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Biomedical subjects

R W Seiler

Publications and source records attributed to R W Seiler.

At least 37 records · Page 2Linked to original sources
PubMed2000

Silent cerebral ischemia detected by diffusion-weighted MRI after carotid endarterectomy.

BACKGROUND AND PURPOSE: Small emboli arising from a friable plaque during carotid endarterectomy (CEA) constitute an important risk of perioperative ischemic complications. To evaluate the incidence and significance of silent cerebral ischemic lesions of embolic origin after CEA, we prospectively examined a series of surgical patients with high-grade carotid stenosis by using diffusion-weighted MRI (DWI). We also tried to correlate postoperative ischemic lesions with the occurrence of sonographic cerebral embolic signals, the presence of plaque ulcerations, and the use of intraoperative shunting. METHODS: Of a consecutive series of 53 patients undergoing elective CEA for high-grade carotid stenosis, 48 patients with unchanged postoperative neurological status were prospectively studied with DWI of the brain the day before and the day after the operation. The magnetic resonance images were analyzed by 2 neuroradiologists blinded to the clinical result of the operation. Any new hyperintense signal was interpreted as a postoperative ischemic lesion. RESULTS: Forty-six (95.8%) of 48 patients had unchanged postoperative brain DWI. In 2 patients (4.2%), a new single asymptomatic hyperintense signal was observed on the side of the operation. Both lesions were small and presumably of embolic origin. They were not related to sonographic embolic signals, plaque ulcerations, or intraoperative shunting. CONCLUSIONS: These results suggest that the incidence of silent ischemic brain lesions of embolic origin after CEA is low and does not correlate with the occurrence of intraoperative sonographic microemboli. They confirm that CEA is a safe procedure that carries a low risk of postoperative cerebral events.

Aged↗
PubMed2000

Sellar reconstruction with resorbable vicryl patches, gelatin foam, and fibrin glue in transsphenoidal surgery: a 10-year experience with 376 patients.

OBJECT: Closure of the sella turcica after transsphenoidal surgery is mainly accomplished with autologous muscle fascia and fat or muscle; this requires a second surgical incision. The authors review the results of using resorbable vicryl patches, gelatin foam, and fibrin glue for sellar reconstruction. METHODS: A review was conducted of 376 consecutive patients who underwent surgery for pituitary adenomas, cysts, or subdiaphragmatic craniopharyngiomas in the sella turcica that the senior author (R.W.S.) had performed or directly supervised over the last 10 years. The sellar reconstruction was performed with a commercially available, synthetic absorbable patch composed of polyglactin 910/poly-p-dioxanone, gelatin foam, and fibrin glue. The patch is essentially resorbed in 2 to 3 months and replaced by fibrous collagen tissue. There were 117 small, 112 medium-sized, and 147 large lesions. The overall nonendocrine postoperative morbidity rate was 2.8%, and included visual deterioration, meningitis, secondary epistaxis, nasal septum complication, and cerebrospinal fluid (CSF) leakage. Two patients with macroadenomas needed reoperation for persistent CSF leakage, which comprised 0.5% of the whole series or 0.8% of the 259 patients with medium-sized or large lesions. There was no mortality and no morbidity related to the implanted material, and in particular no delayed empty sella syndrome. CONCLUSIONS: Closure of the sella turcica with a synthetic absorbable vicryl patch, gelatin foam, and fibrin glue after transsphenoidal surgery is safe and very effective in preventing postoperative CSF fistulas. The use of this technique obviates the need for a second surgical incision and shortens the operating time. Because of the progressive resorption of the substitute material, the interpretation of postoperative magnetic resonance studies was not significantly hindered.

Adenoma↗
PubMed2000

Transdural cauda equina incarceration after microsurgical lumbar discectomy: case report.

