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Hiroshi Yamada

✓ A method of regulating flow rate through cerebrospinal fluid (CSF) shunts with the addition of a flow-regulating device (FRD) is reported. The FRD consists of a small-caliber (0.4 mm) Teflon tube placed in the usual connector. This device has the advantage of converting the original shunt valves to valves for higher-resistance flow without replacing the entire distal catheter. An experimental study revealed that this device reduced the CSF flow rate in the shunt system by approximately 30%. The author has found it reliable in 32 patients, without causing CSF obstruction. The device is easily installed and removed.

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Hiroshi Yamada and Masataka Tajima

✓ A simple method of lengthening the venous catheter in a ventriculoatrial shunt is described.

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Hiroshi Yamada and Masataka Tajima

✓ A method for visualizing the third ventricle, aqueduct of Sylvius, and fourth ventricle with methylglucamine iothalamate 60% (Conray) in infantile hydrocephalus is described. Only a small amount of contrast medium is necessary to visualize these structures. This procedure has been performed in 47 infants from 7 days to 3 years of age, and has been proved simple, safe, and valuable in the diagnosis of lesions around the third and fourth ventricles.

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Hiroshi Yamada, Masaki Ohya, Tsuguo Okada and Zenji Shiozawa

✓ Five patients with intermittent claudication due to compression of the cauda equina in the presence of lumbar spinal canal stenosis or midline intervertebral disc protrusion are described. The characteristic myelographic evidence was complete obstruction during extension of the spine and release of the block with flexion. The cause of this syndrome is considered to be intermittent bulging of the ligamentum flavum into a narrow spinal canal so as to compress the cauda equina during extension of the back.

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Hiroshi Yamada, Masataka Tajima and Masahiro Nagaya

✓ The authors report a study of the effect of respiratory movement on intracranial, auricular, and intraperitoneal cerebrospinal fluid (CSF) pressure in hydrocephalic infants with shunts. Postoperative intraventricular pressures were also recorded for comparison. The intraventricular, right auricular, and intraperitoneal pressures rose during expiration and dropped during inspiration; the pressure changes were most marked while the infants were crying or straining. All pressures dropped simultaneously at the time of inspiration, but the auricular pressure was most significantly affected. It dropped to −100 to −200 mm H2O when the patients cried, while intraventricular and intraperitoneal pressures remained above 0 mm H2O. The postoperative intracranial pressures were in accord with these results; the pressures after ventriculoatrial shunt were significantly lower than those after ventriculoperitoneal shunt when the same pressure valves were used.

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Hiroshi Yamada, Shigetoshi Nakamura, Masataka Tajima and Naoki Kageyama

✓ The neurological and neuroradiological manifestations of pediatric achondroplasia are analyzed on the basis of 10 cases. In addition to the classical symptomatology of an enlarging head, with or without increased intracranial pressure, several patients presented symptoms related to a small foramen magnum. Respiratory problems and quadriparesis were also observed in these patients. Six patients who were treated by foramen magnum decompression showed remarkable improvement. Neuroradiological evaluation revealed a significant number of patients with dilated cortical sulci and basal cisterns, and mild dilatation of the ventricles on computerized tomography (CT) and/or ventriculography. Two patients showed signs of obstruction at the fourth ventricle outlets. Some exhibited anomalous dilatation of cerebral veins and dural sinuses, narrowing of the sinuses at the jugular foramen, and enlarged emissary veins. Ventriculoperitoneal or ventriculoatrial shunts were placed in three patients. In the other children with a large head and dilated ventricles, head growth curves paralleled the normal slope, and there was no significant clinical evidence of increased intracranial pressure or enlarging ventricles on follow-up CT scan.

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Hiroshi Yamada, Shigetoshi Nakamura and Naoki Kageyama

✓ The first reported instance of identical twins with moyamoya disease is presented. The involved portions of the main intracranial arteries were similar, but the formation of the moyamoya vessels was somewhat different. The cause of obstructive changes in large intracranial arteries remains obscure, but the frequent familial occurrence suggests that the initial stages of this disease and the formation of the moyamoya vessels occur in the prenatal period.

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Hydromyelic hydrocephalus

Correlation of hydromyelia with various stages of hydrocephalus in postshunt isolated compartments

Shizuo Oi, Hiroshi Kudo, Hiroshi Yamada, Songyu Kim, Seiji Hamano, Seishiro Urui and Satoshi Matsumoto

✓ The clinical features and pathophysiology of specific forms of hydromyelia are analyzed in this report together with the chronological changes of associated hydrocephalus. Nine patients were studied; all had hydromyelia with varying degrees of associated hydrocephalus. Clinically applicable classification systems were used to evaluate the progression of hydrocephalus (Stages I to IV) and to define the compartment isolated after shunting in the previously communicating cerebral ventricles (Types I to IV). Four patients had Stage IV disease (holoneural canal dilatation); one had Stage II and four had Stage I disease (both Stages I and II with supratentorial hydrocephalus). All patients were initially treated by ventriculoperitoneal shunting at an average age of 9.9 years. Five patients had progressive spinal symptoms before or after treatment of their hydrocephalus. Two patients had Type III isolation (an isolated rhombencephalic ventricle) with a functioning ventricular shunt; ventriculography confirmed a communication between the fourth ventricle and the hydromyelia, and both patients improved after placement of a shunt in the fourth ventricle. The remaining patients had Type IV isolation (isolated central canal dilatation) with a functioning ventricular shunt. This study indicates that in some cases the pathophysiology of hydromyelia is closely related to associated hydrocephalus. A new concept of the development of an isolated compartment after shunting is proposed to explain the progression of hydromyelia in these cases.