Gamma knife radiosurgery for arteriovenous malformations of basal ganglia, thalamus and brainstem--a retrospective study comparing the results with that for AVMs at other intracranial locations

The Efficacy and Disadvantages of Endovascular Therapy for Deep-Seated Cerebral Arteriovenous Malformations: A Long-Term Follow-Up Study

Arteriovenous malformations (AVMs) in the basal ganglia, the thalamus, and the insular lobe of the brain are rare and difficult-to-treat diseases that require integrated multimodal management. This study aimed to determine the safety and disadvantages of embolization as an independent therapy for deep-seated AVMs. The authors reviewed 76 patients from a single center with cerebral deep-seated AVMs from 2010 to 2020. Clinical hemorrhage refers to the initial clinical presentation with bleeding, the first occurrence of bleeding, and delayed postoperative hemorrhage refers to subsequent bleeding following the initial hemorrhage. After interventional therapy, 8 patients experienced delayed postoperative hemorrhage during the total follow-up of 94,631 person-years, with an annual postoperative hemorrhage rate of 3.1%. Compared with the overall clinical hemorrhage rate before treatment (15.9%/person-year), 11 patients experienced clinical hemorrhage during 25,238 person-years, indicating a significantly decreased risk of clinical hemorrhage after treatment. A total of 28.9% (22/76) of patients achieved angiographic obliteration. Multivariate analysis showed that pretreatment limb weakness and a high Spetzler-Martin grade predicted poor clinical outcomes (P = 0.043 and 0.005). Fewer feeding arteries predicted AVMs' obliteration (P = 0.048). Endovascular procedure-related complications, mortality, and morbidity were, respectively, reported in 7.9% (6/76), 1.3% (1/76), and 14.8% (8/54) of patients. Endovascular embolization significantly lowered the risk of clinical deterioration and delayed hemorrhage, indicating it to be a safe and effective therapy for deep-seated AVMs. Lesions with a simple angioarchitecture were more likely to be completely obliterated.

Outcomes of single-session gamma knife radiosurgery for deep-seated arteriovenous malformations

BACKGROUND

Deep-seated arteriovenous malformations (AVMs) pose unique surgical challenges due to their proximity to critical structures. Gamma knife radiosurgery (GKRS) thus serves a promising alternative that may reduce treatment-related morbidity of deep-seated AVMs. However, the efficacy of GKRS in achieving obliteration in deep AVMs is not established. Therefore, we examined our experience with GKRS in deep-seated AVMs.

METHODS

We retrospectively reviewed all deep-seated (thalamic, basal ganglia and brainstem AVMs) that underwent GKRS at our center between 2006 and 2022. Factors that predicted obliteration were assessed, and the incidence of various long-term complications was recorded.

RESULTS

The cohort comprised 137 patients, 74 males (54 %) and 63 females (46 %). The mean age was 25.1 ± 11.9 years. The mean dose delivered was 21.7 ± 2.6 Gy. The median volume of AVMs in our cohort was 3.2 cc (IQR: 1.5, 6.3 cc). The median follow-up was 36 months (IQR: 24, 42 months), following which 66 AVMs (48.2 %) were obliterated. Radiation-induced edema occurred in 8 cases (5.8 %), 7 of whom were symptomatic with neurological deficits (5.1 %). However, all patients improved on further follow-up with no residual neurological deficits. The median volume was significantly greater among cases with residual AVM (3.45 cc, IQR: 1.77, 6.85 cc) than those that were obliterated (2.77 cc, IQR: 1.09, 5.10 cc, p = 0.049). The mean Pollock Flickinger score was significantly greater among non-obliterated cases, as was the mean dose delivered (22.3 ± 2.7 Gy vs. 21.5 ± 2.8 Gy, p = 0.044). Multivariate analysis revealed that a nidus volume less than 3 cc was the only factor that predicted obliteration of the nidus (HR: 4.994, 2.139, 9.166, p = 0.016).

CONCLUSIONS

GKRS is an effective and safe treatment option for deep-seated AVMs. Obliteration occurred in 48.2% of cases, with complications in 5.8%. Nidus volume, rather than other clinical or radiological factors, appears to be the most significant predictor of successful obliteration. Despite the challenges posed by the complex anatomy of deep AVMs, including variable venous drainage and the potential for radiation-induced edema, GKRS is similarly effective in AVMs located in the thalamus, basal ganglia, and brainstem.

Spetzler-martin grade IV cerebral arteriovenous malformations in adult patients: a propensity-score matched analysis of resection and stereotactic radiosurgery

Spetzler-Martin Grade IV arteriovenous malformations (AVMs) are challenging due to high risks associated with both treatment and natural progression. This study compares the outcomes of microsurgical resection and stereotactic radiosurgery (SRS) in high-grade AVMs, analyzing obliteration rates, complications, and functional outcomes. A retrospective cohort of 96 patients treated with either microsurgical resection (33 patients) or SRS (63 patients) was analyzed. Propensity-score matching was employed to account for baseline variables such as AVM size (cm), preoperative embolization and rupture status. Primary endpoints included AVM obliteration, complication rates, and modified Rankin Scale (mRS) scores. After matching, 31 patients per group were analyzed. Microsurgical resection achieved significantly higher obliteration rates (87.1%) compared to SRS (32.3%, p < 0.001). In the matched SRS cohort (n = 31), the actuarial obliteration rates were 11% (95% CI: 0-22%) at 1 year, 17% (95% CI: 0-31%) at 3 years, and 43% (95% CI: 13-63%) at 5 years post-treatment. Complication rates were similar (32.3% resection, 38.7% SRS, p = 0.6). Functional outcomes in terms of improvement in modified Rankin Scale (mRS) scores were observed in 50.0% of microsurgery patients and 41.4% of SRS patients. However, the absolute number of patients improving was similar (13 vs. 12), and the microsurgery group had more cases of worsening mRS scores compared to the SRS group (4 vs. 2). The difference was not statistically significant (p = 0.4). Microsurgical resection offers superior obliteration rates for high-grade AVMs with comparable complication risks to SRS. SRS remains a valuable alternative for select patients, particularly those ineligible for resection. Future research should focus on optimizing multimodal treatment approaches. Clinical trial number Not applicable.

Stereotactic Radiosurgery for Intermediate (III) or High (IV-V) Spetzler-Martin Grade Arteriovenous Malformations: International Stereotactic Radiosurgery Society Practice Guideline

BACKGROUND AND OBJECTIVES

Consensus guidelines do not exist to guide the role of stereotactic radiosurgery (SRS) in the management of patients with Spetzler-Martin Grade III-V arteriovenous malformations (AVMs). We sought to establish SRS practice guidelines for Grade III-V AVMs based on a critical systematic review of the published literature.

