Autoimmune Encephalitis Resembling Dementia Syndromes

MR Imaging Findings in Anti-Leucine-Rich Glioma Inactivated Protein 1 Encephalitis: A Systematic Review and Meta-analysis

BACKGROUND

Antibodies against leucine-rich glioma inactivated protein 1 (LGI1) constitute a common form of autoimmune encephalitis. On MR imaging, it may show T2 FLAIR hyperintensities of the medial temporal lobe (T2 FLAIR-MTL), involve the basal ganglia, or be unremarkable.

PURPOSE

We performed a systematic review and meta-analysis to obtain prevalence estimates of abnormal findings on MR imaging in anti-LGI1 encephalitis. A human brain map of the LGI1 microarray gene expression was derived from the Allen Human Brain Atlas.

DATA SOURCES

PubMed and Web of Science were searched with the terms "LGI1" and "encephalitis" from inception to April 7, 2022.

STUDY SELECTION

Thirty-one research publications, encompassing case series and retrospective cohort and case-control studies, with >10 patients with anti-LGI1 encephalitis and MR imaging data were included.

DATA ANALYSIS

Pooled prevalence estimates were calculated using Freeman-Tukey double-arcsine transformation. Meta-analysis used DerSimonian and Laird random effects models.

DATA SYNTHESIS

Of 1318 patients in 30 studies, T2 FLAIR-MTL hyperintensities were present in 54% (95% CI, 0.48-0.60; I2 = 76%). Of 394 patients in 13 studies, 27% showed bilateral (95% CI, 0.19-0.36; I2 = 71%) and 24% unilateral T2 FLAIR-MTL abnormalities (95% CI, 0.17-0.32; I2 = 61%). Of 612 patients in 15 studies, basal ganglia abnormalities were present in 10% (95% CI, 0.06-0.15; I2 = 67%). LGI1 expression was highest in the amygdala, hippocampus, and caudate nucleus.

LIMITATIONS

Only part of the spectrum of MR imaging abnormalities in anti-LGI1 encephalitis could be included in a meta-analysis. MR imaging findings were not the main outcomes in most studies, limiting available information. I2 values ranged from 62% to 76%, representing moderate-to-large heterogeneity.

CONCLUSIONS

T2 FLAIR-MTL hyperintensities were present in around one-half of patients with anti-LGI1. The prevalence of unilateral and bilateral presentations was similar, suggesting unilaterality should raise the suspicion of this disease in the appropriate clinical context. Around 10% of patients showed basal ganglia abnormalities, indicating that special attention should be given to this region. LGI1 regional expression coincided with the most frequently reported abnormal findings on MR imaging. Regional specificity might be partially determined by expression levels of the target protein.

LGI1-antibody encephalitis: how to approach this highly treatable dementia mimic in memory and mental health services

Leucine-rich glioma-inactivated 1-antibody-encephalitis is a treatable and potentially reversible cause of cognitive and psychiatric presentations, and may mimic cognitive decline, rapidly progressive dementia and complex psychosis in older patients. This aetiology is of immediate relevance given the alternative treatment pathway required, compared with other conditions presenting with cognitive deficits.

Brain fog in central disorders of hypersomnolence: a review

Brain fog is an undefined term describing a cluster of symptoms related to fatigue and impaired memory, attention, and concentration. Brain fog or brain fog-like symptoms have been reported in central disorders of hypersomnolence and in a range of seemingly unrelated disorders, including coronavirus disease 2019, major depressive disorder, multiple sclerosis, lupus, and celiac disease. This narrative review summarizes current evidence and proposes a consensus definition for brain fog. Brain fog is prevalent in narcolepsy and idiopathic hypersomnia, with more than three-quarters of patients with either disorder reporting this symptom in a registry study; it has also been reported as particularly difficult to treat in idiopathic hypersomnia. Studies directly evaluating brain fog are rare; tools for evaluating this symptom cluster typically are patient reports, with few objective measures validated in any disorder. Evaluating brain fog is further complicated by confounding symptoms, such as excessive daytime sleepiness, which is a hallmark of hypersomnolence disorders. No treatments specifically address brain fog. The paucity of literature, assessment tools, and medications for brain fog highlights the need for research leading to better disambiguation and treatment. Until a clear consensus definition is established, we propose brain fog in hypersomnia disorders be defined as a cognitive dysfunction that may or may not be linked with excessive sleepiness, related to an underlying neuronal dysfunction, which reduces concentration and impairs information processing, leading to a complaint of lack of clarity of mental thinking and awareness.

