Redefined role of angiogenesis in the pathogenesis of dural arteriovenous malformations

Ephrin B2 and EphB4 selectively mark arterial and venous vessels in cerebral arteriovenous malformation

OBJECTIVES

Ephrin type B receptor 4 (EphB4, Eph receptor) selectively binds ephrin B2 (Eph ligand). EphB4/ephrin B2 is involved in embryonic vessel development, vascular remodelling and pathological vessel formation in adults (including tumour angiogenesis). Binding of vascular endothelial growth factor (VEGF)-A to the endothelial-specific receptor VEGF receptor-2 is the main extracellular signal triggering angiogenic response. Little is known about the role of EphB4/ephrin B2 during angiogenesis and arteriovenous plasticity in cerebral arteriovenous malformation (cAVM). This study investigated EphB4 and ephrin B2 expression in cAVM.

METHODS

Haemorrhagic (H-AVM) and nonhaemorrhagic (NH-AVM) specimens of AVM nidus, obtained after microsurgical cAVM resection, and normal superficial temporal artery (STA) specimens, were analysed retrospectively. VEGF-A, EphB4 and ephrin B2 expression were studied by immunohistochemistry and immunoblotting.

RESULTS

In cAVM (10 H-AVM; 10 NH-AVM), VEGF-A was immunocytochemically localized to endothelial cells; strong endothelial cell staining was found for EphB4 in veins and ephrin B2 in arteries. Normal STA (n = 10) did not express EphB4 or ephrin B2. EphB4 and ephrin B2 expression was greater in H-AVM than in NH-AVM.

CONCLUSIONS

Endothelial cells are more active in H-AVM than NH-AVM. EphB4 and ephrin B2 play important roles in neovascularization and arteriovenous differentiation/plasticity. These data provide new insights into the aetiology of cAVM and lay a foundation for further study. The notch pathway induced by VEGF-A may be a key signalling pathway in this process.

Endovascular biopsy: evaluating the feasibility of harvesting endothelial cells using detachable coils

The absence of safe and reliable methods to harvest vascular tissue in situ limits the discovery of the underlying genetic and pathophysiological mechanisms of many vascular disorders such as aneurysms. We investigated the feasibility and comparable efficacy of endothelial cell collection using a spectrum of endovascular coils. Nine detachable coils ranging in k coefficient (0.15-0.24), diameter (4.0 mm-16.0 mm), and length (8.0 cm-47.0 cm) were tested in pigs. All coils were deployed and retrieved within the iliac artery of pigs (three coils/pig). Collected coils were evaluated under light microscopy. The total and endothelial cells collected by each coil were quantified. The nucleated cells were identified by Wright-Giemsa and DAPI stains. Endothelial and smooth muscle cells were identified by CD31 and α-smooth muscle actin antibody staining. Coils were deployed and retrieved without technical difficulty. Light microscopy demonstrated sheets of cellular material concentrated within the coil winds. All coils collected cellular material while five of nine (55.6%) coils retrieved endothelial cells. Coils collected mean endothelial cell counts of 89.0±101.6. Regression analysis demonstrated a positive correlation between increasing coil diameter and endothelial cell counts (R(2)=0.52, p = 0.029). Conventional detachable coils can be used to harvest endothelial cells. The number of endothelial cells collected by a coil positively correlated with its diameter. Given the widespread use of coils and their well-described safety profile their potential as an endovascular biopsy device would expand the availability of tissue for cellular and molecular analysis.

Directional Intraoperative Doppler Ultrasonography During Surgery on Cranial Dural Arteriovenous Fistulas

BACKGROUND:

Directional intraoperative Doppler (dioDoppler) ultrasonography is well established as a tool in the surgery of intracranial aneurysms and cerebral arteriovenous malformations. The literature provides little information about the possible usefulness of this method during surgery on cranial dural arteriovenous fistulas (dAVFs).

OBJECTIVE:

To present our experience with the use of dioDoppler during surgery on cranial dAVFs.

METHODS:

All patients undergoing craniotomy for cranial dAVF from January 2007 to October 2012 in which dioDoppler was used were included in the study. We reviewed patient records, operating protocols, radiological images, dioDoppler files, and intraoperative videos.

RESULTS:

During the study period, 12 patients with cranial dAVFs underwent surgical treatment facilitated by dioDoppler. Four patients were operated on acutely for cerebral bleeds, and 8 patients were treated for various cerebral symptoms and the assumption of a significant risk for intracranial bleed. Three advantages of dioDoppler were unequivocal identification of veins with cortical/deep venous reflux from the fistula, verification of completeness of occlusion of the fistula, and identification of dural arterial feeders not visualized under the microscope.

CONCLUSION:

Reviewing our experience, we found that dioDoppler sonography is an easy, safe, effective, reliable, and instantaneous tool during surgery on cranial dAVFs.

Endovascular treatment of cerebral dural and pial arteriovenous fistulas

Dural arteriovenous fistulas (DAVFs) are arteriovenous shunts from a dural arterial supply to a dural venous channel, typically supplied by pachymeningeal arteries and located near a major venous sinus. Pial arteriovenous fistulas (PAVFs) are composed of one or more arterial feeders draining into a single vein in the absence of an intervening nidus. Fistulas manifesting features of high risk for rupture should be treated aggressively, the spectrum of treatment varies from endovascular, surgical resection, and stereotactic radiosurgery. This article describes the natural history, clinical presentation, and treatment of dural and pial fistulas, with emphasis on endovascular treatment.

