Gamma Knife^®Radiosurgical Strategy for Pediatric High-Grade Arteriovenous Malformations: Advantages of Staged Radiosurgery Prior to Targeting Nidus Proximal to the Drainer

Abstract

Background:The management of high-grade (Spetzler-Martin grade 4-5) arteriovenous malformations (AVMs) still has many risks, and even the use of a multidisciplinary approach is commonly insuffi cient for a cure.

Gamma Knife treatment strategies for paediatric AVMs: approaches to refractory cases

“…This is 50% of the dose required for vascular occlusion and the tolerable dose for normal tissues. [16][17][18][19][20] The 4 cm 3 volume was derived from dose-volume isoeffect curves for a 3% risk of brain necrosis from a single fraction of radiosurgery, as described by Flickinger et al 9 It is believed that, by limiting the use of this method in paediatric patients and keeping the course of treatment consistent, the nidus volume and Pollock-Flickinger score can be used more simply in actual clinical practice as factors associated with post-treatment occlusion and bleeding. Nidus volume may be an important factor in post-treatment bleeding due to the prolonged waiting period required to achieve occlusion.…”

Outcome after Gamma Knife surgery for intracranial arteriovenous malformations in children

“…Meanwhile, it has not yet been clearly defined as to which portion of nidus should be targeted first (adjacent to feeding arteries, at the center, or in the vicinity of draining veins). Our concept of staged-volume GKS [14][15][16] was originally based on the experience of the Marseille group. The main idea of initially targeting the nidus in the vicinity of the draining vein is related to obtaining the desired effect on the shunts.…”

“…In our experience with such a technique in both adults and children, the lesion frequently was obliterated following the first stage of treatment, despite the fact that there was incomplete coverage of the nidus with the prescribed isodose, making subsequent radiosurgical sessions unnecessary. 16 Therefore, we advocate observation for 3-4 years after the initial GKS, postponing a final evaluation of the treatment effects and the decision on further strategy until completion of the latency period. Only in cases of AVMs with intraventricular extension, which have a propensity to bleed, do we propose earlier commencement of the second stage of GKS.…”

“…During the last decade staged-volume GKS with sequential high-dose irradiation of different parts of the lesion separated by sufficiently long time intervals has ob-tained wide, albeit not uniform, acceptance for the management of large AVMs. 1,2,5,[14][15][16]23 In our clinic this technique is used routinely with special emphasis on initial targeting of the portion of nidus adjacent to the draining vein in an attempt to affect the main arteriovenous shunts, slow intralesional blood flow, and, finally, cause thrombosis. This treatment strategy has demonstrated high effectiveness, particularly in high-grade AVMs, and has been associated with minimal risk of complications.…”

“…This treatment strategy has demonstrated high effectiveness, particularly in high-grade AVMs, and has been associated with minimal risk of complications. [14][15][16] Moreover, it may be especially effective in children, since pediatric AVMs may be more sensitive to irradiation. 36,46 The objective of the present study was the evaluation of outcomes after unstaged and staged-volume GKS of intracranial AVMs in children.…”