Occlusive hyperemia: a theory for the hemodynamic complications following resection of intracerebral arteriovenous malformations

Comparative analysis of peri-nidal cerebral blood flow and metabolism using a novel quantitative 15O-PET method in patients with arteriovenous malformations

To effectively treat cerebral arteriovenous malformations (AVMs), peri-nidal flow regulation and metabolic status must be understood. In this study, we used 15O-oxygen positron emission tomography (PET) post-processing analysis to investigate vascular radioactivity in the nidal region of AVMs. Single-dynamic PET imaging was performed on seven unruptured AVM patients during the sequential inhalation of 15O2 and C15O2. A previously validated dual-tracer basis function method (DBFM) was employed to calculate parametric images. The results of our study were as follows. First, in remote and contralateral AVM regions, DBFM and a previous approach of dual-tracer autoradiography (DARG) showed strong positive correlations in cerebral blood flow (CBF), cerebral oxygen metabolism rate (CMRO2), and oxygen extraction fraction. Second, peri-nidal CBF and CMRO2 correlation was lower, and overestimation occurred with DARG compared to with DBFM. Third, on comparing DBFM to quantitative 123I-iodoamphetamine single-photon emission computed tomography (SPECT), CBF correlated significantly. In contrast, the correlation between DARG and quantitative 123I-iodoamphetamine-SPECT was weaker in the peri-nidal regions. Fourth, analysis of tissue time-activity curves demonstrated good reproducibility using the novel formulation in the control, peri-nidus, and core nidal regions, indicating the adequacy of this approach. Overall, the DBFM approach holds promise for assessing haemodynamic alterations in patients with AVMs.

Perioperative stroke

Ischaemic or haemorrhagic perioperative stroke (that is, stroke occurring during or within 30 days following surgery) can be a devastating complication following surgery. Incidence is reported in the 0.1-0.7% range in adults undergoing non-cardiac and non-neurological surgery, in the 1-5% range in patients undergoing cardiac surgery and in the 1-10% range following neurological surgery. However, higher rates have been reported when patients are actively assessed and in high-risk populations. Prognosis is significantly worse than stroke occurring in the community, with double the 30-day mortality, greater disability and diminished quality of life among survivors. Considering the annual volume of surgeries performed worldwide, perioperative stroke represents a substantial burden. Despite notable differences in aetiology, patient populations and clinical settings, existing clinical recommendations for perioperative stroke are extrapolated mainly from stroke in the community. Perioperative in-hospital stroke is unique with respect to the stroke occurring in other settings, and it is essential to apply evidence from other settings with caution and to identify existing knowledge gaps in order to effectively guide patient care and future research.

Treatment of Brain Arteriovenous Malformations

Brain arteriovenous malformations (AVMs) are a rare entity of vascular anomalies, characteristic of anatomical shunting where arterial blood directly flows into the venous circulation. The main aim of the active treatment policy of brain AVMs is the prevention of haemorrhage. There are well-established treatment strategies that continually improve in their safety and efficacy, primarily due to the advances in imaging modalities, targeted and novel techniques, the development of alternative treatment approaches, and even better experience with the disease itself. There are interesting imaging novelties that may be prospectively applicable in the decision-making and planning of the most effective treatment approach for individual patients with intracranial AVM. Surgery is often considered the first-line treatment; however, each patient should be evaluated individually, and the risks of the active treatment policy should not overcome the benefits of the spontaneous natural history of the disease. All treatment modalities, i.e., surgery, radiosurgery, endovascular embolization, and observation, are justified but need to be meticulously selected for each individual patient in order to deliver the best treatment outcome. This chapter deals with historical and currently applied dogmas, followed by introductions of advances in each available treatment modality of AVM management.

Quantitative Analysis of Parenchymal Effects and Flow of Large Arteriovenous Malformations Managed With Stereotactic Radiosurgery

BACKGROUND AND OBJECTIVES

Stereotactic radiosurgery (SRS) of larger arteriovenous malformations (AVM) is associated with an elevated incidence of adverse radiation effects (ARE). To date, volume-response and dose-response models have been used to predict such effects. To understand radiological outcomes and their hemodynamic effects on the regional brain.

METHODS

A retrospective analysis was conducted at our institution using a prospective registry of patients managed between 2014 and 2020. We included patients with AVM with a nidus larger than 5 cc who received either single-session or volume-staged Gamma Knife radiosurgery. AVM volume changes, volumes of parenchymal response, and obliteration were analyzed and correlated with transit times and diameters of feeding arteries and draining veins.

RESULTS

Sixteen patients underwent single-session SRS, and 9 patients underwent volume-staged SRS. The average AVM volume was 12.6 cc (5.5-23). The AVM locations were predominantly lobar (80%) and 17 (68%) were in critical locations. The mean margin dose was 17.2 Gy (15-21), and the median V12Gy was 25.5 cc. Fourteen (56%) AVMs had a transit time shorter than 1 second. The median vein-artery ratio (sum diameter of the veins/sum diameter of feeding arteries) was 1.63 (range, 0.60-4.19). Asymptomatic parenchymal effects were detected in 13 (52%) patients and were symptomatic in 4 (16%) patients. The median time to ARE was 12 months (95% CI 7.6-16.4). On univariate analysis, significant predictors of ARE were lower vein-artery ratio ( P = .024), longer transit time ( P = .05), higher mean dose ( P = .028), and higher D95 ( P = .036).

CONCLUSION

Transit times and vessel diameters are valuable predictors of the subsequent parenchymal response after SRS. A more quantitative understanding of blood flow is critical for predicting the effects on the regional brain after AVM radiosurgery.

Rupture-related quantitative hemodynamics of the supratentorial arteriovenous malformation nidus

OBJECTIVE

The hemodynamics of a brain arteriovenous malformation (AVM) nidus may be closely related to clinical presentation. The authors of this study aimed to explore the hemorrhagic quantitative hemodynamic indicators of the nidus through quantitative digital subtraction angiography (QDSA).

METHODS

The quantitative hemodynamic parameters were generated from QDSA. Three data sets were used to explore independent quantitative hemodynamic indicators associated with AVM rupture. The training data set was exploited to discover independent quantitative hemodynamic indicators of AVM rupture by performing univariate and multivariate logistic regression analyses. The authors plotted receiver operating characteristic curves to validate the diagnostic performance of the hemorrhagic hemodynamic indicators using the training and two external validation data sets. Kaplan-Meier survival analysis was adopted to verify the predictive power of these risk indicators of future hemorrhage in the external prospective validation data set.

RESULTS

A total of 151 patients were included in this study, 91 in the training set and 30 in each of the two validation sets. A higher stasis index and slower transnidal relative velocity (TRV) of the nidus were significantly correlated with AVM rupture. The areas under the curve (AUCs) of the stasis index (nidus) were 0.765 and 0.815 and those of the TRV (nidus) were 0.735 and 0.796, respectively, in the training and retrospective external validation sets. Kaplan-Meier survival analysis confirmed the validity of the stasis index and TRV in predicting future rupture risk in the prospective validation data set (p = 0.008 and 0.041, respectively, log-rank test).

CONCLUSIONS

A higher stasis index (nidus) and slower TRV (nidus) in QDSA were associated with AVM rupture and were effective indicators of future hemorrhage, suggesting that the core mechanisms underlying AVM rupture could be intravascular blood stasis and occlusive hyperemia of the nidus.

