Intention-to-treat analysis of Spetzler-Martin grades IV and V arteriovenous malformations: natural history and treatment paradigm

Advances in Radiosurgery for Arteriovenous Malformations of the Brain

Arteriovenous malformations of the brain are a considerable source of morbidity and mortality for patients who harbor them. Although our understanding of this disease has improved, it remains in evolution. Advances in our ability to treat these malformations and the modes by which we address them have also improved substantially. However, the variety of patient clinical and disease scenarios often leads us into challenging and complex management algorithms as we balance the risks of treatment against the natural history of the disease. The goal of this article is to provide a focused review of the natural history of cerebral arteriovenous malformations, to examine the role of stereotactic radiosurgery, to discuss the role of endovascular therapy as it relates to stereotactic radiosurgery, and to look toward future advances.

Radiosurgery for Spetzler-Martin Grade III arteriovenous malformations

OBJECT

Intracranial arteriovenous malformations (AVMs) are most commonly classified based on their Spetzler-Martin grades. Due to the composition of the Spetzler-Martin grading scale, Grade III AVMs are the most heterogeneous, comprising 4 distinct lesion subtypes. The management of this class of AVMs and the optimal treatment approach when intervention is indicated remain controversial. The authors report their experience with radiosurgery for the treatment of Grade III AVMs in a large cohort of patients.

METHODS

All patients with Spetzler-Martin Grade III AVMs treated with radiosurgery at the University of Virginia over the 20-year span from 1989 to 2009 were identified. Patients who had less than 2 years of radiological follow-up and did not have evidence of complete obliteration during that period were excluded from the study, leaving 398 cases for analysis. The median patient age at treatment was 31 years. The most common presenting symptoms were hemorrhage (59%), seizure (20%), and headache (10%). The median AVM volume was 2.8 cm(3), and the median prescription dose was 20 Gy. The median radiological and clinical follow-up intervals were 54 and 68 months, respectively. Univariate and multivariate Cox proportional hazards and logistic regression analysis were used to identify factors associated with obliteration, postradiosurgery radiation-induced changes (RIC), and favorable outcome.

RESULTS

Complete AVM obliteration was observed in 69% of Grade III AVM cases at a median time of 46 months after radiosurgery. The actuarial obliteration rates at 3 and 5 years were 38% and 60%, respectively. The obliteration rate was higher in ruptured AVMs than in unruptured ones (p < 0.001). Additionally, the obliteration rate for Grade III AVMs with small size (< 3 cm diameter), deep venous drainage, and location in eloquent cortex was higher than for the other subtypes (p < 0.001). Preradiosurgery AVM rupture (p = 0.016), no preradiosurgery embolization (p = 0.003), increased prescription dose (p < 0.001), fewer isocenters (p = 0.006), and a single draining vein (p = 0.018) were independent predictors of obliteration. The annual risk of postradiosurgery hemorrhage during the latency period was 1.7%. Two patients (0.5%) died of hemorrhage during the radiosurgical latency period. The rates of symptomatic and permanent RIC were 12% and 4%, respectively. Absence of preradiosurgery AVM rupture (p < 0.001) and presence of a single draining vein (p < 0.001) were independent predictors of RIC. Favorable outcome was observed in 63% of patients. Independent predictors of favorable outcome were no preradiosurgery hemorrhage (p = 0.014), increased prescription dose (p < 0.001), fewer isocenters (p = 0.014), deep location (p = 0.014), single draining vein (p = 0.001), and lower Virginia radiosurgery AVM scale score (p = 0.016).

CONCLUSIONS

Radiosurgery for Spetzler-Martin Grade III AVMs yields relatively high rates of obliteration with a low rate of adverse procedural events. Small and ruptured lesions are more likely to become obliterated after radiosurgery than large and unruptured ones.

Outcomes following single-session radiosurgery for high-grade intracranial arteriovenous malformations

INTRODUCTION

The management of Spetzler-Martin Grade-IV and -V arteriovenous malformations (AVMs) is controversial due to their uncertain natural history, the high rate of morbidity and mortality associated with microsurgical resection, and the relatively low rate of successful obliteration from less invasive approaches such as radiosurgery and embolization. We present our radiosurgical results for high-grade AVMs.

METHODS

We identified all patients with Spetzler-Martin Grade-IV and -V AVMs treated with single-session radiosurgery at the University of Virginia between 1989 and 2009. Patients with less than 2 years of follow-up without obliteration were excluded. This yielded 110 patients with a median age 27.6 years. The median AVM volume was 5.7 cc and prescription dose was 19 Gy. The median radiographic and clinical follow-up intervals were 88 and 97 months, respectively.

RESULTS

Complete AVM obliteration was identified on MRI only in 11 patients (10%) and confirmed by DSA in 38 patients (34%) for a cumulative obliteration rate of 44%. The actuarial rates of obliteration at 3 and 5 years were 10% and 23%, respectively. The mean and median times to obliteration were 60 months and 43 months, respectively. Significant independent predictors of obliteration were no pre-radiosurgery embolization (P = 0.008), superficial location (P = 0.001), and higher prescription dose (P = 0.028). The annual rate of post-radiosurgery hemorrhage was 3.0%, and symptomatic RIC was observed in 12% of patients. Unruptured AVMs were more likely to have RIC (P = 0.005). The rates of temporary and permanent post-radiosurgery clinical deterioration were 9% and 10%, respectively.

CONCLUSION

Single-session radiosurgery is an acceptable treatment option for select patients harboring high-grade AVMs for which microsurgery or conservative management are associated with an unacceptably high risk of adverse outcomes.

Prospective evaluation of preoperative stereotactic radiosurgery followed by delayed resection of a high grade arteriovenous malformation

Reports of the utility of preoperative radiation for shrinking large arteriovenous malformations (AVM) in preparation for resection have produced conflicting results, and to our knowledge no prospective studies are available. A 28-year-old man presented with a ruptured right temporal Spetzler-Martin Grade 5 AVM with deep venous drainage, involvement of the internal capsule, deep perforator supply, and a diffuse nidus. He underwent staged embolization, a single Gamma Knife (Elekta AB, Stockholm, Sweden) radiation treatment to the deepest portion of the nidus followed by complete surgical resection 3 years later. He suffered no long-term neurological deficits and has since returned to work symptom-free (modified Rankin Scale score 0). Preoperative radiosurgery is an effective method for downgrading high-grade AVM in preparation for surgery by targeting the deeper portions that abut or involve eloquent territory. To our knowledge this is the first such successful prospective report in the literature.

Durable thrombosis in a rat model of arteriovenous malformation treated with radiosurgery and vascular targeting

OBJECT

Radiosurgical treatment of brain arteriovenous malformations (AVMs) has the significant shortcomings of being limited to lesions smaller than 3 cm in diameter and of a latency-to-cure time of up to 3 years. A possible method of overcoming these limitations is stimulation of thrombosis by using vascular targeting. Using an animal model of AVM, the authors examined the durability of the thrombosis induced by the vascular-targeting agents lipopolysaccharide and soluble tissue factor conjugate (LPS/sTF).

