Systematic review of the clinical spectrum of CASPR2 antibody syndrome

Anti-contact protein-associated protein 2 antibody encephalitis in children: A case report

BACKGROUND

Anti-contactin-associated protein-like 2 (CASPR2) antibody encephalitis is an autoimmune disorder characterized by the presence of antibodies against the voltage-gated potassium channel. This leads to neurological symptoms, such as seizures, cognitive decline, and neuropathic pain, primarily affecting the limbic system. The prognosis of this disorder varies among individuals.

CASE SUMMARY

The patient, a girl aged nine years and nine months, underwent treatment for 14 to 21 d. The main clinical manifestations were vomiting and unclear consciousness, positive pathological signs, normal cranial computed tomography and magnetic resonance imaging, and abnormal electroencephalogram. The child was discharged after receiving immunoglobulin and hormone treatment. Subsequent follow-up over a period of 15 months after discharge, conducted through telephone and outpatient visits, showed no recurrence of symptoms.

CONCLUSION

Anti-CASPR2 antibody autoimmune encephalitis in children is rare, mainly manifested as convulsions, mental abnormalities, cognitive impairment, and neuropathic pain, among others. Timely evaluation for autoimmune encephalitis antibodies is crucial, especially in cases of recurrent central nervous system involvement in children.

Anti-CASPR2 Antibody-Associated Syndrome Presenting With Episodic Ataxia

The anti-CASPR2 antibody-associated syndrome is a rare immune-mediated disorder. Most case reports describe neurologic symptoms that include encephalic signs, peripheral nerve hyperexcitability, dysautonomia, or neuropathic pain. We report the case of a 70-year-old man, admitted to the emergency department with complaints of slurred speech and imbalance. Neurological examination was relevant for dysarthria, hyperreflexia, and pancerebellar syndrome. Cranial CT and basic laboratory tests were normal and he spontaneously recovered after 14 hours. Over the next four months, the patient experienced three similar episodes in relation to stressful events (emotional and organic disturbances like prolonged fasting and vaccination). A contrast-enhanced MRI was performed, along with extensive laboratory testing, analysis of cerebrospinal fluid (CSF), paraneoplastic investigation, and next-generation sequencing panel for episodic ataxias. The results revealed oligoclonal bands in the CSF and positive anti-CASPR2 antibodies both in serum and CSF. Three-day-IV- methylprednisolone pulse followed by plasmapheresis and monthly intravenous immunoglobulins was performed with good response. In conclusion, the neurological manifestations that led to the diagnosis of anti-CASPR2 antibody-associated syndrome were intermittent self-limiting episodes of ataxia, often triggered by concurrent stress-inducing factors. This case supports the aim of other authors to add paroxysmal cerebellar ataxia to the spectrum of the anti-CASPR2 antibody syndrome.

Magnetic Resonance Imaging Characteristics of LGI1-Antibody and CASPR2-Antibody Encephalitis

Importance

Rapid and accurate diagnosis of autoimmune encephalitis encourages prompt initiation of immunotherapy toward improved patient outcomes. However, clinical features alone may not sufficiently narrow the differential diagnosis, and awaiting autoantibody results can delay immunotherapy.

Objective

To identify simple magnetic resonance imaging (MRI) characteristics that accurately distinguish 2 common forms of autoimmune encephalitis, LGI1- and CASPR2-antibody encephalitis (LGI1/CASPR2-Ab-E), from 2 major differential diagnoses, viral encephalitis (VE) and Creutzfeldt-Jakob disease (CJD).

Design, Setting, and Participants

This cross-sectional study involved a retrospective, blinded analysis of the first available brain MRIs (taken 2000-2022) from 192 patients at Oxford University Hospitals in the UK and Mayo Clinic in the US. These patients had LGI1/CASPR2-Ab-E, VE, or CJD as evaluated by 2 neuroradiologists (discovery cohort; n = 87); findings were validated in an independent cohort by 3 neurologists (n = 105). Groups were statistically compared with contingency tables. Data were analyzed in 2023.

Main Outcomes and Measures

MRI findings including T2 or fluid-attenuated inversion recovery (FLAIR) hyperintensities, swelling or volume loss, presence of gadolinium contrast enhancement, and diffusion-weighted imaging changes. Correlations with clinical features.

Results

Among 192 participants with MRIs reviewed, 71 were female (37%) and 121 were male (63%); the median age was 66 years (range, 19-92 years). By comparison with VE and CJD, in LGI1/CASPR2-Ab-E, T2 and/or FLAIR hyperintensities were less likely to extend outside the temporal lobe (3/42 patients [7%] vs 17/18 patients [94%] with VE; P < .001, and 3/4 patients [75%] with CJD; P = .005), less frequently exhibited swelling (12/55 [22%] with LGI1/CASPR2-Ab-E vs 13/22 [59%] with VE; P = .003), and showed no diffusion restriction (0 patients vs 16/22 [73%] with VE and 8/10 [80%] with CJD; both P < .001) and rare contrast enhancement (1/20 [5%] vs 7/17 [41%] with VE; P = .01). These findings were validated in an independent cohort and generated an area under the curve of 0.97, sensitivity of 90%, and specificity of 95% among cases with T2/FLAIR hyperintensity in the hippocampus and/or amygdala.

Conclusions and Relevance

In this study, T2 and/or FLAIR hyperintensities confined to the temporal lobes, without diffusion restriction or contrast enhancement, robustly distinguished LGI1/CASPR2-Ab-E from key differential diagnoses. These observations should assist clinical decision-making toward expediting immunotherapy. Their generalizability to other forms of autoimmune encephalitis and VE should be examined in future studies.

Clinicopathological Features in Morvan's Syndrome: An Autopsy Case Study

Morvan's syndrome is a rare, complex autoimmune syndrome comprising peripheral nerve hyperexcitability, dysautonomia, insomnia, and encephalopathy. In this case report, we highlight the clinical and pathological findings of an elderly gentleman who presented to us with clinical features of Morvan's syndrome associated with anti-contactin-associated protein 2 (CASPR-2) antibodies. Histopathology [Figure 3] revealed cortical atrophy with gliosis and mild microglial proliferation. Microglial activation and gliosis were observed in the hippocampus, hypothalamus, and thalamus. Brainstem showed multifocal inflammation. Mild inflammation was observed in the leptomeninges. Morvan's syndrome is an autoimmune disease with antibodies targeted against CASPR within the voltage-gated potassium channel (VGKC) complex. Early diagnosis and treatment play a key role in the management of patients. Most patients show a good response when treated with plasmapheresis and steroids. This patient presented to us late into the illness and succumbed.

