Arteriovenous Malformations Feeders Research Articles

Hemodynamic and Anatomical Factors in Arteriovenous Malformation Clinical Presentation: 45 Case Studies.

Hemodynamic factors have been implicated in hemorrhage from cerebral arteriovenous malformations (AVMs). The goal of this endovascular study is to analyze the hemodynamic variability in AVM feeders in a balanced group of ruptured and unruptured AVMs of various sizes and at both superficial and deep locations. We monitored feeder artery pressure (FP) using microcatheters in 45 patients with AVMs (16 with hemorrhage, 29 without) during superselective angiography and AVM embolization. Mean FP was 49 mm Hg. Significant determinants of FP were the systemic pressure (p < 0.001), AVM size (p = 0.03), and the distance of the microcatheter tip from the Circle of Willis (p = 0.06), but not the presence of hemorrhage, patient age, or feeder artery diameter. The FP in ruptured AVMs was 7 mm Hg higher than in unruptured ones (53.8 mm Hg vs. 47.1 mm Hg, p = 0.032). The presence or absence of venous outflow stenosis and the position of the AVM nidus (superficial or deep to the cortical surface) were important anatomical predictors of AVM presentation. The pressure in the feeding artery supplying an AVM is the result of factors which include the systemic arterial pressure, the size of the AVM nidus, and the distance of the AVM from the Circle of Willis. The correlation between these variables makes it difficult to study the risk of hemorrhage as a function of a single factor, which may account for the variation in the conclusions of previous studies.

신경혈관 중재술에서의 신경계감시의 역할: 척추 동정맥 기형의 증례

Endovascular embolization is one of the treatment options for spinal arteriovenous malformation (AVM). Intraoperative neurophysiological monitoring (IONM) is widely used in procedures where post-procedure neurological deterioration may occur. 24-year-old man, previously diagnosed with spinal AVM, visited a tertiary hospital complaining of weakness and tingling sensation on both lower extremities. After confirming the right 6th thoracic segmental artery as the target point of the AVM feeder, an endovascular procedure was performed with IONM. During embolization using a nonadhesive liquid embolic agent (Onyx^®), the amplitude of motor evoked potentials of the bilateral tibialis anterior and right abductor hallucis brevis were decreased over the alarm criteria. After the procedure, the patient developed weakness in both legs, hypoesthesia, and neurogenic bladder. After 4 weeks of rehabilitation, motor and bladder function partially improved. This case presentation is to emphasize the role of the continuous multimodality IONM in making important decisions during neuroendovascular procedures.

Embolization of a Complex Facial Arteriovenous Malformation, Balloon-Assisted Flow Arrest, and Controlled n-BCA Injection with Dextrose Push Technique: 2-Dimensional Operative Video.

N-butyl cyanoacrylate glue (n-BCA, Cerenovus, Irvine, California) is commonly used to treat arteriovenous malformation (AVM). Even though Onyx (ethylene vinyl alcohol, Medtronic, Dublin, Ireland) presents more controlled injection, n-BCA is colorless, thus preferable for treatment of superficial facial malformations. N-BCA injection into AVM can result in premature distal migration or early precipitation and reflux into the feeder vessels. Here we describe a trans-arterial balloon assisted technique embolization of a complex facial AVM with n-BCA. A 22-yr-old female with chronic oral/gum bleeding presented with a complex facial AVM. She underwent selective transarterial n-BCA balloon assisted treatment with dextrose push. Informed written consent was obtained. A Scepter dual lumen balloon (MicroVention, Aliso Viejo, California) and a Prowler microcatheter (Cerenovus) were introduced via a 6-French Envoy guide catheter (Cerenovus) selectively into the AVM feeder. The balloon was positioned 3 cm proximal to the Prowler microcatheter tip and fully inflated to create flow arrest. Diluted 25% concentration of n-BCA in Ethiodol Oil was injected through the Prowler microcatheter. The distal migration of the n-BCA was modulated with simultaneous injection of Dextrose 5% in water via the Scepter balloon. This resulted in a controlled glue injection without early distal glue migration (because of the flow arrest) nor early proximal glue precipitation or reflux (because of the dextrose infusion), obtaining complete cure of the complex facial AVM. Glue embolization with flow arrest and dextrose push allows well controlled injection, and it represents a valid option also for high flow vascular lesions.

