Reversible paraneoplastic limbic encephalitis associated with antibodies to the AMPA receptor

Glutamatergic autoencephalitides: an emerging field

Autoimmune responses targeting synaptic proteins are associated with a wide range of neurologic symptoms. Among these disorders are those associated with antibodies to ionotropic glutamate receptors, including the NMDAR (N-methyl-D-aspartate receptor) and AMPAR (α-amino-3-hydrozy-5-methyl-4-isoxazolepropionic acid receptor). Patients with anti-NMDAR encephalitis present with psychiatric symptoms, seizures, movement disorders, impaired consciousness, and autonomic derangements; half of patients have an associated ovarian teratoma, and most patients respond to immunosuppressive therapies. Patients' antibodies bind to the amino terminal domain of the NMDAR, and result in loss of NMDARs from synapses with subsequent NMDAR hypofunction. Anti-NMDAR antibodies have now been reported in other neuropsychiatric conditions, including psychosis, dementia, and HSV encephalitis. The pathophysiologic relevance of anti-NMDAR antibodies in these disorders is not yet clear, but their presence may indicate a role for immunotherapy in some patients. Although considerable work remains to be done, our understanding of disorders associated with anti-glutamate receptor antibodies has grown exponentially since they were first described just over 7 years ago, revolutionizing neurology. These antibodies, by interfering with synaptic function, readily link basic science and clinical medicine, and have revealed the impact of sudden but sustained loss of specific neurotransmitter receptors in humans. Improved understanding of their pathophysiology will lead to better treatments for these diseases while providing novel insights regarding the roles of glutamate receptors in learning, memory, and neuropsychiatric disease.

Paraneoplastic disorders of the central and peripheral nervous systems

Paraneoplatic neurologic syndromes (PNS) have been seminally defined as acute or subacute neurological syndromes resulting from nervous system dysfunction that is remote from the site of a malignant neoplasm or its metastases. However, in respect to our current understanding of their pathogenesis we may redefine these disorders as cancer-related dysimmune neurologic syndromes. We first deal with the epidemiology and the pathogenesis of PNS, then the different classic PNS are reviewed with clinical features according to the associated onconeuronal antibodies. Finally, therapeutic approaches are discussed.

Rapid progression and brain atrophy in anti-AMPA receptor encephalitis

Anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor encephalitis is an anti-neuronal surface antigen autoimmune encephalitis that is rarely reported. Our study evaluated the first known patient who developed anti-AMPA receptor encephalitis during pregnancy. Initial brain MRI revealed bilateral limbic encephalitis. However, rapid brain atrophy on MRI with extensive hypometabolism of cerebral cortices, caudate nuclei and brain stem hypoperfusion on (18)F-FDG PET developed when clinically progressed. IgG index of serial CSF studies reflected the clinical improvements after plasmapheresis and plasma exchange. The clinical spectrum of anti-AMPA receptor encephalitis may be expanded from limited limbic involvement to extended central nervous system.

Paraneoplastic neurological syndromes: general treatment overview

OPINION STATEMENT

Major recent discoveries have bringing out a revised definition of paraneoplastic neurological syndromes (PNS), bringing out the concept of antibody-mediated neurological disorders, triggered or not by cancer. Classification of these diseases is not based anymore on the clinical pattern or an underlying tumor, but on the location of the targeted antigens. Indeed, evolution, response to treatment, and pathophysiology are radically different according to the associated antibodies. In some patients with newly described antibodies targeting cell-surface antigens, humoral immunity seems to play a direct role and a dramatic improvement is observed with immunomodulator treatments. In these patients, an associated tumor is less frequent. Conversely, patients with antibodies directed against intracellular targets are, in most cases, characterized by a high degree of irreversible neuronal death mediated by cytotoxic T-cells and do not improve after immunomodulator treatments. In these patients, an associated tumor is highly frequent and must be cured as soon as possible. A third group of patients can be identified with anti-GAD65 and anti-Amphiphysin antibodies. In patients with these antibodies, the efficiency of immunomodulator treatments is less clear as well as the type of immune response that could be a mix between humoral and cellular. In this last group, the antigen is intracellular, but patients may improve with immunomodulator treatments and associated tumors are rare. Thus, identification of associated antibodies should be prompt and the treatment guided according the identified antibody. Mainstream of treatment include the quest of a tumor and its cure. Immunotherapy must be promptly initiated, targeting humoral, or cellular immune response, or both, according to the associated antibodies. Furthermore, in some situations such as Lambert-Eaton Myasthenic Syndromes and Stiff-Person Syndromes, symptomatic drugs can be useful to control the symptoms.

