Calcium-channel antibodies in the Lambert-Eaton syndrome and other paraneoplastic syndromes

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.

Potassium channel complex autoimmunity induced by inhaled brain tissue aerosol

OBJECTIVE

To test the hypothesis that autoimmunity induced by inhalation of aerosolized brain tissue caused outbreaks of sensory-predominant polyradiculoneuropathy among swine abattoir employees in the Midwestern United States.

METHODS

Mice were exposed intranasally, 5 days per week, to liquefied brain tissue. Serum from exposed mice, patients, and unaffected abattoir employees were analyzed for clinically pertinent neural autoantibodies.

RESULTS

Patients, coworkers, and mice exposed to liquefied brain tissue had an autoantibody profile dominated by neural cation channel immunoglobulin Gs (IgGs). The most compelling link between patients and exposed mice was magnetic resonance imaging (MRI) evidence of grossly swollen spinal nerve roots. Autoantibody responses in patients and mice were dose-dependent and declined after antigen exposure ceased. Autoantibodies detected most frequently, and at high levels, bound to detergent-solubilized macromolecular complexes containing neuronal voltage-gated potassium channels ligated with a high affinity Kv1 channel antagonist, 125I-α-dendrotoxin. Exposed mice exhibited a behavioral phenotype consistent with potassium channel dysfunction recognized in drosophila with mutant ("shaker") channels: reduced sensitivity to isoflurane-induced anesthesia. Pathological and electrophysiological findings in patients supported peripheral nerve hyperexcitability over destructive axonal loss. The pain-predominant symptoms were consistent with sensory nerve hyperexcitability.

INTERPRETATION

Our observations establish that inhaled neural antigens readily induce neurological autoimmunity and identify voltage-gated potassium channel complexes as a major immunogen.

Lambert-Eaton myasthenic syndrome: from clinical characteristics to therapeutic strategies

Lambert-Eaton myasthenic syndrome (LEMS) is a neuromuscular autoimmune disease that has served as a model for autoimmunity and tumour immunology. In LEMS, the characteristic muscle weakness is thought to be caused by pathogenic autoantibodies directed against voltage-gated calcium channels (VGCC) present on the presynaptic nerve terminal. Half of patients with LEMS have an associated tumour, small-cell lung carcinoma (SCLC), which also expresses functional VGCC. Knowledge of this association led to the discovery of a wide range of paraneoplastic and non-tumour-related neurological disorders of the peripheral and central nervous systems. Detailed clinical studies have improved our diagnostic skills and knowledge of the pathophysiological mechanisms and association of LEMS with SCLC, and have helped with the development of a protocol for early tumour detection.

Paraneoplastic gastrointestinal dysmotility: when to consider and how to diagnose

In this review of dysmotility in cancer patients, we have focused on paraneoplastic GI dysmotility as it provides an excellent example of how derangements of the neuromuscular apparatus of the gut can affect GI motility. A high index of clinical suspicion, together with serologic evaluation using a panel of autoantibodies in selected patients, is important in ensuring the early diagnosis of paraneoplastic GI dysmotility and may help guide management. Although it remains unproved that paraneoplastic antibodies are pathogenic, they are useful diagnostic markers. A better understanding of the pathogenesis of these disorders, including the role of paraneoplastic antibodies, will, hopefully, lead to earlier diagnosis and improved adjunctive, immunology-based treatments. Furthermore, even though successful treatment of the underlying cancer may not lead to reversal of the GI dysmotility, the recognition of a paraneoplastic syndrome may lead to early cancer diagnosis and a better chance of successful treatment of the cancer and overall survival. Although rare, it is imperative that clinicians be aware of the association between malignancy and GI dysmotility so that they know when to investigate for an underlying malignancy.

John Newsom-Davis: clinician-scientist and so much more

John Newsom-Davis was born in 1932 and died, aged 74, in 2007. After national service in the Royal Air Force, he read Natural Sciences at Cambridge. Following clinical studies at the Middlesex Hospital, he began research into respiratory neurophysiology with Tom Sears at the National Hospital, Queen Square, in London, and spent 1 year with Fred Plum at Cornell University in New York. After neurology specialist training at Queen Square, he became the director of the Batten Unit, continuing his interest in respiratory physiology. There he began to work on myasthenia gravis in collaboration with Ricardo Miledi at University College London and in 1978, after performing the first studies on plasma exchange in that disease, he established a myasthenia gravis research group at the Royal Free Hospital. There he investigated the role of the thymus in this disease and demonstrated an autoimmune basis for the Lambert Eaton myasthenic syndrome and 'seronegative' myasthenia. He was awarded the first Medical Research Council Clinical Research Professorship in 1979 but moved to Oxford in 1987 when he was elected Action Research Professor of Neurology. While at Oxford, he continued to run a very successful multidisciplinary group, researched further into the thymic abnormalities and cellular immunology of myasthenia, identified antibody-mediated mechanisms in acquired neuromyotonia, and began the molecular work that identified the genetic basis for many forms of congenital myasthenic syndrome. Meanwhile, he was also involved in university and college governance and contributed widely to the Medical Research Council, government committees, research charities and the Association of British Neurologists. Among many honours, he was elected Fellow of the Royal Society in 1991, appointed Commander of the British Empire in 1996 and made a Foreign Associate Member of the Institute of Medicine of the United States in 2001. Nearing and following retirement from Oxford, where he continued to see patients with myasthenia, he was the President of the Association of British Neurologists and Editor of Brain, and led a National Institutes of Health-funded international trial of thymectomy.

