Impact of Platelet Function Testing on Thrombotic Events in Intracranial Aneurysm Flow Diversion

Background The role of platelet function testing in patients with intracranial aneurysms undergoing flow diversion remains controversial with limited evidence of its influence on thrombotic outcomes. We report an observational cohort analysis evaluating whether P2Y12 assay testing is associated with lower thrombotic events in patients undergoing flow diversion. Methods We performed a retrospective review of a single center prospectively maintained procedural database to identify patients who underwent flow diversion between March 2015 and July 2025. One physician within our practice never performs P2Y12 assay testing. The remaining physicians utilize P2Y12 assay testing as part of routine practice. These two different patient cohorts were compared. Acute thrombotic events were our primary outcome. Secondary outcomes included delayed intracerebral hemorrhage, intimal hyperplasia without clinical sequalae, and transient neurologic deficits. Results We identified 397 unruptured aneurysm patients who underwent flow diversion at our institution between March 2015 and July 2025. Median age was 58 years old (Interquartile range (IQR) 49‐67), with 328 females (83%) and 69 males (17%). Out of 397 patients, 283 (71%) patients were treated by physicians who performed routine pre and postoperative testing of aspirin and Plavix assays, with subsequent adjustment of antithrombotic dosing accordingly, while 114 patients (29%) were treated with aspirin and clopidogrel pre‐and post‐operatively without testing.Eighteen out of 397 patients (4.5%) had an acute thrombotic event requiring intraarterial anti‐thrombotic infusion or urgent thrombectomy, or both. Of these, 16 were from the 283‐patient testing cohort (5.6%), and two in the 114 patients non‐testing cohort (1.8%) (p=0.09). Patients experiencing a thrombotic event had similar demographics, vascular risk factors, maximal aneurysmal diameter, and stent diameter. In a multivariable analysis adjusting for hypertension, stent diameter, aneurysmal diameter and age, P2Y12 sensitivity assay testing was not significantly associated with acute thrombotic events in aneurysm patients undergoing flow diversion (Odds ratio (OR)=1.5, 95% Confidence Interval (CI)= 0.15‐3.4), p=0.057). Secondary outcomes were comparable between both groups; transient neurologic deficits were noted in 36/283 in the testing group (13%), and 18/114 in the non‐testing group (16%) (p=0.4),endothelial hyperplasia was noted in 40/283 in the testing group (14%), and 12/114 in the non‐testing group (11%) (p=0.3), and intracranial hemorrhage occurred in 1 patient in the testing group (p>0.9). Conclusion Platelet function testing was not correlated with thrombotic events or patient outcomes in this single center series. While platelet function testing is widely used in patients undergoing flow diversion of intracranial aneurysms there remains insufficient to suggest such testing is necessary. Larger prospective studies are required.