Lambert-Eaton myasthenic syndrome: Report of two cases

Abstract

-Two cases of Lambert-Eaton myasthenic syndrome, in female patients whose neoplasm investigation was negative, are reported. Repetitive stimulation of ulnar nerve showed an incremental response (+187% and +198%). Needle EMG was normal in one of them, however, the other patient showed fibrillation potentials, positive sharp waves, potentials of low amplitude and short duration. The authors discuss the clinical, electrophysiological, and pathological features of the disease, as well as some aspects of the treatment and follow-up of these patients.KEY WORDS: Lambert-Eaton myasthenic syndrome, neurophysiological study, muscular biopsy, treatment. Síndrome miastênica de Lambert-Eaton: relato de dois casosRESUMO -São descritos dois casos de síndrome miastênica de Lambert-Eaton em pacientes do sexo feminino, nas quais a investigação de neoplasias foi negativa. Os testes de estimulação repetitiva mostraram incrementos de 187 e 198%. A eletromiografia de agulha em um dos casos foi normal e no outro mostrou potenciais de fibrilação, ondas agudas positivas de curta duração e baixa amplitude de potenciais. São discutidos aspectos clínicos, neurofisiológicos, biópsia muscular, tratamento e acompanhamento desta condição rara. PALAVRAS-CHAVE: síndrome miastênica de Lambert-Eaton, estudo neurofisiológico, biópsia muscular, tratamento.Lambert-Eaton myasthenic syndrome is a rare condition, resulting from an acetylcholine release deficiency in the neuromuscular junction. Over 50% of the cases are related with oat cell lung carcinoma [1][2][3] . Lambert-Eaton syndrome has also been associated with squamous cell lung carcinoma, mixed tumors of the parotid glands, systemic mastocytosis, sarcomas, kidney carcinoma and other malignant neoplastic diseases [3][4][5] . As Lambert-Eaton syndrome presents mostly as a paraneoplastic condition, an extensive investigation of malignant tumors should be performed. However, approximately 40% of the patients do not show any evidence of cancer, and in these cases, the disease is considered to be of primary autoimmune origin 1,2 .We report two cases of Lambert-Eaton myasthenic syndrome in female patients whose investigation for neoplastic diseases was negative, and due to the rarity of this type of disease, we found it worth putting on record.