OBJECTIVE AND IMPORTANCE: Complications usually occur when they are least expected. We present an unusual case of nerve entrapment after microsurgical discectomy. CLINICAL PRESENTATION: A patient undergoing uneventful first lumbar microsurgical discectomy developed severe back and leg pain and a progressive neurological deficit during the first postoperative night. Herniation of cauda equina nerve roots had occurred through an unnoticed minimal defect in the dura, which had not caused cerebrospinal fluid leakage. The roots were incarcerated and swollen, and they filled the space of the resected nucleus pulposus. It was presumed that elevation of intra-abdominal pressure and consequent increased intraspinal pressure during extubation led to the herniation of arachnoid and cauda equina roots. The nerve roots were then trapped and incarcerated in the manner of bowel loops in an abdominal wall hernia. INTERVENTION: During reoperation, the nerve roots were repositioned into the dural sac. The patient recovered without further complications and without long-term sequelae. CONCLUSION: All dural tears that occur during intraspinal surgery, even if they are small and the arachnoid is intact, should be closed with stitches or at a minimum with a patch of muscle or gelatin sponge with fibrin glue. Care should be taken to avoid increased intra-abdominal pressure during extubation. Excessive pain and progressive neurological dysfunction occurring shortly after microsurgical lumbar discectomy or any intraspinal procedure is indicative of possible hemorrhage with subsequent compression of nerve roots. The case reported here provides anecdotal evidence that this situation can also be caused by a herniation of cauda equina nerve roots through a small dural defect that was not evident during the initial operation.

Cauda Equina↗
PubMed1999

Striatal grafts in a rat model of Huntington's disease: time course comparison of MRI and histology.

Survival and integration into the host brain of grafted tissue are crucial factors in neurotransplantation approaches. The present study explored the feasibility of using a clinical MR scanner to study striatal graft development in a rat model of Huntington's disease. Rat fetal lateral ganglionic eminences grown as free-floating roller-tube cultures were grafted into the quinolinic acid-lesioned striatum, and T1- and T2-weighted sequences were acquired at 2, 7, 21, and 99 days posttransplantation. MR images were then compared with images of corresponding histological sections. The lesion-induced striatal degeneration caused a progressive ventricle enlargement, which was significantly different from controls at 21 days posttransplantation. Seven days posttransplantation, T1-weighted images revealed a defined liquid-isointense signal surrounded by a hyperintense rim at the site of graft placement, which was found unaltered for the first 21 days posttransplantation, whereas a hypointense graft signal was detected at 99 days posttransplantation. At 2 days posttransplantation, T2-weighted images showed the graft region as a hyperintense area surrounded by a rim of low signal intensity but at later time-points graft location could not be further verified. Measures for graft size and ventricle size obtained from MR images highly correlated with measures obtained from histologically processed sections (R = 0.8, P < 0.001). In conclusion, the present study shows that fetal rat lateral ganglionic eminences grown as free-floating roller-tube cultures can be successfully grafted in a rat Huntington model and that a clinical MR scanner offers a useful noninvasive tool for studying striatal graft development.

Animals↗
PubMed1999

Endoscopic stereotactic surgery for intraventricular loculated empyema: case report.

BACKGROUND: Ventriculitis accompanied by formation of an intraventricular loculated empyema is a very unusual complication of purulent meningitis. CASE DESCRIPTION: A 62-year-old man presented with acute purulent ventriculitis secondary to a small paraventricular abscess. The well-documented computed tomography scans demonstrated the development of an intraventricular loculated empyema in the posterior portion of the left lateral ventricle. A stereotactically guided endoscopic procedure was performed to drain and rinse the empyema and to remove membranous tissue in order to establish free communication with the ventricular system. In the further course, a ventriculoperitoneal shunt was placed. The patient had recovered almost completely 1 year after the procedure. CONCLUSIONS: Ventriculitis frequently results in severe morbidity and often causes death. Intraventricular pathologies can be treated effectively by endoscopic stereotactic methods. To our knowledge, this is the first case of successful treatment of an intraventricular loculated empyema in an adult.

