Morphological Study Of The Orifice Of Bridging Vein Into The Superior Sagittal Sinus And The Chordae Willisii Adjacent To The Orifice

Objectives To clarify the form and distribution of endothelial cell (EC) and smooth muscle cell (SMC) in vessel wall of the orifice of bridging vein(BV) into the superior sagittal sinus (SSS) by observing the histology and ultrastructure of the orifice of BV, for the occurrence of cerebral venous thrombosis (CVT) in vivo mechanism to provide a new interpretation. To investigate the feature of appearance and distribution of chordae willisii, we observed the willisii nearby the orifice of BV into different segments of the SSS by microanatomy, sectional anatomy and neuroimaging. It provides clarification about its function and influence for mechanism of CVT.Methods①24 orifices of BV into SSS obtained from 5 cadavers were stained with Hematoxylin Eosin (HE) or Van Gieson (VG) to observe its histology.②32 orifices of BV into SSS obtained from 7 cadavers were stained with double-immunofluorescence using anti-vWF and anti-α-SMA to observe the positive expression.③9 orifices of BV into SSS obtained from 7 patients without cerebral venous diseases were examined by Transmission Electron Microscope (TEM) to observe its ultra-microstructure.④30 adult human cadaveric heads, 23 ones were observed by splitting superior walls of the superior sagittal sinus along the long axis , 7 ones were studied by cutting continual coronal section. Record the number, location and distribution of all kinds of chordae willisii in different segments of the SSS which was divided into four segments from anterior to posterior.⑤20 patients without cerebral venous diseases or injury were examined by contrast enhancement magnetic resonance (CE-MR) to observe the feature of chordae willisii in the SSS. Results 1. The microstructure of the orifice of BV into SSS:①The orifice became narrower and its tunica was thick; Clingy ECs of the orifice, the SMCs were more and dense; The SMC with single elliptical or rod-shape nuclear, fusiform in shape and different in length, ran longitudinally and intercrossed with each other in the wall of orifice; No complete layer of smooth muscle wan found in the wall of orifice; Collagen fiber was plenty and dense; The structure of orifice was no significant difference between anterior segment and posterior segment of the SSS.②The arachnoid mater side wall of the orifice was thin and less SMC and collagen fiber content; The dural mater side wall of the orifice was thick and SMC and collagen fiber content.③The wall of the orifice of vWF andα-SMA were positive immune response; vWF-positive endothelial cells were mainly distributed within the lumen surface of the orifice, a linear expression, there were intermittent defects;α-SMA-positive smooth muscle cells were closed to the endothelial cells in orifice, the elongated spindle or cords, the number were more dense, almost coveraged of endothelial cells.④TEM showed the wall of the orifice of a large number of smooth muscle cells, most cells were arranged in longitudinal rows, fusiform nucleus; Cell sarcolemma sagged down to constitute many small caveola, there were many the dense patches, the cytoplasm was rich in muscle filaments, dense bodies and chondriosome; Collagen fibers existed within the extracellular matrix. 2. The anatomy and imaging observation of the chordae willisii adjacent to the orifice of BV into SSS:①The total number of chordae willisii was 425 in 23 specimens with microanatomy, an average of 18.5, divided into three basic types of valvelike, trabecular and lamellar.②We observed 201 valvelike by microanatomy in total, the type of chordae covered 53% of the orifice of BV into SSS; 74% of the valvelike located in the segment 3 of the SSS and 22% in the segment 1; The sectional anatomy showed that the valvelike chordae made the orifice become narrower.③We observed 130 trabecular by microanatomy in total, the trabecular composed complex networks in the SSS, most located in the posterior of valvelike and made the lateral wall of SSS become thicker; 58% of them located in the segment 3 of the SSS and 20% in the segment 1; The sectional anatomy showed some trabecular chordates were shorter and free.④We observed 94 lamellar by microanatomy in total, 64% of them were located in the segment 3 of the SSS; Sectional anatomy showed that lamellar chordate connected the top wall or side wall of sinus in the different forms, divided the lumens of SSS into two separate diameter pipe.⑤20 CE-MR imaging showed 206 chordae willisiis in total, could't distinguish three basic types; The chordae in the CE-MR images showed cord-like filling defect within the sinus, equal density or low density lesions; The image showed that the chordae willisii was close to the orifice of BV.Conclusions①The structure of the wall of the orifice of BV is asymmetrical, the orifice is no significant distinction in different segment of the SSS.②The structure of the orifice exists abnormal histological changes, this may be related to pathogenesis of CVT and could provide a basic morphology evidence for the occurrence of CVT.③The chordae willisii closed to the orifice of BV in the SSS is complex and various, it has the specific feature of segmental distribution, possibly affects the pathogenesis of CVT.④CE-MR image can show morphology and distribution of the chordae willisii, this could provide differential diagnosis for cerebral venous disorders.