Antibodies to neural cell surface and synaptic proteins in paraneoplastic neurologic syndromes

Among patients with paraneoplastic neurologic syndromes (PNS), emphasis has historically been placed on neural antibodies against intracellular proteins that have a strong association with malignancy. Because of the intracellular location of their antigenic targets, these antibodies are typically considered to be non-pathogenic surrogate markers of immune cell-mediated neural injury. Unfortunately, patients with these antibodies often have suboptimal response to immunotherapy and poor prognosis. Over the last two decades, however, dramatic advancements have been made in the discovery and clinical characterization of neural antibodies against extracellular targets. These antibodies are generally considered to be pathogenic, given their potential to directly alter antigen structure or function, and patients with these antibodies often respond favorably to prompt immunotherapy. These antibodies also associate with tumors and may thus occur as PNS, albeit more variably than neural antibodies against intracellular targets. The updated 2021 PNS diagnostic criteria, which classifies antibodies as high-risk, intermediate-risk, or lower-risk for an associated cancer, better clarifies how neural antibodies against extracellular targets relate to PNS. Using this recently created framework, the clinical presentations, ancillary test findings, oncologic associations, and treatment responses of syndromes associated with these antibodies are discussed.

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.

Contactin-associated protein-like 2 antibody-associated autoimmune encephalitis in children: case reports and systematic review of literature

OBJECTIVES

To ascertain the clinical characteristics of pediatric patients with contactin-associated protein-like 2 (CASPR2) antibody-associated autoimmune encephalitis (AEs).

METHODS

Two cases of CASPR2 antibody-associated AEs have been reported. In addition, a systematic search of literature published between January 2010 and March 2022 through six online databases was conducted to identify the pediatric patients with CASPR2 antibody-associated AEs. Data on demographics, clinical symptoms, laboratory examinations, imaging, treatment, and outcome were collected.

RESULTS

Our updated literature search yielded 1,837 publications, of which 21 were selected, and 40 patients in this study met the diagnostic criteria for AE. There were 25 males and 15 females with a mean age of 9.2 years. The most common presenting symptoms are psychiatric symptoms (72.5%), sleep changes (62.5%), and movement disorders (60%). The psychiatric symptoms included mood changes (39.1%), behavior changes (25%), and hallucination (7.5%). In total, 23 cases (57.5%) combined with autonomic dysfunction, such as gastrointestinal dysmotility, cardiovascular-related symptoms, and sweating. No tumors were observed in children. Thirty-eight patients received first-line immunotherapy, and eight received first-line and second-line immunotherapy. All patients had a good clinical response to immune therapy. Mean mRS at onset was 3.4; It was 0.88 at the last follow-up. There was no recurrence during follow-up.

CONCLUSION

Psychiatric symptoms, sleep disorders, movement disorders, and cardiovascular-related symptoms are the most common presentation in pediatric patients with CASPR2 antibody-associated AEs. Tumor, particularly with thymoma, is uncommon in children diagnosed with CASPR2 antibody-associated AEs. In addition, prompt diagnosis and immunotherapy can relieve symptoms and improve the 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.

Paraneoplastic Neurological Syndromes of the Central Nervous System: Pathophysiology, Diagnosis, and Treatment

Paraneoplastic neurological syndromes (PNS) include any symptomatic and non-metastatic neurological manifestations associated with a neoplasm. PNS associated with antibodies against intracellular antigens, known as "high-risk" antibodies, show frequent association with underlying cancer. PNS associated with antibodies against neural surface antigens, known as "intermediate- or low-risk" antibodies, are less frequently associated with cancer. In this narrative review, we will focus on PNS of the central nervous system (CNS). Clinicians should have a high index of suspicion with acute/subacute encephalopathies to achieve a prompt diagnosis and treatment. PNS of the CNS exhibit a range of overlapping "high-risk" clinical syndromes, including but not limited to latent and overt rapidly progressive cerebellar syndrome, opsoclonus-myoclonus-ataxia syndrome, paraneoplastic (and limbic) encephalitis/encephalomyelitis, and stiff-person spectrum disorders. Some of these phenotypes may also arise from recent anti-cancer treatments, namely immune-checkpoint inhibitors and CAR T-cell therapies, as a consequence of boosting of the immune system against cancer cells. Here, we highlight the clinical features of PNS of the CNS, their associated tumors and antibodies, and the diagnostic and therapeutic strategies. The potential and the advance of this review consists on a broad description on how the field of PNS of the CNS is constantly expanding with newly discovered antibodies and syndromes. Standardized diagnostic criteria and disease biomarkers are fundamental to quickly recognize PNS to allow prompt treatment initiation, thus improving the long-term outcome of these conditions.

Contactin-Associated Protein-Like 2-Related Peripheral Nerve Hyperexcitability Associated With Charcot-Marie-Tooth Type 4F

Contactin-associated protein-like 2 autoimmunity is an uncommon disorder resulting in peripheral nerve hyperexcitability or encephalitis. In a fifth of cases, onset may be provoked by thymoma, but other associations are largely unknown. We report a patient with anti-contactin-associated protein-like 2-related peripheral nerve hyperexcitability arising in the setting of Charcot-Marie-Tooth type 4F and discuss potential mechanisms underlying the association.

Thymoma-associated autoimmune encephalitis: Analysis of factors determining prognosis

INTRODUCTION

Autoimmune encephalitis (AE) is a heterogeneous group of inflammatory central nervous system disorders caused by a misdirected immune response against self-antigens expressed in the central nervous system. The thymus is a central organ in the immune system and thymic tumors are thought to be possible initiators of many neurological disorders. Recently, there is growing evidence that thymomas are associated with autoimmune encephalitis.

AIMS

Our study initially explored the characteristics of patients with autoimmune encephalitis combined with thymoma.