Brain Diseases↗
PubMed1998

Rat fetal ventral mesencephalon grown as solid tissue cultures: influence of culture time and BDNF treatment on dopamine neuron survival and function.

Free-floating roller tube (FFRT) cultures of fetal rat and human nigral tissue are a means for tissue storage prior to grafting in experimental Parkinson's disease. In the present study, FFRT cultures prepared from embryonic-day-14 rat ventral mesencephalon were maintained for 4, 8, 12, or 16 days in vitro (DIV) in the presence or absence (controls) of BDNF [100 ng/ml]. The dopamine content in the culture medium, analyzed by HPLC, was significantly higher (4-5 fold) in the BDNF group at DIV 8 and DIV 12 compared to the corresponding control levels (40 pg/ml). The number of tyrosine hydroxylase immunoreactive neurons was significantly higher for BDNF treated cultures (2729+/-300) at DIV 8, as compared to controls (1679+/-217). At DIV 12, the culture volume was significantly increased by BDNF (1.05+/-0.12 vs. 0.71+/-0.04 mm3). Similar results were obtained for total protein. Western blot analysis demonstrated increasing signals for GFAP with increasing time in culture, but levels for control and BDNF treated cultures did not differ at any time-point investigated. In conclusion, it is suggested that the time window for effective storage of dopaminergic tissue prior to grafting can be extended by using the FFRT culture technique and that the in vitro storage may be further prolonged by treatment with BDNF.

Animals↗
PubMed1998

[Surgical versus medical treatment of idiopathic trigeminal neuralgia].

The primary treatment of idiopathic trigeminal neuralgia is medical. Surgery is reserved for unresponsive patients or in case of long lasting, tedious or dangerous side effects of the medication. The surgeon has to inform the patient about risks and benefits of the different surgical methods and consider the patient's expectations and fears in order to choose the best surgical alternative. We describe the clinical picture of trigeminal neuralgia, the steps leading to the diagnosis. We also discuss the pathogenesis and the different treatment modalities with emphasis on surgical methods.

Elective Surgical Procedures↗
PubMed1998

Effects of combined BDNF and GDNF treatment on cultured dopaminergic midbrain neurons.

Neural transplantation is an experimental therapy for Parkinson's disease. Pretreatment of fetal donor tissue with neurotrophic factors may improve survival of grafted dopaminergic neurons. Free-floating roller tube cultures of fetal rat ventral mesencephalon were treated with brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), or a combination of both. Dopamine content of the culture medium, the number of tyrosine hydroxylase-immunoreactive neurons, and culture volumes were moderately increased in the BDNF- and GDNF-treated cultures but significantly increased by 6.8-, 3.2- and 2.4-fold, respectively after treatment with the combination of both factors. We conclude that pretreatment of dopaminergic tissue in culture with a combination of BDNF and GDNF may be an effective means to improve the quality of tissue prior to grafting.

Analysis of Variance↗
PubMed1998

Implants of polymer-encapsulated genetically modified cells releasing glial cell line-derived neurotrophic factor improve survival, growth, and function of fetal dopaminergic grafts.

Neural transplantation as an experimental therapy for Parkinsonian patients has been shown to be effective in several clinical trials. Further benefit, however, may be expected if the grafting is combined with a treatment of neurotrophic factors thus improving the survival and growth of grafted embryonic dopaminergic neurons. Continuous trophic support may be needed and therefore requires the long-term delivery of neurotrophic factors to the brain. We demonstrate here that the implantation of polymer-encapsulated cells genetically engineered to continuously secrete glial cell line-derived neurotrophic factor to the adult rat striatum improves dopaminergic graft survival and function. Near complete compensation of 6-hydroxydopamine-induced rotation was already achieved within 3 weeks postgrafting in rats that received glial cell line-derived neurotrophic factor-releasing capsules in addition to dopaminergic cell grafts of cultured tissue. Rats without trophic factor supply showed only little recovery at the same time point and sham grafted rats showed no recovery. The number of tyrosine hydroxylase-immunoreactive cells per graft was increased 2.6-fold in the presence of glial cell line-derived neurotrophic factor 6 weeks postgrafting. Similarly, tyrosine hydroxylase-immunoreactive fibers around the graft were increased by 53%. Moreover, these fibers showed a preferential growth towards the trophic factor-releasing capsule. Taken together, these results provide evidence that encapsulated genetically engineered cells are an effective means of long-term trophic factor supply into the adult rat brain and that the delivery of glial cell line-derived neurotrophic factor can sustain dopaminergic graft function and survival.

