Botulism

Botulinum toxicity stems from toxins produced from Clostridium botulinum, of which there are seven types (A – G). In our diagram, we show ptosis and flattened facies and a downward arrow to indicate the characteristic descending flaccid paralysis that occurs. Botulinum toxicity causes oculbulbar and facial weakness, specifically there is ptosis, facial and extraocular movement weakness, and dysarthria/dysphagia. This manifests with eyelid drooping, diplopia, limitation of extraocular mobility, expressionless (flat) facies, and choking and regurgitation. Flaccid paralysis follows the oculobulbar weakness and that the weakness begins proximally in the neck and shoulders before it extends distally along the upper extremities and that it subsequently develops in the pelvis and thighs before it descends down the lower extremities. Respiratory arrest can occur from diaphragm (and accessory muscle) failure in combination with the pharyngeal weakness. From an autonomic standpoint, the blocking of cholinergic transmission results in constipation and mydriasis (pupillary widening) from parasympathetic inhibition and hypohidrosis from inhibition of post-ganglionic cholinergic sympathetic fibers. For comparison, in myasthenia gravis there is minimal autonomic nervous system dysfunction, in LEMS there is a fair amount of dysfunction, and botulinum toxicity there is considerable autonomic disturbance. Many causes of botulinum toxicity exist, including:

• Foodborne botulism.
• Contaminated foods produce toxin in an anaerobic milieu.
• Wound botulism.
• Environmental spores germinate and produce toxin in an anaerobic abscess.
• Infant botulism.
• Intestinal colonization can occur in infants because they lack the normal bowel florae necessary to compete with C. botulinum. Note that this can occur in adults with excessive antimicrobial use or functional bowel abnormalities, as well.
• Inhalational botulism.
• Deliberate aerosolization of botulism toxin (which is not a naturally occurrence) is a potential bioterrorism weapon.
• Iatrogenic botulism.
• Rarely, intramuscular botulism injection can result in systemic botulism.

Laboratory confirmation requires demonstration of toxin in serum or stool (or gastric secretions). An absent sweat reflex can also be identified. Botulism anti-toxin and supportive care are the key treatment modalities. Consider that botulism toxin binding is noncompetitive and irreversible, however, and that the anti-toxin must be delivered early to be effective. Fortunately, however, with good intensive care support, patients can survive and within weeks to months, with ample time for nerve terminal regeneration, ~ 95% of patients will recover.