MR Features Of Myodural Bridge Complex And Its Correlation With Cerebral Spinal Fluid Flow

Part I Magnetic resonance imaging of Sui-Yu’s ligament and rectus capitis posterior minor with anatomical validationObjective:This study aims to evaluate the magnetic resonance imaging of Sui-Yu’s ligament and rectus capitis posterior minor（RCPmi）with anatomical validation.Materials and methods:This study was approved by the institutional review board of Dalian Medical University.Five fresh unfrozen head specimen（4 males and 1 female）were imaged by a 3T MRI scanner utilizing a spinal phased-array coil in the supine position.The sequences included sagittal T₂ weighted imaging（T₂WI）,sagittal T₁weighted imaging（T₁WI）and three-dimentional（3D）T₂WI.The data of 3D T₂WI was transmitted to the Advantage Workstation 4.4 and parasagittal or oblique sagittal images were reformatted using the Functool post-processing software equipped in.The images of Sui-Yu’s ligaments on 2D T₁WI、T₂WI and 3D T₂WI were scored by two radiologists and score≥3 was good enough for observation of Sui-Yu’s ligaments.Based on anatomical-MRI classification standard,two radiologists evaluate the types and subtypes of 5 Sui-Yu’s ligaments and 10 RCPmis.Consensus was gotten after discussion if there was different opinion.The head specimens were sent for anatomical dissection following imaging acquisition.Two experienced dissectors evaluated the types of Sui-Yu’s ligaments and RCPmis.Inter-observer agreement for MRI scores of Sui-Yu’s ligaments was tested using Cohen’s kappa and kappas over 0.75 was considered as excellent agreement.A probability value（p）less than 0.05 was considered statistically significant.Results:The scores for Sui-Yu’s ligaments on T1WI、T2WI、3DT2WI and reformated images were more than 3 with good inter-observer agreement.The score from 3D T2WI and reformated images was the highest.The anatomical type and subtype of 5Sui-Yu’s ligaments was 1 of IA,IB,IC,ID and IID,respectively.And the MRI type and subtype was 2 of IA,1 of IB,IC and IID.The classification of 10 RCPmis was 1 of type I,7 of type II and 2 of type IV.Two of RCPmis were observed second termination to Sui-Yu’s ligaments in dissected specimens while as only one observed on MRI.Conclusions:The Sui-Yu’s ligaments and RCPmis can be demonstrated well on 3D T₂WI with good anatomical validation.Part II Sui-Yu’s Ligament,an important myodural bridge’s component deriving from nuchal ligament-a MRI pilot study in vivoObjectives: To assess the involvement pattern of nuchal ligament（NL）in myodural bridge（MDB）via Sui-Yu’s ligament in the suboccipital region using MR 3D T2-weighted imaging in vivo.Materials and Methods: This retrospective study was approved by the institutional review board and the informed consent was waived.This study included 320 subjects（mean age= 43.4 years;range,17-87 years;138M: 182F）who have underwent suboccipital sagittal 3D T2 W MR imaging from September 2015 to December 2017.The MR imaging was performed on all subjects with a 1.5/3.0T unit utilizing a spinal phased-array coil in the supine position.The sequences included sagittal T2 weighted imaging（T2WI）,sagittal T1 weighted imaging（T1WI）and three dimension（3D）T2WI.The data of 3D T2 WI was transmitted to the Advantage Workstation 4.4 and parasagittal or oblique sagittal images were reformatted using the Functool post-processing software equipped in.The 3D T2 WI images were interpreted double-blinded twice by two radiologists with 12 and 10 years of experience in reading musculoskeletal MR images to evaluate the inter-observer concordance.Sui-Yu’s ligament was classified conferring to its dominant orientation and connection pattern with cervical dura mater in the suboccipital region.The involvement pattern of Sui-Yu’s ligament was then classified into radiate（type I）and arcuate（type II）types according to its dominant orientation.It was further divided into four subtypes according to its correlation to the posterior atlanto-axial（PAA）,posterior atlanto-occipital（PAO）interval and RCPmi muscle.SPSS 22.0 software for Windows（SPSS Inc.,Chicago,Illinois,USA）was used for statistical analysis.Inter-observer agreement was tested using Cohen’s kappa and kappas over 0.75 was considered as excellent agreement,0.40 to 0.75 as fair to good agreement whereas below 0.40 as poor inter-observer agreement.The subtype distribution between female and male groups was estimated using Kruskal-Wallis test.A probability value（p）less than 0.05 was considered statistically significant.Results: The Sui-Yu’s ligaments were observed in all subjects.The Kappas of the inter-observer interpretation was 0.936.Radiate type I included 183 subjects,consisting of 55 subjects with subtype IA,10 with subtype IB,75 with subtype IC and 43 with subtype ID.Arcuate type II included 137 subjects,consisting of 29 subjects with subtype IIA,1 with subtype IIB,54 with subtype IIC and 53 with subtype IID.30.00%of Sui-Yu’s ligaments had hypo-intense connection with RCPmi muscles,while 55.21%were recognized in the arcuate type.The gender respective distribution of radiate and arcuate type was conspicuously different in men versus women.Conclusions: Sui-Yu’s ligament was proven to be an local enhancement deriving from nuchal ligament by 3D T2 WI in vivo.It is normal anatomical structure and connects with cervical dura mater directly via atlanto-axial,atlanto-occipital interval,and indirectly as second termination attachment for RCPmi muscle as well.Part III 3D MR morphological study of rectus capitis posterior minor in vivoPurpose: To evaluate the morphological features of rectus capitis posterior minor（RCPmi）in vivo and assess the potential correlation of the RCPmi muscle and Sui-Yu’s ligament,two components of myodural bridge via suboccipital zone using 3D MR T2-weighted imaging.Materials and Methods: This retrospective study was approved by the institutional review board and the