Immunotherapy-responsive chorea as the presenting feature of LGI1-antibody encephalitis

A case of immunotherapy-responsive autoimmune hemichorea

INTRODUCTION

Subacute adult-acquired hemichorea is a striking presentation with a broad differential, including ischemic, metabolic, and inflammatory causes.

CASE

We encountered a 74-year-old woman with rapid onset of hemichorea and associated encephalopathy. Following a thorough workup without identification of clear imaging or laboratory abnormalities, we empirically treated with IVIg. Her hemichorea dramatically improved. Due to relapses of hemichorea, she required repeat immunotherapy with IVIg or high dose steroids followed by maintenance mycophenolate.

DISCUSSION

This case of seronegative autoimmune hemichorea highlights the importance of a high index of suspicion for an inflammatory etiology of chorea when other causes are ruled out and performing an immunotherapy trial.

Movement disorders in autoimmune encephalitis: an update

Autoimmune encephalitis (AE) is a form of encephalitis resulting from an immune response targeting central nervous system antigens, which is characterized by cognitive impairment, neuropsychiatric symptoms, seizures, movement disorders (MDs), and other encephalopathy symptoms. MDs frequently manifest throughout the progression of the disease, with recurrent involuntary movements leading to discomfort and, in some cases, necessitating admission to the intensive care unit. Prompt identification and management of MDs can aid in the diagnosis and prognosis of AE. This review synthesizes current knowledge on the characteristics, underlying mechanisms, and treatment options for MDs in the context of AE.

Diagnostic Uncertainties: Chorea

Chorea is a hyperkinetic movement disorder with a multitude of potential etiologies, both acquired and inherited. Although the differential diagnosis for new-onset chorea is extensive, there are often clues in the history, exam, and basic testing that can help to narrow the options. Evaluation for treatable or reversible causes should take priority, as rapid diagnosis can lead to more favorable outcomes. While Huntington's disease is most common genetic cause of chorea, multiple phenocopies also exist and should be considered if Huntington gene testing is negative. The decision of what additional genetic testing to pursue should be based on both clinical and epidemiological factors. The following review provides an overview of the many possible etiologies as well as a practical approach for a patient presenting with new-onset chorea.

Prognostic significance and extra-hypothalamus dysfunction of hyponatremia in anti-leucine-rich glioma-inactivated protein 1 encephalitis

This study aimed to investigate prognostic significance and brain metabolic mechanism of hyponatremia in anti-leucine-rich glioma-inactivated protein 1 (LGI1) encephalitis. After adjusting for confounders, patients with moderate and severe hyponatremia had significantly increased risk of poor functional outcome and sequelae of seizures. In addition, serum sodium was negatively correlated with normalized ratio of the standardized uptake value of medial temporal lobe (MTL), basal ganglia (BG), and hypothalamus on positron emission tomography (PET) and which was further validated using voxel-wise analysis, suggesting an extra-hypothalamus (BG and MTL) localization for hyponatremia.

Autoimmune and Paraneoplastic Chorea: A Review of the Literature

Autoimmune chorea syndromes represent a vast array of paraneoplastic, parainfectious and idiopathic disorders. It is increasingly apparent that familiarity with these disorders is critically important, as they may be treatable or may be part of a syndrome requiring further work-up and monitoring. These disorders are mediated by an aberrant immunologic attack with resultant neuronal dysfunction, manifesting as chorea. These conditions are typically accompanied by other neurologic or systemic manifestations. In this review we outline the clinical features, epidemiologic factors, and delineate the specific antibodies associated with each of these autoimmune mediated disorders. We highlight up to date information regarding this heterogeneous group of disorders, including a discussion of parainfectious Sydenham's chorea; paraneoplastic syndromes associated with CRMP-5 (collapsin response mediated protein-5/CV2) and ANNA-1 (antineuronal nuclear antibody / Hu) antibodies, in addition to neuronal antibody-associated disorders including anti-NMDAR, LGI1 (leucine-rich glioma inactivated-1) and CASPR2 (contactin associated protein-2). We discuss the more recently described entities of IgLON5, which has evidence of both immunologic and degenerative pathophysiology, in addition to PDE-10A antibody-associated chorea. We also outline chorea secondary to systemic diseases including Systemic Lupus Erythematosus (SLE) and Primary Antiphospholipid Syndrome (PAPS). We provide a framework for diagnosis and treatment.

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

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

One Side of the Story; Clues to Etiology in Patients with Asymmetric Chorea

Background:

Chorea can be due to a large number of etiologies. Unilateral chorea is classically related to a contralateral structural lesion, e.g. of the putamen or subthalamic nucleus, however, based upon personal impressions, we have observed that systemic disease, in particular metabolic or autoimmune conditions, can also lead to a unilateral or markedly asymmetric presentations. We sought to investigate this impression by reviewing the literature.

