Electrodiagnosis of botulism and clinico-electrophysiological correlation

ObjectiveAn electrophysiological study can help to confirm the diagnosis of botulism. This study was aimed at validating a simple and reliable electrodiagnostic test and at correlating the findings with clinical severity.MethodsPre- and post-exercise single supramaximal stimulations (SSSs) were performed in 63 patients with botulism. The sensitivity and specificity of amplitude of compound muscle action potential (CMAP) and percentage increment (PI) of SSS were determined. These two parameters were then correlated with respiratory failure. The relationship between the amplitude of CMAP and PI was also studied.ResultsSSS with a PI of 25% showed a sensitivity of 95.2% and a specificity of 100% in association with botulism. The area under the receiver operating characteristic (ROC) curve of CMAP and PI was associated with the respiratory failure by 0.7 and 0.6, respectively. An inverse relationship between the amplitude of CMAP and PI was also demonstrated.ConclusionsSSS is sensitive and specific in the diagnosis of botulism. There was some correlation of the findings with clinical severity. The inverse relationship between the amplitude of CMAP and PI reflects the pathophysiology of this disorder.SignificanceThis study has validated SSS as being a simple and reliable electrodiagnostic test for botulism.