Application Of Diffusion Spectrum Imaging In White Matter In Idiopathic Normal Pressure Hydrocephalus

Objective:The purpose of this study was to measure the diffusion spectrum imaging（DSI）parameters of corticospinal tracts（CSTs）and regions of bilateral periventricle（PV）,paracentral lobules（PCL）and superior frontal gyrus（SFG）in idiopathic normal pressure hydrocephalus（iNPH）patients.To evaluate the diffusional changes of white matter in different areas and their correlation with the assessment of clinical scales.Methods:A total of twenty-four iNPH patients and twenty-four healthy controls（HC）were involved in this study.All the subjects underwent detailed medical history collection before scanning,and the clinical symptoms and daily living ability of the patient group were evaluated according to iNPH Grading Scale（INPHGS）and modified Rankin scale（m RS）.Brain DSI data for all the participants were collected using the same MR scanning sequence and procedure.After data collection,the acquired diffusion MR images data were imported in the DSI studio software and reconstructed for analyses.The corticospinal tracts were tracked and the regions of interests（ROI）in different brain areas were draw.The diffusion parameters measured and analyzed based on corticospinal tracts and ROIs in different brain areas included quantitative anisotropy（QA）,the isotropic diffusion component（ISO）,general fractional anisotropy（GFA）,fractional anisotropy（FA）,mean diffusivity（MD）,axial diffusivity（AD）and radial diffusivity（RD）.Results:The mean values of QA and ISO of corticospinal tracts in iNPH patients were significantly lower than those in HC group(P_LQA=0.008,P_RQA=0.016,P_LISO=0.024,P_RISO=0.016).The mean values of MD,AD and RD of corticospinal tracts in iNPH patients were significantly higher than those in HC group(P_MD=0.032,P_AD=0.032,P_RD=0.048).There was no significant difference in GFA and FA values in corticospinal tracts between iNPH patients and HC.The GFA,MD and AD values in the areas of bilateral periventricles of iNPH patients were significantly higher than those of normal control group（P<0.01 of all）.The mean values of MD,AD and RD in the paracentral lobular regions of iNPH patients were significantly lower than those in the normal control group(P_MD=0.048,P_AD=0.032,P_RD=0.048).There was no significant correlation between the diffusion parameters of white matter of bilateral periventricles area,paracentral lobule areas,superior frontal gyrus areas and the grading levels of INPHGS and m RS.Conclusion:Decreased QA and ISO values of corticospinal tracts and increased GFA values of white matter of periventricles area were found in iNPH patients.The iNPH clinical syndrome is not only the result of compression of nerve fibers by enlarged lateral ventricles,but also reflects the presence of the damage in microstructural integrity of the fibers,as well as local ischemic white matter changes due to compression.Quantitative assessment of white matter using DSI in idiopathic normal pressure hydrocephalus may provide more information that can improve the present understanding of the mechanism of the disease.