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Biomedical subjects

I Koyanagi

Publications and source records attributed to I Koyanagi.

At least 37 records · Page 2Linked to original sources
PubMed1997

Surgical treatment of syringomyelia associated with spinal dysraphism.

Clinical and radiological features of syringomyelia in 15 patients with spinal dysraphism are reported. There were 8 patients with occult spinal dysraphism (lumbosacral lipoma) and 7 with spina bifida aperta (meningomyelocele). Syringomyelia with spinal dysraphism can be radiologically divided into two types according to the dysraphic state. The syrinx in the patients with occult spinal dysraphism occurred immediately rostral to the lipoma and was localized to the lower thoracic to lumbar levels, while in the meningomyelocele patients the syrinx extended from the cervical to the thoracic level. Large syrinx formation was recognized in 1 of the 7 occult spinal dysraphism cases and 3 of the 8 meningomyelocele cases. For syringomyelia with occult spinal dysraphism, 4 patients underwent syringo-subarachnoid shunting (S-S shunt, 2 cases) or syringostomy (2 cases) during an untethering operation. In the case of meningomyelocele, S-S shunts were placed in 2 patients. Collapse of the syrinx was achieved in all 6 patients who underwent S-S shunting or syringostomy. Decreased size of the syrinx was also noted in 3 occult spinal dysraphism patients who underwent untethering operations alone. In conclusion, a large syrinx in the case of spinal dysraphism should be surgically treated. S-S shunting is effective in both types of syringomyelia. Foramen magnum decompression may be an alternative method of surgical treatment for syringomyelia in patients with meningomyelocele.

Child↗
PubMed1997

Surgical treatment supposed natural history of the tethered cord with occult spinal dysraphism.

We retrospectively evaluated the pre- and postoperative course of 34 tethered cord patients with occult spinal dysraphism in an attempt to infer the natural history of this disorder and to determine the effectiveness of the surgical treatment. There were 32 cases with lumbosacral lipoma and 2 with tight filum terminale. The age at surgery ranged from 1 month to 47 years old. Eight patients, aged 1 month to 4 years old, were asymptomatic; 26 had neurogenic bladder (26 cases) or motor problems affecting the legs (8 cases). None of the patients older than 5 years of age were asymptomatic. Untethering of the spinal cord was performed in all cases. The postoperative follow-up period ranged from 5 months to 11 years. During these periods, 7 (88%) of the 8 asymptomatic patients remained neurologically intact, 6 (23%) of the 26 symptomatic patients showed improved symptoms, and 15 patients (58%) remained unchanged. These results indicate that the neurological symptoms will appear progressively in the tethered cord patients, and that prophylactic surgery should be considered as early as possible.

Adolescent↗
PubMed1997

Effect of a single huge dose of methylprednisolone on blood flow, evoked potentials, and histology after acute spinal cord injury in the rat.

Effects of a single, huge dose of methylprednisolone on post-traumatic spinal cord blood flow (SCBF), evoked potentials and histological changes were studied in a rat model of spinal cord injury. The purpose of this study was to assess the optimal dose of methylprednisolone for the treatment of rat spinal cord injury. Twenty-five male Wistar rats were subjected to an acute clip compression injury at 51 g for 1 min at C8-T1, and then received an intravenous bolus injection of one of the following 30 min after injury: vehicle, 30, 60, 120 or 240 mg kg-1 methylprednisolone. SCBF was measured at the injury site and an adjacent area with the hydrogen clearance technique. Sensory evoked potentials following sciatic stimulation were recorded from the somatosensory and cerebellar cortices. Descending volleys were recorded from T9-10 spinal cord following cerebellar stimulation. SCBF and evoked potential recordings were repeated until perfusion-fixation at 4 h after injury. After injury, SCBF at both levels significantly dropped, and all evoked potentials disappeared in all animals. None of the doses of methylprednisolone improved post-traumatic SCBF, or evoked potentials. Quantitative histological assessment of the injured cords revealed no significant differences in hemorrhages or cavitation in the spinal cord among the treatment groups. This study showed that a single huge dose of methylprednisolone from 30 to 240 mg kg-1 had no beneficial effects on the traumatized rat spinal cord in the acute stage.

