Bilateral vertebral artery dissecting aneurysms (VADAs) presenting with subarachnoid hemorrhage (SAH) are rare and their management is still challenging4,6). Successful results with staged bilateral VA occlusion for vertebro-basilar DA have been reported4,14,15), but in many cases bilateral VA occlusion cannot be tolerated if the patients do not pass the balloon test occlusion. In this situation, reconstructive treatment is required. Of these, stent assisted coiling (SAC) or the stent-within-a-stent (SWS) technique has been performed with relatively good results1,18). And recently, covered stent grafts for VADA has been reported with good outcomes3).

After occlusion of a unilateral VA either by surgically or endovascularly, contralateral VADA enlargement or even rupture has been reported in the literature4,5,14,16). Increased hemodynamic stress to contralateral VADA might precipitate the growth of preexisting VADA.

The authors report a rare case of bilateral VADAs presenting with SAH, which was treated with internal trapping of the ruptured dissecting segment and covered stent graft after SWS and subsequent multiple session of SAC of the contralateral unruptured VADA.

A 44-year-old woman was transferred to our hospital because of headache and sudden mental deterioration. She was stuporous, but had no motor weakness. She had no history of hypertension, diabetes mellitus, or head injury. A physical examination revealed severe neck stiffness.

Brain computed tomography (CT) scans showed a thick SAH on the basal, prepontine, both Sylvian, ambient, and cerebellopontine angle cisterns, predominantly on the right side and acute hydrocephalus due to intraventricular hemorrhage on all ventricles (Fig. 1A). CT angiograms demonstrated bilateral VADAs, which were larger on the right side (not shown). An external ventricular drainage catheter was inserted urgently before the endovascular procedure. Digital subtraction angiography (DSA) and 3-dimensional rotational angiograms demonstrated a 6×12 mm sized right VADA [the right posterior inferior cerebellar artery (PICA) was not visible], and a 5×7 mm sized left VADA, which was incorporated with the PICA origin (In-PICA type) (Fig. 1B, C). The right VADA was considered ruptured because the SAH predominated on the right side and the right VADA was larger than the contralateral VADA. Endovascular coil trapping of the ruptured right VADA was performed on the same day using 19 coils. Postoperative angiography showed complete obliteration of right VADA with sufficient flow to the basilar artery via left VA (Fig. 1D, E).

One month later, two overlapping stents (SWS) implantation (Enterprise 4.5×22 mm, and 4.5×28 mm, Cordis Neurovascular, Miami, FL, USA) was performed for the unruptured left VADA to prevent possible growth due to increased hemodynamic stress to the left VA caused by contralateral VA sacrifice. After double stent implantation for the left VADA, blood flow to aneurysmal sac was slightly reduced (Fig. 1F). Subsequently, the patient was alert with dull mentality. She was discharged to a rehabilitation hospital at 6 weeks after initial SAH.

Eight months follow-up angiograms demonstrated stable occlusion of the right VADA (Fig. 2A) and marked growth of the left VADA (Fig. 2B). At least two pseudosacs were identified, and these were separately treated with coil packing though the interstices of stent strut. Postoperative angiograms showed near complete obliteration of the left VADA and sparing of left PICA flow (Fig. 2C).

Angiography conducted at 5 months after the left VADA procedure demonstrated further growth of left VADA (Fig. 3A), which was re-treated with further coil packing into the growing pseudosacs and bailout stenting using a 4.5×28 mm Enterprise stent to maintain left VA flow (Fig. 3B). Postoperative angiograms showed near complete obliteration of the VADA, and sparing of left PICA flow (Fig. 3C, D). However, follow-up angiograms 4 months later showed regrowth of the left VADA (Fig. 4A). Further coil packing was considered ineffective in this patient, and more definitive treatment, such as, occipital artery-PICA bypass surgery followed by endovascular reconstruction of the VA using a covered stent was considered, but the PICA diameter was too small. Thus, we planned covered stent implantation for the dissection segment below the PICA origin, and coverage of the remaining part of the dissection segment with balloon expandable coronary stent to induce spontaneous occlusion of the pseudosac as a result of flow stagnation and diversion, sparing the PICA flow. Telescopic stenting with two covered stents (Jostent Graftmaster 3.5×12 mm, 3.5×9 mm, Abbott vascular, IL, USA) was successfully performed on left VA just below the PICA origin. Control angiography showed marked reduction of blood flow to the VADA, but retrograde flow was still visible near the PICA origin. A third stent (Driver stent 3.5×12 mm; Medtronic Vascular, Santa Rosa, CA, USA) was then implanted across the PICA origin, covering the distal part of the dissecting segment (Fig. 4B). Final angiography still demonstrated slow retrograde flow to the VADA even though flow velocity into the aneurysmal sac was markedly reduced (Fig. 4C, D). Follow up DSA at 2 months showed near complete occlusion of the left VADA (Fig. 4E, F). Follow-up angiography will be performed to confirm complete occlusion of the VADA in the near future.

Bilateral VADA presenting with SAH is extremely rare6,9-11), and no established treatment is exists for this type of VADA. Even though there has been a successful report with conservative treatment under strict sedation and blood pressure control during the acute stage10), this is not a reasonable option for a ruptured VADA because of the high risk of rebleeding during the acute stage. Bilateral VA occlusion combined with surgical vascular reconstruction may be the treatment of choice for this type of lesion16), but in many cases, vascular reconstruction of the posterior circulation is difficult or not possible. Another treatment option might be unilateral VA occlusion of a ruptured VADA followed by stent only therapy or SAC for a contralateral unruptured VADA. Successful reports with stent only therapy for VADA have been published8,12). Park et al.12) treated 29 vertebro-basilar DAs in 27 patients by stent only therapy. Complete or partial obliteration was achieved in 88.8%, and angiographic improvement was more common in patients with multiple overlapping stents. Stent-induced hemodynamic changes, such as decreases in inflow momentum, velocity, and wall shear stress, could help prevent aneurysm growth and rupture7,20).

