Middle cerebral artery aneurysm endovascular treatment with Flow Diverter
When performed in a select treatment group, high rates of aneurysm occlusion and protection against re-rupture can be achieved 2).
Longer angiographic follow-ups are needed to assess the morphologic outcome; immediate subtotal occlusions do not seem to be related to rupture 3).
Findings suggest that complete occlusion after endovascular treatment with FDD can be delayed (>6 months). Ischemic complications may occur as early or delayed, particularly at clopidogrel interruption 4).
The Pipeline Embolization Device provides a safe and effective treatment alternative for wide-neck MCA aneurysms that give rise to a bifurcating or distal branch when other endovascular techniques are thought to be unfeasible or more risky 5).
For Caroff et al. compared with other available therapeutic options, the flow-diverter stent does not appear to be a suitable solution for the treatment of saccular MCA bifurcation aneurysms 7).
Unsatisfactory occlusion rate in bifurcation aneurysms likely results from residual filling of the aneurysms in cases in which the jailed side branch remains patent 8).
Systematic review and meta-analysis
A systematic search of PubMed, MEDLINE, and Embase was performed for studies published from 2008 to May 2017.
According to the Preferred Reporting Items for Systematic Reviews and MetaAnalyses, Cagnazzo et al. selected studies with >5 patients describing angiographic and clinical outcomes after flow-diversion treatment of MCA aneurysms.
Random-effects metaanalysis was used to pool the following outcomes: aneurysm occlusion rate, procedure-related complications, rupture rate of treated aneurysms, and occlusion of the jailed branches.
Twelve studies evaluating 244 MCA aneurysms were included in this meta-analysis. Complete/near-complete occlusion was obtained in 78.7% (95% CI, 67.8%-89.7%) of aneurysms. The rupture rate of treated aneurysms during follow-up was 0.4% per aneurysm-year. The rate of treatment-related complications was 20.7% (95% CI, 14%-27.5%), and approximately 10% of complications were permanent. The mortality rate was close to 2%. Nearly 10% (95% CI, 4.7%-15.5%) of jailed arteries were occluded during follow-up, whereas 26% (95% CI, 14.4%-37.6%) had slow flow. Rates of symptoms related to occlusion and slow flow were close to 5%.
Small and retrospective series could affect the strength of the reported results.
Given the not negligible rate of treatment-related complications, flow diversion for MCA aneurysms should be considered an alternative treatment when traditional treatment methods are not feasible. However, when performed in this select treatment group, high rates of aneurysm occlusion and protection against re-rupture can be achieved 9).
Consecutive patients treated from January 2010 to December 2014 by Iosif et al. by using endovascular flow-diverting stents for MCA bifurcation aneurysms were evaluated retrospectively with prospectively maintained data. All patients had been followed for at least 12 months after treatment, with at least 2 control angiograms; regional flow-related angiographic modifications were registered by using a new angiographic outcome scale for flow diverters. Data were analyzed with emphasis on procedure-related events, angiographic results, and clinical outcome.
Fifty-eight patients were included in the study, with 63 MCA bifurcation aneurysms; 13 of these were large and giant. Pretreatment mRS was 0 for 12 patients (20.7%), 1 for 41 (70.7%), and 2 for 5 patients (8.6%). Six-month control revealed mRS 0-2 for 57 (98.3%) patients and 3 for 1 (1.7%) patient. Procedure-related morbidity and mortality were 8.6% (5/58) and 0%, respectively. From 95% of still circulating immediate postprocedure angiographic outcomes, 68% progressed to aneurysm occlusion at 6 months and 95%, to occlusion at 12 months, with a 0% aneurysm rupture rate.
Flow diverters seem to be an effective treatment alternative for complex MCA bifurcation aneurysms, with reasonable complication rates. Longer angiographic follow-ups are needed to assess the morphologic outcome; immediate subtotal occlusions do not seem to be related to rupture 10).
Bhogal et al. retrospectively reviewed there prospectively maintained database to collect information for all patients with unruptured saccular bifurcation MCA aneurysms treated with FDS between January 2010 and January 2016. In addition to demographic data, they recorded the location, aneurysm characteristics, previous treatments, number and type of FDS, complications, and clinical and angiographic follow-up.
The search identified 13 patients (7 males) with an average age of 61.7 years (47-74 years). All patients had a single bifurcation aneurysm of the MCA, and none of the aneurysms were acutely ruptured. The average fundus size of the saccular aneurysms was 3 mm (range 1.5-10 mm). Follow-up studies were available for 12 patients. Based on the most recent follow-up angiograms, six aneurysms (50%) were totally occluded; five aneurysms (41.7%) showed only a small remnant; and one aneurysm (8.3%) remained unchanged. One patient suffered from an ischemic stroke with resultant permanent hemiparesis (mRS 3). In another case, there was an in-stent thrombosis during the intervention, which resolved upon intra-arterial infusion of Eptifibatide (mRS 0). There were no intra-operative vessel or aneurysm ruptures and no mortalities. Angiography of the covered MCA branches showed no change in the caliber or flow of the vessel in six (50%), a reduction in caliber in five (41.7%), and a complete occlusion in one (8.3%). All caliber changes and occlusions of the vessels were asymptomatic.