Acute Disease↗
PubMed1997

Bone window computed tomography for detection of dural defect associated with cervical ossified posterior longitudinal ligament.

Anterior decompression of a cervical ossified posterior longitudinal ligament (OPLL) which involves the dura mater occasionally results in a postoperative cerebrospinal fluid fistula. Bone window computed tomography (CT) was carried out to detect dural defects in 21 patients with cervical OPLL. Twelve of 21 patients had double-layer OPLL, and nine had single-layer OPLL. Dural defects were present in 10 of the 12 patients with double-layer OPLL compared with only one of the nine patients with single-layer OPLL. In addition, greater stenosis of the spinal canal by the OPLL was also associated with dural defect. Preoperative bone window CT can indicate likely locations of dural defect in patients with OPLL.

Adult↗
PubMed1997

Vascular mechanisms in the pathophysiology of human spinal cord injury.

Vascular injury plays an important role in the primary and secondary injury mechanisms that cause damage to the acutely traumatized spinal cord. To understand the pathophysiology of human spinal cord injury, the authors investigated the vascular system in three uninjured human spinal cords using silicone rubber microangiography and analyzed the histological findings related to vascular injury in nine acutely traumatized human spinal cords obtained at autopsy. The interval from spinal cord injury to death ranged from 20 minutes to 9 months. The microangiograms of the uninjured human cervical cords demonstrated new information about the sulcal arterial system and the pial arteries. The centrifugal sulcal arterial system was found to supply all of the anterior gray matter, the anterior half of the posterior gray matter, approximately the inner half of the anterior and lateral white columns, and the anterior half of the posterior white columns. Traumatized spinal cord specimens in the acute stage (3-5 days postinjury) showed severe hemorrhages predominantly in the gray matter, but also in the white matter. The white matter surrounding the hemorrhagic gray matter showed a variety of lesions, including decreased staining, disrupted myelin, and axonal and periaxonal swelling. The white matter lesions extended far from the injury site, especially in the posterior columns. There was no evidence of complete occlusion of any of the larger arteries, including the anterior and posterior spinal arteries and the sulcal arteries. However, occluded intramedullary veins were identified in the degenerated posterior white columns. In the chronic stage (3-9 months postinjury), the injured segments showed major tissue loss with large cavitations, whereas both rostral and caudal remote sites showed well-demarcated necrotic areas indicative of infarction mainly in the posterior white columns. Obstruction of small intramedullary arteries and veins by the initial mechanical stress or secondary injury mechanisms most likely produced these extensive white matter lesions. Our studies implicate damage to the anterior sulcal arteries in causing the hemorrhagic necrosis and subsequent central myelomalacia at the injury site in acute spinal cord injury in humans.

Acute Disease↗
PubMed1996

The effects of cortical stimulation, anesthesia and recording site on somatosensory evoked potentials in the rat.

The purpose of this study was to standardize the method of spinal cord monitoring with evoked potentials in the rat. Seventeen male Wistar rats were anesthetized with alpha-chloralose and urethane. Somatosensory evoked potential (SEP) and cerebellar evoked potential (CEP) following sciatic nerve stimulation were mapped at different time points after induction of anesthesia. SEP peaks at latencies of 13-18 ms (P13, N18) were localized to an extremely small area over the sensory cortex. In contrasts, a negative peak of the SEP at 11 ms (N11) and the CEP were widely distributed over the cerebral or cerebellar surface. Anesthesia significantly influenced the cortical components of the SEP. In 10 rats, MEP or posterior fossa evoked potential (PFEP) following stimulation of the sensorimotor or cerebellar cortices respectively, were recorded at T9. Stimulation of different points produced little change on the waveforms of the MEP or PFEP. Successive recordings of MEP and SEP revealed that the P13-N18 complex of the SEP was markedly suppressed after MEP recordings were made. In conclusion, this study identified several factors which alter SEP waveforms in the rat including location of recording, anesthesia and sequence with respect to MEP recording. MEP by stimulation of the same sensory cortex as SEP recordings should not be used for concurrent monitoring, since cortical stimulation will change the waveforms of the SEP.

