Encephalitis, Mild Encephalitis, Neuroprogression, or Encephalopathy-Not Merely a Question of Terminology

Viral infections in etiology of mental disorders: a broad analysis of cytokine profile similarities - a narrative review

The recent pandemic caused by the SARS-CoV-2 virus and the associated mental health complications have renewed scholarly interest in the relationship between viral infections and the development of mental illnesses, a topic that was extensively discussed in the previous century in the context of other viruses, such as influenza. The most probable and analyzable mechanism through which viruses influence the onset of mental illnesses is the inflammation they provoke. Both infections and mental illnesses share a common characteristic: an imbalance in inflammatory factors. In this study, we sought to analyze and compare cytokine profiles in individuals infected with viruses and those suffering from mental illnesses. The objective was to determine whether specific viral diseases can increase the risk of specific mental disorders and whether this risk can be predicted based on the cytokine profile of the viral disease. To this end, we reviewed existing literature, constructed cytokine profiles for various mental and viral diseases, and conducted comparative analyses. The collected data indicate that the risk of developing a specific mental illness cannot be determined solely based on cytokine profiles. However, it was observed that the combination of IL-8 and IL-10 is frequently associated with psychotic symptoms. Therefore, to assess the risk of mental disorders in infected patients, it is imperative to consider the type of virus, the mental complications commonly associated with it, the predominant cytokines to evaluate the risk of psychotic symptoms, and additional patient-specific risk factors.

NMDAR1 autoantibodies amplify behavioral phenotypes of genetic white matter inflammation: a mild encephalitis model with neuropsychiatric relevance

Encephalitis has an estimated prevalence of ≤0.01%. Even with extensive diagnostic work-up, an infectious etiology is identified or suspected in <50% of cases, suggesting a role for etiologically unclear, noninfectious processes. Mild encephalitis runs frequently unnoticed, despite slight neuroinflammation detectable postmortem in many neuropsychiatric illnesses. A widely unexplored field in humans, though clearly documented in rodents, is genetic brain inflammation, particularly that associated with myelin abnormalities, inducing primary white matter encephalitis. We hypothesized that "autoimmune encephalitides" may result from any brain inflammation concurring with the presence of brain antigen-directed autoantibodies, e.g., against N-methyl-D-aspartate-receptor NR1 (NMDAR1-AB), which are not causal of, but may considerably shape the encephalitis phenotype. We therefore immunized young female Cnp^-/- mice lacking the structural myelin protein 2'-3'-cyclic nucleotide 3'-phosphodiesterase (Cnp) with a "cocktail" of NMDAR1 peptides. Cnp^-/- mice exhibit early low-grade inflammation of white matter tracts and blood-brain barrier disruption. Our novel mental-time-travel test disclosed that Cnp^-/- mice are compromised in what-where-when orientation, but this episodic memory readout was not further deteriorated by NMDAR1-AB. In contrast, comparing wild-type and Cnp^-/- mice without/with NMDAR1-AB regarding hippocampal learning/memory and motor balance/coordination revealed distinct stair patterns of behavioral pathology. To elucidate a potential contribution of oligodendroglial NMDAR downregulation to NMDAR1-AB effects, we generated conditional NR1 knockout mice. These mice displayed normal Morris water maze and mental-time-travel, but beam balance performance was similar to immunized Cnp^-/-. Immunohistochemistry confirmed neuroinflammation/neurodegeneration in Cnp^-/- mice, yet without add-on effect of NMDAR1-AB. To conclude, genetic brain inflammation may explain an encephalitic component underlying autoimmune conditions.

Alteration of NMDA receptor trafficking as a cellular hallmark of psychosis

A dysfunction of the glutamatergic transmission, especially of the NMDA receptor (NMDAR), constitutes one of the main biological substrate of psychotic disorders, such as schizophrenia. The NMDAR signaling hypofunction, through genetic and/or environmental insults, would cause a neurodevelopmental myriad of molecular, cellular, and network alterations that persist throughout life. Yet, the mechanisms underpinning NMDAR dysfunctions remain elusive. Here, we compared the membrane trafficking of NMDAR in three gold-standard models of schizophrenia, i.e., patient's cerebrospinal fluids, genetic manipulations of susceptibility genes, and prenatal developmental alterations. Using a combination of single nanoparticle tracking, electrophysiological, biochemical, and behavioral approaches in rodents, we identified that the NMDAR trafficking in hippocampal neurons was consistently altered in all these different models. Artificial manipulations of the NMDAR surface dynamics with competing ligands or antibody-induced receptor cross-link in the developing rat brain were sufficient to regulate the adult acoustic startle reflex and compensate for an early pathological challenge. Collectively, we show that the NMDAR trafficking is markedly altered in all clinically relevant models of psychosis, opening new avenues of therapeutical strategies.