Down but not out

A 20-year-old Hispanic man with Down syndrome presented with progressively worsening headache, fluctuating decreased vision, and bilateral optic disk edema. Magnetic resonance imaging of the head showed an empty sella, and magnetic resonance venography showed thrombosis of left transverse and sigmoid sinuses. Catheter angiography angiogram showed a dural arteriovenous fistula in the wall of left transverse and sigmoid sinuses. The patient underwent Onyx endovascular embolization of the fistula, resulting in its angiographic obliteration, followed by resolution of his clinical signs and symptoms.

Intracerebral pial arteriovenous fistula with large venous varix: A rare case report

BACKGROUND

Intracerebral pial arteriovenous fistulas (AVFs) are rare vascular lesions of the brain. These lesions are composed of one or more direct arterial connection to a single venous channel without true intervening nidus and usually have associated venous varix or giant venous aneurysms. Intracerebral varices are occasionally associated with high-flow AVF, and usually treated by interrupting the feeding arteries leaving the varices intact.

CASE DESCRIPTION

We report a rare case of a 24-year-old male with a single-channel pial AVF of the left cerebral hemisphere, which was fed by the left anterior cerebral artery (ACA) and was associated with large venous varix and continuous varicose venous dilatation. This superficially located varix was over 6 cm in diameter posing significant mass effect and had calcified walls. Direct surgical flow disconnection followed by removal of large varix resulted in complete disappearance of pial AVF without complication.

CONCLUSION

Though endovascular occlusion of feeding arteries offers a simple and safe option, direct surgical removal should be considered in rare cases of intracerebral superficially located large AVF with calcified wall and mass effect.

Endovascular management of intracranial dural arteriovenous fistulas: a review

Dural arteriovenous fistulas (DAVFs) are rare pathological entities presenting with a diverse clinical course, ranging from benign to life-threatening. Digital subtraction angiography remains the gold standard in the diagnosis of clinically suspected DAVFs. This article reviews the ethiopathogenesis, natural history, classification systems, clinical and angiographic features, and the current treatment strategies for these complex lesions. The management of DAVFs may include conservative treatment, endovascular intervention, microsurgery, and stereotactic radiosurgery. A multidisciplinary approach involving a neurosurgeon, interventional neuroradiologist, and neurologist is required before considering any type of treatment modality. The indication for the best therapeutic alternative must be individualized for each patient.

Concurrent dural and perimedullary arteriovenous fistulas at the craniocervical junction: case series with special reference to angioarchitecture

OBJECT

Dural arteriovenous fistulas (DAVFs) and perimedullary arteriovenous fistulas (PAVFs) are uncommonly associated in the craniocervical junction. The purpose of this study was to describe the clinical and angiographic characteristics of such concurrent lesions.

METHODS

Authors reviewed 9 cases with a coexistent DAVF and PAVF at the craniocervical junction. Clinical presentation, angiographic characteristics, intraoperative findings, and treatment outcomes were assessed.

RESULTS

All patients (male/female ratio 5:4; mean age 66.3 years) presented with subarachnoid hemorrhage. Angiography revealed that 8 patients had both a DAVF and PAVF on the same side, whereas 1 patient had 3 arteriovenous fistulas, 1 DAVF, and 1 PAVF on the right side and 1 DAVF on the left side. All of the fistulas shared dilated perimedullary veins (anterior spinal vein, 7 cases; anterolateral spinal vein, 2 cases) as a main drainage route. The shared drainage route was rostrally directed in 8 of 9 cases. Eight patients exhibited an arterial aneurysm on the distal side of the feeding arteries to the PAVF, and the aneurysm in each case was intraoperatively confirmed as a bleeding point. One patient had ruptured venous ectasia at the perimedullary fistulous point. All patients underwent direct surgery via a posterolateral approach. No recurrence was observed in the 4 patients who underwent postoperative angiography, and no rebleeding event was recorded among any of the 9 patients during the follow-up period (mean 38.4 months).

CONCLUSIONS

The similarity of the angioarchitecture and the close anatomical relationship between DAVF and PAVF at the craniocervical junction suggested that these lesions are pathogenetically linked. The pathophysiological mechanism and anatomical features of these lesions represent a unique vascular anomaly that should be recognized angiographically to plan a therapeutic strategy.

Familial Intracranial Dural Arteriovenous Fistulas

BACKGROUND AND IMPORTANCE:

Intracranial dural arteriovenous fistulas (DAVFs) are acquired abnormal communications between dural arteries and veins. Risk factors for development include sinus thrombosis and hypercoagulability, such as occurs in heritable thrombophilias. While there have been reports of other types of vascular anomalies (such as cavernous and arteriovenous malformations) occurring in families, to our knowledge there have been no reports of familial intracranial DAVFs. We describe the first 2 cases of intracranial DAVFs occurring in first-degree relatives.