METHODS

Stereotactic radiosurgery or sham radiation was administered to 32 male Sprague-Dawley rats serving as an animal model of AVM; 24 hours after this intervention, the rats received an intravenous injection of LPS/sTF or normal saline. The animals were killed at 1, 7, 30, or 90 days after treatment. Immediately beforehand, angiography was performed, and model AVM tissue was harvested for histological analysis to assess rates of vessel thrombosis.

RESULTS

Among rats that received radiosurgery and LPS/sTF, induced thrombosis occurred in 58% of small AVM vessels; among those that received radiosurgery and saline, thrombosis occurred in 12% of small AVM vessels (diameter < 200 μm); and among those that received LPS/sTF but no radiosurgery, thrombosis occurred at an intermediate rate of 43%. No systemic toxicity or intravascular thrombosis remote from the target region was detected in any of the animals.

CONCLUSIONS

Vascular targeting can increase intravascular thrombosis after radiosurgery, and the vessel occlusion is durable. Further work is needed to refine this approach to AVM treatment, which shows promise as a way to overcome the limitations of radiosurgery.

[Endovascular treatment of intracranial arteriovenous malformation with n-butyl cyanoacrylate. Working methods and experience in 58 cases]

BACKGROUND AND PURPOSE

Arteriovenous malformations (AVMs) constitute malformative lesions of the central nervous system vasculature and cause significant morbidity and mortality. Endovascular embolization with n-butyl cyanoacrylate is a well established modality of AVM treatment, usually combined with surgery or radiosurgery. The purpose of this study was to characterise the AVMs that were treated endovascularly with n-butyl cyanoacrylate and to evaluate the post-embolization results in the Cuban population.

MATERIALS AND METHODS

From February 2006 to February 2011, a group of 58 consecutive patients with brain AVMs were embolized using n-butyl cyanoacrylate in the endovascular therapy unit of the Medical Surgical Research Centre in Havana (Cuba). In all, 91sessions were carried out with intranidal embolization and mainly partial devascularization, 25-30% per session, and closing 123 arterial pedicles. Safety times for n-butyl cyanoacrylate injection were established by calculating the polymerisation times for different dilutions, using post-embolisation hypotension systematically, as well as a superselective test with propofol to determine cerebral eloquence.

RESULTS

Haemorrhagic signs were the initial presentation in 68.8% of the patients, 24.1% presented with epileptic episodes and 1.7% with ischemic stroke. Of the AVMs, 93.2% were supratentorial; according to the Spetzler and Martin classification, 13.8% were grade II, 56.9% were grade III, 22.4% were grade IV and 6.8%, grade V. One hundred and twenty-eight selective tests with propofol were performed and 118 (92.2%) of those were negative. Partial devascularization (20-30%) prevailed; complete obliteration was achieved in 17.2% of the patients and 70%-99% in 27.5% of the patients. Safety times for n-butyl cyanoacrylate injection were established and the use of post-procedure hypotension was settled. Morbidity of 17.2%, with 6.9% haemorrhagic complications and mortality of 3.4% were registered in the whole series.

CONCLUSIONS

The rates of total occlusion and of morbidity and mortality in the series are in the internationally described ranges. The implementation of intranidal closings with 20-30% devascularization per session and the use of post-embolization hypotension after the haemorrhage complications described resulted in the total absence of haemorrhagic complications.

Combined staged therapy of complex arteriovenous malformations: initial experience

OBJECTIVES

Definitive treatment of complex supratentorial arteriovenous malformations (AVMs) has been classically assigned to ruptured or progressively symptomatic cases. The aim of this study is to report our initial experience in the treatment of complex AVMs by means of staged embolization with Onyx followed by microsurgery.

MATERIAL AND METHODS

Thirteen consecutive patients with supratentorial Spetzler-Martin grades III, IV and V AVMs were treated between January 2009 and June 2010. Mean age at the beginning of the therapy was 34. All patients were symptomatic. Mean AVM size was 48 mm, and mean volume prior to embolization was 47 ml.

RESULTS

Mean number of endovascular procedures was 3, and mean volumetric obliteration prior to surgery was 79.2%. Mean time between two embolizations was 24 days. One patient showed a non-disabling complication after endovascular procedures. Mean time between the last embolization and surgery was 42 days. Two patients showed disabling complications after surgery, and one patient showed a non-disabling complication. Follow-up angiography showed the complete removal of permeable AVM in all patients. According to the modified Rankin Scale, all patients were non-dependent concerning daily life activity at 6-month follow-up. One-year follow-up angiography has been performed in 11 patients so far showing an absence of permeable AVM in spite of the remainder intravascular Onyx.

CONCLUSIONS

Staged preoperative embolization with Onyx followed by microsurgery has made possible 100% cure of complex AVMs with 0% mortality, 15.4% disabling complications and 15.4% non-disabling complications. Complete Onyx resection is not essential to achieve the cure of the patient.

Total resection in a giant left frontal arteriovenous malformation, grade V Spetzler-Martin - Case report

Background: Giant arteriovenous malformations (AVMs) are congenital lesions, with nidus sizing more than 6 cm. According to Spetzler-Martin scale, grade V AVMs have a nidus larger than 6 cm in diameter, profound venous drainage and are located in eloquent areas.

Method: We report a case of a 39 years old woman, with giant left frontal AVM, grade V Spetzler-Martin, who was admitted for generalized seizures, with onset 32 years ago, refractory to full dose antiepileptic polytherapy, which severely impaired the patient’s quality of life.

Results: The patient underwent surgery and we performed total resection of the AVM. We emphasize on surgical technique, intraoperative difficulties and outcome.

Conclusions: Surgery is the therapy of choice in AVMs, because it provides cure of the lesion, and is the only treatment capable of preventing hemorrhage and controlling seizures. Management in grade V AVMs is challenging, because of their large size, multiple dilated arterial feeders from anterior and posterior circulation and external carotid arteries, high blood flow, vascular steel from the surrounding brain, enlarged draining veins, profound venous drainage and location in eloquent area. Giant AVMs with high flow nidus, causing a great degree of vascular steel in the surrounding brain, with hypoperfusion of normal parenchyma may develop early normal perfusion pressure breakthrough. Total resection in grade V AVMs can be performed with minimal transient morbidity and favorable outcome. Total resection permits control of intractable seizures with reduced dose of antiepileptic therapy.

Hypofractionated stereotactic radiotherapy for large or involving critical organs cerebral arteriovenous malformations

Background

The treatment of large arteriovenous malformations (AVMs) or AVMs involving eloquent regions of the brain remains a challenge. For inoperable lesions, observation, volume-staged radiosurgery or hypofractionated stereotactic radiotherapy (HFSRT) are proposed. The aim of our study was to assess the safety and efficiency of HFSRT for large AVMs located in eloquent areas of the brain.

Materials and methods

An analysis of records of 49 patients irradiated for cerebral AVMs with a mean dose of 19.9 Gy (12–28 Gy) delivered in 2–4 fractions with planned gap (at least one week) between fractions. Actuarial obliteration rates and annual bleeding hazard were calculated using Kaplan-Meier survival analysis and life tables.

