Enlargement of small, asymptomatic, unruptured intracranial aneurysms in patients with no history of subarachnoid hemorrhage: the different factors related to the growth of single and multiple aneurysms.

OBJECT: This study was performed to investigate the risk factors related to the growth of small, asymptomatic, unruptured aneurysms in patients with no history of subarachnoid hemorrhage (SAH).
METHODS: Between January 2005 and December 2010, a total of 508 patients in whom unruptured intracranial aneurysms were diagnosed at the University of California, Los Angeles medical center did not receive treatment to prevent rupture. Of these, 235 patients with no history of SAH who had asymptomatic, small, unruptured aneurysms (<7 mm) were monitored with 3D CT angiography images. Follow-up images of the lesions were used to measure aneurysm size changes. Patient medical history, family history of SAH, aneurysm size, and location were studied to find the risk factors associated with small aneurysm growth.
RESULTS: A total of 319 small aneurysms were included, with follow-up durations of 29.2±20.6 months. Forty-two aneurysms increased in size during the follow-up; 5 aneurysms grew to become ≥7 mm within 38.2±18.3 months. A trend of higher growth rates was found in single aneurysms than in multiple aneurysms (p=0.07). A history of stroke was the only factor associated with single aneurysm growth (p=0.03). The number of aneurysms (p=0.011), number of aneurysms located within the posterior circulation (p=0.030), and patient history of transient ischemic attack (p=0.044) were related to multiple aneurysm growth.
CONCLUSIONS: Multiple small aneurysms are more likely to grow, and multiple aneurysms located in the posterior circulation may require additional attention. Although single aneurysms have a lower risk of growth, a trend of higher growth rates in single aneurysms was found.