Discussion

In the present series of 10 patients with aSAH secondary to ruptured BA treated with PED implant, nine had excellent outcomes (90-day mRS 0 or 1). One patient died as a consequence of the original massive SAH and subsequent severe vasospasm. Long-term follow-up by DSA demonstrated complete occlusion of the BA and remodeling of the artery without recurrence or recanalization of the aneurysm.

Ruptured BAs are relatively rare, comprising 0.9–6.5% of ICA aneurysms and <1% of all intracranial aneurysms.11 It is estimated that 2.2% of cases of SAH from ICA aneurysms are the result of ruptured BAs.7 These lesions tend to occur more frequently in women and are associated with younger age, hypertension, and ICA atherosclerosis or dissection.7 Because of their very small size, they are difficult to detect on initial CT angiograms or even on DSA.12 These lesions may increase in size in the few days or weeks following rupture. Therefore, if not detected on the first DSA, they are often detected on follow-up angiograms.

Because of the abrupt disruption of the architecture of the arterial layers, BAs are fragile and prone to spontaneous rebleeds. In addition, the histological features of the BA and often of a large-cross section of the artery harboring the lesion are at high risk of rupture during surgical and endovascular manipulation. Surgical management in the past included microsurgical clipping or deconstructive approaches to the ICA or vessel trapping with or without high-flow bypass with poor outcomes.6 Ogawa et al,7 in a series of patients treated with a clip-wrapping technique, reported slightly better outcomes compared with patients treated with direct microsurgical clipping of the aneurysm. This technique has become the preferred approach for microsurgical management even though there is persistent morbidity and the procedure is technically challenging. In fact, the rate of intraoperative rupture during clipping and wrapping of BAs is reported to be as high as 50%, probably contributing to poor outcomes.7 ,13

Similarly, conventional endovascular approaches including coil embolization, stent-assisted or balloon-assisted coil embolization, and vessel deconstruction with or without high-flow bypass have been associated with procedural morbidity and devastating clinical outcomes in some series,5 ,14 although others have reported favorable results with stent-assisted coiling and more recently layered-stent constructs with or without adjunctive coil use.15 ,16

Flow diversion represents a revolutionary approach to the treatment of cerebral aneurysms. Through the disruption of the pulsatile flow into the aneurysmal sac, flow diversion leads to stasis, thrombosis, and regression of the aneurysm itself.8 Histological studies following FD deployment revealed endothelialization of the device and reconstruction of the entire length of the parent vessel covered by the implant and across the aneurysmal neck. Flow diversion represents a paradigm shift, focusing on reconstructing the parent vessel rather than treatment of the aneurysmal sac. The first FD device approved by the FDA was the PED, which is a self-expanding FD made of a braided multi-alloy cylindrical mesh woven from platinum/8% tungsten and 35NLT (cobalt chromium nickel) alloy wires. The woven wires of the device provide nominally 30–35% metal coverage of the arterial wall surface area.

This represents a significant paradigm shift compared with the 6–8% metal surface area coverage currently present in devices used for stent-assisted coil embolization.17 Two clinical trials have been conducted in the USA: the Pipeline for the Intracranial Treatment of Aneurysms trial18 and the Pipeline for Uncoilable or Failed Aneurysms.19 The results of these trials led to the approval of PED by the FDA and the introduction of the device in clinical practice for the treatment of large, giant wide-necked, and complex unruptured proximal carotid aneurysms. Although, the FDA approved PED for the treatment of large unruptured saccular aneurysms of the ICA, subsequently the device has proven useful in treating smaller sidewall saccular aneurysms. However, all of these studies excluded patients with acute aSAH. Recently, several case series have demonstrated a possible role for FDs as a viable alternative to microsurgical approaches with acceptable rates of lesion occlusion and procedural morbidity/mortality in patients presenting with aSAH.9 ,20–26

Implanting a FD or a stent in acutely ruptured aneurysms has per se the risk of severe complications because of the need for dual antiplatelet therapy. A dual antiplatelet regimen is needed to avoid complications within the PED itself and distally such as in-stent thrombosis and possible thromboembolism. In addition, patients with aSAH may need surgical procedures such as extraventricular drain placement or replacement or delayed surgery for a ventriculoperitoneal shunt. In addition, because of the possible systemic complications of SAH, these patients may need gastrostomy, tracheostomy, decompressive craniectomy or other procedures. In this regard, there is no level 1A evidence for the use or the timing or of a particular antiplatelet regimen of a specific type nor for the initiation and duration of antiplatelet therapy.

In our series, the timing and type of the dual antiplatelet regimen was left to the best judgment of the operators at each institution. In particular, the dual antiplatelet regimen consisted of a 600 mg load of clopidogrel and 325 mg of aspirin 5 followed by daily doses of clopidogrel 75 mg and aspirin 325. At Baptist Hospital in Miami the treatment was started after placement of the EVD and continued for at least 6 months. At Gates Vascular Institute and SUNY SUNY University at Buffalo antiplatelet medication was started 12 h after insertion of the EVD with CT confirmation of no EVD-related hemorrhage.

Aspirin and clopidogrel were the most common agents used, but prasugrel and ticagrelor have also been used instead of clopidogrel secondary to a high rate of clopidogrel resistance. Confirmation of effective antiplatelet activity with VerifyNow was also obtained. Glycoprotein IIb/IIIa inhibitors were avoided. Dual antiplatelet coverage was maintained for at least for 3 months and in some cases, based on individual physician preference, for 6 months.

With regard to the use of PED in BAs overall, Yoon et al9 reported the largest series of ruptured BAs of the ICA treated with PED. The authors reported 12 ICA ruptured BAs in 11 patients treated at six institutions in the USA between May 2011 and March 2013. Nine of these patients (75%) received a single PED, one received two PEDs, one was treated with coils and one PED, and one was treated with coils and two PEDs. Of the 11 patients, three (27%) had major complications such as MCA territory infarct, vision loss, and death. The 10 patients who survived had good clinical outcomes (mRS score 0–2). On long-term follow-up angiography the aneurysm was completely obliterated in seven patients. In another case series by Çinar et al23 the authors reported a series of seven BAs all located in the supraclinoid ICA. In their series, flow diversion with PED was carried out in all but one patient who was treated by parent artery occlusion. Aspirin and clopidogrel were administered 6–8 h before treatment in all patients. No serious adverse events such as rebleeding or thromboembolic complications were reported. The clinical outcome was mRS ≤2 in five patients, one patient had mRS 3, and one had mRS 4. On long-term control angiography, all aneurysms were occluded without recanalization.

In our series, all patients presenting with SAH were reviewed and those with ruptured BAs were assessed retrospectively with respect to procedural technique and outcomes. All PED implants were performed successfully. All patients were treated with PED alone, without coils. There were no cases of parent artery or branch occlusion following PED implant and there were no serious periprocedural complications related to PED placement such as immediate or delayed hemorrhages or in-stent thrombosis. None of the patients in our series had thromboembolic complications. Clinical outcomes were excellent with 90-day mRS scores of 0 or 1 in nine patients; one patient died as a consequence of a large SAH (H&H grade 4). Long-term follow-up by DSA showed complete occlusion of all aneurysms with remodeling of the artery. There were no instances of recurrence, recanalization, or regrowth of any of the aneurysms.