Paraneoplastic encephalomyelopathies: pathology and mechanisms

The last three decades have seen major advances in the understanding of paraneoplastic and idiopathic autoimmune disorders affecting the central nervous system (CNS). Neural-specific autoantibodies and their target antigens have been discovered, immunopathology and neuroimaging patterns recognized and pathogenic mechanisms elucidated. Disorders accompanied by autoantibody markers of neural peptide-specific cytotoxic effector T cells [such as anti-neuronal nuclear antibody type 1 (ANNA-1, aka anti-Hu), Purkinje cell antibody type 1 (PCA-1, aka anti-Yo) and CRMP-5 IgG] are generally poorly responsive to immunotherapy. Disorders accompanied by neural plasma membrane-reactive autoantibodies [the effectors of synaptic disorders, which include antibodies targeting voltage-gated potassium channel (VGKC) complex proteins, NMDA and GABA-B receptors] generally respond well to early immunotherapy. Here we describe in detail the neuropathological findings and pathophysiology of paraneoplastic CNS disorders with reference to antigen-specific serology and neurological and oncological contexts.

Lung cancer-induced paraneoplastic syndromes

PURPOSE OF REVIEW

Paraneoplastic syndromes occur commonly in patients with lung cancer, especially cancers of neuroendocrine origin. The syndromes can be the first clinical manifestation of malignant disease or a harbinger of cancer recurrence. To update the knowledge that would facilitate the care of lung cancer patients with paraneoplastic syndromes, this review focuses on the epidemiology, pathogenesis, clinical features, and current management of the more common and clinically relevant syndromes.

RECENT FINDINGS

Certain combinations of clinical signs and symptoms (endocrine, neurologic, immunologic, dermatologic, metabolic, constitutional, and hematologic) are associated with lung carcinoma as a manifestation of the secretion of cytokines and hormones by these cells or as an associated immunologic response. These syndromes can be categorized by common causative mechanisms: hormonal syndromes, autoimmune syndromes, and other syndromes of less clear cause. Recent advances in medical technology have allowed better understanding of these syndromes and the development of novel diagnostic and therapeutic tools.

SUMMARY

Increased awareness of paraneoplastic syndromes associated with lung cancer should lead to the earlier recognition and diagnosis of malignancies, thereby improving the overall prognosis of patients and alleviating associated comorbidities. Despite the recent advances in recognizing and treating paraneoplastic syndromes, many questions remain to be answered.

Lambert-eaton myasthenic syndrome

Lambert Eaton myasthenic syndrome (LEMS) is a rare neuromuscular junction disease. Often, the signs and symptoms of LEMS are mistaken for myasthenia gravis and therefore the workup is misdirected. A physician must look for an occult malignancy when the diagnosis is made and then continue to search for a malignancy for at least 5 years after diagnosis. The diagnosis of LEMS can be confirmed with electrophysiologic studies or with serum calcium channel antibodies. In most patients with LEMS, 3,4-diaminopyridine will improve strength. In patients without malignancy, immunosuppressants do have a role in the treatment of LEMS. Patients and physicians must be aware that certain situations and drugs may exacerbate weakness.

Neural autoantibody evaluation in functional gastrointestinal disorders: a population-based case-control study

BACKGROUND

Our goal is to investigate the serum profile of neural autoantibodies in community-based patients with irritable bowel syndrome (IBS) or functional dyspepsia. The pathogenesis of functional gastrointestinal (GI) disorders, including IBS and dyspepsia, are unknown. Theories range from purely psychological to autoimmune alterations in GI tract neuromuscular function.

METHODS

The study subjects, based in Olmsted County, MN, reported symptoms of functional dyspepsia or IBS (n = 69), or were asymptomatic controls (n = 64). Their coded sera were screened for antibodies targeting neuronal, glial, and muscle autoantigens.

RESULTS

The prevalence of neural autoantibodies with functional GI disorders did not differ significantly from controls (17% vs. 13%; P = 0.43). In no case was a neuronal or glial nuclear autoantibody or enteric neuronal autoantibody identified. Neuronal cation channel antibodies were identified in 9% of cases (voltage-gated potassium channel [VGKC] in one dyspepsia case and one IBS case, ganglionic acetylcholine receptor [AChR] in four IBS cases) and in 6% of controls (ganglionic AChR in one, voltage-gated calcium channel [VGCC], N-type, in two and VGKC in one; P = 0.36). The frequency of glutamic acid decarboxylase-65 (GAD65) autoantibodies was similar in cases (10%) and controls (5%; P = 0.23).

CONCLUSIONS

Our data do not support neural autoimmunity as the basis for most IBS or functional dyspepsia cases.

Treatment for Lambert-Eaton myasthenic syndrome

BACKGROUND

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of neuromuscular transmission. Treatments attempt to overcome the harmful autoimmune process, or improve residual neuromuscular transmission

OBJECTIVES

The objective was to examine the efficacy of treatment in Lambert-Eaton myasthenic syndrome.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Specialized Register (12 October 2010), the Cochrane Central Register of Controlled Trials (CENTRAL) (12 October 2010, Issue 4 2010 in the Cochrane Library), MEDLINE (January 1966 to September 2010) and EMBASE (January 1980 to September 2010).

