Comparison of Rates of Growth between Unruptured and Ruptured Aneurysms Using Magnetic Resonance Angiography

Background and Purpose: Growth is a key risk factor for rupture of unruptured cerebral aneurysms. There are few reports of investigations into the actual growth of ruptured intracranial aneurysms. The aim of the present study was to ascertain the risk of rupture of aneurysms based on the growth of unruptured and ruptured aneurysms. Methods: Changes in size on magnetic resonance angiography (MRA) were examined in 50 patients with ruptured cerebral aneurysms. Images obtained before and after subarachnoid hemorrhage were used. Moreover, changes in aneurysm size were retrospectively examined in 73 patients with 100 unruptured cerebral aneurysms that were followed serially with MRA that was performed using a 1.5-T or 3-T system. The size of the aneurysm was determined by measuring the maximum diameter on maximum intensity projection MRA images. Based on these data, the annual growth rates (mm growth/year) of unruptured and ruptured aneurysms were calculated and compared. Results: The median annual growth rate of ruptured aneurysms was significantly greater than that of unruptured aneurysms (.69 versus.077 mm/year, P < .01). The annual growth rates of ruptured aneurysms showed a negative correlation between the duration from initial MRA to the time of rupture. Conclusion: A high annual growth rate is a key risk factor for aneurysm rupture. This finding provides strong evidence for the treatment of unruptured cerebral aneurysms.