METHODS

We used patient data from January 1, 2011 to October 1, 2021 from the PubMed, Web of Science, Ovid, and CNKI platforms to analyze overall demographics, frequency of symptoms and associations, and treatment prognosis outcomes.

RESULTS

A total of 68 patients were included. There were 39 female cases (57.4%). The mean age was 50 years (IQR 40-66 years). All had acute and subacute onset. The clinical manifestations were mostly cognitive changes (70.6%), mental disorders (57.4%), and epilepsy (50.0%). The most common neuronal antibody was alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Magnetic resonance imaging (MRI) abnormalities were present in 81.0% of patients, mostly in the hippocampus, temporal lobe, and some in cortical and subcortical areas. Abnormalities in the electroencephalogram (EEG) in 69.8% of patients. Treatment involved immunotherapy and thymoma treatment, with 79.7% of patients improving after treatment. While 20.3% of patients had a poor prognosis. Further, 14.8% of patients relapsed. Mental disorders, autonomic dysfunction, sleep disturbances, anti-Ma2, and thymoma untreated were more frequent in patients with poor prognosis.

CONCLUSION

Thymoma-associated autoimmune encephalitis is a unique disease entity. Long-term follow-up of chest CT findings is recommended for patients with autoimmune encephalitis.

Paraneoplastic neurological syndromes of the central nervous system: a single institution 7-year case series

BACKGROUND

Paraneoplastic neurological syndromes (PNSs) are nonmetastatic complications of malignancy, defined by the presence of onconeural antibodies (ONAs). ONAs may be found in 60% of patients with central nervous system (CNS) involvement, and they are directed against intraneuronal antigens or channels, receptors or associated proteins located at the synaptic or extra-synaptic neuronal cell membrane. Given its rare incidence, there are few epidemiological case series on CNS-PNS. We aim to discuss the variability of CNS-PNSs etiology, clinical features, management and outcome, highlighting the importance of early recognition and appropriate treatment, leading to significant reduction of mortality and morbidity.

METHODS

We retrospectively reviewed our 7-years single-center experience, and specifically discussed the underlying etiology, parenchymal CNS involvement, and the acute treatment response. Only cases fulfilling PNS Euronetwork criteria for definitive PNS were included.

RESULTS

A total of 26 probable PNSs cases involving CNS were identified. We reported medical records of eleven (42.3%) illustrative cases, meeting the criteria of definite PNS and presenting variable clinical spectrum and different radiological appearances. Our series has a relative paucity of the most common syndromes and larger portion of clinical diagnosis with ONAs. Well-characterized ONAs had been detected in CSF of six patients.

CONCLUSIONS

Our case series supports the utmost importance of early recognition of CNS-PNSs. Screening for occult malignancies should not be limited to patients with classical CNS syndrome. Empiric immunomodulatory therapy may be considered before the diagnostic evaluation is completed, in order to prevent unfavorable outcome. Late presentations should not discourage initiation of treatment.

CASPR2 antibody associated neurological syndromes in children

To strengthen the understanding of the clinical features for CASPR2 neurological autoimmunity in children. A multicenter retrospective and prospective analysis of CASPR2 autoimmunity was conducted. Twenty-six patients were enrolled, including 25 with serum positivity and 3 with cerebrospinal fluid (CSF) positivity; 5 patients were co-positive with anti-NMDAR or anti-GABABR antibodies. Eleven patients (who manifested with refractory epilepsy, psychobehavioral abnormalities or germinoma) presented with low antibody titers, relatively normal MRI/EEG/CSF examinations, and poor response to immunotherapy and were thus considered false positive (42.3%). Fifteen patients were diagnosed with autoimmune encephalitis/ encephalopathy/ cerebellitis (including 1 whose condition was secondary to Japanese encephalitis). The most common symptoms included disorders of consciousness (10/15), fever (8/15), psychological symptoms/abnormal behaviors (8/15), sleep disorders (8/15), seizures (7/15), movement disorders (5/15), autonomic symptoms (5/15). Brain MRI revealed abnormalities in 10 patients (66.7%). Electroencephalography (EEG) recordings revealed a slow wave background in 13 patients (86.7%). Five patients showed elevated WBCs in CSF, and 4 patients showed elevated protein levels in the CSF. Thirteen patients received immunotherapy (rituximab was adopted in 2 cases) and recovered well. Two patients received symptomatic treatment, and the recovery was slow and accompanied by emotional abnormalities and developmental delay. Autoimmune encephalitis is the most common clinical phenotype; it can be secondary to Japanese encephalitis. Rituximab can be used in patients who respond poorly to conventional immunotherapy. The high false-positive rate of anti-CASPR2 in refractory epilepsy and the psychobehavioral abnormalities needs to be explored further.

Case report: Autoimmune encephalitis associated with anti-CASPR2 antibody mimicking cerebral infarction

Autoimmune encephalitis associated with antibody against contactin-associated protein-like 2 (CASPR2) varies in its clinical presentation. The disease is difficult to distinguish from some other conditions without testing for anti-CASPR2 antibody in blood serum or cerebrospinal fluid. Cerebral lesions are typically detected by magnetic resonance imaging (MRI) in the medial temporal lobe or hippocampus. Here, we describe a patient with anti-CASPR2 antibody autoimmune encephalitis whose imaging manifestations mimicked infarction in the left frontal lobe. The 48-year-old man reported memory loss, convulsions, and disturbed consciousness one day after drinking wine. The right upper arm showed reduced autonomous movement after painful stimuli, and MRI showed abnormal hyperintensities in the left frontal lobe on T2 and fluid-attenuated inversion recovery sequences, restricted diffusion, and decreased cerebral blood flow, mimicking acute cerebral infarction. Contrast-enhanced T1-weighted MRI showed gyral enhancement involving the cortex and subcortical white matter. Computed tomography angiography did not identify culprit blood vessels. Symptoms did not improve with anti-platelet or lipid-lowering therapy. Screening for serum antibodies associated with autoimmune encephalitis detected antibody against CASPR2, and intravenous immunoglobulin therapy substantially improved symptoms. This case provides the first indication that anti-CASPR2 antibody-associated autoimmune encephalitis can manifest as involvement of the cortex and subcortical white matter in the frontal lobe based on MRI. It emphasizes the need for thorough investigation, including analysis of potential autoimmunity, of patients whose imaging findings mimic ischemic infarction.

