The Lambert-Eaton myasthenic syndrome 1988-2008: a clinical picture in 97 patients

Burden of disease in Lambert-Eaton myasthenic syndrome: taking the patient's perspective

BACKGROUND

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune-mediated neuromuscular disorder leading to muscle weakness, autonomic dysregulation and hyporeflexia. Psychosocial well-being is affected. Previously, we assessed burden of disease for Myasthenia gravis (MG). Here, we aim to elucidate burden of disease by comparing health-related quality of life (HRQoL) of patients with LEMS to the general population (genP) as well as MG patients.

METHODS

A questionnaire-based survey included sociodemographic and clinical data along with standardized questionnaires, e.g. the Short Form Health (SF-36). HRQoL was evaluated through matched-pairs analyses. Participants from a general health survey served as control group.

RESULTS

46 LEMS patients matched by age and gender were compared to 92 controls from the genP and a matched cohort of 92 MG patients. LEMS participants showed lower levels of physical functioning (SF-36 mean 34.2 SD 28.6) compared to genP (mean 78.6 SD 21.1) and MG patients (mean 61.3 SD 31.8). LEMS patients showed lower mental health sub-scores compared to genP (SF-36 mean 62.7 SD 20.2, vs. 75.7 SD 15.1) and MG patients (SF-36 mean 62.7 SD 20.2, vs. 66.0 SD 18.). Depression, anxiety and fatigue were prevalent. Female gender, low income, lower activities of daily living, symptoms of depression, anxiety and fatigue were associated with a lower HRQoL in LEMS.

DISCUSSION

HRQoL is lower in patients with LEMS compared to genP and MG in a matched pair-analysis. The burden of LEMS includes economic and social aspects as well as emotional well-being. TRIAL REGISTRATION INFORMATION: drks.de: DRKS00024527, submitted: February 02, 2021, https://drks.de/search/en/trial/DRKS00024527 .

Paraneoplastic autonomic neuropathies and GI dysmotility

A number of the well-recognized autoimmune and paraneoplastic neurologic syndromes commonly involve the autonomic nervous system. In some cases, the autonomic nerves or ganglia are primary targets of neurologic autoimmunity, as in immune-mediated autonomic ganglionopathies. In other disorders such as encephalitis, autonomic centers in the brain may be affected. The presence of autonomic dysfunction (especially gastrointestinal dysmotility) is sometimes overlooked even though this may contribute significantly to the symptom burden in these paraneoplastic disorders. Additionally, recognition of autonomic features as part of the clinical syndrome can help point the diagnostic evaluation toward autoimmune and paraneoplastic etiologies. As with other paraneoplastic disorders, the clinical syndrome and the presence and type of neurologic autoantibodies help to secure the diagnosis and direct the most appropriate investigation for malignancy. Optimal management for these conditions typically includes aggressive treatment of the neoplasm, immunomodulatory therapy, and symptomatic treatments for orthostatic hypotension and gastrointestinal dysmotility.

Lambert-Eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disease characterized by proximal muscle weakness, loss of tendon reflexes, and autonomic dysfunction. Muscle weakness usually starts in the upper legs and can progress to oculobulbar and in severe cases respiratory muscles. P/Q-type voltage-gated calcium channels (VGCCs) localized in the presynaptic motor nerve terminal and in the autonomic nervous system are targeted by antibodies in LEMS patients. These antibodies can be detected in about 90% of patients, and the presence of decrement and increment upon repetitive nerve stimulation is also a highly sensitive diagnostic test. Rapid diagnosis is important because of the association with SCLC in 50%-60% of patients, which stresses the need for vigorous tumor screening after diagnosis. Clinical parameters can predict tumor probability and guide frequency of tumor screening. Treatment of the tumor as well as symptomatic treatment and immunosuppression can effectively control symptoms in the majority of patients.

Critical illness-associated weakness and related motor disorders

Weakness of limb and respiratory muscles that occurs in the course of critical illness has become an increasingly common and serious complication of adult and pediatric intensive care unit patients and a cause of prolonged ventilatory support, morbidity, and prolonged hospitalization. Two motor disorders that occur singly or together, namely critical illness polyneuropathy and critical illness myopathy, cause weakness of limb and of breathing muscles, making it difficult to be weaned from ventilatory support, commencing rehabilitation, and extending the length of stay in the intensive care unit, with higher rates of morbidity and mortality. Recovery can take weeks or months and in severe cases, and may be incomplete or absent. Recent findings suggest an improved prognosis of critical illness myopathy compared to polyneuropathy. Prevention and treatment are therefore very important. Its management requires an integrated team approach commencing with neurologic consultation, creatine kinase (CK) measurement, detailed electrodiagnostic, respiratory and neuroimaging studies, and potentially muscle biopsy to elucidate the etiopathogenesis of the weakness in the peripheral and/or central nervous system, for which there may be a variety of causes. These tenets of care are being applied to new cases and survivors of the coronavirus-2 disease pandemic of 2019. This chapter provides an update to the understanding and approach to critical illness motor disorders.

