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  • Author or Editor: Kuniaki Ogasawara x
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Takashi Inoue, Yasutaka Kuzu, Kuniaki Ogasawara and Akira Ogawa

Object

This study investigated the changes in the valve pressure setting of several magnetic pressure-programmable valves after exposure to a 3-tesla magnetic field.

Methods

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.

Conclusions

The Sophy Polaris valve allows shunt-dependent patients who need a programmable valve to undergo 3-tesla MR imaging.

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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.

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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.

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Yoshitaka Kubo, Kuniaki Ogasawara, Akira Kurose, Shunsuke Kakino, Nobuhiko Tomitsuka and Akira Ogawa

Although aortic or cardiac complications are common in patients with Marfan syndrome, the presence of an intracranial aneurysm is comparatively rare. In this study, the authors report on their experience with resection of a ruptured fusiform aneurysm of the posterior cerebral artery in a 30-year-old woman with Marfan syndrome. Microscopic examination of the resected tissue showed many Alcian blue–staining deposits, consistent with the presence of mucopolysaccharide in the tunica media and focal fragmentation of the internal elastic lamina.

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Kuniaki Ogasawara, Hirotsugu Yukawa, Masakazu Kobayashi, Chiaki Mikami, Hiromu Konno, Kazunori Terasaki, Takashi Inoue and Akira Ogawa

Object. The purpose of this study was to determine whether the preoperative measurement of acetazolamide-induced changes in cerebral blood flow (CBF), which is performed using single-photon emission computerized tomography (SPECT) scanning, can be used to identify patients at risk for hyperperfusion following carotid endarterectomy (CEA). In addition, the authors investigated whether monitoring of CBF with SPECT scanning after CEA can be used to identify patients at risk for hyperperfusion syndrome.

Methods. Cerebral blood flow and cerebrovascular reactivity (CVR) to acetazolamide were measured before CEA in 51 patients with ipsilateral internal carotid artery stenosis (≥ 70% stenosis). Cerebral blood flow was also measured immediately after CEA and on the 3rd postoperative day.

Hyperperfusion (an increase in CBF of ≥ 100% compared with preoperative values) was observed immediately after CEA in eight of 12 patients with reduced preoperative CVR. Reduced preoperative CVR was the only significant independent predictor of post-CEA hyperperfusion. Forty-three patients in whom hyperperfusion was not detected immediately after CEA did not exhibit hyperperfusion on the 3rd postoperative day and did not experience hyperperfusion syndrome. In two of eight patients in whom hyperperfusion occurred immediately after CEA, CBF progressively increased and hyperperfusion syndrome developed, but intracerebral hemorrhage did not occur. In the remaining six of eight patients in whom hyperperfusion was detected immediately after CEA, the CBF progressively decreased and the hyperperfusion resolved by the 3rd postoperative day.

Conclusions. Preoperative measurement of acetazolamide-induced changes in CBF, which is performed using SPECT scanning, can be used to identify patients at risk for hyperperfusion after CEA. In addition, post-CEA monitoring of CBF performed using SPECT scanning results in the timely and reliable identification of patients at risk for hyperperfusion syndrome.

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Kenji Yoshida, Kuniaki Ogasawara, Masakazu Kobayashi, Junichi Tsuboi, Hitoshi Okabayashi and Akira Ogawa

Object

Scar formation in the carotid sheath is often identified during carotid endarterectomy (CEA) in patients with previous cardiac surgery, and dissection of the carotid sheath and exposure of the carotid arteries in such patients are difficult. The purpose of the present study was to investigate factors related to scar formation identified during CEA in patients with previous cardiac surgery.

Methods

Twenty-three patients with internal carotid artery stenosis (≥ 70%) and previous cardiac surgery underwent CEA. A patient was prospectively defined as having scar formation during CEA when scissors were required throughout dissection of the carotid sheath and exposure of the carotid arteries.

Results

Scar formation was identified during dissection of the carotid sheath in 7 patients (30.4%). In all 7 patients, the side of CEA was identical to the side on which the Swan-Ganz catheter was inserted during cardiac surgery, and the incidence of previous ipsilateral Swan-Ganz catheter insertion was significantly higher in patients with the scar formation (100%) than in those without (31.3%). Seven (58.3%) of 12 patients with a history of ipsilateral Swan-Ganz catheter insertion had scar formation. Two of the 7 patients with scar formation experienced complications after CEA, including one patient with hemiparesis due to artery-to-artery embolism during surgery, and another patient with transient vocal cord paralysis.

Conclusions

A history of Swan-Ganz catheter insertion during previous cardiac surgery is associated with the presence of scar tissue in the ipsilateral carotid sheath and a higher risk of complications during CEA.

