Frequency and Characteristics of Paraclinoid Aneurysm in Ruptured Cerebral Aneurysms

Objective : This study aimed to determine the frequency of paraclinoid aneurysms among ruptured cerebral aneurysms and compare paraclinoid aneurysms with other aneurysms to clarify the characteristics of ruptured paraclinoid aneurysms.Methods : This study included 970 ruptured cerebral aneurysms treated at our hospital between 2003 and 2020.Results : There were 15 cases (1.3%) of paraclinoid aneurysms with maximum diameters of 5-22 mm (mean +/- standard deviation [SD], 11.6 +/- 5.4 mm). Treatment consisted of clipping in four patients and endovascular treatment in 11. Factors significantly different in multivariate analysis for paraclinoid aneurysms compared with those for other aneurysms were a history of hypertension (odds ratio [OR], 1.2-9.8; p=0.021) and aneurysm >= 10 mm (OR, 7.5-390.3; p<0.001). The sites of paraclinoid aneurysm were ophthalmic artery type in nine patients, anterior wall type in five, medial wall type in one, and ventral wall type in zero. The medial wall type (22 mm) was significantly larger than the ophthalmic artery type (mean +/- SD, 7.2 +/- 2.0 mm) (p=0.003), and the anterior wall type (mean +/- SD, 12.2 +/- 4.8 mm) was significantly larger than the ophthalmic artery type (p=0.024).Conclusion : This study showed a low frequency of paraclinoid aneurysms among ruptured cerebral aneurysms. Most were upward-facing with relatively large aneurysms, and no aneurysms were smaller than 5 mm. With recent advances in endovascular treatment devices, paraclinoid aneurysms are easily treatable. However, the treatment indication of each paraclinoid aneurysm should be carefully considered.