Antithrombotic Therapy

Symptomatic cerebral atherosclerosis including intracranial atherosclerosis (ICAS) is associated with a high risk of recurrent stroke. Antithrombotic agents are the mainstay of therapy in these patients. Several studies have found anticoagulation (warfarin) to increase the risk of bleeding events and have an efficacy no better than that of aspirin. Therefore, anticoagulants are not widely used unless patients develop recurrent ischemic symptoms despite receiving antiplatelet therapy. Because ICAS progression is not uncommon and the risk of stroke recurrence is high when aspirin monotherapy is used, dual antiplatelet agents may be needed at least in the early disease stage. The Trial of Cilostazol in Symptomatic Intracranial Stenosis (TOSS) found that aspirin plus cilostazol was significantly better than aspirin monotherapy in preventing progression (6.7 vs. 28.8%, p = 0.008). The TOSS II trial that compared aspirin plus cilostazol with aspirin plus clopidogrel found no significant difference in the progression rate (9.3% vs. 15.5%, p = 0.092). However, the overall changes in stenosis were more favorable (i.e., less progression and more regression) in the cilostazol group (p = 0.049). TOSS studies have limitations in that the end points were changes in magnetic resonance angiography results rather than clinical outcomes. Based on the Clopidogrel in High-Risk Patients with Acute Nondisabling Cerebrovascular Events (CHANCE) trial results, and the fair outcome found in patients enrolled in the SAMMPRIS (Stenting versus Aggressive Medical Therapy for Intracranial Arterial Stenosis) trial, aspirin plus clopidogrel has been recommended in the early stage of symptomatic ICAS. However, the combination of aspirin and clopidogrel did not show superiority over aspirin monotherapy in ICAS patients in a recent CHANCE substudy. Considering that ICAS is the major pathology leading to stroke worldwide, further studies are needed to identify the best medication strategy in ICAS patients. Until then, physicians may choose appropriate antiplatelet agents after careful consideration of the characteristics of both the patients (i.e., degree of stenosis, stroke mechanism, risk of stroke, and risk of bleeding) and the antiplatelet agent (e.g., side effect, cost).