Search PubMed⌕ Search

Biomedical subjects

K Mimatsu

Publications and source records attributed to K Mimatsu.

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

Effects of chondroitinase ABC on degenerative intervertebral discs.

The effects of chondroitinase ABC on surgically induced degenerative rabbit intervertebral discs were determined during a 12-week period by magnetic resonance imaging, radiography, and histologic examination. Rabbit intervertebral discs were surgically extruded, inducing disc degeneration 12 weeks before injection of chondroitinase ABC. Magnetic resonance imaging showed a hypointense area in the center of the surgically induced disc degeneration. After injection of chondroitinase ABC, the hypointense area became more intense, but reversed somewhat by the end of the 12-week period. Additional evidence of the effects of chondroitinase ABC on a surgically induced degenerative disc model was shown by radiographic evidence of shrinkage of the disc after injection. Histologic examination revealed a fibrous degenerative disc induced by surgical extrusion. However, the staining properties of the matrix of the nucleus pulposus was similar to that of normal discs before chondroitinase ABC injection, but diminished after the injection, with slight recovery at 12 weeks. The results suggest that chondroitinase ABC induces chemonucleolysis in the degenerated disc. Also, chondroitinase ABC does not destroy the degenerative disc matrix ability to regenerate after 12 weeks.

Animals↗
PubMed1995

Paraparesis after rib penetration of the spinal canal in neurofibromatous scoliosis.

Paraplegia or paraparesis is uncommon in patients with neurofibromatous scoliosis. The main causes of spinal cord compression in neurofibromatosis are vertebral angulation, vertebral subluxation, and tumorous lesions around the spinal cord. We report a rare case of paraparesis due to spinal cord compression by a rib penetrating the spinal canal in a patient with neurofibromatous scoliosis. There was complete recovery after laminectomy and proximal resection of the compressing rib along with combined anterior and posterior spinal fusion.

Child↗
PubMed1994

Intraoperative ultrasonographic evaluation of the spinal cord in cervical myelopathy.

Intraoperative spinal ultrasonography (IOSS) was used to evaluate and monitor the spinal cord in 49 patients with cervical myelopathy. Intraoperative spinal ultrasonography demonstrated movements of the dura mater and the spinal cord at the cardiac rate, with some variability in intensity and mode. It also delineated the anterior surface of the spinal canal and configuration of the spinal cord. Statistical analysis showed no correlation between clinical outcome and morphologic restoration, and between clinical outcome and variations in intensity or mode of the pulsatile spinal cord movements. Spinal cord motions were surmised to be generated not only by the anterior spinal artery, but also by other factors. Dural pulsations clearly did not always imply the absence of compression of the spinal cord. Intraoperative spinal ultrasonography was thus quite useful for monitoring decompression in cervical myelopathy.

Adult↗
PubMed1993

The increased signal intensity at the vertebral body endplates after chemonucleolysis demonstrated by magnetic resonance imaging.

Changes in signal intensity observed by magnetic resonance imaging in the contiguous end plates of injected discs after chemonucleolysis over a period of 2 years in 28 patients were evaluated. These changes appeared to be of two types; a transiently increased signal intensity on T2-weighted images, and a progressively increased signal intensity on T1-weighted images with isointense or hyperintense signal on T2-weighted images. The former appeared within three months and disappeared within 2 years. This change was observed in six patients (21%), whose mean age was higher than that of the other patients. This change correlated with the preinjection state of the affected disc. The latter appeared after 2 years and was accompanied by sclerotic changes on roentgenograms. These changes were observed in five patients (18%). The discs, of which the contiguous end plates showed these changes, did not recover the decreased nuclear signal intensity in four patients. These changes are considered to be a sign of degenerative spondylosis in the treated segment.

Adult↗
PubMed1993

Early diagnosis of lumbar spondylolysis by MRI.

Radiography and CT and MRI scans of the lumbar spine were performed in young patients complaining of pain during extension of the lumbar spine but without neurological signs in the lower limbs. T1-weighted MR images in the coronal plane showed a hypo-intense area in the pars interarticularis before the detection of spondylolysis at that site by plain radiography or CT. We suggest that this may be useful in the early diagnosis of spondylolysis.