Neurosyphilis: a series of 178 cases at the 3rd-level hospital of Marrakesh (Morocco)

Neurosyphilis (NS) is an infection of the central nervous system (CNS), caused by Treponema pallidum. Up to 4-10% of patients with untreated syphilis may develop NS which still constitutes a health challenge. The aim of this study is to analyze epidemiological, clinical, paraclinical, therapeutic, and progression profiles of NS in the south of Morocco. Authors analyzed retrospectively 178 files of patients with neurosyphilis, collected in the Neurology Department of Marrakesh over 25 years from January 1994 to March 2019. In our study, the mean age was 46 years (17-75 years). The number of males was dominant (87.6%). The most common presentation was meningoencephalitis. Four cases were atypical (late congenital syphilis, amyotrophic lateral sclerosis, neurosyphilis associated with neuro-Behcet's disease, and acute polyradiculoneuropathy). All patients had positive TPHA and VDRL serologies in blood; CSF-TPHA was positive in all patients, and CSF-VDRL was positive in 64.0% of patients. CT scan and brain MRI showed cortical atrophy in the majority of cases. One hundred seventy-seven patients were treated with intravenous injection of aqueous penicillin G. Neurosyphilis is still a significant medical problem in developing countries, and its occurrence in HIV infection is the reason for a growing number of new cases in developed countries. Given the frequent atypical manifestations of the disease, screening for neurosyphilis should be considered in all patients with neurological or psychiatric symptoms.

Case report of the treatment and experience of mental disorders due to chronic viral encephalitis

Viral encephalitis is a common clinical condition. Its clinical manifestations are variable and include neurological symptoms and psychiatric abnormalities, which makes clinical diagnosis and treatment difficult. To date, there are only a few reported cases on mental symptoms of chronic viral encephalitis. We present a case of a 16-year-old male patient who was previously hospitalised and diagnosed with schizophrenia and treated with aripiprazole 15 mg/day but failed to respond. The patient was then given antiviral therapy and recovered after 2 weeks. Clinicians should be aware of the possbility that chronic mental disorders could be caused by viral encephalitis. In the future, diagnosis of chronic functional mental disorders should include viral encephalitis in the differential diagnosis.

The Challenge of Assessing Mild Neuroinflammation in Severe Mental Disorders

Recent psychoneuroimmunology research has provided new insight into the etiology and pathogenesis of severe mental disorders (SMDs). The mild encephalitis (ME) hypothesis was developed with the example of human Borna disease virus infection years ago and proposed, that a subgroup SMD patients, mainly from the broad schizophrenic and affective spectrum, could suffer from mild neuroinflammation, which remained undetected because hard to diagnose with available diagnostic methods. Recently, in neurology an emerging new subgroup of autoimmune encephalitis (AE) cases suffering from various neurological syndromes was described in context with the discovery of an emerging list of Central Nervous System (CNS) autoantibodies. Similarly in psychiatry, consensus criteria of autoimmune psychosis (AP) were developed for patients presenting with CNS autoantibodies together with isolated psychiatric symptoms and paraclinical findings of (mild) neuroinflammation, which in fact match also the previously proposed ME criteria. Nevertheless, identifying mild neuroinflammation in vivo in the individual SMD case remains still a major clinical challenge and the possibility that further cases of ME remain still under diagnosed appears an plausible possibility. In this paper a critical review of recent developments and remaining challenges in the research and clinical diagnosis of mild neuroinflammation in SMDs and in general and in transdisciplinary perspective to psycho-neuro-immunology and neuropsychiatry is given. Present nosological classifications of neuroinflammatory disorders are reconsidered with regard to findings from experimental and clinical research. A refined grading list of clinical states including "classical" encephalitis, AE, AP/ME,and newly proposed terms like parainflammation, stress-induced parainflammation and neuroprogression, and their respective relation to neurodegeneration is presented, which may be useful for further research on the possible causative role of mild neuroinflammation in SMDs. Beyond, an etiology-focused subclassification of ME subtypes, like autoimmune ME or infectious ME, appears to be required for differential diagnosis and individualized treatment. The present status of the clinical diagnosis of mild neuroinflammatory mechanisms involved in SMDs is outlined with the example of actual diagnosis and therapy in AP. Ideas for future research to unravel the contribution of mild neuroinflammation in the causality of SMDs and the difficulties expected to come to novel immune modulatory, anti-infectious or anti-inflammatory therapeutic principles in the sense of precision medicine are discussed.

