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Biomedical subjects

T M Markwalder

Publications and source records attributed to T M Markwalder.

18 recordsLinked to original sources
PubMed1991

"Isthmic" spondylolisthesis--an analysis of the clinical and radiological presentation in relation to intraoperative findings and surgical results in 72 consecutive cases.

72 patients with isthmic spondylolisthesis have been analyzed prospectively with respect to their clinical presentation, radiological and intraoperative findings, operative techniques and surgical results. Excellent, good and satisfactory results have been obtained in 59 (82%), 10 (14%) and 3 patients (4%), respectively, by use of microsurgical techniques in combination with Louis-plate-fixation in Grade I and double arthrodesis/Cotrel-Dubousset-instrumentation in Grade II spondylolisthesis.

Adolescent↗
PubMed1991

Atlanto-axial fusion with transarticular screw fixation.

We reviewed 161 patients, from four centres in Switzerland, who had undergone posterior fusion of the upper cervical spine with transarticular screw fixation of the atlanto-axial joints. They were followed up for a mean 24.6 months. The vertebral artery and the medulla escaped injury and only 5.9% of the complications were directly related to the screws. The rate of pseudarthrosis was 0.6%.

Adolescent↗
PubMed1989

Diagnostic approach in instability and irritative state of a "lumbar motion segment" following disc surgery--failed back surgery syndrome.

A diagnostic protocol for patients with suspected instability and irritative state of a "lumbar motion segment" following lumbar disc surgery is presented and the results of internal fixation are analyzed. In this group of patients the clinical picture and physical signs may be quite distinct and suggestive of instability and irritation of a "lumbar motion segment", however, in isolation, they do not allow to decide upon surgery. Radiological studies favour a decision for surgery only in cases with an obvious instability of a "motion segment". Anaesthethizing the articular nerves permits localization of the irritable segment and non-surgical therapeutic decisions (thermocoagulation) can only be taken in cases of an isolated facet-syndrome when instability has been ruled out. The trial plaster jacket holds the most important position with respect to the indication for internal fixation as demonstrated by the conformity of the results of the plaster jacket and the results of surgery. After internal stabilization excellent, good, satisfactory and moderate results were obtained in 20, 3, 1 and 1 patients, respectively.

Anesthesia, Spinal↗
PubMed1989

Translaminar screw fixation in lumbar spine pathology. Technical note.

Two technical variations of the method of translaminar screw fixation for unstable lumbar and lumbosacral segments are presented. Distraction-arthrodesis with intraarticular bone grafts allows definitive enlargement of narrowed foramina with consecutive root decompression as well as repositioning and intracanalicular decompression in cases of instability after lumbar disc surgery and in degenerative spondylolisthesis. Reconstruction of a hemilamina after hemilaminectomy and facet reduction allows reconstitution of the spinal canal and its posterior parts as well as direct treatment of intraforaminal pathology.

Adult↗
PubMed1989

Immunocytochemical evidence of progesterone receptors in human meningiomas.

The presence of progesterone receptors in meningioma tissue is demonstrated by use of highly specific monoclonal antibodies against the rabbit progesterone receptors which cross-react with human progesterone receptors in breast cancer cells, thus giving evidence of the existence of genuine progesterone receptors in human meningiomas.

Antibodies, Monoclonal↗
PubMed1989

Endocrine manipulation of meningiomas with medroxyprogesterone acetate. Effect of MPA on growth of primary meningioma cells in monolayer tissue culture.

Intracranial meningiomas from patients treated with medroxyprogesterone acetate as well as from untreated patients were studied in monolayer tissue culture with trials of in vitro hormonal modulation with medroxyprogesterone acetate. The following conclusions were drawn from investigations which comprise 37 cell culture assays: (a) tissue cultures of meningiomas inherit the disadvantages of loss of the progesterone receptor and frequent transformation to cells resembling fibroblasts after three to four passages. For these reasons, drug testing as well as the establishment of cell cultures that exhibit the characteristics of meningioma are impeded; (b) the progesterone receptor-content of the solid tumors does not reflect the response to medroxyprogesterone acetate-therapy in vitro; (c) medroxyprogesterone acetate-pretreated meningiomas showed sufficient in vitro growth in 38%, and untreated meningiomas grew well in 56% of the cases; (d) medroxyprogesterone acetate-induced inhibition or delay of growth was observed in 35%. These findings have resulted in criticism with respect to the value of meningioma tissue cultures for trials of hormonal manipulation and it is thought that another method, which consists of immunostaining of cycling cells, and has been tested in another study, may be superior to cell culture assays with respect to evaluation of the effect of hormonotherapy in meningiomas. Medroxyprogesterone acetate holds an interesting position because it reduces cell growth in some meningiomas in vitro.

Antigens, Surface↗
PubMed1988

Hormonotherapy of meningiomas with medroxyprogesterone acetate. Immunohistochemical demonstration of the effect of medroxyprogesterone acetate on growth fractions of meningioma cells using the monoclonal antibody Ki-67.

The effect of medroxyprogesterone acetate (MPA) on growth fractions of ex vivo meningiomas is demonstrated in using the Ki-67 monoclonal antibody in three cases of meningiomas operated on in two stages and in meningioma specimens from a group of eight patients operated on in one single stage after MPA therapy. Growth fractions in samples from five meningioma patients not treated with MPA were determined for comparison. In the three cases of two-stage operation of the tumors, the percentage of Ki-67-positive cells in meningioma tissue was lower by a factor of 6, 5, and 3, respectively, after MPA therapy. In meningioma specimens from patients receiving no MPA therapy, Ki-67-positive cells were present in 1.02 +/- 0.48%; in samples from MPA-treated tumors the percentage of Ki-67-positive cells was 0.41 +/- 0.40 (different at p less than 0.02 [Wilcoxon's test]). In comparison to our previously published data on untreated meningiomas analyzed for progesterone receptors (PR), MPA significantly reduced the PR activity. There was no obvious correlation between PR activity and potential suppression of the tumor growth fraction. It is concluded that MPA is attractive because it reduces the growth fractions of most meningiomas and might be suitable for adjuvant hormonotherapy.

