AMPA receptor antibodies in limbic encephalitis alter synaptic receptor location

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.

A Rare Case of Wobbly, Psychotic Patient with Frozen Eyes - Anti-AMPA Receptor Encephalitis

Background

Anti α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis is a rare autoimmune encephalitis. They present with memory, confusion or behavioral changes.

Objective

The aim of this study was to describe unusual clinical features in a patient with AMPAR-associated encephalitis.

Case

A 42-year-old female presented to us with bulbar and gait disturbances of three weeks duration and behavioral changes for ten days. She was found to have memory impairment along with psychosis. She had left eye ptosis, restricted eye movements, sluggish deep tendon reflexes, and bilateral cerebellar signs. Her serum and CSF (cerebrospinal fluid) AMPAR2 antibodies were strongly positive; CT (computed tomography) chest showed evidence of Thymoma. She was treated with steroids with significant improvement initially but expired within 3 months of diagnosis.

Conclusion

This is the first report of AMPAR associated encephalitis from India presenting with unique clinical features affecting both the CNS (central nervous system)--(psychosis, ataxia, cognition) and PNS--peripheral nervous system involvement (ptosis, restricted eye movements, bulbar disturbances).

Short- and Long-Lived Autoantibody-Secreting Cells in Autoimmune Neurological Disorders

As B cells differentiate into antibody-secreting cells (ASCs), short-lived plasmablasts (SLPBs) are produced by a primary extrafollicular response, followed by the generation of memory B cells and long-lived plasma cells (LLPCs) in germinal centers (GCs). Generation of IgG4 antibodies is T helper type 2 (Th2) and IL-4, -13, and -10-driven and can occur parallel to IgE, in response to chronic stimulation by allergens and helminths. Although IgG4 antibodies are non-crosslinking and have limited ability to mobilize complement and cellular cytotoxicity, when self-tolerance is lost, they can disrupt ligand-receptor binding and cause a wide range of autoimmune disorders including neurological autoimmunity. In myasthenia gravis with predominantly IgG4 autoantibodies against muscle-specific kinase (MuSK), it has been observed that one-time CD20⁺ B cell depletion with rituximab commonly leads to long-term remission and a marked reduction in autoantibody titer, pointing to a short-lived nature of autoantibody-secreting cells. This is also observed in other predominantly IgG4 autoantibody-mediated neurological disorders, such as chronic inflammatory demyelinating polyneuropathy and autoimmune encephalitis with autoantibodies against the Ranvier paranode and juxtaparanode, respectively, and extends beyond neurological autoimmunity as well. Although IgG1 autoantibody-mediated neurological disorders can also respond well to rituximab induction therapy in combination with an autoantibody titer drop, remission tends to be less long-lasting and cases where titers are refractory tend to occur more often than in IgG4 autoimmunity. Moreover, presence of GC-like structures in the thymus of myasthenic patients with predominantly IgG1 autoantibodies against the acetylcholine receptor and in ovarian teratomas of autoimmune encephalitis patients with predominantly IgG1 autoantibodies against the N‐methyl‐d‐aspartate receptor (NMDAR) confers increased the ability to generate LLPCs. Here, we review available information on the short-and long-lived nature of ASCs in IgG1 and IgG4 autoantibody-mediated neurological disorders and highlight common mechanisms as well as differences, all of which can inform therapeutic strategies and personalized medical approaches.

Anti-Alpha-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid Receptor Encephalitis: A Review

Anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis, a rare subtype of autoimmune encephalitis, was first reported by Lai et al. The AMPAR antibodies target against extracellular epitopes of the GluA1 or GluA2 subunits of the receptor. AMPARs are expressed throughout the central nervous system, especially in the hippocampus and other limbic regions. Anti-AMPAR encephalitis was more common in middle-aged women and most patients had an acute or subacute onset. Limbic encephalitis, a classic syndrome of anti-AMPAR encephalitis, was clinically characterized by a subacute disturbance of short-term memory loss, confusion, abnormal behavior and seizure. Magnetic resonance imaging often showed T2/fluid-attenuated inversion-recovery hyperintensities in the bilateral medial temporal lobe. For suspected patients, paired serum and cerebrospinal fluid (CSF) testing with cell-based assay were recommended. CSF specimen was preferred given its higher sensitivity. Most patients with anti-AMPAR encephalitis were complicated with tumors, such as thymoma, small cell lung cancer, breast cancer, and ovarian cancer. First-line treatments included high-dose steroids, intravenous immunoglobulin and plasma exchange. Second-line treatments, including rituximab and cyclophosphamide, can be initiated in patients who were non-reactive to first-line treatment. Most patients with anti-AMPAR encephalitis showed a partial neurologic response to immunotherapy.

Autoimmune Global Amnesia as Manifestation of AMPAR Encephalitis and Neuropathologic Findings

OBJECTIVE

To report an unusual clinical phenotype of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis and describe associated neuropathologic findings.

METHODS

We retrospectively investigated 3 AMPAR encephalitis patients with autoimmune global hippocampal amnesia using comprehensive cognitive and neuropsychologic assessment, antibody testing by in-house tissue-based and cell-based assays, and neuropathologic analysis of brain autopsy tissue including histology and immunohistochemistry.

RESULTS

Three patients presented with acute-to-subacute global amnesia without affection of cognitive performance, attention, concentration, or verbal function. None of the patients had epileptic seizures, change of behavior, personality changes, or psychiatric symptoms. The MRI was normal in 1 patient and showed increased fluid-attenuated inversion recovery/T2 signal in the hippocampus in the other 2 patients. Two patients showed complete remission after immunotherapy. The one patient who did not improve had an underlying adenocarcinoma of the lung and died 3.5 months after disease onset because of tumor progression. Neuropathologic analysis of the brain autopsy revealed unilateral hippocampal sclerosis accompanied by mild inflammatory infiltrates, predominantly composed of T lymphocytes, and decrease of AMPAR immunoreactivity.

CONCLUSION

AMPAR antibodies usually associate with limbic encephalitis but may also present with immune responsive, acute-to-subacute, isolated hippocampal dysfunction without overt inflammatory CSF or MRI changes.

Anti-N-Methyl-D-Aspartate Receptor Encephalitis with Serum Anti-Thyroid Antibodies: A Case Report and Literature Review

BACKGROUND Anti-N methyl D-aspartate receptor encephalitis (anti-NMDArE) is a disorder in which triggers such as infectious agents or neoplastic disease can lead to an autoimmune response against the nervous system, although this disorder is usually idiopathic. Some patients with anti-NMDArE have evidence of other autoimmune alterations. Here, we present a case of non-paraneoplastic anti-NMDArE with elevation of serum anti-thyroid antibodies and a literature review of this association. CASE REPORT A 16-year-old girl was admitted in the University Hospital of Bari for a new onset of tonic-clonic seizures. Progressively, the patient manifested also psychomotor agitation, language difficulties, memory impairment, psychotic symptoms, autonomic dysfunction, and psychomotor retardation. Blood evaluation revealed the presence of anti-thyroglobulin, anti-thyroperoxidase, and anti-NMDAr antibodies. Cerebrospinal fluid analysis confirmed the diagnosis of anti-NMDArE. No tumors were found. Treatment with intravenous immunoglobulin, steroids, and plasma exchange relieved symptoms and decreased levels of serum anti-NMDAr antibodies. After 12 months, the patient had full recovery of communicative capacity, with the persistence of slight difficulty of memory and mild tendency to irritability. Blood exams shown persistence of anti-NMDAr positivity and absence of anti-thyroid antibodies. CONCLUSIONS We report a rare case in which an autoimmune involvement of thyroid gland was concurrent with an anti-NMDArE. It would be useful for clinical practice to clarify whether the presence of anti-thyroid antibody an characterize the clinical course, prognosis, and response to treatment of the idiopathic type of anti-NMDArE.

