Taming the Beast: Treating Associated Aneurysms to Reduce Risk of Hemorrhage After Radiosurgery for Arteriovenous Malformations

El Ahmadieh, Tarek Y.; El Tecle, Najib E.; Stadler, James A. 3rd; Bendok, Bernard R.

doi: 10.1227/01.neu.0000428421.82081.b9
Science Times

Intracranial arteriovenous malformations (AVMs) are an important cause of hemorrhagic stroke in young individuals.1 Advances in microsurgery, radiosurgery, and neurointerventional surgery have revolutionized the approach to these heterogeneous lesions that were once considered too dangerous to treat.2,3 Stereotactic radiosurgery (SRS) provides an avenue to treat select “inoperable AVMs.”4 The main disadvantage of this approach relates to the hemorrhage risk during the latency period.5 Retrospective analyses suggest that associated intracranial aneurysms increase hemorrhagic risk in patients with AVMs.4,6 It has been hypothesized that presence of associated aneurysms increases rehemorrhage risk in AVM patients during the latency period after radiosurgery. To further examine this hypothesis, Kano et al conducted a retrospective analysis of 996 patients whose AVMs were treated with radiosurgery.7 The study focused on assessing the impact of treating associated aneurysms on the risk of rebleeding after radiosurgical treatment of AVMs. The results were published in the October 2012 issue of Stroke.7

Between 1987 and 2006, 996 patients with intracranial AVMs were treated using stereotactic radiosurgery at a single center. Of the total cohort, 407 patients presented with ruptured AVMs of which 45 patients were found to have associated intracranial aneurysms: 34 located in the circle of Willis, 6 in the AVM nidus, and 5 on arterial feeders. Twenty out of the 45 patients with associated aneurysms underwent embolization or microsurgical clipping before SRS (11 patients presented with ruptured aneurysms), whereas the remaining 25 patients had unsecured intracranial aneurysms at the time of treatment. This 25-patient study cohort was matched to a control cohort of patients with AVMs who had no associated aneurysms. The case matching between the 2 groups accounted for basic patient and AVM characteristics, clinical presentation, SRS dosage and target volume, as well as follow-up duration. All patients received SRS treatment using Leksell Gamma Knife (Elekta Instruments, Norcross, GA) at a median margin dose of 20 Gy (13.5-27 Gy). The median maximal diameter of the nidus was 1.9 cm (0.5-4.8 cm) and the median target volume was 2.3 mL (0.1-20.7 mL). The median follow-up period after SRS was 66 months (2-274 months). Complete obliteration of the AVM was defined as the absence of a residual nidus at the time of follow-up angiogram and magnetic resonance imaging (MRI).

Overall complete obliteration rates of AVMs after SRS were reported as: 56% at 3 years, 77% at 4 years, 80% at 5 years, and 82% at 10 years. No significant difference in complete obliteration rates of AVMs was noted for patients with unsecured aneurysms compared to those without associated aneurysms (P = .368). During the latency period, the overall annual rebleeding rate was found to be 3.6% in the first year (total of 407 patients), 1.1% in the second year, 1.6% in the third year, 0.8% between the third and fifth year, 0.7% between the fifth and tenth year, and 0.9% between 10 and 20 years (total of 108 patients). The mortality rate due to AVM rebleeding was 4.2%. No rebleeding was reported following complete obliteration of AVMs.

In their analysis of the rebleeding risk for patients with and without associated intracranial aneurysms, the authors noted a significantly higher rate of rebleeding after SRS for patients with unsecured aneurysms (P = .003). Further, the rate of rebleeding was found to be significantly higher in patients with unsecured aneurysms compared to those who had received endovascular embolization or microsurgical clipping of their aneurysms prior to SRS (P = .033) (Figure 1). Rebleeding was defined as any intracranial bleeding after SRS caused by either the AVM or the aneurysm. In the control cohort (patients with no associated aneurysms), the cumulative risk of rebleeding was 2.8% at 1 year of follow-up, 4.4% at 3 years, and 5.2% at 5 years. In patients with previously embolized or clipped aneurysms, the rebleeding rate was reported to be 0% at 1 year of follow-up, 6.2% at 3 years, and 6.2% at 5 years. On the other hand, the rebleeding rate was 12.2% at 1 year of follow-up, 21.5% at 3 years, and 26.7% at 5 years in patients with unsecured aneurysms.

This important study by Kano et al emphasizes the need to consider associated aneurysms in treatment planning for AVMs eligible for radiosurgery (Figure 2). AVMs should be treated at centers with high level microsurgical, radiosurgical, and neurointerventional expertise. A multimodal approach where the relative merits of all techniques are carefully considered is needed to tackle complex AVMs safely. The excellent study by Kano et al suggests that rehemorrhage after radiosurgery can be reduced if associated aneurysms are treated when this is safe and feasible.

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