Published online before print January 26, 2012, doi: 10.3174/ajnr.A3007
AJNR 2012 33: E38

F. Xu^a and D. Song^a
aDepartment of Neurosurgery
Huashan Hospital
Fudan University
Shanghai, China

We read the article of Kim et al entitled “Stenting from the Vertebral Artery to the Posterior Inferior Cerebellar Artery” with special interest.¹ In their series, 2 patients had vertebral artery (VA) dissecting aneurysms involving the posterior inferior cerebellar artery (PICA) origin. The authors used VA-to-PICA stent placement with occlusion of the VA by coil embolization. They provided a new treatment option for VA dissecting aneurysms involving the origin of PICA. In this letter, we will discuss alternative treatment options for these complex aneurysms.

In recent years, various endovascular strategies have been used to treat VA dissecting aneurysms, including internal coil trapping, proximal parent vessel occlusion, stent-assisted coiling, or stent-only therapy.² Internal coil trapping of the dissected segment has been considered one of the most reliable treatments, especially for ruptured VA dissecting aneurysms. However, this procedure is not suitable for patients with the dissecting segment involving the PICA. Although internal coil trapping including the PICA origin may also be considered, previous studies have demonstrated lateral medullary and cerebellar infarction due to PICA occlusion.³ Therefore, it is difficult to predict the consequences of a PICA occlusion. Proximal occlusion of the parent artery is an alternate strategy but does not protect from rebleeding because of retrograde flow to the dissected segment.

Recently, reconstructive endovascular treatment, including stent or stent with coil, has been applied to VA dissecting aneurysms involving the PICA. In theory, a stent might effectively tack down the torn vessel, resulting in aneurysm occlusion and preservation of the parent artery. However, there are still some limitations in treatment for ruptured VA dissecting aneurysms involving the PICA. First, although double stents or multiple overlapping stents may be more effective for obliteration of a dissecting aneurysm sac than a single stent, a relatively high rate of complete obliteration has not been achieved in the literature. Because it takes a long time for the aneurysm to be completely obliterated, stent-only therapy may not completely prevent the ruptured dissecting aneurysm from rebleeding. Second, conventional stent-assisted coil embolization is usually limited in the treatment of these aneurysms. The coil loop may protrude into the parent artery lumen or occlude the PICA, resulting in ischemic complications.

Therefore, if the contralateral VA is equal or greater than ipsilateral, we might prefer trapping with revascularization of the PICA by endovascular procedures as far as possible. VA-to-PICA stent placement is a valuable treatment option to preserve the patency of the PICA.^1,4 In our experiences with 3 patients, we placed an Enterprise self-expanding stent (Cordis, Miami Lakes, Florida) from the distal or proximal VA to the PICA to save the patency of the PICA and occluded the aneurysm by coiling. However, a stent sometimes cannot be inserted into the PICA because of the small size of the PICA and/or acute angulation to the VA. Therefore, we use intra-/extra-aneurysmal Neuroform stent (Boston Scientific, Natick, Massachusetts) placement to protect the PICA for selected cases.⁵ Because of its open-cell design, the distal aspect of the stent within the aneurysm fundus acts to capture and restrain the initial coils, holding them within the aneurysm and allowing neck reconstruction.

References

1. Kim MJ, Chung J, Kim SL, et al. Stenting from the vertebral artery to the posterior inferior cerebellar artery. AJNR Am J Neuroradiol 2012; 33: 348–52 Abstract/FREE Full Text
2. Jin SC, Kwon DH, Choi CG, et al. Endovascular strategies for vertebrobasilar dissecting aneurysms. AJNR Am J Neuroradiol 2009; 30:1518–23 Abstract/FREE Full Text
3. Peluso JP, van Rooij WS, Sluzewski M, et al. Posterior inferior cerebellar artery aneurysms: incidence, clinical presentation, and outcome of endovascular treatment. AJNR Am J Neuroradiol 2008; 29: 86–90 Abstract/FREE Full Text
4. Chung J, Kim BS, Lee D, et al. Vertebral artery occlusion with vertebral artery-to-posterior inferior cerebellar artery stenting for preservation of the PICA in treating ruptured vertebral artery dissection. Acta Neurochir (Wien)2010; 152: 1489–92 CrossRef » Medline
5. Xu F, Qin X, Tian Y, et al. Endovascular treatment of complex intracranial aneurysms using intra/extra-aneurysmal stent. Acta Neurochir (Wien) 2011; 153:923–30 CrossRefMedline

Reply

Published online before print January 26, 2012, doi: 10.3174/ajnr.A3024
AJNR 2012 33: E39

M.J. Kim^a and Y.S. Shin^a
aDepartment of Neurosurgery
Seoul St. Mary’s Hospital
Catholic University of Korea
Seoul, Republic of Korea

We thank Dr Xu and colleagues for their response to our article entitled “Stent Placement from the Vertebral Artery to the Posterior Inferior Cerebellar Artery” and would hereby like to respond to some of their worthwhile discussion points.

In our country, available self-expandable intracranial stents are the Enterprise (Codman Neurovascular, Miami Lakes, Florida), Neuroform (Stryker Neurovascular, Natick, Massachusetts), Solitaire (ev3, Irvine, California), and Wingspan (Boston Scientific, Fremont, California). Stent-assisted coil embolization for preservation of the parent artery with intracranial aneurysms is becoming increasingly widespread and relies on mainly 2 types of self-expandable intracranial stents: the open-cell-type Neuroform and the closed-cell-type Enterprise.¹

The Neuroform stent was the first self-expandable intracranial stent.^2,3 However, the first-generation Neuroform stent had drawbacks of difficulty and instability with stent delivery. The second-generation Neuroform2 stent also had potential sources of complications due to distal wire injury, though it overcame the previous drawbacks by using a 3F microdelivery catheter and a 2F stabilizer catheter. Recently, the advanced Neuroform EZ 3 has been introduced, but it needs a microcatheter with a 0.027-inch inner diameter, larger than that needed by the Enterprise stent with a 0.021-inch inner diameter.

The intra-/extra-aneurysmal Neuroform stent placement to protect the posterior inferior cerebellar artery (PICA) for selected cases can also be considered another option as Dr Xu suggested. Because of its open-cell design, the distal aspect of the stent within the aneurysm fundus acts to capture and restrain the initial coils, holding them within the aneurysm and allowing neck reconstruction.

However, the Enterprise stent is more maneuverable than the Neuroform stent in our experience. Some authors reported that kinking and flattening of the Enterprise body can occur in curved vessels due to the closed-cell design, and the dislodgment might influence insufficient coil packing and obliteration of parent artery.^4⇓–6 However, in our study, the ability of the Enterprise stent to capture coils in aneurysms was excellent and flow of the parent artery was patent without stenosis or occlusion. The Enterprise stent has higher radial force and bending stiffness than the Neuroform stent.⁵ The characteristics of the Enterprise stent may be paradoxic effectiveness for better flow of the PICA.⁷ Indeed, the caliber of the PICA increased and the angle of the vertebral artery–PICA junction became larger after the procedure in most of our cases.

The above 2 stents may be available as supporting materials for smaller vessels such as the PICA. For the clinical practitioner, the more experienced or favorable “weapon” may be the most effective and safe for the goal of treatment.