Methods:

A PubMed search was conducted using the terms asymmetric” AND “chorea” OR “hemichorea” OR “unilateral” AND “chorea” OR “monochorea” OR “right greater than left” AND “chorea” OR “left greater than right” AND “chorea” OR “right more than left” AND “chorea” OR “left more than right” AND “chorea” as well as “hemiballismus” NOT “stroke” NOT “infarct” NOT “dyskinesia. A total of 243 sources were felt to meet criteria and were reviewed.

Results:

The most common etiology of reported hemi- or asymmetric chorea was diabetic non-ketotic hyperglycemic hemichorea/hemiballismus. Other common diagnoses were Sydenham’s disease, antiphospholipid syndrome and drug-induced chorea. The vast majority of patients with hemi- or asymmetric chorea had acquired rather than genetic, degenerative or congenital causes.

Conclusion:

Despite the potential limitations of our literature review, the evidence presented here supports the observation that the vast majority of asymmetric or unilateral chorea presentations are due to acquired causes, and in this situation an exhaustive search for reversible etiology should be undertaken. However, presentation with symmetric, generalized chorea does not exclude reversible causes, and investigations should address these in addition to genetic and neurodegenerative etiologies.

Autoimmune encephalitis: clinical spectrum and management

Autoimmune encephalitis defines brain inflammation caused by a misdirected immune response against self-antigens expressed in the central nervous system. It comprises a heterogeneous group of disorders that are at least as common as infectious causes of encephalitis. The rapid and ongoing expansion of this field has been driven by the identification of several pathogenic autoantibodies that cause polysymptomatic neurological and neuropsychiatric diseases. These conditions often show highly distinctive cognitive, seizure and movement disorder phenotypes, making them clinically recognisable. Their early identification and treatment improve patient outcomes, and may aid rapid diagnosis of an underlying associated tumour. Here we summarise the well-known autoantibody-mediated encephalitis syndromes with neuronal cell-surface antigens. We focus on practical aspects of their diagnosis and treatment, offer our clinical experiences of managing such cases and highlight more basic neuroimmunological advances that will inform their future diagnosis and treatments.

Paraneoplastic and autoimmune encephalitis: Alterations of mood and emotion

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

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

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

Clinical and Genetic Overview of Paroxysmal Movement Disorders and Episodic Ataxias

Paroxysmal movement disorders (PMDs) are rare neurological diseases typically manifesting with intermittent attacks of abnormal involuntary movements. Two main categories of PMDs are recognized based on the phenomenology: Paroxysmal dyskinesias (PxDs) are characterized by transient episodes hyperkinetic movement disorders, while attacks of cerebellar dysfunction are the hallmark of episodic ataxias (EAs). From an etiological point of view, both primary (genetic) and secondary (acquired) causes of PMDs are known. Recognition and diagnosis of PMDs is based on personal and familial medical history, physical examination, detailed reconstruction of ictal phenomenology, neuroimaging, and genetic analysis. Neurophysiological or laboratory tests are reserved for selected cases. Genetic knowledge of PMDs has been largely incremented by the advent of next generation sequencing (NGS) methodologies. The wide number of genes involved in the pathogenesis of PMDs reflects a high complexity of molecular bases of neurotransmission in cerebellar and basal ganglia circuits. In consideration of the broad genetic and phenotypic heterogeneity, a NGS approach by targeted panel for movement disorders, clinical or whole exome sequencing should be preferred, whenever possible, to a single gene approach, in order to increase diagnostic rate. This review is focused on clinical and genetic features of PMDs with the aim to (1) help clinicians to recognize, diagnose and treat patients with PMDs as well as to (2) provide an overview of genes and molecular mechanisms underlying these intriguing neurogenetic disorders.

Antibody-related movement disorders - a comprehensive review of phenotype-autoantibody correlations and a guide to testing

Background

Over the past decade increasing scientific progress in the field of autoantibody-mediated neurological diseases was achieved. Movement disorders are a frequent and often prominent feature in such diseases which are potentially treatable.

Main body

Antibody-mediated movement disorders encompass a large clinical spectrum of diverse neurologic disorders occurring either in isolation or accompanying more complex autoimmune encephalopathic diseases. Since autoimmune movement disorders can easily be misdiagnosed as neurodegenerative or metabolic conditions, appropriate immunotherapy can be delayed or even missed. Recognition of typical clinical patterns is important to reach the correct diagnosis.

Conclusion

There is a growing number of newly discovered antibodies which can cause movement disorders. Several antibodies can cause distinctive phenotypes of movement disorders which are important to be aware of. Early diagnosis is important because immunotherapy can result in major improvement.In this review article we summarize the current knowledge of autoimmune movement disorders from a point of view focused on clinical syndromes. We discuss associated clinical phenomenology and antineuronal antibodies together with alternative etiologies with the aim of providing a diagnostic framework for clinicians considering underlying autoimmunity in patients with movement disorders.

