Long Sylvian Approach for Proximal Middle Cerebral Artery Aneurysm

This case involved a 66-year-old woman with unruptured proximal middle cerebral artery (MCA) aneurysm that had been found 4 years earlier and followed up with annual magnetic resonance imaging examinations. Considering several risk factors for rupture, such as increasing size and irregular shape of the aneurysm, we offered clipping surgery (Video 1). Preoperative 3-dimensional digital subtraction angiography demonstrated an irregularly shaped aneurysm 6 mm in maximum diameter with multiple daughter sacs. Preoperative magnetic resonance imaging clearly showed that the aneurysm dome was buried in the posterior orbital gyrus. Left pterional craniotomy was performed with a long-distance dissection through the sylvian fissure from the distal M2 segment of the MCA to the internal carotid artery to achieve proximal control. The irregularly shaped aneurysm was completely isolated from the circulation with multiple miniclips under motor evoked potential monitoring with a subdural electrode. Doppler ultrasonography and indocyanine green confirmed complete clipping and patent flow through the MCA bifurcation. Postoperative 3-dimensional computed tomography angiography confirmed no aneurysm filling, and diffusion-weighted imaging demonstrated no ischemic complications. Depending on the positional relationship of the aneurysm and limen insulae, different surgical procedures for head positioning, distance of Sylvian fissure dissection, and securing the site for proximal control are essential for safe clipping of MCA aneurysms.