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Highlight: • LEMS is a rare neurological disease with fluctuating symptoms • Delays and misdiagnosis of LEMS disease often occur • The two main pathophysiologies of LEMS are autoimmune and paraneoplastic. ABSTRACT A rare condition known as Lambert-Eaton myasthenic syndrome (LEMS) affects the neuromuscular junctions, which are the connections between muscles and nerves. Tumor-associated or autoimmune causes trigger this condition. This mechanism depends on the presence of antibodies that directly attach to voltage-gated calcium channels located on the presynaptic nerve terminals. LEMS disease is divided into non-paraneoplastic or non-tumor LEMS (NT-LEMS) and paraneoplastic LEMS (P-LEMS). NT-LEMS is believed to be caused by an autoimmune process. On the other hand, P-LEMS has an underlying tumor, and LEMS symptoms are paraneoplastic manifestations of the tumor. Clinical signs of LEMS include proximal muscle weakness, autonomic dysfunction, and decreased deep tendon reflexes. The predominant sign of LEMS is weakness of the lower extremities. The defining characteristic of LEMS is a weakness that spreads from caudal to cranial, causing oculobulbar manifestations, and from proximal to distal, potentially involving the feet and hands. The diagnosis of LEMS depends on clinical, electromyographic, and serological findings of anti-VGCC antibodies. Therefore, comprehensive oncologic screening and monitoring should promptly follow a diagnosis of LEMS. The standard approach to treating LEMS symptoms is administering drugs that improve neurotransmission, such as potassium channel blockers and amifampridine. In refractory cases, immunosuppressants or immunomodulator agents, such as a combination of prednisone and azathioprine, are used. If a tumor is detected, oncological therapy should be a priority.

Abstract This is an unusual case of voltage gated calcium channel (VGCC) antibodies leading to two distinct and chronologically separated neurologic syndromes without the presence of an underlying neoplasm. Lambert Eaton Myasthenic Syndrome (LEMS) presented five years prior to cerebellar ataxia. Both LEMS and cerebellar ataxia were responsive to treatment, but not the same therapy. He was diagnosed with LEMS through history, exam, electromyography/nerve conduction studies (EMG/NCS) with repetitive nerve stimulation (RNS) and antibody testing. He was treated with 3,4 diaminopyridine (3,4 DAP) with an excellent response. Five years later, he developed acute ataxia. The patient required months of intensive and continued immunomodulating therapy.

Objective To summarize the electrophysiological and muscle pathological characteristics of Lambert - Eaton myasthenic syndrome (LEMS). Methods and Results Twelve LEMS patients referred to China - Japan Friendship Hospital between January 2010 and December 2021 were included. Clinically, they all showed proximal muscle weakness and reduced or disappeared tendon reflexes. Electrophysiologically, all 12 patients showed decreased compound muscle action potential (CMAP) amplitudes, normal distal motor latency (DML), and normal motor and sensory conduction velocities. Ten patients underwent repetitive nerve stimulation (RNS) test: all had amplitude increments of more than 100% at high - frequency RNS, and 8 had amplitude decrements of more than 15% at low - frequency RNS. Three patients completed the post-exercise facilitation (PEF) test: the ulnar nerve CMAP amplitude reached a peak immediately after maximum voluntary contraction of the abductor digiti minimi for 5-10 s and then gradually decreased to near baseline level after contraction for 60 s; the ulnar nerve CMAP amplitude reached a peak immediately after maximum voluntary contraction for 10 s, and then rapidly decreased to near baseline level after 15 s. On needle EMG, 8 patients showed normal motor unit action potential (MUAP), 3 showed short - duration MUAP mimicking myopathy, and one showed long - duration MUAP mimicking neuropathy. Two patients with normal MUAP underwent biceps biopsy, which showed selective type Ⅱ fiber atrophy. Conclusions Electrophysiologically, CMAP amplitudes of LEMS patients are usually diffusely low or borderline. LEMS patients have amplitude increments of more than 100% at high-frequency RNS, and some have amplitude decrements of more than 15% at low-frequency RNS. PEF test shows a transient but significant CMAP amplitude increase after 5-10 s maximum voluntary contraction. Needle EMG is usually normal, but some show myogenic lesions, and some show neurogenic lesions. Muscle biopsy shows selective type Ⅱ fiber atrophy. Needle EMG myogenic lesion may not be associated with pathologically selective type Ⅱ fiber atrophy.