Early-Stage Contactin-Associated Protein-like 2 Limbic Encephalitis: Clues for Diagnosis

Background and Objectives

Previous studies suggested that autoimmune limbic encephalitis with antibodies against contactin-associated protein-like 2 (CASPR2-encephalitis) is clinically heterogeneous and progresses slowly, preventing its early recognition. We aimed to describe the onset and progression of CASPR2-encephalitis and to assess long-term outcomes.

Methods

We retrospectively analyzed the medical records of all patients whose CSF tested positive for anti-CASPR2 antibodies in our center between 2006 and 2020. Standardized telephone interviews of all available patients and relatives were conducted, assessing long-term functional independence using the Functional Activity Questionnaire (FAQ) and quality of life using the 36-Item Short-Form Survey (SF36).

Results

Forty-eight patients were included (98% males; median age 64 years), and 35 participated in telephone interviews (73%). At onset, 81% had at least 1 neurologic symptom among the following: limbic (54%), peripheral nerve hyperexcitability (PNH; 21%), and/or cerebellar symptoms (17%). Most of the patients (75%) had initially symptoms of only one of these categories. Limbic symptoms at onset included mostly seizures (33%), while memory disturbances were less frequent (10%). PNH signs were mostly neuropathic pain (9/10 patients). Other symptoms seen at onset included asthenia (33%), mood disorders (25%), and insomnia (21%); 19% of patients did not show any limbic, peripheral, or cerebellar symptom at onset but only asthenia (15%), mood disorders (6%), weight loss (8%), dysautonomia (4%), and/or insomnia (2%). The peak of the disease was attained in median 16.7 months after onset. Over the study period (median follow-up, 58.8 months, range 10.6–189.1), 77% of patients developed ≥3 core CASPR2 symptoms and 42% fulfilled the diagnostic criteria for autoimmune limbic encephalitis, although all patients ultimately developed limbic symptoms. At the last visit, most interviewed patients (28/35 patients, 80%; median, 5 years after onset) had recovered functional independence (FAQ <9) while only the vitality subscore of the SF36 was lower than normative data (mean 49.9 vs 58.0, p = 0.0369).

Discussion

CASPR2-encephalitis has a progressive course and is highly heterogeneous at the early stage. In men older than 50 years, otherwise unexplained seizures, cerebellar ataxia, and/or neuropathic pain are suggestive of early-stage CASPR2-encephalitis, especially if they coincide with recent asthenia, mood disorders, or insomnia.

Positron emission tomography in autoimmune encephalitis: Clinical implications and future directions

¹⁸ F-fluoro-deoxyglucose position emission tomography (¹⁸ F-FDG-PET) has been proven as a sensitive and reliable tool for diagnosis of autoimmune encephalitis (AE). More attention was paid to this kind of imaging because of the shortage of MRI, EEG, and CSF findings. FDG-PET has been assessed in a few small studies and case reports showing apparent abnormalities in cases where MRI does not. Here, we summarized the patterns (specific or not) in AE with different antibodies detected and the clinical outlook for the wide application of FDG-PET considering some limitations. Specific patterns based on antibody subtypes and clinical symptoms were critical for identifying suspicious AE, the most common of which was the anteroposterior gradient in anti- N -methyl- d -aspartate receptor (NMDAR) encephalitis and the medial temporal lobe hypermetabolism in limbic encephalitis. And the dynamic changes of metabolic presentations in different phases provided us the potential to inspect the evolution of AE and predict the functional outcomes. Except for the visual assessment, quantitative analysis was recently reported in some voxel-based studies of regions of interest, which suggested some clues of the future evaluation of metabolic abnormalities. Large prospective studies need to be conducted controlling the time from symptom onset to examination with the same standard of FDG-PET scanning.

Rituximab Was Effective in Relieving Symptoms of Isaacs Syndrome: A Case Report

We presented a 23-year-old patient who had experienced neuromyotonia in his left leg. Although he tested negative for anti-LGI1 and anti-CASPR2 antibodies, we diagnosed him with Isaacs syndrome due to myokymic discharges on electromyography and symptoms being relieved by intravenous methylprednisolone (IVMP) and intravenous immunoglobulin (IVIg). IVMP, IVIg, plasma exchange, or cyclosporine treatment did not provide a long-term response; however, rituximab showed long-term improvement. Rituximab should be considered early in the treatment of patients with antibody-negative Isaacs syndrome who are responsive to immunotherapy, including IVMP, IVIg, and plasma exchange, and have long-term symptoms that are hard to control.

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.

Guillain-Barré-like syndrome: an uncommon feature of CASPR2 and LGI1 autoimmunity

Contactin-associated protein-like 2 (CASPR2) and leucine-rich glioma-inactivated 1 (LGI1) are essential components of the voltage-gated Kv1 potassium channel complex and are extensively expressed in both central and peripheral nervous system. Autoimmune CASPR2 and LGI1 disorders commonly present with Morvan syndrome (Mos) and/or limbic encephalitis, but whether Guillain-Barré syndrome (GBS) is a specific clinical phenotype is unknown. Here, we first reported an adult patient with dual CASPR2 and LGI1 antibodies in both serum and cerebrospinal fluid, who initially presented with a GBS-like syndrome and developed a typical MoS and respiratory paralysis, with a rapid resolution of his neurological symptoms and disappearance of autoantibodies after treatment with plasma exchange. Additionally, we also provided an overview of the previously reported GBS cases associated with CASPR2 or LGI1 antibodies. These cases expand the phenotypic spectrum of CASPR2 and LGI1 autoimmune syndromes, implying that these two antigens, especially CASPR2, are likely to participate in the etiology of GBS as a potential new target antigen, which deserves further exploration.

Immune-Mediated Cerebellar Ataxia Associated With Neuronal Surface Antibodies

BACKGROUND

Immune-mediated cerebellar ataxias (IMCAs) are common in paraneoplastic cerebellar degeneration (PCD) but rarely occur in patients with neuronal surface antibodies (NSAbs). Although cerebellar ataxias (CAs) associated with anti-NMDAR and anti-CASPR2 have been reported in a few cases, they have never been studied systematically. This study aimed to analyze the characteristics of anti-NSAbs-associated CAs.

