Microsurgical partial trapping for the treatment of unclippable vertebral artery aneurysms: Experience from 27 patients and review of literature

Abstract

Background: The efficacy and safety of partial trapping for the treatment of unclippable vertebral artery aneurysms (UVAs) are still questionable. The partial trapping method (proximal or distal occlusion) was used in the treatment of aneurysms to simplify the surgical procedure and avoid postoperative complications.

Methods: This study included 27 patients with UVAs who underwent microsurgical partial trapping between January 2015 and August 2022, and their postoperative outcomes and complications were retrospectively reviewed and evaluated.

Results: Ruptured UVAs were detected in 25 (92.6%) patients, and 13 (48.1%) patients had poor-grade status. Fusiform dissection, dissecting, and fusiform aneurysms were observed in 17 (63%), 7 (25.9%), and 3 (11.1%) patients, respectively. By location, preposterior inferior cerebellar artery (PICA), PICA, post- PICA, and non-PICA types were noted in 7 (25.9%), 9 (33.3%), 6 (22.2%), and 5 (18.5%) patients, respectively. Microsurgical partial trapping was performed in all patients (blind-alley formation in 96.3%). Complete aneurysm obliteration was achieved in 26 (96.3%) patients. Immediate complete obliteration was achieved in 21 (77.8%) patients, delayed thrombosis within 7 days in 5 (18.5%), and nearly complete obliteration in 1 (3.7%). No re-bleeding was detected in all patients. Favorable outcomes 3 months after the operation were achieved by 92.9% of the patients in the good-grade group and 85.2% overall.

Conclusions: Microsurgical partial trapping, especially the blind-alley formation technique, was a safe and effective treatment of UVAs with high rates of aneurysm thrombosis. The appropriate sites for clip occlusion were dependent on the angioarchitecture of UVAs.

Keywords: Blind-alley formation; Incomplete trapping; Microsurgery; Partial trapping; Unclippable aneurysm; Vertebral artery aneurysm.

Fig. 1

Proximal occlusion at different locations and mechanisms of aneurysm thrombosis.

Fig. 2

Distal occlusion at different locations and mechanisms of aneurysm thrombosis.

Fig. 3

Illustrative case 1 (patient 9) (A) Diffuse subarachnoid hemorrhage (SAH) with premedullary predominance (arrow) was detected by computed tomography (CT) (B, C) A dissecting aneurysm of the right vertebral artery (arrow) without the posterior inferior cerebellar artery (PICA) was detected by computed tomography angiography (CTA) (D) A straight skin incision (arrow) was used for the right transcondylar approach (E, F) Dissecting segment (arrow) was found intraoperatively (F) Proximal clip occlusion of the V4 segment of the right vertebral artery was performed (G) Complete thrombosis of the aneurysm was shown in CTA immediately after the operation.

Fig. 4

Illustrative case 2 (patient 13) (A) Computed tomography (CT) showed a diffuse subarachnoid hemorrhage (SAH)with predominance in the right cerebellomedullary cistern (arrow) (B, C) A dissecting aneurysm of the right vertebral artery (arrow) with PICA involvement (asterisk) was detected by computed tomography angiography (CTA) (D) An L-shaped incision and the right transcondylar approach were performed (E) Right occipital artery (white arrow)–PICA (arrowhead) anastomosis (red arrow) was performed (F) The dissecting segment was found intraoperatively (G) Proximal clipping of the V4 segment (arrowhead) and clip occlusion of the PICA origin (arrow) were performed (H) Complete obliteration of the dissection and good patency of the bypass graft (arrow) were detected by CTA immediately after the operation. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 5

Illustrative case 3 (patient 24) (A) A thick subarachnoid clot at the right cerebellopontine cistern was detected on computed tomography (CT) (B, C) A fusiform aneurysm at the V4 segment of the right vertebral artery which deviated across the midline to the left side was detected by computed tomography angiography (CTA) (D) The left (contralateral) transcondylar approach with right V3 exposure was performed with a large L-shaped skin incision (E) A small perforator (arrow) originates from the midportion of the aneurysm (F) A large perforator (arrow) originates from the proximal aneurysm neck (G) Distal clip occlusion was performed at V4 just distal to the aneurysm (H) Immediate postoperative CTA showed complete aneurysm obliteration.

Fig. 6

Flow replacement bypass and cervical internal carotid artery (ICA) ligation for a giant cavernous ICA aneurysm (A) The aneurysm thrombosis was induced by blind-alley formation (B) With the presence of a persistent trigeminal artery (PTA), the mechanism of aneurysm thrombosis was changed to flow reversal. A1, first segment of the anterior cerebral artery; BA, basilar artery; M1, first segment of the middle cerebral artery; OphA, ophthalmic artery; PCA, posterior cerebral artery; VA, vertebral artery; arrow, direction of blood flow.

Fig. 7

Microsurgical treatment of unclippable vertebral artery (UVA) aneurysms with posterior inferior cerebellar artery (PICA) involvement (A) Proximal occlusion of the VA and PICA origin led the aneurysm into the blind alley (B) The proximal occlusion at the VA alone induces retrograde flow (flow reversal) to the aneurysm and PICA. BA, basilar artery; OA, occipital artery.

Fig. 8

Proximal (A, B) and distal (C, D) occlusion for the aneurysm with a branch origin adjacent to (A, C) or from the aneurysm (B, D). The blood flow to the branch transforms the aneurysm into a side-wall saccular aneurysm.