Introduction

A vertebral artery (VA) dissection with a hemorrhagic presentation is associated with a high risk of rebleeding [1, 5, 12]. Therefore, therapeutic intervention should be performed as soon as possible to prevent any subsequent bleeding. The ideal method of treatment for patients with subarachnoid hemorrhage (SAH) from a VA dissection and/or a dissecting aneurysm is complete occlusion of the dissecting segment from the circulation by performing endovascular treatment (EVT) or sometimes by performing surgical trapping. However, if the lesion involves the origin of the posterior inferior cerebellar artery (PICA), then the treatment options are more complicated. The most commonly accepted treatment modality is complete isolation of the dissected segment by surgical or endovascular trapping, along with revascularization of the PICA by using an occipital artery (OA)-to-PICA bypass [3], PICA side-to-side anastomosis [12] or PICA transposition [7]. Instead of the surgical revascularization of the PICA, we report here on a patient who was treated by placing an Enterprise stent (Cordis Neurovascular, Miami Lakes, FL) from the proximal VA to the PICA in order to save the patency of the PICA, and we completely occluded the dissected segment by coiling.

Case report

A 47-year-old man was admitted with Hunt–Hess Grade II SAH. Diagnostic digital subtraction angiography (DSA) was performed under local anesthesia, and this revealed a right VA dissecting aneurysm that involved the origin of the PICA (Fig. 1). The left VA was patent. The diameter of the right VA was 3.11 mm, and the diameter of the PICA was 1.21 mm. To prevent early rebleeding, we decided to immediately occlude the VA dissection with EVT. A 6-F Envoy catheter (Cordis Neurovascular, Miami Lakes, FL) was introduced into the right VA (V2 segment). We placed a microcatheter (Prowler Select Plus, Cordis Neurovascular, Miami Lakes, FL) into the PICA for the stenting, and another microcatheter (Excelsior SL-10, Boston Scientific, Natick, MA) was placed into the dissected segment of the VA for the occlusion of the segment. A 4.5 × 37-mm Enterprise stent was then placed through the proximal VA to the PICA. The dissected segment of the VA was completely occluded by coil embolization (Fig. 2). Intravenous heparin (3,000 U) was given after the first coil was detached. The right VA was completely occluded, and the flow from the VA to the PICA was preserved. Just after the procedure, loading doses of aspirin (400 mg) and clopidogrel (600 mg) were given to the patient via a nasogastric tube, and the dual anti-platelets (aspirin 100 mg and clopidogrel 75 mg per day) were maintained. The diffusion MRI showed no infarction at the territory of the PICA. The 2-week follow-up angiography showed good patency of the PICA, and the patient was discharged without neurological deficits. The 1-year follow-up angiography showed that the dissected segment was completely occluded, and the diameter of the PICA had increased with a good patency as the VA–PICA angle became larger in the course of time (3-month and 1-year follow-up) (Fig. 2). The patient has displayed no neurological deficit on the 1-year clinical follow-up.

Fig. 1
figure 1

a The lateral image of the left VA angiography and b the 3-dimensional reconstruction image showed the VA dissection with the involvement of the origin of the PICA

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Fig. 2
figure 2

a An Enterprise stent was placed through the proximal VA to the PICA. The dissected segment was completely occluded by coil embolization. b The 3-month follow-up angiography showed that the dissected segment was completely occluded, and the diameter of the PICA was increased with good patency. c The 1-year follow-up angiography revealed that the VA–PICA angle became larger as the stent had been unfolded by its returning force to become straight, resulting to the diameter of the PICA more increased. d The 3-dimensional reconstruction image showed the PICA patency. The proximal and distal stent markers were seen in the VA and the PICA. e The illustration of the VA-to-PICA stenting with coil embolization

