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Akira Watanabe, Ryuichi Tanaka, Norio Takeda and Kazuo Washiyama

✓ The relationships between distribution of deoxyribonucleic acid (DNA)-synthesizing cells (S-phase cells) and blood flow and glucose utilization were investigated in rat brain tumors using an autoradiographic technique and immunoperoxidase staining for bromodeoxyuridine (BUdR). Two strains of rat brain tumor were used: strain A and B, both induced by the Rous sarcoma virus. Strain A was biologically more malignant than strain B. The blood flow was unevenly distributed in the tumor; compared with the contralateral cortex, the average blood flow in the tumor was about 50% in strain A and 60% in strain B. The distribution of blood flow did not correlate with the distribution of S-phase cells or with the distribution of vessels in the tumor in either strain A or B. The average glucose utilization in strain A was about 250% and in strain B about 170% of that of the contralateral cortex. The high glucose utilization area correlated well with the distribution of BUdR-positive nuclei in strain B. These findings suggest that the biological malignancy of a tumor correlates with glucose utilization rather than with blood flow, and that malignant brain tumors show a marked increase in glucose utilization for nucleic acid synthesis.

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Hidetoshi Ikeda, Takehiko Abe and Kazuo Watanabe

Object

Fifty to eighty percent of Cushing disease is diagnosed by typical endocrine responses. Recently, the number of diagnoses of Cushing disease without typical Cushing syndrome has been increasing; therefore, improving ways to determine the localization of the adenoma and making an early diagnosis is important. This study was undertaken to determine the present diagnostic accuracy for Cushing microadenoma and to compare the differences in diagnostic accuracy between MR imaging and PET/MR imaging.

Methods

During the past 3 years the authors analyzed the diagnostic accuracy in a series of 35 patients with Cushing adenoma that was verified by surgical pituitary exploration. All 35 cases of Cushing disease, including 20 cases of “overt” and 15 cases of “preclinical” Cushing disease, were studied. Superconductive MR images (1.5 or 3.0 T) and composite images from FDG-PET or methionine (MET)–PET and 3.0-T MR imaging were compared with the localization of adenomas verified by surgery.

Results

The diagnostic accuracy of superconductive MR imaging for detecting the localization of Cushing microadenoma was only 40%. The causes of unsatisfactory results for superconductive MR imaging were false-negative results (10 cases), false-positive results (6 cases), and instances of double pituitary adenomas (3 cases). In contrast, the accuracy of microadenoma localization using MET-PET/3.0-T MR imaging was 100% and that of FDG-PET/3.0-T MR imaging was 73%. Moreover, the adenoma location was better delineated on MET-PET/MR images than on FDG-PET/MR images. There was no significant difference in maximum standard uptake value of adenomas evaluated by MET-PET between preclinical Cushing disease and overt Cushing disease.

Conclusions

Composite MET-PET/3.0-T MR imaging is useful for the improvement of the delineation of Cushing microadenoma and offers high-quality detectability for early-stage Cushing adenoma.

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Taku Sugawara, Naoki Higashiyama, Shuichi Kaneyama, Masato Takabatake, Naoko Watanabe, Fujio Uchida, Masatoshi Sumi and Kazuo Mizoi

Object

Pedicle screw fixation is a standard procedure of spinal instrumentation, but accurate screw placement is essential to avoid injury to the adjacent structures, such as the vessels, nerves, and viscera. The authors recently developed an intraoperative screw guiding method in which patient-specific laminar templates were used, and verified the accuracy of the multistep procedure in the thoracic spine.

Methods

Preoperative bone images of the CT scans were analyzed using 3D/multiplanar imaging software and the trajectories of the screws were planned. Plastic templates with screw guiding structures were created for each lamina by using 3D design and printing technology. Three types of templates were made for precise multistep guidance, and all templates were specially designed to fit and lock on the lamina during the procedure. Plastic vertebra models were also generated and preoperative screw insertion simulation was performed. Surgery was performed using this patient-specific screw guide template system, and the placement of screws was postoperatively evaluated using CT scanning.