Clinical Experience with Intraoperative Ultrasonographic Image in Microsurgical Resection of Cerebral Arteriovenous Malformations

Intraoperative ultrasonography is widely used in neurosurgery for the management of intracerebral hematoma and brain tumor. However, the clinical value of this method in the surgery of cerebral arteriovenous malformations (AVMs) has not been reported. In this study, the application of intraoperative ultrasonography for AVM surgery was evaluated prospectively. This prospective clinical study comprised 41 patients who underwent microsurgical resection of cerebral AVMs at our institute. After routine craniotomy, ultrasonographic imaging with color Doppler ultrasonography and real-time contrast-enhanced ultrasonographic angiography if necessary were applied as navigated images on the monitor during the operation. Ultrasonographic imaging made it easier to understand the vascular architecture during the operation. Color Doppler flow imaging clearly delineated the shape and margin of the AVMs. Intraoperative real-time contrast-enhanced ultrasonographic angiography enabled the surgeons to categorically identify AVM feeders both on the surface and deep in the tissue. Microneurosurgery with intraoperative ultrasonographic image guidance was a safe, effective, and reliable method for identifying the afferent and efferent vessels and for confirming the complete resection of AVMs. These benefits of image-guided microsurgery were mostly apparent for deep-seated AVMs that were not visible on the surface of the brain.

Clinical experience with navigated 3D ultrasound angiography (power Doppler) in microsurgical treatment of brain arteriovenous malformations.

IntroductionWe have previously described a method that has the potential to improve surgery of arteriovenous malformations (AVMs). In the present paper, we present our clinical results.Materials and methodsOf 78 patients referred for AVMs to our University Hospital from our geographical catchment region from 2005 through 2013, 31 patients were operated on with microsurgical technique. 3D MR angiography (MRA) with neuronavigation was used for planning. Navigated 3D ultrasound angiography (USA) was used to identify and clip feeders in the initial phase of the operation. None of our patients was embolized preoperatively as part of the surgical procedure. The niduses were extirpated based on the 3D USA. After extirpation, controls were done with 3D USA to verify that the AVMs were completely removed. The Spetzler three-tier classification of the patients was: A: 21, B: 6, C: 4.ResultsSixty-eight feeders were identified on preoperative MRA and DSA and 67 feeders were identified and clipped by guidance of intraoperative 3D USA. Six feeders identified preoperatively were missed by 3D USA, while five preoperatively unknown feeders were found and clipped. The overall average bleeding was 440 ml. There was a significant reduction in average bleeding in the last 15 operations compared to the first 16 (340 vs. 559 ml, p = 0.019). We had no serious morbidity (GOS 3 or less). New deficits due to surgery were two patients with quadrantanopia (one class B and one class C), the latter (C) also acquired epilepsy. One patient (class A) acquired a hardly noticeable paresis in two fingers. One hundred percent angiographic cure was achieved in all patients, as evaluated by postoperative DSA.ConclusionsNavigated intraoperative 3D USA is a useful tool to identify and clip AVM feeders. Microsurgical extirpation assisted by navigated 3D USA is an effective and safe method for removing AVMs.

Abstract WP435: Changes in Pulsatility and Resistance Indices of Cerebral Arteriovenous Malformation Feeder Arteries After Embolization and Surgery

Introduction: Embolization reduces flow in cerebral arteriovenous malformations (AVMs) before surgical resection, but changes in pulsatility and resistance indices (PI, RI) are unknown. Here, we measure PI, RI in AVM arterial feeders pre- and post-embolization/surgery. Methods: Records of patients who underwent AVM embolization and surgical resection at our institution between 2007-2014 and had PI, RI, and flows obtained using quantitative magnetic resonance angiography were retrospectively reviewed. PI = [(systolic - diastolic flow velocity)/mean flow velocity] and RI = [(systolic - diastolic flow velocity)/systolic flow velocity]. Hemodynamic parameters were compared between the feeder and contralateral artery pre- and post-embolization/surgery. Results: 32 patients with 48 feeder arteries underwent embolization (mean 1.3 sessions). 32 patients with 49 feeder arteries had surgery with/without preoperative embolization. Before any treatment, flow volume rate and mean, systolic, diastolic flow velocities were significantly higher in feeders versus contralateral counterparts ( P &lt;0.001 for each parameter), and PI, RI were significantly lower in feeder compared to contralateral vessels ( P =0.003, P =0.002). After embolization, flow velocities within feeders were significantly higher than in the normal contralateral vessels, but PI, RI did not change significantly (Table). However, after surgery flow velocities within feeders decreased significantly and PI, RI normalized to match the indices of their contralateral counterparts (Table). Conclusions: Following partial AVM embolization, PI, RI are unchanged and flow velocities in feeder arteries increase significantly likely due to redistribution of flow through residual nidus. Complete surgical resection results in normalization of PI, RI and a concomitant decrease in flow velocities. Table: Changes in PI, RI after embolization and surgery.