To treat bilateral VADA presenting with SAH, it is important to determine which aneurysm has ruptured. The possible clues of side of rupture are SAH distribution and the shape and size of the DA4). If the SAH predominates in one side or one aneurysm is larger, or has a bleb, then there is a high likelihood of rupture of that side. In our case, the right VADA was considered ruptured because SAH predominates on the right side and the right VADA was larger. Furthermore, no important branch was visible on the right VADA, indicating that the right VADA could be trapped completely using coils.

After unilateral VA sacrifice, enlargement or even rupture of contralateral VADA has been reported5,16). Increased hemodynamic stress to the contralateral VA may induce aneurysm growth. In our case, to prevent aneurysm growth or rupture after unilateral trapping of the right VADA, two overlapping stents were implanted into the contralateral VADA. However, even though the immediate postoperative angiogram showed a slight decrease in aneurysm filling, the unruptured VADA enlarged over time, and subsequent, overlapping stenting using two Enterprise stents did not prevent aneurysm growth. The possible reasons why our result was disappointing are related to the degree of apposition of stent and DA and the metal covered area within the vessel wall. Park et al.12) used coronary stents to treat all DAs, except five. Coronary stents are balloon expandable stents, and thus there is a greater chance of good apposition of the DA wall and stent strut during ballooning. On the other hand, the Enterprise stent is a self expandable stent, and although radial force is enough to prevent stent movement after deployment, the pressure applied to the DA wall may not be sufficient to occlude the DA inlet or outlet. Coronary stent has a smaller cell size than Enterprise stent. Thus, the porosity of coronary stent is lower than that of Enterprise stent. The relatively higher porosity of Enterprise stent might have been responsible for aneurysm growth because of less flow diversion effect.

For the management of VADA not amenable to internal trapping, the SAC followed by the SWS technique have been reported1,18,19). Suh et al.18) treated 11 VADA patients successfully in this manner without any treatment-related complications. Follow-up angiography at 6 to 12 months on the surviving 10 patients showed complete DA obliteration in 9. They used 10 Neuroform stents, and 1 balloon expandable coronary stent, and during the procedure they used in-stent balloon assistance to ensure tight packing. However, in our case, marked regrowth of the left VADA was identified after double overlapping stenting. If additional overlapping stenting results in failure, coil packing into the DA might be impossible because triple or quadruple stenting will probably prevent microcatheter selection. Thus, we performed SAC twice before covered stents graft. Covered stent graft below the origin of the PICA can occlude inlet of the VADA and preserve left PICA flow. However, covered stents are very stiff and hard to navigate tortuous cerebral vessel. Thus, we used short length of two covered stents to navigate the VA easily.

Covered stent grafts for intracranial aneurysms were first described by Redekop and colleagues in 200113). Since their report, these stent grafts have infrequently been used for the management of carotid cavernous fistulas, internal carotid artery aneurysms, and VA aneurysms2,3). To our knowledge, only 11 patients with VADA have been treated with a covered stent graft successfully2,3,13). Theoretically, a covered stent graft can obliterate the dissecting aneurysm while maintaining the patency of the parent vessel, and it represents a good treatment option for VADA. However, some considerations should be borne in mind. First, covered stents should not be implanted for vessels with important perforators because they occlude any branch of the parent vessel along the length of the stent. For instance, a covered stent graft for In-PICA type of VADA can result in Wallenberg syndrome or even death due to PICA occlusion. He et al.3) treated 5 cases of VADA successfully with a covered stent graft. Of these, VADA was located at proximal to the PICA in 4. To avoid accidental PICA occlusion, they selected patients with dissection distant from important vessels, such as, the PICA, by at least 2 mm. In our case we also deployed the covered stents just proximal to the PICA origin to prevent accidental occlusion of the PICA. The second consideration is the navigability of the stent to the intracranial VA. Covered stents are relatively stiff compared with other stent systems. Thus, if the proximal VA is tortuous or the V3 segment angle is very acute, a covered stent graft may not be possible. To overcome the navigability issue a shorter length of stent can be used to improve navigability. The third consideration is the restenosis issue. In one study, after coronary stenting restenosis occurred in 25% of patients17). A covered stent, such as, the Jostent Graftmaster, is a stainless steel stent with the PTFE membrane placed between 2 layers of stent struts. It has been associated with an increased risk of delayed restenosis/occlusion of VA17). However, fortunately no restenosis or occlusion of parent artery after covered stent graft in VADA has been reported yet.

Recently, newly designed stents with low porosity, such as, the Pipeline stent have been introduced to create a flow-diversion effect and to induce spontaneous thrombosis in large/giant or fusiform aneurysm. The pipeline stent may help to overcome the limitation of highly porous stents for the management of this challenging aneurysm in the near future.

Bilateral VADA presenting with SAH is rare. In terms of its management, contralateral VADA enlargement due to the increased hemodynamic stress after ipsilateral VA flow sacrifice must be kept in mind. Covered stent graft for the involved VADA can be a valuable therapeutic option, especially in patients that require absolute preservation of VA flow. Early follow-up angiography is mandatory.