Background: Lambert–Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of the presynaptic neuromuscular junction associated with antibody mediated dysfunction of voltage-gated calcium channels (VGCCs). LEMS can exist as a paraneoplastic syndrome, paraneoplastic-LEMS (P-LEMS), when associated with tumors, most commonly, small cell lung carcinoma (SCLC) or as a non-paraneoplastic condition (NP-LEMS) when no malignancies are detected. Methods: A retrospective chart review was conducted in 3 tertiary hospitals in Saudi Arabia for patients diagnosed with LEMS between January 2010 and January 2020. Patients meeting all the following criteria were included: (1) weakness or fatigability of one or more extremity or oculo-bulbar muscles, (2) 60% or higher increment of compound muscle action potential (CMAP) amplitudes immediately following isometric exercise, and (3) positive serum P/Q type VGCC antibodies. Clinical, laboratory, and electrophysiologic features, as well as radiologic imaging modalities performed for tumor screening were reviewed. Results: The study included six patients diagnosed with LEMS, split evenly between P-LEMS and NP-LEMS. Fatigability, particularly in the lower extremities, and dyspnea on exertion were commonly reported symptoms. Low CMAP amplitudes were more frequently seen in NP-LEMS as compared to P-LEMS when recorded from both abductor pollicis brevis and abductor digiti minimi muscles. An incremental response above 60% in post activation CMAPs was detected at similar rates following variable durations of isometric exercise (10, 15, and 20 s). Tumor types detected in 3 patients with P-LEMS are SCLC, breast carcinoma, colon adenocarcinoma, and prostate acinar adenocarcinoma. Triple malignancy was detected in one patient. Conclusion: This is the first study to describe clinical and electrophysiologic features of LEMS in an Arab ethnic cohort. Early recognition of LEMS has a significant impact on prognosis, especially given the aggressive nature of associated cancers such as SCLC. [ABSTRACT FROM AUTHOR]

This is an unusual case of voltage gated calcium channel (VGCC) antibodies leading to two distinct and chronologically separated neurologic syndromes without the presence of an underlying neoplasm. Lambert Eaton Myasthenic Syndrome (LEMS) presented five years prior to cerebellar ataxia. Both LEMS and cerebellar ataxia were responsive to treatment, but not the same therapy. He was diagnosed with LEMS through history, exam, electromyography/nerve conduction studies (EMG/NCS) with repetitive nerve stimulation (RNS) and antibody testing. He was treated with 3,4 diaminopyridine (3,4 DAP) with an excellent response. Five years later, he developed acute ataxia. The patient required months of intensive and continued immunomodulating therapy. [ABSTRACT FROM AUTHOR]

Introduction. Lambert-Eaton myasthenic syndrome (LEMS) is an ultrarare neuromuscular disease with a triad of symptoms: muscle paresis, dysautonomy, and areflexia. Amifampridine is the symptomatic treatment of LEMS. Aim of study. To assess the effectiveness and safety of treatment in the real world. Material and methods. 14 patients with non-neoplastic LEMS treated with amifampridine were enrolled in the study (female 42.9%, mean age 48.8 ± 11.4 years). The patients were assessed using the Quantitative Myasthenia Gravis (QMG) scale, QMG limb domain (LD) score, spirometry, Hand Grip Strength (GRIP) test, and repetitive nerve stimulation study (RNS) at baseline and at the end of follow-up. Diagnostic delay since first symptoms was from seven months up to 22 years. Treatment delay ranged from one to 26 years. The patients were treated and reevaluated after 21.1 ± 12.0 weeks (range 13-48). Results. All of the patients improved in QMG score. Mean improvement was 5.1 ± 2.0 (range 1-8) points (p < 0.001) and this showed no correlation with the duration of the disease before treatment (p = 0.477). 85.7% of patients (n = 12) improved = 3 points (clinically meaningful) in QMG. 78.6% of the patients improved in QMG LD [mean 2.2 ± 1.6 points (p < 0.001)]. Also, forced vital capacity (FVC) improved after treatment (p = 0.031). Mean improvement in GRIP test was 7.0 ± 7.1 kg in the right hand and 5.2 ± 7.5 kg in the left hand (p < 0.001). In RNS before treatment, facilitation (> 100%) was observed in 78.6% (n = 11) of patients, and was higher before treatment (p < 0.001). Compound muscle action potential (CMAP) amplitude was higher after treatment (p < 0.001). Mean increase of CMAP amplitude was 2.1 ± 1.6 times. In 64.3% (n = 9) of patients lowering of corticosteroid dose was achieved. Conclusions. Amifampridine is an effective treatment in non-neoplastic LEMS patients, regardless of disease duration. The treatment is well-tolerated and allows to reduce dose of corticosteroids in the majority of patients. [ABSTRACT FROM AUTHOR]

