CISS画像による傍前床突起部未破裂脳動脈瘤の評価と平均5年間の経過観察からみた治療方針

抄録

Paraclinoid aneurysms generally have benign natural history. The risk of rupture, however, may vary due to the anatomical environment of the individual aneurysm. When dural and bony structure surround the aneurysm, the risk is small; alternately, when it is mostly exposed in the cerebrospinal fluid space, the risk is more significant. This study aims to reveal the natural history of paraclinoid aneurysms that are covered and anatomically “protected” by the surrounding dura and the bone. Patients with paraclinoid aneurysms with 50 to 100% of the surface covered by the endocrania of the skull base were enrolled. During 2003 and 2017, 119 patients with 125 aneurysms were prospectively followed for up to 15 years using MRA with a 6- to 12-months interval. Not a single instance of subarachnoid hemorrhage was observed in the series. In addition, no aneurysm showed enlargement or transformation during the observation period (642 aneurysm-years). Based on the observation of the very benign natural history of these paraclinoid aneurysms, surgical or endovascular intervention should not be recommended during the first diagnosis. Moreover, they should be kept under close follow-up observation with repeat MRA.