Search PubMed⌕ Search

Biomedical subjects

T Shibazaki

Publications and source records attributed to T Shibazaki.

At least 37 records · Page 2Linked to original sources
PubMed1995

Fractionated Gamma Knife radiosurgery for malignant gliomas: neurobiological effects and FDG-PET studies.

Experimental single-dose neural irradiation was performed in rats and monkeys. Acute and 'early' late damage was observed following single high-dose treatments. By contrast, following a single low-dose treatment, neither 'early' nor 'delayed' late damage was noted. Based on these experiments, a clinical trial of fractionated Gamma Knife surgery for malignant gliomas was begun, and patients were followed by FDG-PET studies. An acute response of the tumor was obtained without damage to the surrounding brain. Fractionated Gamma Knife surgery is a potential alternative treatment for malignant gliomas.

Adult↗
PubMed1995

Gamma knife radiosurgery for acoustic schwannoma: early effects and preservation of hearing.

The effects of relatively low dose gamma knife irradiation on acoustic schwannoma were evaluated. The signal intensity change and tumor shrinkage on magnetic resonance (MR) images, change in hearing, and complications in 28 patients (mean age 47.0 +/- 13.6 yrs) were studied. Three patients had bilateral tumors. Six were already deaf when treated. The maximum tumor diameter was 35 mm. The mean dose delivered to the tumor was 12.1 +/- 1.6 Gy at the periphery, and 25.2 +/- 4.3 Gy at the center. The mean follow-up time was 16 months and the longest 24 months. Lowering of the MR signal intensity in the tumor center appeared after 3 months at earliest but generally after 6 months. Signs of tumor shrinkage appeared within 12 months on average. Cyst in the tumor enlarged rapidly after treatment in two patients. The percentage of hearing preservation was 85% (17/20) at 3 months, 80% (16/20) at 6 months, 72% (13/18) at 9 months, 75% (12/16) at 12 months, 67% (8/12) at 15 months, 60% (6/10) at 18 months, and 50% (2/4) at 24 months. Subtle changes in hearing were detected by speech tone audiometry. Temporary facial numbness and weakness was seen in one patient each. No patient had lower cranial nerve paresis. Relatively low dose gamma knife radiosurgery is effective in suppressing growth of acoustic schwannoma with preservation of hearing.

Adult↗
PubMed1994

Long-term follow-up study of conventional irradiation for brain tumours in children: a role for radiosurgery.

21 younger patients (less than 10 years of age) with brain tumours, treated by conventional irradiation, were followed 5 to 20 years (mean 12), using CT scan and/or MR imaging, in order to evaluate adverse effects on the developing brain. Pathological changes such as brain atrophy, lesions in the white matter, calcifications in the brain, and angiopathy were observed in 13 (62%) out of 21 cases. The incidence of abnormalities was related to the age at treatment and the follow-up period. All six cases treated at or under 5 years old and followed more than 10 years showed pathological changes in the brain. In order to minimize the radiation damage, 5 patients with brain tumours less than 5 years old were treated by gamma knife surgery. The early results encourage further trials. Radiosurgery may play a role as an alternative treatment or as a component of future multidisciplinary treatment for brain tumours is children.

Brain↗
PubMed1994

Radiosensitive craniopharyngiomas: the role of radiosurgery.

Clinical characteristics of radiosensitive craniopharyngiomas and histologically identical tumours were re-evaluated from among 53 patients. There were 9 squamous cell type and 3 mixed type tumours. Early effects of radiosurgery for two recent cases are reported. Radiosurgery may have an important role to play in the treatment of craniopharyngiomas, especially of the squamous cell type.

Adolescent↗
PubMed1994

Gamma knife radiosurgery in the treatment of a meningioma in a patient on maintenance hemodialysis: a case report.

To our knowledge, this is the first report ever on the implementation and results of gamma knife radiosurgery in a regularly dialysed patient. The case presented is that of a 59 year-old female patient with a meningioma. Her initial clinical presentation was with sustained headache. Diagnosis was made by using a brain CT scan and MR imaging. Treatment was performed literally without opening the skull. There was only one complication, namely that of postirradiation brain edema, which developed 19 weeks after the operation, and responded dramatically to steroid administration. This is one of the rare side effects of gamma knife therapy, but does not seem to be related to the fact that the patient was uremic. Gamma knife therapy was successful in this patient and her safety was no more compromised than that of a nonuremic patient undergoing radiosurgery.

Brain Edema↗
PubMed1993

Tremor-mediating thalamic zone studied in humans and in monkeys.

The thalamic zone mediating the rhythmic burst activity related to the contralateral tremor was studied by microelectrodes in clinical cases with tremor and in monkeys with experimental tremor. The rhythmic burst time-locked with the tremor was found in a restricted area of the ventrointermedius nucleus (Vim) in humans and also in VPLo nucleus in monkeys. In both cases, only the lateral and ventrocaudal part of each nucleus, which was defined as the kinesthetic zone, was involved. A possible tremor-mediating neural circuit is postulated.