Paraneoplastic motor disorders

Paraneoplastic neurological disorders (PNDs) are heterogeneous clinicopathologic syndromes that occur throughout the neuraxis resulting from damage to organs or tissues remote from the site of a malignant neoplasm or its metastases. The discordance between severe neurological disability and even an indolent malignancy suggests an underlying neuroimmunologic host immune response that inflicts nervous tissue damage while inhibiting malignant tumor growth. Motor system involvement, like other symptoms and signs, is associated with focal or diffuse involvement of the brain, spinal cord, peripheral nerve, neuromuscular junction or muscle, alone or in combination due to an underlying neuroimmune and neuroinflammatory process targeting neural-specific antigens. Unrecognized and therefore untreated, PNDs are often lethal making early detection and aggressive treatment of paramount importance. While the combination of clinical symptoms and signs, and analysis of detailed body and neuroimaging, clinical neurophysiology and electrodiagnostic studies, and tumor and nervous system tissue biopsies are all vitally important, the certain diagnosis of a PND rests with the discovery of a corresponding neural-specific paraneoplastic autoantibody in the blood and/or spinal cerebrospinal fluid.

Nationwide survey of Lambert-Eaton myasthenic syndrome in Japan

Background

There was no nationwide epidemiological study of Lambert-Eaton myasthenic syndrome (LEMS) in Japan; therefore, we conducted a nationwide survey.

Methods

For the first survey, we sent survey sheets to randomly selected medical departments (n=7545) to obtain the number of LEMS who visited medical departments between 1 January 2017 and 31 December 2017. For the second survey, we sent survey sheets to the corresponding medical departments to obtain clinical information on LEMS.

Results

We received 2708 responses (recovery rate: 35.9%) to the first survey. We estimated the number of LEMS as 348 (95% CI 247 to 449). The prevalence was 2.7 (95% CI 1.9 to 3.5) in 1 000 000 population. As a result of the second survey, we obtained 30 case records of 16 men and 14 women. Fourteen patients (46.7%) had a tumour, and 10 out of 14 tumours were small-cell lung carcinoma (71.4%). There was a predominance of men in the LEMS with tumour (paraneoplastic LEMS, P-LEMS) (n=11, 78.6%) and women in the LEMS without tumour (a primary autoimmune form of LEMS, AI-LEMS) (n=11, 68.8%) (p=0.0136). The onset age (mean (SD)) for the P-LEMS was 67.1 (9.0), and that for AI-LEMS was 57.8 (11.2) years old (p=0.0103). The disease duration (median) for P-LEMS was 2 years, and for AI-LEMS was 7.5 years (p=0.0134).

Conclusions

The prevalence of LEMS in Japan is similar to that in other countries. There are predominances of men in P-LEMS and women in AI-LEMS.

Neurological Adverse Events Induced by Immune Checkpoint Inhibitors in Non-Small Cell Lung Cancer: Current Perspectives and New Development

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of multiple malignancies, especially in non-small cell lung cancer (NSCLC). With the extensive application of ICIs in clinical practice, clinicians have to manage their toxicities, which are often termed immune-related adverse events (irAEs). Several ICIs, such as nivolumab, pembrolizumab, atezolizumab, and durvalumab, have been approved by the US Food and Drug Administration (FDA) to treat advanced NSCLC, accompanied by a broad spectrum of toxicity reactions. However, ICIs-associated neurological toxicities, regarding polyneuropathy, Bell palsy, encephalopathy, and myasthenia gravis, as uncommon emerging toxicities have not been well recognized, present a challenge for clinicians to improve awareness of supervision, recognition, and management before death from them. Herein, we have summarized the incidence, diagnosis, clinical manifestations, potential mechanisms, treatments, and outcomes of ICIs-related neurotoxicity and optimized the management approach for NSCLC patients. Prompt recognition and proper management are indispensable to reduce the morbidity of these patients with immune-related neurological toxicities.

Paraneoplastic ocular syndrome: a pandora's box of underlying malignancies

Paraneoplastic syndromes affecting the visual system are a group of conditions that arise in the systemic malignancy framework. In this review, we have provided a detailed and comprehensive overview of the published literature on the various ophthalmic paraneoplastic manifestations. A systematic review of many databases has been performed to identify ample literature on the paraneoplastic syndromes related to ophthalmology. We have discussed here the clinical features, pathogenesis, and treatment strategies of various ophthalmic paraneoplastic syndromes. It can be challenging to distinguish these disorders from their non-paraneoplastic counterparts and to determine the appropriate systemic assessment for the tumour responsible, to have a proper approach towards the management of the syndrome. METHOD: We searched PubMed, Science Direct and Journal of Ophthalmology for studies published in English between 1995 and April 2020, incorporating the general search term "paraneoplastic ocular syndrome" with connecting terms relevant to subheadings-e.g. Key search terms were cancer-associated retinopathy, (CAR), melanoma-associated retinopathy, (MAR), paraneoplastic retinopathy, autoimmune retinopathy, autoimmune-related retinopathy, and optic neuropathy, (ARRON), acute zonal occult outer retinopathy, (AZOOR), paraneoplastic vitelliform maculopathy, paraneoplastic vitelliform retinopathy, bilateral diffuse uveal melanocytic proliferation, (BDUMP), paraneoplastic optic neuropathy, (PON), polyneuropathy, organomegaly, endocrinopathy, monoclona gammopathy, and skin changes syndrome (POEMS) and various other terms. References from identified studies have been reviewed and included if deemed appropriate, valid, and scientifically important. If referenced in a selected English paper, we contemplated papers in other languages too. We preferentially selected papers that have been published in the last 10 years, but we have included relevant older references.