CITATION

Rosenberg R, Thorpy MJ, Doghramji K, Morse AM. Brain fog in central disorders of hypersomnolence: a review. J Clin Sleep Med. 2024;20(4):643-651.

Incident anti-LGI1 autoimmune encephalitis during dementia with Lewy bodies: when Occam razor is a double-edged sword

In Dementia with Lewy bodies (DLB), rapid cognitive decline and seizures seldom complicate the typical clinical course. Nevertheless, concurrent, treatable conditions may be responsible. We report a case of DLB with superimposed anti-LGI1 encephalitis, emphasizing the importance of thorough diagnostic reasoning beyond the simplest explanation amid distinct clinical cues.

A Case Report and Literature Review on Positivity for Multiple Antibodies: Autoimmune Encephalitis in Focus

Autoimmune encephalitis (AE) is a group of neuropsychiatric disorders caused by antibodies that target the neuronal surface, synaptic, or intracellular antigens, impairing brain function. Although AE can affect people of different age groups, the occurrence of AE within specific age brackets depends on the specific type of AE and the antibodies produced. While AE is frequently considered a paraneoplastic syndrome linked to cancer, it is essential to acknowledge that the intensity of this association can vary depending on the specific antibody, leading to diverse relationships with paraneoplastic syndromes. Numerous cases have been recorded where AE manifests without an underlying malignancy. The diagnostic criteria for AE are characterized by a subacute deterioration of cognition, altered mental status, or psychiatric symptoms. Immunotherapy is recommended as a treatment for the condition, and the prognosis varies depending on the subtype. In this case, we present the case of an elderly woman who showed acute mental status changes, psychiatric symptoms, EEG alterations, and positive antibody results in both serum and CSF. Our case breaks new ground as the first documented instance of a female with positive serum anti-LGI 1, anti-AMPAR2, anti-Ri, and anti-CENP-A/B antibodies.

Prevalence, Clinical Profiles, and Prognosis of Stiff-Person Syndrome in a Japanese Nationwide Survey

BACKGROUND AND OBJECTIVES

To elucidate current epidemiologic, clinical, and immunologic profiles and treatments of stiff-person syndrome (SPS) in Japan.

METHODS

A nationwide mail survey was conducted using an established method. Data processing sheets were sent to randomly selected departments of internal medicine, neurology, pediatrics, psychiatry, and neurosurgery in hospitals and clinics throughout Japan to identify patients with SPS who were seen between January 2015 and December 2017.

RESULTS

Thirty cases were identified as glutamic acid decarboxylase 65 (GAD65)-positive SPS cases on the basis of detailed clinical data of 55 cases. Four patients had α1 subunit of glycine receptor (GlyR) antibodies, and 1 patient had both GAD65 and GlyR antibodies. The total estimated number of patients with GAD65-positive SPS was 140, and the estimated prevalence was 0.11 per 100,000 population. The median age at onset was 51 years (range, 26-83 years), and 23 (76%) were female. Of these, 70% had classic SPS, and 30% had stiff-limb syndrome. The median time from symptom onset to diagnosis was significantly longer in the high-titer GAD65 antibody group than in the low-titer group (13 months vs 2.5 months, p = 0.01). The median modified Rankin Scale (mRS) at baseline was 4, and the median mRS at the last follow-up was 2. Among the 29 GAD65-positive patients with ≥1 year follow-up, 7 received only symptomatic treatment, 9 underwent immunotherapy without long-term immunotherapy, and 13 received long-term immunotherapy such as oral prednisolone. The coexistence of type 1 diabetes mellitus and the lack of long-term immunotherapy were independent risk factors for poor outcome (mRS ≥3) in the GAD65-positive patients (odds ratio, 15.0; 95% CI 2.6-131.6; p = 0.001; odds ratio, 19.8; 95% CI 3.2-191.5; p = 0.001, respectively).

