Modification of a previously described arteriovenous malformation model in the swine: endovascular and combined surgical/endovascular construction and hemodynamics

BACKGROUND AND PURPOSE: The rete mirabile in swine has been proposed as an arteriovenous malformation (AVM) model for acute experimental studies through surgical creation of a large carotid-jugular fistula. This report describes two endovascular modifications to simplify the surgical creation and provides hemodynamic parameters for the AVM model. METHODS: An AVM model was created in 29 animals to study n-butyl 2-cyanoacrylate polymerization kinetics. The common carotid artery (CCA) was punctured and a guiding catheter was inserted tightly into the origin of the ascending pharyngeal artery (APA). The CCA was ligated proximal to the catheter to create a pressure drop across the rete, which represented the AVM nidus. The catheter hub was opened whenever needed and served as the venous drainage of the AVM nidus. The contralateral APA served as the arterial feeder. Instead of the surgical ligation of the CCA, a temporary balloon occlusion was performed in three animals. RESULTS: A mean pressure gradient of 14.9 +/- 10.5 mm Hg (range, 4-42 mm Hg) was measured across the rete. The mean flow rate was 30.4 +/- 14.2 mL/min (range, 3.5-46 mL/min), as measured at the venous drainage. CONCLUSION: The endovascular and combined surgical-endovascular rete AVM model in swine is easy to construct and is less time-consuming than are the currently used models for acute experimental studies. Hemodynamic parameters can be monitored during the entire experiment and correspond to values found in human cerebral AVMs.     

Spontaneous thrombosis of congenital cerebral arteriovenous malformation complicated by subdural collection: in utero detection with disappearance in infancy

We report a case of congenital left temporal lobe arteriovenous malformation (AVM) detected by cranial ultrasound in utero and confirmed immediately after birth by cranial Doppler ultrasound and cranial MRI. The AVM disappeared on follow-up cranial MRI 4 months later. A small left frontal subdural collection was present on these follow-up MR images, which subsequently resolved by the 7 month MRI study. The cause of the spontaneous thrombosis of the AVM is uncertain. The frontal subdural collection may be secondary to volume loss. This case documents the perinatal presence of AVM. The baby was neurologically intact before, during and after the thrombosis of the AVM.     

Association of cerebral arteriovenous malformation with cerebral arterial fenestration

Cerebral arteriovenous malformations (AVMs) are rarely associated with other vascular lesions. Our goal was to examine the incidence of the coexistence of cerebral AVMs and cerebral arterial fenestrations. During the past 18 years, 51 patients with a cerebral AVM were examined with selective cerebral angiography in our institution. We retrospectively reviewed these cerebral angiographies and noted associated cerebral arterial fenestrations. We found five fenestrations distributed among 3 patients. In each patient one fenestration was located in the vertebral artery (VA). In 1 patient there were additional basilar and left middle cerebral artery fenestrations. Vertebral artery angiography was performed in 43 of the 51 patients; thus, the frequency of coexistence of AVM and VA fenestration was 7 % (3 of 43). Although the clinical significance may not be great, we found a noteworthy incidence of associated VA fenestrations in AVM cases. Received: 3 February 2000 Revised: 24 July 2000 Accepted: 25 July 2000     

Spontaneous regression of cerebral arteriovenous malformations: clinical and angiographic analysis with review of the literature

Spontaneous regression of cerebral arteriovenous malformation (AVM) is rare and poorly understood. We reviewed the clinical and angiographic findings in patients who had spontaneous regression of cerebral AVMs to determine whether common features were present. The clinical and angiographic findings of four cases from our series and 29 cases from the literature were retrospectively reviewed. The clinical and angiographic features analyzed were: age at diagnosis, initial presentation, venous drainage pattern, number of draining veins, location of the AVM, number of arterial feeders, clinical events during the interval period to thrombosis, and interval period to spontaneous thrombosis. Common clinical and angiographic features of spontaneous regression of cerebral AVMs are: intracranial hemorrhage as an initial presentation, small AVMs, and a single draining vein. Spontaneous regression of cerebral AVMs can not be predicted by clinical or angiographic features, therefore it should not be considered as an option in cerebral AVM management, despite its proven occurrence.     

