Biomedical subjects

T Tachisawa

Publications and source records attributed to T Tachisawa.

5 recordsLinked to original sources

PubMed1997

[40-Hz auditory steady state response (40-Hz SSR) in patients with intracranial lesions--with reference to consciousness level and sites of lesions].

OBJECTIVE: The issue of whether the 40-Hz SSR could become a useful neurophysiological monitoring tool in the patients with intracranial lesions was investigated. SUBJECTS AND METHODS: 40-Hz SSR was recorded in 50 normal persons and 63 patients with intracranial lesions, and correlation among differences in consciousness level, lesion site and 40-Hz SSR was determined. RESULTS: (1) Consciousness level and lesion site were both statistically significantly correlated with the pattern of wave forms at a single variable (alpha < 0.0001). (2) Using the multivariate's analysis, an equation to predict the level of consciousness from the SSR waveform and the site of lesion was made. The coefficient of determination between the calculated value and the actual value was 0.822. (3) In the group with intracranial lesions, the P1-N1 amplitude was confirmed to have significantly decreased (alpha < 0.0001) despite a apparently alert level. DISCUSSION AND CONCLUSION: This study revealed that the pattern of 40-Hz SSR waveforms varies with changes in consciousness and lesion site. Moreover, the amplitude of individual waves of SSR waveform is distinctly reduced prior to change the waveform pattern in the alert group. These findings mean that subtle changes of intracranial status could be detected by the continuous monitoring of 40-Hz SSR even at earlier stage of second insult. Consequently, the 40-Hz SSR is a probable objective means of monitoring the consciousness level.

Adult↗

PubMed1992

Significance of different levels of the Edinburgh 2 coma scale calculated from the outcome of neurosurgical patients.

In the management of patients with acute cerebral disturbances, it is essential to determine precisely the degree of impaired consciousness. In order to secure the accuracy of observations, one must use a reliable coma scale. We have evaluated the Edinburgh 2 coma scale (E2CS) and explored the relationship between levels of the E2CS and the final outcome. Case notes and observation charts of the past 7 years were reviewed, covering neurosurgical operations on 406 patients, in each of whom the postoperative course was evaluated periodically by the E2CS and the outcome was determined by the Glasgow outcome scale. By matching the outcome with each level of impaired consciousness, about 22,000 pairs of data were obtained. In order to quantify the morbidity rate, different stages of the Glasgow outcome scale were rated from 100 through 0, arbitrarily. It was proved that levels of the E2CS were arranged in the correct order in respect to both mortality and morbidity rates. It was shown at the same time that each level has different prognostic significance and that the distance between each level is not identical. The recommendation is made to separate the levels on a chart not by an ordinal number but by the distance calculated on the basis of either mortality or morbidity rates. This will make it possible to get a rough estimate of the patients' prognoses by simply looking at a daily clinical chart.

Adolescent↗

PubMed1988

Structural mechanics of the blowout fracture: numerical computer simulation of orbital deformation by the finite element method.

Blowout fractures most frequently involve the orbital floor. The contour of the orbit has been postulated as one of the factors responsible for this phenomenon, but only a few studies have been carried out. The present study was planned to determine the effect of the contour of the orbit when intraorbital pressure is raised to simulate the hydraulic mechanism of blowout fracture. The profile of the orbit was estimated from five dry human skulls, and the measurements were approximated to frame models. The deformation of these models by raised intraorbital pressure was calculated by computer simulation using the finite element method. In all of the orbital models, the deformation of the orbital floor was significantly greater than that of the roof. These findings verified that the orbital roof has a higher resistance than the floor against raised intraorbital pressure. We suspect that this resistance is due to the arched shape of the orbital roof, whereas the floor is rather flat.

Computer Simulation↗

PubMed1987

Parasellar chondroma: a case report.

A case of a 19-year-old man with a right parasellar chondroma examined with computed tomography (CT) and nuclear magnetic resonance (NMR) scan is reported. The literature about CT and NMR scan findings of intracranial chondroma is reviewed. Typical CT findings are a round, high density mass with calcification, that is only slightly enhanced by contrast medium.

Adult↗

PubMed1985

Intracranial pressure monitoring by a subdurally placed silicone catheter: technical note.

A silicone catheter manufactured originally for ventricular fluid drainage was used for continuous monitoring of intracranial pressure. It can be placed under the dura mater immediately before replacing the craniotomy flap or by introduction through an ordinary burr hole. Pressure is monitored isovolumetrically by connecting the catheter to a pressure transducer mounted at the bedside. This technique has been used in 34 neurosurgical patients for periods of up to 12 days without any untoward effects. This monitoring system by a subdurally placed silicone catheter is simple, safe, inexpensive, and acceptably reliable. It has a place in clinical practice, particularly when the lateral ventricle cannot be tapped because of its deviation or collapse.

Catheters, Indwelling↗