Dissecting aneurysms of the posterior circulation showed a trend toward better long-term functional outcomes compared with saccular aneurysms, and although parent vessel sacrifice was more frequently required for dissecting aneurysms, it was not associated with an increased risk of ischemic complications.
Key Findings
Methods
Dissecting aneurysms (DA) comprised approximately one in five posterior circulation aneurysmal subarachnoid hemorrhage cases requiring surgical treatment.
406 total patients with posterior circulation aSAH who underwent surgical treatment were included from the Chinese Multicenter Cerebral Aneurysm Database (CMAD)
314 patients (77.3%) had saccular aneurysms (SA) and 92 patients (22.7%) had dissecting aneurysms (DA)
Data were collected from January 2017 to December 2020
Baseline data were retrospectively collected; survival status and 2-year mRS scores were prospectively assessed
Results
In unadjusted analyses, dissecting aneurysms were associated with a significantly lower rate of unfavorable functional outcomes at 2 years compared to saccular aneurysms.
Unfavorable outcome rate (mRS 3-6) was 17.1% for DA versus 34.8% for SA (p = 0.003)
Favorable outcomes were defined as mRS 0-2 and unfavorable as mRS 3-6
Outcomes were assessed at 2-year follow-up
After adjustment for covariates in Model 3, DA showed only a trend toward lower risk of unfavorable outcomes (OR = 0.490, 95% CI 0.237–1.013, p = 0.054), which did not reach statistical significance
Results
Dissecting aneurysms required parent vessel sacrifice significantly more often than saccular aneurysms.
Parent vessel sacrifice rate was 22.8% for DA versus 8.0% for SA (p < 0.001)
The association between DA and higher risk of parent vessel sacrifice was consistent across all adjusted models
Model 1: OR = 3.419, 95% CI 1.811–6.456, p < 0.001
Model 2: OR = 2.737, 95% CI 1.415–5.293, p = 0.003
Model 3: OR = 2.899, 95% CI 1.463–5.747, p = 0.002
Results
Despite more frequent parent vessel sacrifice in dissecting aneurysms, ischemic complications were comparable between dissecting and saccular aneurysm groups.
Ischemic complications were described as 'comparable between groups' in unadjusted analyses
Parent vessel sacrifice was not associated with an increased risk of ischemic complications
This finding held despite DA requiring parent vessel sacrifice at nearly three times the rate of SA
Results
After multivariable adjustment, dissecting aneurysm morphology showed a trend toward but did not independently reach a statistically significant association with better long-term outcomes.
In Model 3 (most fully adjusted), OR for unfavorable outcome with DA was 0.490 (95% CI 0.237–1.013, p = 0.054)
The p-value of 0.054 indicates a trend that narrowly missed conventional statistical significance (p < 0.05)
Logistic regression models were used to explore the association between aneurysm morphology and outcomes
The unadjusted difference (17.1% vs. 34.8%, p = 0.003) was attenuated after covariate adjustment, suggesting confounding factors partially explain the outcome difference
What This Means
This research suggests that when a blood vessel in the back part of the brain bursts due to an aneurysm (a weakened, bulging area), the type of aneurysm involved matters for how patients fare over time. The study compared two types: saccular aneurysms, which are balloon-like pouches that form on blood vessels, and dissecting aneurysms, which occur when a tear develops within the wall of the vessel itself. Among 406 patients treated surgically at multiple Chinese hospitals, about one in five had the dissecting type. Before accounting for other differences between the patient groups, those with dissecting aneurysms were nearly half as likely to have poor functional outcomes two years later compared to those with saccular aneurysms (17% versus 35%).
One notable finding is that treating dissecting aneurysms often required intentionally blocking off the affected blood vessel entirely — a procedure called parent vessel sacrifice — which was done about three times more often than in saccular aneurysm cases (23% versus 8%). Despite this more aggressive approach, patients who underwent parent vessel sacrifice did not experience more strokes or other blood-flow-related complications, suggesting the brain was able to compensate through other vessels. When the researchers statistically adjusted for differences in patient characteristics between the two groups, the advantage for dissecting aneurysms in long-term outcomes became a statistical trend rather than a definitive finding (just missing the conventional threshold for significance).
This research suggests that dissecting aneurysms of the posterior circulation, while requiring more aggressive surgical strategies including vessel sacrifice, may carry a more favorable long-term prognosis than saccular aneurysms. The findings highlight that these two aneurysm types behave differently and may warrant distinct treatment planning. However, because the better outcomes with dissecting aneurysms were partly explained by other patient factors, larger studies are needed to confirm whether aneurysm type itself independently drives outcomes.
Li J, Song G, Liu G, Tong Y, Gu X, Wang B, et al.. (2026). Posterior Circulation Aneurysmal Subarachnoid Hemorrhage: A Comparison Between Saccular and Dissecting Aneurysms.. Brain and behavior. https://doi.org/10.1002/brb3.71668