METHODS

A retrospective investigation was conducted to identify patients using the keywords IMCAs and NSAbs. We collected the clinical data of 14 patients diagnosed with anti-NSAbs-associated CAs.

RESULTS

The median age was 33 years (16-66), and the male-to-female ratio was 4:3. Nine were positive for NMDAR-Ab, two for LGI1-Ab, two for CASPR2-Ab, and one for AMPA2R-Ab. CAs were initial symptoms in three patients and presented during the first two months of the disease course (10 days on average) among the rest of the patients. After the immunotherapy, two cases were free from symptoms, and eight cases recovered satisfactorily (10/14, 71.4%). Compared with other causes of IMCAs, anti-NSAbs were more frequently associated with additional extra-cerebellar symptoms (85.7%), mostly seizures (78.6%) and mental abnormalities (64.3%). In the CSF analysis, pleocytosis was detected in ten patients (71.4%) and oligoclonal bands (OB) were observed in nine patients (64.3%). Moreover, compared with PCD and anti-GAD65-Ab-associated CAs, anti-NSAbs-associated CAs showed a better response to immunotherapy.

CONCLUSION

IMCAs are rare and atypical in autoimmune encephalitis with neuronal surface antibodies. Compared with other forms of IMCAs, more symptoms of encephalopathy, a higher rate of pleocytosis and positive OB in CSF, and positive therapeutic effect were the key features of anti-NSAbs-associated CAs.

Diagnosis and Clinical Features in Autoimmune-Mediated Movement Disorders

Movement disorders are common manifestations in autoimmune-mediated encephalitis. This group of diseases is suspected to be triggered by infection or neoplasm. Certain phenotypes correlate with specific autoantibody-related neurological disorders, such as orofacial-lingual dyskinesia with N-methyl-D-aspartate receptor encephalitis and faciobrachial dystonic seizures with leucine-rich glioma-inactivated protein 1 encephalitis. Early diagnosis and treatment, especially for autoantibodies targeting neuronal surface antigens, can improve prognosis. In contrast, the presence of autoantibodies against intracellular neuronal agents warrants screening for underlying malignancy. However, early clinical diagnosis is challenging because these diseases can be misdiagnosed. In this article, we review the distinctive clinical phenotypes, magnetic resonance imaging findings, and current treatment options for autoimmune-mediated encephalitis.

Contemporary advances in antibody-mediated encephalitis: anti-LGI1 and anti-Caspr2 antibody (Ab)-mediated encephalitides

Encephalitides with antibodies directed against leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein-like 2 (Caspr2) represent two increasingly well characterised forms of autoimmune encephalitis. Both share overlapping and distinct clinical features, are mediated by autoantibodies directed against differing proteins complexed with voltage-gated potassium channels, with unique genetic predisposition identified to date. Herein we summarise disease mechanisms, clinical features, treatment considerations, prognostic factors and clinical outcomes regarding these disorders.

Movement disorders associated with neuronal antibodies: a data-driven approach

Background

Movement disorders can be associated with anti-neuronal antibodies.

Methods

We conducted a systematic review of cases with documented anti-neuronal antibodies in serum and/or cerebrospinal fluid published in PubMed before April 1, 2020. Only patients with at least one movement disorder were included. We used random forests for variable selection and recursive partitioning and regression trees for the creation of a data-driven decision algorithm, integrated with expert’s clinical feedback.

Results

Three hundred and seventy-seven studies met eligibility criteria, totaling 844 patients and 13 antibodies: amphiphysin, GAD, GlyR, mGluR1, ANNA-2/Ri, Yo/PCA-1, Caspr2, NMDAR, LGI-1, CRMP5/CV2, ANNA-1/Hu, IgLON5, and DPPX. Stiffness/rigidity/spasm spectrum symptoms were more frequently associated with amphiphysin, GAD, and GlyR; ataxia with mGluR1, ANNA-2/Ri, Yo/PCA-1, Caspr2, and ANNA-1/Hu; dyskinesia with NMDAR and paroxysmal movement with LGI1; chorea/choreoathetosis with CRMP5/CV2, IgLON5, and NMDAR; myoclonus with GlyR and DPPX; tremors with ANNA2/Ri and anti-DPPX; and parkinsonism with IgLON5 and NMDAR. Data-driven classification analysis determined the following diagnostic predictions (with probability selection): psychiatric symptoms and dyskinesia predicted NMDAR (71% and 87%, respectively); stiffness/rigidity/spasm and ataxia, GAD (67% and 47%, respectively); ataxia and opsoclonus, ANNA-2/Ri (68%); chorea/choreoathetosis, CRMP5/CV2 (41%). These symptoms remained the top predictors in random forests analysis. The integration with an expert opinion analysis refined the precision of the approach. Breast and lung tumors were the most common tumors. On neuroimaging, cerebellar involvement was associated with GAD and Yo/PCA-1; temporal involvement with Caspr2, LGI-1, ANNA-1/Hu.

Conclusion

Selected movement disorders are associated with specific anti-neuronal antibodies. The combination of data-driven and expert opinion approach to the diagnosis may assist early management efforts.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10934-7.

Phenotypic Spectrum of CASPR2 and LGI1 Antibodies Associated Neurological Disorders in Children

OBJECTIVES

The clinical data of patients with double-positive for leucine-rich glioma-inactivated protein 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) antibodies is limited, particularly for children. This study aimed to investigate and summarize the clinical features and long-term prognosis of children's LGI1 and CASPR2 antibodies related to neurological disorders.

METHODS

We collected the clinical data and prognosis of patients with dual positive antibodies of CASPR2 and LGI1, hospitalized in the Department of Neurology, Children's Hospital of Chongqing Medical University. Furthermore, we summarized the clinical phenotypes of this disorder in children by reviewing the published literature.

