Diagnostic aspects of botulism

Based on four cases, diagnostic aspects of botulism are presented. Botulism must be diagnosed initially on the basis of the history and physical findings but electrophysiologic studies are often helpful for the establishment of the diagnosis. Conventional neurophysiologic testing with neuro- and myography has low sensitivity. However, the neurophysiological studies on neuromuscular transmission showed abnormalities in most of the cases. A review of 4 own and 15 previously published cases showed an inconsistency with the typical electrophysiological pattern of botulism, described in some text-books of neurophysiology: The "classical" finding of a decrement in low-rate repetitive stimulation (3 - 10 Hz) accompanied by an increment in hi.-h-rate repetitive stimulation (20 - 50 Hz) occurred in only 10,5% of the cases; whereas, normal results for the low-rate repetitive stimulation and an increment for the high-rate stimulation were found in 53% of the cases with documented botulism. In summary more than 63% of patients showed an incremental response in high frequently repetitive stimulation. We postulate a higher sensitivity of the high-rate stimulation in opposite to the low-rate stimulation. However, single-Fiber electromyography has the highest diagnostic sensitivity, but the feasability of this method is limited in the acute phase of the disease.