Follow-up MRI in dural arteriovenous malformations involving the cavernous sinus: emphasis on detection of venous thrombosis

Summary Six patients with a dural arteriovenous malformation (dural AVM) involving the cavernous sinus were followed up with magnetic resonance imaging in order to assess change in the lesions. Spin-echo (SE) imaging of three patients in whom the AVM appeared to have closed at least 1 month earlier (two of them spontaneously, and one after external carotid artery embolization) showed neither apparent flow void in the involved cavernous sinus nor evidence of venous thrombosis. SE images of the other three patients who had not been cured by external carotid artery embolization (two of whom were examined within a week of treatment), detected persisting arteriovenous shunts, including high-flow cortical venous drainage, seen as flow void. Two-dimensional time-of-flight MR angiography (2D TOF MRA) was performed simultaneously in three patients. Whereas shunting blood and the normal cavernous sinus were of high intensity, presumed thrombosed cavernous sinuses were isointense with stationary brain tissue. SE imaging can confirm the resolution of arteriovenous shunts, but poorly delineates ver acute and chronic thrombosis of the draining veins. In contrast, 2D TOF MRA directly demonstrates flowing blood, permitting the diagnosis of venous thrombosis; it should be included in follow-up of a dural AVM involving the cavernous sinus when venous thrombosis is suspected.     

3D-TOF MRA及SWI对脑血管畸形的对照研究

目的:通过分析脑动静脉畸形和海绵状血管瘤的的3D-TOF MRA及SWI磁共振表现,探讨3D-TOF MRA及SWI对脑血管畸形的诊断价值。方法:对我院收治的44例血管畸形进行高场磁共振成像,并加扫3D-TOF MRA及SWI序列,其中26例海绵状血管瘤、18例动静脉畸形。通过分析SW I和3D-TOF-MRA技术对脑血管畸形的显示情况,比较二者对脑血管畸形的检出率以及细微特征的鉴别能力等。结果:3D-TOF MRA可以清晰显示动静脉畸形的部位、大小、输入动脉的来源、输出静脉的去向等;海绵状血管瘤MRA检查均未见异常供血动脉,病灶内无异常流空信号。SWI可清晰显示海绵状血管瘤,病灶的数目及范围较常规序列增大;SWI只能显示动静脉畸形迂曲的小静脉,但不能直观显示畸形血管团的全貌及输入动脉等粗大血管的情况。结论:3D-TOF MRA技术对于AVM之类高流速低阻力的血管畸形的显示具有独特的价值,而SWI技术则对于海绵状血管瘤等小血管或低流速的血管畸形的显示具有明显的优势。     

A simplified arteriovenous malformation model in sheep: feasibility study.

BACKGROUND AND PURPOSE: Recently, a swine model of a cerebral arteriovenous malformation (AVM) has been developed that closely resembles a human AVM of the brain. The creation of such a model requires sophisticated neurointerventional techniques. The purpose of this study was to develop a simple and cost-effective AVM animal model that does not require additional endovascular techniques. METHODS: A surgical anastomosis was created in seven sheep between the common carotid artery and the ipsilateral jugular vein, followed by ligation of the jugular vein above the anastomosis and of the proximal common carotid artery below the anastomosis. The anastomosis was created on the left side in four animals and on the right side in three. Cerebral angiography from the contralateral carotid artery was performed before and immediately after surgery to delineate the relevant cerebral vascular anatomy and to determine the direction of blood flow. RESULTS: An angiographic appearance simulating an AVM was found in all the animals. The ramus anastomoticus and arteria anastomotica functioned as the feeding vessels to the rete mirabile, which represented the nidus in our model, and to the jugular vein, which represented the draining vein from the malformation. Extensive collateral flow through the rete mirabile into the distal segment of the external carotid artery above the ligature was observed angiographically, with retrograde flow through the surgical anastomosis into the jugular vein. CONCLUSION: A simple surgically created experimental model for cerebral AVMs was developed in sheep without the need for additional complex endovascular catheter manipulations of intracranial branches. Such an animal model can substantially reduce the cost of research and training in the neurointerventional or radiosurgical management of AVMs.     

