Abstract

Background: Mechanical thrombectomy (MT) for vessel occlusion near an aneurysm carries the risk of aneurysm rupture due to mechanical stress during the procedure. We report a case of MT performed for M2 occlusion that sharply branched from M1 near the aneurysm.

Case Description: A 73-year-old woman presented with a left middle cerebral artery (MCA) bifurcation aneurysm, exhibiting right-sided hemiparesis and aphasia. MT was performed for M2 occlusion, which sharply branched from M1 near the MCA bifurcation aneurysm. Lesion crossing was carefully performed, and a stent retriever was deployed at the occlusion site. Using a stent retriever as an anchor, a bent-tip aspiration catheter was guided past the aneurysm to the proximal end of the thrombus. A combined technique, during which the stent retriever was retracted into the aspiration catheter, was used. This approach minimized mechanical stress on the aneurysm and helped achieve effective recanalization.

Conclusion: In cases of vessel occlusion with a proximal cerebral aneurysm, a combined technique of retracting a stent retriever into an aspiration catheter positioned distal to the aneurysm after stent retriever deployment may help reduce the mechanical stress on the aneurysm during MT and provide a safer approach.

Keywords: Aneurysm, Aspiration catheter, Combined technique, Stent retriever, Thrombectomy

INTRODUCTION

The prevalence of intracranial aneurysms is approximately 3.2%.[ 14 ] Due to shared risk factors such as hypertension and advanced age, the prevalence is even higher in patients with a history of ischemic strokes, with reported incidences of 6.6–9.3%.[ 4 , 10 ] Since 2015, when multiple randomized controlled trials demonstrated the efficacy of mechanical thrombectomy (MT) for acute ischemic stroke caused by large vessel occlusion (LVO), MT has rapidly become a widely adopted treatment procedure. Consequently, the number of LVO cases involving target vessels with intracranial aneurysms is expected to increase.[ 2 , 3 , 6 ] Intraoperative aneurysm rupture is a serious complication of endovascular treatment. Therefore, more meticulous techniques are required when performing MT on target vessels with associated aneurysms. Herein, we report a case of M2 occlusion sharply branching from M1 near a middle cerebral artery (MCA) bifurcation aneurysm. This procedure involved anchoring a stent retriever and guiding the aspiration catheter with a bent tip past the aneurysm to the proximal end of the thrombus. A combined technique, which involved retracting the stent retriever into the aspiration catheter, was used to minimize the mechanical stress on the aneurysm. This strategy allowed for safe and effective MT. The details of this treatment approach are also discussed.

CASE REPORT

History and examination

The patient was a 73-year-old woman with a history of atrial fibrillation presented with an unruptured MCA bifurcation aneurysm during outpatient follow-up at our institution [ Figure 1a ]. The MCA aneurysm showed no evidence of cortical embedding [ Figure 1b ]. Head computed tomography (CT) angiography revealed a steep branching angle of the left M2 inferior trunk from M1 with the aneurysm [ Figure 1c ]. On the 2^nd day of hospitalization for bilateral occipital lobe infarctions, the patient suddenly developed aphasia and right hemiparesis 10 min after being assessed as normal. The patient had a Glasgow coma scale score of E2V1M3, right hemiparesis, and motor aphasia, with a National Institutes of Health Stroke Scale score of 24. Diffusion-weighted imaging (DWI) performed 24 min after the last known normal assessment showed localized fresh ischemic changes in the left MCA territory, with a DWI-Alberta Stroke Program Early CT Score of 7 [ Figure 1d ]. Magnetic resonance angiography (MRA) confirmed the occlusion of the left M2 inferior trunk. To further evaluate the occlusion site, head CT angiography was performed, which revealed an occlusion of the left M2 inferior trunk sharply branching from the M1 near the MCA bifurcation aneurysm. The origin of the occluded vessel could not be determined [ Figure 1e ]. Although a wide penumbra was present in the left M2 territory, concerns regarding mechanical stress on the aneurysm during MT delayed the initiation of the procedure. MT was initiated 108 min after the last known normal time point.

