Successful recanalization using the Embolus Retriever with Interlinked Cage for acute stroke due to calcified cerebral emboli

Abstract

Mechanical thrombectomy is a safe and effective treatment in patients with acute ischemic stroke caused by large vessel occlusions. However, in rare cases, the procedure may be challenging due to the composition of the embolus. We describe a case of a mechanical thrombectomy with the Embolus Retriever with Interlinked Cage (ERIC) device in a patient with an acute ischemic stroke due to calcified cerebral emboli in the middle cerebral artery. The procedure was done after a failed recanalization attempt with manual aspiration thrombectomy.

An 82-year-old woman presented to the emergency department with a sudden onset of right-sided weakness. A computed tomographic angiography showed left middle cerebral (M1 branch) calcified emboli. After the administration of an intravenous thrombolytic agent, the patient was transferred to the angiographic suite for a mechanical thrombectomy. After failure to recanalize the vessel with manual aspiration thrombectomy, successful recanalization was achieved via mechanical thrombectomy using the ERIC device.

Mechanical thrombectomy with an ERIC device can be a useful option in cases of acute ischemic stroke caused by calcified cerebral emboli.

Introduction

Mechanical thrombectomy is considered to be a safe and effective treatment modality for large vessel occlusions in patients who present with acute ischemic stroke (AIS).^1,2 Although mechanical thrombectomy is associated with a high recanalization rate, several factors may impede successful recanalization, including vascular tortuosity, the location of the occlusion and the thrombus burden. Thrombus composition or consistency may also affect recanalization success.³ Calcified cerebral emboli (CCE), in particular, have lower rates of recanalization success using mechanical thrombectomy as compared to atherogenic or cardiogenic emboli.^4,5 We present a case of an AIS due to CCE in which successful recanalization was achieved using the Embolus Retriever with Interlinked Cage (ERIC; MicroVention, Tustin, California) device.

Case presentation

An 82-year-old woman with hypertension presented to the emergency department at our institution with a sudden onset of right-sided weakness and loss of consciousness. Her National Institutes of Health Stroke Scale (NIHSS) score was 13 with a symptom onset-to-door time of 90 minutes. The patient was a non-smoker, and her only medication was an anti-hypertensive drug, which she had used for 20 years.

The patient’s initial non-contrast brain computed tomography (CT) scan showed a small round calcified lesion measuring approximately 3.7 mm in the left distal M1 branch of the middle cerebral artery (MCA). The mean Hounsfield unit (HU) of the lesion by drawing a small circular region of interest was 141 (Figure 1(a)). Subsequent cervical and brain CT angiography showed a left M1 branch occlusion of the MCA (Figure 1(b)). A dose of intravenous recombinant tissue plasminogen activator (IV tPA; 0.9 mg/kg) was administered to the patient prior to preparation for the mechanical thrombectomy.

Figure 1.

An 82-year-old woman with calcified cerebral emboli in the distal M1 branch of the left middle cerebral artery. (a) A non-contrast brain computed tomography (CT) scan showed a 3.7-mm oval-shaped lesion with hyperattenuation (arrow, 141 Hounsfield unit). (b) CT angiography showed a left distal M1 occlusion.

The mechanical thrombectomy was performed under conscious sedation. After a right femoral artery puncture, a 100-cm 8 French guide catheter (Guider Softip; Stryker, Natick, MA, USA) was advanced to the left cervical portion of the internal carotid artery. The initial cerebral angiogram showed an occlusion of the M1 branch of the MCA with delayed images of the leptomeningeal collaterals (Figure 2 (a) and (b)). Under the roadmap guidance, a 4MAX Penumbra reperfusion (Penumbra, Alameda, CA, USA) catheter was advanced to the level of the thrombus triaxially over a Headway 17 microcatheter (MicroVention, Tustin, CA, USA) and Synchro 0.014-in guide wire (Stryker, Fremont, CA, USA) for manual aspiration thrombectomy (MAT). MAT did not remove the calcified emboli so we next attempted mechanical thrombectomy using the ERIC device. The Headway 17 microcatheter was advanced over the microwire through the calcified lesion, and the microwire was then exchanged for the ERIC device. The ERIC device was deployed a few millimeters distally to the thrombus (Figure 2(c)). Next, the ERIC device and the microcatheter were immediately withdrawn allowing the calcified emboli to be removed by capture within the sphere of the ERIC device (Figure 2(d)).

Figure 2.