Results

Annual bleeding hazard rates were 4.5% and 1.6% after one and two years of the follow-up, respectively. Actuarial total obliteration rates were 7%, 11%, and 21% and total response rate (total and partial obliterations) 22%, 41%, and 55% after one, two and three years of the follow-up, respectively. There was a trend towards larger total obliteration rate in patients irradiated with fraction dose ≥ 8 Gy and total dose > 21 Gy for lesions of volume ≤ 8.18 cm³ which was not observed in case of partial obliterations.

Conclusions

HFSRT results with relatively low obliteration rate but is not associated with a significant risk of permanent neurological deficits if both total and fraction doses are adjusted to size and location of the lesion. Predictive factors for total and partial obliterations can be different; this observation, however, is not firmly supported and requires further studies.

Spinal glomus (type II) arteriovenous malformations: a pooled analysis of hemorrhage risk and results of intervention

BACKGROUND

The natural history and treatment results for spinal glomus (type II) arteriovenous malformations (AVMs) remain relatively obscure.

OBJECTIVE

To calculate spinal glomus (type II) AVM hemorrhages rates and amalgamate results of intervention.

METHODS

We performed a pooled analysis via the PubMed database through May 2012, including studies with at least 3 cases. Data on individual patients were extracted and analyzed using a Cox proportional hazards regression model to obtain hazard ratios for hemorrhage risk factors.

RESULTS

The annual hemorrhage rate before treatment was 4% (95% confidence interval [confidence interval]: 3%-6%), increasing to 10% (95% CI: 7%-16%) for AVMs with previous hemorrhage. The hazard ratio for hemorrhage after hemorrhagic presentation was 2.25 (95% CI: 0.71-7.07), increasing to 13.0 within the first 10 years (95% CI: 1.44-118). The overall rates of complete obliteration were 78% (95% CI: 72%-83%) for surgery and 33% (95% CI: 24%-43%) for endovascular treatment. Long-term clinical worsening occurred in 12% of patients after surgical treatment (95% CI: 8%-16%) and in 13% after endovascular treatment (95% CI: 7%-21%). No hemorrhages occurred after complete obliteration. After partial surgical treatment, the annual hemorrhage rate was 3% (95% CI: 1%-6%); no hemorrhages were reported over 196 patient-years after partial endovascular treatment.

CONCLUSION

Spinal glomus (type II) AVMs with previous hemorrhage, particularly within 10 years, demonstrated a greater risk of hemorrhage. Complete obliteration and even partial endovascular treatment significantly decreased their hemorrhage rate.

Multimodality treatment for cerebral arteriovenous malformations: complementary role of proton beam radiotherapy

A total of 29 cerebral arteriovenous malformations (AVMs) treated at the University of Tsukuba with multimodality treatment including proton beam (PB) radiotherapy for cerebral AVMs between 2005 and 2011 were retrospectively evaluated. Eleven AVMs were classified as Spetzler-Martin grades I and II, 10 as grade III, and 8 as grades IV and V. For AVMs smaller than 2.5 cm and located on superficial and non-eloquent areas, surgical removal with/without embolization was offered as a first-line treatment. For some small AVMs located in deep or eloquent lesions, gamma knife (GK) radiosurgery was offered. Some AVMs were treated with only embolization. AVMs larger than 2.5 cm were embolized to achieve reduction in size, to enhance the safety of the surgery, and to render the AVM amenable to GK radiosurgery. For larger AVMs located in deep or eloquent areas, PB radiotherapy was offered with/without embolization. Immediately after the treatment, 24 patients exhibited no neurological worsening. Four patients had moderate disability, and 1 patient had severe disability. Three patients suffered brain damage after surgical resection, and 2 patients suffered embolization complications. However, no neurological worsening was observed after either GK radiosurgery or PB radiotherapy, but 3 patients treated by PB radiotherapy suffered delayed hemorrhage. Fractionated PB radiotherapy for cerebral AVMs seems to be useful for the treatment of large AVMs, but careful long-term follow up is required to establish the efficacy and safety.

Long-term Outcomes After Staged-Volume Stereotactic Radiosurgery for Large Arteriovenous Malformations

BACKGROUND:

Stereotactic radiosurgery is an effective treatment modality for small arteriovenous malformations (AVMs) of the brain. For larger AVMs, the treatment dose is often lowered to reduce potential complications, but this decreases the likelihood of cure. One strategy is to divide large AVMs into smaller anatomic volumes and treat each volume separately.

OBJECTIVE:

To prospectively assess the long-term efficacy and complications associated with staged-volume radiosurgical treatment of large, symptomatic AVMs.

METHODS:

Eighteen patients with AVMs larger than 15 mL underwent prospective staged-volume radiosurgery over a 13-year period. The median AVM volume was 22.9 mL (range, 15.7-50 mL). Separate anatomic volumes were irradiated at 3- to 9-month intervals (median volume, 10.9 mL; range, 5.3-13.4 mL; median marginal dose, 15 Gy; range, 15-17 Gy). The AVM was divided into 2 volumes in 10 patients, 3 volumes in 5 patients, and 4 volumes in 3 patients. Seven patients underwent retreatment for residual disease.

RESULTS:

Actuarial rates of complete angiographic occlusion were 29% and 89% at 5 and 10 years. Five patients (27.8%) had a hemorrhage after radiosurgery. Kaplan-Meier analysis of cumulative hemorrhage rates after treatment were 12%, 18%, 31%, and 31% at 2, 3, 5, and 10 years, respectively. One patient died after a hemorrhage (5.6%).

CONCLUSION:

Staged-volume radiosurgery for AVMs larger than 15 mL is a viable treatment strategy. The long-term occlusion rate is high, whereas the radiation-related complication rate is low. Hemorrhage during the lag period remains the greatest source of morbidity and mortality.

Hypofractionated stereotactic radiotherapy for large arteriovenous malformations

Cerebral arteriovenous malformations (AVMs) are abnormal connections between the arteries and veins, with possible serious consequences of intracranial hemorrhage. The curative treatment for AVMs includes microsurgery and radiosurgery, sometimes with embolization as an adjunct. However, controversies exist with the treatment options available for large to giant AVMs. Hypofractionated stereotactic radiotherapy (HSRT) is one treatment option for such difficult lesions. We aim to review recent literature, looking at the treatment outcome of HSRT in terms of AVM obliteration rate and complications. The rate of AVM obliteration utilizing HSRT as a primary treatment was comparable with that of stereotactic radiosurgery (SRS). For those not totally obliterated, HSRT makes them smaller and turns some lesions manageable by single-dose SRS or microsurgery. Higher doses per fraction seemed to exhibit better response. However, patients receiving higher total dose may be at risk for higher rates of complications. Fractionated regimens of 7 Gy × 4 and 6–6.5 Gy × 5 may be accepted compromises between obliteration and complication. Embolization may not be beneficial prior to HSRT in terms of obliteration rate or the volume reduction. Future work should aim on a prospectively designed study for larger patient groups and long-term follow-up results.

