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Biomedical subjects

V Seifert

Publications and source records attributed to V Seifert.

At least 19 recordsLinked to original sources
PubMed2006

Active secretion of S100B from astrocytes during metabolic stress.

In patients suffering from cerebrovascular diseases and traumatic brain damage, increases in serum levels of protein S100B are positively correlated with the severity of the insult. Since high concentrations of S100B have been shown to exert neurotoxic effects, the objective of this study was to characterize the regulatory mechanisms underlying control of S100B release from astrocytes. To that end, we analyzed the kinetics and amount of S100B release in correlation with regulation of S100B gene expression in an in vitro ischemia model. Astrocyte cultures were treated with combined oxygen, serum and glucose deprivation, serum and glucose deprivation or hypoxia alone for 6, 12 and 24 h, respectively. While oxygen, serum and glucose deprivation triggered the most rapid release of S100B, serum and glucose deprivation provoked comparable levels of released S100B at the later time points. In contrast to oxygen, serum and glucose deprivation and serum and glucose deprivation, hypoxia alone elicited only marginal increases in secreted S100B. Parallel analysis of extracellular lactate dehydrogenase and the number of viable cells revealed only moderate cell death in the cultures, indicating that S100B was actively secreted during in vitro ischemia. Interestingly, S100B mRNA expression was potently downregulated after 12 and 24 h of oxygen, serum and glucose deprivation, and prolonged oxygen, serum and glucose deprivation for 48 h was associated with a significant reduction of S100B release at later time intervals, whereas lactate dehydrogenase levels remained constant. Our data suggest that secretion of S100B during the glial response to metabolic injury is an early and active process.

Animals↗
PubMed2006

Development of a 3-D convolution/superposition algorithm for precise dose calculation in the skull.

In this paper an algorithm for calculating 3-D dose distributions within the brain is introduced and adapted to the demands of modem radiosurgery. The dose calculation with this model is based on a 3-D distribution of the primary photon intensity which is calculated with a ray casting algorithm. A prelocated matrix takes into account field sizes as well as modifying elements as collimator positions (MLC), blocks, wedges and compensators. Monte Carlo precalculated monoenergetic kernels from 0.1 MeV to 50 MeV were at our disposal. The components of the spectrum were either determined by deconvoluting depth dose curves measured in water or analyzed with a Ge-Li detector system in the case of 60Co. The calculated fluence distribution has to be superposed to the complete kernel containing the spatial energy deposition. Inhomogeneities and tissue interface phenomena (rhoe, Z) have been investigated. The divergence of the rays and the curved surface of the patient are taken into account. Assuming homogenous media, it is possible to shorten the computation time by using the Fast Fourier Transformation (FFT) delivering a first overview within seconds. The algorithm was evaluated and verified under specific conditions of small fields as used in radiosurgery and compared to dose measurements and Monte Carlo calculations. In using both the fast algorithm (FFT) for mainly homogenous conditions on one hand and the very precise superposition for inhomogeneous cases on the other, this algorithm can be a very helpful instrument especially for critical locations in the skull.

Algorithms↗
PubMed2005

Xanthogranuloma of the sellar region.

The incidence of diagnosed xanthogranuloma of the sellar region is very low [1, 2, 5, 6]. We report about two cases 1) in a 57-year-old female and 2) in a 5-year-old boy. In both cases radiographic findings revealed an inhomogeneous, contrast enhancing sellar lesion. Histopathology showed the typical features of a xanthogranuloma of the sellar region with cholesterol clefts, lympho-plasmacellular infiltrates, marked hemosiderin deposits, multinucleated foreign body giant cells around cholesterol clefts, accumulation of macrophages and only small epithelial cell clusters [6]. As xanthogranuloma of the sellar region are rarely diagnosed we want to draw attention to this rather unusual diagnosis.

Child, Preschool↗
PubMed2005

Quality assurance in stereotactic radiosurgery/radiotherapy according to DIN 6875-1.

The new DIN ('Deutsche Industrie-Norm') 6875-1, which is currently being finalised, deals with quality assurance (QA) criteria and tests methods for linear accelerator and Gamma Knife stereotactic radiosurgery/radiotherapy including treatment planning, stereotactic frame and stereotactic imaging and a system test to check the whole chain of uncertainties. Our existing QA program, based on dedicated phantoms and test procedures, has been refined to fulfill the demands of this new DIN. The radiological and mechanical isocentre corresponded within 0.2 mm and the measured 50% isodose lines were in agreement with the calculated ones within less than 0.5 mm. The measured absorbed dose was within 3%. The resultant output factors measured for the 14-, 8- and 4-mm collimator helmet were 0.9870 +/- 0.0086, 0.9578 +/- 0.0057 and 0.8741 +/- 0.0202, respectively. For 170 consecutive tests, the mean geometrical accuracy was 0.48 +/- 0.23 mm. Besides QA phantoms and analysis software developed in-house, the use of commercially available tools facilitated the QA according to the DIN 6875-1 with which our results complied.