METHODS

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant search of Medline, Embase, and Scopus, 1986 to 2023, for publications reporting post-SRS outcomes in ≥10 Grade III-V AVMs with the median follow-up ≥24 months was performed. Primary end points were AVM obliteration and post-SRS hemorrhage. Secondary end points included dosimetric variables, Spetzler-Martin parameters, and neurological outcome.

RESULTS

: In total, 2463 abstracts were screened, 196 manuscripts were reviewed, and 9 met the strict inclusion criteria. The overall sample of 1634 AVMs consisted of 1431 Grade III (88%), 186 Grade IV (11%), and 11 Grade V lesions (1%). Total median post-SRS follow-up was 53 months for Grade III and 43 months for Grade IV-V AVMs (ranges, 2-290; 12-262). For Grade III AVMs, the crude obliteration rate was 72%, and among Grade IV-V lesions, the crude obliteration rate was 46%. Post-SRS hemorrhage was observed in 7% of Grade III compared with 17% of Grade IV-V lesions. Major permanent deficits or death from hemorrhage or radiation-induced complications occurred in 86 Grade III (6%) and 22 Grade IV-V AVMs (12%).

CONCLUSION

Most patients with Spetzler-Martin Grade III AVMs have favorable SRS treatment outcomes; however, the obliteration rate for Grade IV-V AVMs is less than 50%. The available studies are heterogenous and lack nuanced, long-term, grade-specific outcomes.

The influence of hemorrhage presentation on clinical outcomes of curative embolisation in 125 cerebellar arteriovenous malformations

BACKGROUND

This study investigated the influence of periprocedural hemorrhage and clinical outcomes with an endovascular therapeutic strategy for cerebellar arteriovenous malformations (cAVMs).

METHODS

From December 2006 to January 2018, 125 cAVMs were classified as types I-IV and received endovascular embolization via Onyx or Glubran 2. The risk factors of hemorrhage were analyzed using univariate and multivariate logistic analyses. A modified Rankin Scale (mRS) score was used to evaluate the neurological function before and 1 year after the operation. Results Of 125 patients, 63 had type I cAVMs, 2 type II cAVMs, 48 type III cAVMs, and 12 type IV cAVMs. A total of 88 (70.4%) patients had clinical manifestations of intracranial hemorrhage. Multivariate logistic regression analysis showed that age (OR, 2.276; 95% CI, 1.132 - 5.663), flow-related aneurysm (OR, 2.845; 95% CI, 1.265 - 6.248), lesion size (OR, 3.005; 95% CI, 1.119 - 5.936), and the number of feeding arteries (OR, 0.105; 95% CI, 0.081 - 0.312) were still the significant independent risk factors of intracranial hemorrhage. During a 1-year follow-up, 109 patients (87.2%) had good outcomes (mRS 0 - 2), 12 patients (9.6%) had poor outcomes (mRS 3 - 4), 4 patients (3.2%) died, and 3 patients had intracranial hemorrhage due to the incomplete embolization of cAVMs.

CONCLUSIONS

Endovascular embolization is a feasible treatment for cAVMs. Age, flow-related aneurysm, lesion size, and the number of feeding arteries are the significant risk factors of periprocedural hemorrhage. Moreover, the lesion characteristics must be given full consideration when using Onyx or Glubran 2 before cAVMs embolization.

Endovascular embolization for basal ganglia and thalamic arteriovenous malformations

Background

Basal ganglia and thalamic arteriovenous malformations (AVMs) represent a special subset of malformations. Due to the involvement of vital brain structures and the specifically fine and delicate angioarchitecture of these lesions, it presents unique therapeutic challenges and technical difficulties that require thorough treatment planning, individualized treatment strategies, and advanced techniques for good clinical outcome.

Method

In this study, we presented a series of ruptured basal ganglia and thalamic AVMs embolized via a transarterial, transvenous or combined approach. Herein, we summarized our treatment experience and clinical outcomes to further evaluate the effectiveness and safety of endovascular embolization for these AVMs as well as the indications, therapy strategies, and techniques of embolization procedures.

Results

Twelve patients with basal ganglia and thalamus AVMs were included in the study. Their average age was 23.83 ± 16.51 years (range, 4-57 years) with a female predominance of 67% at presentation. The AVMs were located in the thalamus in 3 (25%) patients, in the basal ganglia in 3 (25%) patients, and in both sites of the brain in 6 (50%) patients. There were 5 AVMs located on the left side and 7 on the right. The mean nidus diameter was 3.32 ± 1.43 cm (range 1.3-6.1 cm). According to the Spetzler-Martin grading classification, 4 (33.3%) brain AVMs were Grade III, 7 (58.3%) were Grade IV, and 1 (8.3%) was Grade V. All of them presented with bleeding at admission: four of these patients presented with an intracerebral hemorrhage (ICH), 8 ICH in combination with intraventricular hemorrhage (IVH), and no patient with subarachnoid hemorrhage (SAH). Among these patients treated with endovascular embolization, 7 patients were treated by the transarterial approach, 4 patients transvenous approach, and 1 patient underwent the combined approach. A single embolization procedure was performed in 6 patients (50%) and the other 6 cases (50%) were treated in a staged manner with up to three procedures. Procedure-related complications occurred only in two patient (16.7%). Complete AVM obliteration was obtained in 7 patients (58.3%), and partial obliteration was in 4 patients (33.3%). Overall, good or excellent outcomes were obtained in 7 patients (58.3%), and poor functional outcome was observed in 5 patients (41.7%) at the last follow-up. All survived patients achieved anatomic stabilization and there was no postoperative bleeding or recurrence in the follow-up.

Conclusion

The management of the basal ganglia and thalamic AVMs is a great challenge, which needs multimodal individualized treatment to improve the chances of radiographic cure and good outcomes. Endovascular therapy is safe and effective in the treatment of cerebral AVMs particularly for deep-seated AVMs such as the basal ganglia and thalamus. Our results demonstrate a high rate of anatomic obliteration with an acceptable rate of complications in the endovascular treatment of these vasculopathies via a transarterial approach or a transvenous approach.

Stereotactic Radiosurgery Provides Long-Term Safety for Patients With Arteriovenous Malformations in the Diencephalon and Brainstem: The Optimal Dose Selection and Long-Term Outcomes

BACKGROUND

Arteriovenous malformations (AVMs) of the diencephalon (DC) and brainstem (BS) are difficult to treat. Stereotactic radiosurgery (SRS) is a reasonable option; however, an optimal radiosurgical dose needs to be established to optimize long-term outcomes.

OBJECTIVE

To evaluate dose-dependent long-term outcomes of SRS for DC/BS-AVMs.

