[Non-neoplastic Lambert-Eaton syndrome. A frequently missed diagnosis?]

Three cases of non-paraneoplastic Lambert-Eaton syndrome are presented. There remains no indication of neoplasm after illnesses of nine years, 36 months and 20 months respectively. In one case, the syndrome became manifest during chloroquine medication. The cause of the proximal lower limb weakness had not been recognized during previous hospital stays, although in retrospect indications of a Lambert-Eaton syndrome were found in the electrophysiological tracings. The conclusive diagnosis was made electrophysiologically. The leading sign was an abnormally low compound muscle action potential evoked by supramaximal nerve stimulation. Furthermore, the characteristic increase of amplitude of the compound muscle potential after maximal voluntary contraction or at high frequency stimulation (20 Hz) could be demonstrated. It is concluded that the non-paraneoplastic Lambert-Eaton myasthenic syndrome may frequently remain unrecognized.