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Takashi Yoshimoto and Jiro Suzuki

✓The authors document angiographically the development of a large aneurysm from the funnel-shaped bulge at the origin of the left posterior communicating artery.

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Teiji Tominaga, Toshiyuki Takahashi, Hiroaki Shimizu and Takashi Yoshimoto

✓ Vertebral artery (VA) occlusion by rotation of the head is uncommon, but can result from mechanical compression of the artery, trauma, or atlantoaxial instability. Occipital bone anomalies rarely cause rotational VA occlusion, and patients with nontraumatic intermittent occlusion of the VA usually present with compromised vertebrobasilar flow.

A 34-year-old man suffered three embolic strokes in the vertebrobasilar system within 2 months. Magnetic resonance imaging demonstrated multiple infarcts in the vertebrobasilar territory. Angiography performed immediately after the third attack displayed an embolus in the right posterior cerebral artery. Radiographic and three-dimensional computerized tomography bone images exhibited an anomalous osseous process of the occipital bone projecting to the posterior arch of the atlas. Dynamic angiography indicated complete occlusion of the left VA between the osseous process and the posterior arch while the patient's head was turned to the right. Surgical decompression of the VA resulted in complete resolution of rotational occlusion of the artery.

An occipital bone anomaly can cause rotational VA occlusion at the craniovertebral junction in patients who present with repeated embolic strokes resulting from injury to the arterial wall.

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Takashi Yoshimoto, Keita Uchida and Jiro Suzuki

✓ Between June, 1961, and September, 1975, the authors operated on 60 patients with aneurysms of the anterior cerebral artery distal to the anterior communicating artery (ACoA) by a direct intracranial approach. It is of utmost importance in the treatment of aneurysms to have control of the parent artery of the aneurysm. This makes it easier and safer to approach the aneurysm neck and to handle possible premature aneurysm rupture. The aneurysms were classified into two types, ascending and horizontal. Aneurysms arising from the origin of the ACoA and including the entire portion of the knee of the corpus callosum were designated as aneurysms of the ascending portion, whereas aneurysms beyond the genu were designated as aneurysms of the horizontal portion. For aneurysms of the ascending portion, bifrontal craniotomy was considered the safest approach. For aneurysms of the horizontal portion, a small parasagittal craniotomy was determined to be sufficient.

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Jiro Suzuki, Kazuo Mizoi and Takashi Yoshimoto

✓ The authors review their experience with the bifrontal interhemispheric approach in 603 cases of single anterior communicating artery (ACoA) aneurysms and describe the operative technique. With this approach, the olfactory tracts are dissected, and both A1 segments of the anterior cerebral arteries are identified subfrontally. The interhemispheric fissure is then dissected and A2segments are followed from the distal portion toward the ACoA complex. Following the administration of a combination of mannitol, vitamin E, and dexamethasone, a temporary clip is placed on at least the dominant A1 segment prior to dissection of the aneurysm itself. Once the aneurysm has been completely freed from the surrounding structures, the neck is ligated and clipped. If the aneurysm ruptures during surgery, temporary clips are placed on both A1 and A2 segments bilaterally and the operation proceeds in a completely dry field. With this method, it is possible to occlude any of the intracranial vessels for up to 40 minutes within 100 minutes of drug administration.

To prevent the possibility of rerupture and the development of vasospasm in the period before aneurysm surgery, the authors have adopted a policy of performing ultra-early operations within 48 hours of the onset of symptoms. Among the 257 cases operated on during the 9 years since 1975, one-fifth have been operated on within 48 hours of rupture, and the in-hospital mortality rate has been only 4.3% (11 cases). Follow-up studies have shown that 87% of the 246 surviving patients have returned to useful lives.

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Jiro Suzuki, Takashi Yoshimoto and Kazuo Mizoi

✓ Results of surgical treatment of anterior communicating artery aneurysms, approached via bifrontal craniotomy, are reported in 110 cases. It was possible to preserve the olfactory tracts bilaterally or unilaterally in over 65% of these cases: 47% with bilateral preservation and 34% with unilateral preservation; 33% of the patients with bilateral olfactory tract damage reported subjectively normal olfaction. Objective examination of olfaction by an otolaryngologist showed that 84% of the patients reporting normal olfaction did indeed have normal olfaction, whereas 91% of these reporting no olfaction were anosmic.