Autoimmune Encephalitis

The term autoimmune encephalitis is used to describe a group of disorders characterised by symptoms of limbic and extra-limbic dysfunction occurring in association with antibodies against synaptic antigens and proteins localised on the neuronal cell surface. In recent years there has been a rapidly expanding knowledge of these syndromes resulting in a shift in clinical paradigms and new insights into pathogenic mechanisms. Since many patients respond well to immunosuppressive treatment, the recognition of these disorders is of utmost importance. In general, there are no brain-imaging modalities or biomarkers specific of these disorders other than the demonstration of the neuronal antibodies. A disease classification based on these antibodies provides information on prognosis and paraneoplastic aetiology. This article focuses on recent clinical advances, newly characterised antibodies and treatment approaches to these disorders.

Neuronal autoantigens--pathogenesis, associated disorders and antibody testing

The discovery of disorders that are associated with antibodies to neuronal cell-surface proteins has led to a paradigm shift in our understanding of CNS autoimmunity. These disorders can occur in patients with or without cancer-often children or young adults who develop psychosis, catatonic or autistic features, memory problems, abnormal movements, or seizures that were previously considered idiopathic. The autoantigens in such cases have crucial roles in synaptic transmission, plasticity and peripheral nerve excitability. Patients can be comatose or encephalopathic for months and yet fully recover with supportive care and immunotherapy. By contrast, disorders in which the antibodies target intracellular antigens, and in which T-cell-mediated irreversible neuronal degeneration occurs, show a considerably poorer response to treatment. In this article, we review the various targets of neuronal antibodies, focusing predominantly on autoantigens located on the cell surface or synapses-namely, N-methyl-D-aspartate receptors, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors, γ-aminobutyric acid receptors, leucine-rich glioma-inactivated protein 1, contactin-associated protein-like 2, and metabotropic glutamate receptors. We also provide an algorithm to identify and assess antibodies that bind to cell-surface and synaptic antigens.

Neurological manifestation of colonic adenocarcinoma

Paraneoplastic neurologic disorders are extremely rare in cancer patients and are most commonly associated with certain tumors, such as ovarian cancer, small cell lung cancer, and breast cancer. We report here a paraneoplastic neurological syndrome in a 53-year-old man with colonic adenocarcinoma with a solitary liver metastasis. His paraneoplastic syndrome was successfully treated by methylprednisolone and primary oncologic therapies including neoadjuvant chemotherapy and definitive surgery. This is also the first documented case of simultaneous manifestation of a sensory neuropathy and limbic encephalitis with colon cancer.

Central nervous system neuronal surface antibody associated syndromes: review and guidelines for recognition

The concept of antibody mediated CNS disorders is relatively recent. The classical CNS paraneoplastic neurological syndromes are thought to be T cell mediated, and the onconeural antibodies merely biomarkers for the presence of the tumour. Thus it was thought that antibodies rarely, if ever, cause CNS disease. Over the past 10 years, identification of autoimmune forms of encephalitis with antibodies against neuronal surface antigens, particularly the voltage gated potassium channel complex proteins or the glutamate N-methyl-D-aspartate receptor, have shown that CNS disorders, often without associated tumours, can be antibody mediated and benefit from immunomodulatory therapies. The clinical spectrum of these diseases is not yet fully explored, there may be others yet to be discovered and some types of more common disorders (eg, epilepsy or psychosis) may prove to have an autoimmune basis. Here, the known conditions associated with neuronal surface antibodies are briefly reviewed, some general aspects of these syndromes are considered and guidelines that could help in the recognition of further disorders are suggested.

