Background and purpose The pCONus is a new stent featuring a distal end that opens like a blossoming flower with four petals. The device is implanted in the aneurysm sac at the level of the neck. We report our initial experience in a series of patients treated with this device.
Methods This retrospective study was approved by the authors’ ethics committees. 18 patients with 19 unruptured wide neck bifurcation intracranial aneurysms (IA) were treated by pCONus placement and coiling. Technical issues, immediate post treatment angiographic findings, and clinical and imaging follow-up were assessed.
Results Embolization was successful in all patients. There were 11 women and 7 men with a mean age of 60 years. Median aneurysm size was 9 mm (range 5.5–25 mm). The device was precisely placed and detached in all cases, allowing for subsequent coiling. Two patients experienced a symptomatic complication, one of which, a thromboembolism, was related to the use of the pCONus. This patient had a slight hand paresis. 16 patients had a normal neurological examination at discharge. Immediate anatomical results were 13 complete occlusions, 2 neck remnants, and 4 incomplete occlusions. Imaging follow-up was obtained in 12 patients (mean 9.5 months, range 2–24 months) and showed 9 stable occlusions and 3 recanalizations, of which 2 were retreated.
Conclusions In this initial series of patients, endovascular treatment of wide neck bifurcation IAs with the pCONus was feasible, with acceptable clinical and anatomical outcomes. Further studies are needed to evaluate the indications, safety, and efficacy of this new device.
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Endovascular treatment (EVT) is now the firstline treatment for both ruptured and unruptured intracranial aneurysms (IAs).1–4 With the development of new endovascular approaches, including balloon assisted coiling, stent assisted coiling, flow diversion, and flow disruption, most IAs are now amenable to EVT. However, wide neck IAs located on a bifurcation remain technically more challenging to treat because both bifurcation branches must be protected. Recently, the first stent designed for use in wide neck bifurcation IAs (pCONus; Phenox, Bochum, Germany) was released. To the best of our knowledge, only one series has been reported on the use of this new device.5 ,6
The aim of our study was to report our preliminary experience following EVT of wide neck bifurcation IAs using the pCONus in 18 patients with 19 IAs.
Patients and methods
This retrospective study was approved by our local ethics committees. Between July 2013 and January 2015, EVT with the pCONus was performed in 18 patients with 19 aneurysms in 2 hospitals. There were 11 women and 7 men with a mean age of 60 years (range 42–78 years). All patients presented with an unruptured aneurysm located on a bifurcation: 7 on the anterior communicating artery (AcomA), seven on a middle cerebral artery bifurcation (MCA), 4 on the basilar tip, and 1 on the internal carotid artery (ICA) bifurcation. Among them, six aneurysms were previously treated and showed recanalization (after EVT, n=5) or regrowth (after surgical clipping, n=1). The clinical presentations are detailed in table 1. Because of the device characteristics (see figure 1), only wide neck aneurysms with a neck ≥4 mm were treated. The use of the pCONus was preferred to Y, X, or crossing stenting to avoid placement of two stents within the bifurcation.
All patients underwent conventional angiography of both ICAs, vertebral arteries, and three-dimensional angiography. Aneurysm characteristics are summarized in table 1. Median aneurysm dome diameter was 9 mm (range 5.5–25 mm). All aneurysms had a wide neck (neck/dome ratio >0.7) with a median size of 6 mm (range 4.5–10 mm).