SELECTION CRITERIA

All randomised or quasi-randomised trials of adults and children with a diagnosis of Lambert-Eaton myasthenic syndrome, with or without small-cell lung cancer, receiving any form of pharmacological or physical treatment.

DATA COLLECTION AND ANALYSIS

All authors independently assessed studies for inclusion and extracted data. Study authors were contacted for missing information when possible.

MAIN RESULTS

Four controlled trials of 3,4-diaminopyridine compared with placebo in a total of 54 participants with Lambert-Eaton myasthenic syndrome were eligible: three cross-over trials and one parallel group. Two were added at this update. One of these trials also assessed pyridostigmine in conjunction with 3,4-diaminopyridine. A further cross-over trial compared intravenous immunoglobulin (IVIg) to placebo in nine participants.Four trials of 3,4-diaminopyridine reported significant improvement in the primary outcome, muscle strength score, or myometric limb measurement for between hours and a week following treatment, and significant improvement in resting compound muscle action potential (CMAP) amplitude following 3,4-diaminopyridine, compared with placebo.A meta-analysis of the primary endpoint showed Quantitative Myasthenia Gravis (QMG) muscle score assessed between three and eight days was likely to improve by a mean of 2.44 points (95% confidence interval 3.6 to 1.22). Meta-analysis of the secondary endpoint CMAP amplitude also showed a mean improvement of 1.36 mV (95% confidence interval 0.99 to 1.72) over the same period. The risk of bias was determined to be low, and quality of evidence moderate to high.A single cross-over trial reported significant improvement in myometric limb strength and non-significant improvement in mean resting CMAP amplitude with IVIg compared to placebo. Clinical improvement lasted for up to eight weeks.

AUTHORS' CONCLUSIONS

Limited but moderate to high quality evidence from randomised controlled trials showed that over days 3,4-diaminopyridine, or for up to 8 weeks IVIg, improved muscle strength scores and CMAP amplitudes in participants with Lambert-Eaton myasthenic syndrome. There are insufficient data at present to quantify this effect. Other possible treatments have not been tested in randomised controlled trials.

Neuromuscular paraneoplastic syndromes: the Lambert-Eaton myasthenic syndrome

BACKGROUND

Disorders in which the effects of cancer occur at a site remote from the primary tumor are termed paraneoplastic disorders. The most well- known paraneoplastic disorder affecting the neuromuscular junction is the Lambert-Eaton myasthenic syndrome (LEMS).

DISCUSSION

We describe a case of the Lambert-Eaton myasthenic syndrome diagnosed in a patient with small cell lung cancer presenting with profound weakness. The discussion that follows the case describes the pathophysiology of the disorder, clinical characteristics and therapies that have been used. The role of the palliative care team in the case is described.

Case report: a case review of Lambert-Eaton myasthenic syndrome and low back pain

The following is a case report which reviews the essential aspects of Lambert-Eaton myasthenic syndrome (LEMS) in a patient with long standing back pain and gait dysfunction. The patient was referred to our electrodiagnostics laboratory for a 9-month history of low back pain and difficulty walking following a charity breast cancer walk. A workup including magnetic resonance imaging of the brain, entire spine, and EMG/NCS at another institution were reportedly normal. A detailed history revealed symptoms of proximal weakness and autonomic dysfunction. Physical findings were consistent with proximal weakness, a bilateral gluteus medius gait, and diffusely absent reflexes obtainable in the biceps after 3 s of contraction. Electrical testing revealed an initial low compound muscle action potential amplitude in the deep peroneal nerve recording from the extensor digitorum brevis. Repetitive stimulation at 2 Hz revealed a decremental response of 42% from the 1st response to the 4th response. Following 3 s of exercise, the amplitude increased by 300%. After 30 s of exercise followed by 1 min of rest, there was a return of the decremental response. The history, physical examination, and electrical findings were illustrative of a presynaptic neuromuscular junction disorder, specifically LEMS.

Update on treatment options for Lambert-Eaton myasthenic syndrome: focus on use of amifampridine

In Lambert-Eaton myasthenic syndrome (LEMS), antibodies against presynaptic voltage-gated calcium channels reduce the quantal release of acetylcholine, causing muscle weakness and autonomic dysfunction. More than half of the affected patients have associated small cell lung cancer, and thorough screening for an underlying malignancy is crucial. The mainstay of treatment for LEMS is symptomatic but immunotherapy is needed in more severely affected patients. Symptomatic therapies aim at increasing the concentration of acetylcholine at the muscle endplate. While acetylcholinesterase inhibitors were the first drugs to be used for the amelioration of symptoms, 3,4-diaminopyridine (3,4-DAP, amifampridine) has been shown to be more effective. 3,4-DAP blocks presynaptic potassium channels, thereby prolonging the action potential and increasing presynaptic calcium concentrations. This then results in increased quantal release of acetylcholine. The efficacy of 3,4-DAP for increasing muscle strength and resting compound muscle action potentials has been demonstrated by four placebo-controlled trials. Side effects are usually mild, and the most frequently reported are paresthesias. The most common serious adverse events are epileptic seizures. 3,4-DAP is currently the treatment of choice in patients with Lambert-Eaton myasthenic syndrome.

