11.5. Botulism
- General features:
- Neurotoxin is derived from the bacterium (Clostridium Botulinum)
- Anaerobic and alkaline conditions for growth
- Spores are heat resistant; temperatures of 120o C are required for sterilization; 85o C inactivates the toxin
- High altitude cooking (water boils at lower temperature and does not inactivate spores; inadequate sterilization of canned foods)
- Eight antigenic types of botulinum toxins: A, B, C1, C2, D, E, F, G; Zinc-dependent endopeptidase
- Human disease caused by A, B, E
- Fatal dose 0.05–0.1ug
- 250 cases of botulism/year in the USA
- Type A: Western USA
- Type B: Eastern USA, Europe
- Type E: from fish, more prevalent in Japan (20% of USA patients)
- Ingested toxin from food (USA)
- Vegetables – 57%
- Fruit – 12%
- Fish – 15%
- Infantile form of the toxin is produced by organisms in the GI tract
- Wound infection as a source of poisoning is becoming rare
- Mechanism of action: enters the axon terminal by endocytosis
- Toxins A, C, E-cleave synaptosomal protein-associated protein (SNAP-25)
- Types B, D, F and G-cleave synaptosomal-brevis associated membrane protein
- Type C-cleaves syntoxin
- Clear sensorium; no sensory loss
- Constipation, dry mouth, postural hypotension dilated poorly reactive pupils; internal and external ophthalmoplegia
- Initial nausea, vomiting, diarrhea followed by constipation
- Once process is initiated there is no fluctuation of symptoms
Differential Diagnosis of Botulism vs GQ1b CMS
- GBS (C.M. Fisher variant) G Q 1b (Ab); absent DTRs
- Pharyngeal-cervical brachial variant (GBS); GT1a (Ab)
- Lambert-Eaton Syndrome (increase reflexes and strength with exercise)
- MG (pupils normal)
- Tick paralysis (ataxia with weakness)
- Toxic shell fish (pain at site of envenomation)
- Diphtheritic neuropathy (sore throat)
Infant Botulism
- General features:
- Spores are ingested and germinate in the infant GI tract
- Honey consumption is a risk factor; Type B > A organisms
- Clinical presentation:
- Affects infants less than six months
- Weak cry difficulty feeding
- Weakness of bulbar and limb muscles. Hypotonia loss of head control, decrease of spontaneous movements
- Parasympathomimetic symptoms
Wound Botulism
- General features:
- Primarily in IV drug abuse patients (abscesses)
- Sinusitis in cocaine users
- Clinical presentation:
- Patient with a wound
- Bulbar signs and descending paralysis
Hidden Botulism
- General Features:
- No obvious source of toxin
- Abnormality of GI tract as risk factor such as achlorhydria, surgery, Crohn's disease, recent antibiotic treatment
- Clinical Presentation:
- Similar to chronic form
- C. botulinum in feces of an adult patient
Iatrogenic Botulism
- General Features:
- Toxin injected for movement disorder
- Clinical Presentation:
- Standard doses had been given to patients
- Moderate clinical weakness
- Autonomic symptoms in some patients
- Laboratory Evaluation
- Detection of C. botulinum in the stool or toxin in the serum, stool or wound
- Evaluation of food for bacteria and toxin
- Serum samples need to be collected by two days after ingestion; stool samples by three days
- EMG:
- Prolonged jitter and increased block on single fiber studies at a distance from the injection site
- Small evoked CMAP from single supramaximal stimuli in affected muscles
- Normal sensory (SNAP), velocities and latency
- Normal mNCV
- After exercise CMAP may increase
- Post tetanic facilitation noted in some patients
- Increased brief polyphasic motor unit potentials and fibrillation potentials
- Single fiber EMG: increased jitter and blocking
- General clinical features suggestive of a CMS
- Onset in infancy or childhood of ocular, bulbar or limb, muscle fatigueable weakness
- Involved relative may be isolated)
- Some have late onset
- Weakness in selected muscles
- EMG evaluation
- a) Decremental response at 2–3 HZ on repetitive nerve stimulation
- b) May be positive in restricted muscles or only intermittently
- No anti-acetylcholine receptor antibodies
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