RESULTS

Two patients presenting with variable neurological symptoms including pain, hypertension, profuse sweating, irritability, and dyssomnia from Children's Hospital of Chongqing Medical University were enrolled in this study. Together with the two patients, we identified 17 children with dual CASPR2 and LGI1 antibodies, including 12 males and 5 females. At the onset, the median age was 4.1 years (range 1-16, interquartile range 2.5-13.5), with 9 children younger than 5 years and 6 adolescents. Of the 17 patients, 11 were diagnosed with Morvan syndrome, 4 with acquired neuromyotonia, 1 with Guillain-Barré syndrome, and 1 with Guillain-Barré syndrome combined with Morvan syndrome. Dysautonomia (14/17, 82.3%), pain (13/17, 76.4%), sleep disorders (13/17, 76.4%), encephalopathy (12/17, 70.5%), and weight loss (10/17, 58.8%) were the most frequently described symptoms overall. No tumors were identified. Of the 17 patients, 13 received immunotherapy comprising IVIG combination of IVMP during the acute symptomatic phase followed by oral prednisolone to maintain remission (n = 7), the combination of IVIG, IVMP, oral prednisolone and methotrexate (n = 1), the combination of IVIG, IVMP, and mycophenolate mofetil (n = 1), the combination of IVIG, IVMP, oral prednisolone, and rituximab (n = 1), IVIG only (n = 2), IVMP only (n = 1). Median modified Rankin Scale (mRS) scores in the acute phase were 3 (range 1-4) and improved gradually. Over the follow-up (median 8.6 months, range 1-36 months), 52.9% (9/17) of the patients recovered completely; one patient relapsed and showed immunotherapy-dependent.

CONCLUSION

LGI1 and CASPR2 double-positive antibodies associated with the neurological diseases can occur in children of all ages and involve multiple nervous systems. Morvan syndrome is the most common phenotype of this disorder. The long-term outcomes are mostly favorable upon immunotherapy.

Anti-contactin-associated protein-like 2 antibody-associated encephalitis in children: A case report and literature review

BACKGROUND

Anti-Contactin-associated protein-like 2 (CASPR2) antibody-associated encephalitis is a rare group of autoimmune diseases that causes extensive damage to the central and/or peripheral nervous system.

CASE PRESENTATION

Here, we reported a case of anti-CASPR2 antibody-associated encephalitis in a 12-year-old male patient with symptoms of headache, consciousness disturbance, mental abnormalities, urinary incontinence, fasciculations in the extremity muscles, and involuntary movements. The testing for autoimmune encephalitis-associated antibodies showed that CASPR2-associated antibodies were positive, and electroencephalography showed diffuse slow waves. No tumor was found after screening for malignancies. The child's status significantly improved after receiving immunotherapy with intravenous methylprednisolone and immunoglobulin.

CONCLUSIONS

Anti-CASPR2 antibody-associated encephalitis has been rarely reported in children. It has a complex clinical presentation and a low incidence of tumor. Most pediatric patients have a favorable prognosis and relapse is uncommon.

Case Report: Prominent Brainstem Involvement in Two Patients With Anti-CASPR2 Antibody-Associated Autoimmune Encephalitis

Anti-contactin-associated protein-like 2 (CASPR2) antibody-associated autoimmune encephalitis is commonly characterized by limbic encephalitis with clinical symptoms of mental and behavior disorders, cognitive impairment, deterioration of memory, and epilepsy. The classical lesions reported are located at the medial temporal lobe or hippocampus, whereas prominent brainstem lesions have not been addressed to date. Herein, we reported two patients mimicking progressive brainstem infarction with severe neurological manifestations. On brain magnetic resonance imaging (MRI), prominent brainstem lesions were noted, although multifocal lesions were also shown in the juxtacortical and subcortical white matters, basal ganglia, hippocampus, and cerebellar hemisphere. Unexpectedly and interestingly, both cases had detectable CASPR2 antibodies in sera, and an exclusive IgG1 subclass was documented in the further analysis. They were treated effectively with aggressive immunosuppressive therapies including corticosteroids, intravenous immunoglobulin G, and rituximab, with the first case achieving a rapid remission and the other undergoing a slow but gradual improvement. To the best of our knowledge, this is the first report on prominent brainstem involvement with definite MRI lesions in anti-CASPR2 antibody-associated autoimmune encephalitis, which helps to expand the clinical spectrum of this rare autoimmune disease and update the lesion patterns in the CNS.

Parkinsonism and ataxia

Ataxia is not a common feature in Parkinson's disease. Nevertheless, some rare forms of parkinsonism have ataxia as one of the main features in their clinical picture, especially those with juvenile or early-onset. On the other side, in cerebellar degenerative diseases, parkinsonism might accompany the typical symptoms and even become predominant in some cases. Many disorders involving different neurological systems present with a movement phenomenology reflecting the underlying pattern of pathological involvement, such as neurodegeneration with brain iron accumulation, neurodegeneration associated with calcium deposition, and metabolic and mitochondrial disorders. The prototype of sporadic disorders that present with a constellation of symptoms due to the involvement of multiple Central Nervous System regions is multiple system atrophy, whose motor symptoms at onset can be cerebellar ataxia or parkinsonism. Clinical syndromes encompassing both parkinsonian and cerebellar features might represent a diagnostic challenge for neurologists. Recognizing acquired and potentially treatable causes responsible for complex movement disorders is of paramount importance, since an early diagnosis is essential to prevent permanent consequences. The present review aims to provide a pragmatic overview of the most common diseases characterized by the coexistence of cerebellar and parkinsonism features and suggests a possible diagnostic approach for both inherited and sporadic disorders. This article is part of the Special Issue "Parkinsonism across the spectrum of movement disorders and beyond" edited by Joseph Jankovic, Daniel D. Truong and Matteo Bologna.

Neuromuscular hyperexcitability syndromes

PURPOSE OF REVIEW

To provide an update on recent developments regarding acquired, antibody-mediated, neuromuscular hyperexcitability syndromes, including Isaac's and Morvan's syndromes, cramp-fasciculation syndrome and rippling muscle disease, and their genetic differential diagnoses.

RECENT FINDINGS

Antibodies in auto-immune peripheral nerve hyperexcitability syndromes (PNHS) are directed against CASPR2 and LGI1, proteins of the voltage-gated potassium channel (VGKC) complex. We discuss the significance of 'double-negative' VGKC antibodies in PNHS and the rationale for ceasing VGKC antibody testing (but testing CASPR2 and LGI1 antibodies instead) in clinical practice. Recent case reports also expand the possible clinical phenotypes related to CASPR2/LGI1 antibodies, but the interpretation of these findings is complicated by the frequent association of antibody-mediated neuromuscular hyperexcitability syndromes with other auto-immune disorders (e.g. myasthenia gravis).Finally, a hereditary origin of neuromuscular hyperexcitability should always be considered, even in non-VGKC-related genes, as evidenced by the recently discovered high frequency of HINT1 mutations in people of Slavic origin.