Anatomy of the feeding arteries of the cerebral arteriovenous malformations.

Identification and anatomic features of the feeding arteries of the arteriovenous malformations (AVMs) is very important due to neurologic, radiologic, and surgical reasons. Seventy-seven patients with AVMs were examined by using a digital subtraction angiographic (DSA) and computerised tomographic (CT) examination, including three-dimensional reconstruction of the brain vessels. In addition, the arteries of 4 human brain stems and 8 cerebral hemispheres were microdissected. The anatomic examination showed a sporadic hypoplasia, hyperplasia, early bifurcation and duplication of certain cerebral arteries. The perforating arteries varied from 1 to 8 in number. The features of the leptomeningeal and choroidal vessels were presented. The radiologic examination revealed singular (22.08%), double (32.48%) or multiple primary feeding arteries (45.45%), which were dilated and elongated in 58.44% of the patients. The feeders most often originated from the middle cerebral artery (MCA; (23.38%), less frequently from the anterior cerebral artery (ACA; 12.99%), and the posterior cerebral artery (PCA; 10.39%). Multiple feeders commonly originated from the ACA and MCA (11.69%), the MCA and PCA (10.39%), the ACA and PCA (7.79%), and the ACA, MCA and PCA (5.19%). The infratentorial feeders were found in 9.1% of the AVMs. Contribution from the middle meningeal and occipital arteries was seen in 3.9% angiograms. Two cerebral arteries had a saccular aneurysm. The AVM haemorrhage appeared in 63.6% of patients. The knowledge of the origin and anatomic features of the AVMs feeders is important in the explanation of neurologic signs, and in a decision regarding the endovascular embolisation, neurosurgical and radiosurgical treatments.

E-097 hemodynamic characteristics of cerebral arteriovenous malformation feeder vessels with and without aneurysms

Introduction/purpose The pathogenesis of aneurysms associated with cerebral arteriovenous malformation (AVM) feeder vessels is poorly understood. We sought to determine the hemodynamic characteristics of AVM feeder vessels with and without aneurysms. Materials and methods Patients with AVMs associated with feeder aneurysms who had flow, vessel diameter, and wall shear stress (WSS) measured before treatment using quantitative magnetic resonance angiography were retrospectively reviewed. Feeders within each AVM were classified into two groups based on presence or absence of aneurysms. Hemodynamic parameters were calculated for each arterial feeder and then compared between the two groups using the independent 2-tailed Student’s t test. Results 11 patients had AVMs with feeder aneurysms. Cohort characteristics are summarized in Table 1. Of 35 total feeder arteries, 12 had an aneurysm and 23 feeders did not have any aneurysms. Absolute mean flow was higher (500.5 vs. 438.4 mL/min, P = 0 .59) and vessel diameter was lower (3.9 vs. 4.8 mm, P = 0 .22) in feeders with aneurysms but not significantly. However, WSS (95.7 vs. 28.0 dynes/cm 2 , P = 0 .04) was significantly higher in feeders with aneurysms. Exponential regression analysis demonstrated that higher flows were significantly associated with larger vessel diameter in AVM feeders with (R 2 = 0.52, P = 0 .01) and without aneurysms (R 2 = 0.46, P = 0 .001). Importantly, at most flow rates feeders with aneurysms had smaller diameters and subsequently higher WSS than feeders without aneurysms (Figure 1). Conclusion WSS is significantly higher among cerebral AVM feeders harboring aneurysms. Despite similarly high flows, feeder artery diameter tended to be smaller if an aneurysm was present, suggesting that AVM feeders with aneurysms are a subgroup in which vessel remodeling cannot compensate for increased blood flow. Disclosures S. Shakur: None. S. Amin-Hanjani: None. H. Mostafa: None. F. Charbel: None. A. Alaraj: None.