Recombinant expression of the AChR-alpha1 subunit for the detection of conformation-dependent epitopes in Myasthenia Gravis

Detection of autoantibodies associated with neurological disease typically involves immunoprecipitation of radioactively labeled native proteins. We explored whether single receptor subunits, fused to Renilla luciferase (Ruc), could detect patient autoantibodies in Luciferase Immunoprecipitation Systems. Myasthenia Gravis patient sera were tested for conformational autoantibodies to only the α1-subunit of the nicotinic acetylcholine receptor (AChR). Using a panel of 10 AChR-α1 fragments, AChR-α1-Δ5-Ruc demonstrated the highest immunoreactivity with a conformational-specific antibody and the highest sensitivity in a pilot cohort. Testing a larger cohort with AChR-α1-Δ5-Ruc demonstrated 21% sensitivity and 97% specificity. A point mutation within Ruc increased the diagnostic performance of AChR-α1-Δ5 (32% sensitivity, 97% specificity). The (125)I-α-bungarotoxin multi-subunit AChR assay demonstrated 63% sensitivity and 97% specificity. These findings highlight the difficulty in detecting Myasthenia Gravis conformational epitopes across assay formats and lay the foundation for detecting autoantibodies to defined recombinant chains of the AChR and potentially other neurotransmitter receptors.

The auto-antigen repertoire in myasthenia gravis

Myasthenia Gravis (MG) is an antibody-mediated autoimmune disorder affecting the postsynaptic membrane of the neuromuscular junction (NMJ). MG is characterized by an impaired signal transmission between the motor neuron and the skeletal muscle cell, caused by auto-antibodies directed against NMJ proteins. The auto-antibodies target the nicotinic acetylcholine receptor (nAChR) in about 90% of MG patients. In approximately 5% of MG patients, the muscle specific kinase (MuSK) is the auto-antigen. In the remaining 5% of MG patients, however, antibodies against the nAChR or MuSK are not detectable (idiopathic MG, iMG). Although only the anti-nAChR and anti-MuSK auto-antibodies have been demonstrated to be pathogenic, several other antibodies recognizing self-antigens can also be found in MG patients. Various auto-antibodies associated with thymic abnormalities have been reported, as well as many non-MG-specific auto-antibodies. However, their contribution to the cause, pathology and severity of the disease is still poorly understood. Here, we comprehensively review the reported auto-antibodies in MG patients and discuss their role in the pathology of this autoimmune disease.

Clinical presentation of immune-mediated cerebellar ataxia

INTRODUCTION

Accumulation of recent clinical evidence indicates that the immune system plays an important role in some central nervous system diseases usually regarded as degenerative. The most striking example is paraneoplastic cerebellar ataxia (PCA), which is characterized by autoimmune cross-reaction between tumoral and nervous system antigens.

STATE OF THE ART

In the past 20 years, several antibodies directed against neuronal and tumoral antigens have been described in association with PCA, leading to the description of different subtypes of PCA based on the associated antibodies, the clinical course and the type of tumor. In some subtypes, cerebellar ataxia occurs in isolation, whereas in others, cerebellar ataxia is a syndrome that occurs in conjunction with extensive nervous system disease. Circulating antibodies have also been described in patients with non-paraneoplastic cerebellar ataxia (N-PCA), suggesting that the immune system may be involved in certain cases of sporadic cerebellar ataxia.

PERSPECTIVE

Immune-mediated cerebellar ataxia does not seem to be limited to paraneoplastic neurological syndromes. Further studies are however necessary to understand the exact pathophysiology of these disorders and offer effective treatments.

CONCLUSION

In this review, the clinical presentation of the different subtypes of potentially immune-mediated PCA and N-PCA will be described, and the associated tumors will be discussed.

Role of calcium channels in congenital heart block

Congenital heart block (CHB) is a conduction abnormality that affects hearts of foetuses and/or newborn to mothers with autoantibodies reactive with the intracellular soluble ribonucleoproteins 48-kD La, 52-kD Ro and 60-kD Ro. CHB carries substantial mortality and morbidity, with more than 60% of affected children requiring lifelong pacemakers. Several hypotheses have been proposed to explain the pathogenesis of CHB. These can be grouped under three main hypotheses: Apoptosis, Serotoninergic and Ca channel hypothesis. Here, we discuss these hypotheses and provide recent scientific thinking that will most likely dominate the future of this field of research.

Guidelines on the use of therapeutic apheresis in clinical practice--evidence-based approach from the Apheresis Applications Committee of the American Society for Apheresis

The American Society for Apheresis (ASFA) Apheresis Applications Committee is charged with a review and categorization of indications for therapeutic apheresis. Beginning with the 2007 ASFA Special Issue (fourth edition), the subcommittee has incorporated systematic review and evidence-based approach in the grading and categorization of indications. This Fifth ASFA Special Issue has further improved the process of using evidence-based medicine in the recommendations by refining the category definitions and by adding a grade of recommendation based on widely accepted GRADE system. The concept of a fact sheet was introduced in the Fourth edition and is only slightly modified in this current edition. The fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis. The article consists of 59 fact sheets devoted to each disease entity currently categorized by the ASFA as category I through III. Category IV indications are also listed.

