✓ 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 The balloon was inflated tentatively to evaluate the appropriate inflation volume, then the balloon catheter was withdrawn back into the angiography catheter to prevent thrombus formation.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.
Kazuo Mizoi, Takashi Yoshimoto, Akira Takahashi and Akira Ogawa
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.
Takashi Inoue, Yasutaka Kuzu, Kuniaki Ogasawara and Akira Ogawa
This study investigated the changes in the valve pressure setting of several magnetic pressure-programmable valves after exposure to a 3-tesla magnetic field.
Five each of four types of pressure-programmable shunt valves were tested: Sophy Polaris, Sophy SM8, Codman-Hakim, and Medtronic Strata. First, the valves were advanced toward the 3-tesla static magnetic field. Second, T1-, T2-, and diffusion-weighted magnetic resonance (MR) images were generated with a radiofrequency magnetic field. Any changes in the pressure setting were observed by visual inspection with a compass or radiography.
The pressure settings were changed after exposure to the static magnetic field in all programmable valves except for the Sophy Polaris. All pressure settings studied were unchanged after exposure to both static and radiofrequency magnetic fields (T1-, T2-, and diffusion-weighted MR imaging) in the Sophy Polaris.
The Sophy Polaris valve allows shunt-dependent patients who need a programmable valve to undergo 3-tesla MR imaging.
Akira Kudo, Michiyasu Suzuki, Naohiko Kubo, Kiyoshi Kuroda, Akira Ogawa and Yuzo Iwasaki
✓ This 35-year-old man presented with left facial spasm that had persisted for 10 months. Microvascular decompression was performed to relieve the symptom. No responsible vessel could be identified during surgery, but a small mass seeming to arise from the intermediate nerve and compressing the seventh cranial nerve was removed. The histological diagnosis was Antoni-B type schwannoma. This unique case of schwannoma arising from the intermediate nerve was recognized by means of an operative microscope, and supports the idea that portions of the seventh nerve schwannoma originate from the components of the intermediate nerve.
Tomoko Kobayashi, Akira Ogawa, Motonobu Kameyama, Hiroshi Uenohara and Takashi Yoshimoto
✓ A unique case is reported of Chiari malformation and compression of the medulla oblongata by both vertebral arteries. A 39-year-old woman complained of unsteady gait and motor weakness of the legs, and magnetic resonance imaging revealed the malformation and compression. Vascular decompression of the vertebral arteries was performed using synthetic (Gore-tex) vascular strips following posterior fossa decompression.
Hiroshi Kashimura, Kuniaki Ogasawara, Yoshitaka Kubo, Yasunari Otawara and Akira Ogawa
✓ A technique is described for removing previously placed aneurysm clips and applying new aneurysm clips for the treatment of regrown or reruptured cerebral aneurysms in patients more than 10 years after the original clipping of the aneurysm neck. The adherent tissue covering previously placed clips is cut just on and alongside the clips themselves using a small scalpel. Using the clip applicator, gentle pressure is applied to open the clip blade as little as possible. The aneurysm clip is carefully slid out along the line where the clip blade has resided, and a new aneurysm clip is applied. The procedure was successfully accomplished in four patients. Whereas three of these patients had an uneventful postoperative course, the remaining patient experienced transient right oculomotor nerve palsy and left-sided motor weakness. The present technique is a useful procedure for treatment of regrown or reruptured cerebral aneurysms occurring a significantly long time after initial clipping of an aneurysm neck.
Takashi Yoshimoto, Akira Ogawa, Hirobumi Seki, Tetsuo Kogure and Jiro Suzuki
✓ Knowledge of the natural course of stroke patients has become increasingly important since new therapeutic methods have been proposed for patients with cerebral infarction in the acute stage. In order to clarify the acute stage of this disease, 188 patients admitted within 24 hours after onset of middle cerebral artery (MCA) occlusion were followed for 2 months, and data relating to mortality and changes in disturbances of consciousness and motor function were investigated. It was shown that the prognosis for MCA occlusion cases is poor, and about 80% of these patients are unable to return to their previous lifestyle. The level of consciousness in the acute stage is a good index for estimating the patient's quality and time of survival, and motor function in the acute stage is a good indicator of functional recovery. Thus, when evaluating the effectiveness of a new therapy for cerebral infarction, rapid improvement in the acute stage before and after treatment should be carefully noted.
Hideki Matsuura, Takashi Inoue, Hiromu Konno, Makoto Sasaki, Kuniaki Ogasawara and Akira Ogawa
✓ Although various biomaterials such as ceramics or titanium alloy are widely used in neurosurgery, the susceptibility artifacts that appear around these materials cause problems when a magnetic resonance (MR) imager is used to assess lesions after surgery. The purpose of the present study was to quantify the susceptibility artifacts produced by various biomaterials used for neurosurgical implants.
Using a 3-tesla MR imaging unit, we obtained MR images of various biomaterials, including six types of ceramics, a cobalt-based alloy (Elgiloy), pure titanium, a titanium alloy, and stainless steel. All implants shared a uniform size and shape. In each image, a linear region of interest was defined across the center of the biomaterial in the transverse direction, and the diameter of the susceptibility artifact was calculated.
The ceramics produced a considerably smaller artifact diameter than those produced by other biomaterials. Among the types of ceramics, zirconia was found to produce the smallest artifact diameter. Among the remaining biomaterials, the diameters of the artifacts decreased in order from that associated with stainless steel to those associated with cobalt-based alloys, pure titanium, and titanium alloy. Little difference was observed between the artifact diameters associated with pure titanium and titanium alloy.
Ceramics are the most suitable biomaterials for minimizing artifacts in high-field MR imaging.
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.
A study of 38 cases
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.