Prospective comparison of late 3T MRI with conventional angiography in evaluating the patency of cerebral arteriovenous malformations treated with stereotactic radiosurgery

Introduction

Risk of further haemorrhage in patients suffering from arteriovenous malformation (AVM) would be eliminated only if complete obliteration of the AVM is obtained. Therefore, these patients frequently need long-term follow-up. Conventional catheter angiography (CCA) with a risk of 0.5 %.to 1.6 % of significant neurological complications has traditionally been used for this purpose. However, magnetic resonance imaging (MRI) at 3T may be a safer alternative. The aim of this study was to evaluate if MRI at 3T can accurately evaluate closure of AVM in 2 years after stereotactic radiosurgery.

Methods

Twenty-three patients with both MRI at 3T and a CCA study were examined. The residual AVMs were evaluated by MRI at 3T against CCA in a prospective study.

Results

The time interval between radiosurgery and neuroimaging was on average of 25 months (range, 15–30 months) for MRI study and 33 months (range, 25–46 months) for CCA study. Ten patients showed closure of the AVM on MRI, all of which were confirmed on CCA.

Conclusion

There was a complete agreement between late MRI at 3T scan and CCA in evaluation of AVM patency.     

多层螺旋CT血管造影在急性自发性颅内出血中的应用价值

目的探讨多层螺旋CT血管造影(MSCTA)在急性自发性颅内出血中的应用价值。方法CT诊断急性自发性颅内出血41例,其中蛛网膜下腔出血29例、脑内血肿12例,采用容积重建(VR)和最大密度投影(MIP)方法进行MSCTA检查,并对7例颅内动脉瘤钛夹夹闭术病例和2例脑动静脉畸形、1例脑动静脉畸形伴巢内动脉瘤手术切除病例进行术后MSCTA评价。结果41例急性自发性颅内出血中,MSCTA检查出颅内动脉瘤11例、脑动静脉畸形4例、脑动静脉畸形伴巢内动脉瘤1例;MSCTA对动脉瘤的瘤体大小、瘤颈、载瘤动脉和脑动静脉畸形的部位、大小、瘤巢的形态、供血动脉和引流静脉的显示均较清楚。7例动脉瘤行钛夹夹闭术和2例脑动静脉畸形、1例脑动静脉畸形伴巢内动脉瘤行手术切除,手术所见与术前MSCTA表现相符;术后行MSCTA复查,显示夹闭动脉瘤之钛夹位置正常,载瘤动脉、颅内大血管通畅,脑动静脉畸形之瘤巢已切除。结论MSCTA是急性自发性颅内出血病因诊断的一种无创伤、快捷有效的影像学方法,并且在颅内动脉瘤、脑动静脉畸形术后评价方面也具有临床应用价值。     

Pseudoaneurysm formation secondary to spontaneous thrombosis of a massive cerebral arteriovenous malformation

Summary A case of a large cerebral arteriovenous malformation (AVM) with spontaneous partial thrombosis and intracerebral hematoma is reported. The unusual and unique features of the radionuclide brain scan and cerebral angiogram are described. The characteristic angiographic features of residual tortuosity and dilatation or pseudoaneurysm formation at the bifurcations of the feeding arteries in a partially thrombosed cerebral AVM have not been described previously in the literature.     

Acute and chronic swine rete arteriovenous malformation models: hemodynamics and vascular remodeling

