Introduction Intracranial vertebral dissecting pseudoaneurysms are a rare, but increasingly recognized, cause of subarachnoid hemorrhage and ischemic stroke. The risks of aneurysm re-rupture and associated morbidity are high. The use of flow diverter stents for the treatment of these aneurysms has not been well studied.
Objective To report our data and provide a summarized review of literature using flow diverter stents for the treatment of intracranial vertebral artery dissecting pseudoaneurysms.
Methods We performed a retrospective analysis of flow diverter stents used for the treatment of intracranial vertebral artery dissecting pseudoaneurysms. Clinical, imaging, procedural, and follow-up data were collected.
Results We identified eight vertebral dissecting pseudoaneurysms in seven patients (5 (71.4%) female; median age 47 years (IQR 46–52)) who had undergone treatment with flow diverter stents. In 4/7 patients (57.1%) the aneurysm had ruptured; however, only one was treated in the acute phase. Median size of the largest diameter of the aneurysm was 6.3 mm (IQR 4.2–8.8), and 7/8 aneurysms (87.5%) were treated with a single flow diverter device. Three aneurysms were concurrently coiled. Angiographic complete occlusion was seen in 6/8 (75%) aneurysms at a median follow-up of 14 months (IQR 7.7–20.2). Two patients had periprocedural strokes with transient neurologic deficits. All patients had a good clinical outcome (modified Rankin Scale score ≤2). There were no re-treatments or aneurysm ruptures during the follow-up period.
Conclusions Our experience suggests that flow diverter stent treatment of intracranial vertebral artery dissecting pseudoaneurysms is safe, and associated with good occlusion rates and favorable clinical outcomes.
- Flow Diverter
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Intracranial vertebral artery dissecting pseudoaneurysms are a rare but serious cerebrovascular problem, which can present with subarachnoid hemorrhage, ischemic events, or headaches. The risk of re-rupture of these aneurysms is high and treatment usually involves sacrifice of the parent vessel.1 With the advent of modern endovascular therapy, including stents and flow diverters, reconstructive interventions have been favored in many institutions for the treatment of intracranial vertebral artery dissecting pseudoaneurysms.2 Flow diverter stents can selectively divert flow away from the aneurysm, but keep the patent vessel and the side branches intact,3 making them a unique candidate for treating these difficult lesions. Our aims were to report our data on these challenging vascular anomalies, and to combine our experience with additional evidence from the literature to assess the safety and feasibility of flow diverter therapy for vertebral pseudoaneurysms.
After approval from the institutional review board, a retrospective chart review of all patients those had undergone flow diverter stent embolization for intracranial vertebral artery dissecting pseudoaneurysms at our institution was carried out. We collected patient clinical data, demographics, outcomes, and procedural details. Good clinical outcomes were graded as modified Rankin Scale score 0–2. For aneurysm occlusion, we dichotomized our data into complete occlusion versus incomplete occlusion. For the literature review, we performed a thorough search to identify cases of flow diverter stents used for the treatment of intracranial vertebral artery dissecting pseudoaneurysms. We searched Pubmed, Embase, Scopus, and Web of science with the following key words: ‘flow diverter stent’, ‘dissecting pseudoaneurysm’, ‘intracranial vertebral artery’, ‘Pipeline’, and ‘dissecting aneurysm’. The articles were reviewed to identify patients, and extract clinical, procedural, and follow-up data. Only English language manuscripts were selected. We excluded articles which contained no details of clinical history and imaging findings, or those in which the cases formed part of a larger study with no clear individual case details. We also excluded abstracts presented at meetings with no subsequent manuscripts.