Anti-NMDA receptor encephalitis. The disorder, the diagnosis and the immunobiology

Anti-NMDAR encephalitis is a newly characterized syndrome with a progressive, predictable clinical course and the possibility of effective treatment. Accurate and timely diagnosis is critical to selection and implementation of treatments, and optimal patient outcomes. Outcomes are improved with early diagnosis via indirect immunofluorescence or cell-based assays, and the rapid and appropriate administration of immunosuppressant and anti-psychotic therapies. Three possible scenarios accounting for the immunopathogenesis of anti-NMDAR encephalitis are presented, with the most probable one being that of paraneoplastic autoimmunity. Future efforts in this disorder should focus on elucidating the mechanisms that contribute to initiation of this antibody response, as well as exploring the role of tumors, infectious triggers and immune-reactivation. Finally, accessible tools need to be developed that allow for reliable identification of specific antibody markers against synaptic proteins.

Immune mediated diseases and immune modulation in the neurocritical care unit

This chapter will review the spectrum of immune-mediated diseases that affect the nervous system and may result in an admission to the neurological intensive care unit. Immunomodulatory strategies to treat acute exacerbations of neurological diseases caused by aberrant immune responses are discussed, but strategies for long-term immunosuppression are not presented. The recommendations for therapeutic intervention are based on a synthesis of the literature, and include recommendations by the Cochrane Collaborative, the American Academy of Neurology, and other key organizations. References from recent publications are provided for the disorders and therapies in which randomized clinical trials and large evidenced-based reviews do not exist. The chapter concludes with a brief review of the mechanisms of action, dosing, and side effects of commonly used immunosuppressive strategies in the neurocritical care unit.

The emerging link between autoimmune disorders and neuropsychiatric disease

Abnormal autoimmune activity has been implicated in a number of neuropsychiatric disorders. In this review, the authors discuss a newly recognized class of synaptic autoimmune encephalitides as well as behavioral and cognitive manifestations of systemic autoimmune diseases.

Autoimmune encephalitis: a case series and comprehensive review of the literature

Encephalitic syndromes are a common medical emergency. The importance of early diagnosis and appropriate treatment is paramount. If initial investigations for infectious agents prove negative, other diagnoses must be considered promptly. Autoimmune encephalitides are being increasingly recognized as important (and potentially reversible) non-infectious causes of an encephalitic syndrome. We describe four patients with autoimmune encephalitis--3 auto-antibody positive, 1 auto-antibody negative--treated during the last 18 months. A comprehensive review of the literature in this expanding area will be of interest to the infectious diseases, general medical and neurology community.

Neurologic emergencies in patients who have cancer: diagnosis and management

The nervous system can be significantly affected by cancer. Neurologic symptoms are present in 30% to 50% of oncologic patients presenting to the emergency department or in neurologic consultation at teaching hospitals. Evaluation and treatment require collaborative effort between specialties. The causes of neurologic emergencies in patients with cancer are mostly related to effects of cancer, toxicities of treatments, infections, and paraneoplastic syndromes. These complications cause significant morbidity and mortality and require prompt and accurate diagnostic and treatment measures. This article reviews the common neurologic emergencies affecting patients with cancer and discusses epidemiology, clinical presentation, diagnosis, and treatment modalities.