Chronic monoarthritis and foot-drop as a paraneoplastic syndrome in prostate cancer

Paraneoplastic rheumatic symptoms, caused by a malignancy, but not directly related to invasion by the tumor or its metastases are the result of a wide variety of tumor-derived biologic mediators. Recognition of paraneoplastic rheumatic syndromes is important, as it may lead to an early diagnosis of cancer. We report a 71-year-old patient with prostate cancer, presented with chronic monoarthritis of the left ankle and foot-drop. Monoarthritis and foot-drop was resistant to non-steroidal anti-inflammatory drugs and corticosteroids. After tumor resection, synovitis resolved and foot-drop disappeared almost totally.

Severe and progressive neurotransmitter release aberrations in familial hemiplegic migraine type 1 Cacna1a S218L knock-in mice

Familial hemiplegic migraine type 1 (FHM1) is caused by mutations in the CACNA1A gene, encoding neuronal presynaptic Ca(V)2.1 (P/Q-type) Ca(2+) channels. These channels mediate neurotransmitter release at many central synapses and at the neuromuscular junction (NMJ). Mutation S218L causes a severe neurological phenotype of FHM and, additionally, ataxia and susceptibility to seizures, delayed brain edema, and fatal coma after minor head trauma. Recently, we generated a Cacna1a S218L knock-in mutant mouse, displaying these features and reduced survival. A first electrophysiological study showed high susceptibility for cortical spreading depression, enhanced neuronal soma Ca(2+) influx, and at diaphragm NMJs, a considerable increase of neurotransmitter release. We here assessed the function of S218L knock-in NMJs at several muscle types in great detail. Pharmacological analyses using specific Ca(V) subtype-blocking toxins excluded compensatory contribution of non-Ca(V)2.1 channels. Endplate potentials were considerably broadened at many NMJs. High rate (40 Hz)-evoked acetylcholine release was slightly reduced; however, it was not associated with block of neurotransmission causing weakness, as assessed with grip strength measurements and in vitro muscle contraction experiments. The synaptopathy clearly progressed with age, including development of an increased acetylcholine release at low-rate nerve stimulation at physiological extracellular Ca(2+) concentration and further endplate potential broadening. Our results suggest enhanced Ca(2+) influx into motor nerve terminals through S218L-mutated presynaptic Ca(V)2.1 channels, likely because of the earlier reported negative shift of activation potential and reduced inactivation. Similar severe aberrations at central synapses of S218L mutant mice and humans may underlie or contribute to the drastic neurological phenotype.

Paraneoplastic limbic encephalitis presenting as a neurological emergency: a case report

Introduction

Paraneoplastic limbic encephalitis remains a challenging clinical diagnosis with poor outcome if it is not recognized and treated early in the course of the disease.

Case Presentation

A 65-year-old Caucasian woman presented with generalized tonic-clonic seizures and increasing confusion shortly after a lung biopsy that led to the diagnosis of small-cell lung cancer. She had a complicated hospital course, and had recurrent respiratory distress due to aspiration pneumonia, and fluctuating mental status and seizures that were refractory to anti-epileptic drug treatment. Routine laboratory testing, magnetic resonance imaging of the brain, electroencephalogram, lumbar puncture, serum and cerebrospinal fluid tests for paraneoplastic antibodies, and chest computed tomography were performed on our patient. The diagnosis was paraneoplastic limbic encephalitis in the setting of small-cell lung cancer with positive N-type voltage-gated calcium channel antibody titer. Anti-epileptic drugs for seizures, chemotherapy for small-cell lung cancer, and intravenous immunoglobulin and steroids for paraneoplastic limbic encephalitis led to a resolution of her seizures and improved her mental status.

Conclusion

Early recognition of paraneoplastic limbic encephalitis and prompt intervention with immune therapies at the onset of presentation will probably translate into more favorable neurological outcomes.

Congenital heart block: identification of autoantibody binding site on the extracellular loop (domain I, S5-S6) of alpha(1D) L-type Ca channel

Congenital heart block (CHB) is an autoimmune disease associated with autoantibodies against intracellular ribonucleoproteins SSB/La and SSA/Ro. The hallmark of CHB is complete atrioventricular block. We have recently established that anti-SSA/Ro -SSB/La autoantibodies inhibit alpha(1D) L-type Ca current, I(Ca-L), and cross-react with the alpha(1D) Ca channel protein. This study aims at identifying the possible binding sites on alpha(1D) protein for autoantibodies from sera of mothers with CHB children. GST fusion proteins of the extracellular regions between the transmembrane segments (S5-S6) of each of the four alpha(1D) Ca channel protein domains I-IV were prepared and tested for reactivity with sera from mothers with CHB children and controls using ELISA. Sera containing anti-Ro/La autoantibodies from 118 mothers with CHB children and from 15 mothers with anti-Ro/La autoantibodies but have healthy children, and from 28 healthy mothers without anti-Ro/La autoantibodies and healthy children were evaluated. Seventeen of 118 (14.4%) sera from mothers with CHB children reacted with the extracellular loop of domain I S5-S6 region (E1). In contrast, only 2 of 28 (7%) of sera from healthy mothers (-anti-Ro/La) and healthy children reacted with E1 loop and none (0 of 15) of sera from healthy mothers (+anti-Ro/La) and healthy children reacted with the E1 loop. Preincubation of E1 loop with the positive sera decreased the O.D reading establishing the specificity of the response. Electrophysiological characterization of the ELISA positive sera and purified IgG showed inhibition (44.1% and 49.8%, respectively) of the alpha(1D) I(Ca-L) expressed in tsA201 cells. The inhibition was abolished when the sera were pre-incubated with E1 fusion protein. The results identified the extracellular loop of domain I S5-S6 of L-type Ca channel alpha(1D) subunit as a target for autoantibodies from a subset of mothers with CHB children. This novel finding provides insights into the potential development of therapeutic peptides that could bind to the pathogenic antibodies and prevent CHB.

