Effect of Gamma Knife surgery on the risk of rupture prior to AVM obliteration

Vascular compactness of unruptured brain arteriovenous malformation predicts risk of hemorrhage after stereotactic radiosurgery

The aim of the study was to investigate whether morphology (i.e. compact/diffuse) of brain arteriovenous malformations (bAVMs) correlates with the incidence of hemorrhagic events in patients receiving Stereotactic Radiosurgery (SRS) for unruptured bAVMs. This retrospective study included 262 adult patients with unruptured bAVMs who underwent upfront SRS. Hemorrhagic events were defined as evidence of blood on CT or MRI. The morphology of bAVMs was evaluated using automated segmentation which calculated the proportion of vessel, brain tissue, and cerebrospinal fluid in bAVMs on T2-weighted MRI. Compactness index, defined as the ratio of vessel to brain tissue, categorized bAVMs into compact and diffuse types based on the optimal cutoff. Cox proportional hazard model was used to identify the independent factors for post-SRS hemorrhage. The median clinical follow-ups was 62.1 months. Post-SRS hemorrhage occurred in 13 (5.0%) patients and one of them had two bleeds, resulting in an annual bleeding rate of 0.8%. Multivariable analysis revealed bAVM morphology (compact versus diffuse), bAVM volume, and prescribed margin dose were significant predictors. The post-SRS hemorrhage rate increased with larger bAVM volume only among the diffuse nidi (1.7 versus 14.9 versus 30.6 hemorrhage per 1000 person-years in bAVM volume < 20 cm3 versus 20-40 cm3 versus > 40 cm3; p = 0.022). The significantly higher post-SRS hemorrhage rate of Spetzler-Martin grade IV-V compared with grade I-III bAVMs (20.0 versus 3.3 hemorrhages per 1000 person-years; p = 0.001) mainly originated from the diffuse bAVMs rather than the compact subgroup (30.9 versus 4.8 hemorrhages per 1000 person-years; p = 0.035). Compact and smaller bAVMs, with higher prescribed margin dose harbor lower risks of post-SRS hemorrhage. The post-SRS hemorrhage rate exceeded 2.2% annually within the diffuse and large (> 40 cm3) bAVMs and the diffuse Spetzler-Martin IV-V bAVMs. These findings may help guide patient selection of SRS for the unruptured bAVMs.

Risk for Hemorrhage the First 2 Years After Gamma Knife Surgery for Arteriovenous Malformations: An Update

BACKGROUND

Knowledge about the natural course of brain arteriovenous malformations (AVMs) have increased during the past 20 years, as has the number of AVMs treated, especially larger ones. It is thus timely to again analyze the risk for hemorrhage after Gamma Knife Surgery (GKS).

OBJECTIVE

To confirm or contradict conclusions drawn 20 years ago regarding factors that affect the risk for post-GKS hemorrhage.

METHODS

The outcome after GKS was studied in 5037 AVM patients followed for up to 2 years. The relation between post-treatment hemorrhage rate and a number of patient, AVM, and treatment parameters was analyzed. The results were also compared with the results from our earlier study.

RESULTS

The annual post-treatment hemorrhage rate was 2.4% the first 2 years after GKS. Large size, low treatment dose, and old age were independent risk factors for AVM hemorrhage. After having compensated for the factors above, peripheral AVM location and female sex, at least during their child bearing ages, were factors associated with a lower post-GKS hemorrhage rate.

CONCLUSION

Large AVMs (>5 cm 3 ) treated with low doses (≤16 Gy) had higher and small AVMs treated with high doses a lower risk for hemorrhage as compared with untreated AVMs. This was detectable within the first 6 months after GKS. No difference in hemorrhage rate could be detected for the other AVMs. Based on our findings, it is advisable to prescribe >16 Gy to larger AVMs, assuming that the risk for radiation-induced complications can be kept at an acceptable level.

Multidisciplinary Approach to Suspected Sudden Death Caused by Arteriovenous Malformation Rupture: A Case Report

Arteriovenous malformations (AVMs) are rare congenital conditions with a prevalence of less than 1% and are mostly asymptomatic. However, these malformations can suddenly cause intense pain or bleeding, leading to life-threatening medical problems. This report presents a case of an unexpected death in a 37-year-old previously healthy woman due to an intra-cerebellum arteriovenous malformation rupture identified during autopsy. While infective processes where preliminarily excluded, a Post Mortem Computed Tomography (PMCT) identified a tetra ventricular hemorrhage and intra-cerebellum hemorrhage. Toxicological examination was negative for most substances of abuse. During autopsy an intense hemorrhagic infiltrate in the subarachnoid space was observed. After formalin fixation of the brain the cerebellum showed hemorrhagic infarction on fourth ventricle sides, as well as several small reddish infarctions across the entire cerebellum parenchyma. Histological examination of the brain and cerebellum showed a suffusion of erythrocytes in the sub-arachnoid region. Evidence of an arterio-venous malformation, with several intertwine vessels of variable diameter, surrounded by hemorrhagic evidence. The autopsy played a crucial role in identifying the location and the possibly affected vessel, as well as defining the cause of death. It is necessary to have a greater number of autopsies to make an epidemiological contribution. Furthermore, it is crucial to create a multicenter data network with other authors from other departments to improve information about epidemiological, clinical, diagnostic and therapeutic data. Most brain AVMs as cause of death are often undiscovered.

Clinical outcome following cerebral AVM hemorrhage

BACKGROUND

A significant difference exists between the published results reporting the clinical outcome following brain arteriovenous malformation (AVM) ruptures. Information about the outcome following hemorrhage in an AVM population treated with radiosurgery could provide additional information to assess the risk of mortality and morbidity following an AVM hemorrhage.

METHODS

Clinical outcome was studied in 383 patients, the largest patient population yet studied, who suffered from a symptomatic hemorrhage after Gamma Knife® surgery (GKS) but before confirmed AVM obliteration. The impact of different patient, AVM, and treatment parameters on the clinical outcome was analyzed. The aim was to generate outcome predictions by comparing our data to and combining them with earlier published results.

RESULTS

No relation was found between clinical outcome and treatment parameters, indicating that the results are applicable also on untreated AVMs. Twenty-one percent of the patients died, 45% developed or experienced worsening of neurological sequelae, and 35% recovered completely after the hemorrhage. Old age was a predictor of poor outcome. Sex, AVM location, AVM volume, and history of prior hemorrhage did not influence the outcome. The mortality rate was comparable to earlier published prospective data, but higher than that found in retrospective studies.

CONCLUSIONS

The mortality rates in earlier published retrospective series as well as in studies focusing on clinical outcome following AVM hemorrhage significantly underestimate the risk for a mortal outcome following an AVM hemorrhage. Based on our findings, an AVM rupture has around 20% likelihood to result in mortality, 45% likelihood to result in a minor or major deficit, and 35% likelihood of complete recovery. The findings are probably applicable also for AVM ruptures in general. The cumulative mortality and morbidity rates 25 years after diagnosis were estimated to be around 40% in a patient with a patent AVM.

Volume-Staged Stereotactic Radiosurgery for Intracranial Arteriovenous Malformations: Outcomes Based on an 18-Year Experience

BACKGROUND

Radiation-based treatment options of large intracranial arteriovenous malformations (AVM) must balance the likelihood of obliteration with the risk of adverse radiation effects (ARE).

OBJECTIVE

To analyze the efficacy and risks of volume-staged stereotactic radiosurgery (VS-SRS) for AVM.

METHODS

Retrospective study of 34 AVM patients having VS-SRS between 1997 and 2012. A median of 2 stages (range, 2-4) was used to treat a median AVM volume of 22.2 cm 3 (range, 7.4-56.7). The median AVM margin dose was 16 Gy (range, 14-18); the median radiosurgery-based AVM score was 2.81 (range, 1.54-6.45). The median follow-up after VS-SRS was 8.2 years (range, 3-13.3).

RESULTS

Nidus obliteration was noted in 18 patients (53%) after VS-SRS. The rate of obliteration was 14% at 3 years, 54% at 5 years, and 75% at 7 years. Six patients (18%) had 11 bleeds after VS-SRS. Two patients (6%) remained neurologically stable, 2 (6%) patients had significant deficits, and 2 patients (6%) died. The actuarial risk of a first bleed after VS-SRS was 6% at 1 year, 12% at 3 years, and 19% at 7 years. Six patients (18%) underwent repeat SRS; all achieved nidus obliteration for an overall cure rate of 71%. Two patients (6%) had a permanent ARE after VS-SRS or repeat SRS.

CONCLUSION

VS-SRS permitted large volume intracranial AVM to be treated with a low rate of ARE. Further study is needed on dose escalation and decreasing the treatment volume per stage to determine if this will increase the rate of obliteration with this technique.