The exploration of the spectrum of motor manifestations of anti-LGI1 encephalitis beyond FBDS

PURPOSE

The purpose of this study was to characterize the spectrum of motor events in patients with acute anti-leucine-rich glioma-inactivated protein 1 (anti-LGI1) encephalitis through video-electroencephalogram (VEEG) recordings.

METHOD

We collected data retrospectively from 16 patients diagnosed with anti-LGI1 encephalitis who had completed VEEG recording during hospitalization.

RESULTS

VEEG monitoring lasted a median of 11.0 h (range 4.5∼20). Fourteen types of seizures were recorded in 9 patients (56.3 %). Eight of the 14 types of seizures demonstrated typical ictal EEG evolution (including 2 subclinical seizures), 3/14 demonstrated EEG electrodecremental events (EDE) at onset but without further evolution, and 3/14 could be only judged by analyzing semiology. FBDS was recorded in 6 patients (37.5 %), and all these attacks were followed by epileptic seizures. Simple hyperkinetic movements (HMs), such as jerk-like or twisting movements, were found in 8 (50 %) patients, and 6 of them had complex HMs, such as manipulating movements or mimics of daily activities, during sleep.

CONCLUSIONS

1. Atypical seizures, for instance, seizures without EEG evolution, are not rare but likely to be overlooked. 2. FBDS is closely linked with epileptic seizures, revealing FBDS to be a part of epileptic attacks. 3. HMs could expand the spectrum of motor manifestations, overlapping with sleep disorders. 4. The high prevalence of these motor events might be due to the disrupted cortical-subcortical network, which is critical in motor control and sleep.

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

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

Diagnosing autoimmune encephalitis based on clinical features and autoantibody findings

INTRODUCTION

Autoimmune encephalitides have been accepted as a reproducible and treatable new group of diseases. At present, there is concern that such diagnoses might be made too liberally. Areas covered: This article suggests how to make valid diagnoses. They should consist of three elements: the clinical syndrome, the associated antibody and the presumed cause or predisposition. Recently, an international consortium published formal clinical criteria for autoimmune encephalitides to enable diagnoses even if antibody testing is not (immediately) available and to prevent overinterpretation of questionable antibody results. Antibody testing has greatly benefitted from the introduction of cell-based assays for the demonstration of antibodies against surface antigens. Paraneoplastic or post-infectious situations, side effects of tumor therapies or genetic predispositions help to explain why a patient develops autoimmune encephalitis. Expert opinion: With the application of this three-fold diagnostic system, clinicians can counsel patients regarding therapy and prognosis, while researchers can form meaningful patient cohorts. An operationalization of criteria would be advantageous.

Admission diagnoses of patients later diagnosed with autoimmune encephalitis

BACKGROUND

Since the detection of autoantibodies against neuronal surface antigens, autoimmune encephalitis (AE) has been more frequently diagnosed, especially in patients with symptoms typical of limbic encephalitis, such as seizures, short-term memory deficits, or psychosis. However, the clinical spectrum of AE may be much wider, making correct clinical diagnosis difficult.

METHODS

We retrospectively analysed symptoms and admission diagnoses at first clinical presentation in 50 AE patients. We included patients with a clinical diagnosis of AE for whom a FDG-PET imaging was available. Final diagnoses were re-evaluated by a blinded investigator according to the most recent consensus suggestions published in 2016 for AE diagnostic criteria. We additionally describe two patients with Morvan syndrome who showed CASPR2 antibodies.

RESULTS

In 40 patients (80.0%), the clinical presentation at first admission was typical for AE. Ten patients (20.0%) initially suffered from atypical symptoms; among these patients, isolated headache and cerebellar dysfunction were most frequent (three patients each). However, an initial diagnosis of suspected encephalitis was only reached in 16 patients (32.0%), nine (18.0) of which were suspected to have infectious encephalitis, and seven (14.0%) patients were suspected to have AE. In 34 patients (68.0%), a diagnosis other than encephalitis was considered, (e.g., epilepsy, psychiatric diseases, transient ischemic attack, dementia, meningitis, and cerebellitis).

CONCLUSIONS

These data show the broad spectrum of initial symptoms of AE; the correct initial diagnosis of AE is often missed or delayed. Hence, clinicians in neurological and psychiatric hospitals should consider AE in the differential diagnosis of cases with atypical clinical presentations.