CLINICAL PRESENTATION:

A 66-year-old woman presented with an 18-month history of bilateral pulsatile tinnitus. Neurological examination was significant for a prominent pulsatile bruit over the left mastoid region. Laboratory studies demonstrated heterozygosity for Prothrombin G20210A mutation. Imaging disclosed a large left Type I Borden DAVF involving the distal transverse-sigmoid sinus junction. She underwent uncomplicated stereotactic radiosurgery to the fistula that led to complete resolution of her tinnitus and the fistula. A 73-year-old woman, the sister of the previous patient, presented with a 24-month history of pulsatile tinnitus affecting the left ear. Laboratory studies demonstrated heterozygosity for the Prothrombin G20210A mutation. Imaging revealed a left Type I Borden DAVF involving the left transverse and sigmoid sinuses. The patient's symptoms resolved spontaneously without treatment. Repeat imaging revealed interval involution of the fistula.

CONCLUSION:

We describe 2 sisters who were heterozygous for Prothrombin G20210A mutation and found to have DAVFs. Clinicians should be aware of the potential for these fistulas to congregate in first-degree relatives via heritable thrombophilias such as the Prothrombin G20210A mutation.

Iatrogenic Vascular Complications Associated With External Ventricular Drain Placement: A Report of 8 Cases and Review of the Literature

BACKGROUND:

Placement of an external ventricular drain (EVD) is a commonly performed and often lifesaving procedure. Although hemorrhage is one of the commonest complications associated with the procedure, ventricular catheter–induced vascular injury is rarely reported.

OBJECTIVE:

To describe 9 cases of EVD-related vascular trauma: 7 arteriovenous fistulas and 2 traumatic aneurysms.

METHODS:

During a 3-year period, 299 patients had EVDs placed. Eight patients (2.75%), 3 male and 5 female (mean age, 48 ± 20 years), developed vascular lesions associated with EVDs. Six patients developed arteriovenous fistulas and 2 patients developed a traumatic aneurysm. The arterial feeders of 5 superficial draining fistulas arose from the middle meningeal artery, and the arterial feeder of a deep-draining fistula originated from a lenticulostriate artery. One traumatic aneurysm arose from a distal branch of the anterior cerebral artery, and the second from a branch of the superficial temporal artery. Four of the superficial fistulas were treated with transarterial embolization.

RESULTS:

Two superficial fistulas and the deep-draining fistula resolved spontaneously after EVD removal. The intracranial aneurysm was embolized with Onyx18, and the superficial temporal artery aneurysm was managed conservatively. There were no hemorrhages associated with any of these vascular lesions and no complications after treatment.

CONCLUSION:

Our data suggest that iatrogenic vascular trauma associated with EVD insertions (2.75%) may be more common than is currently appreciated. Endovascular treatment is effective and may be necessary when these lesions do not resolve spontaneously.

Endovascular management of sigmoid sinus dural arteriovenous fistula associated with sinus stenosis in an infant

A 4-month-old female presented with a dural arteriovenous fistula (DAVF), which was successfully managed using endovascular techniques. There are very few case series reporting DAVF in infants younger than 12 months and, to our knowledge, only 60 pediatric patients with DAVF have been reported to date. Although most DAVF have a benign course, they can result in life-threatening hemorrhage. Endovascular therapies are usually indicated in the management of these neurosurgical vascular malformations. Endovascular therapy of DAVF in neonatal patients presents some major issues. Gaining arterial access may be problematic in femoral arteries too small for the introduction of a sizeable guiding catheter. The volumes of contrast and infused fluids must be carefully monitored to prevent fluid overload. Radiation exposure should be restricted as far as possible. This report contributes to the limited body of evidence on neonatal DAVF and its endovascular management.

Anesthesia for endovascular neurosurgery and interventional neuroradiology

This article outlines the roles of the anesthesiologist in the management of patients undergoing invasive endovascular procedures to treat vascular diseases, primarily of the central nervous system. This practice is usually termed interventional neuroradiology or endovascular neurosurgery. The article emphasizes perioperative and anesthetic management strategies to prevent complications and minimize their effects if they occur. Planning the anesthetic and perioperative management is predicated on understanding the goals of the therapeutic intervention and anticipating potential problems.

A comparative analysis of the osteogenic effects of BMP-2, FGF-2, and VEGFA in a calvarial defect model

The utilization of growth factors for bone regeneration is a widely studied field. Since the approval of bone morphogenetic protein-2 (BMP-2) for therapeutic use in humans, the concept of utilizing growth factors for bone regeneration in translational medicine has become even more attractive. Despite many studies published on individual growth factors in various bone models, comparative analysis is largely lacking. The aim of our study was to compare three different proosteogenic factors under identical in vivo conditions. Thus, we tested the bone regeneration capacity of the three different growth factors BMP-2, fibroblast growth factor-2 (FGF-2), and vascular endothelial growth factor A (VEGFA) in a calvarial defect model. We demonstrated that BMP-2 and VEGFA had similar bone healing capacities, resulting in complete calvarial healing as early as week 3. FGF-2 also showed a significantly higher bone regeneration capacity; however, the healing rate was lower than with BMP-2 and VEGFA. Interestingly, these findings were paralleled by an increased angiogenic response upon healing in BMP-2- and VEGFA-treated calvarial defects as compared with FGF-2. Immunohistochemistry for proliferating and osteoprogenitor cells revealed activity at different points after surgery among the groups. In conclusion, we demonstrated an efficient bone regeneration capacity of both BMP-2 and VEGFA, which was superior to FGF-2. Moreover, this study highlights the efficient bone regeneration of VEGFA, which was comparable with BMP-2. These data provide a valuable comparative analysis, which can be used to further optimize growth factor-based strategies in skeletal tissue engineering.