BackgroundLambert–Eaton myasthenic syndrome (LEMS) is an autoimmune disorder of the presynaptic neuromuscular junction associated with antibody mediated dysfunction of voltage-gated calcium channels (VGCCs). LEMS can exist as a paraneoplastic syndrome, paraneoplastic-LEMS (P-LEMS), when associated with tumors, most commonly, small cell lung carcinoma (SCLC) or as a non-paraneoplastic condition (NP-LEMS) when no malignancies are detected.MethodsA retrospective chart review was conducted in 3 tertiary hospitals in Saudi Arabia for patients diagnosed with LEMS between January 2010 and January 2020. Patients meeting all the following criteria were included: (1) weakness or fatigability of one or more extremity or oculo-bulbar muscles, (2) 60% or higher increment of compound muscle action potential (CMAP) amplitudes immediately following isometric exercise, and (3) positive serum P/Q type VGCC antibodies. Clinical, laboratory, and electrophysiologic features, as well as radiologic imaging modalities performed for tumor screening were reviewed.ResultsThe study included six patients diagnosed with LEMS, split evenly between P-LEMS and NP-LEMS. Fatigability, particularly in the lower extremities, and dyspnea on exertion were commonly reported symptoms. Low CMAP amplitudes were more frequently seen in NP-LEMS as compared to P-LEMS when recorded from both abductor pollicis brevis and abductor digiti minimi muscles. An incremental response above 60% in post activation CMAPs was detected at similar rates following variable durations of isometric exercise (10, 15, and 20 s). Tumor types detected in 3 patients with P-LEMS are SCLC, breast carcinoma, colon adenocarcinoma, and prostate acinar adenocarcinoma. Triple malignancy was detected in one patient.ConclusionThis is the first study to describe clinical and electrophysiologic features of LEMS in an Arab ethnic cohort. Early recognition of LEMS has a significant impact on prognosis, especially given the aggressive nature of associated cancers such as SCLC.

Background: The classic triad in LEMS is proximal muscle weakness, areflexia, and autonomic dysfunction. We have frequently observed truncal ataxia as the first complaint in LEMS patients. In this study, we aimed to show the presence of ataxia in 10 newly diagnosed LEMS patients in the past 3 years and what factors influence it. Methods: We present the clinical findings, voltage-gated calcium channels antibody positivity, and electrophysiologic findings of newly diagnosed LEMS patients who presented to our tertiary care center during the past 3 years. Results: Of the 10 LEMS patients examined, 60% (6) were males and 40% (4) were females. The first and most dysfunctional symptoms were gait disorder and loss of balance in seven of the patients. These patients had ataxia, a gait disturbance that was disproportionate to the proximal weakness. Although the patients had mild proximal weakness in the lower extremities, they had considerable difficulty walking. Proximal muscle weakness was present in six patients, speech disorders in three patients, dysphagia in three patients, dry mouth in three patients, ptosis in two patients, diplopia in two patients, and nystagmus in one patient. Conclusion: We believe that more caution is needed in patients with truncal ataxia when LEMS is suspected. This is because we have seen that the first complaints in 7 out of 10 LEMS patients were truncal ataxia, loss of balance, and gait disturbance.

