| Objective: To retrospective analysis of the brain MRI images in patients with acute carbon monoxide poisoning, and the brain MRI abnormalities of acute carbon monoxide poisoning were recorded; by clinically follow-up examination, patients with delayed encephalopathy after acute carbon monoxide poisoning confirmed were subsequently evaluated. And the predictors of the development of delayed encephalopathy after acute carbon monoxide poisoning on MRI image were discussed.Material and methods: 61 patients with acute carbon monoxide poisoning and 50 healthy volunteers were enrolled into our study and served as experimental and normal control groups. All patients underwent T1 weighted, T2 weighted, T2 FLAIR and diffusion weighted imaging sequences, the average ADC values of cortical areas (Bilateral frontal cortex,parietal cortex), semioval center, periventricular white matter (Bilateral lateral ventricle side, anterior horn of lateral ventricle, posterior horn of lateral ventricle), globus pallidus in each patients were measured. All patients with acute carbon monoxide poisoning were acute carbon monoxide poisoning group, according to the severity of poisoning is divided into mild, moderate, and severe levels;According to presences or absences of signal abnormalities on MR imaging, patients in e acute carbon monoxide poisoning group were subsequently divided into two subgroups: abnormal and normal signal groups. And according the development of delayed encephalopathy after acute carbon monoxide poisoning, patients were subsequently divided into two subgroups: delayed encephalopathy and non-delayed encephalopathy groups. The average ADC values between groups (acute carbon monoxide poisoning group and normal control group, abnormal signal group and normal control group, normal signal group and normal control group, abnormal signal group and normal signal group, delayed encephalopathy group and non-delayed encephalopathy group) were then compared by using independent sample student's t tests (The probability value of less than 0.05 was considered to indicate a significant difference).Results: In the group of acute carbon monoxide poisoning, mild poisoning were found in 20 cases, moderate poisoning in 27 cases and severe poisoning in 14 patients. MR imaging were normal in 23 patients (37.7%, including 20 patients with mild poisoning and 3 with moderate poisoning); MR findings were abnormality in 38 patients (62.3%, including 3 patients with moderate poisoning and 14 patients with severe poisoning), The bilateral white matter regions, bilateral globus pallidus and cortical involvement were noted in 13 cases (21.3%), 21 cases (34.4%) and 4 cases (6.6%), respectively. MR abnormalities were most seen in patients of moderate and severe poisoning, and the globus pallidus and white matter areas were the most common region of involvement. The signal characterization of MR abnormalities were as follows: low signal observed in T1WI, high signal s observed in T2WI, T2FLAIR and DWI in 25 patients; slightly low signal observed in T1WI, slightly high signals observed in T2WI, T2FLAIR and DWI in 13 patients;normal signal observed in T1WI,T2WI, T2FLAIR and DWI in 23 patients. In the study of ADC values:the average ADC value were measured in normal control group and the average ADC value in the region of cerebral cortex, semioval center, perventricular white matter and globus pallidus were (1.155±0.062)×10-3, (0.745±0.026)×10-3, (0.775±0.031)×10-3 and (0.764±0.015)×10-3 mm2 / s, respectively. The comparison of average ADC value between acute carbon monoxide poisoning group and normal control group in the same region: the statistical differences in average ADC value were observed in the region of cerebral cortex, semioval center, periventricular white matter and globus pallidus,the average ADC values in acute carbon monoxide poisoning group were lower compared with that in normal control group [average ADC values of each region in acute carbon monoxide poisoning group were (1.115±0.070)×10-3, (0.721±0.046)×10-3, (0.743±0.043)×10-3 and (0.747±0.351)×10-3 mm2 / s, respectively, and t values were 3.126, 3.338, 4.459 and 3.159, respectively, p <0.05].The comparison of average ADC value between abnormal signal group and normal control group in the same region: the statistical differences in average ADC value were observed in the region of cerebral cortex, semioval center, periventricular white matter and globus pallidus , the average ADC values in abnormal signal group were lower compared with that in normal control