Hemodynamic Characteristics of Cerebral Arteriovenous Malformation Feeder Vessels With and Without Aneurysms

The pathogenesis of aneurysms associated with cerebral arteriovenous malformation (AVM) feeder vessels is poorly understood. We sought to determine the hemodynamic characteristics of AVM feeder vessels with and without aneurysms. Patients with AVMs associated with feeder aneurysms who had flow, vessel diameter, and wall shear stress measured before treatment using quantitative magnetic resonance angiography were retrospectively reviewed. Feeders within each AVM were classified into 2 groups based on presence or absence of aneurysms. Hemodynamic parameters were calculated for each arterial feeder and then compared between the 2 groups. Eleven patients had AVMs with feeder aneurysms. Of 35 total feeder arteries, 12 had an aneurysm and 23 feeders did not have any aneurysms. Absolute mean flow was higher (510.2 versus 438.4 mL/min; P=0.53) and vessel diameter was lower (4.0 versus 4.8 mm; P=0.24) in feeders with aneurysms but not significantly. However, wall shear stress (96.2 versus 28.0 dynes/cm2; P=0.04) was significantly higher in feeders with aneurysms. Wall shear stress is significantly higher among cerebral AVM feeders harboring aneurysms. Despite similarly high flows, feeder artery diameter tended to be smaller if an aneurysm was present, suggesting that AVM feeders with aneurysms are a subgroup in which vessel remodeling cannot compensate for increased blood flow.

Multimodal angiographic assessment of cerebral arteriovenous malformations: a pilot study

PurposeWe describe our protocol of three-dimensional (3D) Roadmap intracranial navigation and image fusion for analysis of the angioarchitecture and endovascular treatment of brain arteriovenous malformations (AVMs).MethodsWe performed superselective catheterization of...

脳動静脈奇形のhigh flow feederに対する安全で効果的な術前塞栓術

Endovascular closure of high-flow arteriovenous (AV) shunts in intracranial AV malformations (AVMs) is technically challenging. When using liquid embolic agents, the high flow through the shunt may cause migration of the embolic agent to the venous outflow tract, with potentially devastating consequences. ED coils (Kaneka Medix Co., Osaka, Japan) are useful for preoperative embolization of high-flow feeders of AVMs via transarterial routes before n-butyl cyanoacrylate (NBCA) injection. Detachable coils may be inserted at the fistula site to decrease flow and may provide an anchoring point for NBCA injection. ED coils are compatible with the one-marker MarathonTM Flow Directed Micro Catheter (Irvine CA, Covidien) given that the detachment point between the coil and delivery wire is detected electrically and the delivery wire tip is flexible enough to navigate coils through long tortuous vessels. Here, we report the role of endovascular treatment with ED coils in the management of intra-cranial high flow AVMs.

Transcranial color-coded Doppler assessment of cerebral arteriovenous malformation hemodynamics in patients treated surgically or with staged embolization

