Autoimmune Encephalitis: Pathophysiology and Imaging Review of an Overlooked Diagnosis

Autoimmune encephalitis: Early and late findings on serial MR imaging and correlation to treatment timepoints

Introduction

MRI is negative in a large percentage of autoimmune encephalitis cases or lacks findings specific to an antibody. Even rarer is literature correlating the evolution of imaging findings with treatment timepoints. We aim to characterize imaging findings in autoimmune encephalitis at presentation and on follow up correlated with treatment timepoints for this rare disease.

Methods

A full-text radiological information system search was performed for "autoimmune encephalitis" between January 2012 and June 2022. Patients with laboratory-identified autoantibodies were included. MRI findings were assessed in correlation to treatment timepoints by two readers in consensus. For statistical analysis, cell-surface vs intracellular antibody groups were assessed for the presence of early limbic, early extralimbic, late limbic, and late extralimbic findings using the χ2 test.

Results

Thirty-seven patients (female n = 18, median age 58.8 years; range 25.7 to 82.7 years) with 15 different autoantibodies were included in the study. Twenty-three (62%) patients were MRI-negative at time of presentation; 5 of these developed MRI findings on short-term follow up. Of the 19 patients with early MRI findings, 9 (47%) demonstrated improvement upon treatment initiation (7/9 cell-surface group). There was a significant difference (p = 0.046) between the MRI spectrum of cell-surface vs intracellular antibody syndromes as cell-surface antibody syndromes demonstrated more early classic findings of limbic encephalitis and intracellular antibody syndromes demonstrated more late extralimbic abnormalities.

Conclusion

MRI can be used to help narrow the differential diagnosis in autoimmune encephalitis and can be used as a monitoring tool for certain subtypes of this rare disease.

Features of the clinical course of Autoimmune Encephalitis Associated with various antibodies

Despite the increasing incidence of autoimmune encephalitis and the incomplete recovery observed in patients post-affliction, the issue of timely diagnosis remains unresolved. The primary objective of this study is identification the distinctive clinical presentation features evaluation the management strategies, and assess the outcomes of the disease in patients with various forms of autoimmune encephalitis. The research aims to contribute in a better understanding of the disease progression and facilitate the selection of optimal therapeutic interventions. A retrospective observational study enrolled 68 patients aged 18 years and older with verified autoimmune encephalitis who underwent treatment in state hospitals in Sofia, Bulgaria, from the beginning of 2014 to the end of 2022. The number of patients with pathology linked to antibodies against glycine receptors (Gly-R) was half as much, with 32 and 17 patients, respectively. The primary manifestations of autoimmune encephalitis included cognitive impairments observed in 51 patients, seizures occurring in 44 patients, and mood disorders observed in 22 patients. While the findings of imaging studies were nonspecific, hospitalizations for patients with this pathology, especially those with antibodies to CASPR2 and DPPX, were prolonged (114 and 232 days, respectively). In the vast majority of cases, incomplete recovery with residual symptoms was noted. Among the diverse forms of autoimmune encephalitis, the most prevalent is NMDA-R. Cognitive impairments predominate in the autoimmune encephalitis clinical presentation. Prolonged hospitalization periods and incomplete recovery of patients are characteristic features of autoimmune encephalitis, despite combined therapy involving intravenous administration of methylprednisolone and immunoglobulins.

Uncommon and Miscellaneous Inflammatory Disorders of the Brain and Spine

Inflammatory disorders of the brain and spine have a highly variable MRI appearance, often demonstrating significant overlap in imaging features. The resulting diagnostic dilemma is particularly challenging when considering the more uncommon neuroinflammatory entities. Diligent examination of the salient clinical presentation and signal alteration on imaging examination is necessary when considering neuroinflammation as a diagnostic possibility and may aid in raising suspicion for a particular neuroinflammatory entity. This article reviews a selection of uncommon and miscellaneous inflammatory disorders of the brain and spine to raise awareness of the clinical and imaging features that may assist in this challenging diagnostic task.

Autoimmune encephalitis: what the radiologist needs to know

Autoimmune encephalitis is a relatively novel nosological entity characterized by an immune-mediated damage of the central nervous system. While originally described as a paraneoplastic inflammatory phenomenon affecting limbic structures, numerous instances of non-paraneoplastic pathogenesis, as well as extra-limbic involvement, have been characterized. Given the wide spectrum of insidious clinical presentations ranging from cognitive impairment to psychiatric symptoms or seizures, it is crucial to raise awareness about this disease category. In fact, an early diagnosis can be dramatically beneficial for the prognosis both to achieve an early therapeutic intervention and to detect a potential underlying malignancy. In this scenario, the radiologist can be the first to pose the hypothesis of autoimmune encephalitis and refer the patient to a comprehensive diagnostic work-up - including clinical, serological, and neurophysiological assessments.In this article, we illustrate the main radiological characteristics of autoimmune encephalitis and its subtypes, including the typical limbic presentation, the features of extra-limbic involvement, and also peculiar imaging findings. In addition, we review the most relevant alternative diagnoses that should be considered, ranging from other encephalitides to neoplasms, vascular conditions, and post-seizure alterations. Finally, we discuss the most appropriate imaging diagnostic work-up, also proposing a suggested MRI protocol.

The split apparent diffusion coefficient sign: A novel magnetic resonance imaging biomarker for cortical pathology with possible implications in autoimmune encephalitis

INTRODUCTION

MRI is the imaging modality of choice for assessing patients with encephalopathy. In this context, we discuss a novel biomarker, the "split ADC sign," where the cerebral cortex demonstrates restricted diffusion (high DWI signal and low ADC) and the underlying white matter demonstrates facilitated diffusion (high or low DWI signal and high ADC). We hypothesize that this sign can be used as a biomarker to suggest either acute encephalitis onset or to raise the possibility of an autoimmune etiology.

MATERIALS AND METHODS

A full-text radiological information system search of radiological reports was performed for all entities known to produce restricted diffusion in the cortex excluding stroke between January 2012 and June 2022. Initial MRI studies performed upon onset of clinical symptoms were screened for the split ADC sign.

RESULTS

25 subjects were encountered with a positive split ADC sign (15 female; median age = 57 years, range 18-82). Diagnosis included six herpes simplex encephalitis, three peri-ictal MRI changes, eight PRES, two MELAS, and six autoimmune (3 anti-GABAAR, two seronegative, and one anti-Ma2/Ta). Subjects were imaged at a mean 1.8 days after the onset of symptoms (range 0-8).

DISCUSSION

We present a novel visual MRI biomarker, the split ADC sign, and highlight its potential usefulness in subjects with encephalopathy to suggest acute disease onset or to raise the possibility of an autoimmune etiology when location-based criteria are applied. When positive, the sign was present on the initial MRI and can therefore be used to help focus further clinical and laboratory workup.

Unusual imaging findings associated with abdominal pediatric germ cell tumors

Germ cell tumors of childhood are tumors arising from germline cells in gonadal or extragonadal locations. Extragonadal germ cell tumors are characteristically located in the midline, arising intracranially or in the mediastinum, retroperitoneum, or pelvis. These tumors are generally easily diagnosed due to typical sites of origin, characteristic imaging findings, and laboratory markers. However, germ cell tumors can be associated with unusual clinical syndromes or imaging features that can perplex the radiologist. This review will illustrate atypical imaging/clinical manifestations and complications of abdominal germ cell tumors in childhood. These features include unusual primary tumors such as multifocal primaries; local complications such as ovarian torsion or ruptured dermoid; atypical presentations of metastatic disease associated with burned-out primary tumor, growing teratoma syndrome, and gliomatosis peritonei; endocrine manifestations such as precocious puberty and hyperthyroidism; and antibody mediated paraneoplastic syndrome such as anti-N-methyl-D-aspartate-receptor antibody-mediated encephalitis. This review aims to illustrate unusual imaging features associated with the primary tumor, metastatic disease, or distant complications of abdominal germ cell tumors of childhood.

Case report: Successful treatment of an anti-D2R and DPPX antibody-associated autoimmune encephalitis patient with high-dose methylprednisolone and intravenous immunoglobulin

Background

Autoimmune encephalitis is a neurological condition caused by abnormal immune responses, manifesting as cognitive impairments, behavioral abnormalities, and seizures. Its diagnosis depends on the detecting neuronal surface antibodies in serum or cerebrospinal fluid. Despite recent advances in understanding, clinical recognition remains challenging, especially with rare antibodies such as anti-dopamine D2 receptor (D2R) and anti-dipeptidyl-peptidase-like protein 6 (DPPX) antibodies. Delayed diagnosis can lead to severe complications. This case presentation emphasizes the diagnostic intricacies and effective treatment of the anti-D2R and DPPX antibody-associated autoimmune encephalitis.

