INTERMEDIATE MYASTHENIA SYNDROME FOLLOWING ACUTE ORGANOPHOSPHATES POISONING - AN ANALYSIS OFF 21 CASES

1 Twenty-one cases out of 272 patients of acute organophosphates poiso ning were diagnosed as intermediate syndrome (IMS) with a prevalence a t 7.7%. The responsible OP insecticides included parathion, omethoate and some OP containing pesticide mixtures, IMS occurred mainly in seve re OP poisoning patients who recovered from the acute cholinergic cris is at 7-75 h after the onset of acute poisoning. 2 Muscular weakness a ppeared in the following three categories of muscles: (1) neck flexors and proximal limb muscles; (2) muscles innervated by motor cranial ne rves and/or (3) respiratory muscles. Blood acetylcholinesterase activi ty was persistently inhibited, Electroneuromyography (ENMG) with repet itive nerve stimulation (RNS) at frequencies of 20 Hz or 30 Hz in seve n patients shouted decrements of common muscle action potentials durin g the presence of myrasthenia in five patients and became normal when their muscle strength recovered. 3 Mild IMS recovered within 2-7 days and had a favorable prognosis. Severe IMS patients with respiratory pa ralysis needed immediate endotracheal intubation and mechanical ventil ation. Recovery of weakness of the respiratory muscles and proximal li mb muscles took longer, the slowest being 30 days. Four of the patient s died of respiratory paralysis and the fatality rate was 19%. 4 The m echanism of IMS remains to be further investigated. The RNS/ENMG chang es indicate a postsynaptic block at the neuromuscular junctions. 5 In order to promote the recognition of this syndrome, we proposed to name the syndrome as Intermediate Myasthenia Syndrome (IMS).