Anesthesia↗
PubMed1996

[Clinical study of intraspinal neoplasms in children].

The authors report a series of 10 children under 15 years of age with primary intraspinal neoplasm who underwent surgical resection from 1981 to 1994. The tumors consisted of 4 intramedullary tumors (myxopapillary ependymoma, pilocytic astrocytoma, subpial liporna, cavernous angioma), 2 intradural extramedullary tumors (2 neurinomas), and 4 extradural tumors (ganglioneuroma, chordoma, osteochondroma, rhabdomyosarcoma). The initial symptoms in these patients were gait disturbance (50%), weakness of lower extremities (50%), pain (40%), weakness of upper extremities (10%), and tetraparesis (10%). The neurological findings on admission in these patients revealed motor paresis (90%), sensory disturbance (60%), abnormality of deep tendon reflex (60%), pathological reflex (30%), neurogenic bladder (30%), and Lasegue's sign (10%). All patients were treated surgically; laminectoy was performed in 8 patients, laminoplasty in one patient, and transoral approach in one patient. Five patients (50%) underwent a grossly total resection, 3 (30%) had a subtotal resection, and 2 (20%) had a partial resection. Mean follow-up period was 5.6 years. One (10%) patient died due to recurrence and dissemination of the tumor at eight months after surgery in a case of rhabdomyosarcoma. 9 (90%) have had no recurrent tumor and have improved neurologically. In 4 patients (40%) spinal deformity developed, and 2 patients required operative treatment for the spinal deformity. We emphasized the advantage of laminoplasty to prevent postoperative spinal deformity in children.

Adolescent↗
PubMed1995

The role of radiotherapy in the management of spinal cord glioma.

PURPOSE: To determine the role of radiotherapy in the management of spinal cord gliomas. METHODS AND MATERIALS: Thirty-six patients with spinal cord glioma treated between 1979 and 1993 were examined. The patients had 13 astrocytic tumors (7 astrocytomas, 4 anaplastic astrocytomas, 2 glioblastomas), 22 ependymal tumors (18 ependymomas, 4 myxopapillary ependymomas), and 1 unclassified glioma. Fifteen of the patients were treated by surgery alone, but the remaining 21 patients also received postoperative radiotherapy. Total resection was performed on 1 astrocytoma and 13 ependymomas. In general, 40-50 Gy/16-20 fractions/4-5 weeks were given after parital resection, but no radiotherapy was given after total resection. RESULTS: Actuarial survival was significantly better for patients with ependymal tumors than for those with astrocytic tumors (p = 0007), 5-year actuarial survival rates being 96% and 50% for patients with ependymal tumors and astrocytic tumors, respectively. For patients with ependymal tumors, there was no difference in motor function and survival between those with total resection and those with partial resection followed by radiotherapy. Actuarial 3-year survival was 80% for patients with astrocytomas and 40% for those with anaplastic astrocytomas plus glioblastomas. The difference in the degree of motor function between the patients treated with radiotherapy and those without radiotherapy was not statistically significant. One anaplastic astrocytoma and one glioblastoma patient have lived longer than 4 years after radical treatment including radiocordectomy, or irradiation using doses larger than the tolerance threshold of the spinal cord. CONCLUSION: Postoperative conventional radiotherapy is indicated after less than total resection of low-grade ependymal tumors and astrocytomas but not after total resection of ependymomas. Radiocordectomy may be an option for certain cases with high-grade astrocytic tumors.