Figure 1:

Initial imaging findings before endovascular surgery. (a) Axial image of magnetic resonance (MR) angiography reveals a left middle cerebral artery bifurcation aneurysm (arrowhead). (b) MR IMAGING Volume I Sotropic Tse Acquisition reveals no evidence of aneurysm embedding (arrowhead) into the cerebral lobes. (c) Pre-onset computed tomography (CT) angiography indicates a steep branching angle of the left M2 inferior trunk (arrow), arising from the aneurysm, relative to M1. (d) At onset, diffusion-weighted imaging (DWI) shows faint hyperintensity in the perfusion territory of the left middle cerebral artery. The DWI-Alberta stroke program early CT score is 7 points. (e) At onset, CT angiography reveals occlusion of the left M2 inferior trunk (arrow). The origin of the occluded vessel is not visible.

Endovascular treatment

Under local anesthesia, an 8-Fr OPTIMO (Tokai Medical Products, Aichi, Japan) was placed in the left internal carotid artery through the right femoral artery. Left internal carotid angiography revealed occlusion of the left M2 inferior trunk, which is a branch of the left M1 near the MCA bifurcation aneurysm [ Figures 2a and b]. A 5-Fr SOFIAFLOW (Terumo Corporation, Tokyo, Japan) was positioned in the left MCA M1 segment. A Phenom21 microcatheter (Medtronic, Minneapolis, Minnesota, USA) and a Traxcess microguidewire (Terumo Corporation, Tokyo, Japan) were advanced toward the occlusion site in the left M2 inferior trunk. However, due to the steep branching angle between the M1 and the M2 inferior trunk, the microcatheter could not be navigated into the M2 occlusion. The microcatheter was replaced with a Phenom17 preshaped 90° (Medtronic); however, the occlusion site remained inaccessible. Subsequently, a Headway17 (Terumo Corporation, Tokyo, Japan) microcatheter was introduced and steam-shaped into a pigtail configuration to facilitate advancement of the microguidewire. The Headway17 tip was successfully guided to the proximal side of the occlusion [ Figure 2c ]. After changing the microguidewire to a CHIKAI 10 (Asahi Intecc, Aichi, Japan) and applying torque, the microguidewire crossed the occlusion, and Headway17 was advanced distally into the left M2 inferior trunk [ Figure 2d ]. A Solitaire X 3 mm × 40 cm stent retriever (Medtronic) was deployed from the left M2 inferior trunk to the distal M1 segment. Using the stent retriever as an anchor, the SOFIAFLOW aspiration catheter was guided beyond the aneurysm toward the proximal thrombus. However, the catheter tended to direct stress toward the aneurysm and thus could not be advanced from the distal M1 segment [ Figure 2e ]. Solitaire X was left in place while Headway17 and SOFIAFLOW were withdrawn. Using the Solitaire X pusher wire as a guide, a steam-shaped Vecta46 (Stryker) aspiration catheter with a J-tip was introduced. To minimize the mechanical stress on the aneurysm, tension was applied to the Solitaire pusher wire while advancing the Vecta46 along the lesser curvature of the bend. This allowed the Vecta46 to pass beyond the aneurysm and reach the proximal end of the thrombus in the left M2 inferior trunk [ Figure 2f ]. With the internal carotid artery flow arrest and aspiration applied to the Vecta46, the Solitaire X was retracted into the Vecta46 at the proximal end of the thrombus [ Figure 2g ]. A red thrombus was attached to the Solitaire X [ Figure 2h ]. The wedge obstruction persisted but was eventually resolved in the siphon segment of the internal carotid artery by gently retracting the Vecta46 under mild aspiration, ensuring that no stress was placed on the aneurysm. No thrombi were observed inside the aspiration catheter. Left internal carotid angiography revealed that although a branch of the left M2 inferior trunk remained occluded, effective recanalization of the M2 inferior trunk was achieved [ Figure 2i ]. Final angiography revealed thrombolysis in cerebral infarction (TICI) grade 2b recanalization [ Figure 2j ]. The time from puncture to recanalization was 183 min.