The clinical features, underlying immunology, and treatment of autoantibody-mediated movement disorders

An increasing number of movement disorders are associated with autoantibodies. Many of these autoantibodies target the extracellular domain of neuronal surface proteins and associate with highly specific phenotypes, suggesting they have pathogenic potential. Below, we describe the phenotypes associated with some of these commoner autoantibody‐mediated movement disorders, and outline increasingly well‐established mechanisms of autoantibody pathogenicity which include antigen downregulation and complement fixation. Despite these advances, and the increasingly robust evidence for improved clinical outcomes with early escalation of immunotherapies, the underlying cellular immunology of these conditions has received little attention. Therefore, here, we outline the likely roles of T cells and B cells in the generation of autoantibodies, and reflect on how these may guide both current immunotherapy regimes and our future understanding of precision medicine in the field. In addition, we summarise potential mechanisms by which these peripherally‐driven immune responses may reach the central nervous system. We integrate this with the immunologically‐relevant clinical observations of preceding infections, tumours and human leucocyte antigen‐associations to provide an overview of the therapeutically‐relevant underlying adaptive immunology in the autoantibody‐mediated movement disorders. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Movement disorders with neuronal antibodies: syndromic approach, genetic parallels and pathophysiology

Movement disorders are a prominent and common feature in many autoantibody-associated neurological diseases, a group of potentially treatable conditions that can mimic infectious, metabolic or neurodegenerative disease. Certain movement disorders are likely to associate with certain autoantibodies; for example, the characteristic dyskinesias, chorea and dystonia associated with NMDAR antibodies, stiff person spectrum disorders with GAD, glycine receptor, amphiphysin or DPPX antibodies, specific paroxysmal dystonias with LGI1 antibodies, and cerebellar ataxia with various anti-neuronal antibodies. There are also less-recognized movement disorder presentations of antibody-related disease, and a considerable overlap between the clinical phenotypes and the associated antibody spectra. In this review, we first describe the antibodies associated with each syndrome, highlight distinctive clinical or radiological 'red flags', and suggest a syndromic approach based on the predominant movement disorder presentation, age, and associated features. We then examine the underlying immunopathophysiology, which may guide treatment decisions in these neuroimmunological disorders, and highlight the exceptional interface between neuronal antibodies and neurodegeneration, such as the tauopathy associated with IgLON5 antibodies. Moreover, we elaborate the emerging pathophysiological parallels between genetic movement disorders and immunological conditions, with proteins being either affected by mutations or targeted by autoantibodies. Hereditary hyperekplexia, for example, is caused by mutations of the alpha subunit of the glycine receptor leading to an infantile-onset disorder with exaggerated startle and stiffness, whereas antibodies targeting glycine receptors can induce acquired hyperekplexia. The spectrum of such immunological and genetic analogies also includes cerebellar ataxias and some encephalopathies. Lastly, we discuss how these pathophysiological considerations could reflect on possible future directions regarding antigen-specific immunotherapies or targeting the pathophysiological cascades downstream of the antibody effects.

Autoantibody-Associated Movement Disorders in Children: Proven and Proposed

Movement disorders secondary to autoantibodies in children represent a rapidly expanding group of conditions. Once considered to be limited to poststreptococcal Sydenham's chorea or rare cases of childhood systemic lupus erythematosus, a variety of antibody-related movement abnormalities are now seen as part of noninfectious autoimmune encephalitis or within an expanding list of postinfectious disorders. In this article, several proposed autoantibody-mediated movement disorders in children are reviewed. In each one, there is a hypothesized antibody biomarker that is believed to be pathogenic and cause the clinical symptoms. As will be discussed, in some, such as anti-NMDA receptor encephalitis, the strength of supporting evidence is strong. In others, antibodies have been identified, but their role as the pathophysiological mechanism remains undetermined. Lastly, there are proposed disorders, such as PANDAS, that are controversial on both a clinical and autoimmune basis.

Faciobrachial dystonic seizures result from fronto-temporo-basalganglial network involvement

•Faciobrachial dystonic seizures (FBDS) are caused by autoantibodies to leucine-rich glioma-inactivated1 proteins, a component of the voltage-gated potassium channel complex (VGKC-complex) and precede the clinical presentation of limbic encephalitis.•The exact pathophysiology of FBDS is not known and whether they are seizures or movement disorder is still debated.•We suggest the fronto-temporo-basal ganglia network involving the medial frontal and temporal regions along with the corpus striatum and substantia nigra being responsible for the clinical phenomenon of FBDS.•The varied clinical, electrical and imaging features of FBDS in our cases and in the literature are best explained by involvement of this network.•Entrainment from any part of this network will result in similar clinical expression of FBDS, whereas other electro-clinical associations and duration depends on the extent of involvement of the network.

Confusion, Faciobrachial Dystonic Seizures, and Critical Hyponatremia in a Patient with Voltage-Gated Potassium Channel Encephalitis

Autoimmune limbic encephalitis is a rare cause of encephalitic disease. It is associated with various target antigens and is difficult to diagnose, and experience with its treatment is limited. This case report describes a 69-year-old man, who presented with life-threatening hyponatremia and confusion, following several months of gradually worsening faciobrachial dystonic seizures. Faciobrachial dystonic seizures are a well-described feature classically observed in voltage-gated potassium channel autoimmune encephalitis. The presence of chronic hyponatremia without cognitive dysfunction, eventually culminating in an acute episode of encephalopathy and severe hyponatremia, is a pattern of natural history not previously documented in this condition.

