Stereotactic radiosurgery of intracranial arteriovenous malformations and the use of the K index in determining treatment dose

Gross Total Resection of a Ruptured Micro-arteriovenous Malformation within the Cerebellar Peduncle: A Case Report and Qualitative Review of the Literature

Deep-seated micro-arteriovenous malformations (micro-AVMs) may pose a challenge for complete yet safe resection. We propose the strategic placement of two to three microaneurysm clips throughout the hemorrhage cavity to successfully localize the micro-AVM nidus via digital subtraction angiography (DSA). We successfully demonstrate this novel method in a 15-year-old adolescent boy with cerebellar intraparenchymal hemorrhage who underwent hematoma evacuation and expansile duraplasty. He was found to have a 1-cm nidus of a micro-AVM with early venous drainage located in the right middle cerebellar peduncle. Five days later, we proceeded to resect the micro-AVM; however, a clear nidus or bleeding source was unable to be localized intraoperatively despite the use of stereotactic neuronavigation. In turn, we placed two mini-aneurysm clips superiorly and inferiorly within the hematoma cavity, which led to successful localization via DSA and complete resection. No surgical complications occurred. The patient completely recovered from right-sided weakness and dysarthria 6 to 12 months postoperatively. Our technique allows for the rapid localization and complete resection of micro-AVM nidi when stereotactic neuronavigation is inadequate.

Microsurgical resection versus stereotactic radiosurgery for low-grade intracranial arteriovenous malformations: A 27-year institutional experience

The role of microsurgery and radiosurgery in the management of low-grade (Spetzler-Martin grade 1 and 2) arteriovenous malformations (AVMs) remains controversial. We aimed to compare outcomes of low-grade AVMs following microsurgery and radiosurgery using a database of AVM patients presenting between 1990 and 2017. Procedure-related complications, obliteration, and functional status at last follow-up were compared between groups. Hemorrhage-free survival was compared using Kaplan-Meier analysis with subgroup analyses by rupture status on presentation. The study involved 233 patients, of which 113 and 120 were treated with microsurgery and radiosurgery, respectively. The complication rates were statistically comparable between both treatment modalities. Mean follow-up time was 5.1 ± 5.2 years. In the complete cohort, there was no significant difference in hemorrhage-free survival between microsurgery and radiosurgery (log-rank p = 0.676, Breslow p = 0.493). When excluding procedure-related hemorrhage and partial resection, hemorrhage-free survival was significantly higher in the surgically treated cohort (log-rank = 0.094, Breslow p = 0.034). The obliteration rate was significantly higher in the surgical cohort (96% vs. 57%, p < 0.001), while functional status was similar. Microsurgery may offer superior hemorrhage-free survival in the early post-treatment period and demonstrates equivalent long-term hemorrhage control and functional outcome at 5 years compared to radiosurgery with nearly complete obliteration rates. Persistent neurologic deficits following microsurgery and symptomatic cerebral edema represent important treatment risks despite low SM grading. Appropriate patient selection even when dealing with low-grade AVMs is advised, as judicious patient selection and emphasis on technical success can minimize procedure-related hemorrhage and the incidence of subtotal resection.

Effects of cone versus multi-leaf collimation on dosimetry and neurotoxicity in patients with small arteriovenous malformations treated by stereotactic radiosurgery

PURPOSE/OBJECTIVE

Linear accelerator (LINAC) based stereotactic radiosurgery (SRS) for arteriovenous malformations (AVMs) is delivered with cone or multileaf collimators (MLCs), and favorable dosimetry is associated with reduced radionecrosis in normal brain tissue. This study aims to determine whether cones or MLCs has better dosimetric characteristics, to predict differences in toxicity.

METHODS

All patients treated for AVMs using LINAC SRS from 2003-2017 were examined retrospectively. Demographic data, volumes of normal tissue exposed to 12Gy (V12Gy[cc]) and 4Gy (V4Gy[cc]), maximal dose, and dose gradient were analyzed. Univariate and multivariate analyses were used to evaluate relationships between collimator type, dosimetric parameters, and toxicity. Propensity score matching was used to adjust for AVM size.

RESULTS

Compared to MLC, cones were independently associated with reduced V12Gy[cc] after propensity score matching (p=0.008) and reduced neurotoxicity (p=0.016). Higher V12Gy[cc] (p=0.0008) and V4Gy[cc] (p=0.002) were associated with increased neurotoxicity.

CONCLUSIONS

Treating AVMs with cone-based SRS over MLC-based SRS may improve dosimetry and reduce toxicities.

