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Yuji Tsurumi, Motonobu Kameyama, Kiichi Ishiwata, Ryuichi Katakura, Minoru Monma, Tatsuo Ido and Jiro Suzuki

✓ The value of 18F-fluoro-2′-deoxyuridine (18F-FUdR) as a tracer for nucleic acid metabolism was studied using an experimental rat brain-tumor model. The 18F activity in the tumor tissue 45 minutes after intravenous injection of 18F-FUdR was about 12 times higher than that in the contralateral cortex. Double-labeled autoradiography with 18F-FUdR and 14C-thymidine revealed similar brain-tumor images. In contrast, an autoradiographic comparison of 18F-FUdR with 14C-aminoisobutyric acid, which reveals the impairment of the blood-brain barrier, showed very different images. Also, the 18F radioactivity in the tumor tissue was at a constant level for 30 to 120 minutes, whereas a notable increase in 18F activity with time was observed in nucleotides and acid-insoluble fractions. These results suggest that the distribution pattern of 18F-FUdR closely correlates with the metabolism of nucleic acid and that this drug could be a useful tracer for positron emission tomography.

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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.

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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.

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Takehide Onuma, Yasuko Shimosegawa, Motonobu Kameyama, Hiroaki Arai and Kiyoshi Ishii

✓ The authors have treated five cases of severe head trauma in children in which abnormally high density along gyri, “gyral high density,” was seen on plain computerized tomography (CT) scans in the subacute stage of the injury. The prognosis in all cases was poor, with either severe disability or a vegetative state as the outcome due to significant brain atrophy following gyral high density. This pathology was classified into three clinical stages: 1) acute stage, cerebral ischemia in which there is diffuse low density of the cerebrum on CT scans (most marked on the 3rd and 4th days); 2) subacute stage, hemorrhagic infarction showing gyral high density on plain CT scans (between 1 and 4 weeks); and 3) chronic stage, brain atrophy (beginning 4 weeks after the trauma).

In their consecutive series of head-injured patients (516 children, 1459 adults), the authors did not find gyral high density on CT scan in adults. This is probably due to the fact that adults who suffer the severe head trauma associated with diffuse brain swelling or diffuse brain edema cannot survive, thus making this gyral high density unique to children.