Voltage-gated potassium channel-complex autoimmunity and associated clinical syndromes

Voltage-gated potassium channel (VGKC)-complex antibodies are defined by the radioimmunoprecipitation of Kv1 potassium channel subunits from brain tissue extracts and were initially discovered in patients with peripheral nerve hyperexcitability (PNH). Subsequently, they were found in patients with PNH plus psychosis, insomnia, and dysautonomia, collectively termed Morvan's syndrome (MoS), and in a limbic encephalopathy (LE) with prominent amnesia and frequent seizures. Most recently, they have been described in patients with pure epilepsies, especially in patients with the novel and distinctive semiology termed faciobrachial dystonic seizures (FBDS). In each of these conditions, there is a close correlation between clinical measures and antibody levels. The VGKC-complex is a group of proteins that are strongly associated in situ and after extraction in mild detergent. Two major targets of the autoantibodies are leucine-rich glioma-inactivated 1 (LGI1) and contactin-associated protein 2 (CASPR2). The patients with PNH or MoS are most likely to have CASPR2 antibodies, whereas LGI1 antibodies are found characteristically in patients with FBDS and LE. Crucially, each of these conditions has a good response to immunotherapies, often corticosteroids and plasma exchange, although optimal regimes require further study. VGKC-complex antibodies have also been described in neuropathic pain syndromes, chronic epilepsies, a polyradiculopathy in porcine abattoir workers, and some children with status epilepticus. Increasingly, however, the antigenic targets in these patients are not defined and in some cases the antibodies may be secondary rather than the primary cause. Future serologic studies should define all the antigenic components of the VGKC-complex, and further inform mechanisms of antibody pathogenicity and related inflammation.

Stiff person syndrome and other immune-mediated movement disorders - new insights

PURPOSE OF REVIEW

This review highlights the recent developments in immune-mediated movement disorders and how they reflect on clinical practice and our understanding of the underlying pathophysiological mechanisms.

RECENT FINDINGS

The antibody spectrum associated with stiff person syndrome and related disorders (SPSD) has broadened and, apart from the classic glutamic acid decarboxylase (GAD)- and amphiphysin-antibodies, includes now also antibodies against dipeptidyl-peptidase-like protein-6 (DPPX), gamma-aminobutyric acid type A receptor (GABAAR), glycine receptor (GlyR) and glycine transporter 2 (GlyT2). The field of movement disorders with neuronal antibodies keeps expanding with the discovery for example of antibodies against leucine rich glioma inactivated protein 1 (LGI1) and contactin associated protein 2 (Caspr2) in chorea, or antibodies targeting ARHGAP26- or Na/K ATPase alpha 3 subunit (ATP1A3) in cerebellar ataxia. Moreover, neuronal antibodies may partly account for movement disorders attributed for example to Sydenham's chorea, coeliac disease, or steroid responsive encephalopathy with thyroid antibodies. Lastly, there is an interface of immunology, genetics and neurodegeneration, e.g. in Aicardi-Goutières syndrome or the tauopathy with IgLON5-antibodies.

SUMMARY

Clinicians should be aware of new antibodies such as dipeptidyl-peptidase-like protein-6, gamma-aminobutyric acid type A receptor and glycine transporter 2 in stiff person syndrome and related disorders, as well as of the expanding spectrum of immune-mediated movement disorders.

Huntington's Disease, Huntington's Disease Look-Alikes‎, and Benign Hereditary Chorea: What's New?

Background

The differential diagnosis of chorea syndromes is complex. It includes inherited forms, the most common of which is autosomal dominant Huntington's disease (HD). In addition, there are disorders mimicking HD, the so-called HD-like (HDL) syndromes.

Methods and Results

Here we review main clinical, genetic, and pathophysiological characteristics of HD and the rare HD phenocopies in order to familiarize clinicians with them. Molecular studies have shown that HD phenocopies account for about 1% of suspected HD cases, most commonly due to mutations in C9orf72 (also the main cause of frontotemporal dementia and amyotrophic lateral sclerosis syndromes), TATA box-binding protein (spinocerebellar ataxia type 17 [SCA17]/HDL4), and JPH3 (HDL2). Systematic screening studies also revealed mutations in PRNP (prion disease), VPS13A (chorea-acanthocytosis), ATXN8OS-ATXN8 (SCA8), and FXN (late-onset Friedreich's Ataxia) in single cases. Further differential diagnoses to consider in patients presenting with a clinical diagnosis consistent with HD, but without the HD expansion, include dentatorubral-pallidoluysian atrophy and benign hereditary chorea (TITF1), as well as the recently described form of ADCY5-associated neurodegeneration. Lastly, biallelic mutations in RNF216 and FRRS1L have recently been reported as autosomal recessive phenocopies of HD.