Case description

The patient presented with a 3-day history of fatigue and limb soreness followed by a 3-h episode of confusion and limb convulsions. Upon admission to our facility, the initial diagnosis included status epilepticus, aspiration pneumonia, metabolic acidosis, respiratory alkalosis, and suspected encephalitis. Despite receiving antiepileptic, anti-infection, and antivirus therapy, the patient's condition deteriorated. Both computed tomography (CT) scan and magnetic resonance imaging (MRI) of the brain showed no significant abnormalities. No pathogen was identified in the cerebrospinal fluid (CSF). However, further CSF and serum examination revealed positive results of anti-D2R and anti-DPPX antibodies, confirming a diagnosis of anti-D2R and DPPX antibody-associated autoimmune encephalitis. The patient underwent a comprehensive treatment regimen, including high-dose methylprednisolone pulse therapy combined with intravenous immunoglobulin (IVIG), antiviral and anti-infection treatments, and antiepileptic medications. Significant clinical improvement was observed, and by the 18th day of admission, the patient was stable and coherent.

Conclusions

The current patient represents the first reported case of double-positive autoimmune encephalitis for anti-D2R and DPPX antibodies, with epilepsy as a prominent feature. High-dose methylprednisolone pulse therapy combined with IVIG has shown significant safety and efficacy in treating anti-D2R and DPPX antibody-positive autoimmune encephalitis-associated epilepsy.

Ovarian teratoma-associated anti-NMDA receptor encephalitis with severe features

Anti-N-methyl-D-aspartame receptor (NMDAR) encephalitis is an uncommon clinical entity for the general intensivist or neurologist. Diagnosis can be made by the presence of cerebrospinal fluid IgG antibody against the GluNR1 and GluNR2 subunits of the NMDAR. We present a case of anti-NMDAR encephalitis in a young woman with an ovarian teratoma treated with surgical resection and multiple immunomodulatory therapies.

Canadian Consensus Guidelines for the Diagnosis and Treatment of Autoimmune Encephalitis in Adults

Autoimmune encephalitis is increasingly recognized as a neurologic cause of acute mental status changes with similar prevalence to infectious encephalitis. Despite rising awareness, approaches to diagnosis remain inconsistent and evidence for optimal treatment is limited. The following Canadian guidelines represent a consensus and evidence (where available) based approach to both the diagnosis and treatment of adult patients with autoimmune encephalitis. The guidelines were developed using a modified RAND process and included input from specialists in autoimmune neurology, neuropsychiatry and infectious diseases. These guidelines are targeted at front line clinicians and were created to provide a pragmatic and practical approach to managing such patients in the acute setting.

Unveiling the Intricacies: A Comprehensive Review of Magnetic Resonance Imaging (MRI) Assessment of T2-Weighted Hyperintensities in the Neuroimaging Landscape

T2-weighted hyperintensities in neuroimaging represent areas of heightened signal intensity on magnetic resonance imaging (MRI) scans, holding crucial importance in neuroimaging. This comprehensive review explores the T2-weighted hyperintensities, providing insights into their definition, characteristics, clinical relevance, and underlying causes. It highlights the significance of these hyperintensities as sensitive markers for neurological disorders, including multiple sclerosis, vascular dementia, and brain tumors. The review also delves into advanced neuroimaging techniques, such as susceptibility-weighted and diffusion tensor imaging, and the application of artificial intelligence and machine learning in hyperintensities analysis. Furthermore, it outlines the challenges and pitfalls associated with their assessment and emphasizes the importance of standardized protocols and a multidisciplinary approach. The review discusses future directions for research and clinical practice, including the development of biomarkers, personalized medicine, and enhanced imaging techniques. Ultimately, the review underscores the profound impact of T2-weighted hyperintensities in shaping the landscape of neurological diagnosis, prognosis, and treatment, contributing to a deeper understanding of complex neurological conditions and guiding more informed and effective patient care.

An imaging review of the hippocampus and its common pathologies

The hippocampus is a complex structure located in the mesial temporal lobe that plays a critical role in cognitive and memory-related processes. The hippocampal formation consists of the dentate gyrus, hippocampus proper, and subiculum, and its importance in the neural circuitry makes it a key anatomic structure to evaluate in neuroimaging studies. Advancements in imaging techniques now allow detailed assessment of hippocampus internal architecture and signal features that has improved identification and characterization of hippocampal abnormalities. This review aims to summarize the neuroimaging features of the hippocampus and its common pathologies. It provides an overview of the hippocampal anatomy on magnetic resonance imaging and discusses how various imaging techniques can be used to assess the hippocampus. The review explores neuroimaging findings related to hippocampal variants (incomplete hippocampal inversion, sulcal remnant and choroidal fissure cysts), and pathologies of neoplastic (astrocytoma and glioma, ganglioglioma, dysembryoplastic neuroepithelial tumor, multinodular and vacuolating neuronal tumor, and metastasis), epileptic (mesial temporal sclerosis and focal cortical dysplasia), neurodegenerative (Alzheimer's disease, progressive primary aphasia, and frontotemporal dementia), infectious (Herpes simplex virus and limbic encephalitis), vascular (ischemic stroke, arteriovenous malformation, and cerebral cavernous malformations), and toxic-metabolic (transient global amnesia and opioid-associated amnestic syndrome) etiologies.

Paraneoplastic neurologic syndrome and autoantibody accompaniments of germ cell tumors

Paraneoplastic neurologic syndromes (PNSs) are a group of diseases affecting the central and/or peripheral nervous system caused by immune-mediated processes directed toward antigens with shared expression in tumor and neural tissue. Germ cell tumors (GCTs) are associated with PNSs with varied clinical phenotypes. Early diagnosis of PNS is vital to potentially uncover and treat underlying tumors, improving the chances of recovery, and preventing permanent neurologic complications. In this chapter, we outline the pathophysiology and epidemiology of PNS. We briefly provide a summary of GCTs in males and females. We review the neural-specific autoantibodies and PNSs associated with GCTs and their clinical and radiologic accompaniments. We also provide an overview of the treatment and prognosis of these disorders.

General features, pathogenesis, and laboratory diagnostics of autoimmune encephalitis

Autoimmune encephalitis (AE) is a group of inflammatory conditions that can associate with the presence of antibodies directed to neuronal intracellular, or cell surface antigens. These disorders are increasingly recognized as an important differential diagnosis of infectious encephalitis and of other common neuropsychiatric conditions. Autoantibody diagnostics plays a pivotal role for accurate diagnosis of AE, which is of utmost importance for the prompt recognition and early treatment. Several AE subgroups can be identified, either according to the prominent clinical phenotype, presence of a concomitant tumor, or type of neuronal autoantibody, and recent diagnostic criteria have provided important insights into AE classification. Antibodies to neuronal intracellular antigens typically associate with paraneoplastic neurological syndromes and poor prognosis, whereas antibodies to synaptic/neuronal cell surface antigens characterize many AE subtypes that associate with tumors less frequently, and that are often immunotherapy-responsive. In addition to the general features of AE, we review current knowledge on the pathogenic mechanisms underlying these disorders, focusing mainly on the potential role of neuronal antibodies in the most frequent conditions, and highlight current theories and controversies. Then, we dissect the crucial aspects of the laboratory diagnostics of neuronal antibodies, which represents an actual challenge for both pathologists and neurologists. Indeed, this diagnostics entails technical difficulties, along with particularly interesting novel features and pitfalls. The novelties especially apply to the wide range of assays used, including specific tissue-based and cell-based assays. These assays can be developed in-house, usually in specialized laboratories, or are commercially available. They are widely used in clinical immunology and in clinical chemistry laboratories, with relevant differences in analytic performance. Indeed, several data indicate that in-house assays could perform better than commercial kits, notwithstanding that the former are based on non-standardized protocols. Moreover, they need expertise and laboratory facilities usually unavailable in clinical chemistry laboratories. Together with the data of the literature, we critically evaluate the analytical performance of the in-house vs commercial kit-based approach. Finally, we propose an algorithm aimed at integrating the present strategies of the laboratory diagnostics in AE for the best clinical management of patients with these disorders.

A Near-Fatal Encounter with Acute Suicidal Behavior in Anti-N-methyl-D-aspartate Autoimmune Encephalitis

Anti-N-methyl-D-aspartate receptor encephalitis (anti-NMDARE) is a complex neuropsychiatric syndrome known for its diverse neurological manifestations, often involving psychiatric symptoms and seizures that elevate the risk of suicidal ideation and behavior. We present a case illustrating the potentially lethal nature of anti-NMDARE, wherein an unexpected suicide attempt occurred 10 days after the onset of seizures in a 21-year-old man. Upon arrival at the emergency room, immediate interventions addressed hypovolemic shock, followed by subsequent neurosurgical and orthopedic procedures. Six days after cessation of sedation, the patient exhibited atypical focal seizures, behavioral arrest, psychotic responses, and delusions. Despite normal brain magnetic resonance imaging and cerebrospinal fluid (CSF) analysis results, a high CSF immunoglobulin G index and posterior hypometabolism on brain F-fluorodeoxyglucose positron emission tomography raised suspicion of autoimmune encephalitis. Steroids and intravenous immunoglobulins were administered. A comprehensive evaluation ruled out other conditions. Serum and CSF tests confirmed the presence of anti-NMDAR antibodies. This case highlights the potential lethality of the acute stage of anti-NMDARE, emphasizing the absence of apparent psychiatric symptoms before a suicide attempt. Further studies on suicidality associated with anti-NMDARE are crucial, underscoring the importance of vigilance in cases involving newly diagnosed seizures or psychoses.

