The Lambert-Eaton Myasthenic Syndrome — an Overview

AbstractThe Lambert Eaton myasthenic syndrome (LEMS) has a prevalence of around 5/100 0000 and is around 10–20 times rarer than myasthenia gravis (MG). Although LEMS does have a number of similarities to MG, there are important differences. The syndrome is characterized by a mostly proximally localised exercise induced muscle weakness that can lead to respiratory failure often accompanied by autonomous dysfunction. Disease symptoms are caused by autoantibodies directed against P/Q type voltage gated calcium channels (VGCC) that are expressed in the presynaptic motoric nerve terminals. The diagnosis of LEMS is based on the detection of the pathogenic anti-VGCC antibodies as well as the observation of an increment of at least 60% in the electrophysiological examination of an affected muscle. An increment is defined by an increase of the at rest reduced compound muscle action potential (CMAP) either after voluntary maximal innervation or after high frequent (≥20 Hz) stimulation. In almost one third LEMS is of paraneoplastic origin. Therefore an intensive tumor screening is necessary after diagnosis.There are some differences in the clinical presentation between paraneoplastic (pLEMS)