Blood Blister-Like and Small Aneurysms

Abstract

A blood blister-like aneurysm is a small, bleb-like, and ill-defined outpouching at non-branching sites of the intracranial internal carotid artery. The small (<3 mm) aneurysm is categorized with blister aneurysms together due to similar treatment techniques and principles. Unique challenges with blister aneurysms are reviewed. Different treatment strategies and unique technical points from other aneurysms are introduced. The strategies of the primary coiling, stent-assisted coiling, stent alone, and flow diverter treatment are discussed in detail.

Case Presentation

Case 10.1 One Single Long Coil for Small Wide-Neck Aneurysm

Case Pearls

• 1. For wide-neck small aneurysm, small finishing filling coils have potential risk of coil migration/prolapse/escape into the parent lumen.

• 2. One single “fat” long coil has advantages of maintaining high coil packing density while eliminating the risk of small finishing coil migration.

• 3. Correct size of the coil is pivotal; microcatheter tip at the neck entrance is preferred.

(a) 3D angiogram for work-up of left-side stroke showing a left PCA P1/P2 small 3 mm wide-neck aneurysm; (b) pre-embo 2D working view; (c) one single coil (Target Ultra 2.5×4) placed with coil protruding into lumen, while packing density is low with contrast filling; (d) the coil was pulled out and changed to a Target Ultra Soft 2×6 mm coil with good pack density; (e) coiling catheter tip (arrow) is at neck entrance; (f) 9-month follow-up, no recurrence

Case 10.2 Flow Diverter for Supraclinoid ICA Small Aneurysm

Case Pearls

• 1. Flow diverter is the preferred treatment option for supraclinoid ICA blister/small aneurysm.

• 2. Single flow-diverter stent without the addition of coils is preferred by most providers.

• 3. Primary coiling is more preferred for small aneurysm.

(a) Pre-embo 3D angiogram showing a right supraclinoid ICA blister/small aneurysm; (b) pre-embo 2D view for the right blister aneurysm FD stent treatment; (c) angiogram after FD stent (PED 4.5×14) for the right blister aneurysm (insert showing the contour of PED); (d) 1 month later, pre-embo 3D angiogram for treating a left 9×8 mm supraclinoid ICA narrow-neck aneurysm; (e) pre-embo 2D views for the large left aneurysm; (f) post-embo angiogram for primary coiling (Optima coils: 18 8×27, 6×20 10 coils 6×20, 4×10, 4×8, 3×10, 3×8, and Target 3×10) of left aneurysm showing Raymond-Roy occlusion classification class IIIa result (slightly contrast filling); (g–j) 9-month follow-up DSA showing complete obliteration of the right supraclinoid ICA blister aneurysm (g and h) and class IIIA to I change of the left supraclinoid ICA aneurysm (i and j)

Case 10.3 Branching Point Blister/Small Aneurysm

Case Pearls

• 1. Branching point involvement limits the possibility of primary coiling.

• 2. Outcome of FD treatment depends on the collateral flow of the branch distribution.

• 3. Multiple aneurysms and previous rupture are strong indications for the treatment of unruptured aneurysms.

(a) 3D angiogram for follow-up of previously clipping ruptured left supraclinoid ICA aneurysm showing an M2 branching point small/blister aneurysm and an ophthalmic artery aneurysm; (b) pre-embo 2D views for the best view of both aneurysms for FD stent treatment. (c) angiogram after two PED stent placement (PED, 2.5×14 for M2 aneurysm, 3.75×14 for supraclinoid ICA aneurysm); (d) contour of both PEDs; (e–g) 4-month follow-up angiogram (f: 3D angiogram) showing complete obliteration of both aneurysms; notice M2 branch still patent and the ophthalmic artery (arrow in b, c) occluded (g: un-subtracted angiogram showing contour of both PEDs)

Case 10.4 Microcatheter Tip Position for Small Aneurysms

Case Pearls

• 1. For small aneurysm, microcatheter tip placed at the neck for delivering coil is preferred for less risk of aneurysm rupture.

• 2. Good guide catheter support is paramount for small aneurysm; terminal ICA is the preferred location for the guiding catheter.