Figure 2:

Imaging findings during endovascular surgery. (a and b) Left internal carotid artery angiography depicts a middle cerebral artery bifurcation aneurysm and occlusion of the left M2 inferior trunk. (b) is a magnified view of the frontal working angle. (c) A Headway17 microcatheter, steam-shaped into a pigtail configuration, is positioned proximal to the occlusion site. (d) A CHIKAI10 microguidewire and Headway17 microcatheter are advanced distally into the left M2 inferior trunk. (e) During advancement of the SOFIAFLOW aspiration catheter, anchored by a stent retriever deployed from the M2 inferior trunk to the distal M1, the aspiration catheter could not be advanced due to its orientation toward the aneurysm. (f) After switching to a bent-tip Vecta46 aspiration catheter, successful navigation to the proximal end of the thrombus in the left M2 inferior trunk was achieved. (g) The SolitaireX 3 mm × 40 cm stent retriever is retracted into the Vecta46 aspiration catheter. Angiography confirms that the Vecta46 does not interfere with the aneurysm. (h) Retrieved red thrombus. (i) Effective recanalization is achieved despite the continued occlusion of a branch of the left M2 inferior trunk. (j) Left internal carotid artery angiography shows thrombolysis in cerebral infarction grade 2b recanalization.

Postoperative course

XperCT performed immediately after the procedure showed no intracranial hemorrhage. However, a small amount of subarachnoid hemorrhage was observed in the left Sylvian fissure on the head CT performed the following day [ Figure 3a ]. DWI performed on the same day revealed an infarction in the M2 inferior trunk territory [ Figure 3b ], whereas MRA showed good visualization of the left M2 inferior trunk [ Figure 3c ]. The patient’s right hemiparesis improved, but sensory aphasia persisted. On day 14 after onset, the patient was transferred to a rehabilitation hospital with a modified Rankin scale (mRS) score of 4. The mRS at 90 days was 3.

Figure 3:

Postoperative imaging findings. (a) Non-contrast head computed tomography (CT) on the day after surgery shows a small amount of subarachnoid hemorrhage in the left Sylvian fissure (arrowhead). (b) Diffusion-weighted imaging on the day after surgery reveals an infarction in the left M2 inferior trunk territory. (c) Magnetic resonance angiography on the day after surgery demonstrates patency of the left M2 inferior trunk.

DISCUSSION

This case represents a rare instance of M2 occlusion arising at a sharp angle from M1 near a MCA bifurcation aneurysm. The procedure posed a risk of aneurysm rupture due to mechanical stress induced by stent retriever retraction and aspiration catheter guidance. To mitigate this risk, we employed a combined approach: a stent retriever was deployed distally, and an aspiration catheter with a bent tip was guided across the aneurysm to the proximal end of the thrombus using the stent retriever as an anchor. The stent retriever was subsequently retracted into the distally positioned aspiration catheter. This approach effectively minimized mechanical stress on the aneurysm during stent retriever retraction and aspiration catheter guidance, enabling successful recanalization without aneurysm rupture.

In patients with LVO undergoing MT, Oshikata et al. reported the presence of aneurysms in 7 out of 240 cases (2.9%),[ 11 ] while Zibold et al. identified aneurysms in 11 out of 300 cases (3.6%).[ 16 ] Aneurysms within the target vessel during MT can be categorized as either proximal or distal to the occlusion site. Proximal aneurysms are typically detectable on preprocedural imaging, whereas distal aneurysms often remain undiagnosed before the procedure. This lack of recognition increases the risk of aneurysm perforation and rupture during microcatheters or microguidewires manipulation.[ 11 ] Regarding treatment, stent retrievers may induce shear stress on the aneurysm wall during retraction, potentially leading to wall rupture. Zibold et al. reported a case of severe subarachnoid hemorrhage caused by aneurysm rupture during stent retriever use in an M1 occlusion involving an unrecognized MCA bifurcation aneurysm.[ 16 ] The A Direct Aspiration First Pass Technique (ADAPT) approach, compared to stent retrievers, may reduce shear stress on the vessel wall and facilitate recanalization without passing through the thrombus or aneurysm.[ 13 ] Successful recanalization without hemorrhagic complications has been reported in cases of MCA occlusion with distal aneurysms using ADAPT.[ 1 ] In Oshikata et al.’s series of seven cases, ADAPT was the initial approach in five; however, three required the adjunct use of stent retrievers due to failed recanalization with ADAPT alone.[ 11 ] Similarly, in Zibold et al.’s study, ADAPT was the first-line technique in two cases with pre-identified aneurysms, but neither achieved successful recanalization.[ 16 ] These findings highlight that certain cases are challenging to recanalize using ADAPT alone, necessitating adjunctive stent retriever use. Minimizing mechanical stress on the aneurysm wall during such procedures is crucial to reduce the risk of complications. In this case, the branching angle of the M2 segment from the aneurysm was steep relative to M1, complicating aspiration catheter guidance and its contact with the thrombus. In addition, advancing the aspiration catheter using the microguidewire and microcatheter axis risked applying mechanical stress to the aneurysm on the greater curvature. Stent retriever anchors have been reported to provide superior catheter guidance compared to microcatheter axes.[ 7 , 8 ] Therefore, in this case, a stent retriever deployed distally was used as an anchor to guide a bent-tip aspiration catheter to the proximal end of the thrombus.