Presynaptic Paraneoplastic Disorders of the Neuromuscular Junction: An Update

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

Paraneoplastic Cerebellar Degeneration and Lambert-Eaton Myasthenic Syndrome with SOX-1 Antibodies

A 69-year-old man was admitted to our hospital for progressive muscle weakness in both lower limbs and limb ataxia (day 0). Nerve conduction studies showed low compound muscle action potential amplitudes at rest and increased amplitudes after maximum voluntary contraction. Blood testing revealed SOX-1 antibodies. He was diagnosed with paraneoplastic cerebellar degeneration and Lambert-Eaton myasthenic syndrome (PCD-LEMS). He died from aspiration pneumonia on day 9. Small-cell lung carcinoma (SCLC), which had not been obvious on computed tomography, was found during the autopsy. Patients with PCD-LEMS who test positive for SOX-1 antibodies should be carefully evaluated for SCLC.

Autoimmune Autonomic Disorders

PURPOSE OF REVIEW

Autonomic disorders sometimes occur in the context of systemic autoimmune disease or as a direct consequence of autoimmunity against the nervous system. This article provides an overview of autonomic disorders with potential autoimmune etiology.

RECENT FINDINGS

Recent evidence highlights a close association between the autonomic nervous system and inflammation. The autonomic nervous system regulates immune function, and autonomic manifestations may occur in a number of systemic autoimmune diseases. In a few instances, autoimmunity directly influences autonomic function. Autoimmune autonomic ganglionopathy is the prototypic antibody-mediated autonomic disorder. Over time, a better understanding of the clinical spectrum of autoimmune autonomic ganglionopathy, the significance of ganglionic nicotinic acetylcholine receptor antibodies, other immune-mediated autonomic neuropathies, and autonomic manifestations of other systemic or neurologic autoimmune disorders has emerged.

SUMMARY

Autoimmune autonomic disorders may be challenging, but correct identification of these conditions is important. In some cases, potential exists for effective immunomodulatory treatment.

Long-term follow-up, quality of life, and survival of patients with Lambert-Eaton myasthenic syndrome

Objective

To study survival and to characterize long-term functional impairments and health-related quality of life (HRQOL) of patients with Lambert-Eaton myasthenic syndrome (LEMS).

Methods

In this observational study, survival of patients with LEMS, separately for nontumor (NT) and small cell lung cancer (SCLC), was compared to that of the Dutch general population and patients with SCLC. Disease course in patients with LEMS was recorded retrospectively. Several scales for functional impairments and health-related quality of life were assessed.

Results

We included 150 patients with LEMS. Survival was similar to that of the general population in 65 patients with NT-LEMS. Tumor survival was significantly longer in 81 patients with SCLC-LEMS compared to patients with non-LEMS SCLC (overall median survival 17 vs 7.0 months, p < 0.0001). At diagnosis, 39 (62%) of 63 patients with complete follow-up data were independent for activities of daily living, improving to 85% at the 1-year follow-up. The physical HRQOL composite score (55.9) was significantly lower than in the general population (76.3, p < 0.0001) and comparable to that of patients with myasthenia gravis (60.5). The mental HRQOL composite score was 71.8 in patients with LEMS, comparable to that of the general population (77.9, p = 0.19) and patients with myasthenia gravis (70.3).

Conclusions

This study shows that patients with NT-LEMS have normal survival. Patients with SCLC-LEMS have an improved tumor survival, even after correction for tumor stage. A majority of patients with LEMS report a stable disease course and remain or become independent for self-care after treatment.

Lambert-Eaton Myasthenic Syndrome

Lambert-Eaton myasthenic syndrome is a paraneoplastic or primary autoimmune neuromuscular junction disorder characterized by proximal weakness, autonomic dysfunction and ariflexia. The characteristic symptoms are thought to be caused by antibodies generated against the P/Q-type voltage-gated calcium channels present on presynaptic nerve terminals and by diminished release of acetylcholine. More than half of Lambert-Eaton myasthenic syndrome cases are associated with small cell lung carcinoma. Diagnosis is confirmed by serologic testing and electrophysiologic studies. 3,4-diaminopyridine is effective symptomatic treatment of LEMS.