DISCUSSION

This study provides the current epidemiologic and clinical status of SPS in Japan. The symptom onset to the diagnosis of SPS was longer in patients with high-titer GAD65 antibodies than in those with low-titer GAD65 antibodies. The outcome of patients with SPS was generally favorable, but more aggressive immunotherapies are necessary for GAD65-positive patients with SPS.

The Neuropsychiatric Side of Cerebral Venous Thrombosis: A Case of Delirium and Catatonia

We report a patient with cerebral venous thrombosis who initially presented with psychosis and who then progressed to delirium and catatonia within a few days. Upon treatment and resolution of the thrombosis, she presented complete remission of the psychiatric disturbances. This case highlights a specific neuropsychiatric presentation of cerebral venous thrombosis involving psychosis, catatonia, and delirium, which, to our best knowledge, has not been reported in the neurological or psychiatric literature. However, it reminds us of mental status and behavioral abnormalities which are not infrequent features of cerebral venous thrombosis. This leads to a discussion regarding the psychopathology, etiology, and pathophysiology of the case.

Distinct phenotypes in a cohort of anti-CASPR2 associated neurological syndromes

INTRODUCTION

Anti-contactin-associated protein-like 2 (CASPR2) is classically associated with limbic encephalitis (LE), Morvan syndrome and peripheral nerve hyperexcitability (PNH). Additional clinical features have been previously recognized.

OBJECTIVE

To describe a cohort of patients with anti-CASPR2-associated neurological syndromes from a tertiary referral centre.

METHODS

Retrospective analysis of patients with positive serum anti-CASPR2 antibodies in the period between 2014 and 2021.

RESULTS

Nineteen patients were identified, 11 (57.9%) male, with a median age at symptom onset of 49.0 (31.3-63.0) years and a median time to diagnosis of 1.0 (0.0-1.8) years. The most common clinical syndromes were LE (7 cases, 36.8%), Morvan syndrome (4, 21.1%) and PNH (2, 10.5%). Six patients presented with atypical phenotypes (31.6%), comprising dysautonomia (orthostatic hypotension and Adie's Pupil), motor tics/stereotypies, obsessive-compulsive disorder, and brainstem involvement. The most common presenting symptoms were seizures (31.6%), PNH (21.1%) and cognitive dysfunction (15.8%). One LE patient had a disease duration of 2,5 years and was initially diagnosed with dementia. CSF was normal in most cases. Brain MRI showed temporal lobe hyperintensities in 4 LE cases (57.1%). All PNH cases had myokymic discharges of fasciculations in the electromyography. Two patients had associated thymoma and 1 had lung adenocarcinoma. Eight patients (42.1%) received treatment during the acute phase and 26.3% maintenance treatment. Approximately half of the treated cases improved or stabilised, with 4 (21.1%) deaths in the whole cohort.

CONCLUSION

Anti-CASPR2-associated neurological disorders may present with isolated atypical phenotypes, a slowly progressive clinical course, and with normal CSF or imaging findings.

Brazilian autoimmune encephalitis network (BrAIN): antibody profile and clinical characteristics from a multicenter study

Background

The frequency of antibodies in autoimmune encephalitis (AIE) may vary in different populations, however, data from developing countries are lacking. To describe the clinical profile of AIE in Brazil, and to evaluate seasonality and predictors of AIE in adult and pediatric patients.

Methods

We evaluated patients with possible AIE from 17 centers of the Brazilian Autoimmune Encephalitis Network (BrAIN) between 2018 and 2022. CSF and serum were tested with TBAs and CBAs. Data on clinical presentation, complementary investigation, and treatment were compiled. Seasonality and predictors of AIE in adult and pediatric populations were analyzed.