Clinical characteristics and prognosis in patients with neuronal surface antibody-mediated autoimmune encephalitis: a single-center cohort study in China

Objective

This retrospective observational study primarily aimed to analyse the clinical characteristics of patients with neuronal surface antibody-mediated autoimmune encephalitis (AE) in China and report their prognosis after immunotherapy.

Methods

Clinical characteristics, laboratory or imaging examinations, and treatment outcomes of 103 patients diagnosed with AE between 1 September 2014 and 31 December 2020 were collected. Univariate and multivariate logistic regression analyses were performed to determine the predictors of poor prognosis.

Results

Overall, 103 patients were enrolled in the study. The main clinical symptoms included seizures (74.8%), psychiatric and behavior disorders (66.0%), cognitive deficits (51.5%), disturbances of consciousness (45.6%), and movement disorders/involuntary movements (26.2%). The distribution of clinical syndromes also differed for different AE subtypes. The efficacy rates of first-line immunotherapy for anti-NMDAR, anti-LGI1, anti-GABABR, and anti-CASPR2 encephalitis were 70.2%, 92.3%, 70%, and 83.3%, respectively, and rituximab was administered to 21 patients as second-line immunotherapy, including 14 patients with anti-NMDAR encephalitis, 4 with anti-LGI1 encephalitis, 2 with anti-GABABR encephalitis, and 1 with anti-CASPR2 encephalitis. Five patients with poor effect of the second-line treatment received bortezomib. According to the results of the last follow-up, 78 patients had a good prognosis (mRS 0-2), and 21 patients had a poor prognosis (mRS 3-6). The proportion of patients with a poor prognosis was significantly higher in anti-GABABR encephalitis compared to the other AE subtypes (p<0.001). Multivariate analysis indicated that elevated neutrophil-to-lymphocyte ratio (NLR) and tumour presence were independent risk factors for poor prognosis. The regression equation of the model was logit(P)=-3.480 + 0.318 NLR+2.434 with or without tumour (with assignment =1, without assignment =0). The prediction probability generated by the regression model equation was used as the independent variable for receiver operating curve (ROC) analysis. The results showed that the area under the curve (AUC) of the prediction probability was 0.847 (95% CI, 0.733-0.961; p < 0.001).

Conclusions

Different AE subtypes demonstrated different clinical symptom spectra throughout the disease stage. Anti-LGI1 encephalitis and anti-CASPR2 encephalitis were more sensitive to first-line and second-line treatments. Anti-GABABR encephalitis had the worst prognosis among the abovementioned subtypes. The regression equation constructed using NLR and tumour presence effectively predicted the poor prognosis.

A Devastating Neurological Disorder: Anti-Dipeptidyl-Peptidase-Like Protein 6 (DPPX) Encephalitis Causing Rapidly Progressive Dementia

Rapidly progressive dementia (RPD) is caused by a heterogeneous group of neurological disorders, and the prototype is Creutzfeldt-Jakob disease (CJD). However, treatable causes including autoimmune encephalitis are often underrecognized and undertreated. A 72-year-old female patient was admitted with a 10-month history of rapidly progressive cognitive decline, visual hallucinations, paranoid behavior, diarrhea, and an 18-kg unintentional weight loss. On the physical exam, she was only oriented to the person and demonstrated an exaggerated startle response with diffuse rigidity. The initial clinical suspicion included CJD versus autoimmune encephalitis. Comprehensive laboratory testing, thyroid peroxidase, thyroglobulin antibodies, and autoimmune encephalitis panel were negative. The EEG showed mild to moderate diffuse slowing without any epileptiform abnormalities. An MRI brain revealed mild hippocampal atrophy. CSF testing revealed mild lymphocytic pleocytosis; RT-QuIC analysis and 14-3-3 protein were negative. There was no clinical improvement after treatment with IV steroids and IVIG. Repeated autoimmune encephalitis panel testing performed on a research basis was positive for dipeptidyl-peptidase-like protein 6 (DPPX) antibodies in serum and CSF. Unfortunately, our patient passed away before additional treatment could be attempted. Anti-DPPX encephalitis is a rare autoimmune disorder and an unrecognized cause of RPD. Early diagnosis and rapid escalation of treatment are imperative to avoid devastating neurological consequences.

Autoimmune processes in neurological patients are much more common than presently suspected

Autoimmune encephalitides are seldom diseases. How rare they actually are, however, is not known. The low incidence combined with the problematic identification may dampen efforts of neurologists, to identify patients with unclear symptoms as suffering from autoimmune encephalitis. Here, we aim to obtain a better estimate, how many patients with autoimmune disorders should be expected among 100 inpatients in a conventional neurological department. From a total number of 2603 non-stroke patients attended in a 2-year period (2018-2019) 460 CSFs were obtained. From this collection 187 samples (40.7%, > 500 sections) could be analyzed with our immunocytochemical technique. Autoreactive antibodies were detected in 102 (55%) of these 187 CSF samples. Certainly, the presence of autoreactive antibodies does not necessarily indicate that the patient suffers from an autoimmune disease. Our data indicate that from roughly 2000 patients during 1 year about 125 patients with autoreactive CSF antibodies should be expected in a conventional neurological department. This represents the about 35-fold value of what is generally expected at present. Being aware of this high incidence may intensify the efforts of neurologist to identify patients with any type of autoimmune encephalitis. This will be beneficial for patients, because they often profit from immunomodulatory therapy. Interestingly, some CFSs from our patients react with the CA2 subdivision of the hippocampus. While long neglected, recent research places this area into an important position to influence hippocampal network physiology. Autoreactive antibodies in the CSF may disturb the function of CA2 neurons, thereby explaining some neuropsychiatric symptoms in patients with autoimmune encephalitides.

Mimics of Autoimmune Encephalitis: Validation of the 2016 Clinical Autoimmune Encephalitis Criteria

BACKGROUND AND OBJECTIVES

The clinical criteria for autoimmune encephalitis (AE) were proposed by Graus et al. in 2016. In this study, the AE criteria were validated in the real world, and common AE mimics were described. In addition, criteria for probable anti-LGI1 encephalitis were proposed and validated.

METHODS

In this retrospective cohort study, patients referred to our national referral center with suspicion of AE and specific neuroinflammatory disorders with similar clinical presentations were included from July 2016 to December 2019. Exclusion criteria were pure cerebellar or peripheral nerve system disorders. All patients were evaluated according to the AE criteria.

RESULTS

In total, 239 patients were included (56% female; median age 42 years, range 1-85). AE was diagnosed in 104 patients (44%) and AE mimics in 109 patients (46%). The most common AE mimics and misdiagnoses were neuroinflammatory CNS disorders (26%), psychiatric disorders (19%), epilepsy with a noninflammatory cause (13%), CNS infections (7%), neurodegenerative diseases (7%), and CNS neoplasms (6%). Common confounding factors were mesiotemporal lesions on brain MRI (17%) and false-positive antibodies in serum (12%). Additional mesiotemporal features (involvement extralimbic structures, enhancement, diffusion restriction) were observed more frequently in AE mimics compared with AE (61% vs 24%; p = 0.005). AE criteria showed the following sensitivity and specificity: possible AE, 83% (95% CI 74-89) and 27% (95% CI 20-36); definite autoimmune limbic encephalitis (LE), 10% (95% CI 5-17) and 98% (95% CI 94-100); and probable anti-NMDAR encephalitis, 50% (95% CI 26-74) and 96% (95% CI 92-98), respectively. Specificity of the criteria for probable seronegative AE was 99% (95% CI 96-100). The newly proposed criteria for probable anti-LGI1 encephalitis showed a sensitivity of 66% (95% CI 47-81) and specificity of 96% (95% CI 93-98).

DISCUSSION

AE mimics occur frequently. Common pitfalls in AE misdiagnosis are mesiotemporal lesions (predominantly with atypical features) and false-positive serum antibodies. As expected, the specificity of the criteria for possible AE is low because these criteria represent the minimal requirements for entry in the diagnostic algorithm for AE. Criteria for probable AE (-LGI1, -NMDAR, seronegative) and definite autoimmune LE are applicable for decisions on immunotherapy in early disease stage, as specificity is high.