Adolescent↗
PubMed1995

Surgical indication and results of foramen magnum decompression versus syringosubarachnoid shunting for syringomyelia associated with Chiari I malformation.

Several surgical procedures have been used for the treatment of syringomyelia associated with Chiari I malformation at our institute. The purpose of this article is to evaluate the results of two major surgical procedures, foramen magnum decompression (FMD) and syringosubarachnoid (SS) shunting. The series consisted of 70 patients with syringomyelia associated with Chiari I malformation who were surgically treated. Their ages ranged from 3 to 59 years (median, 29.4 yr). FMD was performed on 33 patients, and SS shunting was performed on 37 patients. The follow-up period ranged from 6 months to 12.5 years, with a mean of 60 months. The clinical and radiological outcomes were analyzed comparing the two groups. We principally performed FMD in patients with symptoms of Chiari I malformation and/or a small syrinx. We prefer to use SS shunting in patients with large syringes. Postoperative magnetic resonance imaging demonstrated that the syrinx had collapsed or decreased in size in 94% of the patients who underwent FMD and in 100% of the patients who underwent SS shunting. Neurological improvements were observed in 82% and in 97% of the patients who underwent FMD and SS shunting, respectively. In particular, the relief of pain was more fully achieved after SS shunting than after FMD. The average time for the syrinx to collapse was 6.3 weeks after surgery in the FMD group and 1.8 weeks in the SS shunting group. These results indicate that clinical symptoms and radiological findings improved much more quickly in the SS shunting group than in the FMD group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

[Surgical treatment for syringomyelia associated with Chiari malformation].

Two major surgical procedures, i.e., foramen magnum decompression (FMD) and syringo-subarachnoid shunt (S-S shunt) have been performed as the treatment for syringomyelia with Chiari malformation in our department. FMD was done principally in patients with symptoms due to Chiari malformation and for small size or localized syrinx, and S-S shunt was applied to patients with main symptoms due to syringomyelia, especially with local pain and for large syrinx in size. Eighty patients of syringomyelia with Chiari malformation were surgically treated. FMD was performed in 38 patients, and S-S shunt in 39 patients as the first operation. FMD were done with craniectomy of posterior fossa, C1 laminectomy and resection of epidural band, but without opening dura, and S-S shunt were done with hemipartial laminectomy and DREZtomy. The clinical outcome was evaluated, comparing the two major surgical procedures. Satisfactory neurological improvement was obtained in the two groups, but S-S shunt group took better improvement than FMD group. These results suggest that both procedures are effective, but should be selected by preoperative clinical and radiological findings.

Adolescent↗
PubMed1993

Sensory evoked potentials for selective monitoring of the rat spinal cord: a cerebellar evoked potential to assess ventral cord integrity.

The purpose of this study was to evaluate two types of ascending sensory evoked potentials (SEPs) in the rat and their capacity for selective monitoring of dorsal versus ventral spinal cord integrity. SEPs were elicited by direct sciatic nerve stimulation. A cerebellar evoked response was recorded over the paramedian lobule of the cerebellar hemisphere (CEPpml) while somatosensory evoked potentials (SSEPs) were simultaneously recorded over the sensorimotor cortex. All components of the CEPpml and SSEP except the longest latency positive waves were present in each animal. At stimulus intensities of 3 to 10 mA, no significant changes in latency of the peaks were observed, but amplitudes of the longer latency responses tended to increase throughout this stimulation range. Unilateral sciatic stimulation resulted in bilateral cortical responses, larger ipsilaterally for the CEPpml, and contralaterally for the SSEP. Selective spinal cord lesions demonstrated N9 and P14 of the CEPpml to be mediated primarily through the ventral spinal cord, while P14 and N19 of the SSEP were conducted primarily through the dorsal columns. Sectioning of the cerebellar peduncles abolished N9 and P14 of the CEPpml despite persistence of the SSEP. This study demonstrates that selective assessment of the ventral and dorsal spinal cord is possible in the rat by monitoring SEPs.

