Gamma Knife radiosurgery of saccular aneurysms in a rabbit model

Abstract

OBJECTIVE Intracranial aneurysms are vascular abnormalities associated with neurological morbidity and mortality due to risk of rupture. In addition, many aneurysm treatments have associated risk profiles that can preclude the prophylactic treatment of asymptomatic lesions. Gamma Knife radiosurgery (GKRS) is a standard treatment for trigeminal neuralgia, tumors, and arteriovenous malformations. Aneurysms associated with arteriovenous malformations have been noted to resolve after treatment of the malformation. The aim of this study was to determine the efficacy of GKRS treatment in a saccular aneurysm animal model. METHODS Aneurysms were surgically produced using an elastase-induced aneurysm model in the right common carotid artery of 10 New Zealand white rabbits. Following initial observation for 4 years, each rabbit aneurysm was treated with a conformal GKRS isodose of 25 Gy to the 50% margin. Longitudinal MRI studies obtained over 2 years and terminal measures obtained at multiple time points were used to track aneurysm size and shape index modifications. RESULTS Aneurysms did not rupture or involute during the observation period. Whole aneurysm and blood volume averages decreased with a linear trend, at rates of 1.7% and 1.6% per month, respectively, over 24 months. Aneurysm wall percent volume increased linearly at a rate of 0.3% per month, indicating a relative thickening of the aneurysm wall during occlusion. Nonsphericity of the average volume, aspect ratio, and isoperimetric ratio of whole aneurysm volume all remained constant. Histopathological samples demonstrated progressive reduction in aneurysm size and wall thickening, with subintimal fibrosis. Consistent shape indices demonstrate stable aneurysm patency and maintenance of minimal rupture risk following treatment. CONCLUSIONS The data indicate that GKRS targeted to saccular aneurysms is associated with histopathological changes and linear reduction of aneurysm size over time. The results suggest that GKRS may be a viable, minimally invasive treatment option for intracranial aneurysm obliteration.

Gamma Knife Radiosurgery of Distal Aneurysm: A Case Series

“…Although passive thrombotization of the aneurysm through feeder artery obliteration is the most possible explanation for the cure, the direct effect on the sac of the aneurysm cannot be excluded. Histopathological changes and linear reduction of aneurysm size over time after gamma knife radiosurgery targeted to saccular aneurysms in a rabbit model were observed, and direct radiosurgical dosage of 25 Gy resulted in 50% occlusion at 24 months [11]. An analogous situation could be found when the positive effect of radiosurgery with regression and decreased risk of rebleeding in case of cavernomas is reported, despite the fact that cavernomas are often formed by larger lacunas with no capillary nidus.…”

Radiosurgery for Intracranial Aneurysms: Blitzkrieg or Guerrilla War?

“…A few animal experimental studies have hypothesized about the efficacy of GKRS in the management of aneurysm treatment. GKRS showed a linear longitudinal decrease in total and luminal volume with promising changes similar to those seen in the AVMs [4]. Apart from the difference in the vascular wall, the differential response of AVMs and aneurysms to radiosurgery is because of the differences in their neighborhood.…”

Gamma Knife Radiosurgery for Berry Aneurysms: Quo Vadis

“…Consistent shape indices (nonsphericity of the average volume, aspect ratio, and isoperimetric ratio of whole aneurysm volume) demonstrated stable aneurysm patency and maintenance of minimal rupture risk during the treatment. 8…”

“…This makes other vascular pathologies relatively resistant to the radiosurgery as cavernomas are usually surrounded by hemosiderin ring and fistulas also similar surroundings. 8…”