[Importance of electromyography in the diagnosis of botulism]

Botulism is a cause of neuromuscular transmission impairment. We report here an electrophysiological study of the neuromuscular junction in a patient presenting with botulism. Repetitive stimulation of a motor nerve showed a characteristic triad, indicating presynaptic block of neuromuscular transmission: the muscle action potential amplitude was low; repetitive high frequency stimulation (20 Hz) induced a more than 100% increment in the amplitude; low frequency repetitive stimulation (3 Hz) induced a more than 10% decrement in the amplitude. Progressive clinical improvement spontaneously occurred and the electrophysiological control recording that was done 1 month later was normal. Botulism toxin reduces acetylcholine quanta released in the autonomic and neuromuscular junction, causing presynaptic block. Electrophysiological recordings associated with clinical data contributed more to the diagnosis of botulism than serological analysis, which remained negative in this patients.