Recent Advances and Therapeutic Options in Lambert-Eaton Myasthenic Syndrome

Lambert-Eaton Myasthenic Syndrome (LEMS) is an autoimmune-mediated neurological disorder that manifests as muscle fatigue, diminished tendon reflexes, with symptoms of cholinergic overactivity. It can be associated with certain neoplastic conditions, the most common being small cell lung carcinoma (SCLC). The basic pathophysiology involved is antibody-mediated targeting of voltage-gated calcium channels (VGCC), which decreases the release of acetylcholine in the synaptic junction. Multiple treatment options have been introduced in the past and, recently, a new drug, amifampridine, has been approved by the Food and Drug Administration (FDA) for the treatment of weakness associated with these patients. We summarize this newly introduced drug with a brief description of other treatment options available.

Autoimmune Channelopathies at Neuromuscular Junction

The neuromuscular junction, also called myoneural junction, is a site of chemical communication between a nerve fiber and a muscle cell. There are many types of channels at neuromuscular junction that play indispensable roles in neuromuscular signal transmission, such as voltage-gated calcium channels and voltage-gated potassium channels on presynaptic membrane, and acetylcholine receptors on post-synaptic membrane. Over the last two decades, our understanding of the role that autoantibodies play in neuromuscular junction disorders has been greatly improved. Antibodies against these channels cause a heterogeneous group of diseases, such as Lambert-Eaton syndrome, Isaacs' syndrome and myasthenia gravis. Lambert-Eaton syndrome is characterized by late onset of fatigue, skeletal muscle weakness, and autonomic symptoms. Patients with Isaacs' syndrome demonstrate muscle cramps and fasciculation. Myasthenia gravis is the most common autoimmune neuromuscular junction channelopathy characterized by fluctuation of muscle weakness. All these disorders have a high risk of tumor. Although these channelopathies share some common features, they differ for clinical features, antibodies profile, neurophysiological features, and treatments. The purpose of this review is to give a comprehensive insight on recent advances in autoimmune channelopathies at the neuromuscular junction.

Lambert-Eaton Myasthenic syndrome: early diagnosis is key

Lambert-Eaton myasthenic syndrome (LEMS) is an uncommon disorder of neuromuscular transmission with distinctive pathophysiological, clinical, electrophysiological and laboratory features. There are two forms of LEMS. The paraneoplastic (P-LEMS) form is associated with a malignant tumor that is most frequently a small cell lung carcinoma (SCLC), and the autoimmune (A-LEMS) form is often related to other dysimmune diseases. Approximately 90% of LEMS patients present antibodies against presynaptic membrane P/Q-type voltage-gated calcium channels (VGCC). These antibodies are directly implicated in the pathophysiology of the disorder, provoke reduced acetylcholine (ACh) at the nerve terminal and consequently lead to muscle weakness. LEMS is clinically characterized by proximal muscle weakness, autonomic dysfunction and areflexia. In clinically suspected cases, diagnoses are confirmed by serological and electrodiagnostic tests. The detection of P/Q-type VGCC antibodies is supportive when there is clinical suspicion but should be carefully interpreted in the absence of characteristic clinical or electrodiagnostic features. Typical electrodiagnostic findings (ie, reduced compound motor action potentials (CMAPs), significant decrements in the responses to low frequency stimulation and incremental responses after brief exercise or high-frequency stimulation) reflect the existence of a presynaptic transmission defect and are key confirmatory criteria. Diagnosis requires a high level of awareness and necessitates the initiation of a prompt screening and surveillance process to detect and treat malignant tumors. In clinically affected patients without cancer and after cancer treatment, symptomatic treatment with 3,4-diaminopyridine or immunosuppressive agents can significantly improve neurologic symptoms and the quality of life. We present a detailed review of LEMS with special emphasis on the pathophysiological mechanisms, clinical manifestation and diagnostic procedure.

Clinical characteristics and long term follow-up of Lambert-Eaton myasthenia syndrome in patients with and without small cell lung cancer

In order to describe the clinical characteristics, treatment response and long-term follow up in Lambert-Eaton myasthenic syndrome (LEMS) patients with and without small cell lung cancer (SCLC) in East China, patients seen in Huashan Hospital from January 1997 to December 2017 were included. Clinical information was collected retrospectively and quantitative MG (QMG) score, manual muscle testing (MMT), activities of daily living (ADL) scale were evaluated when the patients were followed up. Of 50 patients, 23 (46%) were SCLC-LEMS and 20 (40%) were nontumor LEMS (NT-LEMS). The median onset age was 55.5 (18-86) years old and the gender ratio was about 1.8:1. It took less time to make the diagnosis (median time: 6 vs 22.5 months, p = 0.0003) and there were more patients with other paraneoplastic syndromes in SCLC-LEMS group than in NT-LEMS group (8/23 vs 0/20, p = 0.0042). Electrophysiologically, the peroneal compound motor action potential (CMAP) of rest showed difference between SCLC-LEMS and NT-LEMS (0.8 vs 1.6 mV, p = 0.0499). The median survival time of 19 SCLC-LEMS patients since the diagnosis of SCLC was 30 months. According to their survival time, SCLC patients with LEMS showed a more favorable prognosis than those without LEMS. In the time of follow-up, most NT-LEMS showed improvement or obtained status of CSR/PR/MM after immunosuppressive therapy and no significant difference in proportion of achieving CSR/PR/MM was found between SCLC-LEMS and NT-LEMS patients (0/5 vs 6/13, p = 0.114).