Noncontrast dynamic MRA in intracranial arteriovenous malformation (AVM), comparison with time of flight (TOF) and digital subtraction angiography (DSA)

Digital subtraction angiography (DSA) remains the gold standard to diagnose intracranial arteriovenous malformations (AVMs) but is invasive. Existing magnetic resonance angiography (MRA) is suboptimal for assessing the hemodynamics of AVMs. The objective of this study was to evaluate the clinical utility of a novel noncontrast four-dimensional (4D) dynamic MRA (dMRA) in the evaluation of intracranial AVMs through comparison with DSA and time-of-flight (TOF) MRA. Nineteen patients (12 women, mean age 26.2±10.7 years) with intracranial AVMs were examined with 4D dMRA, TOF and DSA. Spetzler-Martin grading scale was evaluated using each of the above three methods independently by two raters. Diagnostic confidence scores for three components of AVMs (feeding artery, nidus and draining vein) were also rated. Kendall's coefficient of concordance was calculated to evaluate the reliability between two raters within each modality (dMRA, TOF, TOF plus dMRA). The Wilcoxon signed-rank test was applied to compare the diagnostic confidence scores between each pair of the three modalities. dMRA was able to detect 16 out of 19 AVMs, and the ratings of AVM size and location matched those of DSA. The diagnostic confidence scores by dMRA were adequate for nidus (3.5/5), moderate for feeding arteries (2.5/5) and poor for draining veins (1.5/5). The hemodynamic information provided by dMRA improved diagnostic confidence scores by TOF MRA. As a completely noninvasive method, 4D dMRA offers hemodynamic information with a temporal resolution of 50-100 ms for the evaluation of AVMs and can complement existing methods such as DSA and TOF MRA.

Multimodality management of Spetzler-Martin Grade III arteriovenous malformations

OBJECT

Grade III arteriovenous malformations (AVMs) are diverse because of their variations in size (S), location in eloquent cortex (E), and presence of central venous drainage (V). Because they may have implications for management and outcome, the authors evaluated these variations in the present study.

METHODS

Between 1984 and 2010, 100 patients with Grade III AVMs were treated. The AVMs were categorized by Spetzler-Martin characteristics as follows: Type 1 = S1E1V1, Type 2 = S2E1V0, Type 3 = S2E0V1, and Type 4 = S3E0V0. The occurrence of a new neurological deficit, functional status (based on modified Rankin Scale [mRS] score) at discharge and follow-up, and radiological obliteration were correlated with demographic and morphological characteristics.

RESULTS

One hundred patients (49 female and 51 male; age range 5-68 years, mean 35.8 years) were evaluated. The size of AVMs was less than 3 cm in 28 patients, 3-6 cm in 71, and greater than 6 cm in 1; 86 AVMs were located in eloquent cortex and 38 had central drainage. The AVMs were Type 1 in 28 cases, Type 2 in 60, Type 3 in 11, and Type 4 in 1. The authors performed embolization in 77 patients (175 procedures), surgery in 64 patients (74 surgeries), and radiosurgery in 49 patients (44 primary and 5 postoperative). The mortality rate following the management of these AVMs was 1%. Fourteen patients (14%) had new neurological deficits, with 5 (5%) being disabling (mRS score > 2) and 9 (9%) being nondisabling (mRS score ≤ 2) events. Patients with Type 1 AVMs (small size) had the best outcome, with 1 (3.6%) in 28 having a new neurological deficit, compared with 72 patients with larger AVMs, of whom 13 (18.1%) had a new neurological deficit (p < 0.002). Older age (> 40 years), malformation size > 3 cm, and nonhemorrhagic presentation predicted the occurrence of new deficits (p < 0.002). Sex, eloquent cortex, and venous drainage did not confer any benefit. In 89 cases follow-up was adequate for data to be included in the obliteration analysis. The AVM was obliterated in 78 patients (87.6%), 69 of them (88.5%) demonstrated on angiography and 9 on MRI /MR angiography. There was no difference between obliteration rates between different types of AVMs, size, eloquence, and drainage. Age, sex, and clinical presentation also did not predict obliteration.

CONCLUSIONS

Multimodality management of Grade III AVMs results in a high rate of obliteration, which was not influenced by size, venous drainage, or eloquent location. However, the development of new neurological deficits did correlate with size, whereas eloquence and venous drainage did not affect the neurological complication rate. The authors propose subclassifying the Grade III AVMs according to their size (< 3 and ≥ 3 cm) to account for treatment risk.

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.

A historical analysis of single-stage γ knife radiosurgical treatment for large arteriovenous malformations: evolution and outcomes

BACKGROUND

Large arteriovenous malformations (AVMs) remain challenging and difficult to treat, reflected by evolving strategies developed from simple radiosurgical plans, to encompass embolization and, recently, staged volume treatments. To establish a baseline for future practice, we reviewed our clinical experience.

METHOD

The outcomes for 492 patients (564 treatments) with AVMs >10 cm(3) treated by single-stage radiosurgery were retrospectively analysed in terms of planning, previous embolization and size.

RESULTS

Twenty-eight percent of the patients presented with haemorrhage at a median age of 29 years (range: 2-75). From 1986 to 1993 (157 patients) plans were simplistic, based on angiography using a median of 2 isocentres and a marginal dose of 23 Gy covering 45-70% of the AVM (median volume 15.7 cm(3)). From 1994 to 2000 (225 patients) plans became more sophisticated, a median of 5 isocentres was used, covering 64-95% of the AVM (14.6 cm(3)), with a marginal dose of 21 Gy. Since 2000, MRI has been used with angiography to plan for 182 patients. Median isocentres increased to 7 with similar coverage (62-94%) of the AVM (14.3 cm(3)) and marginal dose of 21 Gy. Twenty-seven percent, 30% and 52% of patients achieved obliteration at 4 years, respectively. The proportion of prior embolization increased from 9% to 44% during the study. Excluding the embolized patients, improvement in planning increased obliteration rates from 28% to 36% and finally 63%. Improving treatment plans did not significantly decrease the rate of persisting radiation-induced side effects (12-16.5%). Complication rate rose with increasing size. One hundred and twenty-three patients underwent a second radiosurgical treatment, with a 64% obliteration rate, and mild and rare complications (6%).

CONCLUSIONS

Better visualization of the nidus with multimodality imaging improved obliteration rates without changing morbidity. Our results support the view that prior embolization can make interpretation of the nidus more difficult, reducing obliteration rate. It will be important to see how results of staged volume radiosurgery compare with this historical material.

Management of pediatric intracranial arteriovenous malformations: experience with multimodality therapy

BACKGROUND

Successful management of pediatric arteriovenous malformations (AVMs) often requires a balanced application of embolization, surgery, and radiosurgery.

OBJECTIVE

To describe our experience treating pediatric AVMs.

METHODS

We analyzed 120 pediatric patients (< 18 years of age) with AVMs treated with various combinations of radiosurgery, surgery, and endovascular techniques.