Novel Antineuronal Autoantibodies With Somatodendritic Staining Pattern in a Patient With Autoimmune Psychosis

BACKGROUND

Autoimmune encephalitis, such as anti-NMDA-receptor encephalitis, typically presenting with subacute onset of neuropsychiatric symptoms, can be detected by antineuronal autoantibodies or inflammatory changes in the cerebrospinal fluid (CSF), as well as pathological alterations in electroencephalography (EEG), magnetic resonance imaging (MRI), or [18F]fluorodeoxyglucose positron emission tomography (FDG PET). For patients with predominant psychotic symptoms, the term autoimmune psychosis was proposed. Here, the authors present the case of a patient with probable autoimmune psychosis associated with unknown antineuronal antibodies.

CASE PRESENTATION

A 18-year-old male patient with preexisting autism spectrum disorder developed a severe catatonic syndrome over 2.5 years. The MRI showed normal findings, the EEG depicted intermittent slowing, and the independent component analyses showed additional sharp spikes. However, FDG PET, the basic laboratory analysis and testing of the serum/CSF for well-characterized antineuronal autoantibodies were unsuspicious. The serum and CSF "tissue-based assay" using indirect immunofluorescence on unfixed murine brain tissue revealed antineuronal autoantibodies against an unknown epitope in granule cells in the cerebellum and to neurites of hippocampal interneurons with a somatodendritic staining pattern. The immunosuppressive treatment with high-dose glucocorticoids, plasma exchange, and rituximab led to partial improvement.

CONCLUSION

The patient probably suffered from autoantibody-associated autoimmune psychosis. The special features of the case were that the patient (1) presented with mostly inconspicuous basic diagnostics, except for the altered EEG in combination with the detection of CSF autoantibodies directed against a currently unknown epitope, (2) experienced an isolated and long-lasting psychotic course, and (3) had pre-existing autism spectrum disorder. The detection of a probable autoimmune pathophysiology in such cases seems important, as it offers new and more causal immunosuppressive treatment alternatives.

Autoimmune encephalitis as a differential diagnosis of schizophreniform psychosis: clinical symptomatology, pathophysiology, diagnostic approach, and therapeutic considerations

Primary schizophreniform psychoses are thought to be caused by complex gene-environment interactions. Secondary forms are based on a clearly identifiable organic cause, in terms of either an etiological or a relevant pathogenetic factor. The secondary or "symptomatic" forms of psychosis have reentered the focus stimulated by the discovery of autoantibody (Ab)-associated autoimmune encephalitides (AEs), such as anti-NMDA-R encephalitis, which can at least initially mimic variants of primary psychosis. These newly described secondary, immune-mediated schizophreniform psychoses typically present with the acute onset of polymorphic psychotic symptoms. Over the course of the disease, other neurological phenomena, such as epileptic seizures, movement disorders, or reduced levels of consciousness, usually arise. Typical clinical signs for AEs are the acute onset of paranoid hallucinatory symptoms, atypical polymorphic presentation, psychotic episodes in the context of previous AE, and additional neurological and medical symptoms such as catatonia, seizure, dyskinesia, and autonomic instability. Predominant psychotic courses of AEs have also been described casuistically. The term autoimmune psychosis (AP) was recently suggested for these patients. Paraclinical alterations that can be observed in patients with AE/AP are inflammatory cerebrospinal fluid (CSF) pathologies, focal or generalized electroencephalographic slowing or epileptic activity, and/or suspicious "encephalitic" imaging findings. The antibody analyses in these patients include the testing of the most frequently found Abs against cell surface antigens (NMDA-R, CASPR2, LGI1, AMPA-R, GABA_B-R), intracellular antigens (Hu, Ri, Yo, CV2/CRMP5, Ma2 [Ta], amphiphysin, GAD65), thyroid antigens (TG, TPO), and antinuclear Abs (ANA). Less frequent antineuronal Abs (e.g., against DPPX, GABA_A-R, glycine-R, IgLON5) can be investigated in the second step when first step screening is negative and/or some specific clinical factors prevail. Beyond, tissue-based assays on brain slices of rodents may detect previously unknown antineuronal Abs in some cases. The detection of clinical and/or paraclinical pathologies (e.g., pleocytosis in CSF) in combination with antineuronal Abs and the exclusion of alternative causes may lead to the diagnosis of AE/AP and enable more causal therapeutic immunomodulatory opportunities.

