Robot-assisted aspiration improves survival over conservative treatment in critical primary brainstem hemorrhage: a multicenter, volume-stratified cohort study.

Abstract

Background: The optimal management of critical primary brainstem hemorrhage (PBSH, hematoma volume 5-15 mL) remains controversial. While minimally invasive surgery shows promise, multicenter evidence-particularly stratified by hematoma volume-is lacking. This study aimed to evaluate the survival benefit and safety of frameless robot-assisted aspiration compared to conservative treatment in patients with critical PBSH.

Methods: We conducted a multicenter, retrospective cohort study involving 79 consecutive patients [Glasgow Coma Scale (GCS) 3-8] admitted to three neurosurgical centers between May 2022 and October 2025. Patients were allocated to a robot-assisted aspiration group (n = 38) or a conservative care group (n = 41). Further stratification was performed based on initial hematoma volume (5-10 mL, n = 63; >10 mL, n = 16). Volumetric measurements were performed by two independent neurosurgeons blinded to outcomes, demonstrating excellent inter-rater reliability (intraclass correlation coefficient = 0.96). Primary outcomes included 30-day and 90-day survival rates, analyzed using Kaplan-Meier curves and Cox proportional hazards regression. To rigorously control for potential treatment selection bias inherent in a retrospective cohort design, a 1:1 propensity score matching (PSM) sensitivity analysis was additionally performed.

Results: Baseline characteristics, including age, GCS score, and hemorrhage location, were comparable between groups. Safety profiles, including rebleeding (7.89% vs. 4.88%) and intracranial infection rates, were similar (all p > 0.05). In the overall cohort, the robot-assisted aspiration group exhibited a significantly higher 30-day survival rate (76.3% vs. 43.9%, p = 0.006). Stratified analysis revealed that the survival benefit was confined to the 5-10 mL subgroup, where robot-assisted aspiration significantly improved 30-day (82.1% vs. 45.7%, p = 0.004) and 90-day survival (71.4% vs. 42.9%, p = 0.044), alongside improved discharge GCS scores. In the >10 mL subgroup (n = 16), 30-day survival was 60.0% (6/10) vs. 33.3% (2/6) - an absolute difference of +26.7 percentage points (95% CI: -19.9 to +59.8; Fisher's exact p = 0.61; post-hoc power 0.28). This subgroup was underpowered and the result is inconclusive rather than negative. Multivariable Cox regression confirmed robot-assisted aspiration as an independent protective factor (hazard ratio = 0.494, 95% CI: 0.245-0.997, p = 0.049), reducing mortality risk by 50.6%. In the PSM sensitivity cohort (34 matched pairs; 68 patients in total), robot-assisted aspiration still showed a significant survival benefit, reducing the risk of 90-day death by 60.0% (adjusted HR = 0.400, 95% CI: 0.195-0.822, p = 0.013). Volume stratification confirmed significant surgical benefits with respect to both survival and neurological function in the 5-10 mL subgroup (90-day survival rate: 73.1% vs. 32.1%, p = 0.003; distribution of mRS grades: p = 0.034), whereas the outcomes of the two treatment groups converged in the >10 mL subgroup (37.5% vs. 33.3%, p = 1.000).

Conclusions: Robot-assisted aspiration is a safe intervention for critical PBSH and is associated with improved survival over conservative care - an association that persisted after propensity score matching - particularly within the 5-10 mL volume window. In hematomas larger than 10 mL the study was inconclusive: the point estimates favored aspiration but the subgroup was underpowered (n = 16; n = 14 after propensity score matching) and the confidence intervals included no benefit. Long-term functional outcomes were dominated by severe disability or death in both treatment arms regardless of volume. These findings suggest-rather than prove-a volume-dependent therapeutic window, underscoring the need for prospective validation to guide stratified neurocritical care.