SUMMARY

This review provides an update on recent clinical, immunological and genetic developments in neuromuscular hyperexcitability syndromes. We also provide a guide for the clinician for diagnosing and managing these disorders in clinical practice, with a special focus on the main differential diagnoses.

Update in Autoimmune Movement Disorders: Newly Described Antigen Targets in Autoimmune and Paraneoplastic Cerebellar Ataxia

Movement disorders are a common feature of many antibody-associated neurological disorders. In fact, cerebellar ataxia is one of the most common manifestations of autoimmune neurological diseases. Some of the first autoantibodies identified against antigen targets include anti-neuronal nuclear antibody type 1 (ANNA-1 or anti-Hu) and Purkinje cell cytoplasmic antibody (PCA-1) also known as anti-Yo have been identified in paraneoplastic cerebellar degeneration. Historically these antibodies have been associated with an underlying malignancy; however, recently discovered antibodies can occur in the absence of cancer as well, resulting in the clinical syndrome of autoimmune cerebellar ataxia. The pace of discovery of new antibodies associated with autoimmune or paraneoplastic cerebellar ataxia has increased rapidly over the last few years, and pathogenesis and potential treatment options remains to be explored. Here we will review the literature on recently discovered antibodies associated with autoimmune and paraneoplastic cerebellar ataxia including adaptor protein-3B2 (AP3B2); inositol 1,4,5-trisphophate receptor type 1 (ITPR1); tripartite motif-containing (TRIM) proteins 9, 67, and 46; neurochondrin; neuronal intermediate filament light chain (NIF); septin 5; metabotropic glutamate receptor 2 (mGluR2); seizure-related 6 homolog like 2 (SEZ6L2) and homer-3 antibodies. We will review their clinical characteristics, imaging and CSF findings and treatment response. In addition, we will discuss two clinical case examples of autoimmune cerebellar ataxia.

Presynaptic Paraneoplastic Disorders of the Neuromuscular Junction: An Update

The neuromuscular junction (NMJ) is the target of a variety of immune-mediated disorders, usually classified as presynaptic and postsynaptic, according to the site of the antigenic target and consequently of the neuromuscular transmission alteration. Although less common than the classical autoimmune postsynaptic myasthenia gravis, presynaptic disorders are important to recognize due to the frequent association with cancer. Lambert Eaton myasthenic syndrome is due to a presynaptic failure to release acetylcholine, caused by antibodies to the presynaptic voltage-gated calcium channels. Acquired neuromyotonia is a condition characterized by nerve hyperexcitability often due to the presence of antibodies against proteins associated with voltage-gated potassium channels. This review will focus on the recent developments in the autoimmune presynaptic disorders of the NMJ.

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

Objective

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

Materials and Methods

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

Results

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

Conclusion

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

Clinical Profile and Treatment Response in Patients with CASPR2 Antibody-Associated Neurological Disease

Background:

The clinical spectrum of contactin-associated protein-like 2 (CASPR2) antibody-associated disease is wide and includes Morvan syndrome. Studies describing treatment and long-term outcome are limited.

Aims:

We report the clinical profile and emphasize response to treatment and long-term outcome in eight patients with CASPR2-antibody-associated disease.

Methods:

Clinical, radiological, electrophysiological, treatment, follow-up, and outcome data were collected by retrospective chart review.

Results:

Clinical manifestations included Morvan syndrome (n = 7) and limbic encephalitis (n = 1). None of the patients were positive for LGI1 antibody. Associated features included myasthenia (n = 1), thymoma (n = 1), and dermatological manifestations (n = 4). Patients were treated with intravenous methylprednisolone and plasma exchange during the acute symptomatic phase followed by pulsed intravenous methyl prednisolone to maintain remission. Mean-modified Rankin score at admission (pre-treatment), discharge, and last follow-up were 3.75, 2.5, and 0.42, respectively. One patient with underlying thymoma and myasthenic crisis died. The other seven patients were followed up for a mean duration of 19.71 months. All of them improved completely. Relapse occurred in one patient after 13 months but responded favorably to steroids.

Conclusion:

CASPR2 antibody-associated disease has favorable response to immunotherapy with complete improvement and good outcome. Underlying malignancy may be a marker for poor prognosis.

Anti-contactin-associated protein-like 2 antibody-associated cerebellar ataxia: A case report and literature review

The spectrum of anti-contactin-associated protein-like 2 (CASPR2) antibody-associated disease is expanding and the involvement of cerebellum was reported in the past few years. We report a 45-year-old male with chronically progressive cerebellar ataxia. CASPR2 antibodies were detected in his serum and cerebellar atrophy was observed on MRI. His symptoms improved prominently with steroids and intravenous immunoglobulins. 23 cases with CASPR2 antibodies and cerebellar ataxia were identified from previous publications. Most of patients showed acute or subacute onset with other typical presentations of anti-CASPR2 antibody-associated disease, such as limbic encephalitis. Immunotherapy was effective in the majority of patients.

Paraneoplastic neurological syndromes: clinical presentations and management

We provide an overview of the varied presentations of paraneoplastic neurological syndromes. We also review the onconeural antibodies and their particular oncological and neurological associations. Recognition of these syndromes and their oncological associations is crucial, as early diagnosis and management has been associated with better patient outcomes. Specific management strategies and prognosis vary widely depending on the underlying etiology. An understanding of the relevant clinical details, imaging findings, and other diagnostic information can help tailor treatment approaches. We provide an outline of the diagnostic evaluation and treatment of various paraneoplastic neurological disorders, presenting with central and/or peripheral nervous system involvement. We briefly discuss neurologic immune checkpoint inhibitor-related adverse events, which can occasionally present with paraneoplastic neurological syndrome phenotypes.