Animals↗
PubMed1993

Silicone rubber microangiography of acute spinal cord injury in the rat.

The purpose of this study was to investigate the acute changes in the large vessels and microvasculature of the spinal cord after acute clip compression injury in the rat. Nineteen female Wistar rats underwent acute compression of the spinal cord at C8-T1 at 53 g for 1 min. Silicone rubber was injected into the ascending aorta at 15 minutes, 1, 4, or 24 hours after injury. An additional nine rats served as normal controls. The perfused spinal cords were cleared by the alcohol-methylsalicylate technique. The results showed that, in the normal rat, the centrifugal arterial system from the sulcal arteries provided the major blood supply to the gray matter and the lateral and ventral white matter extending all the way to the pial surface. In the normal rat, there were large veins in the posterior columns coursing longitudinally in the parasagittal plane at the base of the posterior columns. The injured spinal cords displayed marked ischemia and hemorrhage at the injury site. The hemorrhage predominated in the gray matter and posterior white columns and extended rostrally and caudally for 2 to 7 mm in each direction from the injury site. Remote hemorrhages originated from damage to the large parasagittal veins in the posterior columns. Extravasations of silicone rubber were frequently seen at the earlier posttraumatic times and often originated from the sulcal arteries or their branches at the injury site. Occluded sulcal arteries were identified at the injury site at 4 and 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1993

Spinal cord evoked potential monitoring after spinal cord stimulation during surgery of spinal cord tumors.

Spinal cord evoked potentials (SCEPs) after spinal cord stimulation were used as a method of spinal cord monitoring during surgery of 6 extramedullary and 14 intramedullary spinal cord tumors. SCEPs were recorded from an epidural electrode placed rostral to the level of the tumor. Electrical stimulation was applied on the dorsal spinal cord from a caudally placed epidural electrode. The wave forms of SCEPs consisted of a sharp negative peak (N1) in 15 cases and two negative peaks (N1 and N2) in 5 cases. The N2 wave was markedly attenuated by posterior midline myelotomy, whereas the N1 activity showed less-remarkable changes by myelotomy. An increase in N1 amplitude was observed after the removal of the tumor in four extramedullary and three intramedullary cases. Of six patients that showed decreased N1 amplitude after the removal of the tumor, five patients developed postoperative motor deficits. However, there were four false-negative cases and one false-positive case in regard to changes of N1 amplitude and postoperative motor deficits. Four false results occurred in intramedullary cases. In two of them, postoperative symptoms indicated intraoperative unilateral damage to the spinal cord. The position of the stimulating electrode, the difference in thresholds of the axons for electrical stimulation between the right and left side of the spinal cord, or the change of the distance between the electrode and the spinal cord surface may account for these false results. Thus, our analysis of the changes of SCEP wave forms and early postoperative symptoms indicates that the sensitivity of this monitoring method to detect intraoperative insults to the spinal cord is unsatisfactory in spite of the reproducible wave forms. We conclude that SCEP monitoring can be used as an alternative method or in combination with other types of evoked potentials in patients with severe spinal cord lesions who show abnormal somatosensory evoked potentials preoperatively.

Adult↗
PubMed1993

Three-dimensional analysis of the vascular system in the rat spinal cord with scanning electron microscopy of vascular corrosion casts. Part 1: Normal spinal cord.