FLAIR hyperintense vessels on MRI post brain arteriovenous malformation embolization: A novel finding associated with post-procedure intraparenchymal hemorrhage

INTRODUCTION

Brain arteriovenous malformations (BAVMs) are frequently managed by endovascular embolization with a growing number of centers embolizing with intent to cure. Hemorrhage post-embolization is a severe and poorly understood complication. We present a novel imaging finding associated with post-embolization hemorrhage that has significantly impacted the management of patients at our institution.

METHODS

A retrospective review of all patients undergoing embolization of BAVM at a single center was performed. Post-embolization magnetic resonance imaging (MRI) was reviewed for the presence of T2 fluid-attenuated inversion recovery (FLAIR) hyperintense vessels (FHVs). Bivariate analysis was performed to determine associations between patient characteristics and risk of hemorrhage.

RESULTS

A total of 50 patients underwent 75 embolization procedures. Forty-six post-embolization MRIs were available for review. There were four hemorrhages and 100% of those presented with FHV. In contrast, only 11.9% of embolization procedures without post-procedural hemorrhage had FHVs on MRI. In total, 18.7% of embolizations led to some morbidity or mortality, with only 6.7% leading to permanent morbidity or mortality. In bivariate analysis, only the presence of FHVs was correlated with the risk of hemorrhage (p < 0.05).

CONCLUSIONS

This is the first series to describe the finding of hyperintense blood vessels on FLAIR imaging after embolization of BAVMs and correlate it with hemorrhage post embolization. This finding can help guide practitioners and potentially identify patients at risk of delayed hemorrhage post embolization.

Pseudo-residual nidus after arteriovenous malformation surgery: illustrative case

BACKGROUND

Intraoperative indocyanine green video angiography (ICG-VA) is useful for determining the extent of lesion removal during cerebral arteriovenous malformation (AVM) surgery. The authors described a case of surgical removal of an AVM presenting with early venous filling mimicking a residual nidus on intraoperative ICG-VA.

OBSERVATIONS

A 7-year-old girl experienced a sudden disturbance of consciousness. Computed tomography revealed right frontal intracerebral hemorrhage. Digital subtraction angiography showed a Spetzler-Martin grade 1 AVM in the right frontal lobe. The patient received surgical removal of the AVM after endovascular embolization. After removal of the nidus, the first intraoperative ICG-VA revealed early venous filling of the cortex around the excision cavity. Additional resection of the cortex around this area was performed. Histopathological examination of the lesion revealed a dilated normal vascular structure without an AVM.

LESSONS

Early venous filling in the surrounding brain tissue after AVM removal does not necessarily indicate a residual nidus. The need for additional resection of the lesion depends on the eloquence of the area.

Intraoperative Monitoring Cerebral Blood Flow During the Treatment of Brain Arteriovenous Malformations in Hybrid Operating Room by Laser Speckle Contrast Imaging

Background

Hemodynamic changes caused by hybrid surgery for brain arteriovenous malformations (bAVM) are usually related to long-term lesions from "blood stealing". There are currently no viable low-cost, noninvasive procedures for assessing cerebral perfusion in the operating room. This study aims to investigate the use of intraoperative laser speckle contrast image (LSCI) software in AVM surgery.

Methods

In Zhongnan Hospital of Wuhan University, 14 patients who underwent surgery with LSCI were collected. To analyze the hemodynamic features of AVM and the influence on the peripheral cortex of AVM embolization and resection, we assessed the transit time between feeding arteries and drainage veins by intraoperative digital subtraction angiography (DSA). Meanwhile, LSCI was performed at pre-embolization, post-embolization, and after complete resection of bAVM.

Results

In this study, the transit time of bAVM before and after embolization was compared, the transit time before embolization was significantly shorter than that after embolization (p < 0.05). We also got good visualization of relative CBF, in addition, to flow imaging in the cortical vasculature round bAVM with LSCI. The flux of post-surgery was significantly higher than pre-embolization (p < 0.01).

Conclusion

Hemodynamic variable assessment plays an important role in the resection of AVM in the hybrid operative room and LSCI can be used to visualize and evaluate cortical cerebral blood flow to detect pathological hyperperfusion in real-time with a good spatial-temporal resolution in a sensitive and continuous, non-invasive mode.

Hemodynamic alterations following a cerebellar arteriovenous malformation resection: Case report and densitometric quantitative analysis from CT imaging

BACKGROUND

Cerebellar arteriovenous malformations (cAVMs) are rare and challenging lesions with an aggressive natural history. The mechanisms whereby a patient can worsen clinically after a supratentorial AVM resection include an acute alteration in cerebral hemodynamics, which is a known cause of postoperative hyperemia, edema and/or hemorrhage. These phenomena has not been described for cAVMS. Moreover, the underlying pathophysiology of edema and hemorrhage after AVM resection still remains controversial.

METHODS

We report a patient that presented an abrupt neurological deterioration after cAVM surgical resection. Emergent external ventricular drainage to treat incipient hydrocephalus only partially reverted the patient's deterioration. Consecutive post-surgery CT images revealed fourth ventricle compression secondary to cerebellar swelling that concurred with a new neurological deterioration. Densitometric analysis was performed in these CT images to reveal the nature of these changes as well as their evolution over time.

RESULTS

Importantly, we demonstrated a dynamic increase in the cerebellum mean density at the interval of Hounsfield values which correspond to hyperemia values. These changes were dynamic, and when hyperemia resolved and cerebellar density returned to basal levels, the fourth ventricle re-expanded and the patient neurologically recovered.

CONCLUSIONS

This study demonstrated the utility of quantitative CT image analysis in the context of hemodynamic alterations following cAVM resection. Densitometric CT analysis demonstrated that hyperemic changes, but not ischemic ones, were time-dependent and were responsible for swelling and hemorrhage that conditioned neurological status and patient's evolution.

Microsurgical Treatment of Deep and Eloquent AVMs

Over the past 30 years, the treatment of deep and eloquent arteriovenous malformations (AVMs) has moved away from microneurosurgical resection and towards medical management and the so-called minimally invasive techniques, such as endovascular embolization and radiosurgery. The Spetzler-Martin grading system (and subsequent modifications) has done much to aid in risk stratification for surgical intervention; however, the system does not predict the risk of hemorrhage nor risk from other interventions. In more recent years, the ARUBA trial has suggested that unruptured AVMs should be medically managed. In our experience, although these eloquent regions of the brain should be discussed with patients in assessing the risks and benefits of intervention, we believe each AVM should be assessed based on the characteristics of the patient and the angio-architecture of the AVM, in particular venous hypertension, which may guide us to treat even high-grade AVMs when we believe we can (and need to) to benefit the patient. Advances in imaging and intraoperative adjuncts have helped us in decision making, preoperative planning, and ensuring good outcomes for our patients. Here, we present several cases to illustrate our primary points that treating low-grade AVMs can be more difficult than treating high-grade ones, mismanagement of deep and eloquent AVMs at the behest of dogma can harm patients, and the treatment of any AVM should be tailored to the individual patient and that patient's lesion.

[Relationship between the features of venous drainage of supratentorial arteriovenous malformations and the risk of intracranial hemorrhage]

BACKGROUND

Intracranial hemorrhage is the most common complication of cerebral arteriovenous malformations (AVM). In recent years, most studies devoted to the features of AVM functioning consider venous drainage as important factor influencing the rupture of malformation.

OBJECTIVE

To review the literature data on the relationship between the features of venous drainage of cerebral arteriovenous malformations and intracranial hemorrhage.

MATERIAL AND METHODS

We found 43 studies discussing the features of AVM venous drainage for the period from 1982 to 2020. Most of reports were published between 2005 and 2020.