A case of pial arteriovenous fistula with giant venous aneurysm and multiple varices treated with coil embolization

Intracranial pial arteriovenous fistulas (AVFs) are rare vascular lesions of the brain. These lesions consist of one or more arterial connection to a single venous channel without true intervening nidus. A 24-year-old woman visited to our hospital because of headache, vomiting, dizziness and memory disturbance that persisted for three days. She complained several times of drop attack because of sudden weakness on both leg. Cerebral angiograms demonstrated a giant venous aneurysm on right frontal lobe beyond the genu of corpus callosum, multiple varices on both frontal lobes fed by azygos anterior cerebral artery, and markedly dilated draining vein into superior sagittal sinus, suggesting single channel pial AVF with multiple varices. Transarterial coil embolization of giant aneurysm and fistulous portion resulted in complete disappearance of pial AVF without complication.

Mixed pial-dural arteriovenous malformation in the anterior cranial fossa--two case reports

Most arteriovenous malformations (AVMs) associated with the meningeal artery in the anterior cranial fossa are the pure dural type, and mixed pial-dural AVMs are rare. Two types of mixed pial-dural AVM occur in the anterior cranial fossa according to the shunting point: one with the nidus in the brain parenchyma of the frontal lobe, and the other with the shunting point in the dura mater. We describe two patients with AVMs fed by the anterior ethmoidal arteries and the persistent primitive olfactory artery, with the nidus located in the pure brain parenchyma of the inferior aspect of frontal lobe, and drained via an abnormal cortical vein into the cavernous and superior sagittal sinuses. The importance of occluding the venous outflow to obliterate intracranial dural arteriovenous fistula (AVF) is emphasized. However, removal of the nidus in the brain parenchyma is required. The presence of a pial feeder should be considered before diagnosis of dural AVF of the anterior cranial fossa, and preoperative detailed evaluation for the pial supply and shunting point is mandatory.

Thrombophilia Due to Factor V and Factor II Mutations and Formation of a Dural Arteriovenous Fistula: Case Report and Review of a Rare Entity

Genetic mutations underlying thrombophilia are often recognized in patients with thromboembolic episodes. However, the clinical and therapeutic implications of such findings often remain unclear. We report the first case of a dural arteriovenous fistula (DAVF) in a patient with a combined factor II and factor V Leiden mutation. A 40-year-old man presented with a large left temporal and intraventricular hemorrhage. An initial angiogram showed thrombosis of the left sigmoid sinus but no evidence of a vascular malformation. One year after the hemorrhage, an angiographic study showed the appearance of a right DAVF. During the follow-up period, the patient was found to harbor heterozygosity for a mutation of factor V and a mutation of factor II. Recognition of the patient's thrombophilia led to prolonged oral anticoagulation therapy to reduce the risk of a recurrent thrombotic episode. Despite the increased risk of bleeding, the therapy was considered justified. DAVFs may occur after sinus thrombosis in patients with combined factor II and factor V mutations. This observation indicates the association of multiple hematological disorders with DAVFs in individual patients. Moreover, it raises the clinical conundrum of how to manage patients with thrombophilia, intracranial hemorrhage, and DAVFs.

Mechanism of the formation of dural arteriovenous fistula: the role of the emissary vein

Dural arteriovenous fistula (DAVF) can be separated into two types: DAVF which drains through an affected sinus (sinus type) and DAVF with direct reflux to the cortical vein (non-sinus type). The present report attempted to clarify the mechanism of formation and development of DAVF focusing on the emissary vein (EV) hypothesis.First, inflammation occurs at the penetrating point of the EV on the dura due to idiopathic or secondary causes. Local inflammatory reactions induce vessel dilatation and neovascularization, and subsequently create arteriovenous (AV) connections on the arteriole level. Although EV communicating with dural arteries might play a role as draining routes at first, they start to degrade due to compression of enlarged emissary arteries or to a hemodynamic shift to the drainage pathway of least resistance. Following the occlusion of drainage pathway through EV into the sinus or cortical veins may form, resulting in clinically detectable DAVF. The AV shunt then expands to the surrounding dura associated with recruitment of feeders from distant sites induced by expression of angiogenetic factors and a shift in the hemodynamic balance. In sinus type DAVF, the sinus is progressively compartmentalized and finally occludes due to thrombogenesis with activated coagulopathy or to hemodynamic hypertrophy of the sinus wall. This progression results in the mature, aggressive DAVF with drainage impairments. Previous mechanistic hypotheses focusing on sinus hypertension and sinus thromboses cannot explain the pathogenesis of non-sinus type of DAVF. Although the etiology of DAVF may be concerned by the thrombo-occlusive change of sinus, the unique theory presented in this report may enable an understanding of the common etiology of both types of DAVF.