METHODS

We retrospectively analyzed the long-term outcomes of 118 patients who had SRS-treated DC/BS-AVMs. The outcomes included post-SRS hemorrhage, AVM obliteration, neurological outcomes, and disease-specific survival. According to margin doses, the patients were classified into low (<18 Gy), medium (18-20 Gy), and high (>20 Gy) dose groups.

RESULTS

SRS reduced the annual hemorrhage rate from 8.6% to 1.6% before obliteration and 0.0% after obliteration. The cumulative hemorrhage rate in the low dose group was likely to be higher than that in the other groups ( P = .113). The cumulative obliteration rates in the entire cohort were 74% and 83% at 5 and 10 years, respectively, and were significantly lower in the low dose group than in the other groups (vs medium dose: P = .027, vs high dose: P = .016). Multivariate analyses demonstrated that low dose SRS was significantly associated with worse obliteration rates (hazard ratio 0.18, 95% CI 0.04-0.79; P = .023).

CONCLUSION

SRS with a margin dose of 18 to 20 Gy for DC/BS-AVMs may be optimal, providing a higher obliteration rate and lower risk of post-SRS hemorrhage than lower dose SRS. Dose reduction to <18 Gy should only be optional when higher doses are intolerable.

Comparison of management approaches in deep-seated intracranial arteriovenous malformations: Does treatment improve outcome?

Deep-seated intracranial arteriovenous malformations (AVMs) represent a subset of AVMs characterized by variably reported outcomes regarding the risk of hemorrhage, microsurgical complications, and response to stereotactic radiosurgery (SRS). We aimed to compare outcomes of microsurgery, SRS, endovascular therapy, and conservative follow-up in deep-seated AVMs. A prospectively maintained database of AVM patients (1990-2017) was queried to identify patients with ruptured and unruptured deep-seated AVMs (extension into thalamus, basal ganglia, or brainstem). Comparisons of hemorrhage-free survival and poor functional outcome (modified Rankin scale [mRS] > 2) were performed between conservative management, microsurgery (±pre-procedural embolization), SRS (±pre-procedural embolization), and embolization utilizing multivariable Cox and logistic regression analyses controlling for univariable factors with p < 0.05. Of 789 AVM patients, 102 had deep-seated AVMs (conservative: 34; microsurgery: 6; SRS: 54; embolization: 8). Mean follow-up time was 6.1 years and did not differ significantly between management groups (p = 0.393). Complete obliteration was achieved in 49% of SRS patients. Upon multivariable analysis controlling for baseline rupture with conservative management as a reference group, embolization was associated with an increased hazard of hemorrhage (HR = 6.2, 95%CI [1.1-40.0], p = 0.037), while microsurgery (p = 0.118) and SRS (p = 0.167) provided no significant protection from hemorrhage. Controlling for baseline mRS, microsurgery was associated with an increased risk of poor outcome (OR = 9.2[1.2-68.3], p = 0.030), while SRS (p = 0.557) and embolization (p = 0.541) did not differ significantly from conservative management. Deep AVMs harbor a high risk of hemorrhage, but the benefit from intervention Remains uncertain. SRS may be a relatively more effective approach if interventional therapy is indicated.

The Thalamic Arteriovenous Malformations Have Better Prognosis than Basal Ganglia Malformations Regarding Obliteration: Prognostic Factors Analysis

BACKGROUND

Arteriovenous malformations (AVMs) are rare vascular congenital lesions that affect mainly patients during their productive years of life. In order to obtain a better quality of life for patients with this disease, a multidisciplinary approach is recommended. Radiosurgery is one of the treatment modalities available for AVMs, but many factors may influence the effectiveness of this strategy. Classically, it has been said that deep-seated lesions have a particular behavior compared with AVMs in other regions, but a differentiation between thalamic lesions and those located in the basal ganglia has not been made.

METHODS

Institutional records for central core AVMs treated with radiosurgery between January 2004 and January 2014 were retrospectively analyzed. Brainstem lesions were excluded from the analysis.

RESULTS

Forty-nine patients with deep-seated AVMs were included. Forty-three (87.8%) were located in the thalamus and 6 (12.2%) in the area of basal ganglia. The nidus mean volume was 4.1 cm³ (SD: 4.1), the maximum diameter mean was of 19.5 mm (SD: 8.0). The prescription dose was 18.2 Gy (SD: 2.1), and the follow-up time was 75.8 months (SD: 32.5). There was a greater obliteration rate in thalamic AVMs compared with those located in the basal ganglia: 81.4% versus 33.3% (P = 0.026), respectively. There was no association between categorical variables and obliteration rate.

CONCLUSIONS

Stereotactic radiosurgery is a good option for patients with thalamic and basal ganglia AVMs, but a multidisciplinary approach to decision-making is mandatory in order to achieve the best results.

Microsurgery for Spetzler-Martin Grade I-III Arteriovenous Malformations: Analysis of Surgical Results and Correlation of Lawton-Young Supplementary Grade and Supplemented Spetzler-Martin Score with Functional Outcome

OBJECTIVE

To analyze the results of microsurgery for Spetzler-Martin (SM) grade I-III AVMs and evaluate the correlation of the Lawton-Young (LY) supplementary grade, supplemented Spetzler-Martin (SM-Supp/combined) score with the functional outcome.

METHODS

A total of 42 patients with SM grade I-III AVMs who had undergone surgery at our institute during a 3-year period (June 2013 to May 2016) were included in the present study.

RESULTS

All 42 patients had undergone primary surgery without previous embolization. Three patients (7.1%) had died due to surgical site hematoma in the postoperative period. One patient was lost to follow-up. The mean follow-up period for the remaining patients was 27 ± 14 months (range, 12-62 months). At the final follow-up examination of ≥12 months (FFU), 92.7% of the patients had a good outcome (modified Rankin scale [mRS] score ≤1), with an improved or unchanged mRS score in 87.8%. An AVM size >3 cm, diffuse AVM, SM grade III, and SM-Supp score >5 were associated with worsened mRS score at discharge and FFU. Higher LY grade (IV and V), eloquent AVM location, deep venous drainage, age >40 years, and unruptured presentation were not associated with worsened mRS score at both discharge and FFU. Of the 20 ARUBA-eligible patients, 19 (95%) had good outcomes. Postoperative angiograms for 39 patients revealed complete excision of the AVM in 37 (94.9%) and a residual AVM in 2 (5.1%).

CONCLUSIONS

High cure rates and excellent clinical outcomes can be expected with microsurgery for most patients with SM grade I-III AVMs. An AVM size >3 cm, diffuse AVM nidus, SM grade III, and SM-Supp score >5 are associated with postoperative worsening of functional scores in patients with SM grade I-III AVMs.