Achalasia, chronic sensory neuropathy, and N-type calcium channel autoantibodies: beneficial response to IVIG

Autoimmune gastrointestinal dysmotility (AGID) can result from paraneoplastic onconeuronal antibodies. Patients may present with regional hypomotility anywhere along the gastrointestinal tract. We report a case of a woman who developed an insidious sensory neuropathy and achalasia. She was found to have a high-titer of N-type voltage gated-calcium channel (VGCC) antibodies. She demonstrated clinical and electrophysiological improvement of her neuropathy, as well as improvement of her swallowing and gait, after treatment with intravenous immunoglobulins.

Neural autoantibody profile of primary achalasia

The etiology and pathogenesis of primary achalasia are both unknown. Postulated mechanisms include autoimmune, viral-immune, and central neurodegenerative. The aim of this study is to investigate the serum profile of neural autoantibodies in patients with primary achalasia. Coded sera from 70 patients with primary achalasia and 161 healthy control subjects, matched in sex, age, and smoking habits, were screened for antibodies targeting neuronal, glial, and muscle autoantigens. No specific myenteric neuronal antibody was identified. However, the overall prevalence of neural autoantibodies in patients with primary achalasia was significantly higher than in healthy control subjects (25.7 vs. 4.4%, P < 0.0001). Most noteworthy was the 21.4% frequency of glutamic acid decarboxylase-65 antibody in patients with achalasia (versus 2.5% in control subjects), in the absence of diabetes or companion antibodies predictive of type 1 diabetes. This profile of autoantibodies suggests an autoimmune basis for a subset of primary achalasia.

Favorable response to rituximab in a patient with anti-VGCC-positive Lambert-Eaton myasthenic syndrome and cerebellar dysfunction

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease that is characterized by impaired transmission across the neuromuscular junction due to autoantibodies directed against the presynaptic voltage-gated calcium channels (VGCC-ab). Clinical symptoms are usually characterized by proximal muscle weakness and mild dysautonomia. In some patients there are signs of cerebellar dysfunction as well, usually associated with cancer. Here we report the long-term follow-up of a patient with VGCC-ab-positive LEMS and a severe cerebellar syndrome but without evidence of cancer over 5 years. While conventional immunosuppressive therapy (steroids, azathioprine) failed, he improved with plasma exchange and consecutive treatment with rituximab. Muscle Nerve 40: 305-308, 2009.

Pathophysiological actions of neuropathy-related anti-ganglioside antibodies at the neuromuscular junction

The outer leaflet of neuronal membranes is highly enriched in gangliosides. Therefore, specific neuronal roles have been attributed to this family of sialylated glycosphingolipids, e.g. in modulation of ion channels and transporters, neuronal interaction and recognition, temperature adaptation, Ca(2+) homeostasis, axonal growth, (para)node of Ranvier stability and synaptic transmission. Recent developmental, ageing and injury studies on transgenic mice lacking subsets of gangliosides indicate that gangliosides are involved in maintenance rather than development of the nervous system and that ganglioside family members are able to act in a mutually compensatory manner. Besides having physiological functions, gangliosides are the likely antigenic targets of autoantibodies present in Guillain-Barré syndrome (GBS), a group of neuropathies with clinical symptoms of motor- and/or sensory peripheral nerve dysfunction. Antibody binding to peripheral nerves is thought to either interfere with ganglioside function or activate complement, causing axonal damage and thereby disturbed action potential conduction. The presynaptic motor nerve terminal at the neuromuscular junction (NMJ) may be a prominent target because it is highly enriched in gangliosides and lies outside the blood-nerve barrier, allowing antibody access. The ensuing neuromuscular synaptopathy might contribute to the muscle weakness in GBS patients. Several groups, including our own, have studied the effects of anti-ganglioside antibodies in ex vivo and in vivo experimental settings at mouse NMJs. Here, after providing a background overview on ganglioside synthesis, localization and physiology, we will review those studies, which clearly show that anti-ganglioside antibodies are capable of binding to NMJs and thereby can exert a variety of pathophysiological effects. Furthermore, we will discuss the human clinical electrophysiological and histological evidence produced so far of the existence of a neuromuscular synaptopathy contributing to muscle weakness in GBS patients.

