Current Management of Asymptomatic Small (^|^lt;5 mm) Unruptured Intracranial Aneurysms (UIAs): Analysis of Cases from a Single Center Experience and the Nagasaki UIA Registry

Elective surgery for asymptomatic small (<5 mm) unruptured intracranial aneurysms (UIAs) remains controversial. To reveal the current trend and outcomes in the management of (UIAs) in daily clinical practice, we retrospectively analyzed treatment options and surgical morbidity of small UIA cases in our institute (Group A: 129 aneurysms) and from the Nagasaki UIA Registry (Group B: 610 aneurysms) over the four recent years (2006–2009). After discreet discussions including recent prospective data of rupture risk and guidelines for treatment of small UIAs as part of informed consent procedure, only 7% (9 aneurysms) of the patients in Group A chose surgical treatment of either clipping or coiling, on which no intra- or post-surgical morbidity was observed. Direct surgical or endovascular interventions were performed in 267 aneurysms in Group B, in which a significant number of complications were reported (mRS≥2=5.9%; mRS 1=7.7%, at three months after the surgery). In view of recent studies suggesting low annual rupture rates (0.3–0.5%/yr) with significant morbidity rates (2–7%) of small UIAs, more conservative management should be considered, especially for UIAs smaller than 5 mm.