Myasthenia Gravis and Lambert-Eaton Myasthenic Syndrome

PURPOSE OF REVIEW

This article discusses the pathogenesis, diagnosis, and management of autoimmune myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS).

RECENT FINDINGS

Recognition of new antigenic targets and improved diagnostic methods promise to improve the diagnosis of MG, although the clinical phenotypes associated with newer antibodies have not yet been defined. Future therapies might specifically target the aberrant immune response. The apparent increase in the prevalence of MG is not fully explained. Results of a long-awaited trial of thymectomy support the practice of performing a thymectomy under specific conditions.

SUMMARY

The current treatment options are so effective in most patients with MG or LEMS that in patients with refractory disease the diagnosis should be reconsidered. The management of MG is individualized, and familiarity with mechanisms, adverse effects, and strategies to manage these commonly used treatments improves outcome. Patient education is important. LEMS, frequently associated with an underlying small cell lung cancer, is uncommon, and the mainstay of treatment is symptomatic in most patients.

Population Pharmacokinetics/Pharmacodynamics of 3,4-Diaminopyridine Free Base in Patients With Lambert-Eaton Myasthenia

Lambert-Eaton myasthenia (LEM) is a rare autoimmune disorder associated with debilitating muscle weakness. There are limited treatment options and 3,4-diaminopyridine (3,4-DAP) free base is an investigational orphan drug used to treat LEM-related weakness. We performed a population pharmacokinetic/pharmacodynamic (PK/PD) analysis using 3,4-DAP and metabolite concentrations collected from a phase II study in patients with LEM. The Triple Timed Up & Go (3TUG) assessment, which measures lower extremity weakness, was the primary outcome measure. A total of 1,270 PK samples (49 patients) and 1,091 3TUG data points (32 randomized patients) were included in the PK/PD analysis. A two-compartment and one-compartment model for parent and metabolite, respectively, described the PK data well. Body weight and serum creatinine partially explained the variability in clearance for the final PK model. A fractional inhibitory maximum effect (Emax ) model characterized the exposure-response relationship well. The PK/PD model was applied to identify a suggested dosing approach for 3,4-DAP free base.

Autoimmune paraneoplastic syndromes associated to lung cancer: A systematic review of the literature Part 4: Neurological paraneoplastic syndromes, involving the peripheral nervous system and the neuromuscular junction and muscles

The development of new immune treatment in oncology and particularly for lung cancer may induce new complications, particularly activation or reactivation of auto-immune diseases. In this context, a systematic review on the auto-immune paraneoplastic syndromes that can complicate lung cancer appears useful. This article is the fourth of a series of five and deals mainly with neurological paraneoplastic syndromes involving the peripheral nervous system and the neuromuscular junction and muscles.

Ophthalmoplegia associated with lung adenocarcinoma in a patient with the Lambert-Eaton myasthenic syndrome: A case report

RATIONALE

The Lambert-Eaton myasthenic syndrome (LEMS) is a neuromuscular disease; its unique symptoms of LEMS include dry mouth with a metallic taste, constipation, and erectile dysfunction. As it is quite rare, isolated ocular muscle impairment associated with LEMS east to ignore.

PATIENT CONCERNS

A 65-year-old man presented with alternating ptosis and diplopia. Isolated ocular muscle impairment had lasted for 6 years, and the patient was initially diagnosed with ocular myasthenia gravis (MG). Treatment with azathioprine only slightly improved symptoms over the first 2 months; long-term treatment was not effective.

DIAGNOSES

Dynamic observation of chest computed tomography images revealed a slowly progressing nodule in the lower lobe of the left lung. The subsequent pathologic examination following mass resection confirmed a diagnosis of lung adenocarcinoma.

INTERVENTIONS

The patient was ultimately diagnosed with the Lambert-Eaton myasthenic syndrome associated with pulmonary adenocarcinoma.

OUTCOMES

Resection of the lung tumor relieved all symptoms.

LESSONS

Other causes of ocular MG symptoms should be considered when standard MG therapy is ineffective, especially the Lambert-Eaton myasthenic syndrome.

The role of laminins in the organization and function of neuromuscular junctions

The synapse between motor neurons and skeletal muscle is known as the neuromuscular junction (NMJ). Proper alignment of presynaptic and post-synaptic structures of motor neurons and muscle fibers, respectively, is essential for efficient motor control of skeletal muscles. The synaptic cleft between these two cells is filled with basal lamina. Laminins are heterotrimer extracellular matrix molecules that are key members of the basal lamina. Laminin α4, α5, and β2 chains specifically localize to NMJs, and these laminin isoforms play a critical role in maintenance of NMJs and organization of synaptic vesicle release sites known as active zones. These individual laminin chains exert their role in organizing NMJs by binding to their receptors including integrins, dystroglycan, and voltage-gated calcium channels (VGCCs). Disruption of these laminins or the laminin-receptor interaction occurs in neuromuscular diseases including Pierson syndrome and Lambert-Eaton myasthenic syndrome (LEMS). Interventions to maintain proper level of laminins and their receptor interactions may be insightful in treating neuromuscular diseases and aging related degeneration of NMJs.