Clinical Review and Prognostic Analysis of α-Amino-3-Hydroxy-5-Methyl-4-Isoxazole Propionate Receptor-Associated Encephalitis

Purpose: Autoimmune encephalitis (AE) is a heterogeneous neurological autoimmune disorder associated with cognitive and psychiatric symptoms. It can be divided into several subtypes based on autoantibodies. Anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor encephalitis (AMPAR-E) is one of the recently discovered AE subtypes, usually manifesting limbic encephalitis and with a good prognosis. Considering AMPAR-E has been described for the first time, only a few cases with similar antibodies have been reported clinically. We aimed to clarify the clinical course and prognosis of the disease in the light of previous reports. Patients and Methods: We collected data on the diagnosis and treatment of six cases of AMPAR-E, diagnosed at the Qilu Hospital of Shandong University in the past 5 years. We retrospectively analyzed the clinical characteristics of the patients and performed a follow-up of the disease. Results: The patients often presented with limbic encephalitis, which sometimes coexisted with tumors. In addition, immunotherapy had a significant effect on the disease. The clinical outcome was related to factors such as the age of onset, timing of treatment, and presence of tumors. Conclusion: In conclusion, specific antibody tests should be performed as early as possible in suspected cases. Clinicians should actively administer immunotherapy and the management of the co-tumor. In addition, repeat antibody tests and image examinations following discharge from the hospital guide the maintenance protocol of immunotherapy.

Clinical Character of CASPR2 Autoimmune Encephalitis: A Multiple Center Retrospective Study

Objective

To examine the clinical characteristics of autoimmune encephalitis associated with the contactin-associated protein-2 (CASPR2) antibody.

Materials and Methods

Medical records of all patients diagnosed with CASPR2 antibody-associated encephalitis were retrospectively analysed. Data regarding demographic features, neurological symptoms and signs, laboratory tests, imaging results, treatments, and prognosis were collected.

Results

A total of 25 patients aged from 3 to 79 years old were enrolled in this study, with a median age of 43. Eight of 25 (32%) were female, and 17 of 25 (68%) were male. The median age of symptom onset was 42 years old with the course of disease from onset to hospital admission ranging from 2 days to 6 months (median was 17 days). Six patients (6/25) had fever as an onset symptom. During the course of disease, cognitive disturbance was the most common symptom, which was observed in 17 patients (17/25) in total. Eight patients (8/25) met the criteria for limbic encephalitis. Epileptic seizure occurred in six of these eight patients. Four patients (4/25) were diagnosed as Morvan syndrome. All patients were positive for anti-CASPR2 antibody in the serum (1:10-1:300). In six patients, antibodies were detected both in the blood and CSF (1:32-1:100). White blood cell (WBC) counts in the CSF were elevated in eight patients (8/25). The concentration of proteins in CSF increased in 10 patients (ranging from 480 to 1,337.6 mg/dl), decreased in seven patients (ranging from 23.2 to 130.5 mg/dl) and remained at a normal range in the other eight patients (ranging from 150 to 450 mg/dl). Abnormal electroencephalogram (EEG) activities included slow background activity and epileptic patterns. Abnormal signals in the bilateral hippocampus were detected by magnetic resonance imaging (MRI) in three patients presenting cognitive disturbance. In one patient who had limbic encephalitis, increased metabolism of bilateral basal ganglia and the mesial temporal lobe was revealed by PET-CT. Eleven of 15 patients receiving immunotherapy experienced varying degrees of improvement. Relapse occurred in four of 25 patients (4/25) after 2 months.

Conclusion

CASPR-antibody-mediated autoimmune encephalitis is characterized by diverse clinical manifestations. The most prominent conclusion revealed by this retrospective analysis is the involvement of both central and peripheral nerve systems, as well as a lower relapse rate, a good response to immunotherapy, and favorable short-term prognosis after treatment was also demonstrated. Besides, additional work is necessary to evaluate the long-term prognosis.

The well responsiveness of drug-resistant focal seizures in anti-AMPA2 receptor encephalitis to perampanel treatment

Anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor encephalitis is an anti-neuronal surface antigen autoimmune encephalitis and is relatively rare. Our study evaluated a patient who developed anti-AMPA2 receptor encephalitis with memory deficits and refractory focal seizures as paroxysmal jerking on right face as well as dystonic seizure on right hand. On this patient, the combination treatment of levetiracetam, carbamazepine, and clonazepam, monthly periodic intravenous immunoglobin and immunosuppressive therapies for 5 months was not effective for the focal seizures, while his memory loss was slightly improved. However, adjunctive perampanel treatment led to a rapid relief of seizures. Perampanel is suggested in seizures associated with anti-AMPA receptor encephalitis by directly attenuating nerve hyperexcitability caused by glutamate and Ca2+-permeable GluA4 subunit of AMPA receptors.

Anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor encephalitis: A case report

INTRODUCTION

: Anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) is a subtype of glutamate receptor that mediates most of the fast excitatory neurotransmission in the brain. Anti-AMPAR encephalitis is an autoimmune-mediated neurological disorder, frequently accompanied by the presence of neoplasms, comprising a spectrum of paraneoplastic syndrome.

PATIENT CONCERNS

A 56-year-old man was admitted for deterioration in memory and aberrant psychological behaviors, which lasted for at least 20 days.

DIAGNOSIS

The patient was diagnosed as anti-AMPAR encephalitis and 4 months later, he was diagnosed with small cell lung cancer.

INTERVENTIONS

Once diagnosis for anti-AMPAR encephalitis was confirmed, methylprednisolone was prescribed with initial dose 500 mg/d for 14 days until the patient returned to pre-illness state. Then he was discharged with oral treatment with corticosteroids. Following the diagnosis of small cell lung cancer, he received 5 rounds of chemotherapy, including carboplatin and etoposide.

OUTCOMES

After taken the prescription of Methylprednisolone for anti-AMPAR encephalitis, he returned to pre-illness state and was discharged. In April 21, 2017, after symptoms of respiratory system showed up, he was diagnosed with small cell lung cancer and he eventually died of respiratory failure.

CONCLUSION

Though progress has been made in recent years in diagnosis and treatment for autoimmune encephalitis, it is challenging to diagnose due to the similarity in clinical findings with other autoimmune or infectious encephalitis. In addition, it is necessary for these patients to regularly have tumor screening, considering AMPAR antibody encephalitis is closely associated with neoplasm, and the incidence of paraneoplastic syndrome is 63% to 70%.

The Peculiar Clinical Symptoms and Treatment of Limbic Encephalitis Associated with AMPA Receptor Antibody

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) antibody-related diseases are very rare in autoimmune neurological diseases. We collected and analyzed the data of 3 patients with peculiar clinical manifestation positive for AMPA2-R antibody in the Department of Neurology, Xuanwu Hospital, Capital Medical University. In our reported case series, 2 patients were male and 1 was female. The initial clinical features of 3 patients were all consistent with an encephalopathy predominantly involving the limbic system. Interestingly, as the disease continues to advance, case 1 presented with limb paralysis, case 2 developed typical cerebellar ataxia, and case 3 had symptoms of autonomic instability. These 3 types of clinical features were very rare in patients with AMPAR-Ab. After immunotherapy, cases 1 and 3 responded well and case 2 was not responsive. During the follow-up, residual memory loss of cases 1 and 3 improved gradually, and they returned to work. To eliminate the influence of the presence of other pathogenic antibodies, we analyzed the available individual clinical information of 37 patients with the single AMPAR-Ab by systematic literature review. A majority of patients had sudden short-term memory loss as the initial symptom and developed limbic encephalitis. Residual memory deficit was the most common symptom after discharge. The combination of at least 2 types of immunotherapy was recommended as the first-line treatment, and patients would benefit from the tumor screening. In addition, compared with the patients positive for single AMPAR-Ab, the patients with both AMPAR-Ab and other antibodies had a higher risk of malignant tumor and might have a poor therapeutic response, which led to a poor prognosis.