Antineuronal antibodies in sporadic late-onset cerebellar ataxia

Sporadic late-onset cerebellar ataxia of unknown cause is considered a neurodegenerative disorder whose underlying mechanisms are still unknown. To identify antineuronal autoantibodies, immunohistochemical and immunoblotting techniques were performed in 67 patients with sporadic cerebellar degeneration of unknown cause. Elevated P/Q-type voltage-gated calcium channel (VGCC)-specific antibodies were found in eight patients (11.9%). There was no hint of a paraneoplastic disorder in any of the patients. The present findings suggest an autoimmune contribution to the pathophysiology of a subgroup of sporadic late-onset cerebellar ataxia.

Association of N-type calcium channel autoimmunity in patients with autoimmune autonomic ganglionopathy

The nicotinic acetylcholine receptor (nAChR) antibody directly contributes to the autonomic dysfunction in Autoimmune Autonomic Ganglionopathy (AAG). The pathological mechanism leading to autonomic dysfunction in seronegative AAG is unclear. We evaluated patients with presumed antibody negative AAG (n=49) to determine whether there was an association with other autoantibodies. Three patients met the clinical criteria and were positive for N-type calcium channel antibodies. All patients had severe autonomic dysfunction characterized by orthostatic hypotension and gastrointestinal involvement. Autonomic testing revealed severe impairment of sudomotor, cardiovagal, and adrenergic domains. These findings raise the possibility that other autoantibodies may contribute to the pathogenesis of AAG.

Myasthenia gravis with presynaptic electrophysiologic abnormalities

OBJECTIVES

To describe the clinical, serologic, and electrophysiologic features of 2 patients with myasthenia gravis (MG), who also had presynaptic electrophysiologic abnormalities.

METHODS

Case reports.

RESULTS

Two patients developed clinical symptoms consistent with MG. They lacked autonomic symptoms or signs, and their reflexes were not absent. Acetylcholine receptor antibody studies were positive, but assays for voltage-gated calcium channel antibodies were negative. Low-amplitude baseline compound muscle action potentials combined with large incremental responses immediately after exercise were consistent with a presynaptic disorder. Thymic pathology in 1 patient was characteristic of autoimmune MG showing lymphoid follicular hyperplasia. No underlying malignancy was found in either patient.

CONCLUSIONS

Patients with MG may rarely have presynaptic electrophysiologic abnormalities. This may occur even in the absence of the typical clinical and serologic features of the Lambert-Eaton syndrome. It is possible that there is another antibody present that is modulating presynaptic acetylcholine release.

The ataxic Cacna1a-mutant mouse rolling nagoya: an overview of neuromorphological and electrophysiological findings

Homozygous rolling Nagoya natural mutant mice display a severe ataxic gait and frequently roll over to their side or back. The causative mutation resides in the Cacna1a gene, encoding the pore-forming α₁ subunit of Ca_v2.1 type voltage-gated Ca²⁺ channels. These channels are crucially involved in neuronal Ca²⁺ signaling and in neurotransmitter release at many central synapses and, in the periphery, at the neuromuscular junction. We here review the behavioral, histological, biochemical, and neurophysiological studies on this mouse mutant and discuss its usefulness as a model of human neurological diseases associated with Ca_v2.1 dysfunction.

Monozygous twins with neuromuscular transmission defects at opposite sides of the motor endplate

Disorders affecting the postsynaptic side of the neuromuscular junction include autoimmune myasthenia gravis (MG) as well as some of the congenital myasthenic syndromes (CMS). Lambert-Eaton myasthenic syndrome (LEMS) is an acquired autoimmune neuromuscular disorder in which autoantibodies are directed against the presynaptic calcium channels. Here we describe two monozygous twin brothers: case 1 was diagnosed with an indeterminate form of acquired postsynaptic neuromuscular junction defect at age 32 and case 2 with LEMS at age 47. Case 1 presented clinically with mild generalized myasthenic weakness, neurophysiological examination revealed disturbed neuromuscular transmission along with probable myositis and serum analysis regarding antibodies against the acetylcholine receptor and muscle-specific tyrosine kinase was negative. Case 2 presented with proximal muscle fatigue accompanied by areflexia at rest and antibodies against the P/Q-type voltage-gated calcium channels were present. Neurophysiologically, case 2 had reduced baseline compound motor action potential amplitudes on neurography, decrement on low-frequency repetitive nerve stimulation (RNS) and pathological increment on high frequency RNS. To our knowledge this is the first case report of its kind and adds an intriguing contrast to the more common diagnosis of CMS in monozygous twins.

New techniques in the tissue diagnosis of gastrointestinal neuromuscular diseases

Gastrointestinal neuromuscular diseases are a clinically heterogeneous group of disorders of children and adults in which symptoms are presumed or proven to arise as a result of neuromuscular (including interstitial cell of Cajal) dysfunction. Common to most of these diseases are symptoms of impaired motor activity which manifest as slowed or obstructed transit with or without evidence of transient or persistent radiological visceral dilatation. A variety of histopathological techniques and allied investigations are being increasingly applied to tissue biopsies from such patients. This review outlines some of the more recent advances in this field, particularly in the most contentious area of small bowel disease manifesting as intestinal pseudo-obstruction.

Voltage-gated potassium channel autoimmunity mimicking creutzfeldt-jakob disease

BACKGROUND

Rapidly progressive dementia has a variety of causes, including Creutzfeldt-Jakob disease (CJD) and neuronal voltage-gated potassium channel (VGKC) autoantibody-associated encephalopathy.