Distal subtraction angiography. (a) Initial angiography showed an M1 occlusion. (b) Delay images showed leptomeningeal collaterals from the anterior cerebral artery (arrows). (c) The tip of the Headway 17 microcatheter (arrow) and the deployed ERIC device (arrow heads). (d) The retrieved calcified emboli in the interlinked cage of the ERIC device. (e) The final angiography showed complete recanalization.

A post-procedural angiography demonstrated complete revascularization (Figure 2(e)) with no immediate or delayed procedure-related complications. The post-procedural course was uneventful, and the patient was transferred to a rehabilitation hospital after a 28-day hospitalization. The discharge NIHSS score improved from 13 to 4, and the patient showed favorable functional outcomes at three months (with a modified Rankin scale of 1).

Discussion

First described in 1981 after being documented on a brain CT scan, CCE are rarely reported emboli, accounting for 1–3% of all acute large artery occlusions.^4,6,7 CCE are an uncommon cause of AIS but are associated with more severe stroke symptoms compared to those seen with other type of emboli, such as fibrous emboli, which are probably due to a different embolus composition.⁸ Prompt diagnosis and rapid reperfusion therapy are essential in improving the prognosis in patients presenting with an AIS due to CCE. However, CCE may be relatively resistant to effective treatment with IV tPA compared to other types of emboli.⁹ Mechanical thrombectomy is regarded as an effective and safe treatment modality for AIS due to large vessel occlusions. Higher recanalization rates and better clinical outcomes have been achieved with the use of newly developed devices and techniques. However, AIS caused by CCE continues to be challenging to treat.^4,10

Although CCE may often be misdiagnosed or ignored, these emboli can be easily diagnosed with a non-contrast brain CT or CT angiography. On non-contrast CT, the emboli will have an intravascular hyperattenuation >90 HU, usually in the range of 140–160 HU, with an occlusion of the corresponding artery demonstrated on angiography.^5,6 Previous studies have demonstrated that thrombolytic therapy is less effective for AIS caused by CCE; instead endovascular treatment is the therapeutic modality of choice.^5,11 Mechanical thrombectomy has a lower rate of recanalization in AIS caused by CCE compared to that achieved for other types of emboli.^4–6 Dobrocky et al. reported that successful recanalization was achieved in only 12.5% of cases of AIS caused by CCE in which thrombectomy was attempted with a stent retriever.⁴ In another study by Koh et al., MAT with a Penumbra reperfusion catheter failed to remove CCE in all five patients studied.¹⁰

The ERIC is formed by several interlinked cage-like nitinol spheres fixed on a pusher wire. They are designed to retract the clot coaxially and to prevent the captured clot from shearing off during retraction, especially at the guiding catheter tip. On cross-sectional view, the sphere looks like a flower with five petals. These geometrical characters result in limited contact points with the vessel wall which can potentially reduce vascular damage. Although it was an initial pilot study, Kahles et al. reported that retrieving thrombi with the ERIC device was technically feasible, effective and safe in patients with anterior circulation AIS.¹²

In the present case, we used an ERIC device in a patient with an AIS caused by CCE after failing to achieve recanalization with MAT. Successful recanalization was achieved in the first pass with the ERIC device. There are a number of potential reasons that the ERIC device has a higher success rate than other mechanical thrombectomy modalities in patients with AIS due to CCE. First, CCE have a harder consistency and tend to be densely packed within the vessel making it difficult to place the catheter tip within the calcified emboli to maintain the vacuum needed for manual aspiration. Second, the hard consistency of the emboli impedes passage of the microcatheter for stent delivery into the distal portion of the CCE. The ERIC device is used with a 0.017-in microcatheter, whereas other typical stent retrievers require the use of a microcatheter with a minimum size of 0.021 in. Third, the design of the ERIC device is different from that of other types of stent retrievers. Stent retriever thrombectomy devices work by compressing and entrapping the thrombus material within the stent struts before withdrawal.⁴ CCE have a higher resistance of deformation, which may interfere with the action of the stent retriever. The ERIC device is formed by 3–5 interlinked cage-like spheres with relatively large cell sizes. These geometric features allow CCE to be easily captured within the sphere of the ERIC device during withdrawal. This mechanism is similar to that occurring with removal of a urethral stone using an endoscopic basket.

CCE are a rare and challenging cause of large vessel occlusions in AIS. With its unique geometrical design, the ERIC device may serve as a useful neurointerventional modality for treating AIS caused by CCE.

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.