Neurological complications of immune checkpoint inhibitor cancer immunotherapy

Neurological autoimmunity is increasingly recognized as a complication of immune checkpoint inhibitor (ICI) cancer immunotherapy. ICIs act by enhancing endogenous anti-tumor immune responses and can also lead to autoimmunity affecting all organs. ICI-related neurological autoimmunity is rare, most often manifests with neuromuscular involvement and more rarely affects the central nervous system. Neurological complications often often present in the first three months of ICI treatment but can also appear after ICI discontinuation. These can occur in patients with tumors not traditionally associated with paraneoplastic neurological autoimmunity, such as melanoma and renal-cell carcinoma and should be suspected when a new neurological symptoms present while on ICI and cannot be explained by disease progression or as a consequence of metabolic dysfunction. Treatment consists of ICI discontinuation or withdrawal depending on the severity with or without immunosuppression. Generally, improvement is observed depending on the patient's baseline characteristics and neurological presentation.

Autoimmune encephalopathies presenting as dementia of subacute onset and rapid progression

The terms autoimmune dementia and autoimmune encephalopathy may be used interchangeably; autoimmune dementia is used here to emphasize its consideration in young-onset dementia, dementia with a subacute onset, and rapidly progressive dementia. Given their potential for reversibility, it is important to distinguish the rare autoimmune dementias from the much more common neurodegenerative dementias. The presence of certain clinical features [e.g. facio-brachial dystonic seizures that accompany anti-leucine-rich-glioma-inactivated-1 (LGI1) encephalitis that can mimic myoclonus] can be a major clue to the diagnosis. When possible, objective assessment of cognition with bedside testing or neuropsychological testing is useful to determine the degree of abnormality and serve as a baseline from which immunotherapy response can be judged. Magnetic resonance imaging (MRI) head and cerebrospinal fluid (CSF) analysis are useful to assess for inflammation that can support an autoimmune etiology. Assessing for neural autoantibody diagnostic biomarkers in serum and CSF in those with suggestive features can help confirm the diagnosis and guide cancer search in paraneoplastic autoimmune dementia. However, broad screening for neural antibodies in elderly patients with an insidious dementia is not recommended. Moreover, there are pitfalls to antibody testing that should be recognized and the high frequency of some antibodies in the general population limit their diagnostic utility [e.g., anti-thyroid peroxidase (TPO) antibodies]. Once the diagnosis is confirmed, both acute and maintenance immunotherapy can be utilized and treatment choice varies depending on the accompanying neural antibody present and the presence or absence of cancer. The target of the neural antibody biomarker may help predict treatment response and prognosis, with antibodies to cell-surface or synaptic antigens more responsive to immunotherapy and yielding a better overall prognosis than those with antibodies to intracellular targets. Neurologists should be aware that autoimmune dementias and encephalopathies are increasingly recognized in novel settings, including post herpes virus encephalitis and following immune-checkpoint inhibitor use.

Anti-gamma-aminobutyric acid receptor type A encephalitis: a review

PURPOSE OF REVIEW

To systematically review the clinical features, diagnosis, and management of anti-gamma-aminobutyric acid receptor Type A (GABAA) autoimmune encephalitis with a focus on recent data.

RECENT FINDINGS

In a review of published reports, we identified 50 cases of anti-GABAA receptor encephalitis with clinical features reported. The median age at presentation was 47 years old (range, 2.5 months-88 years old), 64% were adults, 36% were children and it occurred in both males and females. Eight-two percent (41/50) presented with seizures, 72% (36/50) with encephalopathy, and 58% (29/50) with both. Of those presenting with seizures, 42% developed status epilepticus during their disease course. Ninety-six percent (48/50) had MRI results reported, with 83% of these cases having abnormal findings, most commonly multifocal/diffuse cortical and subcortical T2/FLAIR hyperintense lesions without associated gadolinium enhancement. Almost one-third, 28% (14/50), had an associated malignancy detected by the time of diagnosis, 64% (9/14) of which was thymoma. Of 44 patients with outcomes reported, 80% had partial or complete recovery, whereas 20% had poor outcomes including 11% (5/44) who died. Of the 42 patients with type of treatment(s) and outcomes reported, 54% (23/42) received only first-line immunotherapy and 31% (13/42) received first-line and second-line immunotherapy. Receiving a combination of first-line and second-line immunotherapy may be associated with higher likelihood of complete recovery. When follow-up MRIs were reported, all showed improvement, and sometimes complete resolution, of T2/FLAIR hyperintensities.

SUMMARY

Anti-GABAA receptor encephalitis can present across the age spectrum and should be considered in patients who present with rapidly progressive encephalopathy and/or seizures. Brain MRI often shows a distinctive pattern of multifocal cortical and subcortical T2/FLAIR hyperintense lesions, generally not typical of other known central nervous system autoantibody associated encephalitis syndromes. High clinical suspicion and early diagnosis are important given the potential for clinical improvement with immunotherapy.

NMDA and AMPA Receptor Autoantibodies in Brain Disorders: From Molecular Mechanisms to Clinical Features

The role of autoimmunity in central nervous system (CNS) disorders is rapidly expanding. In the last twenty years, different types of autoantibodies targeting subunits of ionotropic glutamate receptors have been found in a variety of patients affected by brain disorders. Several of these antibodies are directed against NMDA receptors (NMDAR), mostly in autoimmune encephalitis, whereas a growing field of research has identified antibodies against AMPA receptor (AMPAR) subunits in patients with different types of epilepsy or frontotemporal dementia. Several in vitro and in vivo studies performed in the last decade have dramatically improved our understanding of the molecular and functional effects induced by both NMDAR and AMPAR autoantibodies at the excitatory glutamatergic synapse and, consequently, their possible role in the onset of clinical symptoms. In particular, the method by which autoantibodies can modulate the localization at synapses of specific target subunits leading to functional impairments and behavioral alterations has been well addressed in animal studies. Overall, these preclinical studies have opened new avenues for the development of novel pharmacological treatments specifically targeting the synaptic activation of ionotropic glutamate receptors.

Paraneoplastic and autoimmune encephalitis: Alterations of mood and emotion

Autoimmune encephalitis often produces signs and symptoms that appear to be at the interface between neurology and psychiatry. Since psychiatric symptoms are often prominent, patients are often first seen in a psychiatric setting. Therefore it is important that psychiatrists, as well as neurologists, be able to recognize autoimmune encephalitis, a task that is often difficult. Early diagnosis of autoimmune encephalitis is crucial as this will usually result in a better outcome for the patient. This chapter provides an introduction to various autoimmune encephalitides and describes their pathophysiology and the possible associated neuropsychiatric, neuropsychological (cognitive), and neurological (sensory-motor) signs and symptoms. This chapter also reviews the possible treatments of these associated signs and symptoms.

Sleep Disturbances Associated with Neurological Autoimmunity

Associations between sleep disorders and neurological autoimmunity have been notably expanding recently. Potential immune-mediated etiopathogenesis has been proposed for various sleep disorders including narcolepsy, Kleine-Levin syndrome, and Morvan syndrome. Sleep manifestations are also common in various autoimmune neurological syndromes, but may be underestimated as overriding presenting (and potentially dangerous) neurological symptoms often require more urgent attention. Even so, sleep dysfunction has been described with various neural-specific antibody biomarkers, including IgLON5; leucine-rich, glioma-inactivated protein 1 (LGI1); contactin-associated protein 2 (CASPR2); N-methyl-D-aspartate (NMDA)-receptor; Ma2; dipeptidyl-peptidase-like protein-6 (DPPX); alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R); anti-neuronal nuclear antibody type-1 (ANNA-1, i.e., Hu); anti-neuronal nuclear antibody type-2 (ANNA-2, i.e., Ri); gamma-aminobutyric acid (GABA)-B-receptor (GABA-B-R); metabotropic glutamate receptor 5 (mGluR5); and aquaporin-4 (AQP-4). Given potentially distinctive findings, it is possible that sleep testing could potentially provide objective biomarkers (polysomnography, quantitative muscle activity during REM sleep, cerebrospinal fluid hypocretin-1) to support an autoimmune diagnosis, monitor therapeutic response, or disease progression/relapse. However, more comprehensive characterization of sleep manifestations is needed to better understand the underlying sleep disruption with neurological autoimmunity.