Animals↗
PubMed1998

Comparison of mesencephalic free-floating tissue culture grafts and cell suspension grafts in the 6-hydroxydopamine-lesioned rat.

Ventral mesencephalon (VM) of fetal rat and human origin grown as free-floating roller-tube (FFRT) cultures can survive subsequent grafting to the adult rat striatum. To further explore the functional efficacy of such grafts, embryonic day 13 ventral mesencephalic tissue was grafted either after 7 days in culture or directly as dissociated cell suspensions, and compared with regard to neuronal survival and ability to normalize rotational behavior in adult rats with unilateral 6-hydroxydopamine (6-OHDA) lesions. Other lesioned rats received injections of cell-free medium and served as controls. The amphetamine-induced rotational behavior of all 6-OHDA-lesioned animals was monitored at various time points from 18 days before transplantation and up to 80 days after transplantation. Tyrosine hydroxylase (TH) immunostaining of the histologically processed brains served to assess the long-term survival of grafted dopaminergic neurons and to correlate that with the behavioral effects. Additional cultures and acutely prepared explants were also fixed and stored for histological investigation in order to estimate the loss of dopaminergic neurons in culture and after transplantation. Similar behavioral improvements in terms of significant reductions in amphetamine-induced rotations were observed in rats grafted with FFRT cultures (127%) and rats grafted with cell suspensions (122%), while control animals showed no normalization of rotational behavior. At 84 days after transplantation, there were similar numbers of TH-immunoreactive (TH-ir) neurons in grafts of cultured tissue (775 +/- 98, mean +/- SEM) and grafts of fresh, dissociated cell suspension (806 +/- 105, mean +/- SEM). Cell counts in fresh explants, 7-day-old cultures, and grafted cultures revealed a 68.2% loss of TH-ir cells 7 days after explantation, with an additional 23.1% loss after grafting, leaving 8.7% of the original number of TH-ir cells in the intracerebral grafts. This is to be compared with a survival rate of 9.1% for the TH-ir cells in the cell-suspension grafts. Immunostaining for the calcium-binding proteins calretinin, calbindin, and parvalbumin showed no differences in the neuronal expression of these proteins between the two graft types. In conclusion, we found comparable dopaminergic cell survival and functional effects of tissue-culture grafts and cell-suspension grafts, which currently is the type of graft most commonly used for experimental and clinical grafting. In this sense the result is promising for the development of an effective in vitro storage of fetal nigral tissue, which at the same time would allow neuroprotective and neurotrophic treatment prior to intracerebral transplantation.

Amphetamine↗
PubMed1998

Surgical treatment of lumbar spinal stenosis in the elderly.

148 elderly patients, aged 70 years or more, diagnosed as having lumbar spinal stenosis, were operated upon at our institution during 1983 to 1995. Totally 161 operative procedures were performed. We analysed retrospectively the results of the surgical treatment. The most frequently performed procedure was multisegmental laminectomy, in 32% interlaminar fenestration and laminotomy were done. In 9 cases fusion was indicated, two of them being secondary operations. The mean hospital stay was 11 days. The morbidity was 6%, and there was one fatality (0.6%). The outcome was determined according to the six-grade classification proposed by Pappas and Sonntag [25]. Overall, in 91% of cases satisfactory-to-excellent results could be achieved. We conclude, that in elderly patients with symptomatic lumbar spinal stenosis, with no evidence of instability, decompressive surgery without stabilisation can be done in the majority of patients with low morbidity and high expectation of clinical improvement.

