A Clinical Study Of Venous Morphology And Hemodynamics In Cerebral And Jugular Venous Outflow Impairment

Background and purpose:Internal jugular vein is the main cerebral venous outflow tract, which abnormalities instructure and hemodynamics are presumed to impair cerebral venous drainage and further toinfluence cerebral circulation, particularly during valsalva maneuver(VM), resulting inmarked increase in cerebral venous congestion and decrease in cerebral blood flow duringVM to venous ischemia, even related to impairment of cerebral autoregulation. The aim of mystudy was to open up new insights into venous outflow obstruction by using MR imaging andultrasound to investigate the venous morphology and hemodynamics, and their clinicalimplications.Materials and Methods:MR imaging study:A magnetic resonance (MR) imaging protocol was used in patients of transient globalamnesia (TGA), transient monocular blindness (TMB) and panic disorders and age-andsex-matched controls to assess the morphologies of IJV, brachiocephalic vein (BCV) andasymmetry of transverse sinus (TS), which included to measure diameter of the TS and tolocate the site and degree of venous flow stenosis/obstruction. The IJV were divided into theupper-IJV and middle-IJV segments. MR imaging protocol included time-resolved imaging ofcontrast kinetics (TRICKS), contrast-enhanced axial T1-weighted MR imaging (contrast T1),and MRV.Ultrasound study:Secondary analysis of a previously collected data set from three prospective studies ofTGA, TMB and panic disorders. MR imaging and ultrasound of neck was reviewed in all subjects. Ultrasound of neck parameters, such as the cross-sectional lumen area (CSA), time-verage-mean velocity (TAMV), and flow volume (FV) at the middle segment (J2) and distalsegment (J3) were recorded at brief apnea after three respiratory statuses:(1) normalrespiratory status (resting or baseline),(2) deep inspiration, and (3) expiration both in supineand sitting in all TGA patients and controls. The jugular venous reflow/reflux/no reflow wasrecorded during VM for duration15seconds in all subjects.Results:In the first part of this paper, we found TGA patients have a higher prevalence ofmoderate/severe compression in the upper segment of Internal Jugular Vein (IJV), and in leftbrachiocephalic vein (BCV) and of transverse sinus (TS) asymmetry by MR imaging. Thesefindings are new evidences supporting the role of extracranial veins in the TGA pathogenesisand substantiate the venous pathogenesis theory.In the second part of this paper, in the MR imaging study,69subjects had TS hypoplasiabased on MRV criteria, of which30were anatomically small and39were not small based oncontrast T1-weighted MR (contrast T1) findings. The latter is correlated with at least one siteof venous compression/stenosis in IJV or left brachiocephalic vein (BCV)(P=0.0002). Incontrast T1imaging, the diameters of contralateral TS were not enlarged in groups of TShypoplasia. In ultrasound study, the CSA of IJVs was significantly smaller (P<0.0001) on theside of TS hypoplasia. Using IJV CSA ratio (contralateral/ipsilateral)>1.55as cut-off pointto discriminate TS hypoplasia can provide sensitivity0.80, specificity0.81and positivepredictive value0.82. Many TS hypoplasia in MRV are not real hypoplasia with small TSdiameter. Using ultrasound finding of IJV CSA ratio predicts TS hypoplasia accurately.In the third part of this paper, we correlated the findings of MR imaging and ultrasound.The flow volume (FV) of jugular vein was decreased in case of jugular veinstenosis/compression revealed in MR imaging. Moreover, FV of bilateral jugular veins weresignificantly lower in TGA patients than those in controls, and the frequency of orthogradeflow reappeared in the IJV during VM was also lower in TGA patients.The study support theconclusions of the first part of this study, and suggested that IJV reopens during VM could alleviate the intracranial venous congestion and that IJV obstruction does not allow anefficient blood outflow.In the fourth part of this paper, the FV of IJV was low in case of IJV stenosis/compression at various segments. Using resting TAMV <8.0(cm/s) as cut-off point todiscriminate BCV obstruction/compression can provide sensitivity0.78, specificity0.61andpositive predictive value0.63. The IJV from Ultrasound examination could be a surrogate fordetecting severe compression/obstruction in left brachiocephalic vein (BCV) and transversesinus (TS) asymmetry compared with MR imaging finding. To establish a hemodynamics ofIJV with jugular vein stenosis/obstruction in ultrasound can be used in further clinicalresearch.Conclusion:New evidences confirmed the important role of TS hypoplasia and non-patency ofextracranial veins in TGA patients, which further substantiated the venous roles in the TGApathogenesis. Further studies are needed to elucidate the causal relationship and to find abetter and appropriate treatment for patients. We found that two types of hypoplasia exist:anatomical and flow-related, the latter was not real structure hypoplasia and it was related tovenous stenosis/compression. The facts that venous flow volume decrease in resting and noreflow appeared in IJV during VM in condition of stenosis/compression at various venoussegments further support the venous pathogenesis. Ultrasound examination can be a surrogatefor prediction of TS hypoplasia and BCVstenosis/compression.