Autoimmune encephalitis: novel therapeutic targets at the preclinical level

INTRODUCTION

Antibody-mediated encephalitides (AE) with pathogenic autoantibodies (aAB) against neuronal surface antigens are a growing group of diseases characterized by antineuronal autoimmunity in the brain. AE patients typically present with rapidly progressive encephalitis and characteristic disease symptoms dependent on the target antigen. Current treatment consists of an escalating immunotherapy strategy including plasma exchange, steroid application, and B cell depletion.

AREAS COVERED

For this review, we searched Medline database and google scholar with inclusive dates from 2000. We summarize current treatment strategies and present novel therapeutic approaches of target-specific interventions at the pre-clinical level as well as immunotherapy directed at antibody-induced pathology. Treatment options include modulation of target proteins, intervention with downstream pathways, antibody modification, and depletion of antibody-secreting cells.

EXPERT OPINION

Although current therapies in AE are effective in many patients, recovery is often prolonged and relapses as well as persistent deficits can occur. Specific immunotherapy together with supportive target-specific therapy may provide faster control of severe symptoms, shorten the disease course, and lead to long-lasting disease stability. Among the various novel therapeutic approaches, modulation of targeted receptors by small molecules crossing the blood-brain barrier as well as prevention of aAB binding is of particular interest.

Neuropsychiatric Disorders Due to Limbic Encephalitis: Immunologic Aspect

Limbic encephalitis (LE) is a rare cause of encephalitis presenting as an acute and subacute onset of neuropsychiatric manifestations, particularly with memory deficits and confusion as core features, along with seizure occurrence, movement disorders, or autonomic dysfunctions. LE is caused by neuronal antibodies targeting the cellular surface, synaptic, and intracellular antigens, which alter the synaptic transmission, especially in the limbic area. Immunologic mechanisms involve antibodies, complements, or T-cell-mediated immune responses in different degree according to different autoantibodies. Sensitive cerebrospinal fluid markers of LE are unavailable, and radiographic findings may not reveal a typical mesiotemporal involvement at neurologic presentations; therefore, a high clinical index of suspicions is pivotal, and a neuronal antibody testing is necessary to make early diagnosis. Some patients have concomitant tumors, causing paraneoplastic LE; therefore, tumor survey and treatment are required in addition to immunotherapy. In this study, a review on the molecular and immunologic aspects of LE was conducted to gain awareness of its peculiarity, which we found quite different from our knowledge on traditional psychiatric illness.

Diagnostic Value of Structural and Functional Neuroimaging in Autoimmune Epilepsy

Epilepsy is a common nervous system disease, which affects about 70 million people all over the world. In 2017, the International League Against Epilepsy (ILAE) considered immune factors as its independent cause, and the concept of autoimmune epilepsy (AE) was widely accepted. Early diagnosis and timely treatment can effectively improve the prognosis of the disease. However, due to the diversity of clinical manifestations, the expensive cost of autoantibody detection, and the increased prevalence in Western China, the difficulty for clinicians in early diagnosis and treatment has increased. Fortunately, convenient and fast imaging examinations are expected to help even more. The imaging manifestations of AE patients were characteristic, especially the combined application of structural and functional neuroimaging, which improved the diagnostic value of imaging. In this paper, several common autoantibodies associated with AE and their structure and function changes in neuroimaging were reviewed to provide help for neurologists to achieve the goal of precision medicine.

Sleep disorders in autoimmune encephalitis

Sleep disorders in people with autoimmune encephalitis have received little attention, probably overshadowed by the presence of other neurological and psychiatric symptoms in this group of conditions. However, sleep disorders are frequent, often severe, and usually persist beyond the acute disease stage, interfering with patients' recovery and quality of life. Because autoimmune encephalitis can affect any brain network involved in sleep initiation and regulation, all types of sleep disorders can occur, with varying distinct associations, frequency, and intensity. Anti-IgLON5 and anti-NMDA receptor encephalitis exemplify two diseases in which sleep disorders are prominent. In anti-IgLON5 disease, sleep disorders were the core symptoms that led to the description of this disease, whereas in anti-NMDA receptor encephalitis, sleep disorders vary according to the disease stage along with other neuropsychiatric symptoms. Comprehensive, systematic, multicentre studies are needed to characterise sleep disorders and their mechanisms in autoimmune encephalitis.

Surgical treatment is effective in treating thymoma accompanied with non-myasthenia gravis autoimmune diseases: a single-center clinical experience

BACKGROUND AND AIMS

Although thymoma is inextricably linked to autoimmune disease, its best treatment method remains unclear. In this study, we sought to evaluate therapeutic effect of surgical resection of thymoma on non-myasthenia gravis autoimmune diseases.

MATERIALS AND METHODS

This was a retrospective study covering 32 patients with thymoma accompanied with non-myasthenia gravis autoimmune disease. The relationships between surgical treatment, thymoma pathological type, and prognosis of autoimmune diseases were analyzed from postoperative follow-up data.

RESULTS

In total, 32 patients in this study underwent surgical treatment. The mean age of the patients was 51.7 years. By the last follow-up, 2 patients had died, while the other 30 patients showed no sign of tumor recurrence and metastasis. According to the postoperative follow-up data, 22 patients (68.75%) showed improvement or even complete recovery of autoimmune disease symptoms, 9 patients (28.13%) showed no significant change, and only 1 patient's (3.12%) postoperative symptom was aggravated. Female patients and patients aged 50 and older were more likely to combine with non-organ-specific autoimmune diseases (p = 0.036, p = 0.017).

CONCLUSIONS

In conclusion, this study presents that surgical treatment achieves a satisfactory prognosis for thymoma combined with non-myasthenia gravis autoimmune disease.

Psychiatric symptoms in anti glutamic acid decarboxylase associated limbic encephalitis in adults: a systematic review

Autoimmune Limbic Encephalitis (LE) is a relatively new category of immune-mediated diseases with a wide range of neuropsychiatric symptoms. LE associated with Glutamic Acid Decarboxylase (GAD) antibodies is difficult to diagnose due to its possible atypical presentation with neuropsychiatric and behavioral features. We performed a systematic review of literature and retrieved 21 cases of anti GAD-associated LE with neuropsychiatric signs. Median age at onset was 27 years with a female predominance (81.0 %) and median diagnostic delay of 6 months. Clinical presentation included typical LE symptoms such as anterograde amnesia (95.2 %) and temporal lobe or tonico-clonic seizures (95.2 %). Psychiatric symptoms were described in 61.9 % of patients, presenting as anxiety, depressive symptoms, apathy and behavioral changes. Extra-limbic symptoms were present in 14.3 % of patients. No neoplasia associated was found. Some patients had poor epileptic, cognitive and psychiatric outcomes requiring prolonged immunosuppressive treatment. The description of the neuropsychiatric spectrum of anti-GAD LE and its specificities aims to improve our understanding of this entity, and may lead to earlier diagnosis as well as better outcome.