Patterns of Failure After Linear Accelerator Radiosurgery for Cerebral Arteriovenous Malformations

BACKGROUND

Numerous studies have assessed the predictive factors for the arteriovenous malformation (AVM) response to stereotactic radiosurgery (SRS). However, only a few have discussed the causes of failure. The aim of the present study was to evaluate the patterns of failure in patients with AVM who had undergone linear accelerator SRS.

METHODS

We performed a retrospective analysis of 288 patients who had undergone linear accelerator SRS in our institution from 1995 to 2011. Failure was defined from the findings of the follow-up angiogram at 5 years, with failure identified in 44 patients. The distribution of causes was estimated using a descriptive analysis of literature-based causes, including a minimal margin dose of <18 Gy, a residual nidus outside the initial targeted volume, previous embolization, recanalization, and the size of the target volume. We also analyzed the associations among the causes.

RESULTS

Incomplete nidus identification (41%) and previous embolization (77%) were the most frequently observed conditions in patients with failure. Patients who had undergone previous embolization, for whom the cause of failure had always been identified (P = 0.001), were younger (P = 0.004) and had had a larger nidus volume (P = 0.025). Recanalization was rare (5 of 34 patients) and had occurred exclusively in women (P = 0.048). Larger nidus volumes were less frequent (mean, 2.18 ± 2.2 cm³; range, 0.13-10.8 cm³) and had been observed mainly in women when >2 cm³ (P = 0.012). An insufficient dose was observed in 9 patients and had occurred in the case of a larger volume (P = 0.031), which had resulted in dosimetry constraints in 3 patients and treatment in the vicinity of eloquent zones in 6 patients. No known cause was found in 5 patients, 4 of whom had had a low Spetzler-Martin grade (I and II; P = 0.003), suggestive of radioresistance.

CONCLUSION

The results of our detailed analysis have highlighted the distribution of the causes of failure and the potential role of radioresistance in treatment failure.

Short Term Effectiveness of Gamma Knife Radiosurgery in the Management of Brain Arteriovenous Malformation

AIM:

To evaluate the short-term effectiveness of Gamma knife radiosurgery as a modality of treatment of brain arteriovenous malformation.

METHODS:

Sixty-three patients with arteriovenous brain malformations underwent Gamma knife radiosurgery included in this prospective study between April 2017 and September 2018 with clinical and radiological with MRI follow up was done at three months and six months post-Gamma knife radiosurgery. By the end of the 12th-month post-Gamma knife radiosurgery, the patients were re-evaluated using digital subtraction angiography co-registered with M.R.I. During the 12 months follow up, CT scan or MRI was done at any time if any one of the patients' condition deteriorated or developed signs and symptoms of complications. The mean volume of the arteriovenous malformations treated was 26.0 ± 5 cm³ (range 12.5–39.5 cm³) in The Neurosciences Hospital, Baghdad/Iraq.

RESULTS:

By the end of the 12th month of follow up, the overall obliteration of the arteriovenous malformations was seen in six patients only (9.5%), while shrinkage was noticed in 57 patients (90.5%). Improvement or clinical stability was found in 24 out of 39 patients (61.5%) presented with epilepsy as a chief complaint before Gamma knife radiosurgery and 21 out of 24 patients (87.0%) complained of a headache before Gamma knife radiosurgery. Post-Gamma knife radiosurgery bleeding was found in only three patients (5.0%).

CONCLUSION:

Even with the short term follow up, Gamma knife radiosurgery has an excellent clinical outcome in most patients with arteriovenous brain malformations. The clinical symptoms like headache and seizure were either diminished or controlled with the same medical treatment dose before Gamma knife radiosurgery. Long term clinical and radiological follow up is recommended.

Multimodal management of arteriovenous malformations of the basal ganglia and thalamus: factors affecting obliteration and outcome

OBJECTIVE

Arteriovenous malformations (AVMs) of the basal ganglia and thalamus are particularly difficult lesions to treat, accounting for 3%-13% of all AVMs in surgical series and 23%-44% of malformations in radiosurgery series. The goal of this study was to report the results of multimodal management of basal ganglia and thalamic AVMs and investigate the factors that influence radiographic cure and good clinical outcomes.

METHODS

This study was a retrospective analysis of a prospectively maintained database of all patients treated at the authors' institution. Clinical, radiological, follow-up, and outcome data were analyzed. Univariate and multivariate analyses were conducted to explore the influence of various factors on outcome.

RESULTS

The results and data analysis pertaining to 123 patients treated over 32 years are presented. In this cohort, radiographic cure was achieved in 50.9% of the patients. Seventy-five percent of patients had good clinical outcomes (stable or improved performance scores), whereas 25% worsened after treatment. Inclusion of surgery and radiosurgery independently predicted obliteration, whereas nidus diameter and volume predicted clinical outcomes. Nidus volume/diameter and inclusion of surgery predicted the optimal outcome, i.e., good clinical outcomes with lesion obliteration.

CONCLUSIONS

Good outcomes are possible with multimodal treatment in these complex patients. Increasing size and, by extension, higher Spetzler-Martin grade are associated with worse outcomes. Inclusion of multiple modalities of treatment as indicated could improve the chances of radiographic cure and good outcomes.

Brainstem arteriovenous malformations: lesion characteristics and treatment outcomes

OBJECTIVE

Brainstem arteriovenous malformations (AVMs) are rare lesions that are difficult to diagnose and treat. They are often more aggressive in their behavior when compared with their supratentorial counterparts. The consequence of a brainstem hemorrhage is often devastating, and many patients are in poor neurological status at presentation. The authors examine the factors associated with angiographically confirmed cure and those affecting management outcomes for these complex lesions.

METHODS

This was a retrospective analysis of data gathered from the prospectively maintained Stanford AVM database. Lesions were grouped based on their location in the brainstem (medulla, pons, or midbrain) and the quadrant they occupied. Angiographic cure was dichotomized as completely obliterated or not, and functional outcome was dichotomized as either independent or not independent at last follow-up.

RESULTS

Over a 23-year period, 39 lesions were treated. Of these, 3 were located in the medulla, 14 in the pons, and 22 in the midbrain. At presentation, 92% of the patients had hemorrhage, and only 43.6% were functionally independent. Surgery resulted in the best radiographic cure rates, with a morbidity rate of 12.5%. In all, 53% of patients either improved or remained stable after surgery. Absence of residual nidus and female sex correlated with better outcomes.

CONCLUSIONS

Brainstem AVMs usually present with hemorrhage. Surgery offers the best chance of cure, either in isolation or in combination with other modalities as appropriate.

Stereotactic Radiosurgery for Brainstem Arteriovenous Malformations: A Multicenter Study

BACKGROUND

The management of brainstem arteriovenous malformations (bAVMs) is a formidable challenge. bAVMs harbor higher morbidity and mortality compared to other locations.