Quality Control↗
PubMed2005

Development of an interactive graphical user interface for therapy simulation.

Because of the ongoing development to more complex non-coplanar techniques in radiotherapy, the use of modem computer graphics while designing a dose plan becomes increasingly essential and more important. In this paper, we describe a concept to simulate 3D conformal treatment techniques on the computer. All important components of the treatment device and relevant patient structures are mapped to an internal model, which allows simulation of motion sequences as well as the interactive adjustment of treatment parameters. The intention of this user interface is to save time by using mainly graphical modules in the optimization process instead of running through the dose calculation every time.

Algorithms↗
PubMed2005

Hydrocephalus due to superior sagittal sinus thrombosis.

The great variability of clinical appearance is one of the main features of superior sagittal sinus thrombosis. However, hydrocephalus associated with cerebral sinus thrombosis is rare. We report on a patient presented with thunderclap headache, accompanied by nausea, vomiting, and drowsiness. Lumbar puncture ruled out subarachnoid hemorrhage, whereas CT revealed marked hydrocephalus. In addition, magnetic resonance venography then confirmed the diagnosis of cerebral sinus thrombosis. It is a rare occurrence but clinically important, since it entails disastrous sequels if unrecognized, and hydrocephalus is treated in the usual fashion with ventricular drainage.

Humans↗
PubMed2005

Technique and image quality of intraoperative indocyanine green angiography during aneurysm surgery using surgical microscope integrated near-infrared video technology.

OBJECTIVE: To describe the technical integration of indocyanine green (ICG) near-infrared technology into the optical path of the surgical microscope and to report on the image quality achieved by this method. We hypothesized that ICG angiography permits a simple and quick intraoperative assessment of vessel patency and aneurysm occlusion after clip placement. METHODS: A special arrangement of filters was designed to allow the passage of near-infrared light required for the excitation of ICG fluorescence (700-850 nm) from a modified microscope light source into the surgical field and the passage of ICG fluorescence (780-950 nm) from the surgical field back into the optical path of the surgical microscope (Carl Zeiss, Oberkochen, Germany). Thus, ICG angiography could be completely performed with a surgical microscope. 20 patients with intracranial aneurysms were included in the technical evaluation of the new method. RESULTS: Image quality and spatial resolution were excellent and permitted a real-time assessment of vessel patency and aneurysm occlusion if the structures of interest were visible to the surgeon's eye under the microscope, including perforating arteries with a diameter of less than 1 millimeter. In 1 patient, vessel occlusion by the clip was found and in 1 case residual filling of the aneurysm was diagnosed. Both cases could be treated by clip correction within 2 minutes after primary placement of the clip. In all cases, the intraoperative findings correlated with the postoperative digital subtraction angiography. CONCLUSIONS: ICG angiography using a surgical microscope is valuable for the intraoperative imaging of arterial and venous flow in all visible vessels including small perforating arteries. The simplicity of the method and the speed with which the investigation can be performed indicate that this technique may help to improve the quality and outcome of surgical procedures and reduce the need for intra- or postoperative angiography in selected cases.

Adult↗
PubMed2005

Importance of diffusion-weighted imaging in the diagnosis of cystic brain tumors and intracerebral abscesses.

OBJECTIVE: It is often difficult to decide whether a cystic brain lesion is a tumor or an abscess by means of conventional MRI techniques. The immediate diagnosis of a brain abscess is important for the patient's outcome. Our goal was to study the ability of diffusion-weighted imaging and calculation of the apparent diffusion coefficient (ADC) to differentiate between these two pathologies. PATIENTS AND METHODS: Ten patients (five men, five women) with cystic brain lesions were examined with MRI. The ADC maps were calculated for each subject and the ADC value of each lesion was measured. Histology revealed glioblastoma multiforme in six patients and abscess in four patients. RESULTS: All brain abscesses showed markedly hyperintense signal changes on diffusion-weighted imaging, whereas the appearance of glioblastoma varied from slightly hyperintense to hypointense signal conversion. The mean ADC value calculated in the six patients with cystic brain tumor was: 2.05 x 10 (-3) mm(2)/s (1.38-2.88 x 10 (-3) mm(2)/s). The mean ADC value of the four patients with brain abscess was: 0.57 x 10 (-3) mm(2)/s (0.38-0.77 x 10 (-3) mm(2)/s). CONCLUSION: Diffusion-weighted imaging and calculation of ADC maps constitute a helpful tool to differentiate between cystic brain tumors and brain abscesses.

