Local thrombus formation at the coil-parent artery interface during endovascular coil embolization of cerebral...

Fresh thrombus formation at the coil-parent artery interface around the neck of aneurysms is sometimes observed during coil embolization of cerebral aneurysms. We retrospectively analyzed the factors associated with local acute thrombus formation from the data of patients treated over a period of 5 years at our institute.

Between November 2004 and March 2009, 242 patients harboring 250 aneurysms were treated with endovascular coil embolization at our institute. The patients were divided into two groups: Group A included 107 patients who were treated and followed up during the initial 29 months of the study, and group B included 135 patients who were treated and followed up during the later 24 months of the study. Clinical and angiographic variables of the procedures were statistically tested for correlation with thrombus formation in the parent arteries.

Fresh thrombus formation occurred in six patients with unruptured aneurysms (15%) and 11 patients with ruptured aneurysms (14%) in group A. Among the patients with unruptured aneurysms, the dome-to-neck ratio and location of the aneurysms were independently associated with the risk of thrombus formation, whereas among patients with ruptured aneurysms, a higher World Federation of Neurological Surgeons (WFNS) grade and longer interventional duration were significantly associated with thrombus formation. However, fresh thrombus formation occurred in only two patients with unruptured aneurysms (2.9%) and three patients with ruptured aneurysms (4.4%) in group B. There were no factors that were significantly associated with thrombus formation in all Group B patients.

With regard to coil embolization treatment, anatomical and morphological factors seem to be related to intraprocedural thrombus formation in patients with unruptured aneurysms, whereas duration of the intervention and preoperative status are associated factors in patients with ruptured aneurysms. Careful comparison of the thrombus with control angiograms is important to prevent thrombembolic complications. Moreover, the rate of fresh thrombus formation during coil embolization has decreased over the past 5 years at our institute, suggesting the possibility of lowering the incidence of these complications by early detection and treatment.