Objective This study aimed to reveal the clinical significance of the platelet reactivity unit (PRU) and the efficacy of adjunctive cilostazol and its association with thromboembolic and microembolic events after coil embolization for unruptured intracranial aneurysms (UIAs).

Methods We retrospectively analyzed the data of 427 patients with UIAs who underwent endovascular treatment between July 2011 and June 2014. When clopidogrel resistance was confirmed via PRU assay after dual antiplatelet medication (aspirin plus clopidogrel) administration for 5 days, triple antiplatelet therapy with cilostazol was administered (Group I, 274 patients). The other group was placed on standard dual antiplatelet therapy (Group II, 153 patients). All patients underwent magnetic resonance diffusion-weighted imaging within 2 days after endovascular coiling.

Results No significant associations with the occurrence of thromboembolic and microembolic events were found between the groups. The occurrence of thromboembolic and microembolic events showed no statistical difference between groups I and II (p = 0.725 for thromboembolic events and p = 0.109 for microembolic events). Also, the PRU value and the occurrence of microembolic events, using a PRU cutoff value of 240, showed no statistical difference (p = 0.114 in group I and 0.064 in group II). There was significant increase in microembolic events after the use of a stent-assisted endovascular procedure. As the PRU value increased, there was a trend toward an increase in the mean number of microembolic lesions without statistical significance.

Conclusion Even though there is a presumed anti-thromboembolic effect for clopidogrel resistance in other literature, the clinical efficacy of adjustment of additional cilostazol for endovascular coiling of unruptured aneurysms may be limited due to the unspecified cutoff value of the PRU assay for evaluating the resistance.

Disclosures J. Ahn: None. J. Park: None.