Acute Organic Phosphorus pesticide poisoning caused by myasthenia as a prominent manifestation of the syndrome, because of its onset time in acute cholinergic crisis and delayed multiple peripheral neuropathy, Senanayake and Karalliedde named it as an intermediate syndrome.
China's Ministry of Health in 1987 issued a national diagnostic criteria for occupational organic phosphorus poisoning (GB-7794287), but did not include the diagnosis of IMS. In 1989, China began to report IMS, to June 2000 has 147 cases. But there are still some acute Organic Phosphorus poisoning delayed respiratory failure, failed to timely diagnosis of IMS.
In 2002, China's Ministry of Health on April 8 issued GBZ8-2002 "occupational acute Organic Phosphorus pesticide poisoning diagnostic criteria", revised the standard comprehensive summary of the organic phosphorus insecticide on the nervous system toxic effects of three clinical Performance: inhibition of acetylcholinesterase in vivo caused by acute cholinergic excitability or crisis; manifested as muscarinic, nicotine and central nervous system symptoms; intermediate myasthenia gravis, manifested as the neck and proximal limb Muscle, innervation of the muscles, as well as the muscle strength of the muscle weakened or paralysis; delayed multiple peripheral neuropathy, the performance of the distal limb for the heavy movement and sensory disturbances. At this point in our IMS officially named "intermediate muscle weakness syndrome." But foreign scholars still follow the "IMS" name, has not yet recognized "intermediate muscle weakness syndrome" formulation.
IMS pesticide varieties
It is not known whether the pesticide varieties of IMS are selective. According to the clinical data in recent years, the Organic Phosphorus pesticides caused by IMS are more common in dimethoxy compounds. Foreign more common in the sub-agriculture or fenthion phosphorus poisoning, domestic more common in dimethoate, omethoate, dichlorvos, parathion and methamidophos poisoning, IMS did not seem to be related to the structural characteristics of some Organic Phosphorus compounds, physical and chemical properties And biological activity. In recent years, more and more mixed pesticide poisoning reports, according to the epidemic survey, the high incidence of pesticide poisoning Shandong Jiaxiang County and Jiangsu Rudong County, a total of 2179 mixed pesticides (organic phosphorus + pyrethroid vinegar) The poisoning rate of mixed pesticide was 10.10%, which was significantly higher than that of single pesticide group (2.29%), the former was 3.5 times of that of the latter. The main component of mixed pesticide was Organic phosphorus, the vast majority of mixed with a toxic effect or synergistic effect, so organic pesticide poisoning pesticide poisoning should be more alert to the emergence of IMS.
The exact pathogenesis of IMS has not yet been elucidated, there are a variety of theories trying to clarify the pathogenesis, but there are shortcomings, to be further studied.
1. Neuromuscular transmission dysfunction theory At present, many studies support the occurrence of neuromuscular junctional transmission dysfunction related to the theory of the points are summarized:
(1) Pathological changes of the postsynaptic membrane: In 1987, Senanayake et al., In their first report, suggested that the occurrence of IMS was associated with pathological changes in the posterior synaptic membrane striatum. Because of the Organic Phosphorus pesticide poisoning induced myasthenia in rabbits and rats and other animal experimental model appeared in a similar pathological changes.
Â '¢ presynaptic membrane of nicotinic acetylcholine receptor damage: In 1997, Sedgwick and other further improve this theory, proposed synaptic membrane acetylcholine receptor function down and desensitization can explain the occurrence of IMS. In recent years, the molecular mechanism studies have found that skeletal muscle type postsynaptic membrane of the nicotinic acetylcholine receptor is the neuromuscular junction of the postsynaptic membrane on the chemical signal into an electrical reaction signal molecules. Organic phosphorus can inhibit acetylcholinesterase, so that the presynaptic nerve endings release of acetylcholinesterase in synaptic space accumulation, causing synaptic continuous excitement, leading to the postsynaptic membrane of the nicotinic acetylcholine receptor desensitization.