Autoimmune encephalitis with psychiatric features in adults: historical evolution and prospective challenge

Our review aims to delineate the psychiatric spectrum of autoantibody-associated autoimmune encephalitis over time through its discoveries of antibodies. We searched in PubMed for appropriate articles depicting the first appearance and spectrum of psychiatric symptomatology in autoantibody-positive encephalitis for this narrative review. Memory impairment was first associated with autoantibodies against intracellular antigens such as anti-HuD antibodies in 1993. 8 years later, autoantibodies against cell membrane surface antigens such as voltage-gated potassium channels were described in conjunction with memory dysfunction. The spectrum of psychiatric syndromes was amplified between 1990 and 2020 to include disorientation, behavior, cognitive dysfunction, obsessive compulsive behavior and suicidality in encephalitis patients occurring together mainly with antibodies against surface antigens, less so against intracellular antigens. In general, we found no specific psychiatric symptoms underlying specific autoantibody-associated encephalitis. As fundamental data on this issue have not been systemically assessed to date, we cannot know whether our specific findings would remain from systematic studies, i.e., on the association between cerebrospinal fluid N-methyl-D-aspartate receptor antibodies in catatonia. The psychiatric symptomatology overlaps between psychiatric domains and occurs frequently in antibody-positive encephalitis. No specific psychiatric symptoms imply an underlying, specifically autoantibody-associated encephalitis. The psychiatric phenotypology associated with antibody-positive encephalitis has evolved tremendously recently, and this new evidence reveals its relevance for future diagnostic and treatment aspects of autoimmune encephalitis patients.

Clinical features, prognostic factors, and antibody effects in anti-mGluR1 encephalitis

OBJECTIVE

To clinically characterize patients with anti-metabotropic glutamate receptor (mGluR) 1 encephalitis, to identify prognostic factors, and to study the immunoglobulin G (IgG) subclasses and effects of antibodies on neuronal mGluR1 clusters.

METHODS

Clinical information on new and previously reported patients was reviewed. Antibodies to mGluR1 and IgG subclasses were determined with brain immunohistochemistry and cell-based assays, and their effects on mGluR1 clusters were studied on rat hippocampal neurons.

RESULTS

Eleven new patients were identified (10 adults, 1 child);4 were female. In these and 19 previously reported cases (n = 30, median age 55 years), the main clinical manifestation was a subacute cerebellar syndrome that in 25 (86%) patients was associated with behavioral/cognitive changes or other neurologic symptoms. A tumor was found in 3 of 26 (11%). Brain MRI was abnormal in 7 of 19 (37%) at onset and showed cerebellar atrophy in 10 of 12 (83%) at follow-up. Twenty-five of 30 (83%) patients received immunotherapy. Follow-up was available for 25: 13 (52%) had clinical stabilization; 10 (40%) showed significant improvement; and 2 died. At the peak of the disease, patients with bad outcome at 2 years (modified Rankin Scale score > 2, n = 7) were more likely to have higher degree of initial disability, as reflected by a worse Scale for Assessment and Rating of Ataxia score, and more frequent need of assistance to walk. Antibodies to mGluR1 were mainly IgG1 and caused a significant decrease of mGluR1 clusters in cultured neurons.

CONCLUSIONS

Anti-mGluR1 encephalitis manifests as a severe cerebellar syndrome, often resulting in long-term disability and cerebellar atrophy. The antibodies are pathogenic and cause significant decrease of mGluR1 clusters in cultured neurons.

Cognitive impact of neuronal antibodies: encephalitis and beyond

Cognitive dysfunction is a common feature of autoimmune encephalitis. Pathogenic neuronal surface antibodies are thought to mediate distinct profiles of cognitive impairment in both the acute and chronic phases of encephalitis. In this review, we describe the cognitive impairment associated with each antibody-mediated syndrome and, using evidence from imaging and animal studies, examine how the nature of the impairment relates to the underlying neuroimmunological and receptor-based mechanisms. Neuronal surface antibodies, particularly serum NMDA receptor antibodies, are also found outside of encephalitis although the clinical significance of this has yet to be fully determined. We discuss evidence highlighting their prevalence, and association with cognitive outcomes, in a number of common disorders including cancer and schizophrenia. We consider mechanisms, including blood-brain barrier dysfunction, which could determine the impact of these antibodies outside encephalitis and account for much of the clinical heterogeneity observed.

Presence of anti-neuronal antibodies in children with neurological disorders beyond encephalitis

BACKGROUND

Anti-neuronal autoantibodies have been reported as the cause of several neurologic disorders other than encephalitis. Unfortunately, data are mostly based on serum analysis. Predictions about pathogenicity are thus limited. To determine the presence of so far unidentified autoantibody-derived neuroreactivity we analyzed cerebrospinal fluid (CSF) of children with neurological disorders other than encephalitis.

PATIENTS AND METHODS

We did a retrospective analysis of CSF from 254 children with various neurologic diseases other than encephalitis and searched for reactivity against neuronal surface antigens by immunofluorescence on unfixed murine brain sections (tissue-based assay, TBA) and by commercial cell-based assays (CBA). A semi-quantitative fluorescence score classified our results and we described the clinical course of all positive patients with strong neuroreactivity.

RESULTS

Strong anti-neuronal IgG immunoreactivity of unknown antigen specificity was detected in CSF samples of 10 pediatric patients (4%, n = 10/254) with unsolved neurological disorders. CSF inflammatory markers were elevated. Most patients did not or only partly recover. Five screening-positive patients presented with a combination of headache and visual impairment due to optic nerve atrophy. Our data suggest to consider inflammatory, autoantibody-related etiologies, especially in cases without definite diagnoses.

CONCLUSIONS

We present an overview of CSF neuroreactivity in children with neurological disorders other than encephalitis, indicating the presence of unidentified anti-neuronal autoantibodies. As TBA enables screening for unknown autoantibodies, we suggest this method as a second step if commercial CBAs do not yield a result. Further studies are necessary to characterize such antibodies, evaluate pathogenicity, and answer the question whether positive CSF neuroreactivity should prompt an immunotherapeutic approach.

Neuroimmunological antibody-mediated encephalitis and implications for diagnosis and therapy in neuropsychiatry

The past decade has seen a surge of reports and investigations into cases of autoimmune-mediated encephalitis. The increasing recognition of these disorders is especially of relevance to the fields of neurology and psychiatry. Autoimmune encephalitis involves antibodies against synaptic receptors, neuronal cell surface proteins and intracellular targets. These disorders feature prominent symptoms of cognitive impairment and behavioural changes, often associated with the presence of seizures. Early in the clinical course, autoimmune encephalitis may manifest as psychiatric symptoms of psychosis and involve psychiatry as an initial point of contact. Although commonly associated with malignancy, these disorders can present in the absence of an inciting neoplasm. The identification of autoimmune encephalitis is of clinical importance as a large proportion of individuals experience a response to immunotherapy. This review focuses on the current state of knowledge on n-methyl-d-aspartate (NMDA) receptor-associated encephalitis and limbic encephalitis, the latter predominantly involving antibodies against the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, the γ-aminobutyric acid (GABA)B receptor and leucine-rich glioma-inactivated 1 (LGI1) protein. In addition, we briefly describe anti-dopamine D2 receptor encephalitis. A summary of the literature will focus on common clinical presentations and course, diagnostic approaches and response to treatment. Since a substantial proportion of patients with autoimmune encephalitis exhibit symptoms of psychosis, the relevance of this disorder to theories of psychosis and schizophrenia will also be discussed.

Autoimmune encephalitis and epilepsy: evolving definition and clinical spectrum

Advances in autoimmune encephalitis studies in the past 10 years have led to the identification of new syndromes and biomarkers that have transformed the diagnostic approach to the disorder. The disorder or syndrome has been linked to a wide variety of pathologic processes associated with the neuron-specific autoantibodies targeting intracellular and plasma membrane antigens. However, current criteria for autoimmune encephalitis are quite dependent on antibody testing and responses to immunotherapy, which might delay the diagnosis. This form of encephalitis can involve the multifaceted presentation of seizures and unexpected behavioral changes. The spectrum of neuropsychiatric symptoms in children is less definitive than that in adults, and the incorporation of clinical, immunological, electrophysiological, and neuroradiological results is critical to the diagnostic approach. In this review, we document the clinical and immunologic characteristics of autoimmune encephalitis known to date, with the goal of helping clinicians in differential diagnosis and to provide prompt and effective treatment.

