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Biomedical subjects

C Ohye

Publications and source records attributed to C Ohye.

At least 37 records · Page 2Linked to original sources
PubMed1996

Gamma Knife radiosurgery for acoustic schwannoma: effects of low radiation dose and functional prognosis.

The effects of relatively low dose Gamma Knife irradiation on acoustic schwannoma were evaluated in 29 patients followed over 2 years after treatment. The mean dose delivered to the tumor periphery was 12.1 Gy. Lowering of the magnetic resonance signal intensity in the tumor center appeared in 69% and signs of tumor shrinkage appeared in 59% of cases. The cyst in the tumor enlarged in 3 cases, and 2 cases developed hydrocephalus. The percentage of pure-tone hearing preservation was 82% at 3 months, 73% at 6 months, 68% at 12 months. 64% at 18 months and 59% at 24 months in 22 out of 29 cases. Relatively low dose Gamma Knife radiosurgery was effective in suppressing tumor growth, with preservation of hearing.

Adult↗
PubMed1996

Pathobiology of cerebral gliomas in children and the role of radiosurgery.

Twenty-five gliomas of the cerebral hemisphere in children were examined. Most hemispheric gliomas in children have relatively clear margins and less infiltrative potential. Radiosurgery has a role in the treatment of these tumors in addition to reducing the risk of radiation injuries developing later. Fifteen patients were alive 1-27 years (mean 8.4) following treatment and 10 patients died. Histologic examination demonstrated 10 differentiated gliomas, 10 poorly differentiated gliomas and 5 other gliomas. Most tumors had relatively clear margins on computed tomography and/or magnetic resonance images, and peritumoral edema was slight. In 9 autopsy cases, tumor dissemination and/or metastasis were seen in 7. However, tumor infiltration was not extensive, and clear tumor margins were found in some cases. Thus, cerebral gliomas in children have relatively clear margins and low infiltrative potential. Radiosurgery has a role in the treatment of these tumors.

Adolescent↗
PubMed1996

Peripheral nerve regeneration in a silicone tube: effect of collagen sponge prosthesis, laminin, and pyrimidine compound administration.

Regeneration of transected peripheral nerve with a 10-mm gap encased in a silicone tube was evaluated in the presence of collagen sponge with or without laminin, or with systemic administration of a pyrimidine compound, MS-818. The sciatic nerve of 20 adult rats was transected and the proximal and distal nerve stumps were fixed in a silicone tube. The lumen of the silicone tube was empty, or filled with a collagen sponge alone or with a laminin-soaked collagen sponge. Also, a pyrimidine compound was injected intraperitoneally after implantation of the empty silicone tube. Three weeks later, the contents of the silicone tubes were processed for histological examination of regenerated nerve fibers. Other animals were observed 6, 12, and 18 months after surgery to examine the long-term effects of the collagen sponge on nerve regeneration. All animals had regenerated tissue within the tube 3 weeks after nerve transection. The diameter of the tissue decreased toward the distal stump in the empty tube, but was the same throughout the full length in the collagen sponge-containing tube. Immunohistochemical studies revealed that the nerve fibers extended beyond the midline of the regenerated tissue in animals treated with a laminin-containing collagen sponge or receiving a pyrimidine compound. Long-term observation showed the regenerated nerve was thick as the proximal stump and many neurofilament- and peripheral myelin-positive fibers were observed around the collagen sponge. Collagen sponge assists the progress of regenerated tissues in silicone tubes, and laminin-containing prostheses and administration of a pyrimidine compound enhance peripheral nerve regeneration.

Animals↗
PubMed1996

[Automatic anatomic-physiologic correspondence of deep structures of the central nervous system in stereotaxic functional neurosurgery].

