Biomedical subjects
Publications and source records attributed to T Yamashima.
Electron microscopic data on human bridging veins show thin walls of variable thickness, circumferential arrangement of collagen fibres and a lack of outer reinforcement by arachnoid trabecules, all contributory to the subdural portion of the vein being more fragile than its subarachnoid portion. These features explain the laceration of veins and the subdural location of resultant haematomas.
An ultrastructural study was performed to define the mechanisms of proliferation of macrocapillaries and capillaries in the capsule of chronic subdural hematoma. Mitotic activities of endothelial cells and vascular sprouts may contribute to the vascular proliferation. Platelets may also play an important role. Endothelial cells of proliferating macrocapillaries were highly attenuated except for the nuclear portion and showed variable electron densities. The adjacent endothelial cells had less intimate cellular junctions than the proliferating capillaries. The proliferating endothelial cell sometimes contacted the opposing endothelial cell across the lumen, separating the latter into two compartments. The pericytes varied remarkably in size, shape, and electron density. Proliferating capillaries had a narrowed vascular lumen and were characterized by cuboidal or thickened endothelial cells with enlarged nuclei, numerous pinocytotic vesicles, and cytoplasmic protrusions into the vascular lumen. They occasionally had intimate cellular junctions with interdigitations and slender pericytes of high electron density. Proliferating vessels occasionally had some clear endothelial cells that contained filamentous material and a few dense bodies. These cells might represent degenerated or swollen endothelial cells. However, they showed no evidence of increased permeability. Postdegranulation platelets were sometimes trapped in the endothelial linings. These data indicate that the most important factor for the development of chronic subdural hematoma exists in the vessels of the capsules, which have a marked proliferation potential and a fragile nature. The possibility of transition from proliferating capillaries to macrocapillaries is discussed.
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Pathological changes of the cerebral arteries were studied in 30 dogs after subarachnoid injections of saline, fresh autologous blood, epinephrine, blood plus epinephrine, norepinephrine, or blood plus norepinephrine. Macroscopically, the circle of Willis was maximally dilated after the injection of epinephrine and was constricted following administration of blood plus epinephrine. Microscopically, neither saline nor blood produced abnormalities, except for minor changes of the adventitia in the latter. Epinephrine produced frank necrosis of smooth-muscle cells, which was subsequently replaced by fibrosis in the media of larger subarachnoid arteries, and the leakage of necrotic material from the infarcted hypothalamus contributed to these lesions. Blood plus epinephrine produced marked changes in the internal elastic lamina and tortuosities of the nuclei of smooth-muscle cells, while norepinephrine and blood plus norepinephrine produced only minor changes. Previously reported findings of morphological changes due to vasospasm after subarachnoid hemorrhage were confirmed experimentally, but such changes were found only after application of epinephrine. It is suggested that epinephrine produced the most severe vasospasm among the five substances tested.
The structure of macrocapillaries (also called 'sinusoids") in the outer membrane of chronic subdural hematomas was investigated by electron microscopy, with particular attention paid to vascular permeability. One characteristic of macrocapillaries is the frequent formation of gap junctions between adjacent endothelial cells. In endothelial gap junctions 0.6 to 8 microns in diameter, numerous blood components, including red blood cells and plasma, can be seen squeezing or spilling into the interstitial space of the outer membrane. Irregularly deformed erythrocytes are located around the macrocapillaries, and amorphous material is seen among scattered thin collagen fibers. It is suggested that endothelial gap junctions of macrocapillaries play an important role in the leakage of blood, causing enlargement of chronic subdural hematomas.
The intrathecal administration of amikacin (AMK) (50--100 mg/day) was effective for 3 cases of postoperative refractory meningitis caused by gentamicin (GM) resistant organisms. The infecting pathogen of case 1 was K. pneumoniae and that of case 2 was S. epidermidis, while no pathogen was cultured in case 3. The causative pathogens in the former were eradicated only with AMK. No therapeutic response was gained with GM, but with AMK in the latter. High tone hearing impairment was observed in case 1 and transient vomiting was observed in case 3. However, these side effects were trivial for the severity of disease. It is suggested in these 3 cases that the high dose intrathecal administration of AMK may be extremely useful in the treatment of postoperative refractory meningitis which has shown no response to GM.
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A six year-old boy. He complained of a swelling of the left forehead since October of 1971, the region of his upper eyelid has then been gradually swollen. He was admitted to our institute on the 24th of February, 1973, without the past history of head trauma. We found that the swollen region had a diameter of about 4 centimeters covered from the left upper eyelid to the forehead with a slight tenderness on pressure. We had no neurological findings. According to the results of skull X rays, the superior margin of left orbit and zygomatic process of frontal bone were swollen and like honey combs. An irregular, long and narrow osteolytic legion was found, which was about 4 centimeters long and 5 centimeters wide. According to the results of the left selective external carotid angiography, after injection of 60% Urografin, for more than 2.5- 10 seconds, at the left frontal bone an abnormal shadow (patchy contrast filling) was noted, which was about 4 centimeters long and 5 centimeters wide. After the direct injection of Urografid into the lesion, the cyst of one centimeter long and 3 centimeters wide was observed at the zygomatic process of the frontal bone. Operation was performed to excise the outer plate of the swollen bone and to curette the lesion after the ligature of the left external carotid artery. Histological examination showed many blood lakes and some multinuclear giant cells in the specimens and we diagnosed it was an aneurysmall bone cyst. This case is the first one of aneurysmall bone cyst confirmed by the selective external carotid angiography and the direct puncture of lesion.
A 43-year-old man with progressive right common carotid, subclavian artery, and brachiocephalic artery stenoses due to aortitis syndrome is presented. The patient's right common carotid artery had been treated by percutaneous transluminal angioplasty (PTA) four times previously, but it was finally occluded. The right subclavian artery was treated by PTA once, which resulted in restenosis. The stenosis extended to the brachiocephalic artery. For this patient, PTA followed by stent placement was performed for the right subclavian and brachiocephalic artery stenosis. Because arterial stenosis is progressive in cases of aortitis syndrome, simple PTA alone does not appear to be sufficient for treatment. We suggest that PTA followed by stent placement may be an alternative treatment for recurrent stenosis in aortitis syndrome.
We report on six cases of pericallosal lipomas. The T1-weighted sagittal images best demonstrated the relationship between the lipoma and the corpus callosum. In four cases the lipomas surrounded the splenium of the corpus callosum and in two cases the tumors were situated posteriorly and caudally to the splenium. In no case did we encounter an exclusively dorsal pericallosal localization.
This report describes three patients whose cystic portions were filled with intravenously injected Gadolinium-DTPA. Four cystic portions showed contrast enhancement of the whole wall on early MR images and enhancement of the content on delayed MR images. Two cystic portions showed no enhancement of content. We speculate that the difference is based upon the composition of the cyst walls.
In this report, the relationship of acoustic neuromas to the adjacent cranial nerves is discussed. On T1-weighted images, the trigeminal nerve was detected in all 13 cases. Mild to marked compression of these nerves by the tumors was observed in eight cases. The extent of compression did not always correspond to the clinical symptoms. In four cases with a maximum tumor diameter of 2 cm or less, the 7th and 8th cranial nerves were identified. There was no facial palsy in these patients. Two patients with a tumor diameter of more than 2 cm also had no facial palsy. All patients, including those with small tumors, complained of hearing loss and/or tinnitus. While MR imaging has some limitations, it is an effective imaging modality for showing the relationship between tumors and nerves.