Diagnosis and treatment of limbic encephalitis in the cancer patient

Limbic encephalitis is an inflammatory process involving the limbic structures of the brain, manifested with short-term memory deficits, confusion, depression and seizures. It is usually a paraneoplastic condition but it may also appear as a nonparaneoplastic syndrome. Patients with this condition may exhibit a variety of antibodies in their serum or/and cerebrospinal fluid targeting basement membrane components that bind to a variety of neurotransmitter receptors such as α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and GABA B and proteins associated to the ion channels such as LGI1, Caspr2 or intracellular components. Flurodeoxyglucose PET/computed tomography usually demonstrates increased uptake in the limbic structures, and it may reveal the site of the primary tumor. Treatment consists of tumor removal if possible. Symptomatic treatment includes steroids, gamma immune globulin, plasma exchange, immunosuppressive therapies and anti-epileptic drugs. Prognosis is better when it is associated with antibodies against basement membrane rather than intracellular antibodies.

Catatonia secondary to anti-N-methyl-D-aspartate receptor (NMDAr) encephalitis: a review

Anti-N-methyl-D-aspartate receptor (NMDAr) encephalitis is a relatively recent autoimmune entity, as it was first described in 2007. Given that it is a condition with neuropsychiatric symptoms, its initial symptom is frequently psychiatric in nature. Hence, psychiatrists are often the first physicians to assess these patients and, as so, must recognize this type of encephalitis as a possible cause. Catatonia may be inaugural or develop throughout the course of the disease. Management of patients with anti-NMDAr encephalitis is based on etiologic treatment with immunotherapy and removal of the associated tumor, if any. However, these catatonic patients may have variable responses to etiologic treatment, sometimes with refractory catatonic symptoms, which attests to the necessary urgency to know how to manage these patients. In the clinical setting, physicians appear to be using guidelines originally created to the management of catatonia due to primary psychiatric conditions. In this literature review, catatonia was historically contextualized and anti-NMDAr encephalitis overall described. Finally, catatonia secondary to this type of encephalitis was discussed.

Clinically based score predicting cryptogenic NORSE at the early stage of status epilepticus

Objective

To determine whether a clinically based score predicts cryptogenic new-onset refractory status epilepticus (C-NORSE) at the early stage of status epilepticus (SE) with prominent motor symptoms (SE-M) of unclear etiology.

Methods

The score (range 0–6) included 6 clinical features: highly refractoriness to antiseizure drugs, previously healthy individual, presence of prodromal fever, absence of prodromal psychobehavioral or memory alterations, absence of dyskinesias, and symmetric brain MRI abnormalities (the first 2 mandatory). We retrospectively assessed the usefulness of a high scale score (≥5) in predicting C-NORSE in 83 patients with SE-M of unclear etiology, who underwent testing for neuronal surface antibodies (NS-Abs) between January 2007, and December 2019.

Results

Thirty-one (37.3%) patients had a high score. Patients with a high score had more frequent prodromal fever (28/31 vs 24/52), mechanical ventilatory support (31/31 vs 36/52), and symmetric MRI abnormalities (26/31 vs 12/52), had less frequent involuntary movements (2/31 vs 30/52), and had absent prodromal psychobehavioral alterations (0/31 vs 27/52), CSF oligoclonal band detection (0/27 vs 11/38), tumor association (0/31 vs 13/52), or NS-Abs (0/31 vs 29/52) than those with a low score (<5). Thirty-three patients (median age, 27 years; 18 [54.5%] female) were finally regarded as C-NORSE. The sensitivity and specificity of a high score for predicting C-NORSE were 93.9% (95% CI 0.87–0.94) and 100% (95% CI 0.95–1.00), respectively.

Conclusions

Patients with a high score in the indicated scale are more likely to have C-NORSE, making it a useful diagnostic tool at the early stage of SE-M before antibody test results become available.

Significance of Autoantibodies in Autoimmune Encephalitis in Relation to Antigen Localization: An Outline of Frequently Reported Autoantibodies with a Non-Systematic Review

Autoantibodies related to central nervous system (CNS) diseases propel research on paraneoplastic neurological syndrome (PNS). This syndrome develops autoantibodies in combination with certain neurological syndromes and cancers, such as anti-HuD antibodies in encephalomyelitis with small cell lung cancer and anti-Yo antibodies in cerebellar degeneration with gynecological cancer. These autoantibodies have roles in the diagnosis of neurological diseases and early detection of cancers that are usually occult. Most of these autoantibodies have no pathogenic roles in neuronal dysfunction directly. Instead, antigen-specific cytotoxic T lymphocytes are thought to have direct roles in neuronal damage. The recent discoveries of autoantibodies against neuronal synaptic receptors/channels produced in patients with autoimmune encephalomyelitis have highlighted insights into our understanding of the variable neurological symptoms in this disease. It has also improved our understanding of intractable epilepsy, atypical psychosis, and some demyelinating diseases that are ameliorated with immune therapies. The production and motility of these antibodies through the blood-brain barrier into the CNS remains unknown. Most of these recently identified autoantibodies bind to neuronal and glial cell surface synaptic receptors, potentially altering the synaptic signaling process. The clinical features differ among pathologies based on antibody targets. The investigation of these antibodies provides a deeper understanding of the background of neurological symptoms in addition to novel insights into their basic neuroscience.

Fundamental Mechanisms of Autoantibody-Induced Impairments on Ion Channels and Synapses in Immune-Mediated Cerebellar Ataxias

In the last years, different kinds of limbic encephalitis associated with autoantibodies against ion channels and synaptic receptors have been described. Many studies have demonstrated that such autoantibodies induce channel or receptor dysfunction. The same mechanism is discussed in immune-mediated cerebellar ataxias (IMCAs), but the pathogenesis has been less investigated. The aim of the present review is to evaluate what kind of cerebellar ion channels, their related proteins, and the synaptic machinery proteins that are preferably impaired by autoantibodies so as to develop cerebellar ataxias (CAs). The cerebellum predictively coordinates motor and cognitive functions through a continuous update of an internal model. These controls are relayed by cerebellum-specific functions such as precise neuronal discharges with potassium channels, synaptic plasticity through calcium signaling pathways coupled with voltage-gated calcium channels (VGCC) and metabotropic glutamate receptors 1 (mGluR1), a synaptic organization with glutamate receptor delta (GluRδ), and output signal formation through chained GABAergic neurons. Consistently, the association of CAs with anti-potassium channel-related proteins, anti-VGCC, anti-mGluR1, and GluRδ, and anti-glutamate decarboxylase 65 antibodies is observed in IMCAs. Despite ample distributions of AMPA and GABA receptors, however, CAs are rare in conditions with autoantibodies against these receptors. Notably, when the autoantibodies impair synaptic transmission, the autoimmune targets are commonly classified into three categories: release machinery proteins, synaptic adhesion molecules, and receptors. This physiopathological categorization impacts on both our understanding of the pathophysiology and clinical prognosis.

Sleep Disturbances in Patients with Autoimmune Encephalitis

PURPOSE OF REVIEW

To review sleep complaints reported in patients with autoimmune encephalitis, explore the relationship between sleep disturbances and subtypes of autoimmune encephalitis, and leverage knowledge concerning antibody-antigen specificity to inform the receptors, structures, and disseminated neural networks that contribute to sleep function in health and disease.

RECENT FINDINGS

Autoimmune encephalitis is an inflammatory brain disorder characterized by the subacute onset of psychiatric symptoms, cognitive impairment, and focal neurologic deficits or seizures. Sleep disturbances are detected in a majority of patients systematically screened for sleep complaints, may be the presenting symptom in patients with autoimmune encephalitis, and may compromise recovery in patients with autoimmune encephalitis. Early recognition of specific sleep disturbances in patients with subacute changes in behavior or cognition may support the diagnosis of autoimmune encephalitis. Similarly, recognition and treatment of sleep dysfunction in patients with known autoimmune encephalitis may speed recovery and improve long-term outcomes.