There are various variations of the combined technique. Broadly, these can be categorized into two main approaches: The pinching technique, where the aspiration catheter and stent retriever are treated as a single unit to sandwich and retrieve the thrombus, and the ingestion technique, where the aspiration catheter is kept stationary at the proximal end of the thrombus, and the thrombus retrieved by the stent retriever is retracted into the aspiration catheter. Representative of the former is the Continuous Aspiration Prior to Intracranial Vascular Embolectomy method,[ 9 ] while the latter is exemplified by the A Stent-Retrieving into an Aspiration Catheter with Proximal Balloon (ASAP) method.[ 5 ] The ASAP method has been reported to have a low risk of hemorrhagic complications. In this case, to minimize mechanical stress on the aneurysm wall from the stent retriever, the ASAP method was employed. The stent retriever was deployed sufficiently distally to act as an anchor for guiding the aspiration catheter. Initially, SOFIAFLOW (with a distal outer diameter of 1.7 mm) was used as the aspiration catheter, but it could not pass through the origin of the M2 inferior trunk. Therefore, it was replaced with the smaller-diameter Vecta46 (with a distal outer diameter of 1.43 mm), and the tip was steam-shaped into a J-configuration. The aspiration catheter was successfully guided distal to the aneurysm using the mini-pinning technique,[ 15 ] and the stent retriever was completely retracted into the aspiration catheter. This approach minimized mechanical stress on the aneurysm wall and achieved effective recanalization.

Intracranial aneurysms are often adhered to surrounding tissues and, in some cases, may be embedded within cerebral lobes. During aneurysm clipping surgery, a high degree of embedding in the cerebral lobes can increase stress on the aneurysm wall during lobe retraction, increasing the risk of intraoperative rupture. In this case, postoperative imaging revealed a small amount of subarachnoid hemorrhage, suggesting that the MCA may have been displaced during stent retriever retraction, potentially exerting tensile force on the aneurysm. However, because the aneurysm in this case was not embedded within the cerebral lobes, it did not experience forces that could separate it from the lobes and cause rupture. In cases where aneurysms are deeply embedded in the cerebral lobes, the risk of rupture during stent retriever retraction may be significantly higher.

In this case, although a wide penumbra was identified in the left M2 occlusion territory, concerns regarding the mechanical stress on the aneurysm during MT caused significant delays in initiating the procedure. Intraoperative maneuvers were performed with extreme caution to minimize stress to the aneurysm and additional time was required to determine procedural modifications. Consequently, while effective recanalization was eventually achieved, the prolonged time to recanalization resulted in poor clinical outcome for the patient. Although aneurysm rupture during endovascular treatment is a major concern, it can be mitigated by selecting appropriate approaches and devices tailored to the location of the aneurysm and occlusion site, enabling safer MT.[ 12 ] Preprocedural imaging assessments, including CT, magnetic resonance imaging, and angiography, are strongly recommended to guide treatment planning.[ 11 , 12 ] In this case, earlier consideration of a treatment strategy based on preprocedural imaging may have improved the patient’s outcome. Specifically, the steep branching angle of the M2 segment relative to M1 could have been addressed by deploying a stent retriever distally as an anchor to guide a bent-tip aspiration catheter past the aneurysm. Advancing the aspiration catheter distal to the aneurysm and retracting the stent retriever into the catheter would have minimized the mechanical stress on the aneurysm, potentially leading to a more favorable clinical course.