RESULTS

Deep venous drainage and a single drainage vein were the most significant factors influencing the risk of hemorrhage. Venous ectasia, reflux, stenosis, number, length and tortuosity of drainage veins were less important for the risk of AVM rupture.

CONCLUSION

Analysis of the features of AVM venous drainage can make it possible to predict the natural course of disease and risk of intracranial hemorrhage. These aspects are essential for neurosurgical treatment.

Three-dimensional whole-brain mapping of cerebral blood volume and venous cerebral blood volume using Fourier transform-based velocity-selective pulse trains

PURPOSE

To develop 3D MRI methods for cerebral blood volume (CBV) and venous cerebral blood volume (vCBV) estimation with whole-brain coverage using Fourier transform-based velocity-selective (FT-VS) pulse trains.

METHODS

For CBV measurement, FT-VS saturation pulse trains were used to suppress static tissue, whereas CSF contamination was corrected voxel-by-voxel using a multi-readout acquisition and a fast CSF T₂ scan. The vCBV mapping was achieved by inserting an arterial-nulling module that included a FT-VS inversion pulse train. Using these methods, CBV and vCBV maps were obtained on 6 healthy volunteers at 3 T.

RESULTS

The mean CBV and vCBV values in gray matter and white matter in different areas of the brain showed high correlation (r = 0.95 and P < .0001). The averaged CBV and vCBV values of the whole brain were 5.4 ± 0.6 mL/100 g and 2.5 ± 0.3 mL/100 g in gray matter, and 2.6 ± 0.5 mL/100 g and 1.5 ± 0.2 mL/100 g in white matter, respectively, comparable to the literature.

CONCLUSION

The feasibility of FT-VS-based CBV and vCBV estimation was demonstrated for 3D acquisition with large spatial coverage.

Hemodynamic alterations following a cerebellar arteriovenous malformation resection: Case report and densitometric quantitative analysis from CT imaging

BACKGROUND

Cerebellar arteriovenous malformations (cAVMs) are rare and challenging lesions with an aggressive natural history. The mechanisms whereby a patient can worsen clinically after a supratentorial AVM resection include an acute alteration in cerebral hemodynamics, which is a known cause of postoperative hyperemia, edema and/or hemorrhage. These phenomena has not been described for cAVMS. Moreover, the underlying pathophysiology of edema and hemorrhage after AVM resection still remains controversial.

METHODS

We report a patient that presented an abrupt neurological deterioration after cAVM surgical resection. Emergent external ventricular drainage to treat incipient hydrocephalus only partially reverted the patient's deterioration. Consecutive post-surgery CT images revealed fourth ventricle compression secondary to cerebellar swelling that concurred with a new neurological deterioration. Densitometric analysis was performed in these CT images to reveal the nature of these changes as well as their evolution over time.

RESULTS

Importantly, we demonstrated a dynamic increase in the cerebellum mean density at the interval of Hounsfield values which correspond to hyperemia values. These changes were dynamic, and when hyperemia resolved and cerebellar density returned to basal levels, the fourth ventricle re-expanded and the patient neurologically recovered.

CONCLUSIONS

This study demonstrated the utility of quantitative CT image analysis in the context of hemodynamic alterations following cAVM resection. Densitometric CT analysis demonstrated that hyperemic changes, but not ischemic ones, were time-dependent and were responsible for swelling and hemorrhage that conditioned neurological status and patient's evolution.

Complications in AVM Surgery

In AVM surgery perioperative complications can arise and can have serious perioperative consequences. Surgically related complications in AVM treatment, in many cases, can be avoided by paying attention to details:1. Careful selection of the patient: - addressing a patient with eloquent AVM to Gamma Knife treatment - preoperative treatment with selective embolization of the accessible deep feeders - preoperative gamma knife or embolize those patient with an over-expressed venous pattern2. Meticulous coagulation of deep medullary feeders: - Using dirty coagulation - Using dry non-stick coagulation - Using micro clips - Using laser - Reaching the choroidal vessel in the ventricle when possible - Avoiding occlusive coagulation with hemostatic agents3. Check and avoiding any residual of the AVM4. Keep the patient under pressure control during postoperative periodFulfilling these steps contributes to reduce complications in this difficult surgery, leading to a safer treatment that compares favorably with natural history of brain arteriovenous malformations.

One-Stage Treatment in a Hybrid Operation Room to Cure Brain Arteriovenous Malformation: A Single-Center Experience

OBJECTIVE

To report the principles and techniques of using a hybrid operation room in the treatment of brain arteriovenous malformation (BAVM).

METHODS

From October 1, 2016 to December 31, 2018, we treated 54 consecutive patients with nonemergent BAVM in a hybrid operation room. The clinical data, radiologic images, and outcomes were collected to establish a prospective database for evaluation.

RESULTS

Thirty-two male and 22 female patients were enrolled with a mean age of 32.6 ± 13.1 years (range, 10-61 years). Bleeding (n = 32, 59.3%) was the main clinical presentation, followed by headache (n = 27, 50.0%), seizures (n = 14, 25.9%), neurofunctional deficits (n = 16, 29.6%), and no symptoms (n = 2, 3.7%). Thirty-one patients (57.4%) accepted resection without intraoperative embolization, 18 (33.3%) were treated with combined embolization and resection, and 5 (9.3%) were cured with intraoperative embolization and resection was cancelled. All patients achieved total BAVM obliteration confirmed with intraoperative angiography. There were no significant differences in outcomes between low-grade (Spetzler-Martin grades I, II, and modified grade III-) and high-grade (Spetzler-Martin grades ≥IV and modified grade III+) groups, except that the high-grade group had more blood loss (667.9 ± 647.5 vs. 284.3 ± 148.6 mL; P = 0.046) and longer postoperative hospitalization (17.1 ± 9.1 vs. 10.8 ± 5.4 days; P = 0.026). At discharge, 52 patients (96.3%) had favorable outcomes (Glasgow Outcome Scale score ≥4). Forty-three patients (79.6%) received 1 year follow-up after treatment; 97.7% (n = 42) of these had ongoing favorable outcomes. However, 4 patients with low-grade BAVM had recurrence.

CONCLUSIONS

The hybrid operation room can ensure safe, comprehensive treatment of BAVM, offering the opportunity for a favorable curative treatment in 1 stage.

Patient-Specific Blood Flow Analysis for Cerebral Arteriovenous Malformation Based on Digital Subtraction Angiography Images

Real-time digital subtraction angiography (DSA) is capable of revealing the cerebral vascular morphology and blood flow perfusion patterns of arterial venous malformations (AVMs). In this study, we analyze the DSA images of a subject-specific left posterior AVM case and customize a generic electric analog model for cerebral circulation accordingly. The generic model consists of electronic components representing 49 major cerebral arteries and veins, and yields their blood pressure and flow rate profiles. The model was adapted by incorporating the supplying and draining patterns of the AVM to simulate some typical AVM features such as the blood "steal" syndrome, where the flow rate in the left posterior artery increases by almost three times (∼300 ml/min vs 100 ml/min) compared with the healthy case. Meanwhile, the flow rate to the right posterior artery is reduced to ∼30 ml/min from 100 ml/min despite the presence of an autoregulation mechanism in the model. In addition, the blood pressure in the draining veins is increased from 9 to 22 mmHg, and the blood pressure in the feeding arteries is reduced from 85 to 30 mmHg due to the fistula effects of the AVM. In summary, a first DSA-based AVM model has been developed. More subject-specific AVM cases are required to apply the presented in silico model, and in vivo data are used to validate the simulation results.