An Unusual Case of LGI1 (Leucine-Rich Glioma-Inactivated Protein 1) Limbic Encephalitis With Anti-acetylcholine Receptor and Anti-striational Autoantibodies

Autoimmune encephalitis (AE) results from immune-mediated damage to the central nervous system (CNS) with varying clinical manifestations depending on autoimmune antibodies present and the antigens they target. Leucine-rich glioma-inactivated protein 1 (LGI1) has been recognized as one of the leading causes of limbic encephalitis (LE), presenting with seizures, memory loss, and faciobrachial dystonic seizures. A better understanding of the unique presentations of these AE allows for quick and effective diagnosis and treatment. We are presenting a very unusual case of LGI1 autoimmune LE with two additional autoantibodies, anti-acetylcholine receptor (AChR) and anti-striational, in a patient with an underlying thymoma. We will discuss the pathophysiology and common clinical presentation of anti-LGI1 autoimmune LE.

A case of hyperacute postvaccinal encephalopathy after BNT162b2 nCoV-19 vaccine

The global severe acute respiratory syndrome coronavirus 2 pandemic contributed to the development of a large variety of vaccines, of which postvaccinal hyperacute encephalopathy is a very rare complication. Despite its rarity, if diagnosed properly, appropriate treatment can be rapidly applied. A healthy 53-year-old woman was admitted for a seizure on the day she received the second dose of the BNT 162b2 nCoV-19 vaccine. She subsequently developed irritability, which gradually worsened over several days. Cerebrospinal fluid analysis revealed mild pleocytosis and normal protein levels. Brain magnetic resonance imaging (MRI) revealed diffuse sulcal hyperintensity on the entire brain surface on fluid-attenuated inversion recovery images with meningeal enhancement. The patient was diagnosed with hyperacute postvaccinal encephalopathy and received immunosuppressive therapy with corticosteroids and therapeutic plasmapheresis. Fortunately, the patient responded to therapy, achieving almost complete recovery from the neurological symptoms, with only mild memory impairment remaining after 3 weeks. Based on the clinical presentation, electroencephalogram findings, and MRI, our patient developed hyperacute encephalopathy within 24 hours of vaccine administration, which we surmised from the temporal course of symptoms and brain imaging findings. Further studies are required to elucidate the pathogenesis of coronavirus disease 2019 vaccination-related encephalopathy.

Clinical presentations and treatment outcomes of Hashimoto encephalopathy at Siriraj Hospital - Thailand's largest national tertiary referral center

BACKGROUND

Hashimoto encephalopathy has multiple clinical presentations, and other than the presence of thyroid antibody, laboratory and imaging investigations are all non-specific. Data specific to the clinical presentations and treatment outcomes of patients with Hashimoto encephalopathy in Thailand remain scarce.

OBJECTIVES

To retrospectively investigate the clinical presentations and treatment outcomes of patients with Hashimoto encephalopathy at Siriraj Hospital.

METHODS

Patients who presented with acute encephalopathy at our center during July 2012-March 2017 were evaluated for eligibility. The inclusion criteria were positive anti-thyroperoxidase (anti-TPO) or anti-thyroglobulin (anti-Tg) in serum with negative neuronal antibody in serum or cerebral spinal fluid (CSF). Clinical presentations, symptom duration, laboratory results of thyroid status and thyroid autoantibody, CSF study, and clinical outcomes were collected.

RESULTS

Of the 204 patients who presented with encephalopathy, 31 (15.2%) were positive for the anti-TPO or anti-Tg antibody. Of those, 13 patients met the diagnostic criteria for Hashimoto encephalopathy. Clinical presentations included cognitive impairment (76.9%), clouding of consciousness (46.2%), and behavior change (30.8%). The neuropsychiatric presentations were visual hallucination (30.8%), auditory hallucination (15.4%), delusion (7.7%), and mood disturbance (23.1%). Other clinical presentations included seizure (38.5%), abnormal movement (23.1%), sleep disturbance (38.5%), ataxia (46.2%), stroke-like episode (15.4%), and fever (15.4%). Most patients (76.9%) had onset within < 3 months. Regarding outcomes, 1 patient who did not receive corticosteroid died from status epilepticus and septic shock. Among the 12 patients who received corticosteroid, 9 (75%) had marked improvement, 1 (8.3%) had slight improvement, and 2 (16.6%) had no clinical improvement. Seven patients (53.9%) had normal thyroid function, 4 patients (30.8%) had subclinical hypothyroidism, and 2 patients (15.4%) had subclinical hyperthyroidism.

CONCLUSIONS

The results of this study revealed cognitive impairment, neuropsychiatric symptoms, seizure, ataxia, and sleep disturbance to be common manifestations of Hashimoto encephalopathy. This condition should always be considered in individuals with subacute onset of unexplained cognitive impairment or cerebellar ataxia. Laboratory and neuroimaging investigations were all found to be nonspecific in Hashimoto encephalopathy. Most patients responded well to treatment, so clinical suspicion and early diagnosis and treatment will lead to improved patient outcomes.

A novel classification model based on cerebral 18F-FDG uptake pattern facilitates the diagnosis of acute/subacute seropositive autoimmune encephalitis

PURPOSE

To explore the intrinsic alteration of cerebral 18F-FDG metabolism in acute/subacute seropositive autoimmune encephalitis (AE) and to propose a universal classification model based on 18F-FDG metabolic patterns to predict AE.

METHODS

Cerebral 18F-FDG PET images of 42 acute/subacute seropositive AE patients and 45 healthy controls (HCs) were compared using voxelwise and region of interest (ROI)-based schemes. The mean standardized uptake value ratios (SUVRs) of 59 subregions according to a modified Automated Anatomical Labeling (AAL) atlas were compared using a t-test. Subjects were randomly divided into a training set (70%) and a testing set (30%). Logistic regression models were built based on the SUVRs and the models were evaluated by determining their predictive value in the training and testing sets.

RESULTS

The 18F-FDG uptake pattern in the AE group was characterized by increased SUVRs in the brainstem, cerebellum, basal ganglia, and temporal lobe, and decreased SUVRs in the occipital, and frontal regions with voxelwise analysis (false discovery rate [FDR] p<0.05). Utilizing ROI-based analysis, we identified 15 subareas that exhibited statistically significant changes in SUVRs among AE patients compared to HC (FDR p<0.05). Further, a logistic regression model incorporating SUVRs from the calcarine cortex, putamen, supramarginal gyrus, cerebelum_10, and hippocampus successfully enhanced the positive predictive value from 0.76 to 0.86 when compared to visual assessments. This model also demonstrated potent predictive ability, with AUC values of 0.94 and 0.91 observed for the training and testing sets, respectively.

CONCLUSIONS

During the acute/subacute stages of seropositive AE, alterations in SUVRs appear to be concentrated within physiologically significant regions, ultimately defining the general cerebral metabolic pattern. By incorporating these key regions into a new classification model, we have improved the overall diagnostic efficiency of AE.

Anti-N-Methyl-D-Aspartate Receptor Encephalitis With Diffuse Demyelinating Plaques: A Case Report of an Atypical Presentation

Anti-N-methyl-D-aspartate (anti-NMDA) receptor encephalitis is an autoimmune disease triggered by antibodies against the NR1 subunit of this receptor. It has a wide variety of presentations, including abnormal behavior, psychosis, seizures, abnormal movement, insomnia, and irritability. The diagnosis is confirmed by the presence of one of the six main symptoms and anti-NR1 immunoglobulin G (IgG)-positive antibodies in the cerebrospinal fluid (CSF) after the exclusion of other disorders. We present a case of an 18-year-old female with progressive paresthesia and muscle weakness that compromised walking and psychiatric symptoms. She was admitted to a private institution where magnetic resonance imaging (MRI) revealed pseudotumoral lesions, which led to surgical intervention. The original histopathological diagnosis was of a pleomorphic xanthoastrocytoma (PXA) WHO grade 2. As symptoms persisted, she was referred to our institution where a new MRI was performed, and a biopsy was re-evaluated. It showed perivascular inflammatory infiltrates composed of T cells, intense peripheral gliosis, nodules of macrophages, and reactive astrocytes in the white matter with fragmentation and vacuolation of myelin sheets, suggesting a demyelinating process in contrast to neoplasia. CSF analysis was performed, and it was positive for anti-NMDA antibodies. Immunohistochemical positivity for N-methyl-D-aspartate (NMDA) was observed in the neuronal nuclei, which led to the diagnosis.

MR Imaging Findings in a Large Population of Autoimmune Encephalitis

BACKGROUND AND PURPOSE

Autoimmune encephalitis is a rare condition in which autoantibodies attack neuronal tissue, causing neuropsychiatric disturbances. This study sought to evaluate MR imaging findings associated with subtypes and categories of autoimmune encephalitis.

MATERIALS AND METHODS

Cases of autoimmune encephalitis with specific autoantibodies were identified from the medical record (2009-2019). Cases were excluded if no MR imaging of the brain was available, antibodies were associated with demyelinating disease, or >1 concurrent antibody was present. Demographics, CSF profile, antibody subtype and group (group 1 intracellular antigen or group 2 extracellular antigen), and MR imaging features at symptom onset were reviewed. Imaging and clinical features were compared across antibody groups using χ² and Wilcoxon rank-sum tests.