Results

Of the 564 patients, 145 (25.7%) were confirmed as seropositive, 69 (12.23%) were seronegative according to Graus, and 58% received immunotherapy. The median delay to diagnosis confirmation was 5.97 ± 10.3 months. No seasonality variation was observed after 55 months of enrolment. The following antibodies were found: anti-NMDAR (n=79, 54%), anti-MOG (n=14, 9%), anti-LGI1(n=12, 8%), anti-GAD (n=11, 7%), anti-GlyR (n=7, 4%), anti-Caspr2 (n=6, 4%), anti-AMPAR (n=4, 2%), anti-GABA-BR (n=4, 2%), anti-GABA-AR (n=2, 1%), anti-IgLON5 (n=1, 1%), and others (n=5, 3%). Predictors of seropositive AIE in the pediatric population (n=42) were decreased level of consciousness (p=0.04), and chorea (p=0.002). Among adults (n=103), predictors of seropositive AIE were movement disorders (p=0.0001), seizures (p=0.0001), autonomic instability (p=0.026), and memory impairment (p=0.001).

Conclusion

Most common antibodies in Brazilian patients are anti-NMDAR, followed by anti-MOG and anti-LGI1. Only 26% of the possible AIE patients harbor antibodies, and 12% were seronegative AIE. Patients had a 6-month delay in diagnosis and no seasonality was found. Findings highlight the barriers to treating AIE in developing countries and indicate an opportunity for cost-effect analysis. In this scenario, some clinical manifestations help predict seropositive AIE such as decreased level of consciousness, chorea, and dystonia among children, and movement disorders and memory impairment among adults.

Antibodies Associated With Autoimmune Encephalitis in Patients With Presumed Neurodegenerative Dementia

BACKGROUND & OBJECTIVES

Autoimmune encephalitis (AIE) may present with prominent cognitive disturbances without overt inflammatory changes in MRI and CSF. Identification of these neurodegenerative dementia diagnosis mimics is important because patients generally respond to immunotherapy. The objective of this study was to determine the frequency of neuronal antibodies in patients with presumed neurodegenerative dementia and describe the clinical characteristics of the patients with neuronal antibodies.

METHODS

In this retrospective cohort study, 920 patients were included with neurodegenerative dementia diagnosis from established cohorts at 2 large Dutch academic memory clinics. In total, 1,398 samples were tested (both CSF and serum in 478 patients) using immunohistochemistry (IHC), cell-based assays (CBA), and live hippocampal cell cultures (LN). To ascertain specificity and prevent false positive results, samples had to test positive by at least 2 different research techniques. Clinical data were retrieved from patient files.

RESULTS

Neuronal antibodies were detected in 7 patients (0.8%), including anti-IgLON5 (n = 3), anti-LGI1 (n = 2), anti-DPPX, and anti-NMDAR. Clinical symptoms atypical for neurodegenerative diseases were identified in all 7 and included subacute deterioration (n = 3), myoclonus (n = 2), a history of autoimmune disease (n = 2), a fluctuating disease course (n = 1), and epileptic seizures (n = 1). In this cohort, no patients with antibodies fulfilled the criteria for rapidly progressive dementia (RPD), yet a subacute deterioration was reported in 3 patients later in the disease course. Brain MRI of none of the patients demonstrated abnormalities suggestive for AIE. CSF pleocytosis was found in 1 patient, considered as an atypical sign for neurodegenerative diseases. Compared with patients without neuronal antibodies (4 per antibody-positive patient), atypical clinical signs for neurodegenerative diseases were seen more frequently among the patients with antibodies (100% vs 21%, p = 0.0003), especially a subacute deterioration or fluctuating course (57% vs 7%, p = 0.009).

DISCUSSION

A small, but clinically relevant proportion of patients suspected to have neurodegenerative dementias have neuronal antibodies indicative of AIE and might benefit from immunotherapy. In patients with atypical signs for neurodegenerative diseases, clinicians should consider neuronal antibody testing. Physicians should keep in mind the clinical phenotype and confirmation of positive test results to avoid false positive results and administration of potential harmful therapy for the wrong indication.

Efficacy of immunotherapy and prognosis in anti-LGI1 encephalitis patients: A meta-analysis

OBJECTIVE

To assess the efficacy and safety of immunotherapy for LGI1 antibody encephalitis, and consider the predictors of poor outcomes following immunotherapy.

METHODS

We searched PubMed and Embase for articles reporting the immunotherapy data of anti-LGI1 encephalitis patients. The proportions of patients with poor outcomes (modified Rankin Scale [mRS] score > 2) at 3 months, 12 months, and the last follow-up, as well as the odds ratio [OR] of predictors were pooled.