Association of intracranial arteriovenous malformation embolization with more rapid rate of perfusion in the peri-nidal region on color-coded quantitative digital subtraction angiography

BACKGROUND

Hemodynamic alterations post-embolization of intracranial arteriovenous malformations (AVMs) may cause delayed edema/hemorrhage in brain parenchyma adjacent to the lesion.

OBJECTIVE

To quantify and compare cerebral perfusion changes in the peri-AVM territory pre- and post-embolization using color-coded quantitative digital subtraction angiography (q-DSA).

METHODS

Pediatric intracranial AVM embolization procedures performed over a 5 year period were included. DSA images of all patients were retrospectively assessed using syngo iFlow. Regions of interest (ROI) were selected on anteroposterior and lateral q-DSA views: three in the peri-AVM region; two in parenchyma distant from the AVM. Time-to-peak (TTP) contrast enhancement of ROIs and ∆TTP (TTP at the selected ROI minus TTP at either the ipsilateral internal carotid/vertebral artery) were measured.

RESULT

19 pediatric patients with 19 AVMs (9 males/10 females, mean age 12 years) underwent intracranial AVM embolization: 15/19 AVMs were supplied by the anterior circulation and 4/19 by the posterior circulation. Blood flow was significantly slower post-embolization in the draining vein (19/19) (p<0.01), and the venous sinus outflow (17/19) (p<0.01), by mean difference of 2.01±1.31 s and 1.74±2.04 s. There was significantly increased peri-AVM parenchymal perfusion post-embolization (∆TTP=2.20±0.48 s) compared with pre-embolization (∆TTP=2.52±0.42 s), by an average ∆TTP of 0.33±0.53 s (p=0.014). In contrast, there was no perfusion difference (∆TTP=0.03±0.20 s, p=0.8) between pre- and post-embolization in the distant parenchyma. The size of the AVM was not correlated with change in peri-nidal parenchymal perfusion (r=-0.136, p=0.579).

CONCLUSION

This study demonstrates more rapid perfusion in the peri-nidal brain parenchyma post-embolization of the AVM, which supports the theory that increased perfusion in normal tissue surrounding the AVM after embolization may underlie some post-procedural complications.

Experimental rat model of chronic cerebral hypoperfusion-reperfusion mimicking normal perfusion pressure breakthrough phenomenon

BACKGROUND

Normal perfusion pressure breakthrough (NPPB) phenomenon is a major life-threatening complication that restricts the treatment of complex intracranial arteriovenous malformations. The aim of the study it to develop a rat model mimicking NPPB phenomenon that enables the evaluation of any therapy to prevent such complication.

METHODS

Twenty Wistar male rats were randomly assigned to either a study or a control group. Study animals underwent an end-to-side left external jugular vein-common carotid artery anastomosis and ligation of bilateral external carotid arteries. Control animals only underwent ligation of bilateral external carotid arteries. All animals were sacrificed sixty days after the procedure. Hemodynamic parameters [mean arterial pressure (MAP), intracranial pressure (ICP) and cerebral perfusion pressure (CPP)], blood-brain barrier (BBB) permeability (measured by fluorescein staining) and histological features were then compared between both groups.

RESULTS

A significant decrease in MAP and CPP was confirmed in the study group. An increase in ICP was also observed. A significant decrease in MAP and CPP was also present in the study group when comparing preoperative values with those recorded on days 0 (postoperative), 7 and 60. Fluorescein staining findings were consistent with signs of BBB disruption in study animals. Histological analysis demonstrated an increased number of pyknotic neurons in the ipsilateral hemisphere of rat brains included in the study group.

CONCLUSION

These results confirm that this model mimics a vascular steal state with chronic cerebral hypoperfusion comparable to patients with AVMs behavior and disruption of the BBB after fistula closure comparable to NPPB phenomenon disorders.

Postoperative hemodynamic management in patients undergoing resection of cerebral arteriovenous malformations: A retrospective study

Strict control of blood pressure (BP) has been recommended in patients after surgical resection of cerebral arteriovenous malformations (AVM) to prevent postoperative hyperemic complication. The aim of this study was to review the postoperative hemodynamic management in patients after surgical resection of cerebral AVM and the incidence of postoperative intracranial hemorrhage and/or cerebral edema. After the ethics approval, we retrospectively reviewed the medical records of 207 adult patients who underwent elective surgical resection of cerebral AVM from Jan 2005 to Oct 2016 in a single university hospital. We determined the incidence of postoperative symptomatic intracranial hemorrhage and/or cerebral edema, and reviewed the quality of postoperative BP control during the first 72 h postoperatively. Two hundred and seven patients who underwent cerebral AVM resection were included. The median (IQR) of postoperative maximal systolic BP target was 110 (100-120) mmHg but the range was 90-150 mmHg. Failed hemodynamic control was consistently found in half of the patients during the first 72 h postoperatively. The incidence of postoperative intracranial hemorrhage and/or cerebral edema was 4.4% (9/207 patients). All 9 of these patients experienced a hypertensive event prior to their postoperative hyperemic complication. Two patients required induced hypertension to treat postoperative symptomatic cerebral edema. We concluded that postoperative intracranial hemorrhage and/or cerebral edema is not an uncommon complication after surgical resection of cerebral AVM. Further studies are required to develop a more effective strategy to implement strict BP control in the postoperative period.

Spetzler-Martin grade IV and V arteriovenous malformations: Treatment outcomes and risk factors for negative outcomes after surgical resection

OBJECTIVE

Microsurgical resection may be recommended for high grade brain arteriovenous malformations (BAVMs) (HBAVMs) in individualized patients. Careful case selection is necessary to minimize postoperative complications. The aim of this study was to determine the surgical outcomes in patients with HBAVMs and to identify their risk factors associated with postoperative negative outcomes.

PATIENTS AND METHODS

We retrospectively studied 53 consecutive patients with HBAVMs. All patients had undergone preoperative diffusion tensor imaging (DTI), MRI, 3D time-of-flight MRA (3D TOF-MRA) and digital subtraction angiography (DSA) followed by resection. White matter (WM) eloquent fibre tracts, including the corticospinal tract (CST), optic radiation (OR) and arcuate fasciculus (AF), were tract. Both functional, angioarchitectural and operative factors were analyzed with respect to the surgical outcomes.

RESULTS

Nineteen (35.8%) patients suffered from negative surgical outcomes (MRS > 2) one week after surgery. At the last clinic visit, 10 patients (18.9%) suffered from negative surgical outcomes. Diffuse nidus (P = 0.018), Perforating arteries (PA) supplying (P = 0.009) and CST involving (P = 0.001) were independent risk factors for negative short-term outcomes. PA supplying (P = 0.039), CST involving (P = 0.026) and postoperative intracranial haemorrhage (ICH) (P = 0.014) were independent risk factors for negative long-term neurological outcomes. Larger nidus size (P = 0.024) was predictor of postoperative ICH. The cut-off point was 6.8 cm.

CONCLUSIONS

This study identified that diffuse nidus, PA supplying and CST involving are risk factors for negative short-term outcomes in patients with HBAVMs. PA supplying, CST involving and postoperative ICH are risk factors for negative long-term outcomes. Larger nidus size was risk factor for postoperative ICH.

