Electrodiagnosis of infantile botulism.

Analysis of the literature on the electrophysiologic features of infantile botulism was undertaken. Small compound muscle action potential amplitude is a very sensitive feature but lacks specificity. The decremental response to 2- to 3-Hz repetitive nerve stimulation is inconsistent and not a reliable sign. Tetanic and posttetanic facilitation are highly sensitive and highly specific. Absence of posttetanic exhaustion is also highly specific for infant botulism and shared only by hypermagnesemia. We conclude that the findings of low compound muscle action potential amplitude in combination with tetanic facilitation or posttetanic facilitation and absence of posttetanic exhaustion constitute the triad on which the electrodiagnosis of infantile botulism can be supported.