Microsurgery can cure most intracranial dural arteriovenous fistulae of the sinus and non-sinus type

There is consensus that intracranial dural arteriovenous fistulae (dAVF) with direct (non-sinus-type) or indirect (sinus-type) retrograde filling of a leptomeningeal vein should be treated due to the high risk of neurological deficits and hemorrhage. No consensus exists on treatment modality (surgery and/or embolization) and, if surgery is performed, on the best surgical strategy. This series aims to evaluate the role of surgery in the management of aggressive dAVFs. Forty-two patients underwent surgery. Opening and packing the sinus with thrombogenic material was performed in 9 of the 12 sinus-type dAVFs. In two sinus-type fistulae of the cavernous sinus and 1 of the torcular, microsurgery was used as prerequisite for subsequent embolization by providing access to the sinus. In the 30 non-sinus-type dAVFs, surgery consisted of interruption of the draining vein at the intradural entry point. In 41 patients undergoing 43 operations, elimination of the dAVF was achieved (97.6%). In one case, a minimal venous drainage persisted after surgery. The transient surgical morbidity was 11.9% (n = 5) and the permanent surgical morbidity 7.1% (n = 3). Our surgical strategy was to focus on the arterialized leptomeningeal vein in the non-sinus-type and on the arterialized sinus segment in the sinus-type dAVFs allowing us to obliterate all but one dAVF with a low morbidity rate. We therefore propose that microsurgery should be considered early in the treatment of both types of aggressive dAVFs. In selected cases of cavernous sinus dAVFs, the role of microsurgery is reduced to that of an adjunct to endovascular therapy.

CT angiography as a screening tool for dural arteriovenous fistula in patients with pulsatile tinnitus: feasibility and test characteristics

BACKGROUND AND PURPOSE

The diagnosis of intracranial DAVF with noninvasive cross-sectional imaging such as CTA is challenging. We sought to determine the sensitivity and specificity of CTA compared with cerebral angiography for DAVF in patients presenting with PT.

MATERIALS AND METHODS

Following approval of the institutional review board, we reviewed all patients who underwent CTA for PT from 2004 to 2009 and collected clinical and imaging data. Seven patients with PT and proved DAVF and 7 age- and sex-matched control patients with PT but no DAVF composed the study group. CTA images were blindly interpreted by 2 experienced neuroradiologists for the presence of 5 variables: asymmetric arterial feeding vessels, "shaggy" appearance of a dural venous sinus, transcalvarial venous channels, asymmetric venous collaterals, and abnormal size and number of cortical veins. Asymmetric attenuation of jugular veins was additionally assessed.

RESULTS

The presence of arterial feeders showed good test characteristics for screening, with a sensitivity of 86% (95% CI, 42-99) and a specificity of 100% (95% CI, 52-100). A shaggy sinus or tentorium was highly specific: sensitivity of 42% (95% CI, 11-79) and specificity of 100% (95% CI, 56-100). The presence of transcalvarial venous channels demonstrated a poor sensitivity of 29% (95% CI, 5-70) but a high specificity 86% (95% CI, 42-99). CT attenuation of the jugular veins showed statistically significant asymmetry in the DAVF group versus the control group (P < .05).

CONCLUSIONS

CTA can be used to screen for DAVF in patients with PT. The presence of asymmetrically visible and enlarged arterial feeding vessels has a high sensitivity and specificity for the diagnosis of DAVF.

Management of dural arteriovenous fistulas - Helsinki and Kuopio experience

Dural arteriovenous fistulas (DAVFs) are complex disorders, some of them with aggressive clinical behaviour. During past decades their treatment strategy has changed due to increased knowledge of their pathophysiology and natural history, and advances in treatment modalities. In asymptomatic cases or cases with mild symptoms in the absence of cortical venous drainage (CVD) no treatment is necessarily required, whereas aggressive DAVFs should be treated promptly by endovascular or microsurgical means.In our series of 323 patients with 333 fistulas, treated in two neurosurgical units in Finland since 1944, there were 265 true DAVFs and 68 Barrow type A caroticocavernous fistulas. Among the DAVFs there was a slight female predominance, 140 women (55%) and 115 men (45%), and the majority of the cases were located in the area of transverse and sigmoid sinuses. Mode of treatment in the early series was proximal ligation of feeding artery, and later craniotomy, endovascular treatment and radiosurgery, or combination of these treatments, with total occlusion rate being 53%.

The putative role of the venous system in the genesis of vascular malformations

Recent clinical and experimental evidence has challenged the traditional concept of the venous system as a “passive” element in the genesis and evolution of intracranial vascular malformations. The authors review the clinical and experimental evidence linking the venous system and its anomalies to the genesis of various intracranial vascular malformations, including dural arteriovenous fistulas, cavernous malformations, parenchymal arteriovenous malformations, and capillary telangiectasia. They also describe the potential significance of different associations of these vascular anomalies.

