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  • Author or Editor: Akira Ogawa x
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Akira Ogawa, Michiyasu Suzuki, Yoshiharu Sakurai and Takashi Yoshimoto

✓ Direct operations were performed on 206 patients with aneurysms of the anterior communicating artery (ACoA) using a bifrontal craniotomy and an interhemispheric approach. A total of 44 (21.4%) of these patients had vascular anomalies in the vicinity of the ACoA; these included a median artery of the corpus callosum (MACC) in 27 cases (13.1%), duplication of the ACoA in 20 (9.7%), and duplication of the A1 segment of the anterior cerebral artery in one (0.5%). A retrospective study of the angiograms indicated that diagnosis of the A1 or ACoA duplication was not possible; only 11 (41%) of the 27 MACC's were easily identified, while eight (30%) could not be diagnosed. The majority of the cases of ACoA aneurysms with MACC (81.5%) showed trifurcation of the ACoA, A2, and MACC. The operative results in the patients with MACC did not differ significantly from the results of the entire ACoA aneurysm series. From the above study it is concluded that, regardless of whether a vascular anomaly has been identified preoperatively, ACoA aneurysm surgery should be undertaken with that possibility in mind. A bifrontal craniotomy and an interhemispheric approach has the advantage of allowing for a wide operative field and the attainment of a good understanding of the vascular structures near the ACoA. It is particularly useful in cases of vascular anomaly in this region.

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Akira Ogawa, Motonobu Kameyama, Kenji Muraishi, Takashi Yoshimoto, Masatoshi Ito and Yoshiharu Sakurai

✓ In order to clarify the effectiveness of extracranial-intracranial bypass operations in patients with vertebrobasilar occlusive disease, the authors used positron emission tomography to investigate the cerebral blood flow (CBF) and metabolism of eight patients undergoing superficial temporal artery (STA)-superior cerebellar artery (SCA) bypass procedures. In the preoperative studies, CBF in the region of the posterior fossa was low and the oxygen extraction fraction (OEF) was high, the so-called “misery perfusion syndrome.” Such changes were evident in both the posterior circulation and the anterior circulation regions. Postoperatively, there was a significant increase in CBF, a significant decrease in the OEF not only in the region of posterior circulation but also over the entire brain, and a disappearance of the uncoupling between CBF and oxygen metabolism. The STA-SCA bypass procedure is effective in improving CBF and metabolism in patients with vertebrobasilar occlusive disease.

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Michiyasu Suzuki, Takehide Onuma, Yoshiharu Sakurai, Kazuo Mizoi, Akira Ogawa and Takashi Yoshimoto

✓ This study reviews aneurysms of the proximal segment (A1) of the anterior cerebral artery in 38 patients (23 men and 15 women) and their surgical, angiographic, and clinical management. Thirty-seven aneurysms were saccular and one was fusiform. The incidence of A1 aneurysms among a total of 4295 aneurysm cases treated was 0.88%. Multiple aneurysms occurred in 17 patients (44.7%) of the 38 cases; in 10 (58.8%), there was bleeding from the A1 aneurysm. The aneurysms were classified into five categories according to the mode of origin of the aneurysm in relation to the A1 segment: in 21 cases, aneurysms originated from the junction of the A1 segment and a perforating artery; in eight, from the A1 segment directly; in six, from the proximal end of the A1 fenestration; and in two, from the junction of the A1 segment and the cortical branch. One patient had a fusiform aneurysm. Computerized tomography (CT) of these aneurysms revealed bleeding extending to the septum pellucidum similar to that of anterior communicating artery aneurysms. When performing radical surgery it is very important to recognize the characteristics of A1 aneurysms, including multiplicity, a high incidence of vascular anomalies (especially A1 fenestration), and their similarity to anterior communicating artery aneurysms on CT.