Aged↗
PubMed1997

Evaluation of hemodynamic responses in head injury patients with transcranial Doppler monitoring.

Transcranial Doppler (TCD) can monitor middle cerebral artery (MCA) velocity which can be recorded simultaneously with other physiologic parameters such as end tidal (Et) CO2, arterial blood pressure and intracranial pressure (ICP), in head injured patients. Relative changes in MCA velocity can be used to reflect relative MCA blood flow changes during ICP waves, and also to evaluate cerebral autoregulation, CO2 reactivity and hemodynamic responses to mannitol and barbiturates. The utility and practicality of short intervals of TCD monitoring to evaluate hemodynamic responses, was evaluated in a group of 22 head injured patients (average Glasgow coma score 6). During ICP A waves, MCA velocity always decreased during the peak of the wave, and during ICP B waves, fluctuated synchronously with the ICP. Dynamic cerebral autoregulation, and reactivity to CO2, were reduced within 48 hours of admission. Impaired cerebral autoregulation within 48 hours of admission did not correlate with outcome at 1 month. Mannitol infusion caused an increase in MCA velocity (15.4 +/- 7.9%) which was significantly correlated to the impairment of dynamic autoregulation (r = 0.54, p < 0.0001). The MCA velocity response to a test dose of barbiturates was significantly correlated to the ICP (r = 0.61, p < 0.01) response as well as to the CO2 reactivity (r = 0.37, p < 0.05). Continuous MCA velocity monitoring using TCD may be useful in evaluating a variety of hemodynamic responses in head injury patients and may replace more cumbersome cerebral blood flow techniques which have been used in the past for these purposes.

Adolescent↗
PubMed1997

[Tethered spinal cord syndrome in adults].

The tethered spinal cord syndrome is more often encountered in children, but does also occur in adults. Its clinical spectrum comprises low back pain, neurological deficits such as distal motor weakness and trophic and sensory disturbances in the legs, urological symptoms and such musculoskeletal signs as scoliosis or foot deformities. In addition, cutaneous lesions or subcutaneous lipomas in the lumbosacral region may be indirect signs of an intraspinal pathology. This consists in a tight, thickened and sometimes shortened filum terminale, an intraspinal lipoma, intradural scar formation or other lesions that lead to conus fixation. The common mechanism of injury of these types of pathologies is an impairment of longitudinal movement of the spinal cord, especially the conus medullaris, which subsequently leads to chronic local ischemia. Diagnosis is most readily achieved by magnetic resonance imaging. Treatment is aimed at the restoration of cord mobility by means of microsurgical release of the conus, the cauda equina and the filum terminale with the aid of cauda equina neuromonitoring. Further progression can be effectively halted; in fact almost half of the patient actually improve. Therefore, every patients presenting with the clinical diagnosis of tethered cord syndrome should be offered specialized surgical treatment.

Adult↗
PubMed1997

Continuous intraoperative monitoring of middle cerebral artery blood flow velocities and electroencephalography during carotid endarterectomy. A comparison of the two methods to detect cerebral ischemia.