RESULTS

The review included 162 articles with 1066 patients. The proportion of patients with poor functional outcomes was 21% at 3 months, 14% at 12 months, and 14% at the last follow-up after receiving immunotherapy. The proportion of patients with reported relapse was 16.6%. The mean duration from onset to the first relapse was 15.6 months. Predictors significantly associated with poor outcomes were age (increase of 1 year), the presence of cognitive impairment, and CSF LGI1 antibody positive. We did not find a statistically significant association between the worst mRS score in the acute phase, the presence of faciobrachial dystonic seizures (FBDS), days from symptom onset to immunotherapy, second-line treatment, maintenance immunotherapy, or follow-up time and outcomes.

INTERPRETATION

Although most patients respond to immunotherapy, a minority of patients still have poor outcomes. Advanced age, cognitive impairment, and CSF LGI1 antibody positive are associated with an increased risk of poor outcomes. However, due to the insufficiency of the data, these conclusions need to be interpreted with caution.

Cerebrospinal fluid biomarkers in psychiatric autoimmune encephalitis: a retrospective cohort study

Background

Psychiatric autoimmune encephalitis (pAE) is a growing field of interest in diagnosis and therapy in psychiatric hospitals and institutions. This study investigates the relevant extent to which there are potential biomarkers in cerebrospinal fluid (CSF) that can differentiate against a cohort with neurodegenerative disease.

Methods

We included in this study a total of 27 patients with possible and definite psychiatric autoimmune encephalitis and compared with a cohort with CSF-based AD (n = 27) different biomarkers in CSF such as lactate, cell count, % lymphocytes, % monocytes, total protein content, albumin, immunoglobulins G (IgG), M (IgM) and A (IgA), CSF/serum albumin ratio, CSF/serum IgG ratio, CSF/serum IgA ratio, intrathecal IgG synthesis, blood-brain barrier disruption, specific antibody synthesis for measles, rubella, herpes simplex virus, varicella zoster virus, Ebstein-Barr virus and cytomegalovirus, total tau protein (t-tau), phosphorylated tau protein 181 (p-tau181), amyloid beta 42 (Aß42), amyloid beta 40 (Aß40) and the amyloid beta 42/ amyloid beta 40 (Aß42/40) ratio.

Results

The p-tau 181 was elevated above cut-off values in both possible pAE and AD. However, in definitive pAE, p-tau181 levels were not elevated. When elevated p-tau181 levels in possible AE were compared with those in AD, we found relevant differences, such as a relative increase in p-tau181 in AD patients. Elevated p-tau181 levels were detected in possible psychiatric AEs with IgLON5, glycine, recoverin, titin, and nonspecific neuropil antibodies in serum and IgLON5, titin, Yo, and nonspecific neuropil autoantibodies in CSF. In addition, we detected elevated levels of p-tau181 and IgLON5 autoantibodies in serum and CSF, and Yo autoantibodies in CSF in patients with definitive pAE. Interestingly, we observed a higher CSF/serum IgM ratio in possible and definitive pAE than in AD patients.

Conclusion

Our results suggest that neuroaxonal brain damage may occur in specific psychiatric AEs associated with IgLON5, glycine, recoverin, and titin autoantibodies. Further research should focus on the CSF/serum IgM ratio as an early marker of autoantibody production in pAE compared to AD as a potential biomarker for differential diagnosis.

Immunoreactivity to astrocytes in different forms of dementia: High prevalence of autoantibodies to GFAP

Objective

To study the prevalence of autoantibodies to glial and neuronal antigens with a focus on glial acidic fibrillary protein (GFAP) in patients with dementia.

Methods

Sera of 127 patients with different forms of dementia and sera of 82 age-matched patients with various neurological diseases except for dementia, as well as sera from 15 age-matched healthy controls were analyzed for anti-glial or anti-neuronal IgG using 1) primary murine embryonic hippocampus cell cultures, 2) murine brain sections, 3) immunoblotting on mouse brain homogenates and 4) astrocyte cultures. Sera reacting with astrocytes in hippocampus cell cultures were further analyzed using HEK293 cells transfected with human GFAP.