OBJECTIVE

To review the outcomes following stereotactic radiosurgery (SRS) of bAVMs in a multicenter study.

METHODS

Six medical centers contributed data from 205 patients through the International Gamma Knife Research Foundation. Median age was 32 yr (6-81). Median nidus volume was 1.4 mL (0.1-69 mL). Favorable outcome (FO) was defined as AVM obliteration and no post-treatment hemorrhage or permanent symptomatic radiation-induced complications.

RESULTS

Overall obliteration was reported in 65.4% (n = 134) at a mean follow-up of 69 mo. Obliteration was angiographically proven in 53.2% (n = 109) and on MRA in 12.2% (n = 25). Actuarial rate of obliteration at 2, 3, 5, 7, and 10 yr after SRS was 24.5%, 43.3%, 62.3%, 73%, and 81.8% respectively. Patients treated with a margin dose &gt;20 Gy were more likely to achieve obliteration (P = .001). Obliteration occurred earlier in patients who received a higher prescribed margin dose (P = .05) and maximum dose (P = .041). Post-SRS hemorrhage occurred in 8.8% (n = 18). Annual postgamma knife latency period hemorrhage was 1.5%. Radiation-induced complications were radiologically evident in 35.6% (n = 73), symptomatic in 14.6% (n = 30), and permanent in 14.6% (n = 30, which included long-tract signs and new cranial nerve deficits). FO was achieved in 64.4% (n = 132). Predictors of an FO were a higher Virginia radiosurgery AVM scale score (P = .003), prior hemorrhage (P = .045), and a lower prescribed maximum dose (P = .006).

CONCLUSION

SRS for bAVMs results in obliteration and avoids permanent complications in the majority of patients.

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.

Brainstem arteriovenous malformations: anatomical subtypes, assessment of "occlusion in situ" technique, and microsurgical results

OBJECT

The surgical management of brainstem arteriovenous malformations (AVMs) might benefit from the definition of anatomical subtypes and refinements of resection techniques. Many brainstem AVMs sit extrinsically on pia mater rather than intrinsically in the parenchyma, allowing treatment by occluding feeding arteries circumferentially, interrupting draining veins after arteriovenous shunting is eliminated, and leaving the obliterated nidus behind. The authors report here the largest series of brainstem AVMs to define 6 subtypes, assess this "occlusion in situ" technique, and analyze the microsurgical results.

METHODS

Brainstem AVMs were categorized as 1 of 6 types: anterior midbrain, posterior midbrain, anterior pontine, lateral pontine, anterior medullary, and lateral medullary AVMs. Data from a prospectively maintained AVM registry were reviewed to evaluate multidisciplinary treatment results.

RESULTS

During a 15-year period, the authors treated 29 patients with brainstem AVMs located in the midbrain (1 anterior and 6 posterior), pons (6 anterior and 7 lateral), and medulla (1 anterior and 8 lateral). The nidus was pial in 26 cases and parenchymal in 3 cases. Twenty-three patients (79%) presented with hemorrhage. Brainstem AVMs were either resected (18 patients, 62%) or occluded in situ (11 patients, 38%). All lateral pontine AVMs were resected, and the occlusion in situ rate was highest with anterior pontine AVMs (83%). Angiography confirmed complete obliteration in 26 patients (89.6%). The surgical mortality rate was 6.9%, and the rate of permanent neurological deterioration was 13.8%. At follow-up (mean 1.3 years), good outcomes (modified Rankin Scale [mRS] score ≤ 2) were observed in 18 patients (66.7%) and poor outcomes (mRS score of 3-5) were observed in 9 patients (33.3%). The mRS scores in 21 patients (77.8%) were unchanged or improved. The best outcomes were observed with lateral pontine (100%) and lateral medullary (75%) AVMs, and the rate of worsening/death was greatest with posterior midbrain and anterior pontine AVMs (50% each).

CONCLUSIONS

Brainstem AVMs can be differentiated by their location in the brainstem (midbrain, pons, or medulla) and the surface on which they are based (anterior, posterior, or lateral). Anatomical subtypes can help the neurosurgeon determine how to advise patients, with lateral subtypes being a favorable surgical indication along with extrinsic pial location and hemorrhagic presentation. Most AVMs are dissected with the intention to resect them, and occlusion in situ is reserved for those AVMs that do not separate cleanly from the brainstem, that penetrate into the parenchyma, or are more anterior in location, where it is difficult to visualize and preserve perforating arteries (anterior pontine and lateral medullary AVMs). Although surgical morbidity is considerable, surgery results in a better obliteration rate than nonoperative management and is indicated in highly selected patients with high rerupture risks.

A treatment paradigm for high-grade brain arteriovenous malformations: volume-staged radiosurgical downgrading followed by microsurgical resection

OBJECT

The surgical treatment of many large arteriovenous malformations (AVMs) is associated with substantial risks, and many are considered inoperable. Furthermore, AVMs larger than 3 cm in diameter are not usually treated with conventional single-session radiosurgery encompassing the entire AVM volume. Volume-staged stereotactic radiosurgery (VS-SRS) is an option for large AVMs, but it has mixed results. The authors report on a series of patients with high-grade AVMs who underwent multiple VS-SRS sessions with resultant downgrading of the AVMs, followed by resection.

METHODS

A cohort of patients was retrieved from a single-institution AVM patient registry consisting of prospectively collected data. VS-SRS was performed as a planned intentional treatment. Surgery was considered as salvage therapy in select patients.

RESULTS

Sixteen AVMs underwent VS-SRS followed by surgery. Four AVMs presented with rupture. The mean patient age was 25.3 years (range 13–54 years). The average initial Spetzler-Martin grade before any treatment was 4, while the average supplemented Spetzler-Martin grade (Spetzler-Martin plus Lawton-Young) was 7.1. The average AVM size in maximum dimension was 5.9 cm (range 3.3–10 cm). All AVMs were supratentorial in location and all except one were in eloquent areas of the brain, with 7 involving primary motor cortex. The mean number of VS-SRS sessions was 2.7 (range 2–5 sessions). The mean interval between first VS-SRS session and resection was 5.7 years. There were 4 hemorrhages that occurred after VS-SRS. The average Spetzler-Martin grade was reduced to 2.5 (downgrade, −1.5) and the average supplemented Spetzler-Martin grade was reduced to 5.6 (downgrade, −1.5). The maximum AVM size was reduced to an average of 3.0 cm (downsize = −2.9 cm). The mean modified Rankin Scale (mRS) scores were 1.2, 2.3, and 2.2 before VS-SRS, before surgery, and at last follow-up, respectively (mean follow-up, 6.9 years). Fifteen AVMs were cured after surgery. Ten patients had good outcomes at last follow-up (7 with mRS Score 0 or 1, and 3 with mRS Score 2). There were 2 deaths (both mRS Score 1 before treatment) and 4 patients with mRS Score 3 outcome (from mRS Scores 0, 1, and 2 [n = 2]).