BACKGROUND AND PURPOSE: An acute and a chronic arteriovenous malformation (AVM) model were developed by using the swine rete to study hemodynamics and vascular remodeling. The models were also used to study in vivo polymerization kinetics and the distribution of various N-butyl 2-cyanoacrylate (NBCA) and Lipiodol mixtures. METHODS: In the acute swine AVM model, retrograde flow through the left side of the rete was created by the placement of an endovascular shunt through the ipsilateral ascending pharyngeal artery. In the chronic model, flow was redirected retrograde through the left side of rete and ascending pharyngeal artery by creating an arteriovenous fistula between the ipsilateral jugular vein and the common carotid artery. After a period of at least 6 months, the entire head with the rete was connected to a perfusion loop driven by a peristaltic pump. A total of 30 swine were used for both the acute (n = 23) and chronic groups (n = 7). Hemodynamic parameters, including the flow and pressure drop across the rete, were recorded before NBCA embolization. Image processing was used on high-resolution radiographs of the explanted retia to measure the total rete length. Measurements of rete vessel calibers were based on histology. RESULTS: The pressure gradients across retia were higher in the chronic model than in the acute model, but they did not reach the level of statistical significance (23.7 +/- 12.0 mm Hg vs 15.4 +/- 1.4 mm Hg). The rete blood outflow was significantly higher in the chronic model compared with the acute one (139.9 +/- 100.3 mL/min vs 32.5 +/- 17.6; P = .03). The rete length in the chronic model was significantly higher than in the acute model (593.1 +/- 39.9 vs 401.3 +/- 65.2 pixel; P < .001). The average vessel diameter of the rete in the chronic group was 520 microm and 320 microm in the control animals. CONCLUSION: Increased pressure gradients and flow in the chronic swine rete AVM model may be related to increased size and decreased impedance. The resulting hemodynamic changes reflect a true flow-induced vascular remodeling rather than a simple change related to aging and size of the animal.     

Spontaneous occlusion of a cerebral arteriovenous malformation: angiography and MR imaging follow-up and review of the literature

We present the angiographic and MR imaging course of a 62-year-old man with a right parietal high-flow arteriovenous malformation (AVM), which was diagnosed because of seizures. A spontaneous, complete, and asymptomatic occlusion of the AVM was confirmed by a second angiography 3 months later. The possible mechanisms leading to the occlusion are discussed, and a brief review of the literature is given.     

Intranidal aneurysms in cerebral arteriovenous malformations: evaluation and endovascular treatment.

Patients with cerebral arteriovenous malformations (AVMs) have an increased risk of hemorrhage if an intranidal aneurysm is present. Angiograms from 125 patients with cerebral AVMs were evaluated, and 15 (12%) had intranidal aneurysms. All 15 patients had a history of bleeding. Five patients underwent particulate or liquid embolization before surgical excision of or radiation therapy for the AVM. All aneurysms were thrombosed at the time of embolization. Ten patients underwent radio-surgery alone. Eight of the 10 underwent angiographic follow-up (mean, 33 months); seven patients showed complete obliteration of the AVM without residual aneurysm. Histologic evaluation showed intranidal aneurysms to be thin-walled vascular structures, and they are the likely site for AVM hemorrhage. Embolization is an effective method for achieving thrombosis of the intranidal aneurysm and may be beneficial in patients undergoing radiation therapy because of a long latency period between treatment and thrombosis of the AVM.     

Transcranial colour Doppler sonography in emergency management of intracerebral haemorrhage caused by an arteriovenous malformation: case report

We present a case which demonstrates the use of transcranial colour Doppler (TCCD) sonography in screening for an underlying arteriovenous malformation (AVM) in a middle-aged hypertensive patient with a spontaneous thalamic haematoma. The AVM was not detected on emergency CT but its presence, site and shape were demonstrated by TCCD, in the presence of a massive cerebral haemorrhage and acute intracranial hypertension. Received: 1 March 2000/Accepted: 17 April 2000     

三维数字减影血管造影技术诊断脑血管疾病的应用价值

目的评价三维数字减影血管造影(3D—DSA)技术诊断脑血管疾病的应用价值。方法对临床怀疑和确诊为脑血管疾病的71例患者行常规脑血管数字减影造影(DSA)和3D—DSA。结果本组共检查71例,经3D—DSA技术共检出动脉瘤44例64枚、颅内动静脉畸形(AVM)19例、血管狭窄致脑缺血8例(6例颈内动脉狭窄、大脑前动脉闭塞)。结论3D—DSA诊断脑血管疾病具有极大的临床应用价值。尤其对颅内动脉瘤、AVM、血管狭窄的诊断最为准确、快速、安全。     