Results

IgG in serum from 45 of 127 (35.5%) patients with dementia but only 8 of 97 (8.2%, p ≤ 0.001) controls bound to either glial or neuronal structures in cultured murine hippocampus cells. In these cultures antibodies to astrocytes were detected in 35 of 127 (27.5%) of the dementia patients, whereas in controls antibodies to astrocytes were detected in 4 sera only (4.1%, p ≤ 0.001). Among the sera exhibiting reactivity to astrocytes, 14 of 35 (40%) showed immunoreaction to HEK293 cells transfected with GFAP in dementia patients, representing 11% of all sera. Within the 4 immunoreactive control sera reacting with astrocytes one reacted with GFAP (1.0% of total immunoreactivity, p = 0.003).

Conclusions

Autoantibodies to glial epitopes in general and to GFAP in particular are more frequent in patients with dementia than in age-matched controls without dementia, thus indicating the need for further investigations regarding the potential pathophysiological relevance of these antibodies.

Blood biomarkers for Alzheimer's disease in clinical practice and trials

Blood-based biomarkers hold great promise to revolutionize the diagnostic and prognostic work-up of Alzheimer's disease (AD) in clinical practice. This is very timely, considering the recent development of anti-amyloid-β (Aβ) immunotherapies. Several assays for measuring phosphorylated tau (p-tau) in plasma exhibit high diagnostic accuracy in distinguishing AD from all other neurodegenerative diseases in patients with cognitive impairment. Prognostic models based on plasma p-tau levels can also predict future development of AD dementia in patients with mild cognitive complaints. The use of such high-performing plasma p-tau assays in the clinical practice of specialist memory clinics would reduce the need for more costly investigations involving cerebrospinal fluid samples or positron emission tomography. Indeed, blood-based biomarkers already facilitate identification of individuals with pre-symptomatic AD in the context of clinical trials. Longitudinal measurements of such biomarkers will also improve the detection of relevant disease-modifying effects of new drugs or lifestyle interventions.

Clinical Correlates of Cerebrospinal Fluid 14-3-3 Protein in Non-Prion Rapid Progressive Dementia

BACKGROUND

The 14-3-3 protein in cerebrospinal fluid (CSF) is a suitable biomarker for the diagnosis of Creutzfeldt-Jakob disease (CJD). However, it has also been detected in various non-prion-related rapidly progressive dementia (RPD), which affected its diagnostic performance and clinical utilization.

OBJECTIVE

To investigate the general disease distribution with positive 14-3-3 result and to evaluate the association between CSF 14-3-3 protein and the clinical features in patients with non-prion RPD.

METHODS

A total of 150 patients with non-prion RPD were enrolled. The clinical data were collected and CSF 14-3-3 test was performed for all patients. The distribution of various diseases with a positive 14-3-3 result was analyzed and the association of CSF 14-3-3 with clinical features was tested.

RESULTS

The CSF 14-3-3 protein was detected in 23.3% of non-prion RPD patients, and the most frequent diagnoses were autoimmune encephalitis (22.9%) and neurodegenerative disease (22.9%). CSF 14-3-3 protein was more common in older patients (p = 0.028) and those presenting myoclonus (p = 0.008). In subgroup analysis, the positive 14-3-3 test was more common in neurodegenerative disease with a long time from the symptom onset to CSF 14-3-3 test (p = 0.014).

CONCLUSION

CSF 14-3-3 protein could be detected in a broad spectrum of non-prion RPD. In particular, patients with autoimmune encephalitis and rapidly progressive neurodegenerative diseases and those with myoclonus have a greater likelihood of a positive 14-3-3 result. These results could help clinicians interpret the results of CSF 14-3-3 protein more reasonably.

Hashimoto Encephalopathy of a Middle-Aged Man With Progressive Symptoms of Dementia

Autoimmune encephalitis is caused by immunological reactions showing unconsciousness, agitation, and other neurological symptoms. Autoimmune diseases can be related to autoantibodies, causing encephalitis. These autoantibody-related encephalitides could appear in various clinical courses. As laboratory tests for detecting these antibodies are limited, diagnosis is difficult. Hashimoto’s encephalopathy is autoimmune encephalitis caused by antibodies against the thyroid gland. This time, we experienced a case of a 69-year-old man with a chief complaint of subacute progression of amnesia and suspected autoimmune encephalitis, who was finally diagnosed with Hashimoto’s encephalopathy in a rural community hospital. In this case, clinicians should consider Hashimoto's encephalopathy as a differential diagnosis and measure antithyroid antibodies when acute or subacute onset cognitive impairment is observed in middle-aged patients. As a super-aging society significantly affects community hospitals, general physicians need to start treatments for encephalopathy and encephalitis when clinicians suspect the disease and rule out other critical diseases.

