| Part ?:MRI study on the changes of total intracranial volume,gray matter,white matter and cerebrospinal fluid volume in people rapidly ascending to high altitudePurpose:Acute mountain sickness(AMS)is a common high-altitude disease,although its mechanism remains unclear.In this research,using 3D fast spoiled gradient recalled(3D-FSPGR)sequence,the changes of total intracranial volume,gray matter,white matter and cerebrospinal fluid volume in the people rapidly ascending to high altitude were investigated..Materials and Methods:A total of 47 healthy young volunteers(18-45 years old)living in the plain were enrolled in this study.Two 3D-FSPGR scans were performed with two MR scanners of the same type in plain(Beijing,50m)and high altitude(Lhasa,3650m)within 8±2 hours,and the Lake Louise Acute Mountain Sickness Score(LLS)was filled in after high altitude scanning.Based on SPM,voxel-based morphometry(VBM)technology was used to measure the total intracranial volume(TIV=gray matter volume+white matter volume+cerebrospinal fluid volume)and the volume of gray matter,white matter and cerebrospinal fluid.Paired t-test was used to compare the differences of brain volume between plain and high altitude in all subjects.According to LLS,volunteers were divided into AMS group and non-AMS group.Two independent samples t-test(excluding 2 singular values)was used to compare the difference of the ratio of brain volume change between the two groups.Pearson correlation analysis was used to analyze the correlation between the above changes in brain volume and the correlation between the above changes and the LLS.Result:47 subjects who were rushed to the high altitude showed a increase in TIVand gray matter volume(1562.90±138.83ml,718.39±46.50ml)compared with the plain(1555.48 139.87ml,703.05 48.88ml),and the difference was statistically significant(p=0.000,p=0.000).The volume of white matter and cerebrospinal fluid(310.93±45.27ml,314.61±46.99ml)compared with the plain(536.69±61.51ml,540.60±60.15ml)decreased,and the difference was statistically significant(p=0.027,p=0.045).After 2 outliers were removed by the normality test,the remaining 45 subjects were graded according to the LLS and 23 subjects were diagnosed as AMS.For the AMS group,the ratio of changes in TIV,gray matter and white matter volume(0.0061±0.0059,0.0286±0.0169,-0.0117±0.0151)was greater than that for the non-AMS group(0.0032±0.0055,0.0146±0.0191,-0.0036±0.0245).The change of cerebrospinal fluid volume in the AMS group(-0.0105±0.0272)was consistent with that in the non-AMS group(-0.0105±0.0426).Among them,the ration of gray matter volume change between the two groups was significantly different(p=0.012),while the ratio of TIV,white matter and cerebrospinal fluid volume change was not statistically significant(p=0.092,p=0.191,p=0.998).The change of gray matter volume was positively correlated with the change of TIV(r=0.564,p=0.000).The change of grey matter volume was positively correlated with the LLS score(r=0.469,p=0.001).There was a significant negative correlation between gray matter volume change and white matter volume change(r=-0.457,p=0.002).Conclusion:Acute exposure to high altitude with hypobaric hypoxic environment in a short period of time increase the TIV and gray matter volume,but decrease the volume of white matter and cerebrospinal fluid.The increased gray matter volume may be involved in the pathogenesis of AMS,which may provide a basis for further study of the pathology of AMS.Part ?:MRI Study of the changes of optic nerve sheath diameter in people rapid entry to high altitudePurpose:Increased intracranial pressure is an important theory of AMS,but it has not been utterly validated.The optic nerve sheath diameter(ONSD)can be used to reflect the condition of ICP.The study used 3D-FSPGR sequence to investigate changes in the optic nerve sheath diameter(ONSD)in people rapid entry to high altitude to assess correlation to acute mountain sickness(AMS).Materials and Methods:A total of 47 young healthy volunteers aged 18-45 years living in the plain were included in the study.Two 3D-FSPGR scans were performed with two MR scanners of the same type in plain(Beijing,50m)and high altitude(Lhasa,3650m)within 8±2 hours,and the Lake Louise Acute Mountain Sickness Score(LLS)was filled in after high altitude scanning.Using the obtained structure image on the GE AW46 workstation,to measure the bilateral ONSD at the position of 3 mm behind the eyeball while perpendicular to the optic nerve using electronic caliper.Two measurements were performed by one researcher at different times(3 days apart)using a blind method(the scanning sequence and subject's AMS status were unknown).3 subjects were not included due to head movement and technical reasons.Paired sample t test was used to compare the differences of the ONSD of 44 subjects between the plain and high altitude.According to the LLS,subjects are divided into AMS group and non-AMS group,and two independent sample t tests are adopted to compare the difference in the ratio of ONSD change between the two groups.Result:The mean ONSD of the 45(AMS 23 cases)subjects at high altitude(4.58±0.05mm,p=0.004),increased significantly compared with baseline(4.49±0.06mm).The ratio of ONSD changes in AMS group(0.035±0.056)and non-AMS group(0.008±0.033)was close to significant difference(p=0.063).Conclusion:High-altitude exposure leads to an increase in ONSD,suggesting an increase in ICP.However,the increase in ICP occurred in all people that entered the high altitude and did not have a definite correlation with the occurrence of AMS. |
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