RESULTS

Eighty-five cases of autoimmune encephalitis constituting 16 distinct antibodies were reviewed. The most common antibodies were anti-N-methyl-D-aspartate (n = 41), anti-glutamic acid decarboxylase (n = 7), and anti-voltage-gated potassium channel (n = 6). Eighteen of 85 (21%) were group 1; and 67/85 (79%) were group 2. The median time between MR imaging and antibody diagnosis was 14 days (interquartile range, 4-26 days). MR imaging had normal findings in 33/85 (39%), and 20/33 (61%) patients with normal MRIs had anti-N-methyl-D-aspartate receptor antibodies. Signal abnormality was most common in the limbic system (28/85, 33%); 1/68 (1.5%) had susceptibility artifacts. Brainstem and cerebellar involvement were more common in group 1, while leptomeningeal enhancement was more common in group 2.

CONCLUSIONS

Sixty-one percent of patients with autoimmune encephalitis had abnormal brain MR imaging findings at symptom onset, most commonly involving the limbic system. Susceptibility artifact is rare and makes autoimmune encephalitis less likely as a diagnosis. Brainstem and cerebellar involvement were more common in group 1, while leptomeningeal enhancement was more common in group 2.

Bibliometric Analysis on GABA-A Receptors Research Based on CiteSpace and VOSviewer

Background

GABA-A receptors are the primary mediators of brain inhibitory neurotransmission. In the past years, many studies focused on this channel to decipher the pathogenesis of related diseases but lacked bibliometric analysis research. This study aims to explore the research status and identify the research trends of GABA-A receptor channels.

Methods

Publications related to GABA-A receptor channels were retrieved from the Web of Science Core Collection from 2012 to 2022. After screening, the VOSviewer 1.6.18 and Citespace 5.8 R3 were used for bibliometric analysis from journals, countries, institutions, authors, co-cited references and keywords.

Results

We included 12,124 publications in the field of GABA-A receptor channels for analysis. The data shows that although there was a slight decrease in annual publications from 2012 to 2021, it remained at a relatively high level. Most publications were in the domain of neuroscience. Additionally, the United States was the most prolific country, followed by China. Univ Toronto was the most productive institution, and James M Cook led essential findings in this field. Furthermore, brain activation, GABAAR subunits expression, modulation mechanism in pain and anxiety behaviors and GABA and dopamine were paid attention to by researchers. And top research frontiers were molecular docking, autoimmune encephalitic series, obesity, sex difference, diagnosis and management, EEG and KCC2.

Conclusion

Taken together, academic attention on GABA-A receptor channels was never neglected since 2012. Our analysis identified key information, such as core countries, institutions and authors in this field. Molecular docking, autoimmune encephalitic series, obesity, sex difference, diagnosis and management, EEG and KCC2 will be the future research direction.

PET/MRI Applications in Pediatric Epilepsy

Epilepsy neuroimaging assessment requires exceptional anatomic detail, physiologic and metabolic information. Magnetic resonance (MR) protocols are often time-consuming necessitating sedation and positron emission tomography (PET)/computed tomography (CT) comes with a significant radiation dose. Hybrid PET/MRI protocols allow for exquisite assessment of brain anatomy and structural abnormalities, in addition to metabolic information in a single, convenient imaging session, which limits radiation dose, sedation time, and sedation events. Brain PET/MRI has proven especially useful for accurate localization of epileptogenic zones in pediatric seizure cases, providing critical additional information and guiding surgical decision making in medically refractory cases. Accurate localization of seizure focus is necessary to limit the extent of the surgical resection, preserve healthy brain tissue, and achieve seizure control. This review provides a systematic overview with illustrative examples demonstrating the applications and diagnostic utility of PET/MRI in pediatric epilepsy.

Claustrum sparing sign in seronegative limbic encephalitis

Background

Limbic encephalitis (LE) is a rare variant of autoimmune encephalitis. It often manifests with subacute neuropsychiatric symptoms of agitation, delusions, variable seizure semiology, and short-term memory loss. Seronegative limbic encephalitis can pose a diagnostic conundrum owing to its inadequately understood pathophysiology.

Case presentation

We report a rare case of a young male with subacute neuropsychiatric manifestations of delusions, agitations and seizures. He was diagnosed with seronegative limbic encephalitis (SNLE). Brain MRI demonstrated bilateral Claustrum sparing sign. An EEG showed continuous left-sided epileptiform discharges in periodic to predominantly left middle temporal. Patient condition gradually improved with pulsed methylprednisolone, intravenous immunoglobulins and anti-seizure medications.

Conclusion

Claustrum remains one of the least understood neuroanatomical structures. Claustrum sign has been reported in febrile infection-related epilepsy syndrome (FIRES), LE, and autoimmune refractory epilepsy. To the best of our knowledge, we report the first case in literature with Claustrum sparing sign in seronegative Limbic Encephalitis. Further experimental models and researches are warranted to better understand the unique function of the claustrum and unravel possible other attributable auto-antibodies, which could alter treatment and prognosis.

Clinical spectrum of contactin-associated protein 2 autoimmune encephalitis in children

Objective

Anti-contactin-associated protein 2 (CASPR2)-related autoimmune encephalitis (AE) is more common in adults than in children. Clinical understanding of anti-CASPR2-antibody (Ab)-related AE, diagnosis and treatment standards are lacking in children. Therefore, this retrospective study on clinical symptoms and treatment outcomes in children with anti-CASPR2-Ab-related AE was conducted, to improve the clinical understanding of the disease, its diagnosis and treatment.

Methods

This study retrospectively assessed children with anti-CASPR2-Ab-related AE from January 1, 2020, to June 30, 2022, in the Department of Neurology at Hunan Children's Hospital. Data regarding demographics, clinical symptoms, laboratory examinations, electroencephalography (EEG), imaging, and curative were collected.

Results

Thirteen patients were positive for serum anti-CASPR2-Ab (age at manifestation, 25 months to 13 years old; median, 8.1 years old; male-to-female ratio, 8/5). One patient (P1) had dual Abs, including anti-CASPR2 and anti-N-methyl-D-aspartate receptor Abs; his symptoms were more severe than those of children with anti-CASPR2 Abs alone. The clinical symptoms of the 13 patients with anti-CASPR2 Ab were movement disorders (9/13), consciousness disorders (9/13), abnormal demeanor (8/13), seizures (7/13), language disorders (6/13), fever (6/13), pain (4/13), involuntary exercise (4/13), poor diet (4/13), vomiting (3/13), sleep disorders (3/13), mood disorders (3/13), eczema/itching/redness (2/13), sweating (P8), urinary disorders (P13), and cognitive disorders (P9). No tumors were found in any patient. Additionally, EEG results of six patients were abnormal and imaging findings such as abnormal signals were found in 10 patients. Moreover, all except one patient recovered well after treatment; P1 with overlapping syndrome underwent recovery for more than 2 years. None of the patients who recovered have had a relapse.

Discussion and conclusion

Anti-CASPR2-Ab-related AE has several clinical manifestations. Anti-CASPR2-Ab levels were higher in male patients than in female patients. Moreover, related tumors are relatively rare. Most patients benefit from immunotherapy and have a lower chance of recurrence in the short term. Furthermore, different from patients who had anti-CASPR2-Ab AE alone, those with overlapping syndrome had a severe and complex condition requiring lengthy treatment and rehabilitation. Additional studies are needed to evaluate the long-term prognosis of these patients.

Biomarkers in autoimmune diseases of the central nervous system

The autoimmune diseases of the central nervous system (CNS) represent individual heterogeneity with different disease entities. Although clinical and imaging features make it possible to characterize larger patient cohorts, they may not provide sufficient evidence to detect disease activity and response to disease modifying drugs. Biomarkers are becoming a powerful tool due to their objectivity and easy access. Biomarkers may indicate various aspects of biological processes in healthy and/or pathological states, or as a response to drug therapy. According to the clinical features described, biomarkers are usually classified into predictive, diagnostic, monitoring and safety biomarkers. Some nerve injury markers, humoral markers, cytokines and immune cells in serum or cerebrospinal fluid have potential roles in disease severity and prognosis in autoimmune diseases occurring in the CNS, which provides a promising approach for clinicians to early intervention and prevention of future disability. Therefore, this review mainly summarizes the potential biomarkers indicated in autoimmune disorders of the CNS.

Autoimmune encephalitis: Epidemiology, pathophysiology and clinical spectrum (part 2)

Autoimmune encephalitis (AE) represents a growing number of severe autoimmune-inflammatory diseases affecting both the white and grey matter of the brain. In part 1 of this series we focused on the epidemiology, pathophysiology and clinical presentation of this condition, with two illustrative cases. In this part, we will introduce the clinical criteria for AE, particularly for the diagnosis of anti-N-methyl-D-aspartate (NMDA) receptor encephalitis, which were developed to facilitate immune treatment in suspected cases before antibody results are available. We subsequently discuss the work up, differential diagnosis and treatment options for patients with this disease.  

