Epidemiology: toxin produced by spores of Clostridium botulinum. Exposure risks: inadequately cooked food; contamination of anaerobic wounds; ingestion or inhalation of spores; intestinal surgery; gastric achlorhydria; antibiotic therapy. May appear at any age.

Pathogenesis: toxin disrupts exocytosis without causing cell death. Effects slowly disappear over several months.

Laboratory data: EMG: abnormally small single muscle action potential evoked in response to supramaximal nerve stimulus; potentiation of response with repetitive stimulation at high rates (20 to 50 Hz), similar to Lambert-Eaton myasthenic syndrome.