Aneurysm Securing After SAH: Clipping vs. Coiling
Early aneurysm securing is the single most impactful intervention in aneurysmal subarachnoid hemorrhage (aSAH). Without treatment, the risk of rebleeding is approximately 4% on day 1 and 1–2% per day thereafter over the first two weeks — and rebleeding carries a mortality rate exceeding 70%. The 2023 AHA/ASA guidelines recommend aneurysm treatment as early as feasible, ideally within 24 hours of presentation (Class 1, LOE B-NR). Two landmark trials — ISAT and BRAT — established endovascular coiling as the preferred modality for aneurysms amenable to both approaches, though surgical clipping remains essential for specific anatomic and clinical scenarios.
🔹 Bottom Line: Aneurysm Securing
- Timing: Secure the aneurysm as early as feasible, ideally <24 hours. Ultra-early treatment (<12h) is increasingly supported but not mandated (AHA Class 1, LOE B-NR).
- Coiling preferred when feasible: ISAT demonstrated 7.4% absolute risk reduction in death or dependency with coiling vs. clipping at 1 year (p=0.0001), with survival benefit maintained at 7 years.
- Clipping remains essential: MCA aneurysms, wide-neck aneurysms, aneurysms with parenchymal hematomas requiring evacuation, and complex morphologies may be better suited for microsurgical clipping.
- Prevent rebleeding: Short-course tranexamic acid (≤72 hours) is reasonable to reduce rebleeding before aneurysm securing (AHA Class 2a). Maintain SBP <160 mmHg pre-treatment.
- Intraoperative hypothermia does not help: IHAST showed no benefit from cooling during open clipping (66% vs 63% good outcome, NS).
1. Endovascular Coiling vs. Surgical Clipping
The choice between endovascular coiling and microsurgical clipping is the most consequential treatment decision in aSAH management. Two major RCTs have addressed this question, and their results — alongside evolving endovascular technology — have shifted practice decisively toward an endovascular-first approach for most patients.
1.1 ISAT (2002–2005)
The International Subarachnoid Aneurysm Trial (ISAT) remains the largest and most influential trial comparing the two modalities. A total of 2,143 patients with ruptured intracranial aneurysms considered suitable for either treatment were randomized to endovascular coiling (n=1,073) or neurosurgical clipping (n=1,070) at 43 neurosurgical centers, predominantly in the UK and Europe.
| Outcome | Coiling | Clipping | Effect |
|---|---|---|---|
| Death or dependency (mRS 3–6) at 1 year | 23.5% | 30.9% | RR 0.76 (95% CI 0.66–0.87), p=0.0001 |
| Death at 1 year | 8.0% | 9.9% | Trend favoring coiling |
| Epilepsy risk | Lower | Higher | RR 0.52 favoring coiling |
| Survival benefit at 7 years | Better | Worse | Log-rank p=0.03 |
| Late rebleeding (after 1 year) | 7 patients | 2 patients | 0.2% per patient-year — higher in coiling group |
The survival benefit of coiling was maintained for up to 7 years of follow-up, driven primarily by fewer procedure-related complications. However, ISAT enrolled predominantly good-grade patients (88% WFNS I–II) with anterior circulation aneurysms (97%), limiting generalizability to poor-grade SAH, posterior circulation, and complex aneurysm morphologies. The slightly higher late rebleeding rate with coiling (0.2%/year) underscores the need for long-term angiographic follow-up.
1.2 BRAT
The Barrow Ruptured Aneurysm Trial (BRAT) was a single-center study at Barrow Neurological Institute that randomized 471 patients with acute aSAH to clipping (n=238) or coiling (n=233). Unlike ISAT, BRAT included all ruptured aneurysms regardless of whether they were deemed suitable for both modalities, making it more pragmatic. Crossover was permitted based on clinical judgment — and was substantial.
| Timepoint | Poor Outcome (mRS >2) — Clip | Poor Outcome (mRS >2) — Coil | p-value |
|---|---|---|---|
| 1 year (ITT) | 33.7% | 23.2% | 0.02 (OR 1.68) |
| 1 year (as treated) | 33.9% | 18.4% | 0.005 (OR 2.28) |
| 3 years | 35.8% | 30.4% | NS |
| 6 years | Similar in anterior circulation | — | Posterior: coiling superior (p=0.0007) |
At 1 year, coiling was clearly superior. By 6 years of follow-up, outcomes converged for anterior circulation aneurysms, but coiling remained significantly superior for posterior circulation aneurysms. The retreatment rate was higher in the coiling group (6.9% vs. 2.9% at 1 year), consistent with ISAT findings. Only 62.3% of patients assigned to coiling actually received coiling, reflecting the real-world challenge that not all aneurysms are amenable to endovascular treatment.