MRI and steroid-responsive encephalopathy associated with autoimmune thyroiditis: first report of conus medullaris involvement and literature review of the known neuroimaging profiles

BACKGROUND

Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT) is a rare but potentially reversible autoimmune encephalopathy. The most frequent neuroimaging correlates are normal brain MRI or non-specific white matter hyperintensities.

METHODS

We present the first description of conus medullaris involvement, also providing an extensive review of MRI patterns described so far.

RESULTS

Our results show that in less than 30% of cases, it is possible to find focal SREAT neuroanatomical correlates. Among these, T2w/FLAIR temporal hyperintensities are the most frequent, followed by basal ganglia/thalamic and brainstem involvement, respectively.

CONCLUSIONS

Unfortunately, spinal cord investigation is an uncommon practice in the diagnostic approach of encephalopathies, thus neglecting potential pathological lesions of the medulla spinalis. In our opinion, the extension of the MRI study to the cervical, thoracic, and lumbosacral regions may allow finding new, and hopefully specific, anatomical correlates.

Metagenomic next-generation sequencing for the etiological diagnosis of rabies virus in cerebrospinal fluid

Background

Rabies is a highly fatal disease. Once symptoms develop, death usually occurs within days. Survivors were occasionally reported in the literatures. Ante-mortem diagnosis remains a challenge in most rabies endemic countries. A novel, accurate diagnostic assay is highly desirable.

Methods

We used metagenomic next-generation sequencing (mNGS) to examine the cerebrospinal fluid (CSF) samples of a 49-year-old patient with rabies and validated the results by TaqMan PCR and RT-PCR/Sanger sequencing.

Results

Metagenomic next-generation sequencing identified sequence reads uniquely aligned to the rabies virus (RABV). PCR confirmed the presence of the partial RABV N gene in the CSF. Phylogenetic analysis showed that the RABV grouped as an Asian clade, which is the most broadly distributed clade in China.

Conclusion

Metagenomic next-generation sequencing may be a useful screening tool for the etiological diagnosis of rabies, especially in the absence of timely rabies laboratory testing or in patients with no exposure history.

Safety of inactivated COVID-19 vaccines in autoimmune encephalitis: A real-world cross-sectional survey

OBJECTIVE

To assess safety data of the inactivated COVID-19 vaccines in a real-world sample of people with autoimmune encephalitis (pwAE).

METHODS

A cross-sectional study was performed between 1 March and 30 April 2022. We invited pwAE from our previous ONE-WC (Outcome of Autoimmune Encephalitis Study in Western China) registration study database, to attend neurological clinics, at West China Hospital to participate in a face-to-face survey using a custom-designed questionnaire for this study. The ONE-WC study began in October 2011 and prospectively enrolled pwAE from four large comprehensive neurological centers in Sichuan province, China.

RESULTS

Of the 387 pwAE, 240 (62.0%) completed the questionnaire. Half the 240 participants (121, 50.4%) reported receiving at least one dose of COVID-19 vaccine, which in all but two patients received inactivated COVID-19 vaccine. Among vaccinated pwAE, the median age was 35 years (range 15-69) and 57.8% of them were women. The most frequent reasons that unvaccinated individuals reported for not receiving the COVID-19 vaccine were concern about vaccine-induced relapse of AE (50.4%) and advice from a physician to delay vaccination (21.0%). Small proportions of vaccinated individuals reported adverse events after the first dose (11.5%) or the second dose (10.2%), and none of the adverse events was serious. Across the entire sample, one individual reported relapsing within 30 days after the first dose and three individuals reported relapsing more than 120 days after the first dose.

CONCLUSIONS

This real-world survey indicates an overall favorable safety profile of the inactivated COVID-19 vaccine for pwAE.

A pediatric case of autoimmune encephalitis with chronologically moving seizure foci and cortical lesions: A case report

INTRODUCTION

Autoimmune encephalitis (AIE) is a relatively newly described category of immune-mediated diseases involving the central nervous system with a wide spectrum of clinical presentations, ranging from relatively mild or insidious onset of cognitive impairment to more complex forms of encephalopathy with medically refractory seizures. Single or multifocal seizures accompanied by neuropsychiatric symptoms and cognitive or memory impairments are suggestive of clinical features at AIE onset.

CASE REPORT

A six-year-old boy presented with repetitive focal seizures, slowly progressive emotional liability, and attention-deficit/hyperactivity disorder-like symptoms. Seizure types varied during the clinical course, sometimes emerging as clusters or statuses. MRI performed during seizure clustering/status revealed moving signal abnormalities. We successfully treated the patient with high-dose intravenous methylprednisolone. Cerebrospinal fluid analysis revealed pleocytosis and marked elevation of antibodies against N-terminals of N-methyl-d-aspartate type glutamate receptor subunits and granzyme B.

CONCLUSION

We report a case of moving seizure foci with abnormal MRI findings. Although the onset of psychiatric symptoms slowly progressed to those atypical for AIE, responsiveness to immunotherapy, cerebrospinal fluid pleocytosis, and autoantibodies all indicated AIE. We thus suggest that moving seizure foci and abnormal MRI signals may be findings of AIE.

Autoimmune-mediated encephalitis and mimics: A neuroimaging review

Autoimmune encephalitis is a category of autoantibody-mediated neurological disorders that often presents a diagnostic challenge due to its variable clinical and imaging findings. The purpose of this image-based review is to provide an overview of the major subtypes of autoimmune encephalitis and their associated autoantibodies, discuss their characteristic clinical and imaging features, and highlight several disease processes that may mimic imaging findings of autoimmune encephalitis. A literature search on autoimmune encephalitis was performed and publications from neuroradiology, neurology, and nuclear medicine literature were included. Cases from our institutional database that best exemplify major imaging features were presented.

Neurosyphilis: The Great Imitator

Syphilis is a sexually transmitted disease caused by spirochete Treponema pallidum, with a growing incidence documented in recent years. Its clinical course is divided into three phases - primary, secondary, and tertiary syphilis - and virtually any organ can be affected, resulting in diverse clinical manifestations, making the diagnosis challenging. Neurosyphilis is a progressive, destructive disease of the central nervous system (CNS) that can develop at any stage of the infection, leading to meningeal involvement, meningovascular disease, or parenchymal syphilis (including tabes dorsalis and general paresis). Its clinical manifestations are heterogeneous and vary from focal neurologic signs to neuropsychiatric manifestations. The diagnosis is based mainly on the clinical picture and study of cerebrospinal fluid. Neuroimaging is helpful and sometimes essential, with magnetic resonance imaging being the most sensitive radiologic method, although there are no pathognomonic radiologic signs. Treatment of all forms of neurosyphilis is based on parenteral penicillin. We present a case of neurosyphilis in a patient presenting with a subacute confusional state and initial imaging findings suggestive of metastatic CNS lesions.

Parallel roles of neuroinflammation in feline and human epilepsies

Autoimmune encephalitis refers to a group of disorders characterised by a non-infectious encephalitis, often with prominent seizures and surface neuronal autoantibodies. AE is an important cause of new-onset refractory status epilepticus in humans and is frequently responsive to immunotherapies including corticosteroids, plasma exchange, intravenous immunoglobulin G and rituximab. Recent research suggests that parallel autoantibodies can be detected in non-human mammalian species. The best documented example is leucine-rich glioma-inactivated 1 (LGI1)-antibodies in domestic cats with limbic encephalitis (LE). In this review, we discuss the role of neuroinflammation and autoantibodies in human and feline epilepsy and LE.

Extracellular Vesicles in Chronic Demyelinating Diseases: Prospects in Treatment and Diagnosis of Autoimmune Neurological Disorders

Extracellular vesicles (EVs) represent membrane-enclosed structures that are likely to be secreted by all living cell types in the animal organism, including cells of peripheral (PNS) and central nervous systems (CNS). The ability to cross the blood-brain barrier (BBB) provides the possibility not only for various EV-loaded molecules to be delivered to the brain tissues but also for the CNS-to-periphery transmission of these molecules. Since neural EVs transfer proteins and RNAs are both responsible for functional intercellular communication and involved in the pathogenesis of neurodegenerative diseases, they represent attractive diagnostic and therapeutic targets. Here, we discuss EVs' role in maintaining the living organisms' function and describe deviations in EVs' structure and malfunctioning during various neurodegenerative diseases.

FDG-PET in Autoimmune Encephalitis: Utility, Pattern of Abnormalities, and Correlation with Autoantibodies

Background

Fluorodeoxyglucose-positron emission tomography (FDG-PET) in autoimmune encephalitis (AE) as an adjunctive investigation helps in characterizing the type of AE based on characteristic metabolic patterns.