Vascular corrosion casts of polyester resin in the normal spinal cord at C4-C6 and C7-T1 were inspected three-dimensionally by scanning electron microscopy in 13 rats. Arteries and veins were easily differentiated by the impression pattern of endothelial nuclei on the casts. The centrifugal arterial system from the sulcal arteries supplied most of the gray and white matter in the ventral and lateral spinal cord. Each sulcal artery supplied only one side of the cord. The average number of sulcal arteries was 2.6 per mm. The centripetal arterial system from the posterior spinal arteries fed the posterior gray and white matter. In contrast with classical concepts, there was no pial arterial plexus on the ventral and ventrolateral surface except for infrequent transverse branches from the anterior spinal artery. In the posterior columns, two types of large veins were identified: the posterior medial septal veins and the posterior oblique veins that drained the posterior columns, medial posterior gray matter, and posterior gray commissure. The remainder of the gray and white matter was drained by the sulcal veins and the radial veins. This method clearly demonstrates the three-dimensional structure of both the arterial and venous system in the rat spinal cord.

Animals↗
PubMed1993

Three-dimensional analysis of the vascular system in the rat spinal cord with scanning electron microscopy of vascular corrosion casts. Part 2: Acute spinal cord injury.

The purpose of this study was to investigate the vascular mechanisms involved in the pathophysiology of acute spinal cord injury. Vascular corrosion casts of traumatized rat spinal cords at C7-T1 were inspected by scanning electron microscopy. Nineteen rats were subjected to a 51g acute clip compression at C8-T1 and then underwent transcardial perfusion with polyester resin at 15 minutes, 4 hours, or 24 hours after injury. The injured spinal cord appeared almost avascular at the compression site, although the large vessels on the surface of the spinal cord were all intact. The sulcal arteries at the injury site frequently showed constriction, and the impressions of endothelial nuclei were more slender and less distinct in the constricted arterial casts. Extravasation of the injected resin at the injury site was observed most frequently in the 15-minute group. Poorly filled distal branches of the sulcal arteries were seen at the injury site in every group. Indeed, it was concluded that the disruption and occlusion of the sulcal arteries and their branches accounted for a considerable amount of the posttraumatic ischemia of the cord. Occlusion of the sulcal arteries in the anterior median sulcus at the injury site was more frequently observed in the 24-hour group than in earlier groups. This observation suggests that there was a progressive circulatory disturbance of the damaged sulcal arteries at the injury site. The 4- and 24-hour groups showed avascular areas extending longitudinally from the injury site in the posterior columns, probably the result of hemorrhage and venous obstruction.

Aneurysm↗
PubMed1993

[Intraoperative monitoring for spinal cord tumor by spinal cord evoked potential following unilateral spinal cord stimulation].

We described our experiences with intraoperative spinal cord monitoring in 6 cases of spinal cord tumor. During the operation, spinal cord evoked potential following unilateral spinal cord stimulation was recorded from subdural monitoring electrodes. This series included two cases of intradural extramedullary tumor (one case each of neurinoma and of meningioma) and four cases of intramedullary tumor (2 cases of cavernous angioma, one case each of ependymoma, and of glioblastoma multiforme). Before the removal of the tumor, the spinal cord evoked potential showed lower amplitude or no response on the more affected side in all 6 cases. During the operation, the different intraoperative changes were shown on each side. The authors think that the detection of unilateral damage to the spinal cord is possible in spinal cord evoked potential using unilateral spinal cord stimulation.

Adult↗
PubMed1992

Scoliosis associated with syringomyelia presenting in children.

The clinical presentations and radiological features of scoliosis accompanying syringomyelia were analyzed in 14 cases of syringomyelia associated with a in 14 cases of syringomyelia associated with a Chiari malformation in children. Scoliosis was the initial symptom in 11 out of 16 patients (64%) with syringomyelia and present in 14 (88%) at the initial examination. The scoliosis associated with syringomyelia was characterized by a higher incidence of a single curve (6 cases, 43%) and convexity to the left (7 cases, 50%) than seen in idiopathic scoliosis. The syrinx was shifted to the convex side of scoliosis on the axial section at the middle or lower thoracic level in patients with a single curve, and at the cervical or upper thoracic level in patients with a double curve. The authors think that the scoliosis develops in children as a result of damage done to the anterior horn, which innervates the muscles of the trunk, by an asymmetrically expanded syrinx.

Arnold-Chiari Malformation↗