(a) 3D angiogram for work-up of SAH (insert: head CT demonstrated SAH) showing a 3.5×2 mm narrow-neck AComA aneurysm; (b, c) pre-embo 2D views for the best view of the neck and access arteries; (d–f) angiogram after the first, second, and third coil (Target Ultra 2×3, Nano 1×3, 1×2) placement, respectively (upper row, AP view; lower row, lateral view); the tip of microcatheter (arrow) is located at the neck, not deep inside aneurysm; closely watch the coil movement under fluoroscopy; (g) final run post-coiling. The patient moved back to home state; no further follow-up angiogram available

Case 10.5 Ruptured Twin Small Aneurysms Treated with Primary Coiling

Case Pearls

• 1. Primary coiling is preferred for the ruptured aneurysm to avoid DAPT.

• 2. Sealing the dome to prevent imminent re-rupture is the goal for the difficult one to treat endovascularly.

• 3. Patient age and clinical status should be considered for treatment decision-making.

(a) Presenting head CT showing SAH; (b) pre-embo 3D angiogram showing two small blister aneurysms side by side; (c) pre-embo 2D views for the best view of the neck and parent vessel relationship; (d) coiling the smaller (coil: single Target Nano 1.5×4), subtracted and un-subtracted images; (e) coiling the larger one (coils: Target XL 360 Ultra 2.5×4, Nano 1.5×3, 1×2×2), subtracted and un-subtracted images; (f) final run post-coiling, subtracted and un-subtracted images; (g) 8-month follow-up angiogram with small neck residual on the larger aneurysm, the smaller aneurysm completely obliterated, subtracted and un-subtracted images

Case 10.6 Primary Coiling for Small Aneurysm with Dome/Neck Ratio ≈ 1

Case Pearls

• 1. A small aneurysm with dome/neck ratio ≈1 (virtually no neck) is still possibly and safely coiled primarily; often a long “fat” small coil is all what is needed.

• 2. When primary coiling failed, BAC or SAC will be the bailout strategy.

(a) Pre-op AP angiogram for work-up of a questionable SAH patient showing small 3×3 basilar tip aneurysm; (b) two small coils (one “fat” coil of Target XL 2×6 and a filling coil of Nano 1×2) primary coiling embolization; (c) un-subtracted final angiogram showing complete obliteration of the aneurysm; (d–f) lateral views of the primary coiling process; (g, h) 16-month follow-up subtracted and un-subtracted AP view (g) and lateral view (h)

Case 10.7 Intraoperative Rupture of Small Aneurysm with SAC

Case Pearls

• 1. SAC is one of the options for small aneurysm not suitable for FD.

• 2. The risk of intraoperative rupture is higher for blister/small aneurysm.

• 3. The most effective way is to keep the coil/wire in place and continue coiling with more coils.

(a) 3D angiogram showing a bilobed BA tip small aneurysm; (b) pre-embo 2D views for the best view of the neck and both lobes. (c) Stent placed from one PCA to BA with jailing the coiling microcatheter; (d) coiling of large lobe with the jailed microcatheter and coils (Target 360 soft ultra, 3×15, 3×8, and 3×6); (e) single-shot X-ray showing the “go through” technique with the second coiling catheter (use the one for stent deployment; arrow: tip of microcatheter), while keep the jailed microcatheter and un-detached first coil to maintain the stability of the coil mass of bigger lobe; (f) first coil (Target soft nano 1.5×4) in the smaller lobe with minimal contrast filing (maybe we should have stopped here for acceptable result to avoid high risk of further coiling for higher packing density). (g) intraoperative rupture while putting the second coil (Target Nano 1×2) in the smaller lobe; the mistake was that the coil was pulled back out of the aneurysm; (h) after the second coil was put back again, still showing contrast extravasation although less; (i) third coil (Target Nano 1×2) placed, and bleeding stopped; (j) final run post-coiling; (k) immediate post-op CT; (l) post-op day 2 CT before discharge; (m) 2 years MRA FU; (n) 5-year follow-up, the aneurysm remains completely obliterated