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Infant Botulism

Botulism is an acute descending flaccid paralysis that results from ingestion or absorption of the neurotoxin from Clostridium botulinum that blocks the neuromuscular transmission. Three clinical variants are recognized; food poisoning from ingestion of contaminated canned food, mainly home processed foods, the most important food vehicles are vegetable, fish, fruits and condiments. Wound botulism from a contaminant local infection.

Infant botulism is the most common variant and the most recently recognized (1976). Seven immunologic types of C-botulism have been identified, designated A through G, each elaborating an immunologically distinct toxin. Almost all human botulism have resulted from ingestion of toxins A,B and E, the latter usually associated with fish and marine mammal products.

Recently, a case of infant botulism with clostridium botulinum type C has been described. The illness in infants is caused by the release of toxin produced in the intestinal tract by clostridium botulinum as opposed to classic botulism, which is caused by absorbed preformed toxins from the intestine or an infected wound. The toxin binds irreversibly to the synaptic membrane of cholinergic nerves and subsequently prevents the release of acetylcholine. The autonomic nervous system dysfunction occurs first followed by motor weakness. Recovery occurs when sufficient new, toxin free receptors are available at the neuromuscular junction. Because the toxins bind at all ganglionic and postganglionic parasympathetic synapses, the typical signs consist of weakness in the distribution of both peripheral and cranial nerves, constipation and autonomic instability.

The most unique epidemiologic feature of infant botulism is its age distribution, which, perhaps coincidentally, is virtually identical to the age distribution of SIDS. All cases of infant botulism reported so far occurred in children less than one year of age. Some 95% of cases occur in the first 6 months of life. The remaining 5% are distributed over the subsequent 6 months.

The illness has occurred in all major racial and ethnic groups in equal proportions in males and females. The diagnosis should be considered as a possibility in any season of the year given a compatible history. The illness occurs with an increased frequency in California, Utah and Southeastern Pennsylvania. Studies have identified an association between being breast-fed and being hospitalized for infant botulism. One perspective suggested that breast feeding predisposes to illness, however all other studied revealed that breast feeding slows onset sufficient to permit hospitalization to occur.

Honey is the one dietary reservoir of C. botulinum. So far, corn syrups do not constitute a source of C. botulinum spore or a meaningful risk factor for infant botulism. Besides honey, the soil in Pennsylvania, the soil and cistern water in Australia and the soil and vacuum cleaners in California were also identified as a source of spores. However, for the majority of infant botulism, no source of spores is ever identified.

Infant botulism may be difficult to recognize in its early stages, and even today, the most common admitting diagnosis is "rule out sepsis." It usually displays a spectrum in its clinical severity. Almost all recognized cases have been sufficiently hypotonic and weak toward hospitalization. The onset of infant botulism ranges from insidious to abrupt. In the classic case the first sign of illness is almost always constipation, yet the constipation is often overlooked. Less than 5% will present without constipation.

The mother usually notices listlessness, lethargy and poor feeding. The weakness increases over 1 to 4 days. The descending paralysis is symmetrical. The first signs of the illness are in the cranial nerves. The typical patient has expressionless face, a feeble cry,poor head control,, and generalized weakness and hypotonia. The gag, suck, and swallow reflex are impaired as well as the corneal reflex if tested repetitively. Deep tendon reflex are normal initially and diminished subsequently as the paralysis extends and increases. The "frog leg" sign is also seen.

EMG offers rapid bedside confirmation of the clinical diagnosis. It shows a pattern of brief, small, abundant motor unit potential. The definite diagnosis is the examination of feces for the organism and toxin.

The management consists of meticulous supportive care and the anticipation and avoidance of fatal complication (see Table). An endotracheal tube is often needed to maintain and protect the airway, even in the absence of mechanical ventilation. A new potential treatment may be the human derived botulism immune globulin (BIG). This regimen remains in clinical trial at this point.

The parents need to understand that the clinical course is reliable for small improvements and deterioration. Movement of the fingers provides an early sign of returning muscle strength and is closely followed by incomplete eye opening. Return of a weak cough and improvement in swallowing will be accompanied by decrease in need for suctioning. When the strength of cough improves and suction becomes unnecessary, the patient can be safely extubated.

In the absence of hypoxic cerebral complications, full and complete recovery of strength and tone is expected. Since the toxin does not cross the BBB to any functional degree, the intelligence and personality remain unaffected. Reinfection with the same or different toxins does not occur.

At present, the recommendation is to avoid feeding honey to infants, and breast feeding may help moderate the rapidity of onset and severity of illness.