BACKGROUND AND PURPOSE: Intraoperative monitoring of brain function may influence the outcome of carotid endarterectomy (CEA). METHODS: We performed transcranial Doppler (TCD) monitoring of middle cerebral artery blood flow velocities (VMCAs) and eight-channel electroencephalographic (EEG) recording simultaneously in 82 patients undergoing CEA. Thiopental narcosis limited EEG interpretation in 11 patients, thus allowing direct comparison of both methods in 71 patients. RESULTS: There was a significant correlation between VMCA decrease and the frequency of EEG changes after carotid clamping (P < .001). Eight patients (11%) showed a VMCA decrease exceeding 60%, accompanied by EEG changes in 7 patients. Altogether, 16 patients (22%) showed severe or moderate EEG changes. Stenosis or occlusion of the contralateral carotid artery led to an increase of abnormal findings with both monitoring methods, which was, however, significant only for TCD (P < .05). Four patients (4.8%) suffered intraoperative transient ischemic attacks. In 3 of these patients, there were no abnormal findings with either of the methods. The events were thus unpredictable and probably of embolic origin. The fourth patient showed VMCA decrease to 0 and severe EEG changes. Nine patients had severe or moderate EEG changes without significant VMCA decrease and without complications. EEG monitoring alone in these would have led to unnecessary use of a shunt with the increased risk of embolism. CONCLUSION: EEG and TCD monitoring are complementary techniques. Their results showed a good overall correlation but with marked differences in the individual patient. TCD monitoring alone was sensitive enough to prevent ischemic intraoperative complications. EEG findings are of limited value when barbiturates are used.

Aged↗
PubMed1996

Fetal ventral mesencephalon of human and rat origin maintained in vitro and transplanted to 6-hydroxydopamine-lesioned rats gives rise to grafts rich in dopaminergic neurons.

Free-floating roller tube cultures of human fetal (embryonic age 6-10 weeks post-conception) and rat fetal (embryonic day 13) ventral mesencephalon were prepared. After 7-15 days in vitro, the mesencephalic tissue cultures were transplanted into the striatum of adult rats that had received unilateral injections of 6-hydroxydopamine into the nigrostriatal bundle 3-5 weeks prior to transplantation. Graft survival was assessed in tyrosine hydroxylase (TH)-immunostained serial sections of the grafted brains up to post-transplantation week 4 for the human fetal xenografts and post-transplantation week 11 for the rat fetal allografts. D-amphetamine-induced rotation was monitored up to 10 weeks after transplantation in the allografted animals and compared with that of lesioned-only control animals. All transplanted animals showed large, viable grafts containing TH-immunoreactive (ir) neurons. The density of TH-ir neurons in the human fetal xenografts and in rat fetal allografts was similar. A significant amelioration of the amphetamine-induced rotation was observed in the animals that received cultured tissue allografts. These results promote the feasibility of in vitro maintenance of fetal human and rat nigral tissue prior to transplantation using the free-floating roller tube technique.

Animals↗
PubMed1996

Effects of brain-derived neurotrophic factor on neuronal structure of dopaminergic neurons in dissociated cultures of human fetal mesencephalon.

Brain-derived neurotrophic factor (BDNF) has been shown to promote the survival of cultured fetal mesencephalic dopaminergic neurons of rat and human origin. In the present study, BDNF was tested for its ability to influence neuronal structure of dopaminergic neurons in dissociated cultures of human fetal ventral mesencephalon after 7 days in vitro. Following immunocyto chemical staining for tyrosine hydroxylase, all surviving dopaminergic neurons were counted. Computer-assisted three-dimensional reconstructions of uniform randomly selected neurons cultured with 50 ng/ml BDNF (n = 120) or without BDNF (n = 80) were made. BDNF increased the number of surviving human dopaminergic neurons by 76%. Mean soma profile area was significantly enlarged by 18% in BDNF-treated neurons as compared to controls. Analysis of parameters of neuritic size and complexity in these cultures revealed that combined neuritic length, combined neuritic volume, and neuritic field area were increased by 60%, 125% and 129%, respectively, and the mean number of segments per cell was increased by 41%. A change in neurite complexity in BDNF-treated cultures was further confirmed by the Sholl's concentric sphere analysis. These results demonstrate that BDNF promotes development and differentiation of human fetal dopaminergic neurons in vitro.

Brain-Derived Neurotrophic Factor↗