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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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Wataru Yanagihara, Kohei Chida, Masakazu Kobayashi, Yoshitaka Kubo, Kenji Yoshida, Kazunori Terasaki, and Kuniaki Ogasawara

OBJECTIVE

Some adult patients with moyamoya disease (MMD) undergoing revascularization surgery show an improvement or decline in cognition postoperatively. Revascularization surgery for ischemic MMD augments cerebral blood flow (CBF) and improves cerebral oxygen metabolism. However, cerebral hyperperfusion, which is a short-term, major increase in ipsilateral CBF that is much greater than the metabolic needs of the brain, sometimes occurs as a complication. Cerebral hyperperfusion produces widespread, minimal injury to the ipsilateral white matter and cortical regions. The aim of the present prospective study was to determine how changes in CBF due to arterial bypass surgery affect cognitive function in adult patients with symptomatic ischemic MMD and misery perfusion.

METHODS

Thirty-two patients with cerebral misery perfusion, as determined on the basis of 15O gas positron emission tomography, underwent single superficial temporal artery–middle cerebral artery (M4 in the precentral region) anastomosis. Brain perfusion single-photon emission computed tomography (SPECT) studies were performed preoperatively, on the 1st postoperative day, and 2 months after surgery. Neuropsychological tests were also performed preoperatively and 2 months after surgery.

RESULTS

Postoperative neuropsychological assessments demonstrated cognitive improvement in 10 cases (31%), no change in 8 cases (25%), and decline in 14 cases (44%). Based on brain perfusion SPECT and symptoms, 10 patients were considered to have cerebral hyperperfusion syndrome, and all of these patients exhibited a postoperative decline in cognition. Relative precentral CBF on the 1st postoperative day was significantly greater in patients with postoperative cognitive decline (167.3% ± 15.3%) than in those with improved (105.3% ± 18.2%; p < 0.0001) or unchanged (131.4% ± 32.1%; p = 0.0029) cognition. The difference between relative precentral CBF 2 months after surgery and that before surgery was significantly greater in patients with postoperative cognitive improvement (17.2% ± 3.8%) than in those with no postoperative change (10.1% ± 2.4%; p = 0.0003) or with postoperative decline (11.5% ± 3.2%; p = 0.0009) in cognition.

CONCLUSIONS

Cerebral hyperperfusion in the acute stage after arterial bypass surgery impairs cognitive function. An increase in CBF in the chronic stage without acute-stage cerebral hyperperfusion improves cognitive function in adult patients with symptomatic ischemic MMD and misery perfusion.

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Yasunari Otawara, Kuniaki Ogasawara, Hiroshi Kashimura, Yoshitaka Kubo, Akira Ogawa, and Kouichi Watanabe

The mechanical properties of titanium-alloy aneurysm clips after long-term implantation in the human cranium are unclear. The characteristics of a Yasargil titanium aneurysm clip were evaluated after long-term implantation for 12 years in a patient with a cerebral aneurysm. The closing forces of the retrieved clip before and after implantation were approximately equal. The bending test showed no differences between the retrieved and control clips. Titanium oxide and calcium were identified on the surface of the retrieved clip, which indicated the formation of corrosion-resistant layers. Titanium-alloy clips retain their mechanical properties in the human cranium for a long time.

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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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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.

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Kuniaki Ogasawara, Keiko Yamadate, Masakazu Kobayashi, Hidehiko Endo, Takeshi Fukuda, Kenji Yoshida, Kazunori Terasaki, Takashi Inoue, and Akira Ogawa

Object. Cognitive impairment occurs in 20 to 30% of patients following carotid endarterectomy (CEA). The purpose of the present study was to determine whether postoperative cerebral hyperperfusion is associated with impairment of cognitive function in patients undergoing that procedure.

Methods. Cerebral blood flow (CBF) was measured using single-photon emission computerized tomography scanning before and immediately after CEA and on the 3rd postoperative day in 92 patients with ipsilateral internal carotid artery stenosis of 70% or greater. Hyperperfusion post-CEA was defined as a 100% increase or greater in CBF compared with preoperative values. Neuropsychological testing was also performed preoperatively and at the 1-, 3-, and 6-month follow-up examinations.

At the 1-month postoperative neuropsychological assessment, 11 patients (12%) displayed evidence of cognitive impairment. In addition, the incidence of postoperative cognitive impairment in patients with post-CEA hyperperfusion (seven [58%] of 12 patients) was significantly higher than that in patients without post-CEA hyperperfusion (four [5%] of 80 patients; p < 0.0001). A logistic regression analysis demonstrated that post-CEA hyperperfusion was the only significant independent predictor of postoperative cognitive impairment. Of the seven patients in whom post-CEA hyperperfusion and cognitive impairment were identified 1 month postoperatively, four (including three patients with hyperperfusion syndrome) remained cognitively impaired at the 3- and 6-month follow-up examinations.

Conclusions. Postoperative cerebral hyperperfusion is associated with impairment of cognitive function in patients undergoing CEA. Furthermore, the development of hyperperfusion syndrome is associated with the persistence of postoperative cognitive impairment.

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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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Yoshitaka Kubo, Takahiro Koji, Hiroshi Kashimura, Yasunari Otawara, Akira Ogawa, and Kuniaki Ogasawara

Object

The prevalence of patients with asymptomatic unruptured intracranial aneurysms (UIAs) increases with the advancing age of the general population. The goal of the present study was to identify risk factors for the growth of UIAs detected with serial MR angiography (MRA) in patients 70 years of age or older.

Methods

This prospective study enrolled 79 patients (age range 70–84 years) with 98 UIAs. Patients were followed up every 4 months, including an assessment of the aneurysm diameter and morphological changes on MRA, neurological status, and other medical conditions. Aneurysm growth was categorized into two different patterns on the basis of the MRA findings: 1) maximum increase in aneurysm diameter of 2 mm or more; and 2) obvious morphological change, such as the appearance of a bleb.

Results

The mean duration of follow-up was 38.5 months (250.2 patient-years). Aneurysm rupture did not occur, but aneurysm growth was observed in 8 aneurysms (8 patients) during the study period. Univariate analysis showed that female sex, patient age ≥ 75 years, and an aneurysm location in the internal carotid artery (ICA) or middle cerebral artery (MCA) were associated with aneurysm growth (p = 0.04, p = 0.04, and p < 0.001, respectively). Multivariate analysis demonstrated that female sex was the only independent predictor of aneurysm growth (p = 0.0313, OR 2.3, 95% CI 1.3–30.2).

Conclusions

Female sex is an independent risk factor for the growth of UIAs in elderly patients. In addition, an age ≥ 75 years and aneurysm location in the ICA or MCA are characteristics that may warrant additional attention during follow-up imaging.