What is the role of aneurysm stent in treating posterior circulation stroke?

Aneurysm Stenting in Posterior Circulation Stroke

For posterior circulation aneurysms causing stroke, flow diverter stents should be reserved only for complex cases where conventional surgical clipping or primary coiling are not technically feasible, as stents carry significantly higher complication rates in this anatomical location. 1

Treatment Hierarchy for Posterior Circulation Aneurysms

First-Line Approaches

• Surgical clipping remains the gold standard when technically feasible, particularly for younger patients requiring durable long-term protection 1
• Primary coiling without stent assistance should be attempted first for saccular aneurysms amenable to endovascular treatment 1, 2
• Conventional approaches are explicitly preferred over stents/flow diverters due to lower complication profiles 1

When Stents May Be Considered

Flow diversion should only be used for 1:

• Fusiform or blister aneurysms without a defined neck
• Wide-neck aneurysms not amenable to clipping or primary coiling
• Cases where all conventional options have been exhausted

Critical caveat: The American Heart Association/American Stroke Association explicitly states that stents or flow diverters should NOT be used for ruptured saccular aneurysms amenable to either primary coiling or clipping 1, 2

Location-Specific Risk Profile

Posterior Circulation Carries Substantially Higher Risk

• Mortality rates for giant posterior circulation aneurysms reach 9.6% with morbidity of 37.9% compared to anterior circulation 3
• Flow diverter treatment of posterior circulation aneurysms shows 15% procedure-related mortality versus lower rates in anterior circulation 4
• Ischemic stroke occurs in 11% and perforator infarction in 7% with flow diversion in posterior circulation 4

Anatomical Challenges

• Basilar apex aneurysms are intimately associated with midbrain perforating arteries that can be injured during either open surgery or endovascular procedures 3
• Aneurysms arising from the mid-portion of the basilar artery require specialized techniques and carry increased morbidity 3

Size-Dependent Treatment Considerations

Small to Medium Aneurysms (<25mm)

• Non-giant posterior circulation aneurysms: 3% mortality, 12.9% morbidity with surgical approaches 3
• Morbidity rates: <3% for ≤5mm, ~7% for 6-15mm, 14% for 16-24mm 3

Giant Aneurysms (≥25mm)

• Combined mortality and morbidity rates approach 20% and 50% respectively for posterior circulation 3
• These carry the highest risk regardless of treatment modality 3
• Flow diverter mortality is significantly higher with giant basilar artery aneurysms 4

Stent-Assisted Coiling vs Flow Diversion

When endovascular treatment is necessary and conventional coiling fails:

Stent-Assisted Coiling

• Lower periprocedural complication rate (6%) compared to flow diversion (18%) 5
• Similar complete/near-complete occlusion rates (84%) to flow diversion 5
• Preferred when anatomical configuration allows 1

Flow Diversion

• Higher occlusion rates (83-84%) at 6-month follow-up 5, 4
• Significantly higher periprocedural complications (18% vs 6%) 5
• Requires dual antiplatelet therapy with associated thromboembolic risks 1
• Stroke remains the most common complication regardless of modality 5

Critical Management Pitfalls

Antiplatelet Therapy Complications

• Dual antiplatelet therapy required for flow diversion increases thromboembolic risk 1
• Clopidogrel non-responders must be switched to alternative agents to reduce complications 6
• Appropriate antiplatelet regimen is associated with lower complication rates 6

Ruptured vs Unruptured Status

• Ruptured aneurysms have significantly lower odds of good outcomes with flow diversion 4
• Procedure-related good outcome rate is only 79% overall for posterior circulation 4

Age-Related Considerations

• Combined morbidity/mortality: 6.5% for patients <45 years, 14.4% for 45-65 years, 32% for patients ≥64 years 3
• Older patients have increased atherosclerotic burden complicating treatment 3

Follow-Up Requirements

Post-Stent/Flow Diversion Monitoring

• More frequent and longer-term follow-up imaging is mandatory to monitor for incomplete occlusion 1
• DSA at 6 months, then annually until complete occlusion confirmed 1
• Assessment of cognitive outcomes in addition to standard neurological measures 2

Post-Clipping Surveillance

• Regular cerebrovascular imaging to identify remnants or recurrence 7
• Recurrence rate: 0.26% per year for completely clipped aneurysms, 0.89% per year for incomplete clipping 3
• Follow-up warranted within 5-10 years, up to 20 years in younger patients 3

Hospital Volume Matters

Surgical experience dramatically influences outcomes: hospitals performing >10 craniotomies per year have 53% lower mortality (5.3% vs 11.2%) compared to low-volume centers 3