Flow diversion devices are a relatively recent addition to the endovascular arsenal for the treatment of intracranial aneurysms, and have been typically employed when more common endovascular or surgical options may not be feasible such as for morphologically complex or surgically inaccessible lesions. They are a mesh structure similar to a stent passed across the aneurysm neck that functions to divert blood flow from the aneurysm, allowing it to occlude over time.
Although small single- and multi-center studies have reported favorable results, their efficacy and safety have not been evaluated on a larger scale. Waleed Brinjikji and colleagues report in Stroke a first-of-its-kind random-effects meta-analysis of 29 studies of flow diverter treatment across varied clinical and aneurysm populations. Efficacy and safety profiles were compiled based upon rates of aneurysm occlusion, short-/long-term complications, morbidity and mortality. On average, at 6 months, flow diverters achieved a 76% occlusion rate with morbidity and mortality rates of 5 and 4% respectively. Complications over this time (SAH 4%; Ischemic stroke 6%; intraparenchymal hemorrhage 3%; perforator infarction 3%) were low, but not negligible. Further analyses evaluated effects of aneurysm size (small versus large/giant) and location (anterior versus posterior circulation) on each of these. Overall, small size and anterior location were associated with fewer complications. Importantly, for large/giant aneurysms, risk of SAH and ischemic stroke was highest; whereas, for posterior aneurysms, risk of ischemic and perforator stroke was highest.
So, should we start shelving our conventional coiling, stenting and clipping techniques for these new devices? Not so fast. Although this analysis provides evidence that flow diverters are a feasible and effective treatment option for aneurysms, their associated rates of morbidity and mortality are not without concern. Further, this study is not without significant limitation that leaves its quality of evidence low: both as a meta-analysis and from the methodologies of the studies it includes. Therefore, its results neither can be applied to specific clinical and aneurysm populations, nor can they be used for comparison with efficacy and safety profiles of other treatments. Nevertheless, this analysis lends traction to the need for continued study of the flow diverter especially in prospective, randomized head-to-head comparison with more established endovascular and surgical methods of aneurysm treatment.