Radiosurgery in treatment of cerebral arteriovenous malformation: Mid-term results of 388 cases from a single center

Background and Objectives:

The purpose of this study is to evaluate the outcome and risks of radiosurgery for patients with arteriovenous malformations (AVM) of the brain all treated in a single center in the 3^rd world with all its limitations.

Materials and Methods:

We performed a retrospective analysis of 388 patients with AVM treated with radiosurgery during an 8-year period. Factors associated with increased chance of AVM obliteration or hemorrhages during the follow-up period were analyzed.

Results:

Among 388 cases included in our series, 74 were Spetzler-Martin (SM) grade IV or V. Forty-four patients (11.3%) experienced post-radiosurgery hemorrhage in their follow-up period. The number of feeders (one/multiple) and deep location of the AVM did not alter the chance of bleeding (P < 0.05). Higher SM grading of the AVM was associated with increased chance of hemorrhage and decreased obliteration rate (P > 0.05) in the mid-term follow up.

Conclusions:

Our case series showed that radiosurgery can be considered a viable alternative in the treatment of even large AVMs which might not be considered good candidates for surgery or endovascular treatment. Further data including large size lesions are warranted to further support our findings.

Linear Accelerator Stereotactic Radiosurgery of Central Nervous System Arteriovenous Malformations: A 15-Year Analysis of Outcome-Related Factors in a Single Tertiary Center

BACKGROUND

Linear accelerator stereotactic radiosurgery is one of the modalities available for the treatment of central nervous system arteriovenous malformations (AVMs). The aim of this study was to describe our 15-year experience with this technique in a single tertiary center and the analysis of outcome-related factors.

METHODS

From 1998 to 2013, 195 patients were treated with linear accelerator-based radiosurgery; we conducted a retrospective study collecting patient- and AVM-related variables. Treatment outcomes were obliteration, posttreatment hemorrhage, symptomatic radiation-induced changes, and 3-year neurologic status. We also analyzed prognostic factors of each outcome and predictability analysis of 5 scales: Spetzler-Martin grade, Lawton-Young supplementary and Lawton combined scores, radiosurgery-based AVM score, Virginia Radiosurgery AVM Scale, and Heidelberg score.

RESULTS

Overall obliteration rate was 81%. Nidus diameter and venous drainage were predictive of obliteration (P < 0.05), ruptured status and previous embolization were not related to rate of obliteration, and low-grade AVMs had higher obliteration rates. Posttreatment hemorrhage incidence was 8.72%; nidus diameter was the only predictor (P = 0.05). Symptomatic radiation-induced changes occurred in 11.79% of patients and were significantly associated with unruptured status (P < 0.05). Treatment success as a composite measure was obtained in 70.77% of patients. Receiver operating characteristic curves were presented for each scoring system and outcome measure; best area under the curve was 0.687 for Lawton combined score in the obliteration outcome.

CONCLUSIONS

In the long-term, linear accelerator-based radiosurgery is a useful, valid, effective, and safe modality for treatment of brain AVMs.

Predictors for occlusion of cerebral AVMs following radiation therapy : Radiation dose and prior embolization, but not Spetzler-Martin grade

BACKGROUND

Intracranial arteriovenous malformations (AVMs) may show a harmful development. AVMs are treated by surgery, embolization, or radiation therapy.

OBJECTIVE

This study investigated obliteration rates and side effects in patients with AVMs treated by radiation therapy.

METHODS

A total of 40 cases treated between 2005 and 2013 were analyzed. Single-dose stereotactic radiosurgery (SRS) was received by 13 patients and 27 received hypofractionated stereotactic radiation therapy (HSRT). In 20 patients, endovascular embolization had been performed prior to irradiation and 24 patients (60 %) had a history of previous intracranial hemorrhage.

RESULTS

Treatment resulted in complete obliteration (CO) in 23/40 cases and partial obliteration in 8/40. CO was achieved in 85 % of patients receiving SRS compared to 44 % of those receiving HSRT. In the HSRT group, a first indication of an influence of AVM volume on obliteration rate was found. Equivalent 2 Gy fraction doses (EQD2) >70 Gy showed an obliteration rate of 50 %. Prior embolization was significantly associated with a higher portion of CO (p = 0.032). Median latency period (24.2 vs. 26 months) until CO was similar in both groups (SRS vs. HSRT). The rate of intracranial hemorrhage in patients with no prior bleeding events was 0 %.

CONCLUSION

Excellent obliteration rates were achieved by SRS. Consistent with the literature, this data analysis suggests that the results of HSRT are volume-dependent. Furthermore, regimens with EQD2 doses >70 Gy appear more likely to achieve obliteration than schemes with lower doses. The findings indicate that radiation therapy does not increase the risk of bleeding. Prior embolization may have a good prognostic impact.

Gamma Knife surgical treatment for partially embolized cerebral arteriovenous malformations

OBJECTIVE

A combination of embolization and radiosurgery is used as a common strategy for the treatment of large and complex cerebral arteriovenous malformations (AVMs). This study presents the experiences of partially embolized cerebral AVMs followed by Gamma Knife surgery (GKS) and assesses predictive factors for AVM obliteration and hemorrhage.

METHODS

The interventional neuroradiology database that was reviewed included 404 patients who underwent AVM embolization. Using this database, the authors retrospectively analyzed all partially embolized AVM cases followed by GKS for a residual nidus. Except for cases of complete AVM obliteration, the authors excluded all patients with radiological follow-up of less than 2 years. Logistic regression analysis was used to analyze the predictive factors related to AVM obliteration and hemorrhage following GKS. Kaplan-Meier analysis was used to evaluate the obliteration with a cutoff AVM nidus volume of 3 cm(3) and 10 cm(3).

RESULTS

One hundred sixty-two patients qualified for the study. The median patient age was 26 years and 48.8% were female. Hemorrhage presented as the most common symptom (48.1%). The median preembolization volume of an AVM was 14.3 cm(3). The median volume and margin dose for GKS were 10.92 cm(3) and 16.0 Gy, respectively. The median radiological and clinical follow-up intervals were 47 and 79 months, respectively. The annual hemorrhage rate was 1.71% and total obliteration rate was 56.8%. Noneloquent area (p = 0.004), superficial location (p < 0.001), decreased volume (p < 0.001), lower Spetzler-Martin grade (p < 0.001), lower Virginia Radiosurgery AVM Scale (RAS; p < 0.001), lower Pollock-Flickinger score (p < 0.001), lower modified Pollock-Flickinger score (p < 0.001), increased maximum dose (p < 0.001), and increased margin dose (p < 0.001) were found to be statistically significant in predicting the probability of AVM obliteration in the univariate analysis. In the multivariate analysis, only volume (p = 0.016) was found to be an independent prognostic factor for AVM obliteration. The log-rank (Mantel-Cox) test of the Kaplan-Meier analysis (chi-square = 54.402, p < 0.001) showed a significantly decreased obliteration rate of different cutoff AVM volume groups of less than 3 cm(3), 3-10 cm(3), and more than 10 cm(3). No independent prognostic factor was found for AVM hemorrhage in multivariate analysis.

CONCLUSIONS

Partially embolized AVMs are amenable to successful treatment with GKS. The volume of the nidus significantly influences the outcome of radiosurgical treatment. The Virginia RAS and Pollock-Flickinger score were found to be reliable scoring systems for selection of patient candidates and prediction of partially embolized AVM closure and complications for GKS.

Stereotactic Radiosurgery for Arteriovenous Malformations

BACKGROUND:

Stereotactic radiosurgery (SRS) has been performed on patients with cerebral arteriovenous malformations (AVMs) for over 40 years.

OBJECTIVE:

To evaluate the impact of treatment period on obliteration, intracranial hemorrhage (ICH), and radiation-induced complications (RICs).

METHODS:

Retrospective comparison of 381 AVM patients having SRS during a 20-year period (group 1, January 1990 through March 1997, n = 160; group 2, April 1997 through December 2009, n = 221). The median radiological and clinical follow-up after initial SRS was 77 months and 93 months, respectively.

RESULTS:

Obliteration was 59.1% at 4 years and 85.1% at 8 years. Obliteration was more common in patients with hemispheric or cerebellar AVMs (P = .001), smaller prescription isodose volume (PIV) (P &lt; .001), and group 1 patients (P &lt; .001). The ICH rate was 7.7% at 4 years and 10.6% at 8 years. ICH was more common in older patients (P = .02), patients with deep AVM (P = .01), and larger PIV (P &lt; .001). There was no difference in the ICH rate between the treatment groups (P = .18). The rate of permanent RICs was 4.4% at 4 years and 8.6% at 8 years. RICs were more common with larger PIVs (P &lt; .001) and group 1 patients (P = .02). There was no difference in the number of patients having obliteration without new deficits between the 2 treatment periods (68.8% vs 73.3%, P = .33).

