Minimally Invasive Microsurgery for Cerebral Aneurysms.

ntracranial aneurysms arise in ≈2% of the population, and their rupture causes 3% of all strokes. 1 Their treatment requires safely achieving complete aneurysm occlusion while preserving blood flow in the parent, branching, and perforating vessels. For decades, this task was achieved using classic open approaches, such as the pterional craniotomy (PTC) described by Yasargil and Fox in 1975, which afforded safe and effective exposure of the Circle of Willis through the Sylvian fissure with minimal retraction on the frontal and temporal lobes. 2 Supported by the introduction of the operating microscope, this approach gained popularity for treating tumors and aneu-rysms of the anterior circulation and the basilar tip. 2–4 However, the most significant advance in aneurysm treatment has been the advent of safe and effective endovascu-lar techniques for the treatment of intracranial aneurysms, buoyed by clinical trials, such as International Subarachnoid Aneurysm Trial 5 and Barrow Ruptured Aneurysm Trial (BRAT). 6 Although both surgical and endovascular aneurysm occlusion technologies are effective for appropriately selected patients, endovascular treatment is also perceived to be less invasive as compared with classical open surgery. Indeed, technological developments in microsurgery, such as improved vascular imaging, intraoperative navigation, and fluorescence angiography, 7 have focused on improving precision and effectiveness. However, more recently, the advent of endovascular techniques has spurred a shift of surgery to minimally invasive techniques with the goal of improving tolerability, cosmesis, and acceptability for patients. Ideally, this should translate to equivalent safety and efficacy as surgery through standard craniotomies, but with the benefit of reduced operative time, postoperative pain, and length of in-hospital stay and improved cosmesis. 4,8 This article reviews the evolution of minimally invasive microsurgery (MIM) with keyhole or mini-cranioto-mies and the development of endoscope-assisted and purely endoscopic aneurysm surgery. These techniques are already well established in skull base neurosurgery, but are only now being increasingly applied to aneurysm operations. Aneurysm surgery requires exposure and adequate visualiza-tion of the circle of Willis at the skull base. Initially, surgeons used the frontolateral craniotomy as described by Dandy in 1938, involving extensive retraction of the frontal and temporal lobes to provide visualization of an aneurysm. 9 With the advent of the improved illumination and magnification afforded by operating microscopes, Yasargil promoted the PTC involving less brain retraction but more bone removal of the sphenoid wing and dissection of the Sylvian fissure. 2 This approach requires a long skin incision hidden behind the …