RESULTS

Between 1985 and 2009, 76 children with low Spetzler-Martin grade (1-3) and 44 with high-grade (4-5) AVMs were treated. Annual risk of hemorrhage from presentation to initial treatment was 4.0%, decreasing to 3.2% after treatment initiation until confirmed obliteration. Results for AVM obliteration were available in 101 patients. Initial single-modality therapy led to AVM obliteration in 51 of 67 low-grade (76%) and 3 of 34 high-grade (9%) AVMs, improving to 58 of 67 (87%) and 9 of 34 (26%), respectively, with further treatment. Mean time to obliteration was 1.8 years for low-grade and 6.4 years for high-grade AVMs. Disabling neurological complications occurred in 4 of 77 low-grade (5%) and 12 of 43 high-grade (28%) AVMs. At the final clinical follow-up (mean, 9.2 years), 48 of 67 patients (72%) with low-grade lesions had a modified Rankin Scale score (mRS) of 0 to 1 compared with 12 of 34 patients (35%) with high-grade AVMs. On multivariate analysis, significant risk factors for poor final clinical outcome (mRS ≥ 2) included baseline mRS ≥ 2 (odds ratio, 9.51; 95% confidence interval, 3.31-27.37; P < .01), left-sided location (odds ratio, 3.03; 95% confidence interval, 1.11-8.33; P = .03), and high AVM grade (odds ratio, 4.35; 95% confidence interval, 1.28-14.28; P = .02).

CONCLUSION

Treatment of pediatric AVMs with multimodality therapy can substantially improve obliteration rates and may decrease AVM hemorrhage rates. The poor natural history and risks of intervention must be carefully considered when deciding to treat high-grade pediatric AVMs.

Management of incidentally discovered intracranial vascular abnormalities

With the widespread use of brain imaging studies, neurosurgeons have seen a marked increase in the number of incidental intracranial lesions, including vascular abnormalities. Specifically, the detection of incidentally discovered aneurysms, arteriovenous malformations, cavernous angiomas, developmental venous anomalies, and capillary telangiectasias has increased. The best management strategy for most of these lesions is controversial. Treatment options include observation, open surgery, endovascular procedures, and radiosurgery. Multiple factors should be taken into account when discussing treatment indications, including the natural history of the disease and the risk of the treatment. In this article, the authors focus on the natural history of these lesions and the risk of the treatment, and they give recommendations regarding the most appropriate management strategy based on the current evidence in the literature and their experience with intracranial vascular abnormalities.

Bleeding source identification and treatment in brain arteriovenous malformations

Arteriovenous malformation (AVM) patients who initially present with intracerebral haemorrhage may have an identifiable source of bleeding on angiogram, which can be a treatment target. Previous work suggests that the re-bleed rate may be lowered if a weak area is eliminated.A retrospective cohort study was conducted on patients who presented over a six-year period with a bled AVM. Cases were reviewed looking for the source of the hemorrhage by correlating haematoma location on CT or MRI and any angio-architectural weakness seen on digital subtraction angiography (DSA). Neuroendovascular notes were reviewed to identify the treatment targets. One hundred patients presented with a brain AVM with a 1.7:1 male: female ratio, 41 patients had an initial presentation of hemorrhage. The source of hemorrhage was identified in 18 subjects with 11 intranidal false aneurysms, five flow-related aneurysms, two associated aneurysms and one venous pouch. The location of haemorrhage on the presenting scan significantly correlated with the identified bleeding source using Chi-square analysis (P-value 0.039). Partial targeted embolization was used successfully in 90% with a 9% related technical complication rate not resulting in long-term morbidity or mortality. The mean follow-up period was 34 months with an annual hemorrhage rate of 0.7%. In just under half the patients with AVM bleeding a source of haemorrhage can be identified on DSA and in most cases this will be an intranidal false aneurysm. Flow-related and associated aneurysms in patients with brain AVM can cause haemorrhage and these patients are more likely to have SAH than intracerebral haemorrhage.These weak points are a good target for partial endovascular treatment, are usually accessible and may reduce the higher haemorrhage rate expected over the next two years.

Risk of hemorrhage in patients with untreated Spetzler-Martin grade IV and V arteriovenous malformations: a long-term follow-up study in 63 patients

BACKGROUND

Treatment of Spetzler-Martin Grade IV and V brain arteriovenous malformations (ie, high-grade AVMs) carries a high risk of morbidity and even mortality. However, little is known about the behavior of these lesions if left untreated.

OBJECTIVE

To investigate the natural history of patients with high-grade AVMs.

METHODS

Patients with untreated high-grade AVMs admitted to our center between 1952 and 2005 were followed from admission until death, AVM rupture, or initiation of treatment. Rates of rupture and various risk factors were analyzed using Kaplan-Meier life table analyses and Cox proportional hazards models. Functional outcome was assessed 1 year after possible AVM rupture using the Glasgow Outcome Scale.

RESULTS

Sixty-three patients with a mean follow-up time of 11.0 years (range, 1 month to 39.6 years) were identified. Twenty-three patients (37%) experienced a subsequent rupture. The average annual rate of rupture was 3.3%. In patients with hemorrhagic presentation, the annual rate was 6.0%, compared to 1.1% in patients with unruptured AVMs (P = .001, log-rank test; hazard ratio, 5.09 [1.40-18.5, 95% CI]; P = .013, multivariate Cox regression model). One year after the first subsequent rupture, 6 patients (26%) had died, and 9 (39%) had moderate or severe disability.

CONCLUSION

Untreated high grade AVMs presenting with hemorrhage have a significant risk of subsequent rupture, and their rupture carries a higher risk of case fatality and permanent morbidity than AVMs in general. The risks associated with their treatment should be appraised in light of perilous natural history.

Noncontrast-enhanced four-dimensional MR angiography for the evaluation of cerebral arteriovenous malformation: a preliminary trial

PURPOSE

To prospectively evaluate noncontrast-enhanced (NCE), time resolved, four-dimensional (4D) magnetic resonance angiography (MRA) for assessment of cerebral arteriovenous malformation (AVM), with intraarterial digital subtraction angiography (DSA) performed as the reference standard.

MATERIALS AND METHODS

Fifteen patients (ten men, five women; age range 2-59 years, mean 29.4 years) with 15 untreated cerebral AVMs comprised the study population. NCE 4D MRA was performed on a 3.0 T MR scanner. MR images were reviewed by two independent readers and compared with DSA with respect to arterial feeders, nidus size, and venous drainage. Kappa coefficients of concordance were computed to determine the interobserver and intermodality agreements for the depiction of arterial feeders, nidus, and venous drainage between the two techniques.

RESULTS

Fifteen AVMs detected in DSA were visualized in NCE 4D MRA. Intermodality agreements were excellent for the arterial feeders (K = 0.918, P = 0.000), good for the nidus size (K = 0.692, P = 0.000), and moderate for the venous drainage (K = 0.495, P = 0.001).

CONCLUSION

NCE 4D MRA is a promising and potentially valuable method for noninvasive assessment of angioarchitecture and hemodynamics of cerebral AVMs. Further improvement of labeling persistence is desirable in order to enhance the depiction of draining veins for AVMs.

Surgical treatment of giant intracranial arteriovenous malformations

BACKGROUND

The treatment of giant arteriovenous malformations (AVMs) remains a challenge in the neurosurgical field. Microsurgery is one of the most effective ways for eliminating giant cerebral AVMs.