🔹 Clinical Relevance: Choosing Between Clipping and Coiling
- Endovascular coiling is preferred when the aneurysm is amenable to either treatment (AHA 2023, Class 1, LOE B-R), particularly for posterior circulation and basilar tip aneurysms.
- Microsurgical clipping is preferred for: (1) MCA bifurcation aneurysms with wide necks or unfavorable dome-to-neck ratio; (2) aneurysms with large parenchymal hematomas requiring surgical evacuation; (3) very wide-necked aneurysms not suitable for stent-assisted coiling in the acute setting; (4) aneurysms with branches arising from the dome or neck.
- Multidisciplinary decision: Both a vascular neurosurgeon and neurointerventionalist should evaluate every case (AHA Class 1). Neither modality is universally superior.
- Modern endovascular advances — flow diverters, intrasaccular devices (WEB), stent-assisted coiling — have expanded the range of aneurysms treatable by endovascular means, though most of these technologies lack robust RCT data in the ruptured setting.
- Long-term follow-up: Coiled patients require serial angiographic surveillance (MRA or DSA at 6 months, then periodically) to detect aneurysm recurrence. Retreatment rates are 10–17% over 10 years.
2. Timing of Aneurysm Securing
Historical practice created arbitrary "early" (days 0–3) vs. "late" (days 10–14) surgical windows, avoiding the vasospasm period (days 4–10). This paradigm has been completely abandoned. Modern evidence and guidelines favor the earliest feasible treatment, reflecting the catastrophic nature of rebleeding.
2.1 Guideline Recommendations
| Guideline | Timing Recommendation | COR/LOE |
|---|---|---|
| AHA 2023 | As early as feasible to reduce rebleeding risk. Within 24 hours recommended. | Class 1, LOE B-NR |
| NCS 2023 | Within 24 hours of presentation. Emergency treatment if rebleeding occurs. | Strong recommendation |
| NICE 2022 | Refer within 24 hours; treat within 48 hours of referral. | — |
Observational data increasingly support ultra-early treatment (<12 hours from ictus). A meta-analysis of 75 studies found that treatment within 24 hours was associated with lower in-hospital mortality (OR 0.56) compared to delayed treatment. However, these are observational data subject to confounding (patients treated later may have been sicker or transferred from outside hospitals). No RCT has directly tested ultra-early vs. early treatment.
🔴 Delayed Transfer = Delayed Treatment
- The most common reason for delay beyond 24 hours is transfer from a non-comprehensive stroke center. This is a systems-of-care failure, not a clinical decision.
- Early recognition and rapid transfer to a high-volume center (≥35 aSAH cases/year) directly impacts outcomes (AHA Class 1).
- If transfer will be significantly delayed, initiate SBP control (<160 mmHg) and consider short-course tranexamic acid at the referring hospital.
3. Preventing Rebleeding Before Securing
The period between initial hemorrhage and aneurysm securing represents the highest-risk window for rebleeding. Two evidence-based strategies can reduce this risk: blood pressure control and short-course antifibrinolytic therapy.
3.1 Blood Pressure Management
The 2023 AHA guidelines recommend maintaining SBP <160 mmHg before aneurysm securing (Class 2a, LOE B-NR). This target balances rebleeding prevention against the risk of cerebral hypoperfusion — particularly important in patients with elevated ICP or clinical signs of vasospasm. Easily titratable IV agents (nicardipine, clevidipine, labetalol) are preferred. Nitroprusside should be avoided (increases ICP). The 2023 NCS guidelines suggest a similar approach, targeting a reduction in SBP of approximately 20% from baseline or an absolute SBP target of 140–160 mmHg, whichever is less aggressive.
3.2 Short-Course Antifibrinolytics
Antifibrinolytic agents (tranexamic acid, aminocaproic acid) reduce early rebleeding by stabilizing the fibrin clot overlying the ruptured aneurysm. Historically, prolonged courses (2+ weeks) were associated with increased DCI, negating the rebleeding benefit. Modern evidence supports short-course therapy (<72 hours), administered only until the aneurysm is secured:
- Hillman et al. (2002): Ultra-early TXA (started pre-CT, continued to securing) reduced rebleeding from 10.8% to 2.4% (p=0.02) with improved 3-month outcomes.
