Endovascular treatment of very small unruptured aneurysms: rate of procedural complications, clinical outcome, and anatomical results.

BACKGROUND AND PURPOSE The strategy of treatment of small unruptured intracranial aneurysms is complex because of their presumably low risk of rupture. A precise knowledge of the perioperative complications in this specific subgroup is mandatory. The purpose of this study was to compare the results of the endovascular treatment of aneurysms ≤ 3 mm and aneurysms > 3 mm included in the Analysis of Treatment by Endovascular Approach of Nonruptured Aneurysms study. METHODS The study included 626 patients harboring 682 unruptured aneurysms. Perioperative adverse events and clinical outcome were analyzed in patients treated for aneurysms ≤ 3 mm (51 patients, 51 aneurysms) and in patients treated for aneurysms > 3 mm (575 patients, 631 aneurysms). RESULTS Endovascular treatment failed more often in aneurysms ≤ 3 mm (13.7%) compared to aneurysms > 3 mm (3.3%; P = 0.003). The rate of intraoperative rupture for aneurysms ≤ 3 mm (3.9%; 95% CI, 0.5-13.5) did not significantly differ compared to aneurysms > 3 mm (2.4%; 95% CI, 1.2-3.6; P = 0.37). Thromboembolic events were not significantly different in both groups (3.9%; 95% CI, 0.5-13.5 in very small aneurysms and 7.1%; 95% CI, 5.1-9.1 in larger aneurysms; P = 0.57). One month morbidity/mortality was not significantly different for patients with very small aneurysms (2.0%; 95% CI, 0.05-10.45) and for patients with larger aneurysms (3.3%; 95% CI, 1.8-4.8; P = 0.60). CONCLUSIONS The risks of endovascular treatment are similar in patients with very small or with larger aneurysms. Because the risk of spontaneous rupture is lower in very small aneurysms, their management will include follow-up MRI and active treatment in case of morphological modification.