OBJECTIVE

To review surgical outcomes in treating the disease, and form conclusions regarding the indications for and outcomes of surgical treatment in giant intracranial AVMs.

METHODS

We studied 40 consecutive cases of giant AVMs treated in Beijing Tiantan Hospital between 2000 and 2008. The radiologic and clinical features were analyzed. The Spetzler-Martin grading system was used to classify the patients. All patients were surgically treated, and the final outcomes of the patients were gathered for analysis.

RESULTS

The major presenting symptoms were seizures, headaches, hemorrhage, and neurological deficits. The mean AVM diameter was 6.3 cm. According to the Spetzler-Martin grading system, 5 patients had grade III lesions, 21 had grade IV lesions, and 14 had grade V lesions. Out of the total 40 patients, 31 (77.5%) demonstrated excellent or good outcome. Complications included hemiparalysis, aphasia, hemianopia, cranial nerve dysfunction, and seizures. After follow-up, 27 of 30 (90%) surviving patients presented normal function or minimal symptoms.

CONCLUSION

Presurgical evaluation of every candidate and treatment choice is the determining factor in therapy for giant AVMs. For giant cerebral AVMs located superficially or not involving critical components, a good outcome can be expected through surgical resection. The obliteration and recurrence rates were satisfying, and the complication rate was acceptable.

Endovascular treatment of brain arteriovenous malformations with prolonged intranidal Onyx injection technique: long-term results in 350 consecutive patients with completed endovascular treatment course

OBJECT

The purpose of this study was to present the authors' clinical experience and long-term angiographic and clinical follow-up results in 350 patients with brain arteriovenous malformations (AVMs) treated using prolonged intranidal Onyx injection with a very slow "staged" reflux technique described by the authors.

METHODS

Three hundred and fifty consecutive patients with brain AVMs treated using Onyx between 1999 and 2008 and in whom definitive status for endovascular treatment was reached are presented. There were 206 (59%) male and 144 (41%) female patients, with a mean age of 34 years. There were 607 endovascular sessions performed. Onyx was the only agent used for intranidal injections in all patients, but in 42 patients high-concentration N-butyl cyanoacrylate glue was used adjunctively to close high-flow direct arteriovenous intra- or perinidal fistulas, or when a feeding vessel or nidus perforation and/or dissection occurred.

RESULTS

Angiographically confirmed obliteration was achieved in 179 patients (51%) with only endovascular treatment; 1 patient died due to intracranial hemorrhage after the treatment. Twenty-two patients underwent resection, and 136 patients were sent to radiosurgery after endovascular treatment. In 4 patients embolization therapy was discontinued, and 5 additional patients refused the suggested complementary surgery. In all 178 surviving patients who had angiographically confirmed AVM obliteration by embolization alone, 1-8 years of control angiography (mean 47 months) confirmed stable obliteration, except for 2 patients in whom a very small recruitment was noted in the 1st year on control angiography studies, despite initial apparent total obliteration (recanalization rate 1.1%). In the entire series, 5 patients died; the mortality rate was 1.4%. The permanent morbidity rate was 7.1%.

CONCLUSIONS

With the prolonged intranidal injection technique described herein, Onyx allows the practitioner to achieve higher rates of anatomical cures compared with the cure rates obtained previously with other embolic agents. More importantly, due to this technique's much more effective intranidal penetration, it allows high-grade AVMs to be made radiosurgically treatable in a group of patients for whom there has been no treatment alternative.

A 3-tier classification of cerebral arteriovenous malformations

Object

The authors propose a 3-tier classification for cerebral arteriovenous malformations (AVMs). The classification is based on the original 5-tier Spetzler-Martin grading system, and reflects the treatment paradigm for these lesions. The implications of this modification in the literature are explored.

Methods

Class A combines Grades I and II AVMs, Class B are Grade III AVMs, and Class C combines Grades IV and V AVMs. Recommended management is surgery for Class A AVMs, multimodality treatment for Class B, and observation for Class C, with exceptions to the latter including recurrent hemorrhages and progressive neurological deficits. To evaluate whether combining grades is warranted from the perspective of surgical outcomes, the 3-tier system was applied to 1476 patients from 7 surgical series in which results were stratified according to Spetzler-Martin grades.

Results

Pairwise comparisons of individual Spetzler-Martin grades in the series analyzed showed the fewest significant differences (p < 0.05) in outcomes between Grades I and II AVMs and between Grades IV and V AVMs. In the pooled data analysis, significant differences in outcomes were found between all grades except IV and V (p = 0.38), and the lowest relative risks were found between Grades I and II (1.066) and between Grades IV and V (1.095). Using the pooled data, the predictive accuracies for surgical outcomes of the 5-tier and 3-tier systems were equivalent (receiver operating characteristic curve area 0.711 and 0.713, respectively).

Conclusions

Combining Grades I and II AVMs and combining Grades IV and V AVMs is justified in part because the differences in surgical results between these respective pairs are small. The proposed 3-tier classification of AVMs offers simplification of the Spetzler-Martin system, provides a guide to treatment, and is predictive of outcome. The revised classification not only simplifies treatment recommendations; by placing patients into 3 as opposed to 5 groups, statistical power is markedly increased for series comparisons.

Large vascular malformation in a child presenting with vascular steal phenomenon managed with pial synangiosis

The management of large and giant arteriovenous malformations (AVMs) in patients presenting with nonhemorrhagic neurological deficits secondary to vascular steal phenomenon is challenging and controversial. In many cases, large AVMs cannot be completely excised or cured, leaving patients with residual or partially treated AVMs, the natural history of which is unknown. Additionally, large, diffuse vascular malformations with multiple, small feeders, slow flow, or so-called cerebral proliferative angiopathy represent a related but distinct clinical and angiographic entity that may require a different therapeutic approach than traditional brain AVMs. The current management of children with other conditions of chronic cerebral hypoperfusion, such as moyamoya disease, involves consideration of surgical revascularization to enhance blood flow to the compromised hemisphere. Here, the authors present the case of a young child with a large thalamic vascular malformation who presented with clinical and radiological features of vascular steal and ischemia. In an effort to augment flow to the hypoperfused brain and protect against future ischemia, the authors treated the child with unilateral pial synangiosis. At 12 months, postoperative angiography demonstrated robust neovascularization, and the child has not sustained any further ischemic events. The authors discuss concept of vascular malformation-related hypoperfusion and the utility of indirect revascularization for inoperable vascular malformations presenting with ischemic symptoms.

Treatment of Giant Cerebral Arteriovenous Malformation: Hypofractionated Stereotactic Radiation as the First Stage

BACKGROUND:

Treatment of giant cerebral arteriovenous malformations (AVMs) remains a challenge.

OBJECTIVE:

To propose hypofractionated stereotactic radiotherapy (HSRT) as a part of staged treatment, and evaluate its effect by analyzing AVM volume changes.

METHODS:

From 2001 to 2007, 20 AVMs larger than 5 cm were treated by HSRT and followed up using magnetic resonance imaging. Patients' median age was 34 years (8–61 years). Eleven patients presented with hemorrhage and 9 with seizure. Ten patients had previous embolization and radiosurgery had failed in 4. Thirteen AVMs (65%) were classified as Spetzler-Martin grade V and 7 as grade IV. Median pretreatment volume was 46.84 cm3(12.51-155.38 cm3). Dose was 25 to 30 Gy in 5 to 6 daily fractions. Median follow-up was 32 months.