91.7% of treated MCA bifurcation aneurysms were either completely occluded or showed only a small remnant with a good safety profile. Flow diversion of MCA bifurcation aneurysms should be considered as an alternative treatment strategy when microsurgical clipping or alternative endovascular treatment options are not feasible 11).
Patients with MCAAs were treated by flow diversion if surgical or other endovascular treatment modalities had failed or were deemed likely to fail. Angiographic and clinical outcome of these patients was assessed retrospectively. Aneurysm location on MCA was defined as M1 segment, “true bifurcation” (classical bifurcation of MCA into superior and inferior trunks), “variant bifurcation” (bifurcation of early frontal or early/distal temporal branches), or M2 segment. Aneurysm morphology was classified as saccular versus dissecting/fusiform.
Treatment was attempted in 29 MCAAs. Technical failure rate was 3.4% (1/29). Thirteen of aneurysms were fusiform. Of the bifurcation aneurysms, most (10/16) were the variant type. Overall and procedure-related mortality/permanent morbidity rates were 10.3% (3/29) and 3.5% (1/29). Total occlusion rates (mean angiographic follow-up 10.3 months) for saccular and fusiform aneurysms were 40% and 75%, respectively. In bifurcation aneurysms, occlusion was strongly associated with side-branch occlusion (P < 0.005).
In this series, flow diversion for the treatment of MCAAs was safe, was effective in the treatment of fusiform MCAAs, and was not as effective at mid-term for MCA bifurcation aneurysms. Unsatisfactory occlusion rate in bifurcation aneurysms likely results from residual filling of the aneurysms in cases in which the jailed side branch remains patent 12).
Fourteen patients with 15 aneurysms were included in the study. Ischemic complications, as confirmed by MR imaging, occurred in 6 patients (43%). Procedure-related morbidity and mortality at last follow-up were 21% and 0%, respectively. Angiographic follow-up was available for 13 aneurysms, with a mean follow-up of 16 months. Complete occlusion was obtained for 8 aneurysms (62%).
Compared with other available therapeutic options, the flow-diverter stent does not appear to be a suitable solution for the treatment of saccular MCA bifurcation aneurysms 13).
From February 2010 to December 2013, 14 patients (10 women; mean age 59 years) with 15 small MCA aneurysms were treated with FDD. All procedures were performed with the Pipeline embolization device (PED).
Complete occlusion was obtained in 12/15 aneurysms (80%) and partial occlusion in 3 (20%). Among 13 aneurysms with a side branch, this was patent at the angiographic control in 4 cases, showed decreased filling in 6, and was occluded in 3 (with neurological deficits in 2). All PEDs were patent at follow-up. Post-procedural ischemic complications occurred in 4 (27%) procedures with permanent neurological deficit (modified Rankin score 2) in 3 (21%). No early or delayed aneurysm rupture, no subarachnoid or intraparenchymal hemorrhage and no deaths occurred.
Endovascular treatment with FDD is a relatively safe treatment for small MCA aneurysms resulting in a high occlusion rate. The findings suggest that complete occlusion after endovascular treatment with FDD can be delayed (>6 months). Ischemic complications may occur as early or delayed, particularly at clopidogrel interruption 14).
Twenty-five aneurysms located at the MCA bifurcation (n = 21) or distal (n = 4) were treated. Of these, 22 were small and 3 were large. A single device was used in all but 2. No deaths occurred in the series. All patients had at least 1 control angiographic study, 21 of which were DSA (3-30 months), which showed that 12 of the rising branches were patent whereas 6 were filling in reduced caliber and 3 were occluded asymptomatically. According to the last angiographic follow-up, complete occlusion was revealed in 21 of 25 aneurysms (84%).
The Pipeline Embolization Device provides a safe and effective treatment alternative for wide-neck MCA aneurysms that give rise to a bifurcating or distal branch when other endovascular techniques are thought to be unfeasible or more risky 15).
Thirty-three patients with 34 MCA aneurysms were treated with the Woven EndoBridge (WEB) in 5 European centers. The ability to successfully deploy the WEB, procedure- and device-related adverse events, morbidity and mortality of the treatment, and short-term angiographic follow-up results were analyzed.
Most treated aneurysms were unruptured (85.3%) and were between 5 and 10 mm (85.3%) with a neck size ≥ 4 mm (88.2%). The treatment failed in 1 of the 34 aneurysms (2.9%) owing to a lack of appropriate device size. Treatment was performed exclusively with the WEB in 29 of 33 aneurysms (87.9%). Additional treatment (coiling and/or stenting) was used in 4 of 33 aneurysms (12.1%). Mortality of the treatment was 0.0% and morbidity was 3.1% (intraoperative rupture with modified Rankin Scale score of 3 at the 1-month follow-up). In short-term follow-up (range, 2-12 months), adequate occlusion (total occlusion or neck remnant) was observed in 83.3% of aneurysms.
WEB flow disruption seems to be a promising technique for the treatment of complex MCA aneurysms, particularly those with a wide neck or unfavorable dome-to-neck ratio 16).
Burrows et al. present the case of an adolescent with a middle cerebral artery (MCA) fusiform aneurysm which recurred following clip reconstruction and bypass. The aneurysm was successfully treated with endovascular flow diversion 17).