Nonischemic cerebral venous hypertension promotes a pro-angiogenic stage through HIF-1 downstream genes and leukocyte-derived MMP-9

Cerebral venous hypertension (VH) and angiogenesis are implicated in the pathogenesis of brain arteriovenous malformation and dural arteriovenous fistulae. We studied the association of VH and angiogenesis using a mouse brain VH model. Sixty mice underwent external jugular vein and common carotid artery (CCA) anastomosis (VH model), CCA ligation, or sham dissection (n=20). Hypoxia-inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF) and stromal-cell-derived factor-1alpha (SDF-1alpha) expression, and matrix metalloproteinase (MMP) activity were analyzed. We found VH animals had higher (P<0.05) sagittal sinus pressure (8+/-1 mm Hg) than control groups (1+/-1 mm Hg). Surface cerebral blood flow and mean arterial pressure did not change. Hypoxia-inducible factor-1alpha, VEGF, and SDF-1alpha expression increased (P<0.05). Neutrophils and MMP-9 activity increased 10-fold 1 day after surgery, gradually decreased afterward, and returned to baseline 2 weeks after surgery. Macrophages began to increase 3 days after surgery (P<0.05), which coincided with the changes in SDF-1alpha expression. Capillary density in the parasagittal cortex increased 17% compared with the controls. Our findings suggest that mild nonischemic VH results in a pro-angiogenic stage in the brain by upregulating HIF-1 and its downstream targets, VEGF and SDF-1alpha, increasing leukocyte infiltration and MMP-9 activity.

Endovascular occlusion of a ruptured transitional aneurysm associated with a developmental venous anomaly

Developmental venous anomalies (DVAs) represent a rare cause of intraparenchymal hemorrhage. This case demonstrates an unusual DVA associated with venous hypertension, arteriovenous shunting, and a ruptured transitional aneurysm. The authors describe the first use of embolization as a treatment method for an unstable ruptured transitional aneurysm associated with a DVA. This 33-year-old man suffered acute onset of headache, gait ataxia, and left hemiparesis. Computed tomography brain scans demonstrated a deep paramedian right frontal intraparenchymal hemorrhage. No cavernous malformation was apparent on MR imaging. Diagnostic angiography revealed arteriovenous shunting from the right anterior and middle cerebral arteries to a large DVA with an associated arteriovenous fistula, with a 3-mm aneurysm in the transition from pericallosal artery to the collecting vein. Both surgical and endovascular treatment options were considered. The patient underwent repeat angiography on hospital Day 7, at which time the aneurysm had increased to 5 mm, and endovascular treatment was selected. Acrylic occlusion of the aneurysm was performed and confirmed angiographically. The patient's neurological symptoms resolved throughout the hospital stay, and he remains symptom free in the 10 months since treatment. Developmental venous anomalies are not usually associated with arteriovenous shunting and aneurysms as a source of intraparenchymal hemorrhage. Endovascular occlusion of the aneurysm without blockage of physiologically necessary venous structures is a possible method of treatment for this complex mixed vascular lesion, and has proven safe and effective in this patient. To the authors' knowledge, this is the first presentation of this situation in the literature.

Cerebral arteriovenous malformations. Part 2: physiology

Object

The scientific understanding of the nature of arteriovenous malformations (AVMs) in the brain is evolving. It is clear from current work that AVMs can undergo a variety of phenomena, including growth, remodeling, and/or regression—and the responsible processes are both molecular and physiological. A review of these complex processes is critical to directing future therapeutic approaches. The authors performed a comprehensive review of the literature to evaluate current information regarding the genetics, pathophysiology, and behavior of AVMs.

Methods

A comprehensive literature review was conducted using PubMed to reveal the angioarchitecture and cerebral hemodynamics of AVMS as they relate to lesion development.

Results

Feeding artery pressures, brain AVM compartmentalization, venous drainage, flow phenomena, and vascular steal are discussed.

Conclusions

The dynamic nature of brain AVMs is at least in part attributable to hemodynamic and flow-related phenomena. These forces acting on an evolving structure are critical to understanding the challenges in endovascular and surgical therapy. As knowledge in this field continues to progress, the natural history and predicted behavior of these AVMs will become more clearly elucidated.

Possible role of local hypoxia in the de novo formation of dural and osteodural arteriovenous fistulas after encephalitis. A case report

A rare case of de novo formation of dural and osteodural arteriovenous fistulas after encephalitis is presented. We review and discuss the etiological angiogenetic factors and processes in intracranial dural arteriovenous fistulas formation. Local tissue hypoxia may have played a role in the initial step causing sprouting angiogenesis as the main pathogenesis of DAVFs formation.

