysfunction associate with clinical course and outcomes in antibody-mediated encephalitis (AME), we measured biomarkers of these processes in CSF from patients presenting with AME and cognitively normal individuals. METHODS: Biomarkers of neuronal (total tau, VILIP-1) and neuroaxonal damage (neurofilament light chain [NfL]), inflammation (YKL-40), and synaptic function (neurogranin, SNAP-25) were measured in CSF obtained from 45 patients at the time of diagnosis of NMDA receptor (n = 34) or LGI1/CASPR2 (n = 11) AME and 39 age- and sex-similar cognitively normal individuals. The association between biomarkers and modified Rankin Scale (mRS) scores were evaluated in a subset (n = 20) of longitudinally followed patients. RESULTS: Biomarkers of neuroaxonal injury (NfL) and neuroinflammation (YKL-40) were elevated in AME cases at presentation, whereas markers of neuronal injury and synaptic function were stable (total tau) or decreased (VILIP-1, SNAP-25, neurogranin). The log-transformed ratio of YKL-40/SNAP-25 optimally discriminated patients from cognitively normal individuals (area under the receiver operating characteristic curve 0.99; 95% confidence interval 0.97, >0.99). Younger age (ρ = -0.56; p = 0.01), lower VILIP-1 (ρ = -0.60; p < 0.01) and SNAP-25 (ρ = -0.54; p = 0.01), and higher log10(YKL-40/SNAP-25) (ρ = 0.48; p = 0.04) associated with greater disease severity (higher mRS score) in prospectively followed patients. Higher YKL-40 (ρ = 0.60; p = 0.02) and neurogranin (ρ = 0.55; p = 0.03) at presentation were associated with higher mRS scores 12 months following hospital discharge. CONCLUSIONS: CSF biomarkers suggest that neuronal integrity is acutely maintained in AME, despite neuroaxonal compromise. Low levels of biomarkers of synaptic function may reflect antibody-mediated internalization of cell surface receptors and may represent an acute correlate of antibody-mediated synaptic dysfunction, with the potential to inform disease severity and outcomes.

Longitudinal CSF Findings in Autoimmune Encephalitis-A Monocentric Cohort Study.

Autoimmune encephalitis (AIE) poses a diagnostic challenge due to its heterogeneous clinical presentation, which overlaps with various neurological and psychiatric diseases. During the diagnostic work-up, cerebrospinal fluid (CSF) is routinely obtained, allowing for differential diagnostics as well as for the determination of antibody subclasses and specificities. In this monocentric cohort study, we describe initial and serial CSF findings of 33 patients diagnosed with antibody-associated AIE (LGI1 (n=8), NMDA (n=7), CASPR2 (n=3), IgLON5 (n=3), AMPAR (n=1), GAD65/67 (n=4), Yo (n=3), Ma-1/2 (n=2), CV2 (n=2)). Routine CSF parameters of 12.1% of AIE patients were in normal ranges, while 60.6% showed elevated protein levels and 45.4% had intrathecal oligoclonal bands (OCBs). Repeated CSF analyses showed a trend towards normalization of initial pathological CSF findings, while relapses were more likely to be associated with increased cell counts and total protein levels. OCB status conversion in anti-NMDARE patients coincided with clinical improvement. In summary, we show that in routine CSF analysis at diagnosis, a considerable number of patients with AIE did not exhibit alteration in the CSF and therefore, diagnosis may be delayed if antibody testing is not performed. Moreover, OCB status in anti-NMDAR AIE patients could represent a potential prognostic biomarker, however further studies are necessary to validate these exploratory findings.

Cerebrospinal fluid findings in patients with psychotic symptoms-a retrospective analysis.

