Minimally invasive keyhole craniotomies for microsurgical clipping of cerebral aneurysms: comparative meta-analysis of the mini-pterional and supraorbital keyhole approaches.

Objective: Axel Perneczky is responsible for conceptualizing the "keyhole" philosophy as a new paradigm of minimal invasiveness within cranial neurosurgery. Keyhole neurosurgery aims to limit approach-related traumatization and minimize brain retraction while still enabling the neurosurgeon to achieve operative goals. The supraorbital keyhole craniotomy (SOKC) and minipterional (pterional keyhole, PKC) approaches have become mainstays for clipping intracranial aneurysms. While studies have compared these approaches to the traditional pterional craniotomy for clipping cerebral aneurysms, head-to-head comparisons of these workhorse keyhole approaches remain limited.

Methods: The authors queried three databases per PRISMA guidelines to identify all studies comparing the SOKC to the PKC for microsurgical clipping of cerebral aneurysms. Of 148 unique studies returned on initial query, a total of 5 studies published between 2013 and 2019 met inclusion criteria. Where applicable, quantitative meta-analysis was performed via the Mantel-Haenszel method using Review Manager v5.4 (Nordic Cochrane Centre, Cochrane Collaboration, Copenhagen, Denmark). Risk of bias (ROB) was assessed using the Cochrane ROBINS-I tool, and all studies were assigned a Level of Evidence (I-V).

Results: Across all five studies, the mean age ranged from 53.0 to 57.5 years old, and the cohort consisted of more females (n = 403, 60.6%) than males. The proportion of patients presenting with ruptured aneurysmal SAH was comparable between the SOKC and PKC cohorts (p = 0.43). Clipping rate [defined as the rate of successful aneurysm clip deployment with successful intraoperative occlusion] (OR 1.52 [0.49, 4.71], I = 0%, p = 0.47), final occlusion rates (OR 1.27 [0.37, 4.32], p = 0.70), and operative durations (SMD 0.33 [-0.83. 1.49], I = 97%, p = 0.58) were comparable regardless of approach used. Furthermore, rates of intraoperative rupture (OR 1.51 [0.64, 3.55], I = 0, p = 0.34), postoperative hemorrhage (OR 1.49 [0.74, 3.01], I = 0, p = 0.26), postoperative vasospasm (OR 0.94 [0.49, 1.80], I = 63, p = 0.86), and postoperative infection (OR 0.70 [0.16, 2.99], I = 0%, p = 0.63) were equivocal across SOKC and PKC cohorts.

Conclusion: The PKC and SOKC approaches appear to afford comparable outcomes when used for open microsurgical clipping of cerebral aneurysms in select patients with both ruptured and unruptured aneurysms. Both are associated with excellent clipping and occlusion rates, minimal perioperative complication profiles, and favorable postoperative neurologic outcomes. Further investigations are merited so clinicians can further parse out the indications and contraindications for each keyhole approach.