Assessment of periprocedural hemodynamic changes in arteriovenous malformation vessels by endovascular dual-sensor guidewire

Endovascular embolization is an important modality in the treatment of brain AVMs. Nowadays staged embolization is the method of choice for the prevention of perioperative hemorrhagic complications. Current theory suggests that simultaneous occlusion of more than 60% of AVM volume induces significant redistribution local blood flow. That, in turn, may lead to hemorrhage due to AVM rupture. Aside from angiographic findings, there is still no method that predicts the degree of safe partial embolization. Intraluminal measurement of flow velocity and pressure in the vicinity of the AVM nidus might allow detecting the changes in local hemodynamics. That can provide a valuable data and shed the light on the origin of vascular catastrophes. Ten patients underwent 12 embolization sessions with intraluminal flow velocity and pressure monitoring. The measurements were performed by dual-sensor guidewire. The "Combomap" (Volcano) system with Combowire microguidewires was chosen for measurements, as there is a documented experience of safe use of said guidewires in the cerebral vasculature. The findings observed during the study matched empirical data as well as the current physiological hypothesis of AVM hemorrhage. In conjunction with DSA runs, intraluminal flow velocity and pressure monitoring has the potential to become a valuable tool in AVM treatment.

Hemodynamics Associated With Intracerebral Arteriovenous Malformations: The Effects of Treatment Modalities

The understanding of the physiology of cerebral arteriovenous malformations (AVMs) continues to expand. Knowledge of the hemodynamics of blood flow associated with AVMs is also progressing as imaging and treatment modalities advance. The authors present a comprehensive literature review that reveals the physical hemodynamics of AVMs, and the effect that various treatment modalities have on AVM hemodynamics and the surrounding cortex and vasculature. The authors discuss feeding arteries, flow through the nidus, venous outflow, and the relative effects of radiosurgical monotherapy, endovascular embolization alone, and combined microsurgical treatments. The hemodynamics associated with intracranial AVMs is complex and likely changes over time with changes in the physical morphology and angioarchitecture of the lesions. Hemodynamic change may be even more of a factor as it pertains to the vast array of single and multimodal treatment options available. An understanding of AVM hemodynamics associated with differing treatment modalities can affect treatment strategies and should be considered for optimal clinical outcomes.

Deliberate employment of postoperative hypotension for brain arteriovenous malformation surgery and the incidence of delayed postoperative hemorrhage: a prospective cohort study

OBJECTIVE

The aim of this study was to examine the impact of deliberate employment of postoperative hypotension on delayed postoperative hemorrhage (DPH) for all Spetzler-Ponce Class (SPC) C brain arteriovenous malformations (bAVMs) and SPC B bAVMs ≥ 3.5 cm in diameter (SPC B 3.5+).

METHODS

A protocol of deliberate employment of postoperative hypotension was introduced in June 1997 for all SPC C and SPC B 3.5+ bAVMs. The aim was to achieve a maximum mean arterial blood pressure (BP) ≤ 70 mm Hg (with cerebral perfusion pressure > 50 mm Hg) for a minimum of 7 days after resection of bAVMs (BP protocol). The authors compared patients who experienced DPH (defined as brain hemorrhage into the resection bed that resulted in a new neurological deficit or that resulted in reoperation during the hospitalization for microsurgical bAVM resection) between 2 periods (prior to adopting the BP protocol and after introduction of the BP protocol) and 4 bAVM categories (SPC A, SPC B 3.5− [that is, SPC B < 3.5 cm maximum diameter], SPC B 3.5+, and SPC C). Patients excluded from treatment by the BP protocol were managed in the intensive care unit to avoid moderate hypertensive episodes. The pooled cases of all bAVM treated by surgery were analyzed to identify characteristics associated with the risk of DPH. These identified characteristics were then examined by multiple logistic regression analysis in both SPC B 3.5+ and SPC C cases.

RESULTS

From a cohort of 641 bAVMs treated by microsurgery, 32 patients with DPH were identified. Of those, 66% (95% CI 48–80) had a permanent new neurological deficit with a modified Rankin Scale score of 2–6. This included a mortality rate of 13% (95% CI 4.4–29). The BP protocol was used to treat 162 patients with either SPC B 3.5+ or SPC C. For SPC B 3.5+, there was no significant reduction in DPH with the introduction of the BP protocol (p = 0.77). For SPC C, there was a significant (p = 0.035) reduction of DPH from 29% (95% CI 13%–53%) to 8.2% (95% CI 3.2%–18%) associated with the introduction of the BP protocol. Multiple logistic regression analysis found that the absence of the BP protocol (p = 0.011, odds ratio 7.5, 95% CI 1.6–36) remained significant for the development of DPH in patients with SPC C bAVMs.

CONCLUSIONS

Treating patients with SPC C bAVMs with a protocol that lowers BP immediately after resection seems to reduce the risk of DPH. For SPC A and SPC B 3.5− bAVMs, there is unlikely to be a need to do more than avoid postoperative hypertension. For SPC B 3.5+ bAVMs, a larger number of patients would be required to test the absence of benefit of the BP protocol.

Ascertaining the Value of Noninvasive Measures Obtained Using Color Duplex Ultrasound and Central Aortic Pressure Monitoring During the Management of Cerebral Arteriovenous Malformation Resection: Protocol for a Prospective, Case Control Pilot Study

BACKGROUND

Dramatic hemodynamic changes occur upon removal of an arteriovenous malformation of the brain (bAVM) with a number of potentially serious perioperative complications, such as intracranial hemorrhage and venous occlusive hypertensive syndrome. As these complications largely occur in the postoperative inpatient period, a rapid, repeatable noninvasive investigation to serially monitor relevant intracranial hemodynamics may be of benefit. Though, transcranial Doppler (TCD) and transcranial color duplex (TCCD) are techniques used and available to provide hemodynamic measurements postoperatively, the time course of hemodynamic sequences following bAVM resection remains uncertain.

OBJECTIVE

This is a prospective, case control pilot study conducted in participants having elective bAVM resection surgery.

METHODS

Each participant will undergo a preoperative color duplex ultrasound (CDU) of the bilateral extracranial carotid arteries, a CDU of the circle of Willis including the bAVM vessels, and a central aortic pressure measurement, repeated daily, postoperatively, for a 2-week period.

RESULTS

Patient accrual has commenced with anticipation of first results in 2018.

CONCLUSIONS

This protocol aims to strengthen the work of previous authors by providing documentation of the time course of hemodynamic changes following bAVM resection. The protocol is designed to determine whether noninvasive technology, including CDU imaging of the extracranial carotid and intracranial arteries in the form of TCCD along with central aortic pressure measurements, can determine whether there are any hemodynamically significant prognostic markers that may provide insight into the process of vessel remodeling, including insight into venous changes following bAVM resection.

Hemodynamic Perturbations in Cerebral Arteriovenous Malformations and Management Implications

Cerebral AVMs have high flow, low resistance shunts that induce regional hemodynamic disturbances and possibly neural derangements. A better understanding of these mechanisms may help treatment planning and the management of complications after endovascular or surgical treatment.

Although the precise mechanisms of hemodynamic perturbation are still relatively unclear, the presence of chronic cerebral hypoperfusion is central and widely believed to be associated with both neurological deficits at presentation (‘steal‘) and ‘hyperemic’ complications following shunt obliteration. The ‘normal perfusion pressure breakthrough‘ (NPPB) theory states that chronic hypoperfusion around AVMs induces the loss of autoregulatory capability; following AVM shunt obliteration, perfusion pressure elevation induces an increase in flow, due to ‘vasomotor paralysis’, which can cause hemorrhage. The ‘dissociative vasoparalysis' theory suggests that vasodilation is preserved but not vasoconstriction. However, pharmacologic exploration of cerebral autoregulation with induced vasoconstriction (phenylephrine) and vasodilatation (acetazolamide) helps identify 3 patterns of autoregulatory behavior. The vast majority of AVM patients appear to retain autoregulatory capability, despite low arterial feeding pressures, consistent with a “shift to the left” of the autoregulation curve. Pronounced hypotension may “exhaust” cerebrovascular reserve in some patients, predisposing to hemorrhagic complications in the post-operative period. Lastly, “vasoparalysis” may coexist with a combination of vascular insult and marked hypotension.