CONCLUSION:

Advances in SRS procedures over the past 20 years have resulted in a lower risk of RIC, but fewer patients had AVM obliteration. Increasing the prescription dose for patients with medium- and large-volume AVMs by using current conformal dose-planning techniques may improve the obliteration rate while maintaining a low risk of RICs.

Volume-staged versus dose-staged radiosurgery outcomes for large intracranial arteriovenous malformations

OBJECT

The aim in this paper was to compare the outcomes of dose-staged and volume-staged stereotactic radio-surgery (SRS) in the treatment of large (> 10 cm(3)) arteriovenous malformations (AVMs).

METHODS

A systematic literature review was performed using PubMed. Studies written in the English language with at least 5 patients harboring large (> 10 cm(3)) AVMs treated with dose- or volume-staged SRS that reported post-treatment outcomes data were selected for review. Demographic information, radiosurgical treatment parameters, and post-SRS outcomes and complications were analyzed for each of these studies.

RESULTS

The mean complete obliteration rates for the dose- and volume-staged groups were 22.8% and 47.5%, respectively. Complete obliteration was demonstrated in 30 of 161 (18.6%) and 59 of 120 (49.2%) patients in the dose- and volume-staged groups, respectively. The mean rates of symptomatic radiation-induced changes were 13.5% and 13.6% in dose- and volume-staged groups, respectively. The mean rates of cumulative post-SRS latency period hemorrhage were 12.3% and 17.8% in the dose- and volume-staged groups, respectively. The mean rates of post-SRS mortality were 3.2% and 4.6% in dose- and volume-staged groups, respectively.

CONCLUSIONS

Volume-staged SRS affords higher obliteration rates and similar complication rates compared with dose-staged SRS. Thus, volume-staged SRS may be a superior approach for large AVMs that are not amenable to single-session SRS. Staged radiosurgery should be considered as an efficacious component of multimodality AVM management.

Radiosurgical Retreatment for Brain Arteriovenous Malformation

Objective:

To analyze our experience with a second radiosurgical treatment for brain arteriovenous malformations (BAVMs) after an unsuccessful first radiosurgical treatment.

Methods:

Between 1993 and 2000, 242 patients were treated by the Toronto Sunnybrook Regional Cancer Center using a LINAC system. Fifteen of these patients required a second radiosurgical intervention due to the failure of the first procedure. Data was collected on baseline patient characteristics, BAVM features, radiosurgery treatment plan and outcomes. Brain arteriovenous malformation obliteration was determined by follow-up MRI and angiography and the obliteration prediction index (OPI) calculated according to a previously established formula.

Results:

The median interval between the first and second treatment was 46 months (range 39-109). The median follow-up after the second procedure was 39 months (range 26 to 72). The mean BAVM volume before the first treatment was 8.9cm3 (range 0.3-21) and before the second treatment was 3.6cm3 (range 0.2-11.6). The mean marginal dose during the first treatment was 18Gy (range 12-25) and during the second treatment was 16Gy (range 12-20). After the second treatment, nine patients had obliteration of their BAVM confirmed by angiography and one patient had obliteration confirmed by MRI, resulting in an obliteration rate of 66.6%, which is very comparable to that predicted by the OPI (65%). After the second treatment two patients had a radiation-induced complication (13.3%).

Conclusion:

Retreatment of BAVM using a second radiosurgery procedure is a safe and effective option that offers the same rate of success as the initial radiosurgery and an acceptable risk of radiation-induced complication.

Evaluation of prognostic factors as predictor of AVMS obliteration after Gamma Knife radiosurgery

BACKGROUND

The reported AVMs obliteration rate after Gamma Knife radiosurgery (GKS) ranges from 70 to 94 %. The objective of the present study was to assess prognostic factors predictive for cerebral AVMs obliteration in 127 patients who underwent GKS.

METHODS

The AVMs were classified according to the Spetzler-Martin classification. Twenty-one cases (16.5 %) were classified as grade I, 46 cases (36.2 %) as grade II, 51 cases (40.1 %) as grade III, and nine cases (7.1 %) as grade IV-V. The AVMs were deeply located in 16.5 % of patients. The peripheral prescription dose ranged from 16 to 30 Gy (mean 22.3 Gy). The AVMs volume ranged from 0.1 to 13 cc (mean 2.7 cc).

RESULTS

In 72 patients out of the 104 (69.2 %) with a radiological follow-up, MRI showed the AVM obliteration; in 54 cases (60 %) out of the 90 that performed a DSA, a complete AVM obliteration was achieved (average closure time 48.5 months). The volume of the nidus (p = 0.001), the prescription dose (p = 0.004), the 2002 Pollock-Flickinger classification (p = 0.031), and their 2008 revised classification (p = 0.025) were found to be statistically significant in predicting the probability of AVM closure. In the multivariate analysis, only the prescription dose was found to be an independent prognostic factor (p = 0.009) for AVM obliteration.

CONCLUSIONS

The volume of the nidus and the prescription dose significantly influence the outcome of radiosurgical treatment. The Pollock-Flickinger classification was found to be a reliable scoring system in predicting the AVM closure and an important tool for selection of patients candidate for GKS.

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.

Gamma Knife surgery for basal ganglia and thalamic arteriovenous malformations

Object

Gamma Knife surgery (GKS) has emerged as the treatment of choice for small- to medium-sized cerebral arteriovenous malformations (AVMs) in deep locations. The present study aims to investigate the outcomes of GKS for AVMs in the basal ganglia and thalamus.

Methods

Between 1989 and 2007, 85 patients with AVMs in the basal ganglia and 97 in the thalamus underwent GKS and were followed up for more than 2 years. The nidus volumes ranged from 0.1 to 29.4 cm3 (mean 3.4 cm3). The mean margin dose at the initial GKS was 21.3 Gy (range 10–28 Gy). Thirty-six patients underwent repeat GKS for residual AVMs at a median 4 years after initial GKS. The mean margin dose at repeat GKS was 21.1 Gy (range 7.5–27 Gy).

Results

Following a single GKS, total obliteration of the nidus was confirmed on angiograms in 91 patients (50%). In 12 patients (6.6%) a subtotal obliteration was achieved. No flow voids were observed on MR imaging in 14 patients (7.7%). Following single or repeat GKS, total obliteration was angiographically confirmed in 106 patients (58.2%) and subtotal obliteration in 8 patients (4.4%). No flow voids on MR imaging were observed in 18 patients (9.9%). The overall obliteration rates following one or multiple GKSs based on MR imaging or angiography was 68%. A small nidus volume, high margin dose, low number of isocenters, and no history of embolization were significantly associated with an increased rate of obliteration. Twenty-one patients experienced 25 episodes of hemorrhage in 850 risk-years following GKS, yielding an annual hemorrhage rate of 2.9%. Four patients died in this series: 2 due to complications of hemorrhage and 2 due to unrelated diseases. Permanent neurological deficits caused by radiation were noted in 9 patients (4.9%).

Conclusions

Gamma Knife surgery offers a reasonable chance of obliterating basal ganglia and thalamic AVMs and does so with a low risk of complications. It is an optimal treatment option in patients for whom the anticipated risk of microsurgery is too high.

Stereotactic radiosurgery of cranial arteriovenous malformations and dural arteriovenous fistulas

Cranial arteriovenous malformations (AVM) and cranial dural arteriovenous fistulas (AVF) carry a significant risk of morbidity and mortality when they hemorrhage. Current treatment options include surgery, embolization, radiosurgery, or a combination of these treatments. Radiosurgery is thought to reduce the risk hemorrhage in AVMs and AVFs by obliterating of the nidus of abnormal vasculature over the course of 2 to 3 years. Success in treating AVMs is variable depending on the volume of the lesion, the radiation dose, and the pattern of vascular supply and drainage. This article discusses the considerations for selecting radiosurgery as a treatment modality in patients who present with AVMs and AVFs.

Hemorrhage risk of cerebral arteriovenous malformations before and during the latency period after GAMMA knife radiosurgery

BACKGROUND AND PURPOSE

To evaluate the hemorrhage rates of cerebral arteriovenous malformations (AVM) and the risk factors of hemorrhage before and after Gamma Knife radiosurgery (GKS).

METHODS

The annual hemorrhage rate was calculated as the number of hemorrhages divided by the patient-years at risk. Characteristics of patients and AVM related to hemorrhagic or nonhemorrhagic presentation were evaluated by logistic regression. Risk factors predicting AVM hemorrhage during the period from the diagnosis to GKS of AVM and during the latency period after radiosurgery were evaluated using Cox regression hazards model.