Anti-NMDA-Receptor Encephalitis and Other Synaptic Autoimmune Disorders

OPINION STATEMENT

Synaptic autoimmunity may result in a wide variety of symptoms, including catatonia, psychosis, movement disorders, short-term memory deficits, and refractory seizures, so these patients are seen by a wide spectrum of practitioners, who need to be aware of these disorders. In some cases, these disorders occur as a paraneoplastic manifestation of an associated cancer. However, in contrast to the well-known paraneoplastic neurologic disorders of the central nervous system that predominate in older individuals, these novel disorders often affect children and young adults. Additionally, for some syndromes, the presence of a tumor does not necessarily indicate a poor prognosis. Successful treatment of the tumor and immunotherapy often result in recovery, supporting the use of surgery for severely ill patients. In all syndromes, deficits may be reversible despite the duration or severity of symptoms. For example, patients with anti-NMDA-receptor encephalitis who had been in a coma or ventilated for 6-10 months have had full recovery after appropriate treatment.

Current approaches to the treatment of paraneoplastic encephalitis

Paraneoplastic neurological syndromes (PNSs) cover a wide range of diseases and involve both the central nervous system (CNS) and peripheral nervous system. Paraneoplastic encephalitis comprises several diseases such as paraneoplastic cerebellar degeneration (PCD), limbic encephalitis (LE), paraneoplastic encephalomyelitis (PEM), brainstem encephalitis, opsomyoclonus syndrome, in addition to other even less frequently occurring entities. LE was the first historically identified CNS PNS, and similarities between other temporal lobe diseases such as herpes encephalitis have been elucidated. In the past few decades several autoantibodies have been described in association with LE. These encompass the classical 'onconeuronal' antibodies (abs) such as Hu, Yo, Ri and others, and now additionally abs towards either ion channels or surface antigens. The clinical core findings in LE are various mental changes such as amnesia or confusion, often associated with seizures. Careful characterization of psychiatric manifestations and/or associated neurological signs can help to characterize the syndrome and type of ab. The treatment options in LE depend on the aetiology. In LE caused by onconeuronal abs, the treatment options are poor. In two types of abs associated with LE, abs against ion channels and surface antigens (e.g. NMDA), immunomodulatory treatments seem effective, making these types of LE treatable conditions. However, LE can also occur without being associated with cancer, in which case only immunomodulation is required. Despite effective treatments, some patients' residual deficits remain, and recurrences have also been described.

The evaluation of rapidly progressive dementia

BACKGROUND

Rapidly progressive dementia (RPD) is a unique set of disorders resulting in cognitive, behavioral, and motor decline within 2 years. A variety of etiologies may contribute to RPD including neurodegenerative, inflammatory, infectious, and toxic-metabolic conditions. Jakob-Creutzfeldt disease (CJD) is frequently the most concerning diagnosis on the differential. The challenge for the neurologist is distinguishing prion disease from reversible processes that result in dementia.

REVIEW SUMMARY

This review discusses the clinical aspects and the diagnostic workup of RPD. Particular focus is given to both CJD and the potentially treatable inflammatory conditions that may cause a similar presentation. Furthermore, a standardized stepwise approach is outlined for patients presenting with RPD.

CONCLUSIONS

Neurologists should adopt a standardized approach to the rapidly presenting disease processes that may mimic CJD in their clinical and radiologic features.

GABA(B) receptor antibodies in limbic encephalitis and anti-GAD-associated neurologic disorders

BACKGROUND

γ-Aminobutyric acid-B receptor antibodies (GABA(B)R-ab) were recently described in 15 patients with limbic encephalitis (LE), associated with small-cell lung cancer (SCLC) or with concurrent glutamic acid decarboxylase (GAD) antibodies. We analyzed the frequency of GABA(B)R-ab in 147 patients with LE or neurologic syndromes associated with GAD-ab.

METHODS

We examined the presence of GABA(B)R-ab in 70 patients with LE (33 paraneoplastic with onconeural antibodies, 18 paraneoplastic without onconeural antibodies [5 with Gad-ab], and 19 idiopathic with either GAD-ab [5 patients] or seronegative) and 77 patients with GAD-ab-associated neurologic syndromes other than LE (29 stiff-person syndrome, 28 cerebellar ataxia, 14 epilepsy, and 6 with diverse paraneoplastic neurologic syndromes). GABA(B)R-ab were analyzed in serum or CSF by indirect immunofluorescence on HEK293 cells transfected with GABA(B1) and GABA(B2) receptor subunits.