Clinical presentation, AVM angioarchitecture and peri-operative physiologic data (especially feeding artery and venous outflow pressures) may assist patient management. Patients can be identified in whom staged treatment is recommended initially. Following AVM obliteration, the patient's hemodynamic response, which may range from a minimal increase in A-V pressure gradient to significant CBF increase may be predicted, and blood pressure, fluid and ICP management adjusted accordingly, as the monitoring of post-operative cerebral hemodynamics remains difficult. Extreme attention to endovascular and operative technique must be exercised, as technical problems can be devastating.

Although incompletely understood, hemodynamic derangements associated with cerebral AVMs increasingly appear to be associated with intact cerebral autoregulation in most patients. As cerebral hemodynamics monitoring remains challenging, clinical, angiographic and physiologic data from interventional/operative monitoring must be used to guide patient management.

Risk Reduction of Cerebral Stroke After Stereotactic Radiosurgery for Small Unruptured Brain Arteriovenous Malformations

Background and Purpose—

A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA) indicated the superiority of medical management in reducing the risks for strokes and other neurological deficits over observation alone. The aim of our study was to verify the rationale for stereotactic radiosurgery (SRS) for small unruptured arteriovenous malformation.

Methods—

A retrospective review was performed for 292 patients with unruptured arteriovenous malformations referred for SRS. The risks for cerebral hemorrhages were statistically compared before and after SRS.

Results—

Of the 292 patients in whom arteriovenous malformation was found unruptured at initial diagnosis, 17 sustained hemorrhages in the period between the diagnosis and the initial therapeutic intervention (annual bleeding rate, 2.1%; 95% confidence interval [CI], 1.2%–3.4%). Of the remaining 275 patients, 240 were initially treated with SRS, and 16 sustained a hemorrhage after SRS (annual bleeding rate, 1.1%; 95% CI, 0.6%–1.8%), but only 2 sustained a hemorrhage after angiographic obliteration (annual bleeding rate, 0.3%; 95% CI, 0.04%–1.2%). Comparing the risk of hemorrhage between the periods before and after SRS, a 53% risk reduction was achieved after SRS (hazard ratio, 0.47; 95% CI, 0.24–0.94; P =0.03), and 85% reduction was achieved after angiographic obliteration (hazard ratio, 0.15; 95% CI, 0.02–0.53; P =0.002).

Conclusions—

SRS can significantly reduce the risk of stroke in the patients with small unruptured arteriovenous malformations. To definitively determine the clinical benefits of SRS, a longer follow-up will be necessary. However, based on our results, we can recommend SRS for patients who face a latent risk for stroke from this intractable vascular disease.

Radiosurgery for Cerebral Arteriovenous Malformations in A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA)-Eligible Patients: A Multicenter Study

BACKGROUND AND PURPOSE

The benefit of intervention for patients with unruptured cerebral arteriovenous malformations (AVMs) was challenged by results demonstrating superior clinical outcomes with conservative management from A Randomized Trial of Unruptured Brain AVMs (ARUBA). The aim of this multicenter, retrospective cohort study is to analyze the outcomes of stereotactic radiosurgery for ARUBA-eligible patients.

METHODS

We combined AVM radiosurgery outcome data from 7 institutions participating in the International Gamma Knife Research Foundation. Patients with ≥12 months of follow-up were screened for ARUBA eligibility criteria. Favorable outcome was defined as AVM obliteration, no postradiosurgery hemorrhage, and no permanently symptomatic radiation-induced changes. Adverse neurological outcome was defined as any new or worsening neurological symptoms or death.

RESULTS

The ARUBA-eligible cohort comprised 509 patients (mean age, 40 years). The Spetzler-Martin grade was I to II in 46% and III to IV in 54%. The mean radiosurgical margin dose was 22 Gy and follow-up was 86 months. AVM obliteration was achieved in 75%. The postradiosurgery hemorrhage rate during the latency period was 0.9% per year. Symptomatic and permanent radiation-induced changes occurred in 11% and 3%, respectively. The rates of favorable outcome, adverse neurological outcome, permanent neurological morbidity, and mortality were 70%, 13%, 5%, and 4%, respectively.

CONCLUSIONS

Radiosurgery may provide durable clinical benefit in some ARUBA-eligible patients. On the basis of the natural history of untreated, unruptured AVMs in the medical arm of ARUBA, we estimate that a follow-up duration of 15 to 20 years is necessary to realize a potential benefit of radiosurgical intervention for conservative management in unruptured patients with AVM.

Endovascular and microsurgical treatment of cerebral arteriovenous malformations: Current recommendations

Background:

Cerebral arteriovenous malformations (AVMs) can be a heterogeneous pathological entity whose management requires a complex decision-making process due to the risks associated with their treatment and natural history. Despite the recently published conclusions of the aborted Randomized Trial of Brain Unruptured AVMs (ARUBA) trial, the authors of this article believe multimodality intervention in general and microsurgical resection in particular continue to play a major role in the management of carefully selected ruptured or unruptured AVMs.

Methods:

The authors provide an overview of their methodology for endovascular intervention and microsurgical resection and share their technical nuances for successful embolization and microsurgical resection of AVMs with special emphasis on complication avoidance.

Results:

The authors have achieved successful outcomes in embolization and resection of cerebral AVMs when using their methodology.

Conclusions:

These lesions are among the most technically difficult pathological entities handled by the cerebrovascular specialist, and an overview of technical concepts to help systematize this challenging and variable endeavor can improve the safety of their treatment.

Normal perfusion pressure breakthrough theory: a reappraisal after 35 years

The intrinsic ability of the brain to maintain constant cerebral blood flow (CBF) is known as cerebral pressure autoregulation. This ability protects the brain against cerebral ischemia and hyperemia within a certain range of blood pressures. The normal perfusion pressure breakthrough (NPPB) theory described by Spetzler in 1978 was adopted to explain the edema and hemorrhage that sometimes occur after resection of brain arteriovenous malformations (AVMs). The underlying pathophysiology of edema and hemorrhage after AVM resection still remains controversial. Over the last three decades, advances in neuroimaging, CBF, and cerebral perfusion pressure (CPP) measurement have both favored and contradicted the NBBP theory. At the same time, other theories have been proposed, including the occlusive hyperemia theory. We believe that both theories are related and complementary and that they both explain changes in hemodynamics after AVM resection. The purpose of this work is to review the current status of the NBBP theory 35 years after its original description.

Use of intracranial and ocular thermography before and after arteriovenous malformation excision

Excision of arteriovenous malformations (AVMs) is known to carry a risk of postoperative hemorrhage, postulated to be the result of normal perfusion pressure breakthrough. It is also possible that AVMs may cause a steal effect, reducing perfusion in nearby vessels. There is currently no simple method of visualizing the presence or absence of steal effect intraoperatively. We hypothesized that the infrared thermographic (heat sensitive) imaging of perilesional brain may be useful for detecting reduced perfusion due to steal. Moreover, we hypothesized that if steal effect was present, it could impact on ocular perfusion and thereby temperature. Our objective was, therefore, to investigate whether perilesional cortical and ocular temperature (OT) may be a marker of steal effect. We intraoperatively acquired conventional and thermal images of the surgical field and eyes bilaterally, pre- and post-excisions of a large left hemisphere AVM. We found OT asymmetry preoperatively, which was absent after the AVM was excised. Intraoperative thermal images showed an increase of perilesional temperature, although this could be confounded by generalized changes in cortical perfusion due to anesthetics or surgery.

