Dystonic reaction possibly induced by cholinesterase inhibitor insecticides.

A 39-year-old male presented to the emergency room following parenteral injection of a household insecticide. The patient suffered from delayed, local complications as well as a dystonic-like reaction involving the neck musculature that was relieved by intramuscular diphenhydramine. Exposure to cholinesterase inhibitor insecticides has been associated with a number of serious toxicities due to accumulation of acetylcholine at various sites. It has been suggested that dystonic reactions are caused by an imbalance between cholinergic and dopaminergic pathways in the central nervous system. Therefore, a possible explanation of the dystonic reaction in this case is the increased cholinergic activity relative to dopaminergic activity induced by the insecticide.