Psychiatric manifestations of autoimmune encephalitis

Autoimmune encephalitis is increasingly recognized as a cause of psychiatric symptoms. A wide spectrum of psychiatric manifestations have been described which may precede, follow or occur independently of neurologic features. Patients typically respond to immunotherapy, however diagnosis is challenging due to phenotypic heterogeneity. The aim of this review is to provide an overview of the psychiatric features associated with encephalitis mediated by autoantibodies targeting neuronal cell-surface antigens and describe indicators of potential immunopathology underlying psychiatric manifestations.

Novel qEEG Biomarker to Distinguish Anti-NMDAR Encephalitis From Other Types of Autoimmune Encephalitis

Objective

To establish the diagnostic biomarker of electroencephalogram (EEG) to distinguish between anti-N-methyl-d-aspartate receptor encephalitis (NMDARE) and other types of autoimmune encephalitis (other AEs).

Methods

We reviewed the clinical records of 90 patients with acute encephalitis who were treated in our institution between January 2014 and October 2020. We enrolled the patients who fulfilled the diagnostic criteria for possible AE (pAE) defined by Graus et al. (pAE criteria) and then classified into definite NMDARE and other AEs. We investigated the main syndrome and analyzed all admission EEGs using EEG power value (PV). Statistical significance was tested using the Mann–Whitney U test or Fisher’s exact test.

Results

Twenty-five patients fulfilled the pAE criteria and were classified into 9 with definite NMDARE (median age: 21 years; 8 women) and 12 with other AEs (median age: 37.5 years; 6 women). Four were eventually excluded. Speech dysfunction (9/9 vs. 4/12, p = 0.005) and movement disorders (6/9 vs. 1/12, p = 0.016) were more frequent in NMDARE than in other AEs. The PV analyses revealed the novel quantitative EEG (qEEG) index, namely, fast slow ratio (FSR) (PV of total beta/PV of total theta + delta). The median FSR (0.139 vs. 0.029, p = 0.004) was higher for NMDARE than other AEs, and the receiver operating characteristic curve area of FSR was 0.86 (95% CI 0.70–1.00). A cutoff value of 0.047 yielded a specificity of 0.75 and a sensitivity of 1.00. Focusing on patients who did not meet the “probable NMDARE criteria” in Graus 2016 (proNMDARE criteria) (n = 10), the pretest probability of NMDAR antibody test was 0.30 (3/10), which increased in patients with an FSR greater than the cutoff (n = 5) to 0.60 (3/5).

Conclusions

The NMDARE group highlighted speech dysfunction and movement disorders, and a novel qEEG index FSR accurately distinguished the NMDARE patients from other AEs. The FSR is a promising diagnostic marker for NMDARE that indicates the positive results of NMDAR antibodies in patients with AE when combined with the proNMDARE criteria.

A critical review and update on autoimmune encephalitis: understanding the alphabet soup

Autoimmune encephalitis (AE) comprises a group of diseases mediated by antibodies against neuronal cell surface or synaptic antigens, such as ion channels or neurotransmitter receptors. New clinical syndromes and their associated antibodies were and are still being characterized over the last two decades. The fact that their main clinical features are interdisciplinary, - encompassing neuropsychiatric symptoms, cognitive dysfunction, epileptic seizures, movement and sleep disorders - has led to a surge of interest in this field. Some of these diseases present with a well-defined syndrome, being recognizable on clinical grounds. Correct diagnosis is important since AE are potentially treatable diseases, despite their severity. On the other hand, an increasing number of neuronal antibodies being described casts doubt upon the way we should utilize antibody testing and interpret results. In this article we review, summarize and update the current knowledge on antibody mediated encephalitis.

