Stent Reconstruction of Carotid Tonsillar Loop Dissection Using Telescoping Peripheral Stents

Internal carotid artery (ICA) dissection associated with tandem intracranial occlusion may be directly addressed through endovascular thrombectomy and carotid stent reconstruction [1, 2]. Anatomical tortuosity of the cervical ICA presents a technical challenge for conventional carotid stents, and there is limited experience with the use of intracranial or peripheral stents in this setting [3]. To the best of our knowledge, stenting around a true 360° tonsillar loop of the dissected ICA has not been previously reported.

We retrospectively reviewed 2 patients with tandem intracranial occlusions and ICA loop dissections treated with intracranial manual aspiration thrombectomy (MAT) and extracranial stent reconstruction with Zilver stents (Cook Medical, Bloomington, IN, USA).

Zilver self-expanding peripheral stents have an open-cell design with a pore diameter of 1.23 mm to limit plaque prolapse. They are compatible with a 0.018” guidewire and require a 5-F (0.066” inner diameter) or larger intermediate catheter for delivery. The delivery platform is 125 cm in length and utilizes an over-the-wire design, necessitating an exchange-length 0.018” guidewire.

We reviewed patient demographics, clinical presentations, endovascular treatments, and clinical outcomes. This study was exempt from our institutional review board, and patient consent was not sought because personal health information was de-identified.

A 41-year-old male developed acute-onset headache, dysarthria, and right hemiparesis that transiently resolved during transfer to our hospital, where his admission National Institutes of Health Stroke Scale (NIHSS) score was 2. Tissue plasminogen activator was not given due to his rapidly improving symptoms. Computed tomography (CT) angiography showed occlusion of the proximal left ICA with patent intracranial vessels. Despite aggressive medical management with aspirin and an intravenous heparin drip, the patient’s NIHSS acutely worsened to 16 the following day. Urgent arteriography was performed demonstrating left cervical ICA dissection and left middle cerebral artery occlusion (Fig. 1). A 6-F long sheath was advanced into the proximal ICA, and a triaxial system, including a microwire, microcatheter, and intermediate catheter (Table 1), was cautiously advanced through the dissection, which was noted to be associated with a 360° loop. A left M2 MAT was performed. Given that the patient had clinically failed medical therapy with a significant embolic event, the decision was made to stent across the dissection, and the patient was subsequently systemically heparinized (activated clotting time of 250). An 300-cm 0.018” microwire (Table 1) was advanced into the petrous ICA to maintain access distal to the dissection, the stroke catheter system was exchanged for a shorter intermediate catheter, and 3 telescoping Zilver stents were deployed around the dissected cervical ICA loop from distal to proximal, resulting in brisk anterograde flow through the construct at the conclusion of the procedure (Fig. 2).

A 56-year-old female presented to our hospital after developing acute, recurrent neck pain, dysarthria, and left hemiparesis with an NIHSS score of 14. Catheter-based arteriography revealed a right-sided intracranial tandem occlusion associated with a tonsillar loop dissection. A 6-F long sheath was advanced into the proximal ICA, a triaxial system was advanced through the dissection, and a right M1 MAT was performed. She was systemically heparinized (activated clotting time of 250), eptifibatide, aspirin, and clopidogrel were given, and 2 telescoping Zilver stents were placed around the dissected cervical ICA loop from distal to proximal, resulting in brisk anterograde flow through the construct at the conclusion of the procedure.

Symptomatic ICA dissections associated with tandem intracranial thromboembolic lesions respond poorly to intravenous anticoagulation and thrombolytic therapies [4]. Emergent endovascular treatment, including carotid revascularization and intracranial thrombectomy, is an increasingly popular and promising management strategy [1, 5-8]. A variety of techniques have been described for carotid revascularization in this setting, including the use of dedicated carotid artery stents with or without balloon angioplasty [2, 9, 10], the use of self-expanding intracranial or peripheral stents [11-13], and the use of an overlapping or telescoping stenting technique [9]. Recently, Murias Quintana et al. [3] called attention to the importance of considering ectatic or tortuous ICA anatomy that could impact the choice of carotid revascularization technique.