Conclusion

There is a growing list of genes associated with chorea, yet a substantial percentage of patients remain undiagnosed. It is likely that more genes will be discovered in the future and that the clinical spectrum of the described disorders will broaden.

Autoimmune movement disorders

Autoimmune movement disorders encapsulate a large and diverse group of neurologic disorders occurring either in isolation or accompanying more diffuse autoimmune encephalitic illnesses. The full range of movement phenomena has been described and, as they often occur in adults, many of the presentations can mimic neurodegenerative disorders, such as Huntington disease. Disorders may be ataxic, hypokinetic (parkinsonism), or hyperkinetic (myoclonus, chorea, tics, and other dyskinetic disorders). The autoantibody targets are diverse and include neuronal surface proteins such as leucine-rich, glioma-inactivated 1 (LGI1) and glycine receptors, as well as antibodies (such as intracellular antigens) that are markers of a central nervous system process mediated by CD8+ cytotoxic T cells. However, there are two conditions, stiff-person syndrome (also known as stiff-man syndrome) and progressive encephalomyelitis with rigidity and myoclonus (PERM), that are always autoimmune movement disorders. In some instances (such as Purkinje cell cytoplasmic antibody-1 (PCA-1) autoimmunity), antibodies detected in serum and cerebrospinal fluid can be indicative of a paraneoplastic cause, and may direct the cancer search. In other instances (such as 65kDa isoform of glutamic acid decarboxylase (GAD65) autoimmunity), a paraneoplastic cause is very unlikely, and early treatment with immunotherapy may promote improvement or recovery. Here we describe the different types of movement disorder and the clinical features and antibodies associated with them, and discuss treatment.

[Unexplicated neuropsychiatric disorders: Do not ignore dysimmune encephalitis. A case report of a dysimmune encephalitis with anti-leucine rich glioma inactivated 1 (LGI-1) antibodies]

INTRODUCTION

Anti-leucine rich glioma inactivated 1 encephalitis is a common and a treatable etiology of autoimmune encephalitis. Its diagnosis is a challenge because the initial diagnostic work-up is often normal.

CASE REPORT

A 48-year-old man experienced cognitive and behavioral troubles, facio-brachial dystonic seizures and a syndrome of inappropriate antidiuretic hormone secretion. First line tests excluded infectious, neoplastic, systemic inflammatory, endrocrine or toxic etiologies. Cerebral (18)Fluoro-desoxy-glucose (FDG) position emission tomography and research of specific antibodies in cerebro-spinal fluid and serum led to diagnose an anti-leucine rich glioma inactivated 1 encephalitis. Intravenous immunoglobulins and corticosteroids were partially effective. Cyclophosphamid permitted a good recovery.

CONCLUSION

In the presence of acute neuropsychiatric disorders with a negative etiologic research, physician should think about dysimmune encephalitis. Facio-brachial dystonic seizures and syndrome of inappropriate antidiuretic hormone secretion are highly evocative of anti-leucine rich glioma inactivated 1 encephalitis. The diagnosis needs specific diagnostic tests (cerebral (18)FDG position emission tomography and antibodies research in cerebro-spinal fluid and in serum), after the exclusion of alternative diagnoses. Extensive and repeated diagnostic work-up for neoplasia is required. Immunosupressive therapies are effective in most cases.

Encephalitis due to antibodies to voltage gated potassium channel (VGKC) with cerebellar involvement in a teenager

Encephalitis due to antibodies to voltage gated potassium channel (VGKC) typically presents with limbic encephalitis and medial temporal lobe involvement on neuroimaging. We describe a case of 13 year girl female with encephalitis due to antibodies to VGKC with signal changes in the cerebellar dentate nuclei bilaterally and clinical features that suggested predominant cerebellar involvement. These have never been reported previously in the literature. Our case expands the phenotypic spectrum of this rare condition.

Cell-surface central nervous system autoantibodies: clinical relevance and emerging paradigms

The recent discovery of several potentially pathogenic autoantibodies has helped identify patients with clinically distinctive central nervous system diseases that appear to benefit from immunotherapy. The associated autoantibodies are directed against the extracellular domains of cell-surface-expressed neuronal or glial proteins such as LGI1, N-methyl-D-aspartate receptor, and aquaporin-4. The original descriptions of the associated clinical syndromes were phenotypically well circumscribed. However, as availability of antibody testing has increased, the range of associated patient phenotypes and demographics has expanded. This in turn has led to the recognition of more immunotherapy-responsive syndromes in patients presenting with cognitive and behavioral problems, seizures, movement disorders, psychiatric features, and demyelinating disease. Although antibody detection remains diagnostically important, clinical recognition of these distinctive syndromes should ensure early and appropriate immunotherapy administration. We review the emerging paradigm of cell-surface-directed antibody-mediated neurological diseases, describe how the associated disease spectrums have broadened since the original descriptions, discuss some of the methodological issues regarding techniques for antibody detection and emphasize considerations surrounding immunotherapy administration. As these disorders continue to reach mainstream neurology and even psychiatry, more cell-surface-directed antibodies will be discovered, and their possible relevance to other more common disease presentations should become more clearly defined.

