Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3801_Библиотеки_им_академика_М_И_Перельмана

On the other hand, several studies have reported nonthrombotic occlusion of the dural sinuses as the primary cause in the pathogenetic process. Occlu­sion of the sinuses due to the direct compression of tumors (Arnautovic et al. 1998) or due to the surgi- cal sacrifi ce of the sinus during tumor removal may equally result in development of DAVM as late as up to 7 years following surgery (Sakaki et al. 1996). These latter fi ndings suggest that venous congestion and hypertension, rather than sinus thrombosis, lead to dural AV shunts. To check this assumption a num­ber of animal experiments were recently carried out. In rats, surgically induced venous hypertension by artifi cial carotid-jugular fi stula and proximal jugu­lar vein ligation resulted in development of arteriove­nous malformations, one of them located on a dural sinus (Terada et al. 1994). A combination of signifi ­cant (three- to sixfold) increase of the venous pres­su re (by lig ation of the drai ning vein of t he t rans verse sinus) and artifi cially induced superior sagittal sinus thrombosis resulted in arteriovenous fi stulae that de­veloped within the dura near the thrombosed section of the sinus. However, a direct connection between the fi stula and the thrombus was found in only half of the cases (Herman et al. 1995). In another series of experiments, superior sagittal sinus thrombosis was induced in all animals, with or without venous hypertension. Angiogenic activity of the dura mater adjacent to the thrombosed section of the sinus was tested and found to be positively correlated with ve­nous hypertension but was not correlated with sinus thrombosis. Development of dural AV fi stulae corre­lated positively with both venous hypertension and increased angiogenic activity, suggesting that venous hypertension is the primary etiologic factor in the de­velopment of DAVM (Lawton et al. 1997). Evidence of increased angiogenic activity was also found in as­sociation with DAVM in human beings. Surgically ex­cised specimens were studied that had been removed from patients harboring DAVMs associated with si­nus thrombosis. The subendothelial and medial layer of the sinus wall, as well as the wall of proliferating vessels and connective tissue around the involved si­nuses expressed basic fi broblast grow th factor (bFGF) on immunohistochemical staining. The endothelium of the sinus expressed vascular endothelial growth factor (VEGF) (Uranishi et al. 1999).