Angiogenesis and gliomas: current issues and development of surrogate markers

Despite significant improvements, current therapies have yet to cure infiltrative gliomas. Glioma progression is strongly dependent on the development of a new vascular network that occurs primarily by angiogenesis. Hypoxia and genetic anomalies within a glioma trigger the angiogenic switch, thus upregulating angiogenic factors and downregulating antiangiogenic factors. The main factors indicative of angiogenesis are now well known, and more recently, differences based on grade and subtype have been reported. New data also indicate a potential role for postnatal vasculogenesis with bone marrow endothelial progenitors in addition to angiogenesis in tumor vascular development. All of these factors may have therapeutic implications. Antiangiogenic therapies are presently being developed; more than 80 trials are ongoing. Initial results indicate that epidermal growth factor receptor inhibitors, anti-metalloproteases, and thalidomide do not demonstrate strong anti-tumor activity. Thus, antiangiogenic agents combined with conventional therapies and second-generation antiangiogenic drugs for targeting multiple molecular pathways are presently being tested. Clinical experience also demonstrates the failure of conventional imaging to monitor these new approaches accurately. New advances in the design of surrogate markers for angiogenesis have been reported for both magnetic resonance and molecular imaging techniques. This article summarizes the mechanisms of the angiogenic switch based on tumor grade and subtype, reviews completed and ongoing clinical trials, and details the present and the future of surrogate markers for angiogenesis in gliomas.

Anesthesia for endovascular neurosurgery and interventional neuroradiology

This review outlines the roles of anesthesiologists in the management of patients undergoing invasive endovascular procedures to treat vascular diseases, primarily of the central nervous system. This practice usually is termed interventional neuroradiology or endovascular neurosurgery. The discussion emphasizes perioperative and anesthetic management strategies to prevent complications and minimize their effects if they occur. Planning anesthetic and perioperative management is predicated on understanding the goals of the therapeutic intervention and anticipating potential problems.

Expression of angiogenic growth factor in the rat DAVF model

OBJECTIVE

The precise mechanisms responsible for the development and growth of dural arteriovenous fistula (DAVF) remain unclear, but it has been hypothesized that vascular endothelial growth factor (VEGF) might be involved in the pathogenesis. The aim of this study was to examine the expression of VEGF in the rat DAVF model.

METHODS

Forty-five Sprague-Dawley rats were used in two experiments. In Experiment 1 (n = 20, including sham-operated controls), VEGF expression was analysed by Western blots in three different rat DAVF models: model I: common carotid artery-external jugular vein (CCA-EJV) anastomosis (n = 5); model II: sagittal sinus thrombosis and bipolar coagulation of the vein draining the transverse sinus (n = 5); model III: CCA-EJV anastomosis and bipolar coagulation of the vein draining the transverse sinus and sagittal sinus thrombosis to induce venous hypertension (n = 5). Based on the results of Experiment 1, Western blots were performed at weekly intervals 1, 2 and 3 weeks in Experiment 2 following induction of venous hypertension in model III (n = 5 at each time point and n = 5 sham controls); in addition, VEGF expression was immunohistochemically examined in the dura and the brain near the occluded sinus in five model III animals after 1 week.

RESULTS

In Experiment 1, Western blot analysis showed barely detectable bands with molecular weights of 45 kD, corresponding to VEGF, in the sham group, but the highest level of VEGF was induced in model III, followed by models I and II (model III>model I>model II). In Experiment 2, the expression of VEGF peaked 1 week after induction of venous hypertension in model III, decreasing in a linear fashion over 2 and 3 weeks (week 1>weeks 2 and 3). The expression of immunoreactive VEGF was restricted in the connective tissue and the endothelial layer of the dura matter, cerebral cortical tissue and neurons of the basal ganglia.

CONCLUSION

Our results strongly suggest a possible contribution of an angiogenic factor to the growth of DAVF. Venous ischemia by venous hypertension might be a mechanism for inducing up-regulation of angiogenic factor expression.

Genetic considerations relevant to intracranial hemorrhage and brain arteriovenous malformations

Brain arteriovenous malformations (AVMs) cause intracranial hemorrhage (ICH), especially in young adults. Molecular characterization of lesional tissue provides evidence for involvement of both angiogenic and inflammatory pathways, but the pathogenesis remains obscure and medical therapy is lacking. Abnormal expression patterns have been observed for proteins related to angiogenesis (e.g., vascular endothelial growth factor, angiopoietin-2, matrix metalloproteinase-9), and inflammation (e.g., interleukin-6 [IL-6] and myeloperoxidase). Macrophage and neutrophil invasion have also been observed in the absence of prior ICH. Candidate gene association studies have identified a number of germline variants associated with clinical ICH course and AVM susceptibility. A single nucleotide polymorphism (SNP) in activin receptor-like kinase-1 (ALK-1) is associated with AVM susceptibility, and SNPs in IL-6, tumor necrosis factor-alpha (TNF-alpha), and apolipoprotein-E (APOE) are associated with AVM rupture. These observations suggest that even without a complete understanding of the determinants of AVM development, the recent discoveries of downstream derangements in vascular function and integrity may offer potential targets for therapy development. Further, biomarkers can now be established for assessing ICH risk. These data will generate hypotheses that can be tested mechanistically in model systems, including surrogate phenotypes, such as vascular dysplasia and/or models recapitulating the clinical syndrome of recurrent spontaneous ICH.