Management of intracranial aneurysms associated with arteriovenous malformations

Intracranial or brain arteriovenous malformations (BAVMs) are some of the most interesting and challenging lesions treated by the cerebrovascular neurosurgeon. It is generally believed that the combination of BAVMs and intracranial aneurysms (IAs) is associated with higher hemorrhage rates at presentation and higher rehemorrhage rates and thus with a more aggressive course and natural history. There is wide variation in the literature on the prevalence of BAVM-associated aneurysms (range 2.7%–58%), with 10%–20% being most often cited in the largest case series. The risk of intracranial hemorrhage in patients with unruptured BAVMs and coexisting IAs has been reported to be 7% annually, compared with 2%–4% annually for those with BAVM alone. Several different classification systems have been applied in an attempt to better understand the natural history of this combination of lesions and implications for treatment. Independent of the classification used, it is clear that a few subtypes of aneurysms have a direct hemodynamic correlation with the BAVM itself. This is exemplified by the fact that the presence of a distal flow-related or an intranidal aneurysm appears to be associated with an increased hemorrhage risk, when compared with an aneurysm located on a vessel with no direct supply to the BAVM nidus. Debate still exists regarding the etiology of the association between those two vascular lesions, the subsequent implications for patients’ risk of hemorrhagic stroke, and finally the determination of which patients warrant treatment and when. The ultimate goals of the treatment of a BAVM associated with an IA are to prevent hemorrhage, avoid stepwise neurological deterioration, and eliminate the mortality risk associated with recurrent hemorrhagic events. The treatment is only justifiable if the risks associated with an intervention are lower than or equivalent to the long-term risks of disability or mortality caused by the lesion itself. When faced with this difficult decision, a few questions need to be answered by the treating neu-rosurgeon: What is the mode of presentation? What is the symptomatic lesion? Which one of the lesions bled? What is the relationship between the BAVM and IA? Is it possible to safely treat both BAVM and IA? The objective of this review is to discuss the demographics, natural history, classification, and strategies for management of BAVMs associated with IAs.

Hemorrhagic complications after endovascular treatment of cerebral arteriovenous malformations

BACKGROUND AND PURPOSE

Intracranial hemorrhage is the most severe complication of brain arteriovenous malformation treatment. We report our rate of hemorrhagic complications after endovascular treatment and analyze the clinical significance and potential mechanisms, with emphasis on cases of delayed hemorrhage after uneventful embolization.

MATERIALS AND METHODS

During a 10-year period, 846 embolization procedures were performed in 408 patients with brain AVMs. Any cases of hemorrhagic complications were identified and divided into those related or unrelated to a periprocedural arterial tear (during catheter navigation or catheter retrieval). We analyzed the following variables: sex, age, hemorrhagic presentation, Spetzler-Martin grade, size of the AVM, number of embolized pedicles, microcatheter used, type and volume of liquid embolic agent injected, and the presence of a premature venous occlusion. Univariate and multivariate multiple regression analyses were performed to identify risk factors for hemorrhagic complications.

RESULTS

A hemorrhagic complication occurred in 92 (11%) procedures. Forty-four (48%) complications were related to a periprocedural arterial perforation, and 48 (52%) were not. Hemorrhagic complications unrelated to an arterial perforation were located more commonly in the cerebral parenchyma, caused more neurologic deficits, and were associated with worse prognosis than those in the arterial perforation group. Only premature venous occlusion was identified as an independent predictor of hemorrhagic complication in the nonperforation group. Premature venous occlusion was significantly related to the ratio of Onyx volume to nidus diameter.

CONCLUSIONS

Higher injected volume of embolic agent and deposition on the venous outflow before complete occlusion of the AVM may account for severe hemorrhagic complications.

Normal perfusion pressure breakthrough phenomenon: experimental models

One of the most life-threatening complications after the obliteration of intracranial arteriovenous malformations is the development of oedema and/or multifocal haemorrhage. Two main theories have been postulated so far in order to explain this situation. On one hand, "normal perfusion pressure breakthrough phenomenon" is based on the loss of cerebral vessel autoregulation due to the chronic vasodilation of perinidal microcirculation. On the other hand, the "occlusive hyperaemia" deals with thrombotic and venous obstruction phenomena that may also generate such manifestations. The aim of this study is to resume the main concepts of the "normal perfusion pressure breakthrough phenomenon" theory as well as the related animal models described up to date, their advantages and disadvantages, and the main conclusions obtained as a result of the experimental research.

Benefit of cone-beam computed tomography angiography in acute management of angiographically undetectable ruptured arteriovenous malformations

Object

Ruptured arteriovenous malformations (AVMs) are a frequent cause of intracerebral hemorrhage (ICH). In some cases, compression from the associated hematoma in the acute setting can partially or completely occlude an AVM, making it invisible on conventional angiography techniques. The authors report on the successful use of cone-beam CT angiography (CBCT-A) to precisely identify the underlying angioarchitecture of ruptured AVMs that are not visible on conventional angiography.

Methods

Three patients presented with ICH for which they underwent examination with CBCT-A in addition to digital subtraction angiography and other imaging modalities, including MR angiography and CT angiography. All patients underwent surgical evacuation due to mass effect from the hematoma. Clinical history, imaging studies, and surgical records were reviewed. Hematoma volumes were calculated.

Results

In all 3 cases, CBCT-A demonstrated detailed anatomy of an AVM where no lesion or just a suggestion of a draining vein had been seen with other imaging modalities. Magnetic resonance imaging demonstrated enhancement in 1 patient; CT angiography demonstrated a draining vein in 1 patient; 2D digital subtraction angiography and 3D rotational angiography demonstrated a suggestion of a draining vein in 2 cases and no finding in the third. In the 2 patients in whom CBCT-A was performed prior to surgery, the demonstrated AVM was successfully resected without evidence of a residual lesion. In the third patient, CBCT-A allowed precise targeting of the AVM nidus using Gamma Knife radiosurgery.

Conclusions

Cone-beam CT angiography should be considered in the evaluation and subsequent treatment of ICH due to ruptured AVMs. In cases in which the associated hematoma compresses the AVM nidus, CBCT-A can have higher sensitivity and anatomical accuracy than traditional angiographic modalities, including digital subtraction angiography.

The pre-treatment effect on brain injury during restoration of normal perfusion pressure with hemodilution in a new rat model of chronic cerebral hypoperfusion

OBJECTIVES

To investigate the effect of hemodilution with high-concentration human serum albumin (HSA) on brain injury in a rat model of chronic cerebral hypoperfusion associated with arteriovenous malformations.

METHODS

The animal model was established by creating a fistula through an end-to-side anastomosis between the right distal external jugular vein and the ipsilateral common carotid artery, followed by ligation of the left vein draining the transverse sinus and bilateral external carotid arteries. The agent (20% HSA) or control solution (0.9% sodium chloride) was administered intravenously at a dosage of 1% body weight 24 hours before ligation of the fistula. Blood-brain barrier (BBB) disruption was judged by extravasation of Evans blue (EB) dye. EB, water content and the changes of myeloperoxidase (MPO) activity and superoxide dismutase (SOD) activity in rat brains 24 hours after ligation of the fistula were determined.