Results

Ten patients with thoracic or cervicothoracic pathological entities were selected to verify this novel procedure. Fifty-eight pedicle screws were placed using the screw guide template system. Preoperatively, each template was found to fit exactly and to lock on the lamina of the vertebra models, and screw insertion simulation was successfully performed. Intraoperatively the templates also fit and locked on the patient lamina, and screw insertion was completed successfully. Postoperative CT scans confirmed that no screws violated the cortex of the pedicles, and the mean deviation of the screws from the planned trajectories was 0.87 ± 0.34 mm at the coronal midpoint section of the pedicles.

Conclusions

The multistep, patient-specific screw guide template system is useful for intraoperative pedicle screw navigation in the thoracic spine. This simple and economical method can improve the accuracy of pedicle screw insertion and reduce the operating time and radiation exposure of spinal fixation surgery.

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Shin-ichi Tsubaki, Takanori Fukushima, Teruaki Tamagawa, Shin-ichiro Miyazaki, Kazuo Watanabe, Nobumasa Kuwana and Tsuneo Shimizu

✓ Posterior fossa microvascular decompression surgery was attempted in 1257 patients with trigeminal neuralgia (TN), of whom seven had a very unusual cryptic angioma. The lesions were not visualized on preoperative enhanced computerized tomography scans, and serial angiography demonstrated a small vascular stain in only one case. The character of the facial pain was indistinguishable from TN caused by vascular compression and there was no other specific symptomatology. The patients' age and sex distributions were also compatible with classical TN. Cryptic angiomas presenting as typical TN without other symptoms have not been reported before, but they should be kept in mind in the differential diagnosis and surgical management of TN.

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Sumito Okuyama, Shinjitsu Nishimura, Yoshiharu Takahashi, Keiichi Kubota, Takayuki Hirano, Ken Kazama, Masato Tomii, Junko Matsuyama, Junichi Mizuno, Tadao Matsushima, Masataka Sato and Kazuo Watanabe

OBJECTIVE

Hypoperfusion during carotid artery cross-clamping (CC) for carotid endarterectomy (CEA) may result in the major complication of perioperative stroke. Median nerve somatosensory evoked potential (MNSSEP) monitoring, which is an established method for the prediction of cerebral ischemia, has low sensitivity in detecting such hypoperfusion. In this study the authors sought to explore the limitations of MNSSEP monitoring compared to tibial nerve somatosensory evoked potential (TNSSEP) monitoring for the detection of CC-related hypoperfusion.

METHODS

The authors retrospectively analyzed data from patients who underwent unilateral CEA with routine shunt use. All patients underwent preoperative magnetic resonance angiography and were monitored for intraoperative cerebral ischemia by using MNSSEP, TNSSEP, and carotid stump pressure during CC. First, the frequency of MNSSEP and TNSSEP changes during CC were analyzed. Subsequently, variables related to stump pressure were determined by using linear analysis and those related to each of the somatosensory evoked potential (SSEP) changes were determined by using logistic regression analysis.

RESULTS

A total of 94 patients (mean age 74 years) were included in the study. TNSSEP identified a greater number of SSEP changes during CC than MNSSEP (20.2% vs 11.7%; p < 0.05). Linear regression analysis demonstrated that hypoplasia of the contralateral proximal segment of the anterior cerebral artery (A1 hypoplasia) (p < 0.01) and hypoplasia of the ipsilateral precommunicating segment of the posterior cerebral artery (P1 hypoplasia) (p = 0.02) independently and negatively correlated with stump pressure. Both contralateral A1 hypoplasia (OR 26.25, 95% CI 4.52–152.51) and ipsilateral P1 hypoplasia (OR 8.75, 95% CI 1.83–41.94) were independently related to the TNSSEP changes. However, only ipsilateral P1 hypoplasia (OR 8.76, 95% CI 1.61–47.67) was independently related to MNSSEP changes.

CONCLUSIONS

TNSSEP monitoring appears to be superior to MNSSEP in detecting CC-related hypoperfusion. Correlation with stump pressure and SSEP changes indicates that TNSSEP, and not MNSSEP monitoring, is a reliable indicator of cerebral ischemia in the territory of the anterior cerebral artery.