However, case series tend to suggest that anti- thrombotic therapy lowers the risk of recurrent ischemic events compared with the natural his- There are also no prospective RCTs comparing antiplatelet strategies (either aspirin or second-generation antiplatelet drugs) with anticoagulation. The case series reviewed dem- onstrated no clear or consistent benefit for 1 form of antithrombotic therapy over another.760 763 Although 1 small case series favored anticoagu- lation, not all of the patients in that series pre- sented with ischemic symptoms, and the series consisted of patients with fusiform aneurysms rather than true vertebrobasilar dolichoecta- Although the risks of hemorrhage appear to be low in patients presenting with ischemic there are insufficient data to pro- vide a recommendation for anticoagulation over antiplatelet therapy. Knowledge Gaps and Future Research Many important issues about the management of patients with vertebrobasilar dolichoectasia remain unclear. Some of these include the following: Development of an agreed-on definition for ver- tebrobasilar dolichoectasia that is distinguishable from the definition of a fusiform aneurysm. Accumulation of more robust natural history data with detailed clinical outcomes. Clarification of the type, dosing regimens, and efficacy of antiplatelet therapy versus anticoagu- lation for primary and secondary ischemic stroke prevention. Improved understanding of the role of reconstruc- tive procedures, whether endovascular or open surgical, in the management of patients with verte- brobasilar dolichoectasia. 5.18. Embolic Stroke of Undetermined Source Recommendations for ESUS Referenced studies that support recommendations are summarized in online Data Supplement 56. COR LOE Recommendations Benefit B-R In patients with ESUS, treatment with direct oral anticoagulants is not recommended to reduce risk of secondary stroke.779,780 Benefit B-NR In patients with ESUS, treatment with ticagre- lor is not recommended to reduce the risk of Synopsis ESUS is an evolving stroke subtype commonly defined as a nonlacunar cryptogenic ischemic stroke. 