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Progressively stronger pupillary constriction occurs with very frequent stimulations because of the additive effect of acetylcholine at the postsynaptic region. This additive effect occurs when the interval between the release of acetylcholine is significantly less than the time it takes for acetylcholine to be destroyed in the cleft. Progressively weaker pupillary constriction occurs with infrequent stimulation because repetitive stimulation at a slow rate does not have this additive effect.
Seizures may occur in neonates with botulism and are often due to hyponatremia (which results from inappropriate secretion of antidiuretic hormone) or asphyxia. Classic electrodiagnostic findings are an incremental response in muscle action potential produced by very frequent repetitive nerve stimulation (20 to 50 Hz) and abundant brief and small polyphasic motor unit and fibrillation potentials. These findings are not present in all cases, therefore, their absence does not exclude infantile botulism. The diagnosis of botulism rests on finding C botulinum in the stools. Treatment with human botulism immune globulin is effective. Supportive treatment is needed. Infantile botulism is a self-limiting disease that lasts from 2 to 8 weeks.

Hypermagnesemia
Hypermagnesemia produces hypotonia, weakness, abdominal distention, absent bowel sounds, and constipation. It usually occurs in newborns after the mother has received a large amount of intravenous magnesium sulfate. It is a presynaptic defect. The diagnosis is confirmed by a serum magnesium level above 4.5 mEq/L. Treatment is supportive. Exchange transfusion may help in very severe cases.

Aminoglycosides Therapy
Aminoglycosides produce weakness, hypotonia, dilated pupils, atonic bladder, and paralytic ileus. Treatment consists of elimination of antibiotics and support. Hypotonia due to aminoglycoside therapy occurs more frequently in neonates with other disorders that affect the myoneural junction; therefore, the use of aminoglycosides in a neonate with a disorder of myoneural junction involvement should be avoided.

 

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Thompson, 1980 Pickett, 1976 Lipsitz, 1967