This work describes in detail the graphic facilities of a neurosurgical deep recording system for the anatomic-physiologic analysis of central nervous system deep structures in stereotaxic function neurosurgery guided by deep semi-microrecordings of the brain, as developed by the International Center of Neurologic Restoration in Cuba. This system for digitization of electrical activity in the brain uses an IBM-compatible 80386/80486 microprocessor in place of analog equipment for the visualization and recording of signals, thereby providing easier manipulation of recorded data and greater flexibility of analysis. The system automatically integrates each pulse recorded and quantifies its average amplitude. For each brain region explored, the behavior of the integrated activity recorded can be displayed on the corresponding sagittal view from the cerebral atlas of Schaltenbrand-Wahren, and then automatically scaled to the anatomic dimensions of each patient. The picture, with its different options, Facilitates analysis of anatomic correspondence of deep electrophysiologic signals so the various structures, nuclei and specific neuronal groups can be precisely located in the patient's brain. To date the system has been used successfully in over 110 neurosurgical procedures ventral intermedios (vim)-thalamotomy, pallidotomy, subthalotomy and neurotransplantation, providing more certain location of lesions or grafting sites for managing symptoms in Parkinson's disease and other movement disorders.

Brain↗
PubMed1995

Grafts of genetically modified fibroblasts expressing neural cell adhesion molecule L1 into transected spinal cord of adult rats.

L1, a neural cell adhesion molecule, is known to promote neurite elongation via a homophilic interaction in vitro. In the present study, fibroblast L cells that were genetically modified to express the L1 molecule were grafted to a lesion of rat spinal cord immediately after hemisection. Grafts drastically promoted regeneration of the axons in the injured spinal cord 2 weeks after grafting. A number of regenerating axons penetrated the glial scar along the host-graft interface, and elongated into the graft. These results suggest that grafts of genetically modified cells expressing L1 can provide an environment suitable for regeneration of the axons in the injured spinal cord.

Animals↗
PubMed1995

Parkinsonian rigidity, dopa-induced dyskinesia and chorea--dynamic studies on the basal ganglia-thalamocortical motor circuit using PET scan and depth microrecording.

Regional cerebral glucose metabolism (rCMRGlu-18FDG) was measured in 6 cases with rigid type Parkinson's disease (PD) (2 cases with dopa-induced dyskinesia = DID), 6 cases with chorea (Ch), 5 cases with essential tremor (EssT) and 2 cases with normal subjects (N). The effects of L-Dopa on rCMRGlu was studied in 3 cases with PD. With the aid of depth microrecording study, stereotactic pallidotomy was performed in all cases with PD. Thalamotomy was performed in 3 cases with Ch. In the EssT and N group, the metabolic pattern was high in the frontal cortex (FCx) but low in the lenticular nucleus (LN). In contrast, all cases with a rigid type PD showed lower rCMRGlu in FCx (premotor, prefrontal area). However, 4 out of 6 cases were higher in LN than the control group. Administration of L-Dopa shifted rCMRGlu toward the normal pattern in this group. Five out of 6 cases with Ch represented higher rCMRGlu in FCx (3 focal, 2 diffuse) but lower in LN. Moreover, when DID occurred, it showed almost the same pattern as in Ch. Electrophysiological studies showed high background neuronal activity (BNA) in the medial segment of the globus pallidus (GP) but low BNA in the lateral segment of the GP in the rigid type of PD. In cases with Ch, irregular burst discharges were often encountered in ventro-oral thalamus. From these results, the on-going changes of basal ganglia-thalamocortical motor circuit in cases with a rigid type PD, DID and Ch are discussed. The underlying mechanisms of Parkinsonian rigidity was considered to contrast with those of DID and Ch within the same motor circuit.

Antiparkinson Agents↗
PubMed1995

Calcified astrocytoma of the amygdalo-hippocampal region in children.

Three pediatric cases of temporal lobe seizure due to calcified glioma of amygdalo-hippocampal region are described. Computed tomography and magnetic resonance imaging showed dense calcification with no postcontrast enhancement in the amygdalo-hippocampal region. Positron emission tomography showed low oxygen metabolism, low glucose metabolism, hypermetabolism of amino acids, and low regional cerebral blood flow in the tumors. Single photon emission computed tomography showed a high accumulation of 201Tl chloride and 123I-isopropyl iodoamphetamine in one tumor, but otherwise low radioisotope uptake. These studies indicated low-grade malignancies. The patients were treated by partial tumor removal and radiotherapy. Histological examination of the tumor specimens showed astrocytoma with interstitial calcification. One patient died due to tumor recurrence, while the others are doing well with minimal seizure. We recommended temporal lobectomy in similar cases to achieve complete remission.

