Botulism

Early diagnosis of botulism is essential for effective treatment. Electroph ysiologic testing can be of major help to establish a prompt diagnosis, but the classic electrodiagnostic features of botulism are often elusive. Decr ement or increment of compound muscle action potential (CMAP) amplitudes to slow or fast rates of nerve stimulation are often unimpressive or totally absent. Reduction of CMAP amplitudes, denervation activity, or myopathic-li ke motor unit potentials in affected muscles are found more frequently but they are less specific. In general, the electrophysiologic findings taken t ogether suggest involvement of the motor nerve terminal, which should raise the possibility or botulism. The case reported here illustrates a common c linical presentation of botulism. This study emphasizes realistic expectati ons of the electrodiagnostic testing, the differential diagnosis, and the p otential pitfalls often encountered in the interpretation of the electrophy siologic data. (C) 2000 American Association of Electrodiagnostic Medicine.