What is the effectiveness of flow diversion for posterior communicating (PComm) artery aneurysms with a non-fetal but moderate to large caliber posterior communicating (PComm) artery coming off the aneurysm and a good-sized ipsilateral posterior cerebral artery (P1-PCA)?

Flow Diversion for PComm Aneurysms with Non-Fetal but Moderate to Large Caliber PComm Artery

Flow diversion is generally not recommended as first-line treatment for posterior communicating (PComm) artery aneurysms with a non-fetal but moderate to large caliber PComm artery originating from the aneurysm, even with a good-sized ipsilateral P1-PCA, due to higher risk of complications and lower occlusion rates compared to conventional treatment options.

Anatomical Considerations and Treatment Challenges

• The specific anatomical configuration of a PComm aneurysm with a moderate to large caliber PComm artery originating from the aneurysm presents unique challenges for flow diversion therapy 1
• When a significant PComm artery arises from the aneurysm, flow diversion may be less effective due to persistent flow through the PComm, which can prevent complete aneurysm occlusion 2
• Even with a good-sized ipsilateral P1-PCA segment, the persistent flow through the moderate to large PComm artery can maintain patency of the aneurysm sac, reducing treatment efficacy 2

Efficacy of Flow Diversion in This Scenario

• Studies specifically examining PComm aneurysms with incorporated PComm arteries show significantly lower complete occlusion rates with flow diversion compared to other aneurysm configurations 2
• One study demonstrated only 17% complete occlusion rate at 5-7 months follow-up for PComm aneurysms associated with fetal PCA variants, with an overall occlusion rate of only 33% even after retreatment 2
• Flow diversion for complex aneurysms involving branch vessels generally shows lower efficacy, with complete occlusion rates of 61-69% for ICA aneurysms overall, but significantly lower rates when branch vessels originate from the aneurysm 3

Treatment Recommendations Based on Current Guidelines

• The 2023 AHA/ASA guidelines explicitly state that for patients with aneurysmal subarachnoid hemorrhage (aSAH) from ruptured saccular aneurysms amenable to either primary coiling or clipping, stents or flow diverters should not be used due to higher risk of complications 4
• For unruptured aneurysms, conventional treatment options (clipping or coiling) should be considered first when technically feasible 1
• Flow diversion should be reserved for cases where conventional treatment options are not feasible, such as fusiform/blister aneurysms or wide-neck aneurysms not amenable to clipping or primary coiling 4

Alternative Treatment Approaches

• For PComm aneurysms with a non-fetal but moderate to large caliber PComm artery, conventional surgical clipping may provide better results by allowing direct visualization and preservation of the PComm artery 4
• If endovascular treatment is preferred, stent-assisted coiling may be more appropriate than flow diversion for this specific anatomical configuration 1
• For younger patients (<40 years), surgical clipping might be preferred over endovascular approaches to improve durability of treatment 4

Special Considerations for Complex Cases

• In cases where neither conventional clipping nor coiling is feasible, alternative strategies such as "anatomical flow diversion" with adjunctive techniques may be considered 5
• This might include a hybrid approach combining partial coiling with flow diversion, or competitive flow diversion strategies 6, 5
• However, these advanced techniques carry higher risks and should only be considered when conventional approaches are not feasible 4, 5

Complications and Risks

• Flow diversion in this anatomical configuration carries risks of:
  • Incomplete aneurysm occlusion requiring retreatment 2
  • Thromboembolic complications due to required dual antiplatelet therapy 1
  • Potential ischemia in the territory supplied by the PComm artery if it becomes compromised 7
• The risk-benefit ratio generally favors conventional treatment approaches (clipping or coiling) over flow diversion when technically feasible 4, 1

Follow-up Recommendations

• If flow diversion is ultimately chosen despite these concerns, more frequent and longer-term follow-up imaging is necessary to monitor for incomplete occlusion and potential retreatment 4
• Follow-up should include DSA at 6 months and then annually until complete occlusion is confirmed 4
• Long-term surveillance is warranted as delayed aneurysm occlusion may occur with flow diversion 3

Flow diversion for PComm aneurysms with incorporated moderate to large PComm arteries remains challenging, with current evidence suggesting lower efficacy and higher risks compared to conventional treatment options. The decision should be made by a multidisciplinary team with both endovascular and surgical expertise, with conventional treatment approaches preferred when technically feasible.