In current international classification systems (ICD-10, DSM5), the diagnostic criteria for psychotic disorders (e.g. schizophrenia and schizoaffective disorder) are based on symptomatic descriptions since no unambiguous biomarkers are known to date. However, when underlying causes of psychotic symptoms, like inflammation, ischemia, or tumor affecting the neural tissue can be identified, a different classification is used ("psychotic disorder with delusions due to known physiological condition" (ICD-10: F06.2) or psychosis caused by medical factors (DSM5)). While CSF analysis still is considered optional in current diagnostic guidelines for psychotic disorders, CSF biomarkers could help to identify known physiological conditions. In this retrospective, partly descriptive analysis of 144 patients with psychotic symptoms and available CSF data, we analyzed CSF examinations' significance to differentiate patients with specific etiological factors (F06.2) from patients with schizophrenia, schizotypal, delusional, and other non-mood psychotic disorders (F2). In 40.3% of all patients, at least one CSF parameter was out of the reference range. Abnormal CSF-findings were found significantly more often in patients diagnosed with F06.2 (88.2%) as compared to patients diagnosed with F2 (23.8%, p < 0.00001). A total of 17 cases were identified as probably caused by specific etiological factors (F06.2), of which ten cases fulfilled the criteria for a probable autoimmune psychosis linked to the following autoantibodies: amphiphysin, CASPR2, CV2, LGl1, NMDA, zic4, and titin. Two cases presented with anti-thyroid tissue autoantibodies. In four cases, further probable causal factors were identified: COVID-19, a frontal intracranial tumor, multiple sclerosis (n = 2), and neurosyphilis. Twenty-one cases remained with "no reliable diagnostic classification". Age at onset of psychotic symptoms differed between patients diagnosed with F2 and F06.2 (p = 0.014), with the latter group being older (median: 44 vs. 28 years). Various CSF parameters were analyzed in an exploratory analysis, identifying pleocytosis and oligoclonal bands (OCBs) as discriminators (F06.2 vs. F2) with a high specificity of > 96% each. No group differences were found for gender, characteristics of psychotic symptoms, substance dependency, or family history. This study emphasizes the great importance of a detailed diagnostic workup in diagnosing psychotic disorders, including CSF analysis, to detect possible underlying pathologies and improve treatment decisions.

Autoimmune Epilepsy in Children: Unraveling the Mystery.

Although many neurologists are familiar with the clinical presentations of anti-N-methyl-d-aspartate receptor or limbic encephalitides, there remains much mystery surrounding autoimmune etiologies of subacute and chronic epilepsies. In addition, the subtleties and differences in presentation in the pediatric population limit diagnosis and challenge clinicians. In the absence of an acute encephalitic picture, it is likely that many clinicians do not test for autoimmune disorders due to the uncertainty surrounding the selection of appropriate candidates for testing and immunomodulation. Recent developments have expanded the definition of epilepsy related to autoimmune mechanisms. Based on current knowledge, autoimmune epilepsy can best be thought of as a subset of autoimmune encephalitis where seizures and epilepsy are the primary presenting factor. Autoimmune epilepsy has been increasingly recognized as a contributor to drug-resistant epilepsies; however, identification of affected individuals remains challenging, particularly in the pediatric population. Our understanding of autoimmune epilepsy continues to evolve as more individuals with epilepsy are tested for antibodies to neuronal proteins and as additional antibodies are being identified. This article provides an overview of the clinical features most commonly associated with positive antibody testing in epilepsy and the scales that are currently available to screen patients for antibody testing and response to immunotherapy. Literature-based recommendations are presented for the modification and validation of current scales to increase applicability to children.

Single-cell RNA-seq analysis of human CSF microglia and myeloid cells in neuroinflammation.

OBJECTIVE: To identify and characterize myeloid cell populations within the CSF of patients with MS and anti-myelin oligodendrocyte glycoprotein (MOG) disorder by high-resolution single-cell gene expression analysis. METHODS: Single-cell RNA sequencing (scRNA-seq) was used to profile individual cells of CSF and blood from 2 subjects with relapsing-remitting MS (RRMS) and one with anti-MOG disorder. Publicly available scRNA-seq data from the blood and CSF of 2 subjects with HIV were also analyzed. An informatics pipeline was used to cluster cell populations by transcriptomic profiling. Based on gene expression by CSF myeloid cells, a flow cytometry panel was devised to examine myeloid cell populations from the CSF of 11 additional subjects, including individuals with RRMS, anti-MOG disorder, and control subjects without inflammatory demyelination. RESULTS: Common myeloid populations were identified within the CSF of subjects with RRMS, anti-MOG disorder, and HIV. These included monocytes, conventional and plasmacytoid dendritic cells, and cells with a transcriptomic signature matching microglia. Microglia could be discriminated from other myeloid cell populations in the CSF by flow cytometry. CONCLUSIONS: High-resolution single-cell gene expression analysis clearly distinguishes distinct myeloid cell types present within the CSF of subjects with neuroinflammation. A population of microglia exists within the human CSF, which is detectable by surface protein expression. The function of these cells during immunity and disease requires further investigation.