Pathogenesis and Pathophysiology. Botulism is the most potent poison known to man. It is produced by the spores of Clostridium botulinum. Three distinct varieties of the disease exist. Foodborne botulism results primarily from the ingestion of contaminated home-canned fruits and vegetables. Since this type of botulinum toxin is produced by spores that are already formed and ingested, toxic signs appear rapidly, usually between 8 and 36 hours after ingestion, and an incubation period is not required. After ingestion of the botulinum toxin, neurological signs appear within hours or at most 1 week. Wound botulism is both an infection and an intoxication. The organism enters through the wound site, and the spores may germinate locally in the tissues, producing a potent exotoxin. The third form of botulism is infantile botulism, which occurs in the first 6 months of life. It is related to the absorption of C. botulinum from the gastrointestinal tract. The basic pathophysiological mechanism of botulism neurotoxicity is inhibition of acetylcholine release.
Epidemiology and Risk Factors. Each year, approximately 20 cases of foodborne botulism in adults and 250 cases of infantile botulism are reported. Infantile botulism produces a very different clinical syndrome from that outlined below. This disease has been reported only within the last decade. Interestingly, botulinum toxicity has been offered as a possible explanation for the sudden infant death syndrome (SIDS). The age distribution is the same, and 10 infants with SIDS in California in 1977 also had evidence of intestinal infection with C. botulinum. Botulism may cause sudden infant death by producing flaccidity of the upper airway or tongue muscles, leading to airway obstruction during sleep. y
Clinical Features and Associated Findings. Early signs of toxicity include nausea and vomiting with abdominal pain, and diarrhea. Other symptoms include ptosis, extraocular paresis, and progressive weakness suggestive of myasthenia gravis. Cranial nerve symptoms most commonly involve the eyes. Additional symptoms include dryness of the mucous membranes, vertigo, deafness, dysphasia, swallowing difficulties, breathing difficulty that may lead to respiratory failure, speech impairment, absent or decreased gag reflex, and absent or decreased deep tendon reflexes. By the second to fourth day of the illness, muscular weakness develops. Often muscular involvement is limited to the neck muscles, resulting in an inability of the patient to raise the head. y
In infants symptoms consist of constipation, weakness with loss of muscle tone, and an alert but weak appearance.
Differential Diagnosis. Weakness can be differentiated from Guillain-Barre syndrome because the weakness associated with botulism toxicity is descending, so the proximal muscles are affected before the distal extremities. The progressive weakness is suggestive of myasthenia gravis; however, the pupillary dilation seen in botulism is not characteristic of myasthenia.
Evaluation. Confirmation of the diagnosis depends on detection of the toxin either in the patient (blood) or in the implicated food. A stool culture is often useful.
Management. Once the patient has been admitted to the hospital, respiration should be monitored. Trivalent ABE antitoxin is recommended.
Prognosis and Future Perspectives. In severe cases, a downward course is rapid and terminates in death. Death occurs in 70 percent of untreated cases. If the patient survives, recovery begins within a few weeks.
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