RESULTS

The annual hemorrhage rate before GKS was 2.0% assuming patients were at risk for hemorrhage since their birth. The hemorrhage rate calculated between the diagnosis and GKS of AVM was 6.6% and reduced to 2.5% after GKS until obliteration of the AVM. Although small and deep nidi and those with deep and single draining veins tended to present themselves with hemorrhage, only nidi with single draining veins and those ruptured before were more likely to bleed once the AVM had been diagnosed. These factors no longer predisposed the nidus to a rupture after radiosurgery and the only predicting factor for hemorrhage was a low radiosurgical prescription dose to the margin of nidus.

CONCLUSIONS

The AVM hemorrhage rate seems to reduce after GKS. After radiosurgery, none of the patients or nidus-related risk factors remained relevant to the occurrence of hemorrhage. The nidus treated with a high radiosurgical dose is less likely to bleed.

Radiosurgical management of pediatric arteriovenous malformations

PURPOSE

Hemorrhage from an arteriovenous malformation (AVM) is the commonest cause of childhood stroke. Management options for children include observation and medical management, surgical resection, endovascular embolization, or stereotactic radiosurgery, alone or in combination.

METHODS

Radiosurgery is used for high-risk malformations in critical brain locations. While this goal is being achieved, there should be limited morbidity and hopefully no mortality from hemorrhage or radiation-induced brain injury.

RESULTS

Physicians who consider AVM radiosurgery cite one or more of the following: (1) that radiosurgery is an effective therapy required for the management of deep-brain AVMs; (2) that radiosurgery is an effective therapy for residual AVMs after subtotal resection; (3) that radiosurgery is worthwhile in an attempt to lower management risks for AVMs in functional brain locations; (4) since embolization does not cure most AVMs, additional therapy such as radiosurgery may be required; and (5) microsurgical resection may not be the best choice for some children.

CONCLUSION

Radiosurgery is the first and only biologic AVM therapy; it represents the beginnings of future cellular approaches to vascular malformation diseases. For this reason, the future of radiosurgery may be impacted positively by the development of other biologic strategies such as brain protection or endothelial sensitization.

Repeat Gamma Knife Surgery for Incompletely Obliterated Cerebral Arteriovenous Malformations

OBJECTIVE

The causes of failure after an initial Gamma procedure were studied, along with imaging and clinical outcomes, in a series of 140 patients with cerebral arteriovenous malformations (AVMs) treated with repeat Gamma Knife surgery (GKS).

METHODS

Causes of initial treatment failure included inaccurate nidus definition in 14 patients, failure to fill part of the nidus as a result of hemodynamic factors in 16, recanalization of embolized AVM compartments in 6, and suboptimal dose (&lt; 20 Gy) in 23. Nineteen patients had repeat GKS for subtotal obliteration of AVMs. In 62 patients, the AVM failed to obliterate despite correct target definition and adequate dose. At the time of retreatment, the nidus volume ranged from 0.1 to 6.9 cm3 (mean, 1.4 cm3), and the mean prescription dose was 20.3 Gy.

RESULTS

Repeat GKS yielded a total angiographic obliteration in 77 patients (55%) and subtotal obliteration in 9 (6.4%). In 38 patients (27.1%), the AVMs remained patent, and in 16 patients (11.4%), no flow voids were observed on magnetic resonance imaging. Clinically, 126 patients improved or remained stable, and 14 experienced deterioration (8 resulting from a rebleed, 2 caused by persistent arteriovenous shunting, and 4 related to radiation-induced changes).

CONCLUSION

By using repeat GKS, we achieved a 55% angiographic cure rate. Although radiation-induced changes as visualized on magnetic resonance imaging occurred in 48 patients (39%), only 4 patients (3.6%) developed permanent neurological deficits. These findings may be useful in deciding the management of AVMs in whom total obliteration after initial GKS was not achieved.

Radiosurgical considerations in the treatment of large cerebral arteriovenous malformations

OBJECTIVE

In order to establish the role of Gamma Knife radiosurgery (GKS) in large intracranial arteriovenous malformations (AVMs), we analyzed clinical characteristics, radiological features, and radiosurgical outcomes.

METHODS

Between March 1992 and March 2005, 28 of 33 patients with large AVMs (> 10 cm(3) in nidus-volume) who were treated with GKS underwent single session radiosurgery (RS), and the other 5 patients underwent staged volumetric RS. Retrospectively collected data were available in 23 cases. We analyzed treatment outcomes in each subdivided groups and according to the AVM sizes. We compared the estimated volume, defined as primarily estimated nidus volume using MR images, with real target volume after excluding draining veins and feeding arteries embedded into the nidus.

RESULTS

Regarding those patients who underwent single session RS, 44.4% (8/18) had complete obliteration; regarding staged volumetric RS, the obliteration rate was 40% (2/5). The complete obliteration rate was 60% (6/10) in the smaller nidus group (10-15 cm(3) size), and 25% (2/8) in the larger nidus group (over 15 cm(3) size). One case of cerebral edema and two cases (8.7%) of hemorrhage were seen during the latent period. The mean real target volume for 18 single sessions of RS was 17.1 cm(3) (10.1-38.4 cm(3)), in contrast with the mean estimated volume of 20.9 cm(3) (12.0-45.0 cm(3)).

CONCLUSION

The radiosurgical treatment outcomes of large AVMs are generally poor. However, we presume that the recent development in planning software and imaging devices aid more accurate measurement of the nidus volume, therefore improving the treatment outcome.

THE PROTECTIVE STATUS OF SUBTOTAL OBLITERATION OF ARTERIOVENOUS MALFORMATIONS AFTER RADIOSURGERY

OBJECTIVE

Arteriovenous malformations (AVMs) treated by radiosurgery with complete obliteration of the nidus but a persisting early draining vein on follow-up angiography can be termed subtotally obliterated. However, these are persistent circulating AVMs. The significance of these lesions, their hemorrhage rate, and their management are analyzed.

METHODS

In a series of 862 consecutive patients with AVMs treated by radiosurgery, 121 patients (14%) achieved subtotal obliteration (STO). The angiographic evolution and rate of obliteration were studied. The pretreatment angiographic features, dosimetric parameters, and postradiosurgery hemorrhage rate were compared with those in the rest of the treated population. Finally, the options for follow-up and treatment were analyzed.

RESULTS

Of 121 subtotally obliterated AVMs, the bleeding rate was 0%; 53% of patients achieved complete obliteration. This occurred in 71% of those who had STO at 1 year. In the cases in which STO was detected at 2, 3, and 4 years, total obliteration eventually occurred in 43%, 28.5%, and 0%, respectively. Comparative analysis with AVMs in which a part of the nidus persisted showed a significant difference in the bleeding rate. Except for volume, no significant statistical difference in angiographic and dosimetric parameters was found between the STO group and the rest of the studied population with residual nidus. Six cases received further treatment, resulting in 2 cures and 2 treatment-related complications.

CONCLUSION

Subtotally obliterated AVMs are different from other partially obliterated AVMs, with a 0% bleeding rate. Their complete obliteration is a function of delay of appearance on follow-up angiography. Invasive follow-up and further treatment of these AVMs do not seem warranted.

Thrombosis and hemorrhage in the acute period following Gamma Knife surgery for arteriovenous malformation

Bleeding of an arteriovenous malformation (AVM) following stereotactic radiosurgery (SRS) is a known risk during the latency interval, but hemorrhage in the 30-day period following radiosurgery rarely has been reported in the literature. The authors present the case of a 57-year-old man who underwent Gamma Knife surgery for a large AVM, and they provide radiographic documentation of a thrombus in the primary draining vein immediately preceding an AVM hemorrhage within 9 days after radiosurgery. They postulate that the pathophysiology of an AVM hemorrhage in the acute period following SRS is related to an association among tissue irradiation, acute inflammatory response, and vessel thrombosis.

The authors also review the literature on risk factors for hemorrhage due to untreated and radiosurgically treated AVMs. Recent evidence on the role of inflammation in the pathogenesis of AVMs and the pathophysiology of AVM rupture is presented. Inflammatory markers have been demonstrated in brain AVM tissue, and the association between inflammation and AVM hemorrhage has been established. There is an acute inflammatory response following tissue irradiation, resulting in structural and functional vascular changes that can lead to vessel thrombosis. Early hemorrhage following radiosurgical treatment of AVMs may be related to the acute inflammatory response and associated vascular changes that occur in irradiated tissue. In the first stage of a planned 2-stage Gamma Knife treatment for a large AVM in the featured case, the superior posteromedial portion of the primary draining vein was included in the treatment field. The authors present the planning images and subsequent CT scans demonstrating a new venous thrombus in the primary draining vein. An acute inflammatory response following radiosurgery with resultant acute venous thrombus formation and venous obstruction is proposed as one mechanism of an AVM hemorrhage in this patient. Radiographic evidence of the time course of thrombosis and hemorrhage supports the hypothesis that acute venous obstruction is a cause of intracranial hemorrhage.

