Electrophysiological changes in patients with acute organophosphorous pesticide poisoning

Organophosphorous pesticides (OP) are widely used in agriculture without proper control in the Islamic Republic of Iran and thus OP poisonings are common in this country. Epidemiological and management aspects of OP have been studied in detail, but there have been very few reports on peripheral polyneuropathy, particularly electrophysiological changes related to this poisoning. Thus, we aimed to study electrophysiological changes including electromyography (EMG) and nerve conduction velocity (NCV) in patients with OP poisoning. The patients with acute moderate to severe OP poisonings who revealed clinical symptoms and signs of peripheral polyneuropathy after recovery of the acute phase of intoxication were investigated from 2005 to 2006 in Mashhad, Iran. These patients lacked previous neurological problems and had not been chronically exposed to OP. EMG and NCV were performed using MEDELEC MS92 & TOENNIES Multiliner E. Statistical analyses including Student's t-test and Pearson's test were applied using SPSS (Version 11.5). Of 342 hospitalized patients, eight patients (four females and four males) aged 13-59 years were investigated. Intervals between the onset of OP poisoning and electrodiagnostic tests varied between 10 and 210 days. On EMG, there was a sensory-motor peripheral polyneuropathy, which was predominantly a distal sensory deficit. Sensory nerve dysfunction (84.4%) was significantly higher (p < 0.001) than motor dysfunctions (18.7%). The lower extremities, particularly tibial and peroneal nerves, were more affected than the upper extremities (p < 0.0001). Sensory nerve dysfunction of the lower extremities was more common than motor nerves, which was predominantly a distal sensory deficit.