[Neurogenic electromyographic activity in a patient with non-paraneoplasic Lambert-Eaton syndrome].

INTRODUCTION: Lambert-Eaton myasthenic syndrome (LEMS) is a rare presynaptic disorder of the neuromuscular junction. Electrodiagnosis is characterized by compound muscle action potentials of small amplitude at rest, normalizing immediately after brief exercise or high-rate nerve stimulation. Needle electromyographic (EMG) activity is classically described as normal or myogenic.

CASE: We report the case of a young patient with a non-paraneoplastic LEMS in whom the initial electroneuromyographic examination showed neurogenic changes in needle EMG concomitant with typical features of presynaptic neuromuscular junction disorder at single and repetitive nerve stimulation.

DISCUSSION: Neurogenic EMG abnormalities were not previously described in patients with LEMS and could result from "functional" reversible denervation, depending on the presence of anti-calcium channel antibodies at axon terminals.

CONCLUSION: Neurogenic features in needle EMG examination in case of subacute motor deficiency should not eliminate the possibility of a presynaptic neuromuscular junction disorder, such as LEMS.