Definition of the key target volume in radiosurgical management of arteriovenous malformations: a new dynamic concept based on angiographic circulation time

Object

The cumulative experience worldwide indicates complete radiosurgical obliteration rates of brain arteriovenous malformations (AVMs) ranging from 35 to 90%. The purpose of this study was to propose a strategy to increase the obliteration rate for AVMs through the dynamic definition of the key target volume (KTV).

Methods

A prospective series of patients harboring an AVM was assessed using digital subtraction angiography in which a digital counter was used to measure the several stages of the frame-by-frame circulation time. All the patients were analyzed using dynamic measurement planning to define the KTV, corresponding to the volume of the shunt with the least vascular resistance and the earliest venous drainage. All patients underwent catheter-based angiography, a subgroup was additionally assessed by means of a superselective catheterization, and among these a further subgroup received embolization. The shunts were also categorized according to their angioarchitectural type: fistulous, plexiform, or mixed. The authors applied the radiosurgery-based grading system (RBGS) as well to find a correlation with the obliteration rate.

Results

This series includes 44 patients treated by radiosurgery; global angiography was performed for all patients, including dynamic measurement planning. Eighty-four percent of them underwent superselective catheterization, and 50% of the total population underwent embolization. In the embolized arm of the study, the pretreatment volume was up to 120 ml. In patients with a single treatment, the mean volume was 8.5 ml, and the median volume was 6.95 ± 4.56 ml (mean ± standard deviation), with a KTV of up to 15 ml. For prospectively staged radiosurgery, the mean KTV was 28 ml. The marginal radiation dose was 18–22 Gy, with a mean of dose 20 Gy. The mean RBGS score was 1.70. The overall obliteration rate was 91%, including the repeated radiosurgery group (4 patients), in which 100% showed complete obliteration. The overall permanent deficit was 2 of 44 patients, 1 in each group.

Conclusions

Dynamic definition of the KTV might increase the obliteration rate, even in complex AVMs, allowing the treatment of smaller volumes off the recruitment vessels (pseudonidus). By using this technique, the authors avoided double-blind treatment, where the neurosurgeon does not know precisely which type of lesion he or she is irradiating and the interventionalist does not know why and what he or she is embolizing.

Embolization of Arteriovenous Malformation. Efficacy and Safety of Preoperative Embolization Followed by Surgical Resection of AVM

SUMMARY

Treatment options for cerebral arteriovenous malformation (AVM) are still controversial due to the recent result of stereotactic radiosurgery and the improved result of microsurgical resection. We investigated previously treated AVM cases and discussed the efficacy and safety of preoperative embolization especially for microsurgical resection of high-grade AVM in the Spetzler-Martin grading. Efficacy of preoperative embolization was evaluated based on 126 previously treated AVM cases at Shinshu University Hospital during the last 25 years. The safety of embolization was evaluated based on our previously-embolized 58 AVM cases (91 procedures) in the last 11 years after introduction of preoperative embolization for AVM. In all 126 cases, 82 were treated before introduction of embolization and 44 were treated after introduction of embolization. In 82 cases of the pre-embolization era, 63 lesions were removed totally in 63 AVMs (77%), partially resected in 11 (13%) and untreated in eight (10%). In 74 surgically removed cases, 11 (15%) cases showed severe intra/postoperative bleeding. In 44 cases of the embolization era, lesions were removed totally in 29 AVMs (66%), disappeared only with embolization in one (2%), disappeared with radiosurgery in seven (16%) and were untreated in five (11%). In 32 surgically removed cases, only one (2%) case showed severe intra/postoperative bleeding. In all 58 embolized cases, 44 were surgically removed, six were treated with radiosurgery, one was eliminated with embolization alone and six were partially obliterated and followed up for their location. In 91 procedures for 58 cases, two haemorrhagic and three ischemic complications occurred, three were transient and two remained having neurological deficits. The introduction of preoperative embolization improved the total removal rate and reduced the intra/postoperative bleeding rate in surgical removal of AVM. The total risk of embolization is low and well-designed preoperative embolization makes surgical resection safer even in high-grade AVM in the Spetzler-Martin grading.

Advances in the radiosurgical treatment of large inoperable arteriovenous malformations

Radiosurgery has proven useful in the treatment of small arteriovenous malformations (AVMs) of the brain. However, the volume of healthy tissue irradiated around large lesions is rather significant, necessitating reduced radiation doses to avoid complications. As a consequence, this can produce poorer obliteration rates. Several strategies have been developed in the past decade to circumvent dose-volume problems with large AVMs, including repeated treatments as well as dose, and volume fractionation schemes. Although success on par with that achieved in lesions smaller than 3 ml remains elusive, improvements over the obliteration rate, the complication rate or both have been reported after conventional single-dose stereotactic radiosurgery (SRS). Radiosurgery with a marginal dose or peripheral dose < 15 Gy rarely obliterates AVMs, yet most lesions diminish in size posttreatment. Higher doses may then be reapplied to any residual nidi after an appropriate follow-up period. Volume fractionation divides AVMs into smaller segments to be treated on separate occasions. Doses > 15 Gy irradiate target volumes of only 5-15 ml, thereby minimizing the radiation delivered to the surrounding brain tissue. Fewer adverse radiological effects with the use of fractionated radiosurgery over standard radiosurgery have been reported. Advances in AVM localization, dose delivery, and dosimetry have revived interest in hypofractionated SRS. Investigators dispensing >or= 7 Gy per fraction minimum doses have achieved occlusion with an acceptable number of complications in 53-70% of patients. The extended latency period between treatment and occlusion, about 5 years for emerging techniques (such as salvage, staged volume, and hypofractionated radiotherapy), exposes the patient to the risk of hemorrhage during that period. Nevertheless, improvements in dose planning and target delineation will continue to improve the prognosis in patients harboring inoperable AVMs.

Microsurgery or Radiosurgery for Cerebral Arteriovenous Malformations? A Study of Two Paired Series

OBJECTIVE

To detect parameters that may augment the therapeutic strategy in patients with a cerebral arteriovenous malformation (AVM) that is considered equally suitable for treatment by neurosurgery or radiosurgery, we compared the efficacy and risks of these two methods in a paired series with similar patient and AVM characteristics.

PATIENTS AND METHODS

Two series of patients with AVM were studied, including a series of 39 patients treated using microsurgery (MS) and another series of 39 patients treated via radiosurgery (RS). These series were paired for age and sex, initial symptoms, size, location and Spetzler-Martin grade, and presence of embolization preceding treatment. We compared the posttreatment outcome in the two groups with respect to obliteration rate, neurological status, mortality rate, and recurrent bleeding. Statistical analysis was performed using paired Student's t test.

RESULTS

The Glasgow Outcome Scale values and Modified Rankin Scores measured at discharge and 12 to 24 months were significantly better in the RS series than in the MS series. The obliteration rate tended to be higher in the MS series (91% versus 81%; P = 0.10, not significant), whereas the rate of neurological deficit was higher in the MS series than in the RS series(P &lt; 0.001). The mortality rate was not significantly different in the two series, but the rate of recurrent bleeding was higher in the RS group (10% versus 0%; P = 0.04).

CONCLUSIONS

Although the rate of cure was similar for patients treated with MS and RS, neurological morbidity was higher after MS and recurrent bleeding was more frequent after RS.

ARTERIOVENOUS MALFORMATIONS AFTER LEKSELL GAMMA KNIFE RADIOSURGERY

OBJECTIVE

Although relevant information exists regarding the chance of obliterating arteriovenous malformations (AVMs) using radiosurgery, the overall chance of cure after gamma knife radiosurgery is usually only extrapolated from a portion of all monitored patients. This chance and the risks involved in radiosurgery, including repeat treatment when necessary in a defined population of treated patients, were analyzed in our study.

METHODS

Between October 1992 and June 2000, gamma knife radiosurgery was performed on 330 patients with AVMs. The volume of the AVM nidus ranged from 0.15 to 28.6 cm3 (median, 3.9 cm3). When complete obliteration was not achieved within 3 years, repeat radiosurgery was performed on 76 patients. The volume of the nidus for the second treatment ranged from 0.09 to 16.8 cm3 (median 2.9 cm3). The result was reviewed in 300 (91%) patients after the first round of treatment and in 68 (89.5%) after the second round of treatment.

