Pathophysiology
1) paralyzing disease 2) cause is Clostridia botulinum neurotoxin, which is released through growth and autolysis of the microorganism 3) toxin acts on autonomic and voluntary nervous system to block release of acetylcholine at synapses
Signs and Symptoms
in adults – 1) difficulty swallowing 2) speech problems 3) double vision 4) flaccid paralysis 5) respiratory paralysis 6) cardiac arrest 7) dry mouth 8) dilated pupils (unlike myasthenia where pupils are always normal) 9) constipation 10) urinary retention 11) usually presents with cranial nerve involvement (ptosis) 12) can mimic and be confused with myasthenia gravis, tetanus, and Fisher variant of Guillain-Barre syndrome
Characteristic Test Findings
Laboratory – 1) toxin is detectable in the feces and serum 2) sometimes false-positive for Tensilon test for myasthenia EEG – 3) normal nerve conduction velocity 4) repetitive nerve stimulation gives incremental response (unlike myasthenia in which it is decremental)
Histology/Gross Pathology
1) anaerobic, gram-positive organism 2) spores widely distributed in soil
Biochemistry
prevents release of acetylcholine from presynaptic areas
Inheritance/Epidemiology
1) toxin enters body through ingestion of food (usually, but not always, home-canned, vacuum-packaged, or cured where C. botulinum is present and has produced toxin or via skin wound 2) infants – occurs in first months of life and is linked with ingestion of honey
Treatment
1) best if infection is prevented – the toxin is destroyed by heating for 20 minutes at 100C 2) trivalent equine antitoxin (against types A, B, E) given IV 3) stomach lavage/high-colonic enemas 4) guanidine HCL 5) mechanical ventilation if needed 6) if infected wound, the debridement, toxin, and penicillin topically
Tips for USMLE
1) there is no fever 2) there are no sensory disturbances and patients are mentally intact 3) paralysis is descending in nature (starts with head and moves to legs) 4) does not always leave infected food “spoiled” 5) patients almost always have ptosis 6) Fisher variant of Guillain-Barre (with descending paralysis) is distinguished from classic Guillain-Barre with ascending paralysis
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