RESULTS

GABA(B)R-ab were detected in 10 of the 70 patients with LE (14%). Eight had SCLC and 2 were idiopathic. One of the 8 patients with LE with SCLC had an additional onconeural antibody (Hu) and 2 GAD-ab. GABA(B)R-ab were identified in 7 (70%) of the 10 patients with LE and SCLC without onconeural antibodies. GABA(B)R-ab antibodies were not found in patients with GAD-ab and stiff-person syndrome, idiopathic cerebellar ataxia, or epilepsy. However, one patient with GAD-ab, paraneoplastic cerebellar ataxia, and anaplastic carcinoid of the thymus also presented GABA(B)R-ab.

CONCLUSIONS

GABA(B)R-ab are the most common antibodies found in LE associated with SCLC previously considered "seronegative." In patients with GAD-ab, the frequency of GABA(B)R-ab is low and only observed in the context of cancer.

Autoimmune limbic encephalitis

Limbic encephalitis (LE) was first described in 1960 by Brierley et al. and was defined by an acute or subacute temporal lobe epilepsy, memory loss and psychiatric disturbances. Corsellis et al. then demonstrated that LE was associated with small-cell lung cancer and a paraneoplastic origin of LE was suggested. In the 1980s, onconeuronal antibodies specific to paraneoplastic neurological syndromes were described and some of them, such as Hu-Ab, were clearly associated with LE. In the last 20 years, other onconeuronal antibodies targeting intracellular antigens were subsequently identified and LE was considered as a rare paraneoplastic neurological syndrome with a poor outcome and as mainly being associated with Hu-Ab, Ma2-Ab or CV2/CRMP5-Ab. The concept of LE has dramatically evolved since 2004, with the description of LE becoming associated with novel autoantibodies that target neuronal surface rather than intracellular antigens. In these cases, LE was not always paraneoplastic. Interestingly, these newly described LE cases offer a much better prognosis than the previous ones. At present, LE is considered to be an autoimmune disorder that can be paraneoplastic or not and could be more frequent than previously suspected. The associated antibodies lead to the classification of different subtypes of LE and are used as prognostic markers. Those that are directed against cell surface antigens could play a direct role in the neurological symptoms of LE.

The emerging link between autoimmune disorders and neuropsychiatric disease

Abnormal autoimmune activity has been implicated in a number of neuropsychiatric disorders. In this review, the authors discuss a newly recognized class of synaptic autoimmune encephalitides as well as behavioral and cognitive manifestations of systemic autoimmune diseases.

Diagnosing central nervous system vasculitis in children

PURPOSE OF REVIEW

To review the current literature of childhood central nervous system vasculitis, and to discuss a tailored approach to diagnosis and treatment based on recent evidence.

RECENT FINDINGS

Primary angiitis of the central nervous system in children (cPACNS) is an increasingly recognized inflammatory brain disease with potentially devastating neurological consequences. The diagnostic approach should be tailored to the clinical presentation of the child with suspected cPACNS and should address the expanding spectrum of inflammatory and noninflammatory brain diseases with overlapping clinical features. New evidence has confirmed that elective brain biopsies in children have a higher diagnostic yield than in adults and improve our ability to diagnose angiography-negative cPACNS. Finally, observational studies have shown that early diagnosis and aggressive treatment lead to improved neurological outcomes and lower mortality rates in patients with cPACNS.

SUMMARY

This review summarizes the recent data on diagnosis, classification, treatment, and outcomes in cPACNS. Our improved understanding of cPACNS facilitates a tailored diagnostic approach that results in earlier diagnosis and initiation of therapy for this potentially reversible condition.