Animals↗
PubMed1993

[Effect of tranilast ophthalmic solution on allergic conjunctivitis in guinea pigs].

The effect of the ophthalmic solution of tranilast, an anti-allergic agent, on allergic conjunctivitis was studied in passively sensitized guinea pigs. We determined the content of uranine dye and histamine in tears and histopathologically examined palpebral conjunctiva. After instillation of antigen into the conjunctival sac, inflammation of the palpebral conjunctiva, an increase in leaked dye and the release of histamine were found. In the histopathological study, tranilast (1.0%) suppressed the appearance of edema and infiltration of inflammatory cells. Tranilast suppressed the leakage of uranine in a dose-dependent manner. A 0.5% solution of diphenhydramine also showed the inhibitory effect on the leakage of uranine. The inhibitory effect of 0.5% tranilast on antigen-induced dye leakage and histamine release lasted for 6 hr. These results suggest that topically applied tranilast is effective for allergic conjunctivitis.

Animals↗
PubMed1993

Clinical evaluation of thallium-201 SPECT in supratentorial gliomas: relationship to histologic grade, prognosis and proliferative activities.

We performed 201Tl SPECT and cell kinetic studies on 28 presurgical patients with supratentorial gliomas by administering bromodeoxyuridine (BUdR). All patients had surgery and had follow-up for more than 25 mo. In patients with grade IV glioma (198.1% +/- 32.8%, n = 10), the 201Tl index, expressed as the count rate of the tumor site to the count rate over the contralateral normal region, was significantly higher than that in patients with grade III glioma (140.5% +/- 15.1%, n = 4, p < 0.01) or low-grade glioma (104.1% +/- 22.6%, n = 14, p < 0.001). A significant correlation was observed between the 201Tl index and BUdR-positive cells in excised tumor specimens (r = 0.67, p < 0.001). The 201Tl index of the 12 patients who died was higher than those who survived (173.2% versus 122.4%, p < 0.01). These results show the clinical utility of 201Tl brain SPECT in imaging supratentorial glioma and that the 201Tl index is representative of proliferative activity of the tumor.

Adult↗
PubMed1991

Pathophysiology of central (thalamic) pain: a possible role of the intralaminar nuclei in superficial pain.

In 15 patients with central pain (thalamic pain) after stroke, CT, PET scan and intraoperative thalamic microrecordings were performed. The results are considered together to evaluate a possible role of thalamic intralaminar nuclei in the genesis of central pain, especially of superficial pain. In the non-thalamic lesion group (deep pain dominant), thalamic background neural activity (BNA) was relatively high in Vim but low in CL. Conversely, in the thalamic lesion group (superficial pain dominant), thalamic BNA was higher in CL than in Vim, and markedly decreased in VC. In this group, regional cerebral oxygen consumption (rCMRO2) was relatively maintained, and regional oxygen extraction ratio (raOEF) and the relative value of regional cerebral glucose utilization (CMRGL), compared to rCMRO2, was increased in the cerebral cortex around the central sulcus. The genesis of superficial pain is discussed.

Aged↗
PubMed1991

[Evaluation of 201Tl SPECT in patients with glioma: a comparative study with histological diagnosis, clinical feature and proliferative activity].

The purpose of this study is to clarify the usefulness of 201Tl brain SPECT in the prediction of clinical degree of malignancy. Quantitative evaluation of 201Tl uptake in the tumor was expressed as count ratio of tumor site over contralateral normal region (D/C ratio) on 201Tl SPECT image. Fourteen patients with gliomas received an intravenous administration of bromodeoxyuridine (BUdR) at surgery to label tumor cells in the DNA synthesis phase. BUdR-positive cells in excised tumor specimen were stained with anti-BUdR monoclonal antibody by indirect immunoperoxidase staining. Percentage of labeled cells in relation to the total number of tumor cells in microscopic fields was defined as labeling index (BUdR-LI). D/C ratio in patients with grade IV glioma (198.7 +/- 31.7) was higher than that in patients with grade III glioma (138.3 +/- 33.9) or more low-grade gliomas (94.2 +/- 11.9, p less than 0.001). BUdR-LI in patients with high-grade glioma was also higher than that in patients with low-grade glioma. D/C ratio correlated well (r = 0.753) with BUdR-LI, which is considered to represent proliferative activity of the tumor. D/C ratio does not only correlate well with histological grade of glioma, but with clinical course or prognosis of individual patient with glioma. In conclusion, degree of 201Tl uptake in the tumor may provide non-invasive prediction of malignancy grade of gliomas and accurate estimation of efficacy of the therapy and early detection of recurrence or malignant transformation of the tumors, by delineating viable tumor tissue in patients with gliomas.

Adult↗
PubMed1990

Strategy of selective VIM thalamotomy guided by microrecording.