Pretreatment with aspirin and clopidogrel was initiated 5–7 days before treatment for elective cases. A loading dose (600 mg clopidogrel and 650 mg aspirin) was administered a few hours before treatment for the one acutely ruptured emergent case when the procedure was performed within 24 hours of the ictus. Adequate platelet inhibition was verified via institutional platelet aggregometry testing as previously reported, and higher doses were administered if necessary.4 All cases were treated using a triaxial system of a proximal shuttle, an intermediate catheter, and a standard 0.027″ microcatheter. The Pipeline flow diverter stent (Medtronic, Minneapolis, Minnesota, USA) was used in all cases. Device size was chosen according to the parent vessel diameter, length of the affected segment, and aneurysm neck size. A decision to use multiple telescoping stents was based on individual case and provider preference. Patients were maintained on at least 6–12 months of dual antiplatelet therapy, followed by aspirin monotherapy indefinitely.
We identified seven patients with eight aneurysms that met the inclusion criteria (table 1). The median age of the patients at the time of treatment was 47 years (IQR 46–52) and five were female (71.4%). In 4/7 patients (57.1%), the aneurysm had ruptured; however, only one was treated in the acute phase. The other three patients had previously ruptured aneurysms, which underwent flow diverter embolization as a secondary treatment for residual filling of the aneurysm several months to years after the original rupture and initial endovascular treatment (primary coiling and stent-assisted coiling). Presenting symptoms for the patients with non-ruptured aneurysms were headaches and transient neurologic deficits. The right vertebral artery was most involved in 5/8 aneurysms (62.5%). In three cases each, the aneurysm was at the level of the posterior inferior cerebellar artery (PICA) and proximal to the PICA branch (figure 2), while in two cases it was distal to the PICA (figure 1). The median size of the largest diameter of the aneurysm was 6.3 mm (IQR 4.2–8.8). The majority of cases (7/8 aneurysms, 87.5%) were treated with a single flow diverter device; one aneurysm was treated with two overlapping flow diverter stents. Three aneurysms (37.5%) were concurrently coiled. In all cases, the distal end of the flow diverter stent was anchored in the distal V4 segment of the vertebral artery or the vertebrobasilar junction. The PICA origin was covered by the stent in 7/8 procedures (87.5%), with preserved patency of the PICA in all of these patients at time of the last follow-up. This included one of our patients with a mild PICA stroke, who had no obvious PICA thrombus or vessel compromise on imaging. The anterior spinal artery origin was covered by the stent in 4/8 procedures (50%) without any compromise in blood flow on the last follow-up imaging. Angiographic follow-up was available in 7/7 patients (100%) with complete occlusion in 6/8 (75%) aneurysms at a median follow-up of 14 months (IQR 7.7–20.2). Two patients had small periprocedural strokes with transient neurologic deficits. One was due to early stent thrombosis involving the non-dominant vertebral artery, resulting in a cerebellar stroke. The other patient (as mentioned earlier) had a PICA stroke with excellent recovery, and without evidence of PICA vessel compromise on imaging. All patients had excellent clinical outcome at the last available follow-up (with a median modified Rankin Scale score of 1). There were no re-treatments, recurrences, or aneurysm rupture during the follow-up period.
Review of literature
We identified only 11 published papers in the English literature, yielding 45 patients with a total of 47 intracranial dissecting vertebral artery aneurysms treated with flow diverter stents.3 ,5–14 Details of individual cases are given in table 2. Only two studies had more patients/cases than ours (nine each), but these reports lacked either follow-up clinical outcome data, or the exact description and location of the treated aneurysms. Median age at treatment was 48.5 years (IQR 42.7–56). In 19/47 (40.4%) the presenting symptom was acute subarachnoid hemorrhage due to the vertebral dissecting aneurysm, while in 4/47 (8.5%) the presenting symptom was an ischemic stroke/transient ischemic attack. In 6/47 (12.8%) a Tubridge flow diverter (Microport Scientific Corporation, Shanghai, China) was used, and the remainder had Pipeline flow diverter stents. At available follow-up (range 5 days to 45 months), only 8/44 (18.2%) aneurysms had residual filling. Periprocedural complications were seen in 3/36 patients (8.3%). Only two patients required re-treatment, one owing to foreshortening of the device, and the other for in-stent stenosis. No postprocedural ruptures were noted.