ObjectiveThe etiology of hemodynamic disturbances following embolization or surgical resection of arteriovenous malformations (AVMs) has not been fully explained. The aim of the study was the assessment of the selected hemodynamic parameters in patients treated for cerebral AVMs using transcranial color-coded Doppler sonography (TCCS). Materials and methodsForty-six adult patients (28 males, 18 females, aged 41±13 years, mean±SD) diagnosed with AVMs who were consecutively admitted to the Department of Neurosurgery between 2000 and 2012 treated surgically or with staged embolization were enrolled in the study. All patients were examined with TCCS assessing mean flow velocity (Vm), the pulsatility index (PI) and vasomotor reactivity (VMR) in all main intracranial arteries. The examined parameters were assessed in the vessel groups (feeding, ipsilateral and contralateral to the AVM) and they were compared between the examinations, i.e. at admission, within 24h after the first embolization or surgical resection (I control), and before the second embolization (II control). ResultsIn feeders which were completely obliterated or surgically resected – I control examination showed a nonsignificant Vm decrease. The difference between Vm before embolization and II control examination was significant (102.0±47.8cm/s vs 54.3±19.4cm/s, p<0.01). A significant increase in PI (0.72±0.18 vs 0.94±0.24, p<0.01) and VMR (1.80±0.59 vs 2.78±0.78, p<0.01) of feeding vessels was observed in I control. No further increase in PI or in VMR was observed. In embolized feeding vessels after partial AVM embolization I control examination showed a significant decrease in Vm (116.1±32.6cm/s vs 93.4±33.0cm/s, p<0.01). No further significant decrease in Vm was noted. The pulsatility index increased significantly (I control, 0.54±0.11 vs 0.66±0.15, p<0.01) and then decreased nonsignificantly (II control). No statistically significant differences were found in VMR values between pretreatment, I and II control examinations. Both Vm in the ipsilateral internal carotid artery and the ratio of Vm of the embolized vessel to Vm of the corresponding contralateral vessel were significantly higher in I control examination compared to II control examination (111.8±44.0cm/s vs 101.3±40.6cm/s, p<0.01; 1.63±0.61 vs 1.37±0.62, p<0.01; respectively). No statistically significant correlation was observed between the decrease in Vm or the increase in PI in the embolized vessels and the reduction of AVM volume. In the nonembolized feeding vessels after partial AVM embolization II control examination revealed the increase in Vm and a significant decrease in PI (0.71±0.21 vs 0.62±0.16, p<0.01) compared to I examination. No statistically significant changes in the VMR value in the nonembolized feeders between the pretreatment, I and II control examinations were noted. ConclusionsThe decrease in Vm and the increase in the PI in the embolized feeding vessels after the first complete embolization or surgical resection is observed, whereas the PI returned to normal values before Vm does. The observed decrease in Vm and an increase in the PI in embolized AVM feeders after complete or partial embolization do not correlate with the extent of embolization. In these vessels a relative increase in blood flow velocity is maintained within the first 24h following embolization as compared to contralateral vessels. The increase in Vm is not related to disturbances in VMR. Blood redistribution to the nonembolized AVM feeders is observed after partial AVM embolization.

P-026 Comparative 4D Flow MR Imaging in Quantification of Vascular Haemodynamics in Different Types of Intra-cranial Arteriovenous Malformations

Background and PurposeHaemodynamic characterisation of arteriovenous malformations (AVMs) may have implications for risk stratification. Gross visualisation and quantification of intracranial AVM flow dynamics have been investigated using various methods including...

Abstract TP446: Noninvasive Evaluation of Cerebral Arteriovenous Malformations by 4D-CT Angiography using 320-detector row CT

Background and Purpose: Patients with higher Spetzler-Martin grade cerebral arteriovenous malformations (AVMs) are associated with poorer neurologic and clinical outcomes. Four dimensional computed tomography angiography (4D-CTA) is newly and promising technique in the diagnosis of patients with cerebral arteriovenous malformations (AVMs). The purpose of this retrospective study was to investigate the utility of 4D-CTA using whole-brain 320- detector row CT for assessing cerebral AVMs compared with conventional angiography (CA). Materials &amp; Methods: Participants comprised patients admitted to our institution from November 2010 to March 2012 due to cerebral AVMs, who underwent both 4D-CTA and CA within 14days. The diagnosis of AVM was finally confirmed by CA. Two readers reviewed 4D-CTA and CA under consensus regarding detection rate of the AVMs, each component of the AVMs (feeders, nidi, drainers) which was scored using four-point grading scale (excellent=3, good=2, fair=1, poor=0), and the Spetzler-Martin (S-M) grade. Results: During study periods, eleven patients met our criteria. In every case, cerebral AVM was diagnosed by 4D-CTA. The average score for feeders, nidi, and drainers was 2.0, 2.3, and 2.5 in 4D-CTA and 2.4, 2.6, and 2.7 in CA, respectively. The average score of S-M grade was both 2.0, and matched in 11/11 patients. There were no significant differences statistically between two modalities (P&lt;.005). Conclusion: 4D-CTA using 320-detector row CT is a very reliable method and offered diagnostic performance equivalent to CA in detecting and predicting S-M classification of cerebral AVMs.