Mapping autoantigen epitopes: molecular insights into autoantibody-associated disorders of the nervous system

Background

Our knowledge of autoantibody-associated diseases of the central (CNS) and peripheral (PNS) nervous systems has expanded greatly over the recent years. A number of extracellular and intracellular autoantigens have been identified, and there is no doubt that this field will continue to expand as more autoantigens are discovered as a result of improved clinical awareness and methodological practice. In recent years, interest has shifted to uncover the target epitopes of these autoantibodies.

Main body

The purpose of this review is to discuss the mapping of the epitope targets of autoantibodies in CNS and PNS antibody-mediated disorders, such as N-methyl-D-aspartate receptor (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), leucine-rich glioma-inactivated protein 1 (Lgi1), contactin-associated protein-like 2 (Caspr2), myelin oligodendrocyte glycoprotein (MOG), aquaporin-4 (AQP4), 65 kDa glutamic acid decarboxylase (GAD65), acetylcholine receptor (AChR), muscle-specific kinase (MuSK), voltage-gated calcium channel (VGCC), neurofascin (NF), and contactin. We also address the methods used to analyze these epitopes, the relevance of their determination, and how this knowledge can inform studies on autoantibody pathogenicity. Furthermore, we discuss triggers of autoimmunity, such as molecular mimicry, ectopic antigen expression, epitope spreading, and potential mechanisms for the rising number of double autoantibody-positive patients.

Conclusions

Molecular insights into specificity and role of autoantibodies will likely improve diagnosis and treatment of CNS and PNS neuroimmune diseases.

Case report of severe Cushing's syndrome in medullary thyroid cancer complicated by functional diabetes insipidus, aortic dissection, jejunal intussusception, and paraneoplastic dysautonomia: remission with sorafenib without reduction in cortisol concentration

Background

Normalization of cortisol concentration by multikinase inhibitors have been reported in three patients with medullary thyroid cancer-related Cushing’s syndrome. Aortic dissection has been reported in three patients with Cushing’s syndrome. Diabetes insipidus without intrasellar metastasis, intestinal intussusception, and paraneoplastic dysautonomia have not been reported in medullary thyroid cancer.

Case presentation

An adult male with metastatic medullary thyroid cancer presented with hyperglycemia, hypernatremia, hypokalemia, hypertension, acne-like rash, and diabetes insipidus (urine volume >8 L/d, osmolality 190 mOsm/kg). Serum cortisol, adrenocorticoitropic hormone, dehydroepiandrostenedione sulfate, and urinary free cortisol were elevated 8, 20, 4.4, and 340 folds, respectively. Pituitary imaging was normal. Computed tomography scan revealed jejunal intussusception and incidental abdominal aortic dissection. Sorafenib treatment was associated with Cushing’s syndrome remission, elevated progesterone (>10 fold), normalization of dehydroepiandrostenedione sulfate, but persistently elevated cortisol concentration. Newly-developed proximal lower limb weakness and decreased salivation were associated with elevated ganglionic neuronal acetylcholine receptor (alpha-3) and borderline P/Q type calcium channel antibodies.

Conclusion

Extreme cortisol concentration may have contributed to aortic dissection and suppressed antidiuretic hormone secretion; which combined with hypokalemia due cortisol activation of mineralocorticoid receptors, manifested as diabetes insipidus. This is the first report of paraneoplastic dysautonomia and jejunal intussusception in medullary thyroid cancer, they may be related to medullary thyroid cancer’s neuroendocrine origin and metastasis, respectively. Remission of Cushing’s syndrome without measurable reduction in cortisol concentration suggests a novel cortisol-independent mechanism of action or assay cross-reactivity. Normalization of dehydroepiandrostenedione sulfate and elevation of progesterone suggest inhibition of 17-hydroxylase and 21-hydroxylase activities by sorafenib.

Long-term follow-up in infantile-onset lambert-eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome is a neuromuscular junction disorder characterized by proximal limb muscle weakness, fatigability, decreased deep-tendon reflexes, and autonomic symptoms. There are 2 forms of Lambert-Eaton myasthenic syndrome: one most frequently associated with small-cell lung cancer (P-Lambert-Eaton myasthenic syndrome) and the other that is a pure autoimmune form (NP-Lambert-Eaton myasthenic syndrome). Lambert-Eaton myasthenic syndrome is a very rare disorder in children younger than age 12 years. Herein, we report a 25-year-old man with NP-Lambert-Eaton myasthenic syndrome, which onset was at the age of 10 years. To date, this is the most long-term follow-up of NP-Lambert-Eaton myasthenic syndrome in childhood. In our patient, the only symptomatic treatment with 3,4-diaminopyridine phosphate has been sufficient to guarantee him a good quality of life. Our data remind physicians to keep in mind the diagnosis of Lambert-Eaton myasthenic syndrome in children with a proximal myopathic pattern and they confirm the specificity of compound muscle action potential incremental pattern after brief maximal effort in Lambert-Eaton myasthenic syndrome.