RESULTS:

Median AVM volume decreased to 13.51 cm3(range, 0.55-147.14 cm3). Residual volume varied from 1.5% to 98%. Volume decreased 44% every year on average. We noted that 6-Gy fractions were more effective (P= .040); embolized AVM tended to respond less (P= .085). After HSRT, we reirradiated 4 AVMs, with 3 amenable to single dose and one with fractions. After HSRT, one patient had an ischemic stroke and one had increased seizure frequency. One AVM bled during follow-up (2.06%/year). No complete obliteration was confirmed.

CONCLUSION:

HSRT can turn some giant AVMs manageable for single-dose radiosurgery. Six-Gray fractions were better than 5-Gy and routine embolization seemed unhelpful. There was no increase in bleeding risk with this approach. Future studies with longer follow-up are necessary to confirm our observation.

Multidisciplinary care of occipital arteriovenous malformations: effect on nonhemorrhagic headache, vision, and outcome in a series of 135 patients

Object

In this study, the authors evaluated how an appropriate allocation of patients with occipital arteriovenous malformations (AVMs) who were treated according to different strategies would affect nonhemorrhagic headache, visual function, and hemorrhage risk levels.

Methods

Of the 712 patients with brain AVMs in the Toronto Western Hospital prospective database, 135 had occipital AVMs. The treatment decision was based on patients' characteristics, presentation, and morphology of the AVM. The management modalities were correlated with their outcomes.

Results

The mean follow-up period was 6.78 years. Nonhemorrhagic headache was the most frequent symptom (82 [61%] of 135 patients). Ninety-four patients underwent treatment with one or a combination of embolization, surgery, or radiosurgery, and 41 were simply observed. Of the 40 nontreated patients with nonhemorrhagic headache, only 12 (30%) showed improvement. In the observation group 2 patients (22%) had worsening of visual symptoms, and 2 experienced hemorrhage, for an annual hemorrhage rate of 0.7% per year; 1 patient died. In the treatment group, the improvement in nonhemorrhagic headache in 35 patients (83%) was significant (p < 0.0001). Visual deficit at presentation worsened in 2 (8%), and there were 8 new visual field deficits (9%). The visual worsening was not significantly different. There were 2 other neurological deficits (2%) and 2 deaths (2%) related to the AVM treatment. One AVM hemorrhaged. The annual hemorrhage rate was 0.1% per year. The hemorrhage risk in the observation and treatment groups was lower than the observed hemorrhage risk of all patients with AVMs (4.6%) at the authors' institution.

Conclusions

Appropriate selection of patients with occipital AVMs for one or a combination of treatment modalities yields a significant decrease in nonhemorrhagic headache without significant visual worsening. The multidisciplinary care of occipital AVMs can aim for an apparent decrease in hemorrhage risk.

To glue or not to glue? That is the question!!!

The purpose of Clinical Problem Solving manuscripts is to present management challenges in an attempt to give practicing neurosurgeons insight into how field leaders address these dilemmas. This illustration is accompanied by a brief review of the literature on the topic. We describe the case of a patient who presented with recurrent headaches resulting from a nondominant hemisphere parietal arteriovenous malformation. Challenges in prognosis, treatment, and complication management are discussed.

Comparison of 2 approaches for determining the natural history risk of brain arteriovenous malformation rupture

Estimating risk of intracranial hemorrhage (ICH) for patients with unruptured brain arteriovenous malformations (AVMs) in the natural course is essential for assessing risks and benefits of treatment. Traditionally, the survival period starts at the time of diagnosis and ends at ICH, but most patients are quickly censored because of treatment. Alternatively, a survival period from birth to first ICH, censoring at the date of diagnosis, has been proposed. The authors quantitatively compared these 2 timelines using survival analysis in 1,581 Northern California brain AVM patients (2000-2007). Time-shift analysis of the birth-to-diagnosis timeline and maximum pseudolikelihood identified the point at which the 2 survival curves overlapped; the 95% confidence interval was determined using bootstrapping. Annual ICH rates per 100 patient-years were similar for both the birth-to-diagnosis (1.27, 95% confidence interval (CI): 1.18, 1.36) and the diagnosis-to-ICH (1.17, 95% CI: 0.89, 1.53) timelines, despite differences in curve morphology. Shifting the birth-to-diagnosis timeline an optimal amount (10.3 years, 95% CI: 3.3, 17.4) resulted in similar ICH survival curves (P = 0.979). These results suggest that the unconventional birth-to-diagnosis approach can be used to analyze risk factors for natural history risk in unruptured brain AVM patients, providing greater statistical power. The data also suggest a biologic change around age 10 years influencing ICH rate.

Assessment of cerebral arteriovenous malformations with high temporal and spatial resolution contrast-enhanced magnetic resonance angiography: a review from protocol to clinical application

The combination of high spatial and high temporal resolution contrast-enhanced magnetic resonance angiography (MRA) at 3.0 T has enabled the detailed evaluation of functional vascular anatomy and hemodynamics of cerebral arteriovenous malformations (AVMs). Key contributory technical factors for the successful implementation of MRA in patients with different vascular pathologies are multicoil and multichannel receiver arrays, which enable higher parallel acquisition at 3.0 T over a uniform and a large field of view for highly temporally and spatially resolved MRA. Magnetic resonance angiography enables both screening of patients with suspected AVMs and follow-up of patients after therapy. It allows the characterization of AVMs with respect to nidus configuration, size, venous drainage, and so on, according to the Spetzler-Martin classification.

Challenging traditional beliefs: microsurgery for arteriovenous malformations of the basal ganglia and thalamus

OBJECTIVE

Arteriovenous malformations of the basal ganglia and thalamus are often managed with radiosurgery or observation, without consideration of microsurgery. Given the devastating effects of hemorrhage from these lesions, the accumulating evidence that they bleed more frequently than their lobar counterparts should prompt more creative thinking regarding their management.

METHODS

A review of the endovascular, microsurgical, and radiosurgical literature for arteriovenous malformations of the basal ganglia and thalamus was performed, with close attention to surgical approaches, obliteration rates, and procedure-related complications.

RESULTS

A complete resection rate of 91% and a mortality rate of 2.4% were found across surgical series of these lesions. These contrast with a 69% rate of complete obliteration and a 5.3% mortality rate (from latency-period hemorrhage) found when compiling results across the radiosurgical literature.

CONCLUSION

Given an appropriate surgical corridor of access, often afforded by incident hemorrhage, arteriovenous malformations of the basal ganglia and thalamus should be considered for microsurgical extirpation with preoperative embolization. In experienced hands, this approach presents an expeditious and definitive opportunity to eliminate the risk of subsequent hemorrhage and resultant morbidity and mortality.

