Brain injury due to acute organophosphate poisoning: Magnetic resonance imaging manifestation and pathological characteristics

Abstract

Background Acute organophosphate poisoning can cause injuries of multiple visceras; especially, central nervous system injury can increase risk factors of patients with severe acute organophosphate poisoning. An application of modern image may increase diagnostic rate of brain injury in an earlier period and provide evidences for clinical treatment. Objective To reveal imaging manifestations, pathological characteristics and multi-ways injured mechanism of brain injury due to acute organophosphate poisoning. Design Contrast observational study. Setting Department of Medical Image, the Second Hospital of Hebei Medical University. Materials The experiment was carried out in the Department of Nerve Molecule Imaging Medicine and Laboratory of Neurology, the Second Hospital of Hebei Medical University from August 2003 to February 2004. A total of 30 healthy cats weighing 2.8–3.5 g and of both genders were selected from Animal Experimental Center of Hebei Medical University. Methods Thirty healthy cats were randomly divided into control group ( n =5) and intoxication group ( n =25). Cats in the control group were subcutaneously injected with 0.3 mL/kg saline at four points; while, cats in the intoxication group were subcutaneously injected with 400 g/L 0.3 mL/kg O,O-dimethyl-S-(methoxycarbonylmethyl) thiophosphate at four points. Two minutes after intoxication, cats received muscular injection with 0.5 mg/kg atropine sulfate, and then, brain tissues were collected from parietal lobe, basal ganglia, hippocampus, cerebellum and brain stem were observed at 3, 6, 24 hours, 3 and 7 days after intoxication respectively under optic microscope and electron microscope and expressions of acetylcholinesterase (AChE), choline acetyltransferase (ChAT), glial fibrillary acidic protein (GFAP), glutamic acid (Glu) and γ-amino butyric acid after immunohistochemical staining. Main outcome measures Results of MRI examinations; histological changes under optic microscope and electron microscope; expressions of AChE, ChAT, GFAP, Glu and γ-amino butyric acid after immunohistochemical staining. Results All 30 healthy cats were involved in the final analysis. ▪ Imaging and pathological observation: Image manifestations of brain injury induced by acute organophosphate poisoning showed as cerebral edema and symmetry signal abnormality of bilateral basal ganglia; while, pathological manifestations also showed as cerebral edema. ▪ Observation of immunohistochemical staining: As compared with the control group, after organophosphate poisoning, area of AChE immune-positive cells was decreased obviously ( P < 0.01), but area of ChAT immune-positive cells was not changed ( P > 0.05); in addition, positive cells of GFAP were increased remarkably ( P < 0.01), positive cells of γ-amino butyric acid in cerebral cortex were increased obviously ( P < 0.05), but numbers of positive cells of Glu were not changed ( P < 0.05). Conclusion Multi-ways injured mechanism invovled in acute organophosphate poisoning. An application of modern image can increase diagnostic rate of brain injury in an earlier period and provide evidences for clinical treatment.