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Kenzoh Yada, Yoku Nakagawa and Mitsuo Tsuru

✓ The venous drainage system during increased intracranial pressure (ICP) was studied in dogs. The ICP was gradually increased to the level of the systemic blood pressure while related arterial and venous pressures were monitored. The blood flow through the parasagittal intradural venous channels (lateral lacuna) was also measured to test the collapsibility of these vessels. The cortical venous pressure was constantly 50 to 200 mm H2O higher than the ICP regardless of the degree of elevation, while the sagittal sinus pressure remained at 50 to 75 mm H2O unless the central venous pressure was elevated by respiratory disturbance. Flow through the lateral lacuna decreased as the ICP was increased. The authors conclude that the low pressure in the sinus and the consistency of the walls of the lateral lacuna allow gradual stenosis of the lacuna during increased ICP.

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Yoku Nakagawa, Mitsuo Tsuru and Kenzoh Yada

✓ The pressure gradient of the venous pathway between the cortical vein and superior sagittal sinus was measured in adult mongrel dogs by recording the pressures of the bridging vein, lateral lacuna (proximal portion), and superior sagittal sinus, together with the systemic blood pressure while gradually increasing the intracranial pressure up to the level of mean systemic blood pressure. The pressure gradient between the lateral lacuna and the superior sagittal sinus was also measured under increased intracranial pressure. Pressures of the bridging vein and lateral lacuna were constantly 50 to 250 mm H2O higher than the intracranial pressure, regardless of the level of intracranial pressure. An abrupt drop in the intraluminal pressure was observed at a point 1 to 2 mm proximal to the junction of the lateral lacuna and the superior sagittal sinus, regardless of the level of intracranial pressure. It is concluded that gradual stenosis of the parasagittal venous pathways took place 1 to 2 mm proximal to the junction between the lacuna and the superior sagittal sinus, and thus cortical venous pressure was maintained 50 to 250 mm H2O higher than intracranial pressure. The authors believe that an “intracranial venous pressure regulation mechanism” exists at the junction of the lateral lacuna and the superior sagittal sinus.

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Yoku Nakagawa, Mineo Motomiya, Mitsuo Tsuru, Mitsue Bando and Makiko Tabata

✓ Destructive stereotaxic lesions were made in the posterior hypothalamus, unilaterally or bilaterally, in 26 dogs. In 21 dogs the intracranial pressure (ICP) was maintained in normal range, and in five dogs the ICP was artificially elevated to 300 to 400 mm H2O, preceding the procedures to the hypothalamus. Arterial oxygen and carbon dioxide pressure (PaO2 and PaCO2) were maintained in the normal range. Before and after each procedure, systemic arterial pressure (SAP) was elevated by intravenous injection of norepinephrine (5 × 10−3 mg/kg) to determine whether the ICP increases coincidentally with elevation of the systemic arterial pressure. The intracranial pressure/mean arterial pressure ratio of elevation by injection of norepinephrine was not significant regardless of the level of the ICP, or of uni- or bilateral lesions of the hypothalamus. The authors conclude that dysfunction of posterior hypothalamus does not play a specific role in the development of vasomotor paralysis leading to acute brain swelling, under conditions of normal or moderately raised ICP with normal PaCO2 and PaO2 levels.

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Yoku Nakagawa, Kunio Tashiro, Toyohiko Isu and Mitsuo Tsuru

✓ A case of cerebral metastasis of chorioepithelioma with an occlusion of the angular artery is presented. The occlusion was verified angiographically, surgically, and microscopically.

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Kazuo Miyasaka, Hidetoshi Takei, Mikio Nomura, Sinji Sugimoto, Toshimitsu Aida, Hiroshi Abe and Mitsuo Tsuru

✓ Changes in the brain parenchyma and cerebrospinal fluid spaces were demonstrated in three cases of dural arteriovenous malformations by computerized tomography (CT). In various combinations, there were 1) vermiform or patchy enhancement after intravenous contrast infusion, 2) abnormal decreased density mainly in the white matter, 3) local mass effect, 4) hydrocephalus, 5) dilatation of the major venous sinus system, and 6) prominent vascular grooving of the skull inner table. Most of these changes were secondary to raised sinus pressure caused by arteriovenous shunt. It was also demonstrated by serial CT that some elements improved after artificial embolization or surgical excision of the malformations.

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Hiroshi Abe, Mitsuo Tsuru, Terufumi Ito, Yoshinobu Iwasaki and Mitsuyuki Koiwa

✓ Anterior decompression and fusion for treating ossification of the posterior longitudinal ligament of the cervical spine was performed in 12 patients. The central part of the vertebral body and the ossified area of the posterior longitudinal ligament were removed by means of a microrongeur and an air drill. The defect was filled with a long bone graft taken from the ilium. The operative results were excellent. Marked improvement of radicular and spinal cord signs was seen in all 12 cases. Three vertebral bodies were fused in one case, four in nine cases, and five in two cases. The highest level of fusion was C-2 and the lowest was T-1. It is considered that any ossification of the ligament below the C-2 level can be removed via an anterior approach as long as no more than five vertebral bodies are involved. Spinal computerized tomography was valuable in providing more detailed information about the stenotic spinal canal and the shape of the ossified ligament.

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Toyohiko Isu, Kazuo Miyasaka, Hiroshi Abe, Terufumi Ito, Yoshinobu Iwasaki, Mitsuo Tsuru, Kenichi Kitaoka and Minoru Tsunoda

✓ Atlantoaxial dislocation was found in three patients with neurofibromatosis. Roentgenographic findings included marked reduction of sagittal diameter at the C-1 vertebral level, and cervical spine abnormalities associated with mesodermal dysplasia, such as posterior scalloping of the cervical spinal bodies with dural ectasia and vertebral body deformity (vertebral body dysplasia). Although the relationship of the atlas and axis did not change with neck position, all three patients had progressive neurological deficits and were treated by decompressive surgery combined with fusion. The pathogenesis of atlantoaxial dislocation associated with neurofibromatosis is discussed.

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Yoshinobu Iwasaki, Minoru Akino, Hiroshi Abe, Mitsuo Tsuru, Kunio Tashiro, Kazuo Miyasaka, Kiyoshi Kaneda, Toyohiko Isu and Terufumi Ito

✓ Four cases of calcification of the cervical ligamentum flavum are reported, all in women over 60 years of age. Neurological findings were not significantly different from those of other cervical compressive diseases. Among radiological examinations, computerized tomography was the most valuable diagnostic tool. Calcification might have been induced by the degeneration or abnormal nutritional state of the ligamentum flavum. Endocrine abnormalities and inflammatory processes might also have been contributory factors.