CONCLUSIONS

Volume-staged SRS can downgrade AVMs, transforming high-grade AVMs (initially considered inoperable) into operable AVMs with acceptable surgical risks. This treatment paradigm offers an alternative to conservative observation for young patients with unruptured AVMs and long life expectancy, where the risk of hemorrhage is substantial. Difficult AVMs were cured in 15 patients. Surgical morbidity associated with downgraded AVMs is reduced to that of postradiosurgical/preoperative supplemented Spetzler-Martin grades, not their initial AVM grades.

Deep arteriovenous malformations in the Basal Ganglia, thalamus, and insula: microsurgical management, techniques, and results

BACKGROUND

Arteriovenous malformations (AVMs) in the basal ganglia, thalamus, and insula are considered inoperable given their depth, eloquence, and limited surgical exposure. Although many neurosurgeons opt for radiosurgery or observation, others have challenged the belief that deep AVMs are inoperable. Further discussion of patient selection, technique, and multimodality management is needed.

OBJECTIVE

To describe and discuss the technical considerations of microsurgical resection for deep-seated AVMs.

METHODS

Patients with deep AVMs who underwent surgery during a 14-year period were reviewed through the use of a prospective AVM registry.

RESULTS

Microsurgery was performed in 48 patients with AVMs in the basal ganglia (n=10), thalamus (n=13), or insula (n=25). The most common Spetzler-Martin grade was III- (68%). Surgical approaches included transsylvian (67%), transcallosal (19%), and transcortical (15%). Complete resection was achieved in 34 patients (71%), and patients with incomplete resection were treated with radiosurgery. Forty-five patients (94%) were improved or unchanged (mean follow-up, 1.6 years).

CONCLUSION

This experience advances the notion that select deep AVMs may be operable lesions. Patients were highly selected for small size, hemorrhagic presentation, young age, and compactness-factors embodied in the Spetzler-Martin and Supplementary grading systems. Overall, 10 different approaches were used, exploiting direct, transcortical corridors created by hemorrhage or maximizing anatomic corridors through subarachnoid spaces and ventricles that minimize brain transgression. The same cautious attitude exercised in selecting patients for surgery was also exercised in deciding extent of resection, opting for incomplete resection and radiosurgery more than with other AVMs to prioritize neurological outcomes.

Deep arteriovenous malformations in the basal ganglia, thalamus, and insula: multimodality management, patient selection, and results

OBJECTIVE

This study sought to describe a single institution's experience treating arteriovenous malformations (AVMs) of the basal ganglia, thalamus, and insula in a multimodal fashion.

METHODS

We conducted a retrospective review of all deep AVMs treated at our institution between 1997 and 2011 with attention to patient selection, treatment strategies, and radiographic and functional outcomes.

RESULTS

A total of 97 patients underwent initial treatment at our institution. 64% presented with hemorrhage with 29% located in the basal ganglia, 41% in the thalamus, and 30% in the insula. 80% were Spetzler-Martin grade III-IV. Initial treatment was microsurgical resection in 42%, stereotactic radiosurgery (SRS) in 45%, and observation in 12%. Radiographic cure was achieved in 54% after initial surgical or SRS treatment (71% and 23%, respectively) and in 63% after subsequent treatments, with good functional outcomes in 78% (median follow-up 2.2 years). Multivariate logistic regression analysis revealed treatment group and age as factors associated with radiographic cure, whereas Spetzler-Martin score and time to follow-up were significantly associated with improved/unchanged functional status at time of last follow-up. Posttreatment hemorrhage occurred in 11% (7% of surgical and 18% of SRS patients).

CONCLUSIONS

Modern treatment of deep AVMs includes a multidisciplinary approach utilizing microsurgery, SRS, embolization, and observation. Supplementary grading adds meaningfully to traditional Spetzler-Martin grading to guide patient selection. Surgical resection is more likely to result in obliteration compared with SRS, and is associated with satisfactory results in carefully selected patients.

Long-term outcomes of gamma knife surgery for posterior fossa arteriovenous malformations

The long-term outcomes of gamma knife surgery (GKS) in patients with posterior fossa arteriovenous malformations (AVMs) were retrospectively analyzed in 82 patients followed up for more than 5 years to evaluate the efficacy and safety. The median AVM volume at GKS was 0.95 cm³. The prescribed dose to the AVM margin was median 18 Gy with 1–18 isocenters. The actual complete AVM obliteration rate was 58.5% at 3 years and 78.0% at 5 years. The significant factors for higher complete obliteration rate were younger patient age and smaller maximum/minimum nidus diameter ratio. Two patients experienced hemorrhage caused by residual AVM rupture at 4 and 49 months. Twenty patients developed peri-nidal edema as an adverse radiation-induced reaction at median 13 months. One patient developed radiation-induced necrosis at 6.8 years. Neurological complication was observed in 12 patients and 6 patients remained with neurological dysfunction permanently. Larger nidus volume and location adjacent to an eloquent area significantly increased the risk of neurological complication. Pittsburgh radiosurgery-based AVM grading scale was significantly correlated with the outcome of neurological symptoms after GKS. GKS achieved acceptable and complete obliteration rate for posterior fossa AVM with relatively low risk of morbidity on neuroimaging and neurological symptoms for the long-term period after treatment. We recommend conformable and selective treatment planning to achieve both obliteration of the AVM nidus and preservation of neurological function.

Hypofractionated stereotactic radiosurgery in a large bilateral thalamic and Basal Ganglia arteriovenous malformation

Purpose. Arteriovenous malformations (AVMs) in the basal ganglia and thalamus have a more aggressive natural history with a higher morbidity and mortality than AVMs in other locations. Optimal treatment—complete obliteration without new neurological deficits—is often challenging. We present a patient with a large bilateral basal ganglia and thalamic AVM successfully treated with hypofractionated stereotactic radiosurgery (HFSRS) with intensity modulated radiotherapy (IMRT). Methods. The patient was treated with hypofractionated stereotactic radiosurgery to 30 Gy at margin in 5 fractions of 9 static fields with a minimultileaf collimator and intensity modulated radiotherapy. Results. At 10 months following treatment, digital subtraction angiography showed complete obliteration of the AVM. Conclusions. Large bilateral thalamic and basal ganglia AVMs can be successfully treated with complete obliteration by HFSRS with IMRT with relatively limited toxicity. Appropriate caution is recommended.

[Linear accelerator radiosurgery for brainstem arteriovenous malformations. Long-term results]

OBJECTIVE

Arteriovenous malformations (AVM) in the brainstem carry a high risk of recurrent haemorrhage, mortality and morbidity. Treatment options are limited and mainly based on stereotactic radiosurgery. We studied the results of our series of brainstem AVM treated with linear accelerator (LINAC) and with a long-term follow-up.