RESULTS

EB and water content in rat brains of the pre-treated group were significantly decreased compared with the control group accompanied by reduction of MPO activity and enhancement of SOD activity.

DISCUSSION

Hemodilution with high-concentration HSA has a certain pre-treatment effect on brain injury after ligation of the fistula in rat model of chronic cerebral hypoperfusion, which may be resulted from improved microcirculation, decrease in inflammatory cell infiltration and inactivation of oxygen free radicals.

A study on blood–brain barrier ultrastructural changes induced by cerebral hypoperfusion of different stages

OBJECTIVES

To evaluate the ultrastructural changes in the blood-brain barrier (BBB) induced by cerebral hypoperfusion of different stages, which may predispose the brain to the formation of vasogenic edema and hemorrhage under cerebral luxury perfusion.

METHODS

Twenty cerebral steal models with left neck arteriovenous fistula (AVF) were surgically created in Wistar's rats, leading to a noninfarctional reduction in the cerebral blood flow (CBF) by between 25 and 50%, resulting in cerebral hypoperfusion in the AVF side for 3 days (acute stage), 3 weeks (subacute stage) and 3 months (chronic stage), respectively. Another six sham-operated models were made in age-matched rats as control. The BBB ultrastructural changes were assessed by transmission electron microscopy. Ridit analysis was conducted to compare the positive ratio of ultrastructural changes among multiple groups.

RESULTS

Electron microscopy demonstrated no ultrastructural change at the acute stage, however, at the subacute stage, slight vacuolar degeneration was found in the astrocytic foot process layer encircling the capillaries; furthermore, at the chronic stage, the astrocytic foot processes expressed marked vacuolization associated with the adjacent astrocytic degeneration. Meanwhile, in both capillary endothelium and basal lamina layers, no abnormal ultrastructures similar to those in the astrocytic foot processes layer were identified. After cerebral luxury perfusion took place, BBB was disrupted where astrocytic foot processes vacuolization was most distinguished.

CONCLUSION

Astrocytes generate ultrastructural abnormality as a result of chronic cerebral hypoperfusion. Astrocytic foot process vacuolization, which constitutes the major ultrastructural change in the BBB, is the extension of the degeneration of astrocyte body. It is inferred that BBB is prone to structure weakness and function instability, which forms the morphological basis of cerebral luxury perfusion.

Endovascular management of pediatric high-flow vertebro-vertebral fistula with reversed basilar artery flow. A case report and review of the literature

Vertebral artery arteriovenous fistula (VAVF) is mostly known as a post-traumatic and/or iatrogenic arteriovenous complication. However, spontaneous high-flow VAVF associated with flow reversal in the basilar artery has not been reported in children. We describe a unique asymptomatic presentation of a spontaneous high-flow VAVF associated with flow reversal in the basilar artery in a pediatric patient. The literature for classification, pathophysiology, treatment strategies, and post-procedural complications is also reviewed.

Pathophysiology of increased cerebrospinal fluid pressure associated to brain arteriovenous malformations: The hydraulic hypothesis

Background:

Brain arteriovenous malformations (AVMs) produce circulatory and functional disturbances in adjacent as well as in remote areas of the brain, but their physiological effect on the cerebrospinal fluid (CSF) pressure is not well known.

Methods:

The hypothesis of an intrinsic disease mechanism leading to increased CSF pressure in all patients with brain AVM is outlined, based on a theory of hemodynamic control of intracranial pressure that asserts that CSF pressure is a fraction of the systemic arterial pressure as predicted by a two-resistor series circuit hydraulic model. The resistors are the arteriolar resistance (that is regulated by vasomotor tonus), and the venous resistance (which is mechanically passive as a Starling resistor). This theory is discussed and compared with the knowledge accumulated by now on intravasal pressures and CSF pressure measured in patients with brain AVM.

Results:

The theory provides a basis for understanding the occurrence of pseudotumor cerebri syndrome in patients with nonhemorrhagic brain AVMs, for the occurrence of local mass effect and brain edema bordering unruptured AVMs, and for the development of hydrocephalus in patients with unruptured AVMs. The theory also contributes to a better appreciation of the pathophysiology of dural arteriovenous fistulas, of vein of Galen aneurismal malformation, and of autoregulation-related disorders in AVM patients.

Conclusions:

The hydraulic hypothesis provides a comprehensive frame to understand brain AVM hemodynamics and its effect on the CSF dynamics.

Anesthesia considerations and intraoperative monitoring during surgery for arteriovenous malformations and dural arteriovenous fistulas

The anesthetic considerations for surgical resection of arteriovenous malformations (AVMs) and dural arteriovenous fistulas (DAVFs) incorporate many principles that are common to craniotomies for other indications. However, a high-flow, low-resistance shunt results in chronic hypoperfusion of adjacent brain tissue that is vulnerable to ischemia and at high risk for hyperemia and hemorrhage as resection of the lesion redirects blood flow. A comprehensive understanding of AVM pathophysiology and rapidly titratable anesthetic and vasoactive agents allow the anesthesiologist to alter blood pressure targets as resection evolves for optimal patient outcome. Intensive management is continued post-operatively as the brain acclimatizes to new parameters.

Surgical treatment of cranial arteriovenous malformations and dural arteriovenous fistulas

Microsurgical resection remains the treatment of choice for more than half of all patients with arteriovenous malformations (AVMs). It reduces the treatment window to a span of a few weeks and is curative. Careful patient selection, meticulous surgical planning, and painstaking technical execution of surgery are typically rewarded with excellent outcomes. For dural arteriovenous fistulas (DAVFs), microsurgical obliteration is often reserved for cases in which endovascular therapy either cannot be pursued or fails. When performed, however, microsurgical obliteration of DAVFs is associated with excellent outcomes as well. This article reviews the current state of microsurgical treatment of AVMs and DAVFs.

Delayed Intracerebral Hemorrhage After Uneventful Embolization of Brain Arteriovenous Malformations Is Related to Volume of Embolic Agent Administered: Multivariate Analysis of 13 Predictive Factors

BACKGROUND:

The mechanisms and management of delayed intracerebral hemorrhage (dICH) after treatment of brain arteriovenous malformations (AVMs) are poorly understood and widely debated. Many clinical predictive factors have been theorized for dICH after an otherwise uneventful AVM embolization, but there is an absence of data to discern their significance.

OBJECTIVE:

To analyze 13 proposed predictive factors and to assess their potential in guiding prevention strategies.

METHODS:

One hundred sixty-eight embolization procedures were performed on 67 patients with brain AVMs by a single surgeon. Patients were divided into 2 groups: those with symptomatic dICH and control subjects. Thirteen factors were analyzed: age, sex, race, previous ICH, Spetzler-Martin grade, AVM size, eloquence, embolic volume, embolic agent, percent obliteration, and timing, number, and stage of embolizations. Univariate and multivariate analyses were performed on these factors to determine significance.

RESULTS:

Six procedures were complicated by dICH; 5 (83%) occurred after the final planned procedure. The volume of embolic agent was significantly higher in the dICH group (4.5 ± 1.0 mL) compared with control subjects (1.7 ± 0.2 mL) in both univariate and multivariate analyses (P &lt; .01), even after controlling for AVM size. AVM size was significant in univariate analysis but not multivariate analysis. There were no statistically significant differences between the groups for any of the other possible predictive factors.

CONCLUSION:

High volume of embolic agent administered per procedure is an independent predictive factor for dICH. Limiting the injected volume for each procedure may reduce this poorly understood complication.