Antibodies, Monoclonal↗
PubMed1987

Endocrine manipulation of meningiomas with medroxyprogesterone acetate. Effect of MPA on receptor status of meningioma cytosols.

Fifteen patients with intracranial or spinal meningiomas have been treated with the semisynthetic progestational agent medroxyprogesterone acetate (MPA, Depo-Provera) prior to surgical removal of the tumors in order to investigate the influence of MPA on the progesterone receptor (PR) status of meningioma cytosols. MPA acted as a competitive binder to meningioma-PR: The mean PR values were 15.6 fmol/mg protein (range 0-69) and 338.3 fmol/g tumor (range 0-1190), respectively. In comparison, mean PR values of our untreated meningioma series (n = 58) were 54.9 fmol/mg protein (range 0-586) and 2813 fmol/g tumor (range 0-17,168), respectively. In cases of two-stage resection of meningiomas MPA significantly decreased PR activity in the cytoplasm of meningioma cells. We conclude that MPA binds to meningioma PRs, however, its effect on the growth rate of meningiomas has still to be elucidated.

Cytosol↗
PubMed1987

Failure to demonstrate a vasoconstrictive effect of vasopressin on the internal carotid and middle cerebral arteries: a transcranial ultrasound Doppler study.

Vasopressin (AVP) was infused into four healthy human volunteers to explore by Doppler ultrasound the vasoconstrictive action of AVP on the internal carotid (ICA) and the medial cerebral artery (MCA, transcranial Doppler technique). Although AVP levels rose to 74.2 pg/ml (+/- 13 pg, SEM) no significant changes of flow velocity were observed in the ICA as well as the MCA. There was no effect on the pulsatility index of the MCA velocity profile indicating that peripheral vascular resistance remained unchanged during AVP infusion. These results do not support an effect of AVP at high physiological levels on the vascular diameters of the ICA, MCA and cerebral arteriolar system in humans.

Adult↗
PubMed1987

Clinicopathological relations of cerebral cavernous angiomas: observations in eleven cases.

Eleven cases of cerebral cavernous angiomas (cavernomas) were observed within a period of 3 years. Two patients presented with cerebral hemorrhage, five with epilepsy, three each with a progressive focal neurological deficit, and one with papilledema. The unruptured lesions had a heterogeneous density on computed tomography with relatively little contrast enhancement. Two lesions contained major cysts. In one of these cases, the cyst measured 5.5 cm in diameter, had an enhancing membrane, and was surrounded by brain edema. Angiography did not show hypervascularity in any instance. During exploration and histological processing, special attention was paid to signs of previous silent hemorrhages and to the degree of encapsulation of the lesion. Iron deposits (signs of previous hemorrhages) were seen to varying degrees inside all cavernomas as well as in the surrounding gliotic cerebrum, and a causal relation between iron deposits and epileptic seizures seems likely. Encapsulation was minimal with the ruptured cavernomas and particularly prominent with the cystic lesions. The membrane of the giant cystic lesion with peripheral brain edema had a histological structure similar to that of the membranes of chronic subdural hematomas. It is suggested that continuous growth of cavernoma cysts is the result of recurrent hemorrhages from sinusoids of the malformation and from the neocapillary network of the cyst membranes.

Adolescent↗
PubMed1986

Estrogen and progestin receptors in acoustic and spinal neurilemmomas. Clinicopathologic correlations.

Estradiol and progestin receptors were studied in 20 patients with neuraxial Schwann cell tumors, and their presence was correlated to the clinicopathologic features and the amount of preoperative corticosteroid therapy. Based on an arbitrary cutoff value of 200 fmol per gram of tumor as indicative of a positive receptor value in breast cancer, 4 and 13 of the neurilemmoma tissue samples could be considered as positive for estrogen and progesterone receptors, respectively. Whereas there was no convincing correlation between the estrogen and progestin receptor activity and the age, sex, or menopausal status of the patients, overweight patients had significantly higher estrogen and progestin binding values. The correlation between the amount of preoperative prednisone therapy and the amount of [3H]estradiol and [3H]promegestone binding revealed no dose relationship. Correlating [3H]estradiol and [3H]promegestone content with the histologic type of the schwannomas (Antoni types A and B, respectively), we were not able to draw conclusions, because of the predominance of Antoni type A over Antoni type B tissues in our material. The necessity of nuclear receptor assays, ligand specificity testing, and in vitro studies is stressed as a prerequisite for answering the questions whether neurilemmomas contain genuine sexual steroid hormone receptors and whether these receptors are regulated via an estrogen-estrogen-receptor system as is the case in classical sexual steroid hormone target tissues.

Adult↗
PubMed1979

Primary intraventricular oligodendrogliomas.

Two cases of primary intraventricular oligodendrogliomas which were successfully removed by a transventricular approach using microtechniques are presented. Oligodendrogliomas in this location are very rare. The literature is reviewed.

Adolescent↗
PubMed1979

Intracerebral ciliated epithelial cyst.

The authors describe a case of hemispheric brain cyst of possible neuroectodermal origin, presenting as a frontotemporoparietal mass lesion. The etiologic aspects of intracranial neuroepithelial cysts are discussed.

Adult↗
PubMed1979

Metastatic chordoma.

The authors present two cases of vertebral chordomas with widespread metastases. The literature is reviewed and the metastatic potential of chordomas is analysed.

Adult↗