Rupture of Very Small Intracranial Aneurysms: Incidence and Clinical Characteristics

OBJECTIVE: Unruptured intracranial aneurysms are now being detected with increasing frequency in clinical practice. Results of the largest studies, including those of the International Study of Unruptured Intracranial Aneurysms, indicate that surgical and endovascular treatments are rarely justified in small aneurysms. However, we have encountered several cases of rupture of small and very small aneurysms in our clinical practice. This retrospective study analyzed the incidence and clinical characteristics of very small ruptured aneurysms. MATERIALS AND METHODS: A total of 200 patients with aneurysmal subarachnoid hemorrhage between January 2012 and December 2014 were reviewed. Various factors were analyzed, including the aneurysm location and size as well as the associated risk factors. RESULTS: The mean age of patients was 56.31 ± 13.78 (range, 25-89) years, and the male to female ratio was 1:2.1. There were 94 (47%) small-sized (< 5 mm), 91 (45.5%) medium-sized (5-9.9 mm), and 15 large-sized (> 10 mm) aneurysms. Of these, 30 (15%) aneurysms were very small-sized (< 3 mm). The most frequent site of aneurysms was the anterior communicating artery (ACoA). However, the proportion of aneurysms at the ACoA was significantly high in very small aneurysms (53.3%, p = 0.013). Hypertension was a significant risk factor for rupture of very small aneurysms (p < 0.001). CONCLUSION: About half of our cases of ruptured aneurysms involved the rupture of small and very small aneurysms. The most common site of rupture of very small aneurysm was the ACoA. Rupture of small and very small aneurysms is unpredictable, and treatment may be considered in selected high-risk patients according to factors such as young age, ACoA location, and hypertension.