Can Induction of Systemic Hypotension Help Prevent Nidus Rupture Complicating Arteriovenous Malformation Embolization?: Analysis of Underlying Mechanisms Achieved Using a Theoretical Model

BACKGROUND AND PURPOSE: Nidus rupture is a serious complication of intracranial arteriovenous malformation (AVM) embolotherapy, but its pathogenetic mechanisms are not well described. An AVM model based on electrical network analysis was used to investigate theoretically the potential role of hemodynamic perturbations for elevating the risk of nidus vessel rupture (Rrupt) after simulated AVM embolotherapy, and to assess the potential benefit of systemic hypotension for preventing rupture. METHODS: Five separate hypothetical mechanisms for nidus hemorrhage were studied: 1) intranidal rerouting of blood pressure; 2) extranidal rerouting of blood pressure; 3) occlusion of draining veins with glue; 4) delayed thrombosis of draining veins; and 5) excessively high injection pressures proximal to the nidus. Simulated occlusion of vessels or elevated injection pressures were implemented into the AVM model, and electrical circuit analysis revealed the consequent changes in intranidal flow, pressure, and Rrupt for the nidus vessels. An expression for Rrupt was derived based on the functional distribution of the critical radii of component vessels. If AVM rupture was observed (Rrupt > or = 100%) at systemic normotension (mean pressure [P] = 74 mm Hg), the theoretical embolization was repeated under systemic hypotension (minor P = 70 mm Hg, moderate P = 50 mm Hg, or profound P = 25 mm Hg) to assess the potential benefit of this maneuver in reducing hemorrhage rates. RESULTS: All five pathogenetic mechanisms under investigation were able to produce rupture of AVMs during or after embolotherapy. These different mechanisms had in common the capability of generating surges in intranidal hemodynamic parameters resulting in nidus vessel rupture. The theoretical induction of systemic hypotension during and after treatment was shown to be of significant benefit in attenuating these surges and reducing Rrupt to safer levels below 100%. CONCLUSION: The induction of systemic hypotension during and after AVM embolization would appear theoretically to be of potential use in preventing iatrogenic nidus hemorrhage. The described AVM model should serve as a useful research tool for further theoretical investigations of AVM embolotherapy and its hemodynamic sequelae.     

Stereotactic radiosurgery for brain arteriovenous malformations: quantitative MR assessment of nidal response at 1 year and angiographic factors predicting early obliteration

Introduction We investigated the role of magnetic resonance angiography (MRA) in the early follow-up of patients after stereotactic radiosurgery (STRS) for cerebral arteriovenous malformations (AVMs) and determined the influence of individual morphological factors of AVMs in early response to treatment.Methods A group of 40 patients (41 AVMs) consented to a dedicated 1.5-T MR protocol 12 months after receiving STRS for a brain AVM. In addition to standard spin echo sequences, 3-D contrast-enhanced sliding interleaved Ky MRA (CE-SLINKY) and dynamic time-resolved subtraction angiography (MR-DSA) were performed. Nidal volumes were calculated using CE-SLINKY data in patients with a persisting arteriovenous shunt. Planning angiographic data was investigated in all 40 patients. The following AVM factors were used in the statistical analysis to determine their role in nidus obliteration: (1) maximum linear dimension, (2) nidal volume, (3) AVM location (4) nidal morphology, (5) venous drainage, (6) “high-flow angiographic change”, (7) prior embolization, and (8) dose reduction.Results Complete nidal obliteration was found in 9 patients, 26 showed greater than 50% nidal reduction and 6 had less than 50%. Two AVM factors, venous drainage and AVM location, were found to significantly correlate with rate of obliteration.Conclusion We successfully demonstrated the use of MRA to quantitatively assess the response of AVMs to STRS. Two AVM factors, venous drainage and AVM location were found to correlate with rate of obliteration prior to the application of the Bonferroni correction, but if this more rigorous statistical test was applied then none of the factors was found to be significant.     

