De Novo Formation of Intracranial Aneurysms Following Gamma Knife Surgery

Introduction: Gamma knife surgery (GKS) is a form of radiotherapy used to treat intracranial conditions such as trigeminal neuralgia, vascular malformations, and tumors. Complications include radiation necrosis, neuropathy, and hemorrhage. GKS-induced aneurysms are rare and may fatally rupture. We present our institution’s experience with a de novo post-GKS aneurysm treated with trap bypass and compare our experience with the current literature via a scoping review of cases detailing GKS-induced aneurysms.

Methods: After collection of the index patient’s clinical history, we conducted a scoping literature review using PubMed with MeSH terms such as “aneurysm”, “radiosurgery”, and “gamma knife”. Papers were included if they described de novo post-GKS intracranial aneurysm formation, and excluded if they reported pediatric patients, pre-existing aneurysms, or pseudoaneurysms.

Results: We report a male in his 80s who presented as a transfer from an outside hospital with a WFNS grade 2 right SCA aneurysm rupture. Twenty years before he had received GKS to treat his right-sided trigeminal neuralgia. His aneurysm was unsuccessfully coiled prior to transfer, and upon arrival he was prepped for open securing via a retrosigmoid approach. The aneurysm was intimately adhered to the trigeminal nerve. As there was no saccular component, his aneurysm was trapped, excised, and the parent vessel anastomosed. The patient recovered and was discharged to a skilled nursing facility.

The literature reports 22 cases of post-GKS aneurysms with an average time from GKS of 12 years. Of these, four were SCA aneurysms, and two of which had ruptured. These four were treated using occlusion or coiling. One patient was discharged home, two to inpatient rehabilitation, and one died during hospitalization.

Conclusion : De novo aneurysmal formation is a rare complication of GKS that warrants further study. The value of radiographic surveillance and histological assessment of aneurysmal tissue should be explored to understand the mechanism behind this phenomenon.