Basic And Clinical Research On Intracranial Dural Arteriovenous Fistula

Part OneEtiological Research of Intracranial Dural Arteriovenous FistulasObjectTo investigate the pathogenesis of intracranial dural arteriovenous fistula, withspecial concern on the role of angiogenic factors and chronic brain hypoperfusion.Methods120 Sprague-Dawley rats were randomly assigned to 4 groups: 1) Group A(n=25),sham operation; 2) Group B(n=25), thrombosis of the sagittal sinus; 3) GroupC(n=35), anastomosis of the right common carotid artery(CCA) to the external jugularvein(EJV) and occlusion of the proximate-cardiac end of the transverse sinus on theleft; 4) Group D(n=35), procedures done as Group C and added thrombosis of thesagittal sinus. Mean arterial pressure, sinus pressure, blood gas from the artery andjugular vein, blood flow of the brain were monitered during the operation. Animals ofgroup C and D with its sinus pressure below 20mmHg were excluded from the study.Mean arterial pressure, sinus pressure and blood flow of the brain were again tested 1,2, 4, 12 weeks after operation in subgroups of animals. Histological examination andWestern blotting analysis were used to test the distribution and concentration ofVEGF and MMP-9 in dura mater, arachnoid membrane, cortex and basal ganglia.Perfusion MR of the brain was done to compare blood flow in different site of thebrain.ResultsIn group C and D, the mean blood pressure went down soon after operation, and thesinus pressure elevated to 28.55±4.92mmHg and kept stable at 22.34±3.24mmHg 4weeks later. The SO₂ of the vein draining the left transverse sinus changedsignificantly from 58.02±3.58% to 93±3.18% in group C and from 57.74±3.34 %to 95.58±1.72% in group D after CCA-EJV anastomosis. The blood flow of the brainwent down significantly after operation in group C and D, with the right occipital lobemore significantly than any of the other sites. Two weeks later the blood flow hadretumed to the normal level in the left side but stayed abnormal in the right occipitallobe. Perfusion MR found higher blood volume and longer mean time to enhance in the right occipital lobe, comparing with its contralateral side. Immunohistologicalstain of VEGF was positive in basal ganglia, right occipital lobe and arachnoidmembrane one week after operation, but weakened in basal ganglia two weeks later.VEGF expression was weak in dura mater one week after operation, but becamestrongly positive from the 4th to 12th week after operation. The angiogenesis wasprominent in the dura mater 12 weeks after operation in group C and D but negativeor abscure in group A and B. Western blotting analysis of the protein of dura mater 12weeks after operation realized the expression of VEGF as D＞C＞B=A, andexpression of MMP-9 as D＞C＞B＞A.ConclusionsSinus high pressure was the main reason for angiogenesis of dura mater and wascritical for DAVF formation. Sinus thrombosis is a risk factor for elevation of sinuspressure. Chronic brain hypoperfusion is an early sign of venous hypertension. It willpromote the expression of VEGF and MMP-9, so as enhance abnormal angiogenesisof the dura mater. Chronic brain hypoperfusion is an important step from theprogression of venous hypertension to DAVF formation, so maybe helpful forjudgment of the prognosis of DAVF before venous reflex.Part TwoAnatomy and Surgical Approaches of the TentoriumObjectTo investigate the anatomic features of the tentorium, compare the difference ofvarious approaches to this region and to select the proper approach for the lesions ator around the tentoriam.Methods15 cadaver heads were used to observe the number, shape, derivation and afflux ofthe tentorial sinuses. Under the direction of neuronavigation, another 15 cadaverheads were used to modify surgical approaches. The anteriolateral approachesincluded trans-sylvian approach, subtemporal approach and trans-anterior petrousapproach. The posterior approaches included suboccipital transtentorium approachand subtentorium-supercerebellar approach. The exposed realm of the tentorium andsurrounding structures were labeled with navigation system.ResultsMain tentorial sinuses located at the posteriomedial part of the tentorium, deriving from the bridge veins of the superior verrnis and medial part of the cerebellum.Tentorial sinuses at the posteriolateral part of the tentorium derived from the bridgeveins of the temporal and occipital lobe. Veins at the tentorial edge were frombranches of deep venous system or the petrous vein. The trans-anterior petrousapproach had the best view to tentorium, comparing with other anteriolateralapproaches. Ipsolateral tentorial edge and superficies inferia at the petrous apex couldbe fully visualized. The lateral part of the tentorium could be better visualized viasubtemporal approach and the posterio-medial part of the tentorium could be betterexposed via posterior approaches. The suboccipital transtentorium approach had thebest view of the medial tentorial edge and the pineal region. After incision of thebilateral tentorium and the falx, we could get a total view of the pineal region.ConclusionsRegular pattem of the tentorial sinus was summarized. Different approaches couldexpose different realm of the tentorium. Accordingly, tentorial dural arteriovenousfistula could be classfied into the marginal type, the medial type and the lateral type.Appropriate surgical approaches should be be chosen based on the fistula site at thetentorium.Part ThreeDiagnosis and Therapy of Intracranial Dural Arteriovenous FistulasObjectTo summarize the clinical characters, diagnostic and therapeutic ways of theintracranial DAVF.MethodsA review of 54 patients with intracranial DAVFs treated in our hospital from July2001 to June 2006 was conducted, including the clinical manifestation, imagingcharacters, therapeutic procedure and results. The fistula located at thetentorium(n=14, 25.9%), transverse or sigrnoid sinus(n=7, 13.0%), anterior cranialfossa(n=6, 11.1%), superior sigittal sinus(n=6, 11.1%), foramen magnum(n=2, 3.7%)and sphenobasic sinus(n=1, 1.9%). There were 18 cavernous sinus DAVF(33.3%).According to Borden classification, there were typeâ… 16 cases(29.6%), typeâ…¡16cases(29.6%) and typeâ…¢22 cases(40.7%). Clinical manifestation includedintracranial hemorrhage(n=13), progressive neurological defesits(n=15), chronicintracranial hypertension(n=7), etc. 22 cases underwent intravascular embolization, including 15 via arterial pathway and 8 via the venous way. 22 cases underwenttranscranial operation without embolization and 8 cases was treated with thecombination of vascular embolization and microsurgery.ResultsPostoperative DSA was performed in 41 cases(74.5%), demonstrating the cure in25 cases(61.0%), relief in 13(31.7%) and recurrence in 3 cases(7.3%). 47 cases werefollowed up for a mean time of 32.5 months. No one had intracranial hemorrhageduring follow up period. 29 cases(61.7%) returned to normal life without neurologicaldeficits. Symptoms relieved in 11 cases(23.4%) and resumed in 4 eases(8.5%). 3 casesrecurred and need further therapy.ConclusionsVenous hypertension was the main cause of severe symptoms. Therapeutic methodswere different according to the site of fistula. Intravascular therapy was preferred forcavernous sinus DAVF, while microsurgery was the first choice for DAVF of theanterior cranial fossa and tentorium. Tentorial DAVF could be divided into themarginal type, medial type and lateral type according to the fistula site at thetentorium. Appropriate approaches were chosen accordingly. Combination ofintravascular therapy and microsurgery was recommended for complex ones, and theresults remained unsatisfactory.