Our single-center data show that reconstructive endovascular surgery with flow diverter stents is feasible, safe, and effective for intracranial vertebral artery dissecting pseudoaneurysms.
Our cohort is one of the largest of its kind with concise follow-up data. In addition, for the first time, we provide a comprehensive review and summary of the available literature on this topic, and combine the data with our results. Our numbers are favorable and comparable to previously reported occlusion, re-treatment, and periprocedural complication rates.
Although flow diverter devices have not been approved by the Food and Drug Administration for posterior circulation application in the USA, they have been used more and more frequently since an increasing body of clinical and radiographic evidence has become available.4 ,15 The treatment of intracranial vertebral artery pseudoaneurysms is generally considered high risk owing to the presence of two major branches to the parent vessel: the PICA and the anterior spinal artery. Although prior reports showed preserved patency of side branches covered by flow diverters in many cases,16 the posterior circulation remains a challenging perforator-rich vascular region with often not fully predictable response to flow diversion. In general, most operators advocate the use of the smallest number of flow diverters to avoid possible complications related to the stent.4 We try to apply this concept in our clinical practice as shown by the average number of devices used in this study: only one patient had two flow diverters while all the others received a single device. Although two of our patients did have small periprocedural strokes, fortunately they caused only transient neurologic symptoms, and these patients made an excellent recovery with no residual neurologic deficit. In one patient, the stroke involved the PICA territory despite any flow compromise to the vessel from the flow diverter covering the PICA origin. In the other patient with a cerebellar stroke, in-stent thrombosis distal to the PICA origin was found in the non-dominant vertebral artery within 24 hours of the procedure despite adequate platelet inhibition. There was no obvious vessel or stent compromise at the time of treatment, but the overall small vessel caliber might have contributed to altered flow dynamics and an eventual thrombotic phenomenon.
In the past, parent artery occlusion or trapping of the aneurysms was the preferred treatment for this highly challenging and potentially devastating disease entity. However, as endovascular devices have developed, patent artery preservation has emerged as a plausible technique.2 In a meta-analysis comparing deconstructive with reconstructive surgery for vertebral dissecting aneurysms, endovascular reconstructive surgery was as effective as deconstructive surgery, and also had a lower periprocedural morbidity.2 Another meta-analysis study comparing stent-assisted coiling with trapping showed that long-term outcomes and morbidity were similar.1 Vessel remodeling and reconstruction with flow diverters also has a distinct advantage for dissecting pseudoaneurysms. Vessel dissection usually involves the proximal and distal segment of the parent vessel, not only the pseudoaneurysmal portion. Flow diverter stents may help to remodel the entire diseased vessel segment, treat the aneurysm, and close the false lumen.6 ,10
Limitations to our study include its retrospective nature and the number of patients. In addition, longer follow-up times would provide more precise information on recurrence and complete occlusion rates. Owing to the low incidence of the index disease, however, it is not likely that it will be feasible to conduct large randomized controlled studies for this rare vascular problem in the foreseeable future.
Our results, combined with a review of available evidence from the literature, suggest that flow diverter stent treatment of intracranial vertebral pseudoaneurysms is technically feasible, relatively safe, and associated with good occlusion rates and favorable clinical outcomes.
Contributors RC: design of the work, acquisition of data, interpretation of data, drafting of the manuscript. GT: study conception, interpretation of data, critical revision of manuscript. Remaining authors assisted in interpretation of data and critical revision of the manuscript.
Competing interests MB: Codman and Stryker consultant. Clinical Events Committee for the BARREL trial. MSH: Pulsar Inc, Clinical Events Committee. PR: Medtronic Neurovascular—Scientific Advisory Board; Genentech—consultant/honorarium; Nervive Medical—Scientific Advisory Board and stock holder; Perflow Medical—Scientific Advisory Board and stock holder; Stryker Neurovascular—Scientific Advisory Board. GT: Data Safety Monitoring Board for the COMPASS trial.
Ethics approval Institutional review board, Cleveland Clinic.
Provenance and peer review Not commissioned; externally peer reviewed.