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A Obwegeser

Publications and source records attributed to A Obwegeser.

8 recordsLinked to original sources
PubMed2000

Vascular endothelial growth factor (VEGF) is elevated in brain tumor cysts and correlates with tumor progression.

Vascular endothelial growth factor (VEGF), a key regulatory protein in neoangiogenesis, is strongly expressed in a variety of primary brain tumors, particularly malignant gliomas. In previous studies, high levels of VEGF were also reported in tumor cysts of glioblastomas. Using an ELISA method we measured the concentration of VEGF in matched samples of aspiration fluid from tumor cysts and serum. Samples were collected from 14 patients with primary brain tumors of various histology (six glioblastomas, one protoplasmatic astrocytoma, two pilocytic astrocytomas, one ependymoma, one meningioma, and three craniopharyngiomas) and two patients with solitary cystic brain metastases from adenocarcinomas of the lung. Aspiration fluids of tumor cysts from all patients revealed high VEGF levels ranging between 882 and 1,263,000 pg/ml, which were 2 to more than 2,000 times higher than the corresponding serum levels. Maximum VEGF levels were detectable in cyst fluids from recurrent glioblastoma. Serum VEGF levels ranged between 125 and 716 pg/ml and did not differ from serum levels in 145 healthy volunteers. In a single patient with metastatic lung cancer the concentration of VEGF in serum and cyst fluid was determined during disease progression. During 60 days of follow-up VEGF concentrations in the cyst fluid collected by puncture of an Ommaya reservoir increased 650-fold, while serum levels remained rather constant. These findings indicate that immunoreactive VEGF is produced at the tumor site and abundantly released into the cyst fluid of primary and metastatic brain tumors. Interestingly, this abundant local release is not reflected in serum VEGF levels, even in the case of very high VEGF concentrations in tumor cysts. Thus, VEGF may be biologically relevant for the formation of tumor cysts in brain tumors and correlates with local disease progression.

Adolescent↗
PubMed1998

Three-dimensional computer assisted magnetic resonance imaging for neurosurgical planning in parasagittal and parafalcine central region tumors.

Usually, conventional magnetic resonance spin echo images (MRI) are sufficient to establish the diagnosis of intracranial pathology. Planning and executing a neurosurgical procedure requires the ability of the neurosurgeon to transform these two-dimensional MRI into a three-dimensional (3-D) virtual image of the pathology and the surrounding neuronal anatomy. Such mentally performed transformations after sequential observation of the individual two-dimensional slices (i.e., MRI and angiography) may be virtual tasks that are very difficult or sometimes impossible to achieve. Using 3-D MRI data sets and a semiautomatic computer assisted segmentation technique, we tried to simulate intraoperative situs-based 3-D MRI reconstructions of parasagittal and parafalcine central region tumors. The MRI reconstructions were integrated into the neurosurgical planning procedure as an additional tool. They proved to be an important adjunct in determining the distinct anatomy of the intracranial pathology in its relation to the surrounding and overlying brain and vascular (especially venous) anatomy. With 10 patients with central region parasagittal and parafalcine tumors, we found that the 3-D MRI reconstructions revealed additional information compared to conventional cross-sectional images and had an influence on neurosurgical planning and strategy, improving neurosurgical performance and patient outcome.

Humans↗
PubMed1998

Uptake and kinetics of 14C-labelled meta-tetrahydroxyphenylchlorin and 5-aminolaevulinic acid in the C6 rat glioma model.

Meta-tetrahydroxyphenylchlorin (m-THPC) and 5-aminolaevulinic acid (5-ALA) are two second-generation photosensitizers which are currently under investigation for photodynamic therapy (PDT) and photodynamic diagnosis (PDD). So far, the experience with these photosensitizers for use within brain tumours is limited. We examined the distribution and retention of 14C-labelled m-THPC and [14C]5-ALA in the rat C6 glioma brain tumour model. After intraperitoneal injection of m-THPC (71,909 d.p.m. microl(-1); 0.16 mg ml(-1) m-THPC; 0.3 mg kg(-1)), the following activities were found after 36 h: brain tumour 223,664 d.p.m. g(-1), brain contralateral to the tumour side 2567 d.p.m. g(-1), liver 369,959 d.p.m. g(-1) and skin 55,197 d.p.m. g(-1); 100,000 d.p.m. corresponding to 0.22 microg of m-THPC. After 7 days, the concentration of m-THPC decreased to 76,277 d.p.m. g(-1) in tumour and 635 d.p.m. g(-1) in brain. The radioactivity after intravenous administration of [14C]5-ALA (23,079 d.p.m. microl(-1); 40 mg ml(-1); 120 mg kg(-1)) increased within 15 min (59,634 d.p.m. g(-1) in tumour, 17,427 d.p.m. g(-1) in brain); after 8 h only a small amount (3653 d.p.m. g(-1) in tumour) remained. Brain adjacent to the tumour was also found to have a higher uptake of 5-ALA. This study provides basic information for the use of m-THPC and 5-ALA in brain tumours. Because of the different pharmacokinetic and toxicological profile, we recommend m-THPC for PDT and 5-ALA for PDD. Clinical trials now have to prove the superior phototoxic properties of these second-generation photosensitizers.