Objectives

We aimed to study the following: (i) the sensitivity of FDG-PET in the diagnosis of AE, (ii) describe abnormal patterns of metabolism of various subtypes of AE, and (iii) correlate serum serology with FDG-PET abnormalities.

Materials and Methods

This study was conducted at a tertiary university hospital in South India. The demographic profile, clinical features, and investigations (FDG-PET, magnetic resonance imaging (MRI) brain, electroencephalography (EEG), cerebrospinal fluid (CSF)) were reviewed. The nuclear medicine physician performed blinded qualitative visual and semi-quantitative analysis of the 18-FDG-PET (fluorine 18-FDG-PET) findings of these patients.

Results

Twenty-nine (M:F: 11:18) patients were recruited; among them, 22 (75.8%) patients had autoimmune antibodies; the rest seven (24.1%) patients were seronegative. Among the 22 seropositive patients, 9 (31%) patients were positive for anti-N-methyl-D-aspartate receptor (NMDAR), 8 (28%) for anti-leucine-rich glioma inactivated 1 (LGI-1), 4 (14%) for anti-contactin-associated protein 2 (CASPR2), 1 (3%) for anti-glutamic acid decarboxylase (GAD)-65, and rest 7 (24%) patients were seronegative. The patterns most commonly observed were isolated hypermetabolism (41%), isolated hypometabolism (41%), and combined hypermetabolism with hypometabolism (18%). The fraction of abnormalities was lower for MRI (17/22; 73.9%) than for FDG-PET (27/29; 93.1%). FDG-PET correlated with serology in 10 (34%) cases [NMDAR: 6 (60%) and LGI-1: 4 (40%)]. The sensitivity of FDG-PET was 94.1% when compared with MRI.

Discussion and Conclusion

FDG-PET correlated with serology in only one-third of patients. The most consistent pattern in both seropositive and seronegative AE is characterized by parieto-occipital hypometabolism and fronto-temporal with basal ganglia hypermetabolism.

Brain magnetic resonance imaging predictors in anti-N-methyl-D-aspartate receptor encephalitis

OBJECTIVE

Brain magnetic resonance imaging (MRI) findings in anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis are nonspecific and rarely have obvious associations with clinical characteristics and outcomes. This study aimed to comprehensively describe the MRI features of patients with NMDAR encephalitis, examine their associations with clinical characteristics, and evaluate their predictive power for disease recurrence and prognosis.

METHODS

We retrospectively extracted the clinical data and brain MRI findings of 144 patients with NMDAR encephalitis. Patients underwent a 2-year follow-up to assess disease outcomes. We evaluated the associations of brain MRI findings at the onset with clinical characteristics, recurrence, and prognosis.

RESULTS

Initial MRI showed typical abnormalities in 65 patients (45.1%); of these, 34 (29.3%) developed recurrence and 10 (9.4%) had poor prognosis (mRS ≥3). Binary logistic regression analyses revealed that insula abnormalities were associated with acute seizure (odds ratio [OR] = 3.048, 95% confidence interval [CI]: 1.026-9.060) and white matter lesions were associated with cognitive impairment (OR = 2.730, 95% CI: 1.096-6.799). Risk factors for a poor 2-year prognosis included a higher number of brain MRI abnormalities (OR = 1.573, 95% CI: 1.129-2.192) and intensive care unit (ICU) admissions (OR = 15.312, 95% CI: 1.684-139.198). The risk factors for 2-year recurrence included abnormalities of the thalamus (HR = 3.780, 95% CI: 1.642-8.699).

INTERPRETATIONS

Brain MRI features of patients with NMDAR encephalitis were associated with clinical manifestations, prognosis, and recurrence. Higher numbers of MRI abnormalities and ICU admissions were predictive of poor prognosis. Abnormalities of the thalamus constituted a recurrence-related risk factor.

Clinical and MRI differential analysis of autoimmune encephalitis and viral encephalitis

Objectives

The goal of this study was to analyze the clinical and magnetic resonance imaging (MRI) characteristics of autoimmune encephalitis (AE) and viral encephalitis (VE) at the initial stage of onset.

Methods

This study was a retrospective analysis of the clinical manifestations, laboratory tests, electroencephalogram examination, imaging examinations, and treatment outcomes of 24 VE patients and 20 AE patients.

Results

The onset age was significantly younger in the VE group than in the AE group, mainly occurring in adolescents (P < 0.05). The proportions of fever, headache, and vomiting were higher in the VE group than in the AE group (P < 0.05), and there were few manifestations of central hypoventilation. The incidence of abnormal myocardial enzymes was significantly higher in the VE group than in the AE group (P < 0.05). There was no significant difference in electroencephalogram test results between the VE and AE groups. Regarding magnetic resonance imaging (MRI), the proportion of single lesion involving a single lobe or multiple asymmetries involving the limbic system in the VE group was higher than that in the AE group (P < 0.05). The incidence of lesion enhancement in the VE group was higher than that in the AE group. Meanwhile, diffusion-weighted imaging sequence was more sensitive than T2 liquid-attenuated inversion recovery sequence in the detection, efficacy evaluation, and follow-up review of the AE and VE groups.

Conclusion

The onset age of VE is younger, and the clinical symptoms of AE and VE differ with statistical significance. MRI can objectively reflect the imaging characteristics of both groups. Combining early clinical manifestations with imaging manifestations can facilitate early diagnosis and treatment, and improve the prognosis.

Herpes simplex virus-1 encephalitis secondary to whole brain radiation therapy for metastatic renal cell carcinoma

Herpes simplex virus-1 (HSV-1) infection is the most common cause of encephalitis. This virus commonly lays dormant in neural ganglia, specifically the trigeminal ganglia, following retrograde axonal transport from the site of infection. States of immunosuppression can activate the virus to cause active infection. There are several causes of immunosuppression that can cause viral reactivation. Sporadic case reports have demonstrated HSV-1 encephalitis following brain radiotherapy, although no clear relationship between this treatment and HSV-1 encephalitis has been elucidated. HSV1 encephalitis that arises during immunocompromized states has an atypical presentation for encephalitis, potentially obfuscating the diagnosis and delaying subsequent treatment. The main diagnostic criteria, including CSF analysis, brain imaging, and clinical presentation, all commonly present atypically during states of immunosuppression. For these reasons, it is imperative for physicians to be aware of this rare sequelae in appropriate populations, such as patients undergoing brain radiotherapy. We present a case of an atypical presentation of HSV-1 encephalitis in a patient who recently completed radiotherapy for brain metastases secondary to renal cell carcinoma.

Psychiatric Illness or Immune Dysfunction-Brain Perfusion Imaging Providing the Answer in a Case of Anti-NMDAR Encephalitis

BACKGROUND

We investigated the potential use of SPECT quantification in addition to qualitative brain perfusion analysis for the detection of anti-NMDAR encephalitis. The question is how to normalize brain activity to be able to quantitatively detect perfusion patterns. Usually, brain activity is normalized to a structure considered unaffected by the disease.

METHODS

Brain [99mTc]-HMPAO SPECT was performed as a method to detect brain perfusion patterns. The patterns of abnormal brain perfusion cannot always be reliably and qualitatively assessed when dealing with rare diseases. Recent advances in SPECT quantification using commercial software have enabled more objective and detailed analysis of brain perfusion. The cerebellum and whole brain were used as the normalization structures and were compared with visual analysis.

RESULTS

The quantification analysis performed with whole brain normalization confirmed right parietal lobe hypoperfusion while also detecting statistically significant left-to-right perfusion differences between the temporal lobe and thalamus. Whole brain normalization further described bilateral frontal lobe hyperperfusion, predominantly of the left lobe, and was in accordance with visual analysis.

CONCLUSION

SPECT quantitative brain perfusion analysis, using the whole brain as the normalization structure rather than the cerebellum, in this case, improved confidence in the visual detection of anti-NMDAR encephalitis and provided unexpected solutions to atypical psychiatric dilemmas.