Paraneoplastic syndromes associated with lung cancer

Paraneoplastic syndromes are signs or symptoms that occur as a result of organ or tissue damage at locations remote from the site of the primary tumor or metastases. Paraneoplastic syndromes associated with lung cancer can impair various organ functions and include neurologic, endocrine, dermatologic, rheumatologic, hematologic, and ophthalmological syndromes, as well as glomerulopathy and coagulopathy (Trousseau’s syndrome). The histological type of lung cancer is generally dependent on the associated syndrome, the two most common of which are humoral hypercalcemia of malignancy in squamous cell carcinoma and the syndrome of inappropriate antidiuretic hormone secretion in small cell lung cancer. The symptoms often precede the diagnosis of the associated lung cancer, especially when the symptoms are neurologic or dermatologic. The proposed mechanisms of paraneoplastic processes include the aberrant release of humoral mediators, such as hormones and hormone-like peptides, cytokines, and antibodies. Treating the underlying cancer is generally the most effective therapy for paraneoplastic syndromes, and treatment soon after symptom onset appears to offer the best potential for symptom improvement. In this article, we review the diagnosis, potential mechanisms, and treatments of a wide variety of paraneoplastic syndromes associated with lung cancer.

Complete reversal of Lambert-Eaton myasthenic syndrome synaptic impairment by the combined use of a K+ channel blocker and a Ca2+ channel agonist

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder in which a significant fraction of the presynaptic P/Q-type Ca(2+) channels critical to the triggering of neurotransmitter release at the neuromuscular junction (NMJ) are thought to be removed. There is no cure for LEMS, and the current most commonly used symptomatic treatment option is a potassium channel blocker [3,4-diaminopyridine (3,4-DAP)] that does not completely reverse symptoms and can have dose-limiting side-effects. We previously reported the development of a novel Ca(2+) channel agonist, GV-58, as a possible alternative treatment strategy for LEMS. In this study, we tested the hypothesis that the combination of GV-58 and 3,4-DAP will elicit a supra-additive increase in neurotransmitter release at LEMS model NMJs. First, we tested GV-58 in a cell survival assay to assess potential effects on cyclin-dependent kinases (Cdks) and showed that GV-58 did not affect cell survival at the relevant concentrations for Ca(2+) channel effects. Then, we examined the voltage dependence of GV-58 effects on Ca(2+) channels using patch clamp techniques; this showed the effects of GV-58 to be dependent upon Ca(2+) channel opening. Based on this mechanism, we predicted an interaction between 3,4-DAP and GV-58. We tested this hypothesis using a mouse passive transfer model of LEMS. Using intracellular electrophysiological ex vivo recordings, we demonstrated that a combined application of 3,4-DAP plus GV-58 had a supra-additive effect that completely reversed the deficit in neurotransmitter release magnitude at LEMS model NMJs. This reversal contrasts with the less significant improvement observed with either compound alone. Our data indicate that a combination of 3,4-DAP and GV-58 represents a promising treatment option for LEMS and potentially for other disorders of the NMJ.

Pathogenic immune mechanisms at the neuromuscular synapse: the role of specific antibody-binding epitopes in myasthenia gravis

Autoantibodies against three different postsynaptic antigens and one presynaptic antigen at the neuromuscular junction are known to cause myasthenic syndromes. The mechanisms by which these antibodies cause muscle weakness vary from antigenic modulation and complement-mediated membrane damage to inhibition of endogenous ligand binding and blocking of essential protein-protein interactions. These mechanisms are related to the autoantibody titre, specific epitopes on the target proteins and IgG autoantibody subclass. We here review the role of specific autoantibody-binding epitopes in myasthenia gravis, their possible relevance to the pathophysiology of the disease and potential implications of epitope mapping knowledge for new therapeutic strategies.

The association between Lambert-Eaton myasthenic syndrome and small cell lung carcinoma

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder mediated by autoantibodies to voltage-gated calcium channels. The disorder is diagnosed clinically on the basis of a triad of symptoms (proximal muscle weakness, hyporeflexia, and autonomic disturbance), supported by electrophysiological findings and the presence of autoantibodies. Between 40% and 62% of patients diagnosed with LEMS are found to have small-cell lung cancer (SCLC), almost all of whom develop neurological symptoms before their cancer is diagnosed. Prompt identification of LEMS and appropriate screening for SCLC is key to improving the outcome of both conditions. Here we review the pathophysiology and clinical management of LEMS, focusing particularly on the relationship with SCLC.

