Abstract
The natural history of the unruptured aneurysm is not clear. We retrospectively analyzed 7 cases with 10 unruptured aneurysms and in the literature 18 similar cases with 23 aneurysms that expanded or newly formed due to natural causes.
In our series, the diameters of the aneurysms of the first angiograms were AN1 (mm) 0 to 28.63 (mean 8.40, median 6.45). Those of the last angiograms were AN2 (mm) 1.82 to 30.11 (mean 11.38, median 8.53). They were performed after 5.8 years of mean follow-up period: (=Int). The growth of the aneurysm diameter was G (mm)=AN2-AN1, 1.47 to 7.15 (2.98±2.02). The growth rate was Gratio (mm/yrs)=G/Int, 0.22 to 2.52 (0.71±0.70). In our series, 4 of 10 aneurysms were ruptured, and the remaining were intact. The mean diameter of the ruptured aneurysms expanded from AN1: 7.69 to AN2: 12.39. The unruptured ones expanded from AN1: 8.87 to AN2: 10.70. G of the ruptured aneurysm group was 4.70. The unruptured group was 1.83. Between these two Gs were significant differences. Gratio of the ruptured aneurysm group was 1.26. The unruptured group was 0.34. These two Gratios also had significant differences.
In our series AN2 of the ruptured aneurysm group was 12.39. This was larger than the unruptured group (10.70). This does not contradict findings in the literature that unruptured aneurysms whose sizes are over 7mm~10mm have more risks of rupture.
Together with our series and the literature's, there were 18 de novo aneurysms. Five were so called “mirror image” aneurysms, so suspected one of the causes of the de novo aneurysm was congenital defect of the media, for example.
In our series the aneurysms whose Gs were equal to or grater than 2.5mm, or whose Gratios were equal to or greater than 20.49mm/years ruptured. We therefore consider 2.5mm≤G or 20.49mm/years≤Gratio as risk factors.
We emphasize the need to estimate and follow up the sizes of the unruptured aneurysms with noninvasive examinations like MRA or CTA. If the sizes of the unruptured aneurysms are expanding by 2.5mm≤G or 20.49mm/years≤Gratio, the aneurysms have more risks of rupture, so some kind of surgical intevention is recommended.