Adolescent↗
PubMed1993

New transducers for intraoperative spinal sonography. Technical note.

Although ultrasonography during spinal cord surgery has been widely accepted, it still has limitations in clinical application because of the size of the transducers needed and the immersion method. The authors report on newly designed microprobe transducers used to evaluate intramedullary spinal cord lesions and to monitor surgical procedures. This microprobe system permitted the microscopic use of intraoperative ultrasonography without requiring saline immersion.

Female↗
PubMed1993

Comparison of tissue reaction with chondroitinase ABC and chymopapain in rabbits as the basis of clinical application in chemonucleolysis.

Although chemonucleolysis with chymopapain is an approved treatment for lumbar intervertebral disk herniation, recent serious complications have raised doubt concerning its safety. It is therefore necessary to search for a safer and more selective agent than chymopapain for chemonucleolysis. Experimental chemonucleolysis with chondroitinase ABC was thus tested and compared with chymopapain. Acute tissue reactions to chondroitinase ABC were investigated and compared with chymopapain. The epidural space, yellow ligament, sciatic nerve, knee joint, and Achilles tendon were examined. Chymopapain damaged nervous and ligamentous tissues as well as cartilaginous tissue. Chondroitinase ABC did not damage nervous and ligamentous tissue. Chondroitinase ABC affected only cartilaginous tissue, and its action was chiefly limited to digestion of the matrix. Chondroitinase ABC has high enzymatic specificity for matrix in vivo. In addition, chondroitinase ABC is less toxic to noncartilaginous tissues than chymopapain. Chondroitinase ABC might be a more suitable and safer enzyme than chymopapain for chemonucleolysis.

Achilles Tendon↗
PubMed1992

Changes seen on magnetic resonance imaging in the intervertebral disc space after chemonucleolysis: a hypothesis concerning regeneration of the disc after chemonucleolysis.

Measurements of the intervertebral disc space were made by magnetic resonance imaging and plain film examinations over a period of 2 years in 26 patients who had undergone chemonucleolysis. The height of the posterior portion of the disc decreased after 3 months and never recovered; the height of the anterior portion also decreased but recovered slightly over the same period. The angle of lordosis and the range of motion in the treated segment were decreased, but recovered. Marked decrease in signal from the disc was observed after 2 weeks which did not recover till 2 years after chemonucleolysis. We suspect that the disc degenerated markedly after chemonucleolysis and changed into a type of scar tissue, maturation of which could stabilize the affected segment.

Adolescent↗
PubMed1992

Intraoperative sonography of intramedullary spinal cord tumours.

Intraoperative spinal sonography was performed 23 times in 20 patients with intramedullary spinal cord tumours, and the sonographic features were examined. Eight cases of astrocytoma were classified into three types: type 1, seen in 3 children, had intramedullary, circular or oval, hyperechogenic multiple tumour shadows; type 2 presented inter-multimyelomere, relatively well-defined single tumour shadows corresponding to grade III and I for two juvenile and aged cases each, respectively; and type 3 appeared ill-defined and diffusely infiltrating. The relationships between these types, the ages of patients and histological grades were considered a potential clue to mechanisms of occurrence and infiltration of astrocytoma. All 7 ependymomas had syrinxes, of three types; central canal was very large, the tumour lying within it like an island; or the tumour was in contact with a cephalocaudal side part of the syrinx; or the tumour had a syrinx or cyst. Sonographic images thus differ according to the tumour, but differential diagnosis is currently limited. Development of sonographic equipment, with upgrading its resolving power are hoped for.

Adolescent↗
PubMed1992

Intraoperative ultrasonography of extramedullary spinal tumours.