Aminolevulinic Acid↗
PubMed1996

Quadriplegia after lumbar disc surgery. A case report.

STUDY DESIGN: Case report. OBJECTIVE: To report a case of quadriplegia after surgery in the prone position for a herniated lumbar disc. SUMMARY OF BACKGROUND DATA: Ischemia in the vascular territories of the vertebral arteries after back surgery in the prone position is rare. Degenerative changes of the cervical spine or decreased blood flow to the head with mechanical vessel obstruction during extreme neck movements, systemic hypotension, and thromboembolism have mostly been implicated in the pathogenesis. METHODS: The case of a 33-year-old man undergoing surgery for an unilateral single level disc herniation at L4-L5 is presented. Within a few hours after surgery he developed quadriplegia and signs of occipital lobe dysfunction. He underwent magnetic resonance imaging investigation. Therapy included arterial blood pressure control, low molecular dextran, dexamethasone, bladder catheterization, and physiotherapy. RESULTS: Magnetic resonance imaging demonstrated intramedullary ischemic changes in the cervical spinal cord and at the borderline between anterior and posterior circulation. Outcome after 2 years is fair regarding the severe initial deficit-the patient walks alone with a cane and bladder function is under control. He is employed in a sedentary job. CONCLUSIONS: The authors believe that a temporary mechanical occlusion of a vertebral artery led to stasis, formation of thrombi, and subsequent embolism in the vertebrobasilar vascular territory. Extreme head rotation and neck extension is to be avoided in the prone position.

Adult↗
PubMed1996

Photodynamic therapy in neurosurgery: a review.

Photodynamic therapy (PDT) has been investigated extensively, both experimentally and clinically, as an adjunctive treatment in the neuro-oncological field. It is based on the more selective accumulation of a photosensitizer in malignant than normal tissue with low systemic toxicity. Subsequent light activation induces photo-oxidation, followed by selective tumour destruction via vascular and direct cellular mechanisms. Malignant brain tumours carry a lethal prognosis with a median survival of 15 months despite surgery, radiotherapy and chemotherapy. PDT is therefore a logical therapeutic concept for brain tumours infiltrating into normal brain. In this review, all the available data on patients treated with haematoporphyrin derivative-mediated PDT are critically analysed. Over 310 patients have been reported in the literature suffering from primary or recurrent malignant brain tumours which were treated with PDT following tumour resection in open clinical phase I/II trials. This number includes 58 patients treated at our own institution. Variations in the treatment protocols make evaluation scientifically difficult; however, there is a clear trend of increased median survival after surgical resection and one single photodynamic treatment. PDT is generally well tolerated and side effects consist of moderate increased intracranial pressure and prolonged skin sensitivity to direct sunlight. The current available data indicate that PDT is a safe treatment, which is well tolerated by the patients and yields an improvement in survival of those with malignant brain tumours. Conclusive information can be expected from controlled clinical trials which are currently being designed. The results raise the hope that PDT will be a valuable addition to the armamentarium for the treatment of cerebral malignancies.

Biopsy↗
PubMed1995

Therapy of glioblastoma multiforme: a cumulative experience of 10 years.

PURPOSE: Comparison of the effect of different therapeutic modalities on survival time of patients with glioblastoma multiforme operated on during the last decade (1980-1990). PATIENTS AND METHODS: The records of 157 consecutive patients with the histological diagnosis of glioblastoma multiforme were analysed for survival with respect to age of patients, extent of surgery, influence of re-operation and adjuvant postoperative treatment. The latter included fractionated radiotherapy, chemotherapy (BCNU. CCNU with Vincristine) and photodynamic therapy (PDT). RESULTS: Analysis of variance showed a significant effect for survival after macroscopically radical surgery (p = 0.005), postoperative radiotherapy (p < 0.001), chemotherapy (p < 0.01). Low age (p < 0.05) and a postoperative Karnofsky performance score (KPS) > or = 60 (p < 0.001) had a positive influence: the site of tumour and pre-operative presence of seizures had no significant influence (p > 0.1) on survival time. CONCLUSION: We conclude that the current adequate management of glioblastoma multiforme should include surgical resection followed by adjuvant treatment such as radiotherapy and chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