Development of a cerebral microvascular dysplasia model in rodents

Normal vasculature development of the central nervous system is extremely important because patients with vascular malformations are at life-threatening risk for intracranial hemorrhage or cerebral ischemia. The etiology and pathogenesis of abnormal vasculature development in the central nervous system are unknown, and progress is hampered by the lack of animal models for human cerebrovascular diseases. Here, we report our current study on cerebral microvascular dysplasia (CMVD) development. Using vascular endothelial growth factor hyper-stimulation, we demonstrated that aberrant microvessels could be developed in the rodent brain under certain conditions (such as genetic deficient background, local cytokine and chemokine release, or exogenous vessel dilating stimulation) that may speed up focal angiogenesis and lead to cerebral vascular dysplasia.

Resolution of an anterior-inferior cerebellar artery feeding aneurysm with the treatment of a transverse-sigmoid dural arteriovenous fistula

A 27-year-old man developed an unruptured anterior-inferior cerebellar artery (AICA) feeding aneurysm from a transverse-sigmoid dural arteriovenous malformation. The patient, with a known history of left transverse and sigmoid sinus thrombosis, presented with pulse-synchronous tinnitus. Angiography revealed an extensive dural arteriovenous fistula (AVF), with feeders from both the extracranial and intracranial circulations, involving the right transverse sinus, the torcula, and the left transverse/sigmoid sinuses. Multimodal endovascular and open surgical therapy was used to manage the lesion. Before a planned second-stage treatment for the left sigmoid sinus component, the dural AVF improved significantly. During this interval, however, a small flow-related aneurysm developed on the left AICA feeding the petrous dural region. The aneurysm resolved after resection of the involved sigmoid sinus. This is the first reported case of an unruptured feeding-artery aneurysm in an intracranial dural AVF that resolved spontaneously with treatment of the dural AVF. Until more is known about the natural history, the decisions of when and whether to treat an unruptured dural AVF feeding-artery aneurysm must be made on an individual basis.

Histologic study of arteriovenous shunts in the normal dura mater adjacent to the transverse sinus

BACKGROUND

Although AV shunts are known to exist in the normal dura mater, their histologic appearance has not been examined in detail. Arteriovenous shunts in the normal dura mater adjacent to the transverse sinus, the most frequent site of DAVFs, were studied histologically.

METHODS

Normal dura mater adjacent to the transverse sinus was obtained from 8 cadavers. Each specimen was cut into approximately 4-microm-thick serial sections; these were stained by the elastic Masson method and examined under a light microscope.

RESULTS

Of the 8 specimens, 5 harbored a total of 6 AV shunts; no shunts were found in the other 3 specimens. The shunts, located in the supratentorial (n = 1) and infratentorial dura mater (n = 4) and in the tentorium cerebelli (n = 1), were classified into 2 types. In direct-type shunts, the artery connected directly to the vein; the diameter of these shunts ranged from 40 to 80 microm. In indirect-type shunts, the artery and vein were parallel and were indirectly connected by a shunt vessel, producing an H shape. The diameter of these shunt vessels ranged from 30 to 45 microm. All 6 shunts were connected to veins or the venous lake; none connected directly to the transverse sinus.

CONCLUSIONS

The existence of direct- and indirect-type AV shunts in the normal dura mater was confirmed histologically. Both types exhibited the histologic features of DAVFs, suggesting that AV shunts in the normal dura mater might be involved in the etiology of DAVFs.

The relationship between venous hypertension and expression of vascular endothelial growth factor: hemodynamic and immunohistochemical examinations in a rat venous hypertension model

BACKGROUND

Venous hypertension is regarded as an important factor in the pathogenesis of dural arteriovenous fistula (DAVF). We investigate histologic reaction of dural sinus under the condition of venous hypertension using a rat venous hypertension model to present hemodynamic and immunohistochemical effect in the development of DAVF.

METHODS

Twenty-four Sprague-Dawley male rats were divided into venous hypertension and control groups. Venous hypertension was induced with a left common carotid artery-external jugular vein anastomosis and an occlusion of a right posterior facial vein. Measurements of systemic mean arterial pressure, draining vein pressure (DVP), and cerebral perfusion pressure (CPP) were conducted on the next day, at 7 days, and at 28 days after surgery, and the rats were killed for histologic examinations.

RESULTS

Postoperative DVP increased significantly in venous hypertension group compared to control group (35 +/- 5 vs 13 +/- 2 mm Hg, P < .05). Increased DVP remained above 30 mm Hg throughout the observation period. Postoperative CPP decreased significantly in venous hypertension group compared to control group (49 +/- 8 vs 86 +/- 9 mm Hg, P < .05). In venous hypertension group, there was a significant difference between days 1 and 28 (49 +/- 8 vs 64 +/- 8 mm Hg, P < .05). Histologic examination revealed thickening of connective tissues, proliferation of fibroblasts, and strong expression of vascular endothelial growth factor (VEGF) in endothelium under venous hypertension condition. Immunostained VEGF cells decreased significantly from day 7 to day 28 (100 +/- 16 vs 72 +/- 19 cells, P < .05). A positive correlation was observed between DVP and VEGF expression (Pearson correlation coefficient; r = 0.671, P = .0017). There was a negative correlation between CPP and immunostained VEGF cells (r = -0.702, P = .0089).

CONCLUSIONS

These results suggest that venous hypertension is associated with increased expression of VEGF, and a decreased CPP may have a potential effect in VEGF expression under venous hypertension condition. These factors are speculated to play an important role in progression of DAVF.