Sleep Disturbances Associated with Neurological Autoimmunity

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

Clinical Features and Outcomes in Pediatric Autoimmune Encephalitis Associated With CASPR2 Antibody

Background: Contactin-associated protein-like 2 (CASPR2) neurological autoimmunity has been associated with various clinical syndromes involving central and peripheral nervous system. CASPR2 antibody-associated autoimmune encephalitis is mostly reported in adults. Analysis of the clinical presentation and prognostic data of CASPR2 antibody-associated autoimmune encephalitis in children remains important. Methods: A single-center retrospective review of children diagnosed with CASPR2 antibody-associated autoimmune encephalitis from June 1st, 2018 to October 31st, 2020. Results: Six patients were identified. The median age was 12 years (range 1.8-14), with an overall male predominance of 83% (5/6). Commonest clinical features were psychiatric symptoms (6/6), movement disorders (4/6), altered consciousness (3/6), sleep disorders (3/6), and headache (3/6). Four patients (4/6) received first-line therapy alone (steroids combined with intravenous immunoglobulins), and two patients (2/6) received second-line therapy (rituximab, mycophenolate mofetil, or cyclophosphamide). All patients showed no peripheral nervous system involvement. One patient had comorbidities with systemic lupus erythematosus. No evidence of neoplastic disease was found in the whole cohort. All patients had favorable outcomes (modified Rankin Score 0-2) with recurrence rate at 0%, respectively. Conclusion: CASPR2 antibody-associated autoimmune encephalitis is rare in children. Our findings suggest that this type of encephalitis seems to occur more frequently in older children. Patients respond well to immunotherapy and usually demonstrate a favorable clinical outcome. Associated tumors are extremely rare.

Neuropsychiatric Disorders Due to Limbic Encephalitis: Immunologic Aspect

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

Diagnostic Value of Structural and Functional Neuroimaging in Autoimmune Epilepsy

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

Possible coexistence of MOG-IgG-associated disease and anti-Caspr2 antibody-associated autoimmune encephalitis: a first case report

Myelin oligodendrocyte glycoprotein antibody-associated disease has been proposed as a separate inflammatory demyelinating disease of the central nervous system (CNS) since the discovery of pathogenic antibodies against myelin oligodendrocyte glycoprotein (MOG-IgG). Antibodies targeting contactin-associated protein-like 2 (Caspr2), a component of voltage-gated potassium channel (VGKC) complex, have been documented to be associated with a novel autoimmune synaptic encephalitis with a low incidence. Herein, we reported an adult female with initial presentation of decreased vision in the right eye and subsequent episodes of neuropsychiatric disturbance including hypersomnia, agitation, apatheia, and memory impairment. Magnetic resonance imaging (MRI) revealed multiple lesions scattered in brain, brainstem, and cervical and thoracic spinal cord, showing hypointensity on T1-weighted images, hyperintensity on T2-weighted and fluid attenuated inversion recovery (FLAIR) images. Heterogenous patchy or ring-like enhancement was observed in the majority of lesions. The detection of low-titer MOG-IgG exclusively in cerebrospinal fluid (CSF; titer, 1:1) and Caspr2-IgG in both serum and CSF (titers, 1:100 and 1:1) led to a possible diagnosis of coexisting MOG-IgG-associated disease (MOGAD) and anti-Caspr2 antibody-associated autoimmune encephalitis. The patient was treated with immunosuppressive agents including corticosteroids and immunoglobulin, and achieved a sustained remission. To the best of our knowledge, this is the first report on the possible coexistence of MOGAD and anti-Caspr2 antibody-associated autoimmune encephalitis, which advocates for the recommendation of a broad spectrum screening for antibodies against well-defined CNS antigens in suspected patients with autoimmune-mediated diseases of the CNS.

Anti-LGI1, anti-GABABR, and Anti-CASPR2 encephalitides in Asia: A systematic review

AIM

We aim to review the literature to collate and describe features of encephalitides arising from autoantibodies against leucine-rich glioma-inactivated 1 (LGI1), gamma aminobutyric acid receptor (GABABR), and contactin-associated protein-like 2 (CASPR2) in Asian populations and compare them with findings of Western studies.

METHODS

Peer-reviewed articles published till 24 May 2020 were searched, and original, full-text studies from Asia with serum/CSF antibody-based diagnosis and at least 2 patients were selected. Twenty-four studies with 263 patients (139 anti-LGI1, 114 anti-GAGABR, and 10 anti-CASPR2) were included. Data were pooled to produce descriptive information on demographics, clinical characteristics, diagnostics, treatments, and outcome.

RESULTS

The mean age was 54.2 (anti-LGI1), 55.2 (anti-GABABR), and 47.7 years (anti-CASPR2), with an overall male predominance of 62.0%. Commonest clinical features across all types were seizures (87.5%), memory deficits (80.7%), psychiatric disturbances (75.9%), and altered consciousness (52.9%). Four anti-LGI1, 40 anti-GABABR, and 1 anti-CASPR2 patients had tumors. CSF, MRI, and EEG were abnormal in 33.3%, 54.1%, and 75% patients in anti-LGI1; 60.0%, 49.6%, and 85.7% in anti-GABABR; and 50%, 44.4%, and 100% in anti-CASPR2 patients, respectively. 95.6% patients received first-line therapy alone (steroids/IVIG/Plasma therapy), and 4.4% received second-line therapy (rituximab/cyclophosphamide). 91.7%, 63.6%, and 70% of patients had favorable outcomes (modified Rankin Score 0-2) with mortality rates at 2.5%, 23.2%, and 0% in the three types, respectively.

CONCLUSION

Our findings suggest that these disorders present in Asian patients at a relatively young age often with features of seizures, memory deficits, and psychiatric disturbances and usually demonstrate a favorable clinical outcome.

Anti-CASPR2 antibody associated encephalitis with anosmia and demyelinating pseudotumor: A case report

A 20-year-old female presented with fine motor deficits and visual field defect was admitted to our hospital. CSF tests for autoimmune encephalitis antibodies and onconeuronal antibodies were unremarkable. MRI showed unilateral lesion involving left basal ganglia, external capsule, insula, hippocampus, and amygdala, which was considered to be demyelinating pseudotumor after surgical intervention. The patient's symptoms relieved so she didn't consent to immunotherapy. Two years and a half later our patient reported sudden anosmia. Reexamination by MRI demonstrated a new lesion. We then detected anti-CASPR2 antibodies in the patient's serum and gave her immunotherapy.