Botulism

Background

- sporeforming,m obligate anaerobe, gram positive

- lethal dose 1 ng/kg

- 1 gm can kill 1 million people

- blocks release of Ach from presynaptic membrane

- experimental vaccine

Symptoms

- symmetric, desc. paralysis w/B/L cranial nerve neuropathies (diplopia, dysarthria, ptosis)

- GI sxs: N/V, pain, late constipation

- Respiratory Failure

INFANT BOTULISM

- no honey or corn syrup to < 1 yo

- most cases < 1 y/o, 90% < 6mo

- most common form of botulism

- relative achlorhydia, poorly developed gut flora

- sxs from mild failure to thrive to sudden infant death

- drooling, ptosis, dilated/sluggish pupils, weak cry, feeding difficulties, constipation, resp arrest, poor head control, diminished muscle tone

WOUND BOTULISM

- black tar heroin, dirty wounds, C-section, tooth abscess, sinus infections

- incubation 10 days

- wound may appear benign

- GI sxs absent

Diagnosis

- clinically

- EMG studies: in botulism and Lambert-Eaton, few AcH released and muscle fibers don't reach threshold for contraction. With rapid nerve stim, can get enough AcH buildup in multiple muscle fibers to get "posttetanic facilitation."

- Nerve Conduction - normal in botulism (unlike GBS)

DDx

1. Myasthenia Gravis - EMG findings and antibody studies will differentiate (decremental response to repetitive nerve stimulation). CAN see false positive improvement to Tensilon test in botulism

2. Lambert-Eaton - spares resp muscles and primarily affects proximal lower limb muscles EMG findings similar to botulism (post-tetanic facilitation) but not identical

3. Guillain -Barre - Miller Fisher variant has prominent ataxia & areflexia that isn't seen in botulism. Nerve conduction tests are also abnormal

4. Poliomyelitis - usually have fever and asymmetric weakness. Ascending paralysis and CSF pleocytosis.

5. Tick Paralysis - ascending paralysis, abnl nerve cond tests

6. Diphtheria - proximal to distal spread of weakness 1-3 mo after fever and pharyngitis

7. Hyperthyroidism

8. Paralytic fish poisoning - tetrodotoxication (w/in 1 hr of fish eat)

9. Mg, mushroom or chemical (arsenic,thallium, anticholinergic) or meds (antichol, aminogly)

10. Sepsis

Workup

- Anaerobic cxs: emesis, gastric fluid, stool, food, wound, serum

- EPS - EMG shows decr amplitude with post-tetanic facilitation Nerve conduction normal

Treatment

- Ventilatory support: Intubate when VC < 30% predicted or < 12 cc/kg

- Foodbrone: antitoxin and AC, consider cathartics

- Infant: supportive care only, no benefit from antitoxin or Abx

- Wound: antitoxin, Td, wound irrigation & debridement even if appears well. Pen G 10-20 mill units/day.