头面部复杂动静脉畸形的栓塞治疗

目的　研究经导管栓塞技术在头面部动静脉畸形治疗中的应用。方法　 3 0例头面部动静脉畸形患者共接受 40次栓塞治疗。其中使用国产TH胶栓塞者为 18例 2 0次 ,使用进口PVA微粒栓塞者为 12例 2 0次。结果　 3 0例患者均成功实行瘤灶供血动脉栓塞术。所有患者栓塞术后临床症状明显改善 ,如瘤体缩小甚至消失 ,皮温降低 ,搏动感和血管杂音减弱或消失等。术后随访3～ 6个月 ,12例复发。全部病例均无严重并发症。结论　对于头面部动静脉畸形的患者来说 ,经导管栓塞术是一种较好的非手术治疗方法 ,在栓塞剂的选择方面 ,则以PVA微粒栓塞更为理想。     

Histopathologic characteristics of a chronic arteriovenous malformation in a swine model: preliminary study

BACKGROUND AND PURPOSE: The experimental induction of histologic transformations in microvessels of similar caliber to those of nidus vessels of cerebral arteriovenous malformations (AVMs) has not been attempted previously. Our goal was to examine preliminarily the histopathologic characteristics of nidus vessels and the angiographic features of a chronic AVM model in swine. METHODS: AVM models were fashioned from bilateral carotid retia mirabilia of seven swine after the surgical formation of large unilateral carotid-jugular fistulas. One AVM model was made for immediate use, whereas in the other six, follow-up angiography was obtained at varying intervals (2 to 180 days) after model creation. Light and electron microscopy, immunohistochemistry (using monoclonal antibodies against smooth muscle actin and PC10 against proliferating cell nuclear antigen), and histometry were performed on the nidus vessels of three swine: one acutely created, one 2 months old, and one 6 months old. RESULTS: Vascular dilatation and tortuosity of the main arterial feeder and draining vein were evident angiographically as early as 4 days after AVM creation, and were maximal in the 6-month-old model. Compared with the acutely created nidus vessels, those in the two chronic models revealed disrupted and attenuated elastica and intimal hyperplasia that was focal ("cushions") or generalized, leading to luminal occlusion. Variable numbers of cells in the tunica media of chronic nidus vessels contained smooth muscle actin. PC10/proliferating cell nuclear antigen immunoreactivity was observed in the endothelium and subendothelial layers. Histometry showed increases in intimal hyperplasia and medial thickness in the chronic vessels. CONCLUSION: Nidus vessels in this chronic swine AVM model exhibited striking histologic changes similar to those seen in cerebral AVMs. The induced vessel growth seen angiographically and histologically in components of the chronic AVMs was consistent with the presence of persistently raised intravascular hemodynamic loads. This preliminary feasibility study suggests that the realistic histologic characteristics of this chronic AVM model are an attractive feature, and if confirmed in future, more comprehensive, studies would be of benefit in accurate histopathologic interpretation of the effects of superimposed experimental embolotherapy or radiosurgery. This model may provide a useful experimental tool to study the dynamic cellular and tissue events that dictate the development and natural history of AVMs.     

Color Doppler flow imaging of the normal and abnormal orbit

Twenty-six normal orbits (16 subjects) and seven patients with suspected orbital disease were studied with color Doppler flow imaging CDFI). Arterial structures consistently identified included the ophthalmic artery, central retinal artery, and posterior ciliary branches. The terminal lacrimal branch was seen in the majority of orbits (n = 19). Venous structures consistently seen included the central retinal vein and venae vorticosae; the superior ophthalmic vein was identified in the majority of normal orbits (n = 22). Response of the superior ophthalmic vein to the Valsalva maneuver was assessed in six of the normal subjects (12 orbits). Retrograde flow was typically seen during the maneuver and accentuated antegrade flow after cessation of the maneuver. Pathologic entities correctly diagnosed with CDFI included a dural arteriovenous malformation (AVM) with spontaneous carotid-cavernous fistula, an orbital AVM, and superior ophthalmic vein thrombosis. Vascular lesions were excluded in two patients with orbital masses. Bilaterally enlarged superior ophthalmic veins were identified in a patient with unilateral symptoms suggestive of a varix; CDFI results were confirmed with computed tomography, but orbital venograms were interpreted as normal. These findings suggest that CDFI may be helpful in the evaluation of suspected vascular orbital disease.