Intraoperative spinal sonography (IOSS) was performed in 28 patients with extramedullary spinal tumours. Images were obtained of 31 tumours, because 2 patients had multiple tumours. There were 17 neurilemmomas, 9 meningiomas and 2 dermoid cysts. All tumours appeared well-defined and highly echogenic. There was no difficulty differentiating extramedullary spinal tumours from intramedullary masses excepting case, a big neurilemmoma at the conus medullaris. All images were assessed with reference to the surface of the lesions, the existence of cysts, and movement. Neurilemmomas had smooth surfaces, some cysts, and exhibited a "floating" movement. Meningiomas had irregular surfaces, were more highly echogenic than neurilemmomas, and adhered tightly to the dura mater. However, some neurilemmomas and meningiomas did not have these, and it was not always possible to differentiate them. Although IOSS has limitations of resolution, it gave useful information about the size of the tumours, the degree of displacement of the spinal cord, and even about the type of tumour in some cases. It was extremely helpful to the surgeon.

Adult↗
PubMed1992

Serial changes observed by magnetic resonance imaging in the intervertebral disc after chemonucleolysis. A consideration of the mechanism of chemonucleolysis.

Changes in the intervertebral disc after chemonucleolysis in 26 patients were observed by magnetic resonance imaging for 1 year, and from the results a mechanism for chemonucleolysis was considered. A reduction in size of the herniation was not recognized 2 weeks after treatment, when chymopapain had caused necrosis of the disc, but began after 4 weeks, when regeneration of the disc had occurred. The herniation was further reduced after 3 months, and the disc had become fibrocartilaginous in a cicatricial process. Marked decrease in disc signal was observed after 2 weeks, and never recovered. From these facts, it is considered that chymopapain might never cause primary diminution of disc herniation, and any reduction of herniation that occurs is due to the effects of a secondary cicatricial contraction.

Adolescent↗
PubMed1992

Postoperative changes in the spinal cord in cervical myelopathy demonstrated by magnetic resonance imaging.

The relation between improvement of myelopathy achieved by surgery and postoperative spinal cord morphologic changes was investigated by magnetic resonance imaging in 51 patients with cervical myelopathy. In 22 patients, the cord indentation disappeared completely (Type I), in 23 it partially disappeared (Type II), and in 3 it remained unchanged (Type III). In three patients the cord enlarged after surgery (Type IV). With the exception of Type IV, increased restoration of cord morphology paralleled improvement in the myelopathy, suggesting that morphologic changes closely reflect neurologic recovery. In Type IV, notwithstanding the peculiar postoperative reaction, improvement was relatively good, and shrinkage of the cord enlargement was seen after 1 year. This kind of postoperative change has not been demonstrated previously by other conventional imaging methods.

Adult↗
PubMed1992

Histopathologic and morphometric study of spinal cord lesion in a chronic cord compression model using bone morphogenetic protein in rabbits.

Chronic compressive myelopathy was induced in domestic rabbits by implanting bone morphogenetic protein on the ligamentum flavum of the lumbar spine, and the resulting spinal cord lesion was studied histopathologically. In addition, morphometry of myelinated nerve fibers of the white matter in the pathologic specimens was performed to elucidate the mechanisms of cord injury. No loss of white matter nerve fibers was seen when the cord compression ratio (sagittal diameter/transverse diameter) was > 45%, although 6 months later myelin thinning was present throughout the white matter. When the cord compression ratio was < or = 45%, loss of fibers, particularly of large fibers, was seen in the superficial layer of the white matter, with the nerve fibers remaining after 6 months showing decreased diameters. No motor paresis was evident in any animal. These histologic changes represent the early pathologic condition induced by chronic cord compression.

Animals↗
PubMed1991

Changes in the evoked spinal cord potentials associated with chronic experimental cord compression.

To determine the functional changes occurring in the early period after the development of chronic cord compression, an ossification of the ligamentum flavum model, which is a model of chronic cord compression, was created in domestic rabbits using bone morphogenetic protein, and monitored evoked spinal cord potentials. Sixty-seven rabbits were used for these experiments. Myelography, evoked spinal cord potential measurements, and histologic examinations were performed in 16 of the ossification of the ligamentum flavum rabbits and six of the healthy control rabbits. Our results show that 1) mild degrees of cord compression produce greater evoked spinal cord potential alterations in chronic than in acute compression, as reported in the literature; 2) chronic compression from the dorsal side produces injury in the superficial layer of the dorsal column and dorsolateral column; and 3) changes in evoked spinal cord potentials precede the development of paralysis and histologic changes.

Animals↗