Abstract 177: Hemodynamics and Anatomic Evaluation of Intracranial Arteriovenous Malformations Using Phase-Contrast Magnetic Resonance Velocimetry

Introduction: Arteriovenous Malformations (AVMs) have a high lifetime risk of hemorrhage; however treatment carries a significant risk of morbidity/mortality. Wall Shear Stress (WSS) and other hemodynamic parameters are shown to be altered in patients with symptomatic AVMs. Analysis of hemodynamics may have value in stratifying patients into different risk groups to prioritize treatment. We have recently implemented PC-VIPR, a phase contrast MRA technique that can acquire whole brain angiograms with scan time of 5 minutes with velocity data. PC-VIPR has sufficient spatial resolution for both hemodynamic analysis and assessment of anatomic features such as Spetzler-Martin grading. Materials &amp; Methods: 10 patients with AVMs were scanned using PC-VIPR; WSS and vessel diameter in vessels feeding the AVMs and in normal contralateral vessels were calculated using PC-VIPR velocity data using automated B-spline interpolation. Spetzler-Martin grading was performed by an experienced neuroradiologist. Results: Patients with an asymptomatic presentation or mild symptoms (n=4) had no significant difference in WSS between ipsilateral feeding vessels and normal contralateral vessels (1.555 N/m2 vs 1.494, p=0.31), and showed significant vessel dilation in feeding vessels when compared to normal contralateral vessels (4.57 mm vs 3.66, p=0.005) while patients presenting with hemorrhage, severe headaches/seizures, or focal neurologic deficits (n=6) had significantly higher WSS in feeders compared to contralateral vessels (1.607 N/m2 vs 1.146, p=0.003) but the increase in vessel dilation was not statistically significant. (4.34 vs 3.84, p=0.11) Spetzler-Martin grading was performed in all patients and correlated with grading performed via digital subtraction angiography in all cases. Discussion: In this study we demonstrate that both hemodynamic analysis and Spetzler-Martin grading can be obtained non-invasively in patients with AVMs using PC-VIPR. Variation in WSS between feeders and normal vessels appeared to relate to the clinical presentation of the patient. Figure 1a shows a WSS map of a patient with mild stable symptoms demonstrating similar WSS in feeders compared to contralateral vessels, Figure 1b shows a WSS map of a patient presenting with hemorrhage with higher WSS in feeders compared to contralateral vessels. Several reports suggest high WSS in AVM feeders stimulates compensatory dilation, normalizing WSS. Hemodynamic analysis using PC-VIPR may have value in risk stratification by identifying patients in which compensation has not yet occurred, with increased risk of hemorrhage.

Gene Expression Microarray Studies of Intracranial Aneurysm Walls Lead to Similar Results

To the Editor: We congratulate the authors Shi et al for their recent study of comparing 3 ruptured and 3 unruptured aneurysm walls with paired tissue of the superficial temporal artery.1 Back in May 2008 we published our gene expression micorarray study results of 4 unruptured and 6 ruptured aneurysms, as well as 4 arteriovenous malformation feeders which were obtained in a similar way.2 We used the same pathway analysis program “Ingenuity …

OPERATION OF ARTERIOVENOUS MALFORMATIONS ASSISTED BY STEREOSCOPIC NAVIGATION-CONTROLLED DISPLAY OF PREOPERATIVE MAGNETIC RESONANCE ANGIOGRAPHY AND INTRAOPERATIVE ULTRASOUND ANGIOGRAPHY

To study the application of navigated stereoscopic display of preoperative three-dimensional (3-D) magnetic resonance angiography and intraoperative 3-D ultrasound angiography in a clinical setting. Preoperative magnetic resonance angiography and intraoperative ultrasound angiography are presented as stereoscopic images on the monitor during the operation by a simple red/blue technique. Two projections are generated, one for each eye, according to a simple ray casting method. Because of integration with a navigation system, it is possible to identify vessels with a pointer. The system has been applied during operations on nine patients with arteriovenous malformations (AVMs). Seven of the patients had AVMs in an eloquent area. The technology makes it easier to understand the vascular architecture during the operation, and it offers a possibility to identify and clip AVM feeders both on the surface and deep in the tissue at the beginning of the operation. All 28 feeders identified on the preoperative angiograms were identified by intraoperative navigated stereoscopy. Twenty-five were clipped at the beginning of the operation. The other three were clipped at a later phase of the operation. 3-D ultrasound angiography was useful to map the size of the nidus, to detect the degree of brain shift, and to identify residual AVM. Stereoscopic visualization enhances the surgeon's perception of the vascular architecture, and integrated with navigation technology, this offers a reliable system for identification and clipping of AVM feeders in the initial phase of the operation.

