Organophosphorus agent induced delayed neuropathy: a case report

Abstract

A 40-year old male, was presented with complaint of difficulty in walking with inability to flex foot and toes in bilateral feet (“foot drop”), which was acute at the onset and gradually progressive since the past 7 days. The patient’s wife and their 2 children had similar complaint with the same period of onset. At home, his family used cottonseed oil as cooking oil with wheat grain mixed with castor oil. On neurological examination, he was found to have lower motor neuron weakness with spasticity. After ruling out other common causes of polyneuropathy and lower motor weakness; due to high suspicion of poisoning by food adulterant, RBC acetyl cholinesterase (AChE) and plasma cholinesterase (BuChE) were tested at National Institute of Occupational Health (NIOH), which came low and confirmed diagnosis of Organophosphorus (OP) poisoning. Nerve conduction study was done; which showed decreased amplitude of conduction in bilateral peroneal and right tibial nerve along with decreased mean nerve conduction velocity of bilateral median nerve. Thus patient was diagnosed with organophosphorus agent induced delayed axonal type of polyneuropathy and physiotherapy was started as treatment. OP compounds are a diverse group of chemicals which are principally used as insecticides in agriculture. Following organophosphate poisoning (OPP), 3 well-defined neurological syndromes are recognised: cholinergic crisis, intermediate syndrome and delayed polyneuropathy. Some organophosphates, particularly triorthocresyl phosphate (TOCP) and tricresyl phosphate (TCP), produce delayed neuropathy. On ingestion, they do not produce significant cholinergic crisis, but 7 to 20 days later it leads to a pure motor axonal neuropathy with wrist and foot drop. The mechanism may involve inhibition of neuropathy target esterase (NTE), which is found in the brain, peripheral nerves, and lymphocytes. This form of toxicity has been seen occasionally in small epidemics in India due to adulteration of cooking oil with TOCP.