Endovascular Management of Wide Neck Aneurysms

Definition and Challenges

• Wide neck aneurysms are typically defined as those with a neck diameter >4mm or a dome-to-neck ratio <2:1, making them technically challenging for standard endovascular coiling 1
• These aneurysms pose a higher risk of coil herniation into the parent vessel and have higher rates of incomplete occlusion and recurrence compared to narrow-necked aneurysms 2

Assessment and Planning

• Accurate assessment of aneurysm morphology requires optimal orthogonal arteriographic projections or rotational angiography with 3D reconstructions 1
• The relationship between parent artery diameter and aneurysm neck size is a critical factor in determining the need for adjunctive techniques 3
• Complete aneurysm obliteration should be the goal of treatment whenever possible to reduce rebleeding risk 4, 5

Endovascular Techniques for Wide Neck Aneurysms

• Stent-assisted coiling involves deploying a self-expandable stent across the aneurysm neck to create a scaffold that prevents coil herniation into the parent vessel 6, 4
• Balloon remodeling technique involves temporary balloon inflation across the aneurysm neck during coil deployment, followed by balloon deflation and removal after coiling, and is particularly useful for wide-neck aneurysms where parent vessel preservation is critical 3, 4
• Flow-diverting stents are low-porosity stents designed to redirect flow away from the aneurysm while providing a scaffold for endothelial growth, and may represent a better option for many saccular aneurysms 4

Follow-Up Considerations

• Aneurysm recurrence is not uncommon after endovascular coiling and may occur even in aneurysms that appear completely occluded initially 7
• Long-term angiographic monitoring is mandatory after endovascular treatment, with follow-up imaging at 6 months and then annually recommended 7

Decision-Making Algorithm

• The American Heart Association recommends assessing aneurysm morphology, including neck size, dome-to-neck ratio, and parent vessel relationship, to determine the best treatment approach 3
• For wide neck aneurysms, the American Stroke Association suggests considering stent-assisted coiling, balloon remodeling, or flow-diverting stents, depending on the patient's condition and the aneurysm's characteristics 4

Pitfalls and Caveats

• Dual antiplatelet therapy required for stent placement increases hemorrhagic risk, especially in the setting of subarachnoid hemorrhage, according to the American Heart Association 4
• Complete aneurysm occlusion is less likely in larger aneurysms with wide necks, and additional embolizations are often required during follow-up, as noted by the American Stroke Association 7
• The risk of recanalization is higher with endovascular treatment compared to surgical clipping, highlighting the need for careful patient selection and multidisciplinary decision-making, as recommended by the American Heart Association 4

Definitions and Measurement Criteria for Intracranial Aneurysm Neck Geometry

1. Neck Width Classification

• A narrow-neck aneurysm is defined by a maximum neck width ≤ 4 mm, whereas a wide-neck aneurysm has a neck width > 4 mm. 8, 9

2. Dome‑to‑Neck Ratio

• A dome‑to‑neck ratio ≥ 2 : 1 indicates geometry favorable for simple coiling. 8
• A dome‑to‑neck ratio < 2 : 1 classifies the aneurysm as wide‑neck. 8, 9

3. Parent Artery‑to‑Neck Relationship

• The ratio between parent artery diameter and aneurysm neck size influences treatment planning; a 4‑mm neck with a 2‑mm parent artery suggests the need for adjunctive devices even when the dome‑to‑neck ratio appears favorable. 8

4. Imaging Requirements for Accurate Measurement

• Catheter cerebral arteriography provides the highest spatial resolution for assessing dome‑to‑neck ratio, neck‑to‑artery ratio, and precise aneurysm dimensions. 10, 9
• Optimal orthogonal arteriographic projections or rotational angiography with 3‑D reconstructions are essential for reliable measurements. 8

5. Anatomical and Morphological Considerations

• Multilobulated or complex‑shaped aneurysms pose challenges for volume analysis and should be described separately in reports. 8
• Aneurysms lacking a definable neck with distinct inflow and outflow tracts do not fit standard neck definitions and require alternative characterization. 9, 11

Intracranial Aneurysm Morphology Definitions and Assessment

Definition of Wide‑Neck Aneurysm

• A wide‑neck aneurysm is defined as having a neck diameter greater than 4 mm or a dome‑to‑neck ratio less than 2 : 1; this geometry is considered technically challenging for simple coil embolization. 12

Favorable Dome‑to‑Neck Geometry for Simple Coiling

• A dome‑to‑neck ratio of ≥ 2 : 1 indicates a morphology that is favorable for endovascular coil occlusion without the need for adjunctive devices. 12

Poor Dome‑to‑Neck Relationship

• A poor dome‑to‑neck relationship refers to aneurysms with a dome‑to‑neck ratio < 2 : 1, especially those with a ratio < 1.2, which are deemed unfavorable for standard endovascular treatment. 12

Influence of Parent‑Artery Diameter on Device Selection

• The diameter of the parent artery relative to the aneurysm neck is a critical discriminator; for example, a 4‑mm neck adjoining a 2‑mm parent artery may still require adjunctive devices (e.g., stent or balloon assistance) even when the dome‑to‑neck ratio appears favorable. 12

Imaging Requirements for Accurate Morphologic Measurements

• Precise assessment of dome‑to‑neck and related ratios requires optimal orthogonal arteriographic projections or rotational angiography with three‑dimensional reconstructions to ensure accurate dimensional data. 12

Reporting of Multilobulated or Complex‑Shaped Aneurysms

• Aneurysms that are multilobulated or have complex shapes pose challenges for volumetric analysis and should be described separately in imaging reports. 12