BACKGROUND: Lambert–Eaton myasthenic syndrome (G73.1 according to ICD-10) is a rare autoimmune disease associated with a presynaptic impairment of neuromuscular transmission due to the production of antibodies to voltage-gated calcium channels. The peculiarity of Lambert–Eaton myasthenic syndrome is manifested in a combination of increased muscle weakness and fatigue with the phenomenon of «working in» — an increase in the muscle strength against the background of muscle load after a short-term maximum contraction. Lambert-Eaton myasthenic syndrome is often associated with small cell lung cancer and very rarely develops with tumors of another localization. CLINICAL CASE DESCRIPTION: We observed an 80-year-old patient with complaints of weakness and pain in the hips, shoulders, pelvic region, and half-ptosis of the eyelids. For half-ptosis of the eyelids, a differential diagnosis was conducted with myasthenia gravis. Stimulation electromyography revealed the M-response increment, i.e. the phenomenon of “working in”, which is typical for this syndrome. The examination revealed papillary thyroid cancer, which was later treated surgically. CONCLUSION: This case illustrates Lambert–Eaton’s paraneoplastic myasthenic syndrome, a rare tumor form associated with thyroid cancer.

Spontaneous regression (SR) of cancer is very rare, especially of small cell lung cancer (SCLC). Recently, an association of paraneoplastic neurological syndrome (PNS) has been reported as a cause of SR of cancer, and onconeural antibodies are a possible factor in the SR of cancer associated with PNS. We herein report the first case of SR of SCLC combined with anti-P/Q-type of voltage-gated calcium channel (VGCC) antibody-positive Lambert-Eaton myasthenic syndrome (LEMS), a subtype of PNS. This case report suggests that SCLC may be spontaneously reduced by an autoimmune response induced by VGCC antibodies associated with LEMS. Our finding may help elucidate the mechanisms that inhibit tumor growth and cause the regression of tumors.

Introduction: Lambert-Eaton myasthenia syndrome (LEMS) is a rare autoimmune disorder characterized by autoantibodies targeting presynaptic neuromuscular junctions. It results in muscle weakness and autonomic dysfunction. LEMS can be idiopathic or associated with neoplastic diseases, often small-cell lung cancer. This case report describes a rare instance of paraneoplastic LEMS in a man with non-Hodgkin lymphoma. Case Presentation: A 57-year-old male with non-Hodgkin lymphoma presented with progressive muscle weakness, diminished reflexes, and autonomic symptoms. Diagnosis revealed LEMS with autoantibodies against voltage-gated calcium channels. Immunosuppressive therapy and lymphoma treatment led to significant improvement in his condition. Conclusion: This case highlights the rare occurrence of paraneoplastic LEMS in a patient with non-Hodgkin lymphoma. Recognition and timely management of LEMS alongside lymphoma treatment can lead to significant clinical improvement, emphasizing the need for increased awareness of such complex associations.

Lambert–Eaton myasthenic syndrome (LEMS) is a rare paraneoplastic neurological syndrome of the neuromuscular transmission. The symptoms often progress slowly and can be misdiagnosed in early stage. Seropositive SOX‐1 antibodies are support for the diagnosis of LEMS and have high specificity for small cell lung cancer (SCLC). In this paper, we report a case of a 56‐year‐old man with smoking history who was admitted to hospital with progressive muscle weakness of the proximal legs. LEMS was diagnosed by repetitive nerve stimulation (RNS) testing and seropositive SOX‐1 antibodies. Primary screening with chest computed tomography (CT) and integrated PET/CT did not reveal any tumor. After continuous follow‐up, SCLC was found by chest CT and confirmed with pathological examination 10 months after the diagnosis of LEMS. Long‐term follow‐up and screening for occult SCLC in LEMS patients with positive SOX‐1 antibodies are very important. [ABSTRACT FROM AUTHOR]

Myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS), and congenital myasthenic syndromes (CMS) represent an etiologically heterogeneous group of (very) rare chronic diseases. MG and LEMS have an autoimmune-mediated etiology, while CMS are genetic disorders. A (strain dependent) muscle weakness due to neuromuscular transmission disorder is a common feature. Generalized MG requires increasingly differentiated therapeutic strategies that consider the enormous therapeutic developments of recent years. To include the newest therapy recommendations, a comprehensive update of the available German-language guideline 'Diagnostics and therapy of myasthenic syndromes' has been published by the German Neurological society with the aid of an interdisciplinary expert panel. This paper is an adapted translation of the updated and partly newly developed treatment guideline. It defines the rapid achievement of complete disease control in myasthenic patients as a central treatment goal. The use of standard therapies, as well as modern immunotherapeutics, is subject to a staged regimen that takes into account autoantibody status and disease activity. With the advent of modern, fast-acting immunomodulators, disease activity assessment has become pivotal and requires evaluation of the clinical course, including severity and required therapies. Applying MG-specific scores and classifications such as Myasthenia Gravis Activities of Daily Living, Quantitative Myasthenia Gravis, and Myasthenia Gravis Foundation of America allows differentiation between mild/moderate and (highly) active (including refractory) disease. Therapy decisions must consider age, thymic pathology, antibody status, and disease activity. Glucocorticosteroids and the classical immunosuppressants (primarily azathioprine) are the basic immunotherapeutics to treat mild/moderate to (highly) active generalized MG/young MG and ocular MG. Thymectomy is indicated as a treatment for thymoma-associated MG and generalized MG with acetylcholine receptor antibody (AChR-Ab)-positive status. In (highly) active generalized MG, complement inhibitors (currently eculizumab and ravulizumab) or neonatal Fc receptor modulators (currently efgartigimod) are recommended for AChR-Ab-positive status and rituximab for muscle-specific receptor tyrosine kinase (MuSK)-Ab-positive status. Specific treatment for myasthenic crises requires plasmapheresis, immunoadsorption, or IVIG. Specific aspects of ocular, juvenile, and congenital myasthenia are highlighted. The guideline will be further developed based on new study results for other immunomodulators and biomarkers that aid the accurate measurement of disease activity. [ABSTRACT FROM AUTHOR]

INTRODUCTION:There are no validated, practical, and quantitative measures of disease severity in Lambert-Eaton myasthenia (LEM). METHODS:Data from the Effectiveness of 3,4-Diaminopyridine in Lambert-Eaton Myasthenic Syndrome (DAPPER) trial were analyzed to assess triple timed up-and-go (3TUG) reproducibility and relationships between 3TUG times and other measures of LEM severity. RESULTS:The coverage probability technique showed ≥0.90 probability for an acceptable 3TUG difference of ≤0.2, indicating that it is reproducible in LEM patients. The correlation between 3TUG times and lower extremity function scores was significant in subjects who continued and in those who were withdrawn from 3,4-diaminopyridine free base. Worsening patient-reported Weakness Self-Assessment Scale and Investigator Assessment of Treatment Effect scores corresponded with prolongation of 3TUG times. DISCUSSION:The 3TUG is reproducible, demonstrates construct validity for assessment of lower extremity function in LEM patients, and correlates with changes in patient and physician assessments. These findings, along with prior reliability studies, indicate 3TUG is a valid measure of disease severity in LEM.

Robert M Pascuzzi, Cynthia L Bodkin Indiana University School of Medicine, Indiana University Health, Indianapolis, IN, USACorrespondence: Robert M Pascuzzi, Indiana University School of Medicine, Indiana University Health, Indianapolis, IN, 46202, USA, Email rpascuzz@iupui.eduAbstract: “Myasthenia Gravis is, like it or not, the neurologist’s disease!” (Thomas Richards Johns II, MD Seminars in Neurology 1982). The most common disorders in clinical practice involving defective neuromuscular transmission are myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS). The hallmark of weakness related to malfunction of the neuromuscular junction (NMJ) is variability in severity of symptoms from minute to minute and hour to hour. Fatigable weakness and fluctuation in symptoms are common in patients whether the etiology is autoimmune, paraneoplastic, genetic, or toxic. Autoimmune MG is the most common disorder of neuromuscular transmission affecting adults with an estimated prevalence of 1 in 10,000. While LEMS is comparatively rare, the unique clinical presentation, the association with cancer, and evolving treatment strategies require the neurologist to be familiar with its presentation, diagnosis, and management. In this paper we provide a summary of the meaningful recent clinical developments in the diagnosis and treatment of both MG and LEMS.Keywords: Myasthenia Gravis, Lambert-Eaton Myasthenic Syndrome, disorders of neuromuscular transmission