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Kazuo Mizoi, Takashi Yoshimoto, Akira Takahashi and Akira Ogawa

✓ In the surgical treatment of basilar trunk aneurysms, there is still considerable technical difficulty in gaining both proximal artery control and a sufficient operative field. The authors describe their experience in five patients with basilar trunk aneurysms treated using temporary balloon occlusion and intraoperative digital subtraction angiography. With the patient under general anesthesia, a heparinized angiography catheter was guided into the dominant vertebral artery by means of the Seldinger technique. A silicone balloon catheter was introduced coaxially through the angiography catheter to the basilar artery just proximal to the aneurysm. The balloon was inflated tentatively to evaluate the appropriate inflation volume, then the balloon catheter was withdrawn back into the angiography catheter to prevent thrombus formation. After exposure of the aneurysm, the occlusion balloon was advanced again and inflated temporarily within the basilar artery to prevent premature rupture and to facilitate dissection of the aneurysm. The mean duration of temporary balloon occlusion was 22 minutes. There were no patients with postoperative deficits attributable to the temporary occlusion. The results of aneurysm clip placement were confirmed by intraoperative digital subtraction angiography immediately after clipping. No patient suffered from distal embolism or other complications related to vessel catheterization. From this experience, it is concluded that this intraoperative endovascular technique can contribute to the success of surgery for complex cerebral aneurysms, particularly for basilar trunk aneurysms in which proximal vascular control is difficult.

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Jiro Suzuki, Akira Takahashi, Takashi Yoshimoto and Hirobumi Seki

✓ The successful resection of a large posterior fossa arteriovenous malformation (AVM) is reported. A balloon catheter was used for temporary intraoperative occlusion of the basilar artery and feeding vessels of the AVM. Prior to occlusion of these arteries, newly tested substances to protect the ischemic brain were administered to prolong occlusion time. Resection of the AVM was completed without complication, and the patient returned to normal life. This is a useful intraoperative procedure for the resection of AVM's considered inoperable by conventional approaches.

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Jiro Suzuki, Takashi Yoshimoto and Takamasa Kayama

✓ The authors report their experience with the surgical therapy of middle cerebral artery (MCA) aneurysms in 413 cases, and describe their technique. After the M1 portion of the MCA is identified, the Sylvian fissure is opened. During the administration of 20% mannitol, temporary occluding clips are applied to the feeding and draining vessels of the aneurysm. The aneurysm is freed from all surrounding tissue, and the aneurysm neck is treated by ligation, clipping, or wrapping. Analysis of surgical results in 91 cases operated on after the surgical approach had become standardized indicates that more than 94% of patients have returned to useful social lives by the time of follow-up evaluation. Twenty-four percent of these patients were operated on within 48 hours after subarachnoid hemorrhage.

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Takamasa Kayama, Takashi Yoshimoto, Shunichi Fujimoto and Yoshiharu Sakurai

✓ Oxygen pressure (pO2) in brain tumors, pO2 in brain cortex surrounding the tumors, and PaO2 were measured simultaneously during total resection in 16 patients with previously untreated brain tumors in order to detect hypoxic regions within the tumors. When the inhaled O2:N2O ratio was 1:3 under enflurane anesthesia, mean PaO2 was 109.2 ± 5.8 mm Hg, a rather high value when compared with that obtained when air is inhaled under atmospheric pressure. The simultaneously measured intratumoral pO2 and pO2 in brain cortex surrounding the tumor were 15.3 ± 2.3 and 59.8 ± 6.5 mm Hg, respectively. Each intratumoral pO2 value was significantly lower than that of pO2 in brain cortex surrounding the tumor (mean < 30 mm Hg, Wilcoxon signed rank test, p < 0.005) and influenced the oxygen effects on radiation. These results appear to confirm that there are hypoxic regions within human brain tumors. A comparison between intratumoral pO2 and either the angiographic or contrast-enhanced computerized tomography scans of the tumor vasculature disclosed no correlation.

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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.