Long-term excess mortality in 623 patients with brain arteriovenous malformations

OBJECTIVE

Long-term follow-up studies in patients with brain arteriovenous malformations (AVM) have been scarce and without proper statistical estimates of mortality. We performed a retrospective survival study in 623 consecutive patients with AVMs admitted to the Department of Neurosurgery in Helsinki University Hospital between 1951 and 2005.

METHODS

Patients were followed from admission until death or the end of 2005. Patient survival was estimated using the relative survival ratio, which provides a measure of the excess mortality experienced by the patients compared with the general Finnish population matched by age, sex, and calendar time.

RESULTS

Median follow-up was 11.9 years, and total follow-up was 10,165 person-years. Treatment was conservative in 155 patients. Total AVM occlusion was attained in 356 patients, and partial occlusion was obtained in 94 patients. Overall, 206 deaths were observed. Of these, 100 were related to AVMs. Diagnosis of AVM was associated with significant long-term excess mortality, with cumulative relative survival ratios of 0.85 (95% confidence interval, 0.81-0.88) and 0.69 (95% confidence interval, 0.62-0.75) at 10 and 30 years after admission, respectively. Men had higher excess mortality than women. The excess in mortality was highest in conservatively treated patients, intermediate in patients with partially occluded AVMs, and lowest in those with totally occluded AVMs. The subgroup with the best outcome consisted of those with totally occluded unruptured AVMs, which did not demonstrate excess mortality after the first year.

CONCLUSION

AVMs are associated with long-term excess mortality that may be reduced by active, even partial, treatment. Male patients have a higher excess mortality rate than female patients.

Radiosurgery for large cerebral arteriovenous malformations

BACKGROUND

Radiosurgery is an effective treatment option for patients with small to medium sized arteriovenous malformations. However, it is not generally accepted as an effective tool for larger (>14 cm(3)) arteriovenous malformations because of low obliteration rates. The authors assessed the applicability and effectiveness of radiosurgery for large arteriovenous malformations.

METHOD

We performed a retrospective study of 46 consecutive patients with more than 14 ml of arteriovenous malformations who were treated with radiosurgery using a linear accelerator and gamma knife (GK). They were grouped according to their initial clinical presentation-17 presented with and 29 without haemorrhage. To assess the effect of embolization, these 46 patients were also regrouped into two subgroups-25 with and 21 without preradiosurgical embolization. Arteriovenous malformations found to have been incompletely obliterated after 3-year follow-up neuroimaging studies were re-treated using a GK.

FINDINGS

The mean treatment volume was 29.5 ml (range, 14.0-65.0) and the mean marginal dose was 14.1 Gy (range, 10.0-20.0). The mean clinical follow-up periods after initial radiosurgery was 78.1 months (range, 34.0-166.4). Depending on the results of the angiography, 11 of 33 patients after the first radiosurgery and three of four patients after the second radiosurgery showed complete obliteration. Twenty patients received the second radiosurgery and their mean volume was significantly smaller than their initial volume (P = 0.017). The annual haemorrhage rate after radiosurgery was 2.9% in the haemorrhage group (mean follow-up 73.3 months) and 3.1% in the nonhaemorrhage group (mean follow-up 66.5 months) (P = 0.941). Preradiosurgical embolization increased the risk of haemorrhage for the nonhaemorrhage group (HR, 28.03; 95% CI, 1.08-6,759.64; P = 0.039), whereas it had no effect on the haemorrhage group. Latency period haemorrhage occurred in eight patients in the embolization group, but in no patient in the nonembolization group (P = 0.004).

CONCLUSIONS

Radiosurgery may be a safe and effective arteriovenous malformation treatment method that is worth considering as an alternative treatment option for a large arteriovenous malformation.

Retrospective analysis of unstaged and staged Gamma Knife surgery with and without preceding embolization for the treatment of arteriovenous malformations

Object

The authors conducted a retrospective study to examine data on rates of obliteration of arteriovenous malformations (AVMs) with use of various combinations of treatment modalities based on Gamma Knife surgery (GKS). The authors believe that this study is the first to report on patients treated with embolization followed by staged GKS.

Methods

The authors identified 150 patients who underwent GKS for treatment of AVMs between 1994 and 2004. In a retrospective study, 4 independent groups emerged based on the various combinations of treatment: 92 patients who underwent unstaged GKS, 28 patients who underwent embolization followed by unstaged GKS, 23 patients who underwent staged GKS, and 7 patients who underwent embolization followed by staged GKS. A minimum of 3 years of follow-up after the last GKS treatment was required for inclusion in the retrospective analysis. Angiograms, MR images, or CT scans at follow-up were required for calculating rates of obliteration of AVMs.

Results

Fifty-seven of 150 patients (38%) supplied angiograms, and overall obliteration was confirmed in 43 of these 57 patients (75.4%). An additional 37 patients had follow-up MR images or CT scans. The overall obliteration rate, including patients with follow-up angiograms and patients with follow-up MR images or CT scans, was 68 of 94 (72.3%). Patients who underwent unstaged GKS had a follow-up rate of 58.7% (54 of 92) and an obliteration rate of 75.9% (41 of 54). Patients who underwent embolization followed by unstaged GKS had a follow-up rate of 53.5% (15 of 28) and an obliteration rate of 60.0% (9 of 15). Patients who underwent staged GKS had a follow-up rate of 82.6% (19 of 23) and an obliteration rate of 73.7% (14 of 19). Patients who underwent embolization followed by staged GKS had a follow-up rate of 85.7% (6 of 7) and an obliteration rate of 66.7% (4 of 6).

Conclusions

Gamma Knife surgery is an effective means of treating AVMs. Embolization prior to GKS may reduce AVM obliteration rates. Staged GKS is a promising method for obtaining high obliteration rates when treating larger AVMs in eloquent locations.

Surgery of cerebral arteriovenous malformations

Despite remarkable progress, the microsurgical extirpation of cerebral arteriovenous malformations (AVMs) even by experienced neurosurgeons is not always easy or safe. This article focuses on how to render AVM surgery safer, and offers strategies and tactics for avoiding perilous bleeding and preserving postoperative neurological function. Our treatment strategies and surgical techniques are offered from the operating surgeon's perspective. An understanding of pathophysiology of cerebral AVMs is important for their appropriate surgical treatment. Sophisticated neuroimaging techniques and scrupulous neurophysiological examinations alert to possible complications, and improved surgical approaches help to minimize the sequelae of unanticipated complications. At the early stage of cerebral AVM surgery, extensive dissection of the sulci, fissures, and subarachnoid cistern should be performed to expose feeders, nidus, and drainers. Problems with the surgery of large and/or deep-seated lesions are exacerbated when arterial bleeding from the nidus continues even after all major feeders are thought to have been occluded. We routinely place catheters for angiography at the surgery of complex AVMs to find missing feeding arteries or to identify the real-time hemodynamic status of the lesion. Temporary clip application on feeders and less coagulation of the nidus is necessary to control intranidal pressure and to avoid uncontrollable bleeding from the nidus and adjacent brain. Intraoperative navigation images superimposed on tractography images can provide us with valuable information to minimize neurological deficits. Deeper insight into AVM nature and into events that occur during AVM surgery as well as the inclusion of molecular biological approaches will open new horizons for the safe and effective treatment of AVMs.