The Mechanism And Significance Of Human Brain Bridging Veins System To Regulate Increased ICP

Increasing intracranial hypertension (ICP) is the most common symptom of nervous system diseases. It is one of the most important topics at neuroscience field to make sure the mechanism of ICP regulation and search for effective methods to decrease ICP. Especially, many researchers have put more and more attention and interest to the method aiming at cerebral circulation system (volume-targeted). Arterial hemodynamic features including reflecting the brain perfusion and automatically regulating ICP balance to some extent have been investigated and described in detail. "Lund" concept-to decrease the intracranial volume by the way of promoting the re-absorption of interstitial fluid in blood capillary bed-has been systematically studied too. But the investigation about cerebral vein system-the biggest blood storeroom-was less reported to review relative literatures. We carried out the pilot experiments to describe brain bridging veins in porcine and underlaid deeper research about human brain bridging veins by initially approaching possible ICP regulation mechanism. In this investigation we observed the morphology features of human brain bridging veins by optical and electronic microscope and described the image morphology and haemodynamics variation in vivo using advanced intracranial MR venography. Based on these foundations we approached its possible mechanism of brain vein system's participation into increasing ICP regulation.The brain bridging veins are the final pathway through which intracranial blood afflux into sinus venosus via brain circulation system. Those veins located at anatomical position with very unusual significance. The first part was morphology research on human brain bridging veins. The specimen of human brain bridging veins acquired during operation was stored and processed with routine methods and then observed them under optical and electronic microscope. We found special morphology features at bridging vein outflow segment which showed obvious differences from other parts of brain vein system just before affluxing into sinus venosus: the human brain bridging veins are short of smooth muscle cells and lots of collagenous and elastic fibers show to be pycnomorphous. But the collagenous and elastic fibers arranged irregularly and more sparsely in other parts of human brain bridging veins without nerve tissue. The ultrastructural organization of fibers can be demonstrated clearly under electronic microscope. For lacking of smooth muscle cell and nerve tissue and inactive contraction of collagenous and elastic fibers we draw a conclusion by saying that: the regulation of blood outflow through brain bridging veins was not positive instead of inactive mechanism with collagenous and elastic fibers.In second part in order to observe the morphology of human brain bridging veins the 2D-TOF MR venography was used to scan and acquire original bridging veins images of adults without intracranial diseases, then postprocessing these original images with maximum intensity projection (MIP). This part of vein possesses obviously different morphology features such as arrangement mode, vessel orientation, bulb of brain bridging veins and weaken even disappearance of MRI signal et al. At the same time we founded the normal value limitation (95%confidence interval) of human brain bridging veins under physiological functions by measuring and analyzing the veins images using Syngo fastview image manipulation system. The normal value limitation foundation of the final pathway- brain bridging veins -will provide valuable morphology theoretical basement. And the findings will start a brand-new field for next investigation in ICP regulation of brain vein system. Because of fluid saturation effect winding vein vessels maybe cause signal weaken or disappearance. But MR venogaphy can play an important and effective role to demonstrate the small or middle level vessels such as human brain bridging veins. 2D-TOF MR venography can provide imageology support for clinical diagonosis of vein diseases.In third part adult patients with the increasing ICP according to chief complaint and case history were chosen as research objects with intracranial lesion through MRI scanning except for vessel diseases. After collecting clinical and imageology materials all the increasing ICP patients' and control were scanned using Phase Contrast cine (PC ) and CE-MRV to acquire original images of human brain bridging veins. Then with help of graphic processing software we described the morphology and haemodynamics and analyzed the dependablity between increasing ICP and haemodynamics features. Based on these findings we investigated the law how the brain vein system regulate vein blood outflow and influent ICP, We found a special structure similar to "outflow cuff segment" in animal model. Human brain bridging veins may be the key point of brain vein blood outflow volume because of existing of "outflow cuff segment": ICP increased, outflow resistance increased, outflow volume reduced, then caused the aggravatation of vein blood deposition in vein bed. Such a sequent procedure formed an infernal circle: ICP increase-vein outflow reduce-vein blood deposition-ICP increase all the better. The MRI scanning results confirmed that the human brain bridging veins would appear increased diameter,slow blood velocity and increased outflow resistance et al.This research confirmed the existence of outflow segment cuff, established the value range of this part of vessel' diameter and described its special morphologic features, through optical microscope, electron microscope in vitro and MRI in vivo. We paid most attention to the effect of human brain bridging veins on ICP regulation and vein blood outflow and investigating the mechanism of reducing ICP when brain veins volume decreased. These findings can provide new ideas and clues to start a brand-new field about ICP regulation, underlay the theory to reduce ICP by interfere with outflow of brain veins and establish a new method to treat increasing ICP from brain injure or intracranial space occupying lesion. At the same time we described the MRI imaging characteristics of human brain veins in order to evaluate the ability of these kinds of MR venography techniques and our investigation can provide significant evident for next clinical practice.