Applied To The Ultra-high Field Magnetic Resonance Study Of Patients With Primary Systemic Dystonia

Background Primary generalized dystonia(PGD)is a heterogeneous disease identity with no pathological changes observed on routine clinical imaging investigation.However,several structural characteristics and/or variations have been reported on PGD patients,including scattered spotty signals and volumetric changes on bilateral basal ganglia.Recently,the technology of ultra-high field magnetic resonance imaging has made crucial progress,with significant improvement regarding spatial resolution,tissue contrast,identification of microstructures.However,currently there is no research performed on PGD patients yet using 7-Tesla MRI.Method(1)Patients were enrolled in the study if they were diagnosed as PGD in Peking Union Medical College Hospital department of Neurology and were referred in preparation of deep brain stimulation(DBS)from December,2017 to June 2018.Healthy volunteers with matched age and sex were also recruited in the study.All subjects underwent T1-MP2RAGE(spatial resolution 0.72 mm),3D-GRE-SWI(spatial resolution 0.75 mm)and 2D-GRE-T2*(in-plane resolution 0.25 mm)scan on a SIEMENS Magnetom 7-Tesla scanner.(2)After transforming the slices in parallel with intercommissual line,visibility of spotty signals on bilateral basal ganglia were examined and recorded.On T1WI,the minimal diameter on the central section of the biggest spotty signal were measured bilaterally(defined as intraplanar diameter).(3)Voxel-based morphometry(VBM)was applied to compare regional gray matter differences among hereditary PGD,idiopathic PGD and healthy control.The T1WI was segmented according to tissue probability maps and unified segmentation algorithm,after which a template was generated using diffeomorphic registration algorithm.The images were then normalized into Montreal Neurological Institute(MNI)template and smoothed using a Gaussian kernel with full-width-at-half-maxima(FWHM)of 8 mm.A family-wise error(FWE)correction of 0.05 was applied,after which the statistical parametric map was plotted.(4)Manual segmentations of bilateral globus pallidus internus(GPi),globus pallidus externus(GPe)and putamen were performed.Shape radiomic feature of the segmentations were calculated(including volume,volume standardized by total intracranial volume,surface area,surface-volume ratio,sphericity,major/minor/least axis,elongation and flatness).Comparisons of these features were made among hereditary PGD,idiopathic PGD and healthy control.Results(1)16 PGD patients were enrolled in the study,including 8 with hereditary PGD(6 DYT1 dystonia,2 DYT6 dystonia)and 8 with idiopathic PGD.15 age-and sex-matched healthy volunteers were also enrolled.(2)T1-hypointensive T2*-hyperintensive spotty signals were observed on bilateral basal ganglia on all subjects.The left intraplanar diameter of spotty signals were larger in PGD patients compared with healthy controls.(3)No regional gray matter differences were observed among patients and healthy controls by VBM.(4)Both hereditary and idiopathic PGD patients had lower sphericity of bilateral GPi compared with healthy control.Idiopathic PGD patients had higher elongation of bilateral GPe compared with healthy control.Both groups of PGD patients had lower volume,standardized volume and shorter major axis of bilateral putamen compared with healthy control.Conclusion(1)Spotty signals can be observed on all subjects,which is deduced to be Virchow-Robin spaces(VRS)taking previous literature into consideration.PGD patients may had bigger VRS than healthy control,while the mechanism still remains to be elucidated.(2)PGD patients had smaller putamen compared with healthy control.(3)PGD patients also had variations on shape of bilateral pallidum.