- Cochrane meta-analysis (2020): Antifibrinolytics reduced rebleeding (RR 0.65; 95% CI 0.44–0.97) but did not clearly improve functional outcomes when used for prolonged durations due to increased ischemic complications.
- AHA 2023: Short-course (<72h) antifibrinolytic therapy is reasonable to reduce rebleeding before aneurysm securing, particularly when securing will be delayed (Class 2a, LOE B-R). Dosing: TXA 1g IV bolus then 1g q8h, or aminocaproic acid 4g IV bolus then 1g/h infusion.
- NCS 2023: Conditionally recommends short-term TXA (≤24h) to reduce rebleeding risk in the pre-aneurysm securing period.
🔹 Clinical Relevance: Antifibrinolytics in Practice
- Start early, stop at securing: Administer TXA as soon as aSAH is confirmed; discontinue at the time of aneurysm treatment (clipping or coiling).
- Do not continue beyond 72 hours: Prolonged use increases DCI risk and negates the rebleeding benefit.
- Greatest benefit when treatment is delayed: If the aneurysm cannot be secured within 24 hours (transfer delay, OR scheduling), short-course TXA is most valuable.
- Contraindications: Active DCI, thromboembolic disease, disseminated intravascular coagulation. Use with caution in patients with renal impairment.
4. Intraoperative Considerations for Clipping
4.1 Intraoperative Hypothermia
The Intraoperative Hypothermia for Aneurysm Surgery Trial (IHAST) randomized 1,000 good-grade aSAH patients undergoing surgical clipping to intraoperative hypothermia (33°C) versus normothermia (36.5°C). Good outcome (GOS 1) at 90 days was 66% in the hypothermia group versus 63% in the normothermia group — a non-significant difference (OR 1.14; 95% CI 0.88–1.48; p=0.32). Postoperative bacteremia was more common with hypothermia (5% vs 3%, p=0.05). IHAST definitively showed that routine intraoperative cooling does not improve outcomes after aneurysm surgery.
4.2 Local Drug Delivery: Nicardipine Implants
A promising innovation for patients undergoing clipping is the intraoperative placement of sustained-release nicardipine pellets around the basal cerebral vasculature to locally prevent vasospasm:
- Nicardipine Implant Trial (2024): 41 patients with WFNS grade 3–4 aSAH undergoing anterior circulation clipping. Implant group (10 pellets, 4 mg each, n=21) vs. standard care (n=20). Moderate-to-severe vasospasm: 20% implant vs. 58% control (p=0.02). Rescue therapy needed: 10% vs. 58% (p=0.002). New infarcts: 10% vs. 32% (NS). Favorable outcome at 52 weeks: 84% vs. 67% (NS). No systemic absorption — therapeutic CSF levels only.
- NicaPlant (2023): Phase IIA dose-escalation study (14 patients). 10 pellets selected as optimal dose based on safety, CSF drug levels, and usability. Only 1/10 implant patients developed moderate vasospasm vs. 2/4 controls with severe vasospasm. No systemic side effects.
These results are compelling — vasospasm reduced by two-thirds with local nicardipine delivery — but both studies are small and single-center. Larger multicenter RCTs are needed. If confirmed, this could become a standard adjunct to microsurgical clipping, offering a unique advantage that coiling cannot provide.
5. Aneurysm Retreatment & Long-Term Follow-Up
A key trade-off of endovascular coiling is the higher rate of aneurysm recurrence requiring retreatment, compared to the more definitive occlusion achieved by surgical clipping.
| Parameter | Coiling | Clipping |
|---|---|---|
| Complete occlusion rate (immediate) | ~50–65% (Raymond I) | ~85–95% |
| Retreatment rate (1 year) | 6–10% | 1–3% |
| Retreatment rate (10 years) | 10–17% | 2–5% |
| Late rebleeding rate | ~0.2%/year | ~0.05%/year |
| Recommended follow-up | MRA or DSA at 6 months, 18 months, then periodically | CTA or DSA at 3–12 months; interval imaging as indicated |
The AHA 2023 guidelines recommend long-term angiographic follow-up for all coiled aneurysms (Class 1, LOE B-NR). Retreatment of recurrent aneurysms (additional coiling, flow diversion, or surgical clipping) is generally safe and effective. The slightly higher retreatment rate is considered an acceptable trade-off given the superior acute outcomes with coiling demonstrated by ISAT and BRAT.