Autoimmune psychosis: an international consensus on an approach to the diagnosis and management of psychosis of suspected autoimmune origin

There is increasing recognition in the neurological and psychiatric literature of patients with so-called isolated psychotic presentations (ie, with no, or minimal, neurological features) who have tested positive for neuronal autoantibodies (principally N-methyl-D-aspartate receptor antibodies) and who have responded to immunotherapies. Although these individuals are sometimes described as having atypical, mild, or attenuated forms of autoimmune encephalitis, some authors feel that that these cases are sufficiently different from typical autoimmune encephalitis to establish a new category of so-called autoimmune psychosis. We briefly review the background, discuss the existing evidence for a form of autoimmune psychosis, and propose a novel, conservative approach to the recognition of possible, probable, and definite autoimmune psychoses for use in psychiatric practice. We also outline the investigations required and the appropriate therapeutic approaches, both psychiatric and immunological, for probable and definite cases of autoimmune psychoses, and discuss the ethical issues posed by this challenging diagnostic category.

Psychiatric Presentation of Anti-NMDA Receptor Encephalitis

Background: Anti-N-methyl D-aspartate (NMDA) receptor encephalitis is an autoimmune condition characterized by neuropsychiatric symptoms, including epileptic seizures, movement disorders, autonomic instability, disturbances of consciousness, paranoia, delusions, and catatonia. Ovarian teratomas and viral infections, typically Herpes simplex viruses, have previously been demonstrated to precipitate anti-NMDA receptor encephalitis, but in many cases, the trigger remains unclear. The detection of anti-NMDA receptor antibodies in cerebrospinal fluid (CSF), in combination with other CSF, electroencephalography (EEG), or magnetic resonance imaging (MRI) abnormalities, typically leads to diagnostic clarification.

Case Presentation: We present the case of a 22-year-old female patient who developed an acute polymorphic psychotic episode 3 days after receiving a booster vaccination against tetanus, diphtheria, pertussis, and polio (Tdap-IPV). Her psychiatric symptoms were initially diagnosed as a primary psychiatric disorder. Her MRI, EEG, and CSF results were non-specific. Anti-NMDA receptor IgG antibodies against the GluN1 subunit were detected in her serum (with a maximum titer of 1:320), but not in her CSF. [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) showed pronounced relative hypermetabolism of her association cortices and a relative hypometabolism of the primary cortices, on the basis of which an anti-NMDA receptor encephalitis diagnosis was made, and treatment with a steroid pulse was initiated. The treatment led to fast and convincing clinical improvement with normalization of neuropsychological findings, considerable improvement of FDG-PET findings, and decreasing antibody titers.

Conclusion: The patient's psychiatric symptoms were most likely caused by anti-NMDA receptor encephalitis. Her polymorphic psychotic symptoms first occurred after she had received a Tdap-IPV booster vaccination. Although the vaccination cannot have caused the initial antibody formation since IgG serum antibodies were detected only 3 days after administration of the vaccine, the vaccine may have exerted immunomodulatory effects. MRI, EEG, and CSF findings were non-specific; however, FDG-PET identified brain involvement consistent with anti-NMDA receptor encephalitis. This case shows the importance of implementing a multimodal diagnostic work-up in similar situations. The negative CSF antibody finding furthermore fits to the hypothesis that the brain may act as an immunoprecipitator for anti-NMDA receptor antibodies.