More than memory impairment in voltage-gated potassium channel complex encephalopathy

BACKGROUND AND PURPOSE

Autoimmune encephalopathies (AEs) are a heterogeneous group of neurological disorders that affect cognition. Although memory difficulties are commonly endorsed, few reports of AEs inclusively assess all cognitive domains in detail. Our aim was to perform an unbiased cognitive evaluation of AE patients with voltage-gated potassium channel complex antibodies (VGKCC -Abs) in order to delineate cognitive strengths and weaknesses.

METHODS

Serial VGKCC -Ab AE subjects (n = 12) were assessed with a comprehensive evaluation of memory, executive functions, visuospatial skills and language. Clinical magnetic resonance imaging (MRI) (n = 10/12) was evaluated. Five subjects had serial cognitive testing available, permitting descriptive analysis of change.

RESULTS

Subjects demonstrated mild to moderate impairment in memory (mean Z = -1.9) and executive functions (mean Z = -1.5), with variable impairments in language and sparing of visuospatial skills. MRI findings showed T2 hyperintensities in medial temporal lobe (10/10) and basal ganglia (2/10). Serial cognitive examination revealed heterogeneity in cognitive function; whereas most patients improved in one or more domains, residual impairments were observed in some patients.

CONCLUSIONS

This study augments previous neuropsychological analyses in VGKCC -Ab AE by identifying not only memory and executive function deficits but also language impairments, with preservation of visuospatial functioning. The study further highlights the importance of domain-specific testing to parse out the complex cognitive phenotypes of VGKCC -Ab AE.

Hemichorea Associated with CASPR2 Antibody

This letter was written in response to: Ramdhani RA, Frucht SJ. Isolated chorea associated with LGI1 antibody. Tremor Other Hyperkinet Mov. 2014; 4. doi: 10.7916/D8MG7MFC.

Molecular and cellular mechanisms underlying anti-neuronal antibody mediated disorders of the central nervous system

Over the last decade multiple autoantigens located on the plasma membrane of neurons have been identified. Neuronal surface antigens include molecules directly involved in neurotransmission and excitability. Binding of the antibody to the antigen may directly alter the target protein's function, resulting in neurological disorders. The often striking reversibility of symptoms following early aggressive immunotherapy supports a pathogenic role for autoantibodies to neuronal surface antigens. In order to better understand and treat these neurologic disorders it is important to gain insight in the underlying mechanisms of antibody pathogenicity. In this review we discuss the clinical, circumstantial, in vitro and in vivo evidence for neuronal surface antibody pathogenicity and the possible underlying cellular and molecular mechanisms. This review shows that antibodies to neuronal surface antigens are often directed at conformational epitopes located in the extracellular domain of the antigen. The conformation of the epitope can be affected by specific posttranslational modifications. This may explain the distinct clinical phenotypes that are seen in patients with antibodies to antigens that are expressed throughout the brain. Furthermore, it is likely that there is a heterogeneous antibody population, consisting of different IgG subtypes and directed at multiple epitopes located in an immunogenic region. Binding of these antibodies may result in different pathophysiological mechanisms occurring in the same patient, together contributing to the clinical syndrome. Unraveling the predominant mechanism in each distinct antigen could provide clues for therapeutic interventions.

N-methyl-D-aspartate receptor antibody-associated movement disorder without encephalopathy

N-methyl-D-aspartate receptor (NMDAR) antibody encephalitis is a well-recognized clinico-immunological syndrome that presents with a movement disorder, cognitive decline, psychiatric symptoms, and epileptic seizures. A pure monosymptomatic presentation is rare; however, some patients present predominantly with a movement disorder in the absence of encephalopathy. Here, we describe three paediatric patients with an NMDAR antibody-mediated movement disorder: a 5-year-old female with acute onset hemichorea, a 10-year-old female with generalized chorea, and a 12-year-old male with abdominal myoclonus. These patients did not develop the characteristic encephalopathy syndrome seen in NMDAR encephalitis, but all three had other associated subtle cognitive deficits. The patients demonstrated good responses to immunotherapy.

Isolated Chorea Associated with LGI1 Antibody

Background

Leucine-rich glioma inactivated 1 (LGI1) antibody produces a syndrome of limbic encephalitis, hyponatremia, and facio-brachial dystonic seizures that is non-paraneoplastic and responsive to corticosteroids. Parkinsonism, tremor, and generalized chorea are rare manifestations of LGI1, but, when present, commonly accompany other signs of limbic encephalitis.