Intravascular pressure measurements in feeding pedicles of brain arteriovenous malformations

Pressure measurements in arterial feeders of arteriovenous malformations (AVMs) can be easily acquired during endovascular treatment procedures. In this study, mean arterial pressure values in arterial feeders (Pfed) of brain AVMs were determined using a pressure measuring system connected to a standard microcatheter. A total of 148 measurements were performed in 139 patients. Mean systemic arterial pressure values were subtracted for correction. The levels of correlation between the pressure values and various clinical parameters (i.e., AVM location, size, previous hemorrhage) and pathoanatomical features of the AVM (e.g., nidus structure, number of draining veins) were determined. Pfed values were 54.5 mmHg on average. Pfed was lower in more distally located AVMs, in larger lesions and in AVMs with multiple drainage veins. Pressure values were significantly higher in patients with previous hemorrhage and in smaller AVMs. Our results support the importance of hemodynamic parameters in determining the presentation of AVMs. More extensive studies using this simple technique may further elucidate these mechanisms and may result in improved criteria for patient selection and reduction of complications.

Operation of Arteriovenous Malformations Assisted by Stereoscopic Navigation-controlled Display of Preoperative Magnetic Resonance Angiography and Intraoperative Ultrasound Angiography

To study the application of navigated stereoscopic display of preoperative three-dimensional (3-D) magnetic resonance angiography and intraoperative 3-D ultrasound angiography in a clinical setting. Preoperative magnetic resonance angiography and intraoperative ultrasound angiography are presented as stereoscopic images on the monitor during the operation by a simple red/blue technique. Two projections are generated, one for each eye, according to a simple ray casting method. Because of integration with a navigation system, it is possible to identify vessels with a pointer. The system has been applied during operations on nine patients with arteriovenous malformations (AVMs). Seven of the patients had AVMs in an eloquent area. The technology makes it easier to understand the vascular architecture during the operation, and it offers a possibility to identify and clip AVM feeders both on the surface and deep in the tissue at the beginning of the operation. All 28 feeders identified on the preoperative angiograms were identified by intraoperative navigated stereoscopy. Twenty-five were clipped at the beginning of the operation. The other three were clipped at a later phase of the operation. 3-D ultrasound angiography was useful to map the size of the nidus, to detect the degree of brain shift, and to identify residual AVM. Stereoscopic visualization enhances the surgeon's perception of the vascular architecture, and integrated with navigation technology, this offers a reliable system for identification and clipping of AVM feeders in the initial phase of the operation.

Ventricular/paraventricular small arteriovenous malformations: role of embolisation with cyanoacrylate

Arteriovenous malformations (AVMs) located in or near to ventricles have proven difficult to treat. We report the safety and efficacy of embolisation of these deep central lesions and describe the contribution of embolisation to multimodality treatment. Fourteen consecutive patients with small (less than 3 cm) ventricular/paraventricular AVMs arranged for possible embolisation to their nidi. All patients presented with intracranial haemorrhage. The AVMs ranged in size from 10 to 30 mm (average, 17 mm). Embolisations were performed using liquid adhesive (cyanoacrylate and iodised oil mixture at a ratio of less than 1:4) delivered by flow-guided microcatheters with the patient under general anaesthesia. One patient (7.1%) was considered unsuitable for embolisation, and another (7.1%) was not able to undergo embolisation because of the morphological features of the AVM feeders, while the remaining 12 could be embolised successfully. Six of 12 patients who underwent embolisation achieved complete occlusion of their AVMs (overall occlusion rate, 42.9%), while the remaining 6 were embolised partially with a 60-95% (mean = 80%) size reduction. One (8%) permanent neurological deficit resulted from embolisation. Endovascular therapy seems to make a significant contribution to the multimodality treatment of small AVMs located in the ventricle or paraventricular deep area. Embolisation alone permits complete cure in a large number of patients. It results in obliteration of a significant volume of the nidus in most of the remaining patients, which makes those nidi more vulnerable to subsequent multimodal therapy.