[Lambert-Eatone myastenic syndrome].

A detailed comparative analysis of neurologic symptoms in 45 patients with Lambert-Eatone myastenic syndrome (LEMS) and 42 patients with generalized myasthenia allowed us to single out clinical patterns facilitating disease diagnosis and differentiation. There were no clinical differences in patients having LEMS with or without paraneoplastic process. Electromyography study revealed the presence of typical phenomena: a reduced amplitude of compound muscle action potential and incremental response at 40-Hz stimulation. The compound muscle action potential tripled after 20 s of maximal voluntary contraction. Sera from 89% of patients with LEMS contained IgG antibodies that immunoprecipitate a radiolabeled complex of a selective antagonist of P/Q type voltage-gated calcium channels. The degree of inhibition of calcium influx by patient's IgG correlated with the reduction in amplitude of the resting compound muscle action potential.