[Synchronous appearance and improvement with anticancer chemotherapy of paraneoplastic cerebellar degeneration and Lambert-Eaton myasthenic syndrome complicated with small cell lung cancer]

A 62-year-old man who had suffered from instability of gait and double vision for two months was admitted to our hospital because of weakness of the extremities and ataxia of the extremities and trunk. Chest X-rays and CT scans showed enlargement of the left hilar lymph nodes and a nodular shadow in the left lung. Transbronchial biopsy revealed small cell lung cancer. We diagnosed the patient with two conditions: paraneoplastic cerebellar degeneration (PCD), based on cerebellar ataxia, the presence of Hu antineuronal antibodies, and the absence of cerebellar atrophy and malignancy; and Lambert-Eaton myasthenic syndrome (LEMS), based on weakness of the extremities, the presence of P/Q-type voltage-gated calcium channel antibodies, and waxing in the evoked electromyogram. Anticancer chemoradiation therapy that was started within three months of symptom onset resulted in reductions in size of the hilar lymph nodes and the nodule. Concurrently, cerebellar ataxia, weakness of the extremities, and double vision all disappeared. Anticancer chemotherapy is effective against LEMS while usually less effective against PCD. Early commencement of anticancer chemotherapy is recommended for the treatment of PCD with LEMS.

SOX1 antibodies in Lambert-Eaton myasthenic syndrome and screening for small cell lung carcinoma

Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of the neuromuscular synapse. About half of LEMS patients have an associated small cell lung carcinoma (SCLC), which is usually detected after diagnosis of LEMS. This short review summarizes clinical and serological markers shown to predict the presence of SCLC in LEMS patients. SOX1 antibodies are a specific marker for SCLC-LEMS but they are also found in SCLC patients without paraneoplastic neurological syndromes. No relation to any clinical characteristic or survival effect has been found for SOX1-positive patients. Several clinical markers also discriminate between SCLC-LEMS and nontumor LEMS. Detailed analysis of these clinical and demographic characteristics from two independent patient cohorts has led to development of the DELTA-P score. This prediction model has provided for a simple clinical tool to indicate the presence of SCLC early in the course of the disease. The DELTA-P score can be used to guide tumor screening in individual patients.

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.

Long-term disease history, clinical symptoms, health status, and healthcare utilization in patients suffering from Lambert Eaton myasthenic syndrome: Results of a patient interview survey in Germany

INTRODUCTION

The burden of disease in Lambert-Eaton myasthenic syndrome (LEMS) patients is unclear. This study focused on the patient's perspective to obtain patient-reported information on clinical symptoms, burden of illness, impact of LEMS on activities of daily living (ADL), and management of LEMS.

METHODS

Semi-structured, face-to-face interviews with LEMS patients from two specialized centres in Germany between September and December 2010.

RESULTS

Twelve patients participated; mean age 66.7 ± 9.8 years. First symptoms occurred at age 52.5 ± 14.0 years. Mean time between first symptoms and diagnosis was 4.4 ± 6.2 years. Patients reported neuromuscular, cranial, and autonomic symptoms plus general fatigue. Two-thirds of patients reported 10 or more symptoms. The most frequent symptoms were leg weakness (91.7%) and general fatigue (83.3%). Restrictions in ADL were reported always or often in 75% of patients. Over half of the patients (n = 7) reported poor or very poor health status. Mean EQ-5D utility scores were 0.34 ± 0.35, with little day-to-day variation. Patients visited a number of different clinicians; most had been hospitalized at some point in the course of their disease. The most frequent drug treatments were 3,4-diaminopyridine (3,4-DAP) (83.3%) and pyridostigmine (41.5%). The study has several limitations, including small sample size and the potential influence of recall bias.

CONCLUSION

LEMS patients report long individual disease histories. Most patients suffer multiple symptoms which are frequently severe and troublesome, and almost all are restricted in ADL with poor health status. There is high utilization of healthcare resources from diagnosis to ongoing treatment. Physicians should be aware of this rare disease to ensure that patients receive an early diagnosis and prompt and appropriate treatment.

Immunological markers in neurological disorders

Neurological dysfunction results from vascular, inflammatory, degenerative, neoplastic, metabolic or genetic causes. Of particular interest is a group of neurological symptoms thought to be linked to an underlying tumour, the so-called paraneoplastic syndromes. It is considered to be due to an attempt by the immune system to subjugate the growth of the tumour by triggering an antibody response against the neuronal antigens expressed by the neoplasm. The unfortunate consequence of this is an assault by the immune components on the nervous tissue, thereby rapidly precipitating a variety of neurological deficits. Every level of the nervous system is potentially vulnerable, with the disability being considered as irreversible due to the lack of regenerative capacity of the neurons. This phenomenon is rare, occurring at an approximate frequency of less than 1% of all tumours and often accompanied by the presence of specific high-titre autoantibodies in both the cerebrospinal fluid and blood. This group of antibodies are non-pathogenic markers for paraneoplastic neurological syndromes, which have expanded to almost 20 since the discovery, in 1986, of the first clinically relevant syndrome. More recently, a new generation of antineuronal antibodies against cell surface antigens, having a direct pathogenic role in causing the disease, has emerged to complement the existing repertoire. Neuronal antibodies are useful diagnostic markers of the brain disease and also, in some cases, may reveal an underlying malignancy, thus facilitating faster diagnosis and earlier treatment with consequently better prognosis.