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Takaaki Beppu, Yuichi Sato, Noriyuki Uesugi, Yasutaka Kuzu, Kuniaki Ogasawara and Akira Ogawa

✓A desmoplastic infantile astrocytoma (DIA) is an extremely rare tumor that comprises a solid astrocytic tumor accompanied by a large cyst and involves the superficial cerebral cortex and leptomeninges in infants. The solid part of this type of tumor has been well described in various reports and books, but characteristics of the cystic portion have remained unclear. Because adequate resection is required to ensure a favorable prognosis, information about the cyst is very important for diagnostic purposes and surgical planning. The authors report on the clinical and histological features of the cyst in a case of a DIA. A 12-month-old boy presented with vomiting. Contrast-enhanced magnetic resonance imaging revealed a strongly enhancing single-lobed large cyst located in the deep white matter, under the solid part of the tumor attached to the dura mater of the left frontal lobe. Both the solid and cystic portions of the tumor were surgically removed. The border between the cyst wall and surrounding white matter was unclear. Histologically, the cyst wall was composed of gliosis representing a rough accumulation of reactive astrocytes, lymphocytes, and small capillary vessels in edematous parenchyma, but no tumor cells. The present case and previous reports suggest that the cyst does not contain tumor cells, even if strongly depicted on contrast-enhanced neuroimaging, and that a thickly enhancing cyst wall indicates gliosis with accumulation of numerous small vessels.

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Yasunari Otawara, Miguel M. Endo, Kuniaki Ogasawara, Yoshitaka Kubo, Akira Ogawa and Kouichi Watanabe

Object

Aneurysm clip reliability after long-term implantation in vivo has not been examined. In this study the authors evaluated the mechanical properties and surface elemental composition of Co-Cr alloy aneurysm clips implanted for more than 10 years in patients with cerebral aneurysms.

Methods

Five aneurysm clips implanted for ruptured or unruptured intracranial aneurysms were retrieved and examined. New aneurysm clips were applied to the regrown aneurysms. The implantation period ranged from 11 to 20 years. Four new and unused aneurysm clips were also examined as controls. The mechanical properties of the clips were tested by measuring their closing force and bending strength. The surface elemental composition of the aneurysm clips was evaluated using x-ray photoelectron spectroscopy. The closing force of the retrieved clips exceeded the minimum force requirement at the time of manufacture. The bending strength was similar between the retrieved and control clips. Chromium oxide was the predominant constituent on the surface of all clips, and its concentration on the retrieved clips was higher than that on the control clips.

Conclusions

Data in the present study demonstrated that Co-Cr alloy aneurysm clips retain their mechanical properties in vivo for a long time, which indicates the reliability of these clips.

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Yoshitaka Kubo, Kuniaki Ogasawara, Nobuhiko Tomitsuka, Yasunari Otawara, Mikio Watanabe and Akira Ogawa

✓ A technique combining wrapping and clip occlusion of aneurysms by using polytetrafluoroethylene (PTFE) for treatment of ruptured blisterlike aneurysms of the supraclinoid internal carotid artery (ICA) is described. The diameter of the abnormal arterial lesion along the long axis of the ICA and the distance between the origin of the ophthalmic artery and the origin of the posterior communicating artery (PCoA), or the origin of the PCoA and the origin of the anterior choroidal artery are measured intraoperatively; a strip of PTFE membrane is then trimmed with scissors to match this diameter and distance. After temporarily occluding the cervical ICA, the intracranial ICA that includes the lesion is wrapped with the strip of PTFE, and one or more aneurysm clips are applied parallel to the ICA. This procedure was successfully accomplished in six patients, all of whom had an uneventful postoperative course with no recurrent subarachnoid hemorrhage during the follow-up period. “Wrap-clipping” using PTFE is a useful procedure for management of ruptured blisterlike aneurysms of the ICA.

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Hiroshi Kashimura, Takashi Inoue, Kuniaki Ogasawara, Hiroshi Arai, Yasunari Otawara, Yoshiyuki Kanbara and Akira Ogawa

Object

Preoperative planning for meningiomas requires information about tumor consistency as well as location and size. In the present study the authors aimed to determine whether the fractional anisotropy (FA) value calculated on the basis of preoperative magnetic resonance (MR) diffusion tensor (DT) imaging could predict meningioma consistency.

Methods

In 29 patients with intracranial meningiomas, MR DT imaging was performed preoperatively, and the FA values of the tumors were calculated. Tumor consistency was intraoperatively determined as hard or soft, and the histological diagnosis of the tumor was established.

Results

Of the 29 tumors, 11 were classified as hard and 18 as soft. The FA values of fibroblastic meningiomas were significantly higher than those of meningothelial meningiomas (p = 0.002). The FA values of hard tumors were significantly higher than those of soft tumors (p = 0.0003). Logistic regression analysis demonstrated that the FA value was a significant independent predictor of tumor consistency (p = 0.007).

Conclusions

The FA value calculated from preoperative MR DT imaging predicts meningioma consistency.