Long-term event-related potential changes following organophosphorus insecticide poisoning

Objective To determine prolonged effects of organophosphorus (OP) insecticide poisoning on cognitive event-related potentials (ERPs). Methods ERPs of a group of 32 patients recovered from cholinergic phase of OP insecticide poisoning were compared with those of two matched control groups: 32 healthy volunteers and nine patients hospitalised with paracetamol overdose. A follow-up assessment was done in 21 patients (66% of the initial sample) 6 months after OP intoxication and the findings were compared with their initial ERP data. Results Patients showed highly significant prolongation of P300 latency, compared to healthy controls (p = 0.003) and the controls with paracetamol overdose (p = 0.016). Follow-up ERP findings of the patients revealed that this impairment remained unchanged even 6 months after OP poisoning (p = 0.790). There was no significant difference in N100, P200 and N200 latencies or P300 amplitude either among the groups or between the two assessments of the patients with OP poisoning. Conclusions Our results suggest that acute OP poisoning causes a delay in cognitive processes involved in stimulus classification, lasting at least for 6 months. Significance These findings highlight the possibility of development of long-lasting cognitive deficits following OP insecticide poisoning, and warrant longer-term prospective studies to determine whether this impairment is permanent.