OBJECTIVE

To describe patients thought initially to have CJD but found subsequently to have immunotherapy-responsive VGKC autoimmunity.

DESIGN

Observational, prospective case series.

SETTING

Department of Neurology, Mayo Clinic, and the Memory and Aging Center, University of California, San Francisco. Patients A clinical serologic cohort of 15 patients referred for paraneoplastic autoantibody evaluation. Seven patients were evaluated clinically by at least one of us. Clinical information for the remaining patients was obtained by physician interview or medical record review.

MAIN OUTCOME MEASURES

Clinical features, magnetic resonance imaging abnormalities, electroencephalographic patterns, cerebrospinal fluid analyses, and responses to immunomodulatory therapy.

RESULTS

All the patients presented subacutely with neurologic manifestations, including rapidly progressive dementia, myoclonus, extrapyramidal dysfunction, visual hallucinations, psychiatric disturbance, and seizures; most (60%) satisfied World Health Organization diagnostic criteria for CJD. Magnetic resonance imaging abnormalities included cerebral cortical diffusion-weighted imaging hyperintensities. Electroencephalographic abnormalities included diffuse slowing, frontal intermittent rhythmic delta activity, and focal epileptogenic activity but not periodic sharp wave complexes. Cerebrospinal fluid 14-3-3 protein or neuron-specific enolase levels were elevated in 5 of 8 patients. Hyponatremia was common (60%). Neoplasia was confirmed histologically in 5 patients (33%) and was suspected in another 5. Most patients' conditions (92%) improved after immunomodulatory therapy.

CONCLUSIONS

Clinical, radiologic, electrophysiologic, and laboratory findings in VGKC autoantibody-associated encephalopathy may be confused with those of CJD. Serologic evaluation for markers of neurologic autoimmunity, including VGKC autoantibodies, may be warranted in suspected CJD cases.

Serologic profiles aiding the diagnosis of autoimmune gastrointestinal dysmotility

BACKGROUND & AIMS

Autoimmune gastrointestinal dysmotility is a limited autoimmune dysautonomia occurring idiopathically or in the context of an anatomically remote neoplasm, previously documented or unsuspected. Here we report 24 Mayo Clinic patients in whom the profile of serum autoantibodies aided this diagnosis.

METHODS

All patients were ascertained serologically in the course of service evaluation for autoantibodies consistent with neurologic autoimmunity. Review of their histories, motility studies, and laboratory findings revealed that all had presented with subacute gastrointestinal dysmotility.

RESULTS

Recorded motility abnormalities included esophageal dysmotility 8 (6 had achalasia), delayed gastric emptying 12, slow small intestinal transit 7, slow colonic transit 4, and pelvic floor dyssynergia 4. Four patients underwent abdominal surgery; 2 commenced total parenteral nutrition. Plasma membrane cation channel autoantibodies were detected in 23 patients: neuronal voltage-gated calcium channel (5 N-type and 1 P/Q-type), acetylcholine receptor (11 ganglionic-type and 4 muscle-type), and neuronal voltage-gated potassium channel autoantibodies (4). Two patients had antineuronal nuclear autoantibodies, type 1. Approximately half of the patients had neural autoantibodies (including skeletal muscle striational and glutamic acid decarboxylase, 65kd isoform) or other antibody markers of organ-specific autoimmunity (thyroid or gastric parietal cell specificities). Neoplasia was diagnosed in 11 patients (9 recent, 2 remote): lung, breast and endometrial, gastrointestinal and thymoma. Moderate to dramatic improvement in gastrointestinal symptoms was reported after immunotherapy in 4 of 4 patients treated and after pyridostigmine treatment in 2 of 2 patients treated.

CONCLUSIONS

Autoimmune serology aids the diagnosis of autoimmune gastrointestinal dysmotility, both paraneoplastic and idiopathic, and might guide management.

Autoimmune channelopathies: John Newsom-Davis's work and legacy. A summary of the Newsom-Davis Memorial Lecture 2008

John Newsom-Davis was a key figure in the field of neuroimmunology and combined many outstanding personal qualities with considerable clinical and scientific expertise. His first report of plasma exchange in myasthenia in the late 1970s demonstrated its use both as a treatment and as an experimental tool to establish the pathogenic role of antibodies in neurological disorders. Subsequent investigations into the Lambert Eaton myasthenic syndrome and acquired neuromyotonia showed that these were caused by antibodies to specific ion channels. The field of autoimmune channelopathies is continuing to expand with identification of new antibody-mediated diseases including those affecting the central nervous system. This review will highlight some of his most seminal findings and those that are following on from his work.

Calcium channels, neuromuscular synaptic transmission and neurological diseases

Voltage-dependent calcium channels are essential in neuronal signaling and synaptic transmission, and their functional alterations underlie numerous human disorders whether monogenic (e.g., ataxia, migraine, etc.) or autoimmune. We review recent work on Ca(V)2.1 or P/Q channelopathies, mostly using neuromuscular junction preparations, and focus specially on the functional hierarchy among the calcium channels recruited to mediate neurotransmitter release when Ca(V)2.1 channels are mutated or depleted. In either case, synaptic transmission is greatly compromised; evidently, none of the reported functional replacements with other calcium channels compensates fully.