group [average ADC values of each region in abnormal signal group were (1.115±0.079)×10-3, (0.716±0.056)×10-3, (0.735±0.053)×10-3, and (0.742±0.041)×10-3 mm2 / s, respectively, and t values were 2.695,3.247,4.494, and 3.528, respectively, p <0.05].The comparison of average ADC value between normal signal group and normal control group in the same region: the statistical differences in average ADC value were observed in the region of cerebral cortex, semioval center and periventricular white matter, the ADC values in normal signal group were lower compared with that in normal control group;the no statistical differences in ADC value were observed in the region of globus pallidus [average ADC values in the region of cerebral cortex, semioval center and periventricular white matter in normal signal group were (1.116±0.056)×10 -3, (0.728±0.023)×10-3 and (0.756±0.013)×10-3 mm2 / s, respectively, and t values were 2.558, 2.691 and 2.914, respectively, p <0.05;average ADC values in the region of globus pallidus was (0.756±0.022)×10-3 mm2 / s, and t values was 1.905,p>0.05].The comparison of average ADC value between abnormal signal group and normal signal group in the same region: no significant differences in the average ADC values were observed in the region of cerebral cortex, semioval center, periventricular white matter and globus pallidus(t values were -0.080,-0.965,-1.842,-1.488,respectively,p>0.05), however, according to the region of cerebral cortex, semioval center, periventricular white matter and globus pallidus with abnormal signal change in a separate statistical analysis were all statistically significant, the average ADC values were reduced significantly than that in normal signal group. 19 cases (31.1%) were progressed to delayed encephalopathy after acute carbon monoxide poisoning; and the regions occurred abnormalities were as follows: cerebral cortex in 4 cases, white matter regions in 7 cases, and globus pallidus in 8 cases; the incidence of development delayed encephalopathy after acute carbon monoxide poisoning in the region of cerebral cortex, cerebral white matter and globus pallidus were 100%, 53.8% and 38.1%, respectively. The comparison of average ADC value between delayed encephalopathy group and non-delayed encephalopathy group in the same region: the statistical differences in average ADC value were observed in the region of semioval center and periventricular white matter, the average ADC values in delayed encephalopathy group were significantly lower than that in non-delayed encephalopathy group; no statistical differences in average ADC value were observed in the region of cerebral cortex and globus pallidus[average ADC values of semioval center and periventricular white matter in delayed encephalopathy group were (0.703±0.065)×10-3 and (0.719±0.068)×10-3 mm2 / s, respectively; and in non-delayed encephalopathy group were (0.729±0.036)×10-3 and (0.754±0.019)×10 -3 mm2 / s. t values were -2.113 and -3.057, respectively, p <0.05; average ADC values of cerebral cortex and globus pallidus in delayed encephalopathy group were (1.097±0.087)×10-3 and (0.747±0.043)×10-3 mm2 / s, respectively; and in non-delayed encephalopathy group were (1.124±0.061)×10-3 and (0.748±0.032)×10 -3 mm2 / s. t values were -1.416 and -0.128, respectively, p >0.05].Conclusion: Based on the MRI images of patients with acute carbon monoxide poisoning, the MRI findings of acute carbon monoxide poisoning can be classified into 4 following types:①no definite abnormality;②bilateral globus pallidus involvement;③cerebral white matter involvement;④cerebral cortex involvement. Patients with severity clinical symptoms had more opportunity to present abnormality on MR image, and bilateral globus pallidus and cerebral white matter involvement are most common abnormalities. In patients with clinical symptoms but have no abnormal signal change on conventional MR images, the ADC values is sensitive for detection acute carbon monoxide poisoning, ADC value measurement is a quantitative method of poisoning, It can be used as a reference for clinical treatment. Patients with extensive involvement of cerebral white matter or cerebral cortex suggested more incidence of developing delayed encephalopathy after acute carbon monoxide poisoning. Patients with severe clinical symptoms and had MRI abnormalities and significantly decreased in ADC values significantly associated with development of delayed encephalopathy after acute carbon monoxide poisoning on clinical.
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