Unilateral approach to bilateral middle cerebral artery aneurysms: a large series and a proposed grading system to predict technical difficulties.

This study includes the surgical treatment of 31 patients with bilateral MCA (bMCA) aneurysms using a unilateral approach and is the second largest series in the literature. The main aim of this study is to present a proposed grading system to preoperatively predict the difficulties in this approach. The clinical files, radiological studies, operation records, intraoperative video recordings, complications and outcomes of 31 patients were retrospectively reviewed. In the first part of this study (2001-2010), we operated on 22 patients with bMCA aneurysms and were able to clip the contralateral aneurysm via unilateral approach in only 12 cases (54.5%). Considering our experience from the surgery of these patients, we identified 5 parameters that reveal surgical difficulties. In the second part of the study (2011-2023), considering these 5 parameters, 20 patients were selected for unilateral approach and bilateral aneurysms could be clipped in 19 patients (95%). As a result, 26 of 31 patients (83.9%) were discharged with a favorable outcome (mRS 0-2, excellent-good). Intraoperative rupture occurred in one patient. Based on our experience, we developed a grading system with a total of 10 points by assigning points according to the degree of difficulty of each parameter and classified surgical difficulty as follows: 0-1 low difficulty, 2-3 moderate difficulty, 4-6 high difficulty and 7-10 very high difficulty. Patients with bMCA aneurysms can be operated via unilateral approach in experienced hands in properly selected cases. This grading system may help the neurosurgeon in this selection by preoperatively predicting intraoperative difficulties. This study is a completely retrospective file scan. This is not a clinical trial. Clinical trial number: not applicable.