RESULTS

AVM obliteration was achieved in 222 (74%) patients after the first round of radiosurgery and in 47 (69%) after the second. The overall chance of cure was 92% (269 patients). Final angiography verified complete obliteration by 12 to 96 months (median, 25 mo) after initial radiosurgery. Smaller volume AVMs and the application of a higher radiation dose resulted in a higher chance of obliteration. The risk of rebleeding after radiosurgery was 2.1% annually until full obliteration, and the overall mortality from rebleeding was 1%. The risk of permanent morbidity after the first and second radiosurgery treatments were 2.7 and 2.9%, respectively. The cumulative risk of morbidity in both groups of patients was 3.4%.

CONCLUSION

Although one-quarter of the patients required that the treatment be repeated, gamma knife radiosurgery can offer a high cure rate for patients treated for AVMs with a low risk of morbidity and mortality from rebleeding during the latent period.

Prospective staged volume radiosurgery for large arteriovenous malformations: indications and outcomes in otherwise untreatable patients

OBJECTIVE

The obliteration response of an arteriovenous malformation (AVM) to radiosurgery is strongly dependent on dose and volume. For larger volumes, the dose must be reduced for safety, but this compromises obliteration. In 1992, we prospectively began to stage anatomic components in order to deliver higher single doses to symptomatic AVMs >15 ml in volume.

METHODS

During a 17-year interval at the University of Pittsburgh, 1040 patients underwent radiosurgery for a brain AVM. Out of 135 patients who had multiple procedures, 37 patients underwent prospectively staged volume radiosurgery for symptomatic otherwise unmanageable larger malformations. Twenty-eight patients who were managed before 2002 were included in this study to achieve sufficient follow-up in assessing the outcomes. The median age was 37 years (range, 13-57 yr). Thirteen patients had previous hemorrhages and 13 patients had attempted embolization. Separate anatomic volumes were irradiated at 3 to 8 months (median, 5 mo) intervals. The median initial AVM volume was 24.9 ml (range, 10.2-57.7 ml). Twenty-six patients had two stages and two had three-stage radiosurgery. Seven patients had repeat radiosurgery after a median interval of 63 months. The median target volume was 12.3 ml. (range, 4.2-20.8 ml.) at Stage I and 11.5 ml. (range, 2.8-22 ml.) at Stage II. The median margin dose was 16 Gy at both stages. Median follow-up after the last stage of radiosurgery was 50 months (range, 3-159 mo).

RESULTS

Four patients (14%) sustained a hemorrhage after radiosurgery; two died and two patients recovered with mild permanent neurological deficits. Worsened neurological deficits developed in one patient. Seizure control was improved in three patients, was stable in eight patients and worsened in two. Magnetic resonance imaging showed T2 prolongation in four patients (14%). Out of 28 patients, 21 had follow-up more than 36 months. Out of 21 patients, seven underwent repeat radiosurgery and none of them had enough follow- up. Of 14 patients followed for more than 36 months, seven (50%) had total, four (29%) near total, and three (21%) had moderate AVM obliteration.

CONCLUSIONS

Prospective staged volume radiosurgery provided imaging defined volumetric reduction or closure in a series of large AVMs unsuitable for any other therapy. After 5 years, this early experience suggests that AVM related symptoms can be stabilized and anticipated bleed rates can be reduced.

Delayed Hemorrhage From Completely Obliterated Arteriovenous Malformation After Gamma Knife Radiosurgery

A 43-year-old female was treated with gamma knife radiosurgery (GKS) for right frontal arteriovenous malformation (AVM) manifesting as absence seizures. Complete nidus obliteration was confirmed on angiography 4 years after GKS. However, she experienced recurrence of her previous seizures and delayed hemorrhage occurred within the treated nidus, despite absence of abnormalities by repeated angiography 81 months after GKS. She was treated conservatively and discharged home without neurological deficits. The risk of hemorrhage from obliterated AVM is significantly reduced but not eliminated after radiosurgery. Recanalization of thrombus that is too small to detect by neuroimaging may result in delayed hemorrhage.

Treatment outcome after linac-based radiosurgery in cerebral arteriovenous malformations: Retrospective analysis of factors affecting obliteration

PURPOSE

We investigated patient outcome and factors affecting obliteration rate after radiosurgery in cerebral arteriovenous malformations (AVM).

MATERIAL AND METHODS

We have treated 110 patients with cerebral AVM with linac-based radiosurgery (RS). AVM classification according Spetzler-Martin was 17 patients grade I (15%), 39 grade II (36%), 41 grade III (37%), 12 grade IV (11%) and 1 grade V (1%). Median single dose was 18 Gy. Mean treatment volume was 4.7 cc (range, 0.1-24.0 cc). Fifty-two patients experienced hemorrhage prior to RS. Median follow-up was 2.5 years.

RESULTS

Actuarial complete obliteration rate (CO) was 51% after 3 years and 67% after 4 years. CO rate was significantly higher in AVM <3 cm (64% vs. 43%, P<0.04) and in patients with grade I/II vs. III-V (71% vs. 33%, P<0.001). CO was significantly improved after doses >18 Gy (P<0.02) and in male gender (P<0.04). In multivariate analysis Spetzler-Martin grade remained significant. Intracranial hemorrhage after RS occurred in 9 patients 13.9 months median after RS. Neurological dysfunction improved/completely dissolved or remained stable in 95% of patients. No new onset of neurological dysfunction was seen. No significant adverse effects after RS were seen.

CONCLUSIONS

The rate of obliteration after RS in AVM depends on applied single dose as well as size and Spetzler-Martin grade. RS is an alternative to neurosurgery, especially in patients with small or surgically inaccesible AVM.

Long-term Results after Fractionated Radiation Therapy for Large Brain Arteriovenous Malformations

OBJECTIVE:

To study the results after fractionated radiotherapy of large arteriovenous malformations (AVMs).

METHODS:

Twenty-eight patients harboring large AVMs were treated between 1980 and 1985 with fractionated radiotherapy with up to 3.5 Gy per fraction twice a week to a total dose of 41 to 50 Gy. All but 5 patients were examined with an angiogram at least 4 years after the treatment.

RESULTS:

Two AVMs (8%) were obliterated after the treatment. Eight patients died: five as a result of hemorrhages, two of unknown causes, and one as a result of lung carcinoma. Five patients deteriorated slightly, three moderately, and four severely after the treatment. The longer the observation time, the higher the incidence of neurological deterioration. The AVMs were significantly larger in the four patients who developed a severe deficit after the treatment. The annual hemorrhage rate was 6% after the treatment, suggesting that radiation did not protect from hemorrhage unless the AVM was occluded. AVMs with a pretreatment rupture had a annual hemorrhage rate of 12%, compared with 1% in the unruptured cases.

CONCLUSION:

The obliteration rate after fractionated radiotherapy with a dose per fraction of 2 to 4 Gy to a total dose of up to 50 Gy was low. The clinical outcome suggests that the radiation treatment may have caused significant side effects. Although the risk for hemorrhage in previously ruptured large AVMs is high, the use of fractionated radiotherapy using low doses per fraction cannot be recommended.

Natural history, evaluation, and management of intracranial vascular malformations

Intracranial vascular malformations are seen increasingly in clinical practice, primarily because of advances in cross-sectional brain and spinal cord imaging. Commonly encountered lesion types include arteriovenous malformations, cavernous malformations, venous malformations, dural arteriovenous fistulas, and capillary telangiectasias. Patients can experience various symptoms and signs at presentation. The natural history of vascular malformations depends on lesion type, location, size, and overall hemodynamics. The natural history for each lesion subtype is reviewed, with special consideration of the risk of hemorrhage or other adverse outcomes after the lesion is detected and any known predictors of hemorrhage or other outcomes. In practice, these data are compared with the risk of available treatment options as the optimal management is clarified. A multidisciplinary approach including neurosurgery, radiosurgery, interventional neuroradiology, and vascular neurology is most useful in determining the best management strategy.

The risk of hemorrhage after radiosurgery for cerebral arteriovenous malformations

BACKGROUND

Angiography shows that stereotactic radiosurgery obliterates most cerebral arteriovenous malformations after a latency period of a few years. However, the effect of this procedure on the risk of hemorrhage is poorly understood.

METHODS

We performed a retrospective observational study of 500 patients with malformations who were treated with radiosurgery with use of a gamma knife. The rates of hemorrhage were assessed during three periods: before radiosurgery, between radiosurgery and the angiographic documentation of obliteration of the malformation (latency period), and after angiographic obliteration.

