遠位部前大脳動脈瘤に対する手術戦略

抄録

Objective: Distal anterior cerebral artery (distal ACA) aneurysms are relatively rare, and have unique clinical and surgical features compared with intracranial aneurysms at other sites. In this study, we reviewed 24 patients with distal ACA aneurysms with regard to preoperative planning and surgical strategies.
Material and methods: Of 24 patients, 15 were women and nine were men. Nineteen had ruptured aneurysms, whereas the remaining five had unruptured aneurysms. The aneurysms were located in four different parts of the distal ACA: two in the superior part of A3, 15 in the anterior part of A3, six in the inferior part of A3, and one in the trunk of A2.
Results: All patients underwent surgery via the unilateral frontal interhemispheric route. The location of craniotomy was adjusted anteriorly, depending on the positional relationship of the aneurysm and the genu of the corpus callosum identified through sagittal three-dimensional computed tomography maximum intensity projection (3D-CT MIP) imaging. In all cases, we first entered the interhemispheric fissure towards the back of the aneurysm. The distal segment of the pericallosal artery was identified and dissected in a retrograde manner toward the aneurysm. We were able to predict the location of the aneurysm by recognizing the branching points of the cortical arteries, such as the middle and posterior internal frontal artery. We were able to approach the distal neck of the aneurysm as expected. As the dome of the aneurysm usually extended to the right or left side, exploration of the proximal segment of the pericallosal artery could be achieved by passing the opposite side of the dome. In 22 of the 24 patients, proximal control of the parent artery was achieved before preparation of the neck. In the remaining two patients, proximal control was achieved using tentative clipping. At the time of clip placement, parallel clipping of the pericallosal artery was required in nine patients, double clipping in four, and shank clipping in two. No patient experienced premature rupture during the procedure.
Discussion and conclusion: 3D-CT imaging was very useful in planning the surgical strategy; it not only indicated the location of the aneurysm but also the location of the frontal bridging vein and the genu of the corpus callosum. We were able to determine the optimal location of the craniotomy on the basis of sagittal 3D-CT MIP imaging.
The procedure, which involves approaching the aneurysm in a retrograde manner from the distal segment of the pericallosal artery, is considered safe because of good orientation and a low incidence of premature rupture.
The parent artery is generally small compared with the aneurysmal neck; therefore, maximum precautions against kinking of the parent artery should be taken during clip placement.
We concluded that the surgical management of distal ACA aneurysms is challenging, but safe with sufficient preoperative evaluation and experience.