COVID-19'un santral sinir sistemi tutulumunu değerlendirmek için bir araç olarak manyetik rezonans görüntülemenin etkinliği

Amaç: Çalışmamızın amacı, COVID-19 ile ilişkili akut nörolojik bulguları olan hastaları tanımlamayı ve tanısında manyetik rezonans görüntüleme (MRG) etkinliğinin gösterilmesini amaçlamaktır. Gereç ve Yöntem: Haziran 2020 ve Aralık 2021 tarihleri arasında kliniğimizde Covid-19 tanısı almış, akciğerde pnömoni bulguları olan, akut nörolojik bulguları olan ve Beyin MRG olan 90 hasta çalışmaya alındı. Bulgular santral sinir sistemi (SSS) tutulumu bulgulari olmayan 46 hasta ve SSS bulgulari olan 44 hasta retrospektif olarak değerlendirildi. Bulgular: COVID-19 hastalarında en sık görülen nörolojik belirtiler; tedavi ile açıklanamayan şuur kayıbı (28/44, %63,6), focal nörolojik defisit (21/44, %47,7) and nöbet (9/44, %20,4). SSS tutulumu olan hastalarda yoğunbakımda yatış sürelerinde uzama, ventilator desteği gereksinimde artış ve mortalitede artış görüldü. Nörolojik semptomları olan 44 hastaya beyin MRG çekildi. MRG çekilen hastalarda 68,3 ortalama yaş (45–78). 32 hastanın (%72) MRG’nda akut bulgular saptandı. Beyin MR görüntülemesinde en sık konulan tanılar akut ve subakut infarktlardı. Sonuç: Merkezi sinir sistemi bulgularının mekanizması hala belirsizdir, COVID-19 hastalarında nörolojik semptomlar özellikle yoğun bakım ünitelerinde önemli bir sorundur. Bu nedenle SSS tutulumunun erken tespiti ve tedavisi çok önemlidir.

Diagnostic yield of diffusion-weighted brain MR imaging in patients with cognitive impairment: Large cohort study with 3,298 patients

Objective

There is a paucity of large cohort-based evidence regarding the need and added value of diffusion-weighted imaging (DWI) in patients attending outpatient clinic for cognitive impairment. We aimed to evaluate the diagnostic yield of DWI in patients attending outpatient clinic for cognitive impairment.

Materials and methods

This retrospective, observational, single-institution study included 3,298 consecutive patients (mean age ± SD, 71 years ± 10; 1,976 women) attending outpatient clinic for cognitive impairment with clinical dementia rating ≥ 0.5 who underwent brain MRI with DWI from January 2010 to February 2020. Diagnostic yield was defined as the proportion of patients in whom DWI supported the diagnosis that underlies cognitive impairment among all patients. Subgroup analyses were performed by age group and sex, and the Chi-square test was performed to compare the diagnostic yields between groups.

Results

The overall diagnostic yield of DWI in patients with cognitive impairment was 3.2% (106/3,298; 95% CI, 2.6–3.9%). The diagnostic yield was 2.5% (83/3,298) for acute or subacute infarct, which included recent small subcortical infarct for which the diagnostic yield was 1.6% (54/3,298). The diagnostic yield was 0.33% (11/3,298) for Creutzfeldt-Jakob disease (CJD), 0.15% (5/3,298) for transient global amnesia (TGA), 0.12% (4/3,298) for encephalitis and 0.09% (3/3,298) for lymphoma. There was a trend towards a higher diagnostic yield in the older age group with age ≥ 70 years old (3.6% vs 2.6%, P = .12). There was an incremental increase in the diagnostic yield from the age group 60–69 years (2.6%; 20/773) to 90–99 years (8.0%; 2/25).

Conclusion

Despite its low overall diagnostic yield, DWI supported the diagnosis of acute or subacute infarct, CJD, TGA, encephalitis and lymphoma that underlie cognitive impairment, and there was a trend towards a higher diagnostic yield in the older age group.

Treatable Ataxias: How to Find the Needle in the Haystack?

Treatable ataxias are a group of ataxic disorders with specific treatments. These disorders include genetic and metabolic disorders, immune-mediated ataxic disorders, and ataxic disorders associated with infectious and parainfectious etiology, vascular causes, toxins and chemicals, and endocrinopathies. This review provides a comprehensive overview of different treatable ataxias. The major metabolic and genetic treatable ataxic disorders include ataxia with vitamin E deficiency, abetalipoproteinemia, cerebrotendinous xanthomatosis, Niemann-Pick disease type C, autosomal recessive cerebellar ataxia due to coenzyme Q10 deficiency, glucose transporter type 1 deficiency, and episodic ataxia type 2. The treatment of these disorders includes the replacement of deficient cofactors and vitamins, dietary modifications, and other specific treatments. Treatable ataxias with immune-mediated etiologies include gluten ataxia, anti-glutamic acid decarboxylase antibody-associated ataxia, steroid-responsive encephalopathy associated with autoimmune thyroiditis, Miller-Fisher syndrome, multiple sclerosis, and paraneoplastic cerebellar degeneration. Although dietary modification with a gluten-free diet is adequate in gluten ataxia, other autoimmune ataxias are managed by short-course steroids, plasma exchange, or immunomodulation. For autoimmune ataxias secondary to malignancy, treatment of tumor can reduce ataxic symptoms. Chronic alcohol consumption, antiepileptics, anticancer drugs, exposure to insecticides, heavy metals, and recreational drugs are potentially avoidable and treatable causes of ataxia. Infective and parainfectious causes of cerebellar ataxias include acute cerebellitis, postinfectious ataxia, Whipple's disease, meningoencephalitis, and progressive multifocal leukoencephalopathy. These disorders are treated with steroids and antibiotics. Recognizing treatable disorders is of paramount importance when dealing with ataxias given that early treatment can prevent permanent neurological sequelae.

Autoimmune Encephalitis: A Physician’s Guide to the Clinical Spectrum Diagnosis and Management

The rapidly expanding spectrum of autoimmune encephalitis in the last fifteen years is largely due to ongoing discovery of many neuronal autoantibodies. The diagnosis of autoimmune encephalitis can be challenging due to the wide spectrum of clinical presentations, prevalence of psychiatric features that mimic primary psychiatric illnesses, frequent absence of diagnostic abnormalities on conventional brain MR-imaging, non-specific findings on EEG testing, and the lack of identified IgG class neuronal autoantibodies in blood or CSF in a subgroup of patients. Early recognition and treatment are paramount to improve outcomes and achieve complete recovery from these debilitating, occasionally life threatening, disorders. This review is aimed to provide primary care physicians and hospitalists who, together with neurologist and psychiatrists, are often the first port of call for individuals presenting with new-onset neuropsychiatric symptoms, with up-to-date data and evidence-based approach to the diagnosis and management of individuals with neuropsychiatric disorders of suspected autoimmune origin.

Arterial Spin Labeling Imaging Characteristics of Anti-leucine-rich Glioma-Inactivated 1 Encephalitis: A Qualitative and Quantitative Analysis

Background and Significance

Autoimmune encephalitis (AE) is a rare group of diseases that can present with stroke-like symptoms. Anti-leucine-rich glioma inactivated 1 (LGI1) encephalitis is an AE subtype that is infrequently associated with neoplasms and highly responsive to prompt immunotherapy treatment. Therefore, accurate diagnosis of LGI1 AE is essential in timely patient management. Neuroimaging plays a critical role in evaluating stroke and stroke mimics such as AE. Arterial Spin Labeling (ASL) is an MRI perfusion modality that measures cerebral blood flow (CBF) and is increasingly used in everyday clinical practice for stroke and stroke mimic assessment as a non-contrast sequence. Our goal in this preliminary study is to demonstrate the added value of ASL in detecting LGI1 AE for prompt diagnosis and treatment.

Methods

In this retrospective single center study, we identified six patients with seropositive LGI1 AE who underwent baseline MRI with single delay 3D pseudocontinuous ASL (pCASL), including five males and one female between ages 28 and 76 years, with mean age of 55 years. Two neuroradiologists qualitatively interpreted the ASL images by visual inspection of CBF using a two-point scale (increased, decreased) when compared to both the ipsilateral and contralateral unaffected temporal and non-temporal cortex. The primary measures on baseline ASL evaluation were a) presence of ASL signal abnormality, b) if present, signal characterization based on the two-point scale, c) territorial vascular distribution, d) localization, and e) laterality. Quantitative assessment was also performed on postprocessed pCASL cerebral blood flow (CBF) maps. The obtained CBF values were then compared between the affected temporal cortex and each of the unaffected ipsilateral parietal, contralateral temporal, and contralateral parietal cortices.

Results

On consensus qualitative assessment, all six patients demonstrated ASL hyperperfusion and corresponding FLAIR hyperintensity in the hippocampus and/or amygdala in a non-territorial distribution (6/6, 100%). The ASL hyperperfusion was found in the right hippocampus or amygdala in 5/6 (83%) of cases. Four of the six patients underwent initial follow-up imaging where all four showed resolution of the initial ASL hyperperfusion. In the same study on structural imaging, all four patients were also diagnosed with mesial temporal sclerosis (MTS). Quantitative assessment was separately performed and demonstrated markedly increased CBF values in the affected temporal cortex (mean, 111.2 ml/min/100 g) compared to the unaffected ipsilateral parietal cortex (mean, 49 ml/min/100 g), contralateral temporal cortex (mean, 58.2 ml/min/100 g), and contralateral parietal cortex (mean, 52.2 ml/min/100 g).

Discussion

In this preliminary study of six patients, we demonstrate an ASL hyperperfusion pattern, with a possible predilection for the right mesial temporal lobe on both qualitative and quantitative assessments in patients with seropositive LGI1. Larger scale studies are necessary to further characterize the strength of these associations.