The pCONus (figure 1) is a stent-like laser cut vessel implant which features a distal end that opens like a blossoming flower with four petals that rest on the inside of the aneurysm along the neck. The distal inner diameter of the pCONus is also crossed by six polyamide fibers, creating a mechanical barrier between the aneurysm and the parent artery. The proximal end of the device and the four distal loops carry segmental radiopaque markers made of platinum–iridium wire. They allow visual control in order to correctly position the device. However, it is important to note that the distal part of the petals remains invisible, and hence physicians should be aware that this part of the device may be in contact with the aneurysmal wall. The shaft of the pCONus is deployed in the parent artery to anchor the device securely in place. The device can be deployed completely and recovered completely, and it is detached via an electrolytic detachment process. Then, a coiling microcatheter must be navigated inside the stent and through a nylon net at the base of the petals to reach the aneurysmal sac. The distal diameters of the expanded petals are available in 5, 6, 8, 10, 12, and 15 mm. The pCONus shaft has a 4 mm diameter and is 20 or 25 mm long. The device is compatible with standard microcatheters with an inner diameter of 0.021 or 0.027 inches.
In all patients, EVT was performed under general anesthesia and systemic heparinization. The adequacy of systemic anticoagulation was monitored by frequent measurements of the activated clotting time (ACT). A baseline ACT was obtained prior to the bolus infusion of heparin (30–50 IU/kg body weight), and hourly thereafter. The bolus infusion of heparin was followed by a continuous infusion (1000–1500 IU/h), with the purpose of doubling the baseline ACT. At the end of the procedure, systemic heparinization was maintained for 24 h.
All procedures were performed by the senior interventional neuroradiologist (BL). The first step was pCONus placement at the base of the aneurysm. In all cases, a Prowler Select Plus microcatheter was used for stent delivery (Codman, Miami Lakes, Florida, USA). The distal tip of the Prowler Select Plus was shaped according to the angle between the parent artery and the aneurysmal sac. Duration of pCONus detachment was recorded. Then, selective coiling was performed with a Headway 17 microcatheter (MicroVention, Aliso Vieja, California, USA). Several three-dimensional coils (Microplex (MicroVention) or Barricade (Blockade Medical, Irvine, California, USA)) were placed to create a cage. Soft coils were then delivered to achieve aneurysm occlusion (HyperSoft coils; MicroVention). Only bare coils were used, and very small coils (1.5 mm in diameter) were not used to avoid the risk of protrusion within the parent vessel.
In all patients, a loading dose of 300 mg of clopidogrel and 320 mg of aspirin were administered 1 day before and on the day of EVT. Clopidogrel was maintained for 3 months whereas aspirin was administered for 6 months. After EVT, patients were transferred to the intensive care unit, and fluid balance, neurological status, and blood pressure were carefully monitored.
Angiographic results were classified according to the Raymond scale:7 complete occlusion (no contrast filling the aneurysmal sac), neck remnant (residual contrast filling the aneurysmal neck), and incomplete occlusion (residual contrast filling the aneurysmal body). The clinical course, including worsening of symptoms and death, were recorded. Clinical outcome was graded according to the modified Rankin Scale (mRS).8
In case of EVT of an unruptured IA, our imaging protocol includes conventional angiography at 6 and 12 months and MR angiography at 12, 36, and 60 months. Follow-up conventional and MR angiograms were compared with immediate post-embolization angiograms, and were then assigned to one of three categories: (1) further thrombosis, when the amount of contrast agent filling the aneurysm decreased; (2) unchanged, when a similar degree of aneurysm occlusion in multiple projections was found; and (3) recanalization, when an increase of the amount of contrast filling in the aneurysm was observed. Conventional and MR angiograms were reviewed for all patients by four senior neuroradiologists (BL, RM, FA, OFE) and consensus was reached.
Case No 1
Patient No 6 presented with multiple incidental IAs. Conventional angiography (figure 2A) showed a wide neck AcomA aneurysm. The aneurysm had a 5.5 mm diameter and a 6 mm neck. EVT was performed by pCONus placement (device with a distal diameter of 5 mm and a shaft of 25 mm) at the aneurysm base (figure 2B) and coiling, and complete aneurysm occlusion was achieved (figure 2C). The patient was discharged home 48 h later with a normal neurological examination (mRS score of 0).