informed consent was waived.This study included 320 subjects（mean age= 43.4 years;range,17-87 years;138M: 182F;23 left-handed;297right-handed;BMI:16.26⁴0.76Kg/m2）who have underwent suboccipital sagittal 3D T2-weighted MR imaging.The MR imaging was performed on all subjects with a3.0/1.5T unit utilizing a spinal phased-array coil in the supine position.The sequences included sagittal T2 weighted imaging（T2WI）,sagittal T1 weighted imaging（T1WI）and three-dimentional（3D）T2WI.The data of 3D T2 WI was transmitted to the Advantage Workstation 4.4 and parasagittal or oblique sagittal images of Sui-Yu’s ligament and RCPmis were reformatted using the Functool post-processing software equipped in.The3 D T2WI images were interpreted double-blinded by two radiologists with 12 and 10 years of experience in reading musculoskeletal MR images.RCPmi was classified conferring to its terminations including arch of atlas,atlantooccipital membrane and atlanto-axial interspace.The subjects were classified into positive and negative groups according to connection observed between RCPmi and NL.The positive group indicated hypo-intense band or strip from RCPmi to NL while the negative group demonstrated no connection between them.Consensus was reached after discussion while opinions were different.The major axis of cross-sectional area（CSAma）of left and right RCPmi was measured with a 30°deviation from the oblique plane that passed through the mid-posterior arch of atlas and the larger one was considered as the final results with good inter-examiner agreement.Spearman was used to analyze the correlation between types of RCPmis and gender,age,BMI and left&right handed.The BMI and gender distributions in these two groups were compared with Spearman analysis.r less than 0.2 was considered no correlation.The inter-examiner agreement of CSAmas measurement was tested by means of the repeated measures ANOVA intraclass correlation coefficient（ICC）.The differences of ma CSAs between positive and negative groups,male and female group and left and right side were compared using the independent Student’s t-test.A probability value（p）less than 0.05 was considered statistically significant.Results: Six hundred and twenty-four RCPmis were observed in 320 subjects, including 9 of type I,578 of type II,1 of type III and 36 of type IV.There was no correlation between the anatomical types and gender,age,BMI and left & right handed（r was 0.045、0.135、0.053 and 0.045）.Hypo-intense bands or strips from RCPmis to NLs were identified in positive group including 123 RCPmis with 61 on the left side and 62 on the right side.There were 501 RCPmis in negative group.The BMI and gender showed no correlation between these two groups（r=0.053,0.045）.The inter-examiner repeatability of MRI measurements（ICC）for RCPmis’ ma CSA were0.891,suggesting a good agreement.The mean CSAma of 624 RCPmis was63.04±29.64 mm2,it was no correlation with age,left & right handed and BMI.The mean CSAma of left RCPmi was 62.18±29.88 mm2,and that of right one was63.89±29.42 mm2,and there was no statistical difference between left and right RCPmis.The mean CSAmas of RCPmis from men（n=237）was 76.28±30.87mm2,significantly bigger than 52.74±24.07 mm2 of women（n=351）.The mean ma CSAs of positive group was significantly smaller than that of negative group（55.95±26.76 mm2 vs.64.78±30.07 mm2,P=0.003）.Conclusions:The current study indicated that 3D T2 WI was a reliable modality to demonstrate RCPmis in vivo.The CSAmas of RCPmis were correlated with gender and men with bigger RCPmis.RCPmis connected with Sui-Yu’s ligament by hypo-intense fibrous or muscular tissue correlating with smaller RCPmis.This may indicate that RCPmi and Sui-Yu’s ligament work together as a myodural bridge complex.Part IV Quantitative assessment of cerebral spinal fluid flow by phase contrast cine imaging in atlantooccipital interval with suboccipital manual therapy-a pilot studyPurpose: To compare the difference of cerebral spinal fluid（CSF）flow by phase contrast（PC）cine imaging in atlantooccipital interval before and after manual therapy in suboccipital region.Materials and Methods: This retrospective study was approved by the institutional review board and the informed consent was obtained.This study included 31 subjects who worked at desks（mean age= 24.77 years;range,21-30 years;9M: 22F）who have underwent suboccipital manual therapy for ten continuous days.MR PC cine imaging in atlantooccipital interval was performed before and after manual therapy.The MR imaging was performed on all subjects with a 1.5T unit utilizing a spinal phased-array coil in the supine position.The data of PC cine was transmitted to the Advantage Workstation 4.6 and analyzed using the Report-Card post-processing software equipped in.One experienced radiologist measured the PC cine parameters including peak positive velocity（PPV）,peak negative velocity（PNV）,flow（F）,positive pixel flow（PPF）and negative pixel flow（NPF）.Nonparametric paired Wilcoxon test was used to analyze CSF flow difference before and after suboccipital manual therapy.A probability value（p）less than 0.05 was considered statistically significant.Results: The mean CSF flow after manual therapy was statistically higher than that before manual therapy [（0.12±0.12）vs.（0.07±0.08）ml/beat ] and the PPF after manual therapy was statistically higher than that before therapy [（0.44±0.24）vs.（0.38±0.20）ml/beat ].the average PPV [（5.36±1.44）vs.（5.28±0.63）cm/s ],NPV [（-4.40±2.12）vs.（-4.07±1.93）cm/s ] and NPF [（-0.32±0.15）vs.（-0.31±0.15）ml/beat ] was no statistical difference after and before manual therapy.Conclusions: The cerebral spinal fluid flow and positive pixel flow from atlantooccipital phase contrast cine imaging increased after manual therapy in suboccipital region in subjects working at desks.The myodural bridge may transmit power from suboccipital muscles to dura mater to influence the CSF circulation.