Radiosurgery for cavernous malformations: theory and practice.

Stereotactic radiosurgery is the precise delivery of a therapeutically effective radiation dose to an imaging-defined target. Over the past 5 decades, stereotactic radiosurgery has undergone significant advances that have improved patient outcomes and made it a critical part of modern neurosurgical practice and training. A review of the history of radiosurgery clearly shows a parallel between the development of new imaging technologies and indications for this technique. The first patients treated with radiosurgery had their dose planning based on cerebral angiography or skull radiographs, so the majority of patients in this first phase had arteriovenous malformations (AVMs), tumors adjacent to cranial base landmarks such as the sella, or trigeminal neuralgia with the gasserian ganglion being the target.17 With the advent of computed tomography and magnetic resonance imaging (MRI), the potential use of radiosurgery for both intraand extra-axial tumors expanded greatly since they could be stereotactically defined. Cavernous malformations (CMs) are vascular lesions that comprise the majority of angiographically occult vascular malformations diagnosed in the modern neuroimaging era. Although seen on cerebral angiography, CMs have a typical appearance on MRI that has permitted a better understanding of their incidence and natural history. Cavernous malformations may present with bleeding, seizures, or as incidental findings. Surgical resection of CMs is the preferred management for patients with symptomatic lesions.23,27 Resection of CMs allows clot removal, improvement in seizures, and protection against future intracranial hemorrhage (ICH). Radiosurgery has been performed as an option for a select group of patients with CMs.1,3,6,8,9,12–15,21 The traditional indication for CM radiosurgery is a patient with a history of multiple ICHs from a surgically inaccessible lesion (Fig. 11.1). Despite its clinical use for more than 2 decades, CM radiosurgery remains controversial.