Case No 2
Patient No 12 presented with multiple incidental IAs. Conventional angiography (figure 3A) showed a wide neck basilar tip aneurysm. Both the aneurysmal sac and the neck had a 9 mm diameter. EVT was performed by pCONus placement (device with a distal diameter of 8 mm and a shaft of 25 mm) and coiling, and complete aneurysm occlusion was achieved (figure 3B). The patient was discharged home 48 h later with a normal neurological examination (mRS score of 0). Angiographic control at 12 months showed recanalization of the base of the sac (figure 3C) and complementary coiling was performed, achieving a satisfactory occlusion (figure 3D).
EVT technique and feasibility
In all patients, EVT was successfully performed. The pCONus was delivered and detached in all cases. We found that the distal tip shaping of the pCONus delivery catheter was helpful to correctly position the device at the aneurysm neck. However, in one case, the stent was judged too small and was retrieved and replaced without significant friction. Radiopaque markers were also helpful to correctly position the device (figure 2B). Electrolytic detachment was reliable, and mean detachment duration was 122 s (110–142 s).
In the first three patients, we did not detach the pCONus before coils packing was judged to be stable. For the next patients, we immediately detached the device once we were satisfied with its position at the aneurysm base. In these cases, the device appeared very stable and no dislodgement was observed during placement of the coiling microcatheter and during coils delivery. However, we experienced two coils stretching that seemed ‘trapped’ within the aneurysm and the pCONus distal end. In both cases, the coils were Hypersoft coils (MicroVention) with a 2 mm diameter (length 4 and 6 cm). The coiling catheter was removed but these coils remained ‘trapped’ within the aneurysm and the pCONus. For this reason, we decided to recapture them. We used a Rebar catheter to position a Solitaire stent (Covidien, Irvine, California, USA) close to the stretched coil in the parent artery. We recaptured it in both cases by gently pulling back the Solitaire while aspirating via the guiding or access catheter (same procedure as a thrombectomy). These major procedural complications had no clinical consequences for the patients. No other technical complications occurred during EVT.
Clinical and anatomical outcome
Two patients presented with a clinical complication despite an uneventful procedure. Patient No 3 had an evolving and irregular wide neck AcomA aneurysm that was only seen when the left ICA was catheterized because both A2 segments of the anterior cerebral arteries were arising from the left A1 segment (he had no right A1 segment). This patient also had 50–60% stenosis of the left cervical ICA. Therefore, EVT was performed with a long introducer placed in the left common carotid artery and a 0.53 Neuron guiding catheter (Penumbra, California, USA) positioned in the left petrous ICA. The procedure was performed without any technical complications and resulted in complete aneurysm occlusion with normal angiographic controls during the whole procedure. The patient woke up with a severe hemiparesis and aphasia. MRI was performed, and diffusion weighted imaging showed diffuse cortical and gyriform hyperintensities in both anterior cerebral arteries and the left MCA territories. We concluded that the patient had global hypoperfusion during EVT. He has improved since EVT but has retained significant paresis and dysphasia (mRS score of 3).
Patient No 6, who was treated for three incidental IAs, experienced a thromboembolic complication, as demonstrated by diffusion weighted imaging on a control MRI, during EVT of a 20 mm MCA aneurysm. This patient retained a very slight paresis of the right hand (mRS score of 1). In the remaining 16 patients, neurological examination was unchanged.
Immediate anatomical results were 13 complete occlusions, 2 neck remnants, and 4 incomplete occlusions. Imaging follow-up was obtained in 12 patients (mean=9.5 months, range 2–24 months) and showed 9 stable occlusions and 3 recanalizations (patient Nos 1, 12, and 14). The first patient, with a slight recanalization at 24 months, presented with a ruptured giant MCA aneurysm that had already been coiled twice in another hospital before being sent to our department for a third treatment with the pCONus device. The second patient had multiple IAs, including a very wide neck basilar tip aneurysm with a 9 mm diameter (figure 3). Finally, the third patient, with multiple IAs, was treated for a recanalization of a ruptured and very wide neck basilar tip aneurysm with a 13 mm diameter. Two of these three patients have been retreated. No stenosis was seen within the stent at follow-up.