Abstract Background The Lambert-Eaton myasthenic syndrome (LEMS) is a rare disorder characterized by proximal muscle weakness and autonomic dysfunction due to involvement of the neuromuscular junction A case of delayed unilateral recovery from spinal anesthesia in a patient with LEMS undergoing open cholecystectomy is described. Case presentation A 42-year-old lady, on treatment for LEMS with pyridostigmine, prednisolone, and azathioprine presented with cholelithiasis and was scheduled for open cholecystectomy. Neuraxial anesthesia combined with a light plane of general anesthesia provided adequate muscle relaxation without the use of neuromuscular blocking drugs. In spite of perioperative continuation of anticholinesterases, the patient required 12 h post-surgery for complete bilateral motor recovery from spinal anesthesia. Conclusions A combination of spinal anesthesia with a light plane of general anesthesia appears to be a safe anesthetic technique for managing patients with Lambert-Eaton myasthenic syndrome undergoing open cholecystectomy. However, neurologically asymptomatic patients with good treatment compliance may also show an unusual delay in recovery from neuraxial anesthesia.

Lambert‐Eaton myasthenic syndrome (LEMS) is an autoimmune paraneoplastic syndrome with proximal muscle weakness, that often complicates small cell lung cancer. It is known that neurological symptoms do not improve with malignancy treatment alone in many LEMS patients, therefore treatment is often difficult. Since Lambert‐Eaton myasthenic syndrome is a rare disease with a frequency of about 1/100 that of myasthenia gravis, there are only a few case reports on malignancy complications other than small cell lung cancer. We report a LEMS patient in his 40s who was found to have an anterior mediastinal mass. We performed surgical resection and confirmed the diagnosis of primary thymic marginal zone B‐cell lymphoma by pathological diagnosis using immunostaining. Thymectomy and malignant lymphoma treatment with rituximab had no effect on neurological symptoms. The neurological symptoms improved only after we provided comprehensive care with the haematology, neurology, and rehabilitation department. [ABSTRACT FROM AUTHOR]

INTRODUCTION:3,4-diaminopyridine has been used to treat Lambert-Eaton myasthenia (LEM) for 30 years despite the lack of conclusive evidence of efficacy. METHODS:We conducted a randomized double-blind placebo-controlled withdrawal study in patients with LEM who had been on stable regimens of 3,4-diaminopyridine base (3,4-DAP) for ≥ 3 months. The primary efficacy endpoint was >30% deterioration in triple timed up-and-go (3TUG) times during tapered drug withdrawal. The secondary endpoint was self-assessment of LEM-related weakness (W-SAS). RESULTS:Thirty-two participants were randomized to continuous 3,4-DAP or placebo groups. None of the 14 participants who received continuous 3,4-DAP had > 30% deterioration in 3TUG time versus 72% of the 18 who tapered to placebo (P

Introduction: Lambert-Eaton myasthenia syndrome (LEMS) is a rare autoimmune disorder characterized by autoantibodies targeting presynaptic neuromuscular junctions. It results in muscle weakness and autonomic dysfunction. LEMS can be idiopathic or associated with neoplastic diseases, often small-cell lung cancer. This case report describes a rare instance of paraneoplastic LEMS in a man with non-Hodgkin lymphoma. Case Presentation: A 57-year-old male with non-Hodgkin lymphoma presented with progressive muscle weakness, diminished reflexes, and autonomic symptoms. Diagnosis revealed LEMS with autoantibodies against voltage-gated calcium channels. Immunosuppressive therapy and lymphoma treatment led to significant improvement in his condition. Conclusion: This case highlights the rare occurrence of paraneoplastic LEMS in a patient with non-Hodgkin lymphoma. Recognition and timely management of LEMS alongside lymphoma treatment can lead to significant clinical improvement, emphasizing the need for increased awareness of such complex associations. [ABSTRACT FROM AUTHOR]