METHODS

We retrospectively analysed the clinical and radiological data of 41 consecutive patients with brainstem AVM treated by radiosurgery with a 6MV linear accelerator between 1992 and 2010. Twenty five lesions were located in the mesencephalon, 14 in the pons, one in the medulla oblongata and one was bulbopontine. We analysed the treatment results in relation to survival, rate of radiological obliteration, rebleeding, and treatment toxicity.

RESULTS

The obliteration rate confirmed by angiography/MRA was 59.5% on 38 controlled patients. The mean follow-up period was 61 months (range: 6.7-178) and the margin dose was 14Gy in most treatments. Up to 39% of patients received more than one radiosurgery procedure to achieve closure of the malformation. No statistical correlation was found with the margin dose, presence of pretreatment haemorrhage, nidus diameter or score on the Pollock-Flickinger grading system. The annual haemorrhage rate after radiosurgery was 3.2%. Three patients died from rebleeding and actuarial survival rate was 88% at 5 and 10 years after treatment. Four patients suffered new transient neurological deficits due to toxicity, and only one presented a permanent deficit (2.6%).

CONCLUSIONS

Nidus obliteration in brainstem AVM must be achieved according to three main criteria: maximum obliteration rate forced by the high rate of rebleeding, minimal morbidity given its critical location, and the greatest possible accuracy. Stereotactic radiosurgery with our moderate-dose protocol, which we believe achieved these three premises, may become an elective therapeutic modality for these patients.

Embolization and radiosurgery for arteriovenous malformations

The treatment of arteriovenous malformations (AVMs) requires a multidisciplinary management including microsurgery, endovascular embolization, and stereotactic radiosurgery (SRS). This article reviews the recent advancements in the multimodality treatment of patients with AVMs using endovascular neurosurgery and SRS. We describe the natural history of AVMs and the role of endovascular and radiosurgical treatment as well as their interplay in the management of these complex vascular lesions. Also, we present some representative cases treated at our institution.

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.

Stereotactic radiosurgery for arteriovenous malformations, Part 5: management of brainstem arteriovenous malformations

Object

In this paper, the authors' goal was to define the long-term outcomes and risks of stereotactic radiosurgery (SRS) for arteriovenous malformations (AVMs) of the medulla, pons, and midbrain.

Methods

Between 1987 and 2006, the authors performed Gamma Knife surgery in 996 patients with brain AVMs; 67 patients had AVMs in the brainstem. In this series, 51 patients (76%) had a prior hemorrhage. The median target volume was 1.4 cm3 (range 0.1–13.4 cm3). The median margin dose was 20 Gy (range 14–25.6 Gy).

Results

Obliteration of the AVMs was eventually documented in 35 patients at a median follow-up of 73 months (range 6–269 months). The actuarial rates of documentation of total obliteration were 41%, 70%, 70%, and 76% at 3, 4, 5, and 10 years, respectively. Higher rates of AVM obliteration were associated only with a higher margin dose. Four patients (6%) suffered a hemorrhage during the latency period, and 2 patients died. The rate of AVM hemorrhage after SRS was 3.0%, 3.0%, and 5.8% at 1, 5, and 10 years, respectively. The overall annual hemorrhage rate was 1.9%. Permanent neurological deficits due to adverse radiation effects (AREs) developed in 7 patients (10%) after SRS, and a delayed cyst developed in 2 patients (3%). One patient died at an outside institution with symptoms of AREs and unrecognized hydrocephalus. Higher 12-Gy volumes and higher Spetzler-Martin grades were associated with a higher risk of symptomatic AREs. Ten of 22 patients who had ocular dysfunction before SRS had improvement, 9 were unchanged, and 3 were worse due to AREs. Eight of 14 patients who had hemiparesis before SRS improved, 5 were unchanged, and 1 was worse.

Conclusions

Although hemorrhage after obliteration did not occur in this series, patients remained at risk during the latency interval until obliteration occurred. Thirty-eight percent of the patients who had neurological deficits due to prior hemorrhage improved. Higher dose delivery in association with conformal and highly selective SRS is required for safe and effective radiosurgery.

Stereotactic Radiosurgery for Arteriovenous Malformations Located in Deep Critical Regions

BACKGROUND:

Radiosurgery is widely used to treat deep eloquent arteriovenous malformations (AVMs).

OBJECTIVE:

To evaluate how anatomic location, AVM size, and treatment parameters define outcome.

METHODS:

Retrospective analysis of 356 thalamic/basal ganglia and 160 brainstem AVMs treated with gamma knife radiosurgery.

RESULTS:

Median volume was 2 cm3 (range, 0.02–50) for supratentorial and 0.5 cm3 (range, 0.01–40) for brainstem AVMs; the marginal treatment doses were 17.5 to 25 Gy. After single treatment, obliteration was achieved in 65% of the brainstem, in 69% of the supratentorial, and 40% of the peritectal AVMs. Obliteration of lesions &lt;4 cm3 was better in the brainstem (70%) and in the supratentorium (80%), but not in the peritectal region (40%). Complications were rare (6%–15%) and mild (⩽modified Rankin scale [MRS] 2). Rebleed rate increased with size, but was not higher than before treatment. AVMs &gt;4 cm3 in the brainstem were treated with unacceptable morbidity and low cure rate. Obliteration of large supratentorial AVMs was 65% to 47% with more complications ≥MRS3. Repeat radiosurgical treatment led to obliteration in 66% of the cases with minor morbidity.

CONCLUSION:

Deep eloquent AVMs &lt;4 cm3 can be treated safely and effectively with radiosurgery. Obliteration of peritectal AVMs is significantly lower after a single treatment. However, morbidity is low, and repeat treatment leads to good obliteration. Radiosurgical treatment &gt;4 cm3 in the brainstem is not recommended. Supratentorial deep AVMs &gt;8 cm3 can be treated with radiosurgery with higher risk and lower obliteration rate. However, these lesions are difficult to treat with other treatment modalities, and a 50% success rate makes radiosurgery a good alternative even in this challenging group.

The predictive value of 3D time-of-flight MR angiography in assessment of brain arteriovenous malformation obliteration after radiosurgery

BACKGROUND AND PURPOSE

The purpose of radiosurgery of bAVMs is complete angiographic obliteration of its nidus. We assessed the diagnostic accuracy of 1.5T T2-weighted MR imaging and TOF-MRA images for detecting nidus obliteration after radiosurgery.