Our routine procedure for stereotactic selective Vim thalamotomy is described briefly. Preoperative steps identify the tremor qualitatively and quantitatively. The highlight of the procedure is the use of intraoperative microrecording to determine tremor time-locked rhythmic discharge in the presumed Vim nucleus. Results of the operation are also estimated quantitatively.

Electrocoagulation↗
PubMed1989

Further physiological observations on the ventralis intermedius neurons in the human thalamus.

1. During the course of stereotaxic thalamotomy for 56 cases with tremor mainly due to Parkinson's disease and essential tremor, extracellular recordings were made from the thalamic ventralis intermedius (Vim) nucleus under local anesthesia. These procedures have been justified as an essential technique to achieve the best therapeutic results by a selective coagulation. These physiological observations provide important information about the functional organization of the ventrolateral thalamic mass in humans. 2. Using Leksell's stereotaxic apparatus, a pair of semimicroelectrodes was introduced simultaneously to the thalamic ventral lateral region from the prefrontal area. The Vim nucleus was identified tentatively by characteristic high background activity which contrasted to that found in its rostral part and by superimposed large amplitude spontaneously active units. 3. In this high activity zone, 135 units (approximately 1/5 of the recorded units) responded to natural stimulation applied to contralateral body parts. Among them, approximately 90% responded to a passive or active movement of a joint. Several lines of evidence suggested that probably muscle receptors were responsible. 4. The rest of units (approximately 10%) responded to light touch applied to contralateral skin surface. Convergent responses between kinesthetic and tactile units were never encountered. Also, kinesthetic and tactile neurons were geographically separated. The latter were found always at the end of our oblique trajectory, following the kinesthetic neurons. 5. Neurons with sensory responses were clustered mostly within the confines of the Vim nucleus, probably extending caudally to the ventrocaudalis externus anterior of Hassler. Evidence for a somatotopic representation in the Vim nucleus was obtained. 6. Electrical stimulation of the appropriate peripheral nerve produced responses of the same thalamic unit(s) that responded to natural stimulation. The latency to upper limb nerve stimulation was between approximately 10 and 20 ms. It was almost fixed in a given case. 7. It is concluded that the Vim nucleus receives kinesthetic afferent input from the contralateral body parts (mainly from the muscle receptor) and may be concerned with muscle sense. This may explain why a small, selective coagulation of the physiologically identified Vim has such a constant effect on several different kinds of tremor.

Action Potentials↗
PubMed1989

Microrecording for the study of thalamic organization, for tumor biopsy and removal.

Use of microrecording technique in stereotactic selective thalamotomy, and in stereotactic biopsy for deep-seated lesions and in tumor removal was briefly described. For selective thalamotomy, the microrecording gives ample information to delineate thalamic subnuclei. Thus, the ventrointermedius (Vim) nucleus is identified by high-amplitude background activity and large-spike discharge, some of which responds solely to contralateral natural stimuli of kinesthetic modality. A small coagulation including this thalamic Vim point resulted in permanent arrest of the various kinds of tremor. As the normal brain tissue, whether the gray or white matter, is electrically active, the microrecording is useful to delineate the brain tumor from its surroundings. Stereotactic diagnostic biopsy and removal of the brain tumor were facilitated by this adjuvant method.

Biopsy↗
PubMed1989

[Analysis of relative cerebral perfusion in ischemic cerebral diseases by single photon emission computed tomography using N-isopropyl-p-[123I]iodoamphetamine].

Semiquantitative analysis of 123I-IMP SPECT enabled to evaluate relative regional cerebral perfusion and redistribution rates. Two parameters were calculated; the relative perfusion rate (RPR) is the ratio of radioactivity on a localized lesion divided by radioactivity on the visual cortex, the redistribution rate (RR) is the ratio of RPR in late images at 3 hrs divided by that in early images at 15 min postinjection. Total of 45 patients with ischemic cerebral diseases were studied. There were 29 males and 16 females with the age ranging from 37 yr to 80 yr. The RPRs were 81.3 +/- 5.1% in TIA (14 cases), 63.6 +/- 10.6% in RIND (8 cases), 64.6 +/- 8.5% in mild infarction (9 cases) and 40.2 +/- 13.8% in severe infarction (14 cases). RPR on the lesion of the severe infarction was extremely low compared to that of TIA, RIND and mild infarction. RPRs of lesions in the mild and severe infarction were reversely correlated to the size of LDA on X-ray CT (p less than 0.01). RPR was well correlated to clinical status of ischemic diseases. The RRs were 1.18 +/- 0.08 in TIA, 1.41 +/- 0.20 in RIND, 1.28 +/- 0.15 in mild infarction and 1.21 +/- 0.31 in severe infarction. The RR of RIND was significantly higher than those of other categorized groups (p less than 0.01). The RR may prove useful as a parameter reflecting tissue viability in cerebral ischemic diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