Lambert-Eaton myasthenic syndrome (LEMS) is a paraneoplastic or autoimmune neuromuscular disorder that typically presents with limb weakness or autonomic dysfunction. Here, we report a rare case of LEMS with acute type 2 respiratory failure as the initial symptom. A 79-year-old woman was admitted with acute disturbance of consciousness and type 2 respiratory failure. On admission, she presented with confusion, seizures, and respiratory acidosis requiring non-invasive positive pressure ventilation. Cerebrospinal fluid analysis revealed pleocytosis and elevated protein levels without infection. Electroencephalography showed nonspecific slowing, while imaging revealed no abnormalities. A nerve conduction study on day 10 confirmed LEMS, with findings of low-amplitude compound motor action potentials and facilitation on high-frequency stimulation. Coexisting autoimmune encephalitis was diagnosed based on clinical presentation and serum antibody positivity for voltage-gated calcium channels and gamma-aminobutyric acid B receptors. Positron emission tomography/CT identified small-cell lung cancer, confirmed by biopsy. The patient and family declined invasive cancer therapies. Then, the patient passed away on day 60. This case highlights the diagnostic challenge of atypical presentations of paraneoplastic neurological syndromes, including LEMS and autoimmune encephalitis. Early recognition of LEMS in patients with unexplained type 2 respiratory failure through nerve conduction studies is critical. This report underscores the importance of considering paraneoplastic etiologies in patients with multiple neurological syndromes., Competing Interests: Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2025, Uemura et al.)

BackgroundWhile immune checkpoint inhibitors (ICIs) have been revolutionary in the treatment of cancer, their administration has been associated with a variety of immune-related adverse events (irAEs), including myasthenia gravis (MG), and Lambert-Eaton myasthenic syndrome (LEMS).ObjectiveTo provide a comprehensive synthesis of the evidence supporting an etiological role for ICIs in MG and LEMS in patients with no prior history of autoimmune disease.HypothesisICIs may trigger MG and LEMS in patients with no prior susceptibility to autoimmune disease.MethodsRelevant primary research on Medline was interrogated using a series of search algorithms. Search terms were constructed based on the PICOS tool endorsed by the Cochrane Collaboration, which describes population, intervention, comparison, outcomes, and study design. Papers were screened according to inclusion and exclusion criteria. Additional papers were retrieved from the reference lists of screened papers. Each paper included in the qualitative synthesis was assigned an integrated metric of evidence (IME) value, ranging from 0 to 7, based on study design, quality of data, likelihood of a causal link between the immune checkpoint inhibitor(s) and MG/LEMS, confidence of MG/LEMS diagnosis, and the number of patients treated with an ICI prior to MG/LEMS diagnosis.ResultsNinety-four papers describing at least one patient treated with ICI(s) prior to the onset of MG and/or LEMS were documented. Overall evidence for a causal link between ICI administration and MG/LEMS was low, with a median IME value of 2.88 (range 2.05–6.61).ConclusionsThere is a paucity of evidence in support of an etiological relationship between ICIs and MG/LEMS, due largely to the lack of mechanistic studies and/or prospective clinical trials with relevant study endpoints. The current literature is dominated by case reports and retrospective cohort studies, which inherently yield only low-level evidence, supporting the need for further work in this area. A role of ICIs in the etiology of MG/LEMS remains plausible, arguing for continued vigilance for irAEs in patients treated with these drugs. We argue that there is a need for future mechanistic, high quality, large-scale studies specifically investigating the possible etiological role of ICIs in MG/LEMS.

We report a severe defect of neuromuscular transmission in a consanguineous patient with a homozygous variant in the laminin α5 subunit gene (LAMA5). The variant c.8046C > T (p.Arg2659Trp) is rare and has a predicted deleterious effect. The affected individual, who also carries a rare homozygous sequence variant in LAMA1, had normal cognitive function, but magnetic resonance brain imaging showed mild volume loss and periventricular T2 prolongation. Repetitive nerve stimulation at 2 Hz showed 50% decrement of compound muscle action potential amplitudes but 250% facilitation immediately after exercise, similar to that seen in Lambert-Eaton myasthenic syndrome. Endplate studies demonstrated a profound reduction of the endplate potential quantal content but normal amplitudes of miniature endplate potentials. Electron microscopy showed endplates with increased postsynaptic folding that were denuded or only partially occupied by small nerve terminals. Expression studies revealed that p.Arg2659Trp caused decreased binding of laminin α5 to SV2A and impaired laminin-521 cell adhesion and cell projection support in primary neuronal cultures. In summary, this report describing severe neuromuscular transmission failure in a patient with a LAMA5 mutation expands the list of phenotypes associated with defects in genes encoding α-laminins.