CONCLUSION

In vessel occlusion accompanied by a proximal cerebral aneurysm, a combined technique in which a stent retriever is retracted into an aspiration catheter positioned distal to the aneurysm after stent retriever deployment may help minimize mechanical stress on the aneurysm and enhance the safety of MT.

Ethical approval:

The Institutional Review Board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

References

1. Asai K, Nakamura H, Sakaguchi M, Kawano T, Ozaki T, Ima H. Direct aspiration first pass technique for a middle cerebral artery occlusion with a hidden aneurysm. Interv Neuroradiol. 2015. 21: 700-2

2. Berkhemer OA, Fransen PS, Beumer D, Van Den Berg LA, Lingsma HF, Yoo AJ. A randomized trial of intraarterial treatment for acute ischemic stroke. N Engl J Med. 2015. 372: 11-20

3. Campbell BC, Mitchell PJ, Kleinig TJ, Dewey HM, Churilov L, Yassi N. Endovascular therapy for ischemic stroke with perfusion-imaging selection. N Engl J Med. 2015. 372: 1009-18

4. Edwards NJ, Kamel H, Josephson SA. The safety of intravenous thrombolysis for ischemic stroke in patients with pre-existing cerebral aneurysms: A case series and review of the literature. Stroke. 2012. 43: 412-6

5. Goto S, Ohshima T, Ishikawa K, Yamamoto T, Shimato S, Nishizawa T. A stent-retrieving into an aspiration catheter with proximal balloon (ASAP) technique: A technique of mechanical thrombectomy. World Neurosurg. 2018. 109: e468-75

6. Goyal M, Demchuk AM, Menon BK, Eesa M, Rempel JL, Thornton J. Randomized assessment of rapid endovascular treatment of ischemic stroke. N Engl J Med. 2015. 372: 1019-30

7. Gross BA, Hudson JS, Tonetti DA, Desai SM, Lang MJ, Jadhav AP. Bigger is still better: A step forward in reperfusion with react 71. Neurosurgery. 2021. 88: 758-62

8. Li J, Ribo M. REACT aspiration catheters: Clinical experience and technical considerations. Neurointervention. 2022. 17: 70-7

9. McTaggart RA, Tung EL, Yaghi S, Cutting SM, Hemendinger M, Gale HI. Continuous aspiration prior to intracranial vascular embolectomy (CAPTIVE): A technique which improves outcomes. J Neurointerv Surg. 2017. 9: 1154-9

10. Oh YS, Lee SJ, Shon YM, Yang DW, Kim BS, Cho AH. Incidental unruptured intracranial aneurysms in patients with acute ischemic stroke. Cerebrovasc Dis. 2008. 26: 650-3

11. Oshikata S, Harada K, Ikema A, Kajihara M, Fujimura H, Fukuyama K. Mechanical thrombectomy for acute cerebral large vessel occlusions involving a cerebral aneurysm in the target vessel. J Neuroendovasc Ther. 2021. 15: 8-13

12. Singh J, Wolfe SQ. Stent retriever thrombectomy with aneurysm in target vessel: Technical note. Interv Neuroradiol. 2016. 22: 544-7

13. Turk AS, Frei D, Fiorella D, Mocco J, Baxter B, Siddiqui A. ADAPT FAST study: A direct aspiration first pass technique for acute stroke thrombectomy. J Neurointerv Surg. 2014. 6: 260-4

14. Vlak MH, Algra A, Brandenburg R, Rinkel GJ. Prevalence of unruptured intracranial aneurysms, with emphasis on sex, age, comorbidity, country, and time period: A systematic review and meta-analysis. Lancet Neurol. 2011. 10: 626-36

15. Yoshimoto T, Tanaka K, Koge J, Shiozawa M, Yamagami H, Inoue M. Blind exchange with mini-pinning technique using the tron stent retriever for middle cerebral artery M2 occlusion thrombectomy in acute ischemic stroke. Front Neurol. 2021. 12: 667835

16. Zibold F, Kleine JF, Zimmer C, Poppert H, Boeckh-Behrens T. Aneurysms in the target vessels of stroke patients subjected to mechanical thrombectomy: Prevalence and impact on treatment. J Neurointerv Surg. 2016. 8: 1016-20