Quantification of hemodynamics of cerebral arteriovenous malformations after stereotactic radiosurgery using 4D flow magnetic resonance imaging

Stereotactic radiosurgery (SRS) is used to treat cerebral arteriovenous malformations (AVMs). However, early evaluation of efficacy is difficult as structural magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) often does not demonstrate appreciable changes within the first 6 months. The aim of this study was to evaluate the use of four-dimensional (4D) flow MRI to quantify hemodynamic changes after SRS as early as 2 months. This was a retrospective observational study, which included 14 patients with both pre-SRS and post-SRS imaging obtained at multiple time points from 1 to 27 months after SRS. A 3T MRI Scanner was used to obtain T₂ single-shot fast spin echo, time-of-flight MRA, and postcontrast 4D flow with three-dimensional velocity encoding between 150 and 200 cm/s. Post-hoc two-dimensional cross-sectional flow was measured for the dominant feeding artery, the draining vein, and the corresponding contralateral artery as a control. Measurements were performed by two independent observers, and reproducibility was assessed. Wilcoxon signed-rank tests were used to compare differences in flow, circumference, and pulsatility between the feeding artery and the contralateral artery both before and after SRS; and differences in nidus size and flow and circumference of the feeding artery and draining vein before and after SRS. Arterial flow (L/min) decreased in the primary feeding artery (mean: 0.1 ± 0.07 vs. 0.3 ± 0.2; p < 0.05) and normalized in comparison to the contralateral artery (mean: 0.1 ± 0.07 vs. 0.1 ± 0.07; p = 0.068). Flow decreased in the draining vein (mean: 0.1 ± 0.2 vs. 0.2 ± 0.2; p < 0.05), and the circumference of the draining vein also decreased (mean: 16.1 ± 8.3 vs. 15.7 ± 6.7; p < 0.05). AVM volume decreased after SRS (mean: 45.3 ± 84.8 vs. 38.1 ± 78.7; p < 0.05). However, circumference (mm) of the primary feeding artery remained similar after SRS (mean: 15.7 ± 2.7 vs. 16.1 ± 3.1; p = 0.600). 4D flow may be able to demonstrate early hemodynamic changes in AVMs treated with radiosurgery, and these changes appear to be more pronounced and occur earlier than the structural changes on standard MRI/MRA. Level of Evidence: 4 Technical Efficacy Stage: 1.

Stereotactic Radiosurgery for Brain Arteriovenous Malformations: Evaluation of Obliteration and Review of Associated Predictors

BACKGROUND

High arteriovenous malformation (AVM) obliteration rates have been reported with stereotactic radiosurgery (SRS), and multiple factors have been found to be associated with AVM obliteration. These predictors have been inconsistent throughout studies. We aimed to analyze our experience with linear accelerator (LINAC)-based SRS for brain AVMs, evaluate outcomes, assess factors associated with AVM obliteration and review the various reported predictors of AVM obliteration.

METHODS

Electronic medical records were retrospectively reviewed to identify consecutive patients with brain AVMs treated with SRS over a 27-year period with at least 2 years of follow-up. Logistic regression analysis was performed to identify factors associated with AVM obliteration.

RESULTS

One hundred twenty-eight patients with 142 brain AVMs treated with SRS were included. Mean age was 34.4 years. Fifty-two percent of AVMs were associated with a hemorrhage before SRS, and 14.8% were previously embolized. Mean clinical and angiographic follow-up times were 67.8 months and 58.6 months, respectively. The median Spetzler-Martin grade was 3. Mean maximal AVM diameter was 2.8 cm and mean AVM target volume was 7.4 cm³ with a median radiation dose of 16 Gy. Complete AVM obliteration was achieved in 80.3%. Radiation-related signs and symptoms were encountered in 32.4%, only 4.9% of which consisted of a permanent deficit. Post-SRS AVM-related hemorrhage occurred in 6.3% of cases. In multivariate analysis, factors associated with AVM obliteration included younger patient age (P = .019), male gender (P = .008), smaller AVM diameter (P = .04), smaller AVM target volume (P = .009), smaller isodose surface volume (P = .005), a higher delivered radiation dose (P = .013), and having only one major draining vein (P = .04).

CONCLUSIONS

AVM obliteration with LINAC-based radiosurgery was safe and effective and achieved complete AVM obliteration in about 80% of cases. The most prominent predictors of AVM success included AVM size, AVM volume, radiation dose, number of draining veins and patient age.

Radiosurgery for the management of cerebral arteriovenous malformations

Cerebral arteriovenous malformations (AVMs) are rare, unstable vascular lesions which spontaneously rupture at a rate of approximately 2-4% annually. Stereotactic radiosurgery is a minimally invasive treatment for AVMs, with a favorable risk-to-benefit profile in most patients, with respect to obliteration, hemorrhage, and seizure control. Radiosurgery is ideally suited for small to medium-sized AVMs (diameter <3cm or volume <12cm³) located in deep or eloquent brain regions. Obliteration is ultimately achieved in 70-80% of cases and is directly associated with nidus volume and radiosurgical margin dose. Adverse radiation effects, which appear as T2-weighted hyperintensities on magnetic resonance imaging, develop in 30-40% of patients after AVM radiosurgery, are symptomatic in 10%, and fail to clinically resolve in 2-3%. The risk of AVM hemorrhage may be reduced by radiosurgery, but the hemorrhage risk persists during the latency period between treatment and obliteration. Delayed postradiosurgery cyst formation occurs in 2% of cases and may require surgical treatment. Radiosurgery abolishes or ameliorates seizure activity in the majority of patients with AVM-associated epilepsy and induces de novo seizures in 1-2% of those without preoperative seizures. Strategies for the treatment of large-volume AVMs include neoadjuvant embolization and either dose- or volume-staged radiosurgery.