Abolishing spontaneous epileptiform activity in human brain tissue through AMPA receptor inhibition

Objective

The amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid receptor (AMPAR) is increasingly recognized as a therapeutic target in drug‐refractory pediatric epilepsy. Perampanel (PER) is a non‐competitive AMPAR antagonist, and pre‐clinical studies have shown the AMPAR‐mediated anticonvulsant effects of decanoic acid (DEC), a major medium‐chain fatty acid provided in the medium‐chain triglyceride ketogenic diet.

Methods

Using brain tissue resected from children with intractable epilepsy, we recorded the effects of PER and DEC in vitro.

Results

We found resected pediatric epilepsy tissue exhibits spontaneous epileptic activity in vitro, and showed that DEC and PER inhibit this epileptiform activity in local field potential recordings as well as excitatory synaptic transmission.

Interpretation

This study confirms AMPAR antagonists inhibit epileptiform discharges in brain tissue resected in a wide range of pediatric epilepsies.

Experimental Models of Neuroimmunological Disorders: A Review

Immune-mediated inflammatory diseases of the central nervous system (CNS) are a group of neurological disorders in which inflammation and/or demyelination are induced by cellular and humoral immune responses specific to CNS antigens. They include diseases such as multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD), acute disseminated encephalomyelitis (ADEM) and anti-NMDA receptor encephalitis (NMDAR encephalitis). Over the years, many in vivo and in vitro models were used to study clinical, pathological, physiological and immunological features of these neuroimmunological disorders. Nevertheless, there are important aspects of human diseases that are not fully reproduced in the experimental models due to their technical limitations. In this review, we describe the preclinical models of neuroimmune disorders, and how they contributed to the understanding of these disorders and explore potential treatments. We also describe the purpose and limitation of each one, as well as the recent advances in this field.

Pediatric postviral autoimmune disorders of the CNS

Infections caused by various viruses, mainly belonging to the Herpesviridae family, can trigger the autoimmune process in the CNS in children. This can break brain immune tolerance and induce many molecular and cellular pathways of the immune response. This can lead to the appearance of neuronal auto-antibodies to intracellular, cell-surface or extracellular synaptic antigens. Children may also display a wide spectrum of neurological problems from encephalitis to obsessive–compulsive or tic disorders. In these cases, patients rarely respond to traditional treatment, based on antiviral or/and symptomatic drugs, but early immunotherapy is very effective. The implementation of routine immune tests in all children with acute neurological disorders should be recommended.

Autoimmune Encephalitis: NMDA Receptor Encephalitis as an Example of Translational Neuroscience

Autoimmune encephalitis (AE) is a group of disorders causing synaptic receptor dysfunction with a broad range of neurological symptoms that has been historically difficult to differentiate clinically. Today, AE represents an excellent example of the rapid determination of the cause of a disease and the ability to identify potential treatments using relatively simple basic science techniques of investigation. Of the number of autoimmune encephalitides identified thus far, one of the best examples of the impact of basic science studies on disease management is NMDA receptor mediated autoimmune encephalitis (NMDAr-AE). In this review, we will provide an overview of the epidemiology of NMDAr-AE, clinical features and treatments, and the basic science tools and techniques that were used to identify the cause, correlate symptoms to underlying pathophysiology, and to understand the mechanism of disease pathology.

Serum Systemic Autoantibodies in Anti-N-Methyl-D-Aspartate Receptor Encephalitis

Objective: The aim of this retrospective study was to investigate the relationship between serum systemic autoantibodies and anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis.

Methods: Thirty-nine patients with anti-NMDAR encephalitis were examined for serum systemic autoantibodies (antinuclear antibodies, extractable nuclear antigen autoantibodies, rheumatoid factors, and anti-neutrophil cytoplasmic antibodies), in comparison with 39 neuromyelitis optica spectrum disorder (NMOSD) and 78 healthy controls. Clinical features, cerebrospinal fluid characteristics, and outcomes were compared between the two subgroups of anti-NMDAR patients with positive and negative systemic autoantibodies, respectively.

Results: Anti-NMDAR encephalitis patients had higher frequency of positive serum systemic autoantibodies than healthy controls (23.1 vs. 2.6%, p = 0.001) and lower frequency than NMOSD (23.1 vs. 48.7%, p = 0.018). No patients were diagnosed comorbidities with non-organ-specific autoimmune diseases. Consciousness disturbance was more frequent in autoantibodies positive group than in the negative group (88.9 vs. 40.0%, p = 0.02). Autoantibody positive group had a poorer outcome than autoantibody negative group (55.6 vs. 86.7%, p = 0.043). There was a negative correlation between serum autoantibodies and outcomes in anti-NMDAR encephalitis patients (r = −0.325, p = 0.044).

Conclusion: Our data demonstrated serum systemic autoantibodies were more frequent in anti-NMDAR encephalitis patients than in healthy controls and less frequent than NMOSD, which were associated with higher severity of disease.

Paraneoplastic Diseases of the Central Nervous System

Paraneoplastic neurological syndromes are nonmetastatic complications of malignancy secondary to immune-mediated neuronal dysfunction or death. Pathogenesis may occur from cell surface binding of antineuronal antibodies leading to dysfunction of the target protein, or from antibodies binding against intracellular antigens which ultimately leads to cell death. There are several classical neurological paraneoplastic phenotypes including subacute cerebellar degeneration, limbic encephalitis, encephalomyelitis, and dorsal sensory neuropathy. The patient’s clinical presentations may be suggestive to the treating clinician as to the specific underlying paraneoplastic antibody. Specific antibodies often correlate with the specific underlying tumor type, and malignancy screening is essential in all patients with paraneoplastic neurological disease. Prompt initiation of immunotherapy is essential in the treatment of patients with paraneoplastic neurological disease, often more effective in cell surface antibodies in comparison to intracellular antibodies, as is removal of the underlying tumor.

Limbic encephalitis associated with AMPA receptor and CRMP5 antibodies: A case report and literature review

AIMS

AMPA receptor (AMPAR) and CRMP5 antibodies are relatively uncommon in limbic encephalitis, and patients with both antibodies are rare. We recently treated such a patient, but the patient died after active treatment. To further understand this disease, we conducted a case report and literature review.

DISCUSSIONS

To date, five encephalitis patients, including our patient, have been found to be positive for AMPAR and CRMP5 antibodies. The male-to-female ratio of the reported cases is 4:1, and the age range is 26 and 62 years old. All five patients presented with various neuropsychiatric symptoms, including insomnia, abnormal behavior, seizures, extrapyramidal symptoms, and autonomic dysfunction. Four patients had tumors (three invasive thymomas and one suspected lymphoma), and three cases died within a short period of time. No tumor was detected in one of the patients during the follow-up period; however, after active treatment, the outcome was poor, and the patient developed cachexia. One patient had good response to immunotherapy and tumor therapy and successfully returned to work.

CONCLUSIONS

The prognosis of encephalitis associated with AMPAR and CRMP5 antibodies is worse than that of the encephalitis associated with AMPAR antibodies alone. The most likely cause is that this encephalitis is more likely to be accompanied by malignant tumors, leading to a poor prognosis. In addition, it may also be due to some synergistic mechanisms between the two antibodies. Further studies aimed at the prognosis of this type of encephalitis are warranted.

Different FDG-PET metabolic patterns of anti-AMPAR and anti-NMDAR encephalitis: Case report and literature review

INTRODUCTION

¹⁸ F-fluorodeoxyglucose (FDG)-PET metabolic patterns of brain differ among autoimmune encephalitis with different neuronal surface antigens. In this case report, we compared the topographical relationship of cerebral glucose metabolism and antigen distribution in the patients with anti-NMDAR and anti-AMPAR encephalitis. Literature review summarized the common features of brain metabolism of autoimmune encephalitis.

