Perforator-Aware Explainable Microsurgical Intelligence for Basilar Trunk Aneurysm Reconstruction: A Human-Centred...

Basilar trunk aneurysms (BTAs) are rare intracranial aneurysms. These aneurysms pose substantial clinical risk because they are located close to vital cranial structures and perfusion-sensitive perforating arteries. In addition, outcomes from BTA repair are dependent upon several factors, which include proximity to the brainstem, preservation of perforators, corridor access to the aneurysm, successful clipping of the aneurysm through reconstruction, the need for intraoperative rescue manoeuvres and the ability of the patient to recover from complications. Many previous studies have documented the outcomes associated with BTA repair; however, few studies have examined how the anatomy of the BTA directly relates to surgical decisions made by surgeons. Therefore, we developed an explainable AI framework for documenting surgeon reasoning regarding the open microsurgical treatment of BTAs. The primary objective was to develop and internally evaluate an explainable microsurgical intelligence framework for structuring surgeon reasoning during open microsurgical treatment of BTAs. The secondary objectives were to explore the relationships between the proposed constructs and postoperative pontine infarction, angiographic occlusion, functional outcome, hidden disability, operative difficulty, and composite technical-safety failure. Methods: We retrospectively analysed the cases of 31 adult patients who underwent open microsurgical treatment of a basilar trunk aneurysm at our hospital between October 1999 and March 2025. The cohort included 18 women (58.1%) and 13 men (41.9%), with a median age of 55 years (interquartile range, 44-63 years); 14 patients (45.2%) presented with ruptured aneurysms. A database containing more than 300 variables collected information about each patient's imaging studies, operative strategies employed during surgery, intraoperative events encountered during surgery, intraoperative angiographic verification, occurrence of new injuries or complications resulting from surgery, and degree of recovery in each patient. Temporally separated scores were generated to quantify perforator-aware hazard, compression burden imposed by proximity to the brainstem, constraints imposed by corridors available for clipping of the BTA, burden imposed by clip reconstruction, degree of surgical precision adjusted based on the need for rescue manoeuvres, degree of dataset/model readiness, and degree of case-level learning density. The framework was evaluated internally using methods that included leave-one-out cross-validation, Firth regression modelling, Bayesian modelling, bootstrap optimism correction, calibration assessments using Brier score, decision-curve analysis, evaluations of explainability, conformal uncertainty estimation, and retrieval of similar cases. Results: Complete occlusion of the aneurysm was successfully achieved in 27 patients (87.1%), whereas residual neck or sac remained in four patients (12.9%). New pontine infarction occurred in six patients (19.4%), including four perforator-related infarctions (12.9%). A favourable last-follow-up modified Rankin Scale (mRS) score of 0-2 was achieved in 25 patients (80.6%); however, hidden disability was noted in 11 of these 25 patients (44.0%). Mortality was 6.5% and was limited to two patients with high-grade rupture. PAH-S-pre predicted pontine infarction (OR, 1.19 for every five-point increase; leave-one-out cross-validated AUC, 0.92). The composite technical-safety failure model had an ROC AUC of 0.91, optimism-corrected AUC of 0.88, calibration slope of 0.96, Brier score of 0.10, and permutation p < 0.001. Explainability indicated that PAH-S-pre, BPCI, and CCR represented the most important features. Conformal prediction resulted in abstention from prediction in four patients (12.9%). Conclusions: Expert microsurgical thought processes involved in repairing BTAs can be systematised and recorded into time-relevant and clinically meaningful measures that preserve anatomical interpretability. Clinical use will require external validation before implementation; however, this framework may provide a clinically interpretable foundation for risk-adapted planning, verification, surveillance, education, and future decision-support research for complex neurovascular surgery.