Endovascular coil embolization of very small intracranial aneurysms.

Introduction: Endovascular coil embolization of very small (maximum dome diameter ≤3 mm) aneurysms is controversial because of a high risk for procedural rupture and technical difficulty. We report clinical and angiographic results of coil embolization of these aneurysms.

Methods: From August 2005 through July 2009, 43 very small aneurysms (23 ruptured, 20 unruptured) in 38 patients (12 males, 26 females; mean age, 53 years) were embolized with detachable coils. Of those 38 patients, 24 (63%) presented with subarachnoid hemorrhage (SAH) from a very small aneurysm (n = 23) or another aneurysm (n = 1). We assessed initial angiographic results, procedural complications, and clinical condition with initial Hunt and Hess grade (HH) and Glasgow outcome scale (GOS) at discharge. Follow-up results were evaluated with conventional angiography and/or magnetic resonance angiography (MRA).

Results: Initial aneurysmal occlusion was total in 16 (37%), subtotal in 22 (51%), and partial in five (12%) aneurysms. There were five incidents of thrombosis (12%) and one procedural rupture (2%), but there was no definite adverse effect on clinical outcome. Of 24 patients with SAH, ten patients (42%) were in poor condition (HH 3 or 4) at admission. Seventeen of 24 patients (71%) had good or excellent outcome (GOS ≥4) at discharge. A 6-month or more follow-up angiography and/or MRA was available in 33 (11 total and 20 subtotal and 2 partial in initial occlusion) aneurysms (77%) in 28 patients and revealed stable occlusion in 20 aneurysms (61%), progressive total occlusion in 10 (30%), minor recanalization in 2 (6%), and major recanalization in 1 (3%).

Conclusions: Coil embolization of very small aneurysms may be technically feasible with favorable clinical/angiographic outcomes and relatively low recanalization rate during 6 months or more follow-up period.