Cervical ICA tortuosity is believed to result from anomalous embryological development of the third aortic arch and the dorsal aorta [14]. Weibel and Fields [15] first coined the term “coiling” to describe redundant, circular true looping of the ICA. It is unclear whether or not ICA coiling itself is associated with carotid dissection or stroke [16], but when dissection or stroke does occur, coiling presents a unique technical challenge for endovascular treatment. Navigating through the dissection to reach the intracranial lesion may be hazardous as exacerbation of the dissection and vessel perforation may occur. There is concern that the exaggerated tortuosity of carotid tonsillar loops could complicate successful deployment of conventional carotid stents and that these stents may not exert adequate radial force to maintain lumen patency under these unique anatomical constraints.

When treating an ICA dissection, it is important to scrutinize the carotid anatomy to immediately recognize any variant coiling or kinking that would prompt the operator to take added caution. For example, in the presented cases, the proximal ICA occlusion and lack of contrast opacification limited initial visualization of the tonsillar loop. It was only with cautious advancement of the 0.014” microwire and microcatheter into the occlusion that the anomalous looping anatomy was recognized. In this situation, even mild tactile resistance or visible microwire tip deformation must be avoided to ensure that the operator remains within the true vessel lumen.

In the setting of a circular, 360° ICA coil loop, robust endoluminal support is necessary to navigate through the dissection in a safe and controlled fashion. We pinned a 6-F 0.088” inner-diameter long sheath just proximal to the dissection and utilized a triaxial stroke system (Table 1) to achieve adequate thrombectomy support in both cases. However, advancement of the rigid, long sheath through the looping dissection should be avoided because this maneuver may exacerbate the dissection.

Once the thrombectomy is completed, maintaining access distal to the dissection is critical if stenting will be performed because it may not be possible to re-cross the dissection. We pinned a 300-cm 0.018” microwire distal to the looping dissection into the petrous ICA and then exchanged our thrombectomy catheters for a shorter, 115-cm intermediate catheter that would accommodate the 125-cm Zilver stent delivery system. If a 115-cm catheter is used, it can sometimes be useful to remove the rotating hemostatic valve and stopcock to overcome length restrictions during stent deployment.

Although typically not used in the ICA, Zilver self-expanding stents were felt to be advantageous in this setting because of their open-cell design that facilitates greater flexibility and wall apposition within tortuous vasculature and their diverse, appropriate sizing options (stent diameters range 5–10 mm, stent lengths range 20–80 mm).

Several technical considerations facilitate safe and effective telescoping of these stents. With the 0.018” microwire pinned distal to the dissection, the intermediate catheter and stent are advanced just distal to the dissection, and the first stent is deployed by retracting the intermediate catheter and unsheathing the stent. Once the first stent is deployed, the pinned, distal microwire is used to guide the intermediate catheter into the deployed stent, and a subsequent stent is deployed in a partially overlapping, or telescoping, configuration. We repeat this process until the stent construct covers the entire length of the lesion, extending from normal endothelium distally to normal tissue proximally.

Pre-stenting heparinization and antiplatelet pharmacotherapy were administered to prevent in-stent thrombosis, and post-stenting dual antiplatelet therapy was continued for the same reason. Post-stenting arteriography showed brisk anterograde flow, post-procedure CT angiography re-demonstrated stent patency, and initial clinical outcomes were encouraging.

Although technically challenging, stent remodeling across a circular, 360° tonsillar loop of the dissected ICA is feasible with the use of flexible, self-expanding stents and advanced catheter support systems. As ICA dissections with tandem intracranial lesions are increasingly managed with emergent endovascular treatment, this technique may prove useful when variant ICA anatomy is encountered.

The authors have no conflicts of interest to declare.

There were no funding sources.