LAMBERT-EATON MYASTHENIC SYNDROME. CLINICAL AND ELECTROPHYSIOLOGICAL FINDINGS IN 35 PATIENTS

Abstract

Objective: To describe the clinical and electrophysiological characteristics of patients with Lambert-Eaton myasthenic syndrome.
Material: We present 35 patients with LEMS.
Results: 20 patients were male, and the mean age of all was 61,97 years (35-81). Proximal muscle weakness presented 76,5% and generalized 23,5%. Tendon reflexes were absent οr depressed in 96,7%. The syndrome was diagnosed 8.5 months from the onset of the symptoms (0.5-48). Acetylcholine receptors antibodies were negative in all patients and anti-VGCC antibodies were measured in 21 patients and were positive in 19 (90,5%). All patients fulfilled the electrophysiological criteria for LEMS: Low amplitude of muscle action potential at rest and increment after 15 sec of voluntary contraction, decrement at 3Hz and increment more than 60% at 30-40Hz. The syndrome was paraneoplastic in 78,1% and in 65,6% a histologically verified small cell lung cancer (SCLC) was diagnosed. Four more patients were diagnosed with other malignancies, mainly leukaemia.
Conclusion: In patients with atypical proximal weakness, absent or depressed tendon reflexes and autonomic symptoms, mainly impotence and dry mouth, the diagnosis of LEMS must be considered and, mainly in the older male subjects, the possibility of small-cell lung cancer must be seriously considered and investigated. In the non-cancer LEMS group the prognosis is favorable.