Stent retriever thrombectomy with aneurysm in target vessel: Technical note

Abstract

Aneurysms within large occluded target vessels can present significant challenges for neuro interventionists because rupture can be catastrophic. We recently encountered a case of left internal carotid artery–middle cerebral artery (MCA) ischemic stroke with an incidental MCA bifurcation aneurysm that we were already aware of. IV tissue plasminogen activator (tPA) with mechanical thrombectomy (MTE) was performed with a stent retriever, proximal to the aneurysm. TICI 2b recanalization was achieved. MTE and IV tPA may not be withheld from patients with acute stroke with known target vessel aneurysms.

Introduction

The clinical effectiveness of mechanical thrombectomy (MTE) with stent retrievers in ischemic stroke due to large vessel occlusion (LVO) and its superiority over systemic thrombolysis alone has been proven in a series of large-scale randomized trials.^1–3 MTE is presently on the brink of becoming the standard treatment for LVO strokes, and the number of MTE procedures is likely to grow rapidly in the coming years. MTE with stent retrievers is generally safe, with a reasonably low rate of procedure-related complications.^4,5 Unruptured, potentially unrecognized aneurysms have a 3% incidence rate in the general population, with similar risk factors as ischemic stroke.⁶ An unknown aneurysm is a potential danger in recanalization attempts.⁷ We present a recent case where bridging tissue plasminogen activator (tPA) followed by internal carotid artery–middle cerebral artery (ICA–MCA) MTE was performed in a patient with known left MCA bifurcation aneurysm with good clinical outcome.

Case report

The patient was a 78-year-old female with previous history of ruptured right MCA aneurysm, status post clipping, and also known to have a 4 mm broad-necked unruptured left MCA aneurysm. She presented with loss of consciousness, aphasia, and right-sided weakness with a NIH stroke scale of 26. She was in atrial fibrillation. She was found to have a left ICA occlusion with significant salvageable penumbra on the CT perfusion. While the patient was being transferred to a neuro-interventional suite, IV tPA was started. We obtained access to the left ICA using a 6F Envoy guide catheter (Codman Neurovascular, Raynham, MA) and placed a Rebar 18 micro catheter (Medtronic, Irvine, California, USA) into the M1 MCA. We confirmed the position of the microcatheter with a contrast injection. The microcatheter was 1 mm proximal to the aneurysm. The catheter was withdrawn to a more proximal position and a 4 × 30 mm Solitaire stent retriever (Medtronic, Irvine, California, USA) was deployed under roadmap guidance. It took two attempts to obtain TICI 2b recanalization. We did not pursue the thrombus distal to the aneurysm in order to prevent any possible rupture. The patient regained full power in her extremities following the procedure, but still had improving Wernicke’s aphasia at the time of discharge (Figures 1–5).

Figure 1.

AP and lateral projections show static flow in the left ICA with no intracranial flow.

Figure 2.

AP and lateral projections show microcatheter angiogram outlining the left MCA aneurysm (arrows).

Figure 3.

Frontal view native image showing stent retriever (small arrow) deployment in the left MCA, proximal to the aneurysm. Right craniotomy with right MCA clip (large arrow) is seen.

Figure 4.

Frontal left carotid angiogram showing placement of the stent retriever tip in the M1 segment (proximal vertical black arrow). MCA aneurysm is outlined with contrast (horizontal arrow).

Figure 5.

Status post-thrombectomy recanalization of MCA is seen with aneurysm well visualized (arrow).

Discussion

As we enter in the era of ever increasing endovascular therapy for ischemic stroke, we are going to increasingly encounter cases where there are recognized or hidden aneurysms in target vessels or elsewhere in the intracranial circulation. These would present not only procedural challenges, as described in our case, but also in post-op care. There is very limited data on the prevalence of aneurysms in stroke patients. Edwards et al.⁷ reported that 9.5% of acute ischemic stroke patients treated with rt-PA had at least one intracranial aneurysm, and 9% of those were located within the territory of ischemia. A coincidental aneurysm prevalence rate of 3.7% in stroke patients with LVOs has been described by Zibold et al.⁸ In their study of 300 patients, most aneurysms were small (average diameter 3.8 mm).The target vessel-related prevalence was significantly higher in the anterior circulation (10/258 (3.9%)) than in the posterior circulation (1/42 (2.4%)).We agree with the authors that given the shared risk factors of arterial hypertension, smoking and age, the actual probability of coincidental aneurysms may be higher. The same authors had one complication resulting in subarachnoid hemorrhage, related to stent retriever thrombectomy. The authors attempted aspiration thrombectomy in two cases,^9,10 although with only partial success. Asai et al.,¹¹ however, were able to achieve complete recanalization of M1 occlusion of a case with left MCA bifurcation aneurysm.

Aspiration techniques may apply lower shear forces on the vessel wall than stent retrievers and can achieve recanalization without passing the thrombus and the aneurysm. However, their effectiveness in achieving recanalization rates equivalent to stent retrievers is unproven.⁸

It may be worthwhile in such cases to attempt initial aspiration attempts. If unsuccessful, stent retrievers may be considered. In our case, we knew the location of the aneurysm and that there was superior division occlusion. Prior knowledge of angiographic anatomy helped us in attempting stent retriever thrombectomy. We took care not to cross the aneurysm with the micro wire or catheter. Clearly, more distal aneurysms pose a higher risk owing to smaller vessel size, increased aneurysmal pressure following recanalization and thinner wall. The risk of injury to occluded vessels with hidden aneurysms has been reported by two cases of rupture during local intra-arterial fibrinolysis^12,13 and reported cases of perforation during MTE.^8,14

We suggest spending time on the prior available imaging, be it CT/MRI or angiograms, before attempting any stroke interventions. Also, it is prudent to have some pre-procedure cross-sectional imaging (CT perfusion or MRI). In their retrospective analysis, Zibold et al. found that aneurysms were visible in 6/11 cases in pretreatment studies, although four were not recognized by the radiologist or the treating interventionist.⁸ On interventions which are essentially without any prior imaging, we suggest attempting the ADAPT technique¹⁵ or going in with a J curve to the micro wire in order to minimize the chances of entering a small MCA aneurysm.

We want to stress the importance of looking very carefully at the pre-contrast images to visualize any focal high-density contour abnormality in the cisterns. Early CT angiography (CTA) images are very helpful to see any aneurysms in patent vessels proximal or distal to the occlusion. If the contour abnormality is part of the occluded vessel, it could be a thrombosed aneurysm. Often, on the delayed CT angiogram images these aneurysms may fill with contrast through collaterals.

To summarize, each case needs individualized treatment depending on the location of the aneurysm and the extent of the thrombus. This report also emphasizes need for cross-sectional imaging, such as CTA, before attempting any cerebrovascular intervention. Also, anticipating a scenario like this should help us explain this to patients and their families while taking informed consent for the thrombectomies.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.