6. Special Populations & Considerations
| Scenario | Preferred Approach | Rationale |
|---|---|---|
| MCA bifurcation aneurysms | Clipping (often preferred) | Broad necks, incorporated branches, Sylvian fissure accessibility. BRAT subgroup: no difference in MCA aneurysm outcomes between modalities. |
| Posterior circulation (BA tip, PICA) | Coiling (strongly preferred) | Surgical access challenging; BRAT 6-year: coiling significantly superior for posterior circulation (p=0.0007). |
| Poor-grade SAH (WFNS IV–V) | Coiling (generally preferred) | Less physiologic stress; avoids craniotomy. However, ISAT excluded most poor-grade patients. Clinical decision based on individual factors. |
| Large hematoma with mass effect | Clipping + surgical evacuation | Addresses both the aneurysm and the mass effect in a single procedure. AHA 2023 Class 2a. |
| Giant aneurysms (≥25 mm) | Individualized — often combined approach | High recurrence with coiling alone; may require flow diversion, bypass, or surgical trapping. |
| Elderly (≥70 years) | Coiling (preferred) | Less invasive; better tolerated. Operative clipping carries higher morbidity in elderly patients. |
| Pregnancy | Case-by-case; coiling often preferred | Minimizes surgical stress and anesthesia duration. Shield fetus from fluoroscopy when possible. |
7. Trial Comparison Table
| Trial | Year | N | Design | Key Finding | Limitations |
|---|---|---|---|---|---|
| ISAT | 2002–2005 | 2,143 | Multicenter RCT, 43 sites. Coiling vs. clipping for ruptured aneurysms suitable for both. | Coiling reduced death or dependency by 7.4% at 1 year (p=0.0001). Survival benefit at 7 years. Lower seizure risk with coiling. Higher late rebleeding with coiling. | 88% good-grade, 97% anterior circulation. High-volume UK centers. Pre-dates modern endovascular devices. |
| BRAT | 2011 | 471 | Single-center RCT (Barrow). Coiling vs. clipping for all ruptured aneurysms. | Coiling superior at 1 year (23.2% vs 33.7% poor outcome, p=0.02). By 6 years: converged for anterior, coiling superior for posterior (p=0.0007). High crossover (38% of coil-assigned received clipping). | Single center. High crossover limits ITT interpretation. Pre-dates flow diverters. |
| IHAST | 2005 | 1,000 | Multicenter RCT. Intraoperative hypothermia (33°C) vs. normothermia during clipping. | No benefit from hypothermia (66% vs 63% good outcome, p=0.32). More bacteremia with cooling. Routine cooling not recommended. | Good-grade patients only (WFNS I–III). Does not address targeted hypothermia in poor-grade patients. |
| Nicardipine Implant | 2024 | 41 | Single-center RCT. Local nicardipine pellets during clipping vs. standard care. | Vasospasm reduced from 58% to 20% (p=0.02). Rescue therapy 10% vs 58% (p=0.002). No systemic side effects. Favorable outcome 84% vs 67% (NS). | Small, single-center. WFNS 3–4 only, anterior circulation clipping only. Needs multicenter confirmation. |
| NicaPlant | 2023 | 14 | Phase IIA dose-finding. NicaPlant pellets during clipping. | 10-pellet dose safe and well-tolerated. CSF nicardipine levels therapeutic without systemic absorption. 1/10 implant patients had vasospasm vs 2/4 controls. | Very small. Dose-finding, not efficacy study. |
References
- Molyneux AJ, et al. International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet. 2005;366(9488):809–817.
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- Spetzler RF, et al. The Barrow Ruptured Aneurysm Trial: 6-year results. J Neurosurg. 2015;123(3):609–617.
- Todd MM, et al. Mild intraoperative hypothermia during surgery for intracranial aneurysm (IHAST). N Engl J Med. 2005;352(2):135–145.
- Barth M, et al. Locally applied nicardipine prolonged-release implants for prevention of vasospasm after aSAH. Neurosurgery. 2024;95(3):612–620.
- Etminan N, et al. NicaPlant: A phase IIA dose-finding study. Stroke. 2023;54(5):e223–e230.
- Hillman J, et al. Immediate administration of tranexamic acid and reduced incidence of early rebleeding after aneurysmal subarachnoid hemorrhage. J Neurosurg. 2002;97(4):771–778.
- Hoh BL, et al. 2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage. Stroke. 2023;54(7):e314–e370.
- Treggiari MM, et al. Guidelines for the Neurocritical Care Management of Aneurysmal Subarachnoid Hemorrhage. Neurocrit Care. 2023;39(1):1–28.