Antibody Therapies in Autoimmune Encephalitis

Autoimmune encephalitis (AE) comprises a heterogeneous group of disorders in which the host immune system targets self-antigens expressed in the central nervous system. The most conspicuous example is an anti-N-methyl-D-aspartate receptor encephalitis linked to a complex neuropsychiatric syndrome. Current treatment of AE is based on immunotherapy and has been established according to clinical experience and along the concept of a B cell-mediated pathology induced by highly specific antibodies to neuronal surface antigens. In general, immunotherapy for AE follows an escalating approach. When first-line therapy with steroids, immunoglobulins, and/or plasma exchange fails, one converts to second-line immunotherapy. Alkylating agents could be the first choice in this stage. However, due to their side effect profile, most clinicians give preference to monoclonal antibodies (mAbs) directed at B cells such as rituximab. Newer mAbs might be added as a third-line therapy in the future, or be given even earlier if shown effective. In this chapter, we will discuss mAbs targeting B cells (rituximab, ocrelizumab, inebulizumab, daratumumab), IL-6 (tocilizumab, satralizumab), the neonatal Fc receptor (FCRn) (efgartigimod, rozanolixizumab), and the complement cascade (eculizumab).

Rapidly progressive dementia: Extending the spectrum of GFAP-astrocytopathies?

Autoimmune glial fibrillary acidic protein astrocytopathy (GFAP-A) is a steroid-responsive meningoencephalomyelitis, sometimes presenting with atypical clinical signs such as movement disorders or psychiatric and autonomic features. Beyond clinical presentation and imaging, diagnosis relies on detection of GFAP-antibodies (AB) in CSF. Using quantitative behavioral, serologic, and immunohistochemical analyses, we characterize two patients longitudinally over 18-24 months who presented with rapidly progressive neurocognitive deterioration in the context of GFAP-AB in CSF and unremarkable cranial MRI studies. Intensified immunotherapy was associated with clinical stabilization. The value of GFAP-AB screening in selected cases of rapidly progressive dementias is discussed.

Clinical Features and Therapeutic Effects of Anti-leucine-rich Glioma Inactivated 1 Encephalitis: A Systematic Review

Background: Clinical presentations and treatment programs about anti-leucine-rich glioma inactivated 1 (LGI1) encephalitis still remain incompletely understood. Objective: This study analyzed the clinical features and therapeutic effects of anti-LGI1 encephalitis. Methods: PubMed, EMBASE, and the Cochrane Library were searched to identify published English and Chinese articles until April 2021. Data were extracted, analyzed, and recorded in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Results: A total of 80 publications detailing 485 subjects matched our inclusion criteria. Short-term memory loss (75.22%), faciobrachial dystonic seizures (FBDS) (52.53%), other seizures excluding FBDS (68.48%), psychiatric symptoms (57.67%), and sleep disturbances (34.30%) were the most frequently described symptoms in anti-LGI1 encephalitis. Hyponatremia (54.90%) was the most common hematologic examination change. The risk of incidence rate of malignant tumors was higher than in healthy people. The positive rate of anti-LGI1 in serum (99.79%) was higher than CSF (77.38%). Steroids (93.02%), IVIG (87.50%), and combined use (96.67%) all had a high remission rate in the initial visit. A total of 35 of 215 cases relapsed, of which 6/35 (17.14%) did not use first-line treatment, and 21 (60.00%) did not maintain long-term treatment. Plasma exchange (PE) could be combined in severe patients, immunosuppressant could be used for refractory patients or for recurrence and using an anti-epileptic drug to control seizures may benefit cognition. Conclusions: Short-term memory loss, FBDS, psychiatric symptoms, and hyponatremia were key features in identifying anti-LGI1 encephalitis. Serum and CSF antibody tests should be considered in diagnosis criteria. Steroids with IVIG should be recommended, PE was combined for use in severe patients, immunosuppressant therapy might improve outcomes if recurrence or progression occurred, and control seizures might benefit cognition. The useful ways to reduce relapse rate were early identification, clear diagnosis, rapid treatment, and maintaining long-term treatment. The follow-up advice was suggested according to the research of paraneoplastic syndrome, and concern about tumors was vital as well.