RESULTS

Forty-two hemorrhages were documented before radiosurgery (median follow-up, 0.4 year), 23 during the latency period (median follow-up, 2.0 years), and 6 after obliteration (median follow-up, 5.4 years). As compared with the period between diagnosis and radiosurgery, the risk of hemorrhage decreased by 54 percent during the latency period (hazard ratio, 0.46; 95 percent confidence interval, 0.26 to 0.80; P=0.006) and by 88 percent after obliteration (hazard ratio, 0.12; 95 percent confidence interval, 0.05 to 0.29; P<0.001). The risk was significantly reduced during the period after obliteration, as compared with the latency period (hazard ratio, 0.26; 95 percent confidence interval, 0.10 to 0.68; P=0.006). The reduction was greater among patients who presented with hemorrhage than among those without hemorrhage at presentation and similar in analyses that took into account the delay in confirming obliteration by means of angiography and analyses that excluded data obtained during the first year after diagnosis.

CONCLUSIONS

Radiosurgery significantly decreases the risk of hemorrhage in patients with cerebral arteriovenous malformations, even before there is angiographic evidence of obliteration. The risk of hemorrhage is further reduced, although not eliminated, after obliteration.

Bleeding after Radiosurgery for Cerebral Arteriovenous Malformations

OBJECTIVE:

Obliteration is progressive after radiosurgery (RS) for cerebral arteriovenous malformation (AVM), and until it is complete, there is still a risk of hemorrhage. The aim of our study was to evaluate the severity of hemorrhage after RS, the actuarial risk of hemorrhage, and the parameters associated with hemorrhage.

METHODS:

Of 756 patients treated by linear accelerator RS for AVM, 51 (6.5%) had one or more hemorrhages after the RS. We studied the clinical, anatomic, and dosimetric parameters and obliteration rate before hemorrhage and then calculated the actuarial risk per patient and per hemorrhage before and after RS. Correlations between parameters and risk were studied by univariate and multivariate analysis using Kaplan-Meier hemorrhage-free survival curves and the Cox model.

RESULTS:

Apart from one exclusively ventricular hemorrhage, which caused the death of the patient, only parenchymal hemorrhages were associated with morbidity and neurological deficits (64.5% of all cases of hemorrhage had neurological deficits, 45% had a permanent deficit). The overall mortality rate per hemorrhage was 7.14%. The overall morbidity rate was 47.6%, 26.2% with a permanent deficit. In all but one patient, the AVM was not cured before hemorrhage; thus, the mean obliteration rate before hemorrhage was 24%. The actuarial hemorrhage rates were 3.08% per year per patient and 3.31% per year per hemorrhage. The actuarial rate per patient increased from 1.66% the 1st year to 3.87% in the 5th year after RS but was not statistically different from the rate before radiosurgery. The parameters found to be correlated with hemorrhage risk after RS using multivariate analysis were intranidal or paranidal aneurysms, complete coverage, and minimum dose.

CONCLUSION:

The risk of hemorrhage after RS would seem to be the sum of hemorrhage risk factors of the AVM and factors predicting a poor level of obliteration. These factors can be predicted in some cases but rarely avoided.

Gamma knife radiosurgery for cerebral arteriovenous malformations

Since its introduction, gamma knife radiosurgery has become an important treatment modality for cerebral arteriovenous malformations. This paper is a brief overview of the technique used, of the clinical results achieved and of the experience gained in Sheffield.

Patient outcomes after arteriovenous malformation radiosurgical management: results based on a 5- to 14-year follow-up study

OBJECTIVE

Radiosurgery is commonly performed for patients with small to medium-sized arteriovenous malformations (AVMs). However, few articles present overall outcomes after one or more radiosurgical procedures, and few data are available for periods longer than 5 years after AVM radiosurgery.

METHODS

Between 1990 and 1997, 144 patients underwent AVM radiosurgery and had angiographic follow-up. Of these patients, 112 (78%) had Spetzler-Martin Grade III or greater AVMs; 37 (26%) were located in the basal ganglia, thalamus, or brainstem. Twenty-six patients (18%) underwent repeat radiosurgery. The mean follow-up of 15 patients who died as a result of AVM bleeding or underwent AVM resection after the initial radiosurgery was 22 months (range, 3-47 mo); the mean follow-up of the remaining 129 patients was 86 months (range, 23-169 mo).

RESULTS

Excellent (obliteration without deficit, n = 96) or good (obliteration with minor deficit, n = 9) outcomes were achieved in 73% of patients after one or more radiosurgical procedures. Twenty patients (14%) sustained major deficits (n = 15; five had obliteration) or died (n = 5) after radiosurgery. Sixteen patients (11%) had unchanged neurological examinations but persistent arteriovenous shunting. Five patients (4%) required surgery (cystoperitoneal shunting, n = 1; AVM resection, n = 4) at a median of 65 months after radiosurgery because of symptomatic cyst formation or persistent edema. The radiosurgery AVM score correlated with both excellent (R(2) = -0.93, P = 0.003) and excellent or good (R(2) = -0.92, P = 0.004) outcomes.

CONCLUSION

The majority of AVM patients are protected from the risk of future hemorrhage and continue their normal daily activities after radiosurgery. Late complications requiring treatment are rare but can occur many years after patients are considered cured of their AVMs. Overall outcomes after AVM radiosurgery seem to be predicted accurately by the described method.

Management of patients with brain arteriovenous malformations

Arteriovenous malformations (AVMs) of the brain, which are probably genetically determined, are errors in the development of the vasculature that, together with the effects of blood flow, may lead to a focal arteriovenous shunt. Clinically, the adult patient may present with acute or chronic neurological symptoms-fixed or unstable-such as deficits, seizures or headache. Sometimes the lesion is an incidental finding. In about half of the patients, the revealing event is an intracranial haemorrhage. The prevalence of AVM in the western world is probably <0.01% and the detection rate is about one per 100,000 person-years. Most AVMs are revealed in patients 20-40 years of age. Therefore, the risk of developing neurological symptoms from an AVM, usually because of haemorrhage, increases with patient age. In the young adult population, AVMs are significant risk factors for hemorrhagic stroke. This risk increases with AVM volume and is higher in centrally located AVMs. Almost all patients with AVM are subjected to treatment, either by surgery, radiosurgery or embolisation, with the functional aim of reducing the risk of haemorrhage or to alleviate neurological symptoms with an acceptable treatment risk. Few neurocentres have physicians highly skilled in all treatment modalities. Therefore, the prescribed treatment may not be defined from an objective assessment of what is optimal for each individual patient, but rather from local expertise. In this context, more and better data about the natural history and the outcome of different treatments, as well as predictive models, would be valuable to help to optimise the management. Management strategies obviously differ according to local preferences, but results presented in the literature suggest the following strategy: (I) cortically located AVMs with a nidus volume <10 ml could be operated, with or without presurgical embolisation, unless there is a single feeder that can easily be catheterised and embolised for obliteration or other obvious target for embolisation, such as pseudoaneurysms or large fistulae; (II) centrally located AVMs with a nidus volume <10 ml should be treated by radiosurgery, unless suitable for embolisation as indicated above; (III) patients harbouring AVMs with a nidus volume >10 ml could benefit from targeted partial embolisation followed by radiosurgery or surgery, depending on the angioarchitecture; and (IV) AVMs >20 ml nidus volume usually have a high treatment risk with any treatment modality and are not obvious targets for treatment at all.

Hemorrhage risks and obliteration rates of arteriovenous malformations after gamma knife radiosurgery

Object. The purpose of this study was to analyze the risk of hemorrhage and the obliteration rate after treatment of patients with arteriovenous malformations (AVMs).

Methods. Between 1991 and 1995, 115 patients were treated using gamma knife radiosurgery (GKS). Surgical planning was based on angiograms and three-dimensional images. The angiographic features of the AVMs and the risk factors for hemorrhage were then evaluated.

Hemorrhages occurred in eight patients (7%) 7 to 42 months after GKS. Based on AVM morphology, the rates of hemorrhage were five (7.6%) of 66 for AVMs with a single draining vein, seven (14%) of 66 for AVMs with deep drainage, four (26.7%) of 15 for AVMs with a varix, four (28.6%) of 14 for AVMs with venous obstruction, eight (17.0%) of 47 for high-flow (shunt- and mixed-type) AVMs, and five (35.7%) of 14 for large AVMs with a volume of more than 10 cm3. No hemorrhages were observed in association with low-flow (moyamoya-type) AVMs in this series. Total AVM obliteration was achieved in 81.3% of 80 patients who underwent angiography. The obliteration rate was 91.3% for moyamoya-type AVMs and 67.6% for shunt- and mixed-type AVMs. Early obliteration within 12 months was achieved in 63% of the moyamoya-type AVMs.

