Neurosurgery. 2026;99(5):1136-1148
Microsurgical clipping remains a strong option for middle cerebral artery bifurcation aneurysms, particularly when durable exclusion and branch preservation are central concerns. Monteiro and colleagues report higher complete occlusion rates after clipping than after endovascular treatment. However, this retrospective comparison does not establish superior functional outcomes or justify choosing the same treatment for every aneurysm.
Study and key findings
The study included 1,060 adults treated at ten US cerebrovascular centers between 2008 and 2023. Treatment comprised clipping in 722 patients, simple coiling in 134, stent-assisted coiling in 106, flow diversion in 34, and intrasaccular flow disruption in 64. Both ruptured and unruptured aneurysms were included.
Reported complete occlusion at the last angiographic assessment was 90.6% after clipping versus 66.0% across endovascular modalities. Among individual endovascular techniques, stent-assisted coiling had the highest reported final complete occlusion rate, at 75.0%. Mean angiographic follow-up differed substantially: 35.2 months after clipping versus 24.8 months after endovascular treatment.
The clipping group contained more wide-necked aneurysms and lesions involving an arterial branch, and had worse baseline functional status. Discharge modified Rankin Scale distributions did not differ significantly between clipping and pooled endovascular treatment. Follow-up complications also differed by technique; the small flow-diversion group had higher reported ischemic event rates.
Interpretation and limitations
The surgical relevance lies in assessing whether the aneurysm neck can be reconstructed while preserving incorporated branches. The findings support retaining clipping in multidisciplinary treatment planning, rather than equating newer devices with better outcomes.
Treatment selection was not randomized, outcomes were locally adjudicated, and more than 20% of each follow-up variable was missing. Unequal surveillance, changing technology over 15 years, and limited numbers for some modalities weaken direct comparisons. Detailed aneurysm orientation was not recorded. Angiographic success therefore should not be interpreted as proof of functional superiority, and nonsignificant clinical differences do not establish equivalence.
Clinical takeaway
Evaluate neck configuration, branch incorporation, rupture status and patient condition alongside local microsurgical and endovascular expertise. Balance the prospect of complete occlusion against procedural risk and branch preservation. This series informs that discussion; it does not provide a universal treatment hierarchy.