Adolescent↗
PubMed1995

Positron emission tomography with 4-[18F]fluoro-L-m-tyrosine in MPTP-induced hemiparkinsonian monkeys.

PET imaging studies with 4-[18F]fluoro-L-m-tyrosine (FMT) in normal macaca monkeys showed selective accumulations of radioactivity in the striatum with time. In monkeys rendered hemiparkinsonian by intracarotid infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), FMT uptake was eliminated in the lesioned striatum. FMT-PET studies were able to detect dopaminergic terminals in both normal and hemiparkinsonian monkeys, and clearly showed a reduction in aromatic L-amino acid decarboxylase (AAAD) activities in the MPTP-lesioned striatum. These results show that FMT is promising as a PET tracer for the evaluation of central dopaminergic systems in parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1995

Gamma Knife radiosurgery for the treatment of brainstem tumors.

Ten patients with brainstem tumors (BST) underwent Gamma Knife radiosurgery. In 5 cases, there were definitive histological diagnoses; ependymoma (n = 3) and CNS lymphoma (n = 2). The others were diagnosed as ependymoma (n = 1), CNS lymphoma (n = 2) and glioma (n = 2) on clinical grounds. Of 4 cases with ependymoma, the tumor showed a marked response in 3 cases. Of 4 cases with CNS lymphoma, all responded rapidly and the clinical symptoms improved markedly. However, in the 2 cases with glioma, the tumor remained unchanged or continued to grow. Gamma Knife radiosurgery was effective in local growth control of BST without adverse effects. An alternative treatment design will be required in glioma cases.

Adult↗
PubMed1995

Classification of arteriovenous malformations for radiosurgery. Neuroimaging, histopathology and radiobiologic effects.

Arteriovenous malformations (AVMs) were classified based on morphologic and hemodynamic factors. They were categorized as Moya type, shunt type or mixed type on the basis of hemodynamic factors, and as homogeneous or heterogeneous types on the basis of morphology. Histopathologic and radiobiologic characteristics were evaluated with respect to these AVM types. Classification depending on the type as well as the size of an AVM is important for modern treatment modalities, especially radiosurgery.

Cerebral Angiography↗
PubMed1995

Gamma Knife thalamotomy for the treatment of functional disorders.

Gamma Knife thalamotomy was performed with a 4-mm collimator in 2 cases with thalamic pain following a stroke and in 1 case of Parkinson's disease with tremor. In both cases with pain the maximum dose of 130 Gy was focused at the mediocaudal region of the previous thalamic lesion. In the case with tremor in Parkinson's disease, the maximum dose was 150 Gy. Longer follow-up is now proceeding, but the short-term results are encouraging. Based on data obtained from selective thalamotomy with depth microrecording, Gamma Knife thalamotomy could be a safe and effective technique for the treatment of these functional disorders.

Aged↗
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↗
PubMed1995

Hypothalamic hamartoma: anatomic, immunohistochemical and ultrastructural features.

Four patients with hypothalamic hamartoma were examined by CT and/or MR imaging, immunohistochemistry and electron microscopy. The hamartomas arose from the hypothalamus and extended inferiorly. LH-RH neurons were detected in three cases by immunohistochemistry. Electron microscopy revealed large myelinated axons, axon terminals containing dense-core vesicles and axon terminals with clear vesicles forming asymmetrical synapses. The development of hypothalamic hamartoma and its functional manifestations (precocious puberty and laugh attacks) are discussed in reference to the migration of LH-RH neurons from the olfactory placode.

Axons↗
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

The new age of stereotaxis: toward the 21st century.

The remarkable recent progress in stereotactic surgery, functional as well as nonfunctional, is briefly reviewed, with emphasis on our own experiences. Owing to the day-by-day progress of computer-assisted neuroimaging and basic research in neuroscience, stereotactic surgery has greatly benefitted. In this sense, the future of stereotactic surgery could be 'en rose' and quite promising toward the 21st century.

Brain Tissue Transplantation↗