J Neurosurg 144:1271–1277, 2026
This clinical study evaluates the etiology of perimesencephalic subarachnoid hemorrhage (pmSAH) by applying high-resolution cone-beam CT (CBCT) during catheter angiography to detect basilar artery perforator outpouchings. The retrospective analysis of 22 pmSAH patients found that CBCT identified basilar perforator pseudoaneurysms in a substantial subset, with conservative management yielding excellent outcomes.
The authors argue that many pmSAHs may be arterial rather than venous in origin when imaged with modern high-resolution CBCT protocols. They recommend heightened suspicion for an arterial source and detailed angiographic CBCT acquisition, while acknowledging limits of retrospective design, variable imaging quality, and unresolved management questions.
Objective High-resolution CBCT performed during catheter angiography was used to better identify the etiology of perimesencephalic SAH (pmSAH), challenging the historical assumption of a venous source.
Methods Retrospective review of pmSAH cases (Jan 2023–Dec 2024) requiring catheter angiography with available, diagnostic-quality CBCT; images were interpreted by two experienced neuroangiographers to consensus.
Cohort Of 152 spontaneous SAH presentations, 22 met Rinkel criteria for pmSAH; after exclusions (alternative causes found, missing/low-quality CBCT), 13 patients remained for CBCT-based imaging analysis.
Key finding In 8/13 (61.5%) analyzed pmSAH cases, CBCT showed a basilar artery perforator focal outpouching consistent with a rupture site (submillimeter, 0.4–0.8 mm).
Anatomy distribution Among the 8 identified perforator lesions, 6 were rostral basilar perforators, with 1 midbasilar and 1 caudal perforator involvement.
Outcomes All pmSAH patients—including those with identified basilar perforator outpouchings—had excellent recovery, with no re-rupture events and no clinically significant vasospasm reported in the series.
Follow-up imaging In patients who underwent follow-up DSA with CBCT, the basilar perforator finding resolved on follow-up imaging.
Conclusion/implication pmSAH should be approached with high suspicion for an arterial etiology (basilar perforator pseudoaneurysm frequently detectable with high-resolution CBCT), and conservative management was associated with excellent outcomes in this cohort.


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