[Lambert-Eaton syndrome. Diagnostic, nosologic and therapeutic problems].

We report on five cases of this myasthenic disorder associated with a loss of deep tendon reflexes, dry mouth and impotence. The diagnosis relies upon the response to repeated electric stimulations: with stimulations at a frequency of 5 Hz, the size of the potentials decreases by more than 30 p. 100 and, at 30 Hz, increases by more than 60 p. 100. This profile differentiates Lambert-Eaton syndrome from myasthenia gravis. Lambert-Eaton syndrome occurs usually in the course of malignant diseases; when it seems isolated, a visceral neoplasm, mainly bronchogenic carcinoma, should be suspected. Nevertheless, in some cases, no malignant disease is found. The mechanism is a presynaptic block of neuromuscular transmission because of an unknown hypothetic substance produced by the tumor. Therapeutic resources (Guanidine) are scarce.