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Discussion

Spontaneous VA dissection is classified into three major clinical types: headache, nonhemorrhagic ischemic symptoms, and SAH [10]. In patients with arterial dissection with a steno-occlusive pattern, subintimal hematoma and intimal flap may cause luminal narrowing and flow restriction [2, 9]. Some dissections may heal spontaneously with reconstitution of the vessel lumen; others can cause ischemic symptoms or stroke as a result of stenosis or occlusion of the parent vessel, or by perforating or circumflex vessels such as the PICA. In the serial angiograms of these patients, the findings continued to change during the first few months after onset, resulting angiographic cure. Vessel wall repair is complete after the neointima covers the entire area of the arterial wall. Anti-platelet drugs or anti-coagulants are recommended to prevent thromboembolic events in these patients. Recently, EVT is also suggested as a treatment option for these lesions [6, 10]. However, acutely ruptured VA dissections are unstable and have a tendency to rebleed [1, 5, 12]. The rebleeding rate has been reported to be as high as 71.4% in a group of 42 untreated patients [5]. The mortality rate of these rebleedings was high, being 46.7% in this series. Therefore, therapeutic intervention should be performed as soon as possible to prevent any subsequent bleeding. The choice of treatment method for patients with VA dissection depends on the patency of the contralateral VA as well as the relationship between the dissection segment and the location of the PICA origin. If the dissection is located proximal or distal to the PICA without hypoplasia of the contralateral VA, then the lesion can be treated with total occlusion of the dissecting segment with coils (internal trapping) so that the PICA would be filled from the contralateral or ipsilateral VA, respectively, after embolization [3]. The ideal method of treatment for patients with VA dissections that involved the PICA origin is complete isolation of the dissected segment by trapping, with revascularization of the PICA by such procedures as an OA-to-PICA bypass [3], PICA side-to-side anastomosis [12] or PICA transposition [7]. However, these surgeries can be troublesome because they take a relatively long time and there can be some surgery-related complication, such as lower cranial nerve palsy. The alternative strategy of proximal occlusion limits the risk of manipulating a catheter and wire across a narrow or irregular segment, and this proximal occlusion may allow for better collateral circulation, especially when the lesions involve the origin of the PICA or the anterior spinal artery [8].

In this case, the rupture point of the dissection was distal to the PICA origin, and the dissected segment involved the PICA origin. We initially planned to trap the dissected segment with an OA–PICA bypass or without the bypass if we preserved the VA–PICA flow with good positioning of the clip. The latter would be performed by using a proximal clip that would have been placed obliquely just distal to the PICA origin so that the dissected segment would be completely occluded while the PICA would be patent. Instead of this surgical technique, we thought about EVT with using a stent, and we concluded that VA-to-PICA stenting might cover the proximal dissected segment with leaving the PICA flow patent. Then, the rupture point of the dissected segment distal to the PICA origin was to be occluded by coil embolization. We performed a VA-to-PICA stenting for saving the PICA’s patency in a patient with the VA dissection involving the PICA origin (Fig. 2e).

When endovascular occlusion of the intradural VA including the PICA origin is considered, we should anticipate the risk for lateral ischemia of the brainstem. The PICA gives rise to quite large caliber perforating vessels supplying the brainstem if it emerges in the intradural VA [4]. This is why we planned to save the PICA in this case. Other perforating vessels emerging from the VA could exist distally from the PICA origin and supply the brainstem. However, the perforating vessels from the PICA share the area with the branches coming from the basilar artery, the AICA, and the VA. Also, Mercier et al. [4] mentioned that there are highly frequent pial anastomoses at the surface of the brainstem. These facts allowed us to occlude the dissected segment of the VA completely.

Even though the Enterprise stent is recommended to be used in an intracranial artery with a diameter larger than 2 mm, the authors placed the Enterprise stent in the PICA with its diameter being about 1.21 mm (less than 2 mm). There are no reports in the literature detailing the feasibility, use, or safety of stents in small cerebral vessels less than 2 mm in diameter, and the longer-term effects of the presence of a stent are not yet known. However, there are some reports dealing with the safety of stents in small cerebral vessels from the case-series studies. Turk et al. [13] described eight patients who had safely and successfully undergone stent treatment in vessel diameters less than 2 mm with positive short- and intermediate-term results. They experienced that thrombus formation occurred within the stent in two cases, which dissolved after the intra-arterial administration of glycoprotein IIb/IIIa inhibitor. Although this finding suggests that there is an increased risk of thrombus formation despite adequate prophylaxis, it did not result in any untoward clinical or imaging outcomes. They concluded that the use of self-expanding stents in vessel diameters less than 2 mm could be performed safely and efficaciously. Also, Siddiqui et al. [11] performed eight cases of horizontal stent-assisted coil embolization with the Enterprise stent in vessels that had the mean caliber of 1.58 mm. They followed up all patients with DSA at 3–12 months following treatment. They concluded that the stents were successfully and accurately deployed in vessels of less than 2 mm in diameter with no occurrences of stent occlusion. They recommend that high-quality DSA should be used to follow such patients because the risk of in-stent stenosis might be higher when stenting small arteries. In our case, the short-term follow-up angiography revealed that the PICA flow was patent, and the diameter of the PICA had increased to 1.58 mm and 1.72 mm in the 3-month and the 1-year follow-up, respectively. The acute angle over which the stent was deployed would be expected to constrict the stent at the VA–PICA junction. However, as the stent had been unfolded by its returning force to become straight, the VA–PICA angle became larger in the course of time (3-month and 1-year follow-up) and made the PICA flow better. However, long-term follow-up should be done for assessing the patency of the PICA as well as confirming that the Enterprise would not migrate backward and the aneurysm would not re-rupture.

Conclusion

VA-to-PICA stenting with total occlusion of the VA by coil embolization might be a valuable treatment option to preserve the PICA’s patency when treating a patient with VA dissection that involves the origin of the PICA.