MATERIALS AND METHODS

The pre- and postradiosurgery MR images and DSA images from 120 patients who were radiosurgically treated for a bAVM were re-evaluated by 2 observers for patency of the nidus (preradiosurgery) and obliteration (postradiosurgery: final follow-up MR imaging), by using a 3-point scale of confidence. Consensus reading of the DSA after radiosurgery was considered the criterion standard for obliteration. Sensitivity, specificity, PPVs, and NPVs, and overall diagnostic performance by using ROC were determined.

RESULTS

Mean bAVM volume during radiosurgery was 3.4 mL (95% CI, 2.6-4.3 mL). Sixty-six patients (55%) had undergone previous endovascular embolization. The mean intervals between radiosurgery and follow-up MR imaging and for DSA, respectively, were 35.6 months (95% CI, 32.3-38.9 months) and 42.1 months (95% CI, 40.3-44.0 months). With ROC, an area under curve of 0.81-0.83 was found. PPVs of final follow-up MR-imaging for definitive obliteration varied between 0.89 [corrected] and 0.95. NPV was 0.52 [corrected] . An average false-positive rate, meaning overestimation of nidus obliteration of 0.10 [corrected] and an average false-negative rate, meaning underestimation of nidus obliteration of 0.42 [corrected] were found.

CONCLUSIONS

MRA is insufficient to diagnose obliteration in the follow-up of bAVMs after radiosurgery. A remaining nidus diameter <10 mm seems to be the major limiting factor for reliable assessment of obliteration. We highly recommend follow-up DSA for definitive diagnosis of complete obliteration.

Stereotactic radiosurgery for arteriovenous malformations, Part 4: management of basal ganglia and thalamus arteriovenous malformations

OBJECT

The authors conducted a study to define the long-term outcomes and risks of stereotactic radiosurgery (SRS) for arteriovenous malformations (AVMs) of the basal ganglia and thalamus.

METHODS

Between 1987 and 2006, the authors performed Gamma Knife surgery in 996 patients with brain AVMs; 56 patients had AVMs of the basal ganglia and 77 had AVMs of the thalamus. In this series, 113 (85%) of 133 patients had a prior hemorrhage. The median target volume was 2.7 cm(3) (range 0.1-20.7 cm(3)) and the median margin dose was 20 Gy (range 15-25 Gy).

RESULTS

Obliteration of the AVM eventually was documented on MR imaging in 78 patients and on angiography in 63 patients in a median follow-up period of 61 months (range 2-265 months). The actuarial rates documenting total obliteration after radiosurgery were 57%, 70%, 72%, and 72% at 3, 4, 5, and 10 years, respectively. Factors associated with a higher rate of AVM obliteration included AVMs located in the basal ganglia, a smaller target volume, a smaller maximum diameter, and a higher margin dose. Fifteen (11%) of 133 patients suffered a hemorrhage during the latency period and 7 patients died. The rate of post-SRS AVM hemorrhage was 4.5%, 6.2%, 9.0%, 11.2%, and 15.4% at 1, 2, 3, 5, and 10 years, respectively. The overall annual hemorrhage rate was 4.7%. When 5 patients with 7 hemorrhages occurring earlier than 6 months after SRS were removed from this analysis, the annual hemorrhage rate decreased to 2.7%. Larger volume AVMs had a higher risk of hemorrhage after SRS. Permanent neurological deficits due to adverse radiation effects (AREs) developed in 6 patients (4.5%), and in 1 patient a delayed cyst developed 56 months after SRS. No patient died of AREs. Factors associated with a higher risk of symptomatic AREs were larger target volume, larger maximum diameter, lower margin dose, and a higher Pollock-Flickinger score.

CONCLUSIONS

Stereotactic radiosurgery is a gradually effective and relatively safe management option for deep-seated AVMs in the basal ganglia and thalamus. Although hemorrhage after obliteration did not occur in the present series, patients remain at risk during the latency interval between SRS and obliteration. The best candidates for SRS are patients with smaller volume AVMs located in the basal ganglia.

Linac stereotactic radiosurgery for the treatment of small arteriovenous malformations: lower doses can be equally effective

OBJECTIVE

The purpose of this study was to examine the efficacy and toxicity of treating small arteriovenous malformations (AVMs) (≤3 cm in diameter) with a median marginal applied dose of 14 Gy.

METHODS

Two hundred and thirteen patients diagnosed with AVMs were treated between January 1991 and December 2005. Seventy-three percent of the patients had hemorrhaged prior to treatment, 13% had had previous surgery and 19.2% had had previous embolization. The median follow-up duration was 48.1 months.

RESULTS

The Kaplan-Meier analysis estimated that the 36-month obliteration rate was 65.5% for patients undergoing their first stereotactic radiosurgery (SRS) and 68.3% for those undergoing repeated SRS. The Kaplan-Meier analysis estimated the 60-month AVMs obliteration rate for the entire cohort to be 82.4%. The median time to AVM obliteration was 40 ± 2.8 months. We found a statistically significant relationship between the time of obliteration and the following factors: site of the AVMs (sites other than brainstem), a higher prescribed dose and a positive history of previous hemorrhage. Thirteen patients (7.6%) experienced toxicities.

CONCLUSIONS

SRS was an effective and safe treatment for AVMs ≤3 cm in diameter, with acceptable toxicity.

Long-term Outcomes of Stereotactic Radiosurgery for Arteriovenous Malformations in the Thalamus

BACKGROUND

Arteriovenous malformations (AVMs) in the thalamus carry a high risk of hemorrhage. Although stereotactic radiosurgery (SRS) is widely accepted because of the high surgical morbidity and mortality of these lesions, precise long-term outcomes are largely unknown.

OBJECTIVE

To review our experience with SRS for thalamic AVMs based on the latest follow-up data.

METHODS

Forty-eight patients with thalamic AVMs were treated by SRS using the Leksell Gamma Knife and were followed. Long-term outcomes including the obliteration rate, hemorrhage after treatment, and adverse effects were retrospectively analyzed.

RESULTS

The annual hemorrhage rate before SRS was 14%. The mean follow-up period after SRS was 66 months (range 6–198 months). The actuarial obliteration rate confirmed by angiography was 82% at 5 years after treatment, and the annual hemorrhage rate after SRS was 0.36%. Factors associated with higher obliteration rates were previous hemorrhage (P = .004) and treatment using new planning software (P = .001). Persistent worsening of neurological symptoms was observed in 17% and more frequently seen in patients who were treated using older planning software (P = .04) and a higher margin dose (P = .02). The morbidity rate for patients who received treatment planned using new software with a margin dose not more than 20 Gy was 12%.

CONCLUSION

SRS for thalamic AVMs achieved a high obliteration rate and effectively decreased the risk of hemorrhage, with less morbidity compared with other modalities. Longer follow-up to evaluate the risk of delayed complications and the effort to minimize the morbidity is necessary.