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.

Abstract Background Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder of neuromuscular transmission. The objective was to examine the efficacy and safety of 3,4-diaminopyridine (3,4-DAP) in patients with LEMS. Methods We searched several databases to identify relevant studies, including PubMed, EMBASE, Web of Science, MEDLINE, Cochrane Neuromuscular Disease Group Specialized Register and the Cochrane Central Register of Controlled Trials(CENTRAL). The primary outcome, quantitative myasthenia gravis (QMG) score and the secondary outcome, compound muscle action potentials (CMAP) amplitude were pooled by meta-analysis. Results Six randomised controlled trials (RCTs) involving 115 patients with LEMS were included. QMG score showed a significant decrease (improvement) of 2.76 points (95 % CI, -4.08 to -1.45, p

Introduction: Lambert–Eaton myasthenic syndrome (LEMS) is characterized by autoantibodies against voltage-gated calcium channels (VGCC) at the neuromuscular junction causing proximal muscle weakness, decreased tendon reflexes, and autonomic changes. The European LEMS registry aimed to collate observational safety data for 3,4-diaminopyridine phosphate (3,4-DAPP) and examine long-term outcomes for patients with LEMS. Methods: Thirty centers across four countries participated in the non-interventional European LEMS registry. Any patients diagnosed with LEMS by means of clinical assessment and abnormal neurophysiological testing, or clinical assessment and positive for VGCC antibodies were eligible to participate. Patients were monitored using standard assessments for LEMS-related clinical manifestations. Results: Among 96 evaluable participants, 50 (52.1%) were being treated with 3,4-DAPP, 21 (21.9%) with 3,4-diaminopyridine (3,4-DAP), and 25 (26.0%) with other treatments (e.g., pyridostigmine, corticosteroids, immunoglobulins, and azathioprine); 74 participants (77.1%) were exposed to 3,4-DAPP at any time. Quantitative myasthenia gravis scores were similar across treatment groups. Muscle strength was generally good and maintained during follow-up. Cerebellar ataxia, defined as a negative Romberg's test and at least one other positive ataxia test, was observed in 30 (56.6%) patients. Most participants had reduced reflex tone and limited functioning. Sustained or improved functioning was observed in participants administered 3,4-DAPP. Inconsistent and sporadic functional improvement and regression was observed with 3,4-DAP and other treatments. Fifty-five treatment-related adverse events (AEs) were reported by 32 (33.3%) participants. Eight (8.3%) participants reported nine treatment-related serious AEs. No new safety signals were identified. Conclusion: No new safety signals were observed following long-term management of LEMS with 3,4-DAPP. [ABSTRACT FROM AUTHOR]

The mouse neuromuscular junction (NMJ) has long been used as a model synapse for the study of neurotransmission in both healthy and disease states of the NMJ. Neurotransmission from these neuromuscular nerve terminals occurs at highly organized structures called active zones (AZs). Within AZs, the relationships between the voltage-gated calcium channels and docked synaptic vesicles govern the probability of acetylcholine release during single action potentials, and the short-term plasticity characteristics during short, high frequency trains of action potentials. Understanding these relationships is important not only for healthy synapses, but also to better understand the pathophysiology of neuromuscular diseases. In particular, we are interested in Lambert-Eaton myasthenic syndrome (LEMS), an autoimmune disorder in which neurotransmitter release from the NMJ decreases, leading to severe muscle weakness. In LEMS, the reduced neurotransmission is traditionally thought to be caused by the antibody-mediated removal of presynaptic voltage-gated calcium channels. However, recent experimental data and AZ computer simulations have predicted that a disruption in the normally highly organized active zone structure, and perhaps autoantibodies to other presynaptic proteins, contribute significantly to pathological effects in the active zone and the characteristics of chemical transmitters. [ABSTRACT FROM AUTHOR]