EVT of wide neck IAs
Several techniques and devices have been developed over the years to enlarge the indications for EVT. However, wide neck IAs located on a bifurcation remain technically challenging to treat by the endovascular approach because both bifurcation branches must be preserved.
The remodeling technique may be used but it has several limitations9: (1) it may fail to retain coils if the neck is too wide, (2) it may be associated with higher thromboembolic complications, and (3) it does not improve the stability of EVT.
The use of conventional stents is limited by the fact that both branches of the bifurcation must be protected. To circumvent this limitation, different stent assisted techniques have been reported including Y or X stenting, linear stenting, and the waffle cone technique.10–13 These techniques require the use of two stents in small vessels, except for the waffle cone technique. Nevertheless, the waffle cone technique is associated with a high recanalization rate.
Recently, the use of intrasaccular flow disruptors has been reported by several authors. They have shown that the WEB device is a new therapeutic option for the treatment of bifurcation wide neck IAs.14 ,15 However, a recent series has highlighted the possibility of major recurrences following EVT with the WEB.15
The first device designed to assist coiling of wide neck bifurcation IAs (the pCONus) has been released and evaluated in a series. Aguilar-Pérez et al5 have shown promising results in 28 patients with 28 wide neck IAs located on a bifurcation. A second device, the PulseRider (Pulsar Vascular, San Jose, California, USA), also designed for EVT of wide neck bifurcation IAs, is now available but no studies have yet been published on its use.
EVT with the pCONus
In our study, EVT was successfully performed in all patients. A significant technical complication occurred in two patients in whom a coil was ‘trapped’ within the aneurysm and distal end of the pCONus. Fortunately, we were able to remove both with the use of a Solitaire stent. Concerning the safety of device delivery, the petals do not have makers on their distal part and therefore physicians must be aware that the distal part of the petals may be in contact with the aneurysmal wall. According to the company, this relative limitation will disappear with the release of a new pCONus generation with distal radiopaque markers on each petal.
The overall good performance of the device confirms the data reported by Aguilar-Pérez et al5 who did not encounter any technical complications.
Clinical and anatomical outcomes
Considering the highly selected population of complex IAs, our clinical results were good, with only one patient (patient No 6) developing a complication related to the use of the pCONus device. Moreover, this patient retained only a slight hand paresis (mRS score of 1). Another patient had a significant complication (patient No 3, mRS score of 3) that was not related to the use of the pCONus. These findings are similar to those reported by Aguilar-Pérez et al5 who did not encounter any clinical complications.
Concerning the anatomical results, aneurysm coil recanalization is an important issue in endovascular therapy, with approximately 20% of coiled aneurysms recanalized and 10% retreated.16 As previously shown, wide neck IAs are prone to recanalization.16 In the present series, three recanalizations were observed (recanalization rate 25%) compared with Aguilar-Pérez et al5 who retreated 3 of 28 patients (11%). This difference may be explained by the fact that our median aneurysm size was larger.
Our study had several limitations: the series had a limited number of patients, and mid-term follow-up was not available for all patients. However, as this is a new EVT, it is important to have a rapid and accurate preliminary evaluation of this new therapeutic option.
Our preliminary study showed that EVT with the pCONus was an effective therapeutic option for the management of patients with wide neck bifurcation IAs. Clinical and anatomical outcomes were satisfactory but need to be confirmed in larger multicenter studies with long term follow-up.
Contributors BL and OFE: project development, data analysis, and manuscript writing. RM and FA: data collection and analysis. BM and LC: review of the manuscript.
Competing interests BL is a proctor for Phenox.
Ethics approval This study was approved by the local ethics committees.
Provenance and peer review Not commissioned; externally peer reviewed.