Lambert-Eaton myasthenic syndrome (LEMS) is a rare disease but is often associated with small-cell lung cancer (SCLC). We discuss the case of a 65-year-old man diagnosed with SCLC-LEMS and treated with carboplatin, etoposide, and durvalumab. Lower extremity weakness and high anti-P/Q voltage-gated calcium channel (VGCC) antibody levels were diagnostic and helpful. The patient showed a reduction in neurological symptoms with treatment for SCLC, including an immune checkpoint inhibitor (ICI), without standard treatment for LEMS. This treatment may be a treatment option, although the recurrence of LEMS as an immune-related adverse events (irAEs) should be noted.

A 74-year-old man experienced diplopia, generalized muscle weakness, and acute respiratory failure. He was diagnosed with Lambert-Eaton myasthenic syndrome (LEMS) and treated with immunotherapy, but no improvement was observed, and additional symptoms, including central apnea and hallucinations, appeared. Subsequent serum and cerebrospinal fluid (CSF) analyses confirmed the presence of GABAB receptor antibodies, indicating the coexistence of autoimmune encephalitis. Although there were no findings of malignancy, it is highly likely that occult small-cell lung carcinoma was present. When atypical symptoms occur in patients with LEMS, it is important to consider the possibility of concomitant autoimmune encephalitis.

BACKGROUND: Lambert-Eaton myasthenic syndrome (LEMS) is a type of paraneoplastic syndrome that may initially manifest itself with proximal weakness and gait abnormalities. Approximately up to 50% of LEMS patients have a primary autonomic dysfunction.
METHODS: We present here a case of a 75-year-old male with symmetric proximal muscle weakness, dry mouth and constipation. The cutaneous response to scratch and upright tilt-table testing were positive. A repetitive nerve stimulation test showed that there was a decremental response of compound muscle action potential (CMAP) amplitude at 3 Hz while an incremental response at 20 Hz. The presence of antibodies against voltage-gated calcium channels (VGCC) confirmed the diagnosis. Because of the prominent symptom of autonomic disorder, the patient further underwent the test of skin sympathetic response (SSR). Lower amplitude and longer response duration were found in palms, while it evoked no response in soles.
CONCLUSIONS: In this case, we present the detailed results of SSR test on a patient suffering LEMS with autonomic disorder. Since autonomic dysfunction has a significant impact on clinical management and SSR test is an effective detection method, we recommend that SSR test be performed on patients with LEMS regularly.

We herein report two P/Q-type VGCC antibody-positive LEMS patients who responded dramatically to cholinesterase inhibitors. Patient 1, a 76-year-old man, had small-cell lung cancer and developed LEMS during chemotherapy. When symptomatic treatment was started with pyridostigmine, gait disturbance was ameliorated, and his modified Rankin scale decreased from 4 points to 3 points. Patient 2, a 68-year-old man, had cancer-free LEMS. Distigmine bromide was very effective and ameliorated not only his gait disturbance but also autonomic symptoms, and his modified Rankin scale decreased from 2 points to 1 point. Cholinesterase inhibitors alone may be effective in a small portion of LEMS patients.

OBJECTIVE: To report the clinical features and the neurophysiological approach of a patient with Lambert-Eaton myasthenic syndrome (LEMS), highlighting the diagnostic role of the stimulated single fiber electromyography (sSFEMG).
METHODS: A 60-year-old woman presenting with the LEMS triad (proximal and axial weakness, autonomic dysfunction and areflexia) was evaluated by neurophysiological tests (electroneuromyography, repetitive stimulation test (TSR), voluntary and stimulated SFEMG). We reported: 1) increase of compound muscle action potential (CMAP) amplitude (>60%) following brief isometric exercise compared to the rest (baseline); 2) decremental/incremental response of CMAP amplitude at low- (3 Hz) and high-frequency (30 Hz) repetitive stimulation test (RST), respectively; 3) increased neuromuscular jitter and blocking at voluntary single-fiber electromyography (vSFEMG); 4) stimulation rate-dependent reduction of the neuromuscular jitter and blocking at sSFEMG. Diagnosis was confirmed by serological demonstration of circulating voltage gated calcium channels (VGCC) antibodies.
CONCLUSIONS: The present case highlights the role of the sSFEMG in the diagnosis of LEMS, underling the stimulation rate-dependency of both neuromuscular jitter and blocks.

Paraneoplastic cerebellar degeneration and Lambert-Eaton myasthenic syndrome (PCD-LEMS) are usually associated with small-cell lung carcinoma (SCLC). PCD-LEMS with extrapulmonary non-SCLC tumors; however, has not been previously reported. A 78-year-old man presented with dysarthria, dysphagia, staggering gait, and lower extremity muscle fatigue. He was diagnosed with PCD-LEMS associated with neuroendocrine carcinoma of the oropharynx, based on the histological findings of the biopsy, the existence of antibodies against P/Q-type voltage-gated calcium channels, and an incremental response of the compound muscle action potentials during repetitive nerve stimulation tests. Thus, PCD-LEMS should be included in the differential diagnosis of neurological dysfunction, even in extrapulmonary non-SCLC patients.

Lambert-Eaton myasthenic syndrome (LEMS) is an uncommon autoimmune idiopathic or paraneoplastic syndrome producing antibodies against voltage presynaptic calcium channels. According to previous studies, many patients with LEMS experience remission in both the clinical symptoms of muscle weakness and the electrophysiologic abnormalities after successful treatment of lung SCC. However, some patients might not respond to conventional therapy and eventually require palliative care. Hereby, we reported a LEMS patient with advanced lung malignancy was referred for palliative care. He was benefited from multidisciplinary approach even with limited survival. In this case, use of 3,4-diaminopyridine (3,4-DAP) had other roles apart from symptomatic treatment.

BACKGROUND: Lambert-Eaton myasthenic syndrome, a presynaptic neuromuscular junction autoimmune disorder, rarely occurs in children. Patients typically present with proximal lower extremity weakness with areflexia.
METHODS: We report three children presenting between ages 9 and 10 years diagnosed with Lambert-Eaton myasthenic syndrome 2 years, 1 year, and 5 months later, respectively. Their clinical attributes are correlated with nine other pediatric Lambert-Eaton myasthenic syndrome patients found in our literature review.
RESULTS: These patients were identified as having Lambert-Eaton myasthenic syndrome during their evaluation for proximal weakness. Low-amplitude compound muscle action potentials classically facilitating >100% with voluntary exercise and/or 50 Hz stimulation were essential to diagnosis. Three of the 12 children had associated malignancies, two of them had lymphoproliferative disorders with onset of symptoms more rapid than the rest, and the third had neuroblastoma. The nine nonparaneoplastic Lambert-Eaton myasthenic syndrome patients responded to immunomodulatory therapy with close return to their baseline function. Complete remission no longer necessitating medication was reported in two patients. Follow-up up to 17 years was available on two patients previously reported.
CONCLUSIONS: Lambert-Eaton myasthenic syndrome is a diagnosis that must be considered in children presenting with unidentified proximal muscle weakness. In most children, Lambert-Eaton myasthenic syndrome is a primary autoimmune disorder that is treatable. Nevertheless, a search for malignancy is recommended.