METHODS

The cerebral glucose metabolism was evaluated by FDG-PET/CT during acute-to-subacute stage of autoimmune encephalitis and after treatment. The stereo and quantitative analysis of cerebral metabolism used standardized z-score and visualized on three-dimensional stereotactic surface projection. To map NMDAR and AMPAR in human brain, we adopted genetic atlases from the Allen Institute and protein atlases from Zilles's receptor densities.

RESULTS

The three-dimensional stereotactic surface projection displayed frontal-dominant hypometabolism in a 66-year-old female patient with anti-AMPAR encephalitis and occipital-dominant hypometabolism in a 29-year-old female patient with anti-NMDAR encephalitis. Receptor density maps revealed opposite frontal-occipital gradients of AMPAR and NMDAR, which reflect reduced metabolism in the correspondent encephalitis. FDG-PET hypometabolic areas possibly represent receptor hypofunction with spatial correspondence to receptor distributions of the autoimmune encephalitis. The reversibility of hypometabolism was in line with patients' cognitive improvement. The literature review summarized six features of metabolic anomalies of autoimmune encephalitis: (a) temporal hypermetabolism, (b) frontal hypermetabolism and (c) occipital hypometabolism in anti-NMDAR encephalitis, (d) hypometabolism in association cortices, (e) sparing of unimodal primary motor cortex, and (e) reversibility in recovery.

CONCLUSIONS

The distinct cerebral hypometabolic patterns of autoimmune encephalitis were representative for receptor hypofunction and topographical distribution of antigenic receptors. The reversibility of hypometabolism marked the clinical recovery of autoimmune encephalitis and made FDG-PET of brain a valuable diagnostic tool.

Associations of paediatric demyelinating and encephalitic syndromes with myelin oligodendrocyte glycoprotein antibodies: a multicentre observational study

BACKGROUND

Investigations of myelin oligodendrocyte glycoprotein (MOG) antibodies are usually focused on demyelinating syndromes, but the entire spectrum of MOG antibody-associated syndromes in children is unknown. In this study, we aimed to determine the frequency and distribution of paediatric demyelinating and encephalitic syndromes with MOG antibodies, their response to treatment, and the phenotypes associated with poor prognosis.

METHODS

In this prospective observational study, children with demyelinating syndromes and with encephalitis other than acute disseminated encephalomyelitis (ADEM) recruited from 40 secondary and tertiary centres in Spain were investigated for MOG antibodies. All MOG antibody-positive cases were included in our study, which assessed syndromes, treatment and response to treatment (ie, number of relapses), outcomes (measured with the modified Rankin scale [mRS]), and phenotypes associated with poor prognosis. We used Fisher's exact and Wilcoxon rank sum tests to analyse clinical features, and survival Cox regression to analyse time to antibody negativity.

FINDINGS

Between June 1, 2013, and Dec 31, 2018, 239 children with demyelinating syndromes (cohort A) and 296 with encephalitis other than ADEM (cohort B) were recruited. 116 patients had MOG antibodies, including 94 (39%) from cohort A and 22 (7%) from cohort B; 57 (49%) were female, with a median age of 6·2 years (IQR 3·7-10·0). Presenting syndromes in these 116 patients included ADEM (46 [68%]), encephalitis other than ADEM (22 [19%]), optic neuritis (20 [17%]), myelitis (13 [11%]), neuromyelitis optica spectrum disorders (six [5%]), and other disorders (nine [8%]). Among the patients with autoimmune encephalitis in cohort B (n=64), MOG antibodies were more common than all neuronal antibodies combined (22 [34%] vs 21 [33%]). After a median follow-up of 42 months (IQR 22-67), 33 (28%) of the 116 patients had relapses, including 17 (17%) of 100 diagnosed at first episode. Steroids, intravenous immunoglobulin, or plasma exchange were used in 100 (86%) patients at diagnosis, and 32 (97%) of 33 at relapses. Rituximab was mainly used at relapses (11 [33%]). 99 (85%) of 116 patients had substantial recovery (mRS <2) and 17 (15%) moderate to severe deficits (mRS >2; one died). Phenotypes of poor prognosis included ADEM-like relapses progressing to leukodystrophy-like features, and extensive cortical encephalitis evolving to atrophy. Time to antibody negativity was longer in patients with relapses (HR 0·18, 95% CI 0·05-0·59).

INTERPRETATION

The spectrum of paediatric MOG antibody-associated syndromes is wider than previously reported and includes demyelinating syndromes and encephalitis. Recognition of these disorders has important clinical and prognostic implications.

FUNDING

Mutua Madrileña Foundation; ISCIII-Subdirección General de Evaluación y Fomento de la Investigación Sanitaria; Fondo Europeo de Desarrollo Regional; Pediatrics Spanish Society; Departament de Salut, Generalitat de Catalunya; Marato TV3 Foundation; Red Española de Esclerosis Múltiple; La Caixa Foundation; and Fundació CELLEX.

In vivo Mechanisms of Antibody-Mediated Neurological Disorders: Animal Models and Potential Implications

Over the last two decades, the discovery of antibodies directed against neuronal surface antigens (NSA-Abs) in patients with different forms of encephalitis has provided a basis for immunotherapies in previously undefined disorders. Nevertheless, despite the circumstantial clinical evidence of the pathogenic role of these antibodies in classical autoimmune encephalitis, specific criteria need to be applied in order to establish the autoimmune nature of a disease. A growing number of studies have begun to provide proof of the pathogenicity of NSA-Abs and insights into their pathogenic mechanisms through passive transfer or, more rarely, through active immunization animal models. Moreover, the increasing evidence that NSA-Abs in the maternal circulation can reach the fetal brain parenchyma during gestation, causing long-term effects, has led to models of antibody-induced neurodevelopmental disorders. This review summarizes different methodological approaches and the results of the animal models of N-methyl-d-aspartate receptor (NMDAR), leucine-rich glioma-inactivated 1 (LGI1), contactin-associated protein 2 (CASPR2), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) antibody-mediated disorders and discuss the results and the limitations. We also summarize recent experiments that demonstrate that maternal antibodies to NMDAR and CASPR2 can alter development in the offspring with potential lifelong susceptibility to neurological or psychiatric disorders.

Human Cerebrospinal Fluid Monoclonal LGI1 Autoantibodies Increase Neuronal Excitability

OBJECTIVE

Leucine-rich glioma-inactivated 1 (LGI1) encephalitis is the second most common antibody-mediated encephalopathy, but insight into the intrathecal B-cell autoimmune response, including clonal relationships, isotype distribution, frequency, and pathogenic effects of single LGI1 antibodies, has remained limited.

METHODS

We cloned, expressed, and tested antibodies from 90 antibody-secreting cells (ASCs) and B cells from the cerebrospinal fluid (CSF) of several patients with LGI1 encephalitis.

RESULTS

Eighty-four percent of the ASCs and 21% of the memory B cells encoded LGI1-reactive antibodies, whereas reactivities to other brain epitopes were rare. All LGI1 antibodies were of IgG1, IgG2, or IgG4 isotype and had undergone affinity maturation. Seven of the overall 26 LGI1 antibodies efficiently blocked the interaction of LGI1 with its receptor ADAM22 in vitro, and their mean LGI1 signal on mouse brain sections was weak compared to the remaining, non-ADAM22-competing antibodies. Nevertheless, both types of LGI1 antibodies increased the intrinsic cellular excitability and glutamatergic synaptic transmission of hippocampal CA3 neurons in slice cultures.

INTERPRETATION

Our data show that the patients' intrathecal B-cell autoimmune response is dominated by LGI1 antibodies and that LGI1 antibodies alone are sufficient to promote neuronal excitability, a basis of seizure generation. Fundamental differences in target specificity and antibody hypermutations compared to the CSF autoantibody repertoire in N-methyl-D-aspartate receptor encephalitis underline the clinical concept that autoimmune encephalitides are very distinct entities. Ann Neurol 2020;87:405-418.