Non-paraneoplastic Lambert-Eaton myasthenic syndrome: a brief review of 10 cases / Síndrome miastênica de Lambert-Eaton não paraneoplásica: uma breve revisão de dez casos

Lambert-Eaton myasthenic syndrome (LEMS) is an immune-mediated disorder of the presynaptic neuromuscular transmission, which more frequently occurs as the remote effect of a neoplasm, in the paraneoplastic form (P-LEMS), or in a non-paraneoplastic form (NP-LEMS); but few studies describe the clinical features of NP-LEMS. We analyzed the clinical manifestations, laboratory findings, electrophysiological studies, and treatment responses in ten Brazilian patients suffering from NP-LEMS. The mean age was 41.5 years. More often neurological findings were hyporeflexia or areflexia with a post-exercise improvement. Treatment response occurred with pyridostigmine, guanidine, prednisone, azathioprine, and cyclosporine; but not response was observed after intravenous immunoglobulin and plasma exchange. Age at onset, clinical manifestations, and electrophysiological abnormalities can help more in the diagnosis than serum antibodies; the symptomatic treatment with pyridostigmine was effective; and the immunosuppressive treatment with prednisone, azathioprine, or cyclosporine was more beneficial than plasma exchange or intravenous immunoglobulin treatment.

A síndrome miastênica de Lambert-Eaton (LEMS) é uma desordem imunomediada da transmissão neuromuscular pré-sinaptica, que mais frequentemente ocorre como efeito à distância de uma neoplasia, na forma paraneoplásica (P-LEMS), ou na forma não paraneoplásica (NP-LEMS); porém poucos estudos têm descrito as características da NP-LEMS. Nós analisamos as manifestações clínicas, laboratoriais, eletrofisiológicas, e resposta ao tratamento em dez pacientes brasileiros com NP-LEMS. A idade média foi de 41,5 anos. A manifestação neurológica mais freqüente foi hiporeflexia ou arreflexia com melhora após o exercício. A resposta ao tratamento ocorreu com piridostigmina, guanidina, prednisona, azatioprina, e ciclosporina; mas não com imunoglobulina intravenosa e plasmaférese. A idade de início, manifestações clínicas e eletrofisiológicas ajudaram mais no diagnóstico do que os anticorpos séricos; o tratamento sintomático com piridostigmina foi efetivo; e o tratamento imunossupressor com prednisona, azatioprina, ou ciclosporina beneficiou mais do que a plasmaférese ou a imunoglobulina intravenosa.

Clinical analysis of 12 Korean Lambert-Eaton myasthenic syndrome (LEMS) patients

The Lambert-Eaton myasthenic syndrome (LEMS) heralds the occurrence of malignancy, especially small-cell lung cancer (SCLC), but it can also occur in the absence of cancer. Twelve patients were diagnosed as LEMS by clinical features and the classical electrophysiological triad, which includes a low amplitude of compound muscle action potentials (CMAP), decremental responses on low-rate stimulation, and incremental responses on high-rate stimulation on the repetitive nerve stimulation (RNS) test. There were 6 male and 6 female patients, ranging in age from 49 to 66 years. Malignancy(all were SCLC) was found in 7 patients. Males predominantly expressed the paraneoplastic form; whereas the primary autoimmune form was found only in women, who showed a good response to corticosteroid treatment. The neurological features were similar in both groups: proximal lower limb weakness, depressed muscle stretch reflexes, and dryness of mouth in nearly all patients. Bulbar dysfunction and limb paresthesia were a little more frequent in the paraneoplastic form. In RNS tests, the characteristic electrophysiological abnormalities were found in all patients and were more profound in the paraneoplastic form. We concluded that LEMS is commonly associated with malignancy, especially SCLC, but it should also be stressed that there are many female LEMS patients who do not harbor any malignancy at all, and that other treatment strategies such as immunotherapy should be considered for these patients.