Case Report

We present a case of LGI1-related isolated chorea in a 53-year-old Japanese male. His chorea responded to high-dose steroids, suggesting a potential role for this synaptic antibody in triggering chorea.

Discussion

This case highlights a new treatable etiology of chorea.

Autoimmune encephalitis: recent updates and emerging challenges

The knowledge of immune dysregulation and autoimmunity in neurological disorders has expanded considerably in recent times. Recognition of clinical syndromes, reliable methods of diagnosis, and early targeted immunotherapy can lead to a favourable outcome in acute and subacute neurological disorders that may be associated with significant morbidity and mortality if left untreated. This review focuses on the rapidly expanding field of autoimmune encephalitis. We describe the differences between limbic encephalitis associated with antibodies targeting intracellular antigens, and neuronal surface antibody syndromes (NSAS) where the antigens are primarily receptors or synaptic proteins located on the neuronal cell surface. We chronologically highlight important developments in NSAS by focusing on voltage gated potassium channel complex-associated antibody mediated encephalitis, anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis, and anti-dopamine 2 receptor antibody-associated basal ganglia encephalitis. Contentious issues such as the complexities of using serum antibodies as biomarkers, the initiation of central nervous system autoimmunity, and possible pathogenic mechanisms of these antibodies will be reviewed. The therapeutic challenges that clinicians face such as the timing of therapy and the role of second-line therapy will be discussed, with crucial concepts highlighted in the form of clinical vignettes. Future directions will involve the identification of novel antigens and methods to establish their pathogenicity, as well as evaluation of the most efficacious therapeutic strategies in patients with established NSAS.

Neuroinflammation and psychiatric illness

Multiple lines of evidence support the pathogenic role of neuroinflammation in psychiatric illness. While systemic autoimmune diseases are well-documented causes of neuropsychiatric disorders, synaptic autoimmune encephalitides with psychotic symptoms often go under-recognized. Parallel to the link between psychiatric symptoms and autoimmunity in autoimmune diseases, neuroimmunological abnormalities occur in classical psychiatric disorders (for example, major depressive, bipolar, schizophrenia, and obsessive-compulsive disorders). Investigations into the pathophysiology of these conditions traditionally stressed dysregulation of the glutamatergic and monoaminergic systems, but the mechanisms causing these neurotransmitter abnormalities remained elusive. We review the link between autoimmunity and neuropsychiatric disorders, and the human and experimental evidence supporting the pathogenic role of neuroinflammation in selected classical psychiatric disorders. Understanding how psychosocial, genetic, immunological and neurotransmitter systems interact can reveal pathogenic clues and help target new preventive and symptomatic therapies.

Autoimmune chorea in adults

OBJECTIVES

To determine the characteristics of adult-onset autoimmune chorea, and compare paraneoplastic and idiopathic subgroups.

METHODS

Thirty-six adults with autoimmune chorea were identified at Mayo Clinic (Rochester, MN) from 1997 to 2012. Medical record and laboratory data were recorded. Nonparaneoplastic (n = 22) and paraneoplastic cases (n = 14) were compared.

RESULTS

Women accounted for 21 patients (58%). Median age at symptom onset was 67 years (range 18-87 years). We estimated the incidence for Olmsted County was 1.5 per million person-years. Symptom onset was subacute in all. Chorea was focal (20 patients) or generalized (16 patients). Although chorea predominated, other neurologic disorders frequently coexisted (29 patients); abnormal eye movements were uncommon (4 patients). No patient had NMDA receptor antibody or any immunoglobulin (Ig)G yielding a detectable immunofluorescence binding pattern restricted to basal ganglia. Two had synaptic IgG antibodies novel to the context of chorea (GAD65, 1; CASPR2, 1). In the paraneoplastic group, 14 patients had evidence of cancer. Of 13 with a histopathologically confirmed neoplasm, small-cell carcinoma and adenocarcinoma were most common; 6 patients had a cancer-predictive paraneoplastic autoantibody, with CRMP-5-IgG and ANNA-1 being most common. In the idiopathic group, 19 of the 22 patients had a coexisting autoimmune disorder (most frequently systemic lupus erythematosus and antiphospholipid syndrome); autoantibodies were detected in 21 patients, most frequently lupus and phospholipid specificities (19 patients). The paraneoplastic group was older (p = 0.001), more frequently male (p = 0.006), had more frequent weight loss (p = 0.02), and frequently had peripheral neuropathy (p = 0.008).

CONCLUSIONS

Autoimmune chorea is a rare disorder with rapid onset. Male sex, older age, severe chorea, coexisting peripheral neuropathy, and weight loss increase the likelihood of cancer.