Conclusions. Moyamoya-type AVMs seem to be at risk for post-GKS hemorrhage. Intravascular embolization should be considered prior to GKS for mixed- and shunt-type AVMs in an attempt to reduce the hemodynamic stress and thereby decrease the risk of hemorrhage.

Impact on the quality of life of patients with arteriovenous malformations during the latent interval between gamma knife radiosurgery and lesion obliteration

Object. The aim of this study was to measure the quality of life (QOL) in patients with cerebral arteriovenous malformations (AVMs) receiving gamma knife treatment before total AVM obliteration. Quality of life was assessed as it related to the knowledge of rebleeding risk during the waiting period, AVM symptoms, and previous bleeding.

Methods. Thirty-nine patients age 18 years or older without other medical problems were asked to complete a questionnaire that included demographic variables, immediate effect of gamma knife radiosurgery, symptoms of AVM, previous hemorrhage, and the Duke—University of North Carolina Health Profile (63 items).

Conclusions. The QOL of patients with cerebral AVM during the waiting period after undergoing gamma knife treatment was affected by irreversible physical disabilities rather than the knowledge of hemorrhage risk and bleeding experience.

A proposed radiosurgery-based grading system for arteriovenous malformations

OBJECT

Radiosurgery is an effective treatment strategy for properly selected patients harboring arteriovenous malformations (AVMs). Grading scales that are currently used to predict patient outcomes after AVM resection are unreliable tools for the prediction of the results of AVM radiosurgery.

METHODS

A grading system was developed to predict outcomes following AVM radiosurgery, based on the multivariate analysis of data obtained in 220 patients treated between 1987 and 1991 (Group 1). The dependent variable in all analyses was excellent patient outcome (complete AVM obliteration without any new neurological deficit). The grading scale was tested on a separate set of 136 patients with AVMs treated between 1990 and 1996 at a different center (Group 2). One hundred twenty-one (55%) of 220 Group 1 patients had excellent outcomes. Multivariate analysis identified five variables related to excellent patient outcomes: AVM volume (p = 0.001), patient age (p < 0.001), AVM location (p < 0.001), previous embolization (p = 0.02), and number of draining veins (p < 0.001). Regression analysis modeling permitted removal of two significant variables (previous embolization and number of draining veins) and resulted in the following equation to predict patient outcomes after AVM radiosurgery: AVM score = (0.1)(AVM volume in cm3) + (0.02)(patient age in years) + (0.3)(location of lesion: frontal or temporal) = 0; parietal, occipital, intraventricular, corpus callosum, cerebellar = 1; or basal ganglia, thalamic, or brainstem = 2). Seventy-nine (58%) of 136 Group 2 patients had excellent outcomes. All variables in the model remained significant for the Group 2 patients: AVM volume (p = 0.01), patient age (p = 0.01), and AVM location (p < 0.001). Testing of the entire model on the Group 2 patients demonstrated that the AVM score could be used to predict patient outcomes after radiosurgery (p < 0.0001). All patients with an AVM score of 1 or lower had an excellent outcome compared with only 39% of patients with an AVM score higher than 2. The Spetzler-Martin grade (p = 0.13), the K index (p = 0.26), and the obliteration prediction index (p = 0.21) did not correlate with excellent patient outcomes.

CONCLUSIONS

Despite significant differences in preoperative patient characteristics and dose prescription guidelines at the two centers, the proposed AVM grading system strongly correlated with patient outcomes after single-session radiosurgery for both patient groups. Although further testing of this model by independent centers using prospective methodology is still required, this system allows a more accurate prediction of outcomes from radiosurgery to guide choices between surgical and radiosurgical management for individual patients with AVMs.

Rupture of pial arteriovenous malformation associated with early thrombosis of the draining system following stereotactic radiosurgery--case report

A 50-year-old man was treated with stereotactic gamma knife radiosurgery for an incidentally detected small callosal arteriovenous malformation (AVM) with stenosis of the main draining pathway. He suffered two episodes of intraventricular hemorrhage at 4 and 14 weeks after the radiosurgery. Radiological studies demonstrated that the anterior portion of the draining system including a varix, which had been irradiated, was thrombosed before the obliteration of arteriovenous shunts. Stereotactic radiosurgery is an accepted treatment for selected small and medium AVMs, but this procedure may increase the risk of bleeding. Early occlusion of a part of the draining pathway after stereotactic radiosurgery might have induced AVM rupture. An impaired venous outlet, either consisting of one draining vein or with stenosis, present before treatment may be develop thrombosis in response to high-dose irradiation.

Decision analysis for small, asymptomatic intracranial arteriovenous malformations

Object

Asymptomatic intracranial arteriovenous malformations (AVMs) represent a clinically challenging problem because of the complex decision making that must be undertaken prior to beginning any type of treatment. In addition, the relative infrequency of these lesions means that there is relatively little experience reported in the literature. The authors use a decision-analysis technique to model the considerations that go into determining the treatment of these lesions in an effort to quantify the various risks and overall benefits conferred by the following three treatment strategies: observation/natural history, microsurgery, and stereotactic radiosurgery.

Methods

The authors conducted a thorough literature search to elucidate the risks and outcomes associated with each treatment option. These values were used to build and run a comprehensive Markov model to determine a base-case analysis. All of the input variables were also subjected to sensitivity analysis to identify the most influential input variables and the crossover points in which favored strategies changed.

The base-case analysis suggested that microsurgery was the favored treatment option because this hypothetical cohort accumulated 21.53 quality-adjusted life years (QALYs) over the course of the model compared with the 16.97 QALYs and 16.40 QALYs for stereotctic radiosurgery and observation, respectively. Sensitivity analysis demonstrated that overall major neurological morbidity and mortality were the most influential input variables both perioperatively and during the radiosurgical “latent” period (that is, up to 2 years posttreatment). The maximum acceptable perioperative combined major neurological morbidity and mortality rate was 6.8%. The latent period combined major neurological morbidity and mortality would need to be 0.7% to make radiosurgery favorable in this analysis.

Conclusions

Results of this decision analysis model suggest that microsurgery in the hands of experienced cerebrovascular surgeons, who can expect a less than 6.8% combined rate of major neurological morbidity and mortality, offers patients a greater overall quality of life over time.

Population-based analysis of arteriovenous malformation treatment

OBJECT

The author sought to describe overall management data on cerebral arteriovenous malformations (AVMs) and to focus the actuarial need for different treatment modalities on a population-based scale. Such data would seem important in the planning of regional or national multimodality strategies for the treatment of AVMs. This analysis of a nonselected, consecutive series of patients representing every diagnosed case of cerebral AVM in a population of 1,000,000 over one decade may serve to shed some light on these treatment aspects.

METHODS

During the 11-year period from 1989 to 1999, data from every patient harboring a cerebral AVM that was presented clinically or discovered incidentally in a strictly defined population of 986,000 people were collected prospectively. No patient was lost to follow up. There were 12.4 de novo diagnosed AVMs per 1,000,000 population per year (135 AVMs). Large high-grade AVMs (Spetzler-Martin classification) were rare, and Grade 1 to 3 lesions represented 85% of the caseload. Hemorrhage was the initial manifestation of AVM in 69.6% of the cases. lntracerebral hematoma was the most common hemorrhagic manifestation occurring in 78 patients. There were 4.4 cases per 1,000,000 population per year of hematomas needing expedient surgical evacuation. In the remaining patients who did not require hematoma surgery, small, critically located Grade 3 and Grade 4 lesions amounted to 1.6 cases per 1,000,000 population per year. There were 5.8 cases per 1,000,000 population per year of Grade 1 to 2 and larger noncritically located Grade 3 malformations. There were 0.5 cases per 1,000,000 population per year of Grade 5 AVMs. The overall outcome in 135 patients was classified as good according to the Glasgow Outcome Scale (Score 5) in 61% of the cases, and the overall mortality rate was 9%.

CONCLUSIONS

In centers with population-based referral, AVM of the brain is predominantly a disease related to intracranial bleeding. and parenchymal clots have a profound impact on overall management outcome. The rupture of an AVM is as devastating as that of an aneurysm. Aneurysm ruptures are more lethal, whereas AVM rupture tends to result in more neurological disability due to the high occurrence of lobar intracerebral hematoma. In an attempt to quantify the need for different modalities of AVM treatment based on a population of 1,000,000 people, figures for surgeries performed range from six to 10 operations per year and embolization as well as gamma knife surgery procedures range from two to seven per year, depending on the strategy at hand. When using nonsurgical approaches to Grade 1 to 3 lesions, the number of patients requiring treatment with more than one method for obliteration increases drastically as does the potential risk for procedure-related complications.