Yasuhiro Yonekawa

Cerebral circulation and metabolism in adults' Moyamoya disease-PET study

SummaryRegional cerebral blood flow (rCBF), oxygen extraction fraction (rOEF), cerebral metabolic rate for oxygen (rCMRO2) and cerebral blood volume (rCBV) in nine cases of moyamoya disease in adults were studied with positron emission CT (PET) scan, using15O steady-state methods. Three cases showed ischaemic symptoms and the other six cases showed haemorrhagic symptoms. PET scan was performed during the chronic stage. Control data were obtained from eight normal volunteers. Regional cerebral blood flow and other physiological parameters in cerebral gray matter, white matter and basal ganglia were compared with normal controls.All nine cases of Moyamoya disease showed decreased rCBF, though not significant, in cerebral gray matter, white matter and basal ganglia. Reduction of rCBF was significant in the cerebral cortex of six haemorrhagic cases. This significant decrease was considered to be due to diaschisis and also brain atrophy caused by the cerebral haemorrhage. There was a significant increase in rCBV in white matter of the both ischaemic and haemorrhagic cases. The calculated value of CBF/CBV is considered to be an index of perfusion pressure. This value was significantly decreased in all three regions, though rOEF was not significantly increased in moyamoya disease. Hence the cerebral circulation in adults with moyamoya disease appears to be characterized by a mild decrease in perfusion pressure and prolonged circulated time.

Efficacy of a blood substitute (Fluosol-DA, 20%) on cerebral ischemia.

Fluosol-DA, 20%, was intravenously infused in 28 patients suffering from cerebrovascular disease, and was found to be effective in 60% of the cases with vasospasm and in 80% of the cases with stenosis and/or occlusion of the artery. Administration of the solution increases r-CBF by 10.1 to 37.9% when measured by either intra-arterial injection or inhalation of 133Xe. However, an increase of arterial oxygen tension appears to have little effect on r-CBF after administration of the solution. The increase of r-CBF caused by Fluosol-DA, 20%, may be due not only to the lowering viscosity of the mixed blood but also to its direct effect on dilating cerebral vessels.

Extent of thermal penetration of Nd-YAG laser--histological considerations.

SummaryThe extent of thermal penetration of Nd-YAG laser was studied histologically. The material was obtained from seven cases of various types of intracranial and extracranial tumours and normal temporal muscle obtained at operation. After irradiation of the tumour surface with the laser, the tumours were removed and depth and width of pathological changes caused by heat were studied. Histologically, materials consisted of a vaporized surface, carbonized, vesicular, necrotic, oedematous layers and surrounding intact brain tumour tissue. There was a direct relationship between the thermal effect and the irradiated thermal energy (watt × exposure time × pulse number). The results showed that the thermal effect was limited to a depth of 6 to 10 mm from the irradiated surface when irradiated 4 times at the power of 90 watts for 2 seconds.

Effects of a Transfusion with a Blood Substitute (Fluosol-DA, 20%) on Cerebral Circulation in the Monkey

Local cerebral blood flow (lCBF) and electroencephalogram were monitored in six monkeys after a transfusion using a perfluorochemical suspension (Fluosol-DA, 20%) that has been manufactured as a blood substitute and is known to be synthetic, biologically inert, and nontoxic and to have a high capacity for carrying oxygen. The animals were mechanically ventilated, and blood gases were maintained at physiological levels. Fluosol-DA, 20% was administered either by an exchange transfusion of 20 ml/kg or by an infusion of 8 ml/kg followed by an exchange transfusion of 12 ml/kg. lCBF was measured using the hydrogen clearance technique. An equation was proposed to estimate the tissue-blood partition coefficient of hydrogen; this coefficient is considered to be dependent upon the amount of perfluorochemicals in the blood and was used to calculate lCBF. Systemic blood pressure, pulse rate, central venous pressure, electroencephalogram, and gas analysis of the blood from the femoral artery, the femoral vein, and the superior sagittal sinus showed little change throughout the experiment. lCBF was increased by 12% (p less than 0.005) after the infusion of Fluosol-DA, 20% of 8 ml/kg and by 31% (p less than 0.02) after the exchange transfusion. Hyperventilation reduced lCBF significantly (p less than 0.005), which implies that the reactivity of the cerebral blood vessels to hypocarbia was not impaired by the administration of FLuosol-DA, 20%. Both the results of this study and the physical properties of Fluosol-DA, 20% suggest that this blood substitute can safely be used for normal human brains and that it might also be effective for ischemic brains.

Effects of a transfusion with a blood substitute (Fluosol-DA, 20%). Part II: Human cerebral blood flow.

In 24 patients suffering from cerebrovascular diseases, alteration of the cerebral blood flow was investigated by means of the 133Xe clearance technique before and after the intravenous infusion of perfluorochemical suspension (Fluosol-DA, 20%, 10 ml/kg). Since perfluorochemicals exhibit high solubilities for not only oxygen but other kinds of gases, the partition coefficient of Xe (lambda tb) is considered to change depending on the amount of perfluorochemicals contained in the blood (Fct). The solubilities of Xe in the perfluorochemicals contained in the solution were then measured by gas chromatography to obtain an equation for lambda tb: lambda tb = 1.50/(Hct/100 + 12.48Fct/100 + 0.95). The cerebral blood flow was found to increase significantly by 10.1% in the lesional hemisphere and by 10.8% in the healthy one. The cortical small artery with a diameter between 0.1 and 0.2 mm appeared to dilate by 13% after its administration. From these results, the decrease of blood viscosity and some vasodilating effect of the solution might be responsible for the increase of the cerebral blood flow.

Histologic study of normal rat brain tissue after neodymiumyttrium aluminum garnet laser irradiation. I. Cerebral hemisphere

We report a histologic study of normal rat brain tissue after neodymium-yttrium aluminum garnet laser irradiation. Morphological changes occurred at a maximum depth of 5 mm after 60-W, 1-second exposure, at a 2-mm distance between the optical fiber tip and the brain surface. Polymorphonuclear leukocyte infiltration into the irradiated area was observed 48 hours after irradiation. After 72 hours, macrophages and fibroblasts appeared; their number increased thereafter. At 1 month, tissue defects attributable to neodymium-yttrium aluminum garnet laser irradiation were small. Gliotic changes were rarely seen. We conclude that 60-W irradiation is harmful to young rats but not to adult rats.

Histologic changes in rat brain tissue caused by neodymium-yttrium aluminum garnet laser irradiation. II. cerebellum

Histologic changes after neodymium-yttrium aluminum garnet laser irradiation were evaluated in the rat cerebellum. Irradiation of 60 W (corresponds to 45.2 W/mm2) to the posterior fossa was dangerous even in adult rats, although this value was safe for the rat cerebral hemisphere as previously reported. The histologic changes caused by neodymium-yttrium aluminum garnet laser irradiation were similar to those caused by thermal energies. To the adult rat cerebellum, 45 W (35.2 W/mm2) can safely be applied. For the further use of the neodymium-yttrium aluminum garnet laser in neurosurgery, our findings should be taken into consideration.

Interventional Radiological Techniques in Cerebral AVMs

Though surgical removal is the best treatment of cerebral arteriovenous malformation (AVM), many AVMs located in the dominant hemisphere or in the deep brain structure can hardly be removed. Also, huge AVMs are difficult to remove. Seventeen cases of those AVMs were treated with artificial embolization in our clinic. Percutaneous interventional technique, using detachable balloon with or without cyanoacrylate derivatives and Silastic spheres, were also used. One of the main problems was a technical difficulty in injection of cyanoacrylate derivatives which resulted in two mobility.