Adult↗
PubMed2005

[Recommendations for the management of patients with aneurysmal subarachnoid hemorrhage].

After SAH, primary and secondary complications are frequent and often require neurosurgical interventions to avoid secondary brain damage. The authors of the present paper have summarized the available data about the treatment modalities often used for patients with SAH. The present recommendations have been developed as a neurosurgical and neuroanestesiological consensus. Evidence from prospective, randomized, double blind, placebo-controlled studies support grade A recommendations (standard) for the prophylaxis and treatment of cerebral vasospasm with oral Nimodipine in good grade patients. For intravenous Nimodipine or for oral nimodipine treatment in poor grade patients, available data only support grade C recommendations (options). Despite the lack of data supporting standards (grade A) or guidelines (grade B), avoidance and rigorous treatment of hypotension and hypovolemia remains the mainstay in the prophylaxis and treatment of a delayed ischemic neurological deficit (DIND). Prophylactic hypervolemia or prophylactic hypertension and hypervolemia was shown to be ineffective in reducing symptomatic vasospasm and improving outcome (grade B). Therapeutic hypertensive hypervolemic hemodilution is recommended as a treatment of symptomatic vasospasm but no prospective studies are available (grade C recommendation). Suggested target values for moderate triple-H-therapy are CPP 80- 120 mmHg (MAP 90-130), CVP > 7 mmHg and Hk 0.25-0.40. Balloon angioplasty should be considered for treatment of DIND cause by focal, proximal cerebral vasospasm. There is no evidence supporting the routine use of antifibrinolyticals, steroids or anticonvulsive prophylaxis. Clinical data indicate that current prophylaxis and treatment of cerebral vasospasm is still insufficient and aggressive triple-H-therapy is associated with an increased incidence of complications.

Angioplasty, Balloon↗
PubMed2004

Robot-assisted navigated endoscopic ventriculostomy: implementation of a new technology and first clinical results.

BACKGROUND: Important landmarks in the evolution of advanced neurosurgical techniques during the past decades include microneurosurgery, neuro-endoscopy and its minimally invasive nature, as well as neuronavigation and advanced intra-operative imaging. With conventional neuroendoscopic techniques, e.g. free-hand endoscopy or the use of mechanical or pneumatic holding devices, a definitive and controlled movement of the endoscope within the brain does depend on the experience and manual skill of the individual neurosurgeon. Therefore, the development of robotic systems to assist surgeons in performing complex neurosurgical procedures is a growing field of interest. METHOD: With the precision robot "Evolution 1" (U.R.S. Universal Robot Systems, Schwerin, Germany) a new neurosurgical tool has just become available for the precise steering of instruments within the cranium. After preclinical anatomical as well as precision studies the system was used for robot-assisted navigated endoscopic third ventriculostomies in six patients with hydrocephalus related to aqueductal stenosis. FINDINGS: All robot-assisted navigated endoscopic procedures were successfully completed. The time for the registration procedure and setup of the robot decreased from 60 min. for the first procedure down to 30 min. The time for the surgical part of the neuro-endoscopic procedure itself ranged from 17 to 35 min. During all procedures no system-related complications occurred. INTERPRETATION: The use of robotic technology for neuro-endoscopic third ventriculostomies is a major step towards the controlled movement of the neuro-endoscope within the cranium. The start up procedure and calibration of the robot is still time consuming, but the real operation time is comparable to free hand neuro-endoscopy. The steering of the endoscope is facilitated and the precision of the endoscopic movements is noteworthy.

Adolescent↗
PubMed2004

Clivus lymphoma.

Lymphoma as primary infiltration of the skull base, especially the clivus, is unusual and rare. However, increasing incidence of atypical lymphoma manifestations have been reported. As cranial base surgery becomes more common, it is important to be aware of lymphoma as a possible differential diagnosis of clivus lesions. This case presents a primary malignant lymphoma of the clivus, histologically confirmed after intra-operative MRI-guided transnasal-transsphenoidal biopsy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2004

Protein S-100b as serum marker for prediction of functional outcome in metastatic spinal cord compression.

BACKGROUND: To evaluate the significance of protein S-100b as a serum marker for the prediction of functional outcome in the event of symptomatic spinal cord compression due to epidural metastases. METHOD: 34 patients with paresis due to metastatic spinal cord compression were included in this prospective study. Venous blood samples for protein S-100b were taken after admission and regularly after operative decompression. The individual time course of protein S-100b levels was correlated with the clinical outcome by means of motor function. Outcome was considered to be favourable in case of neurological improvement and preservation or retrieval of walking ability whereas non-improvement or further neurological deterioration without restoration of function of ambulation was regarded to be unfavourable. FINDINGS: Patients with favourable outcome had serum levels of S-100b which were either normal all the time or which were initially increased but normalised within 2 to 3 days. Patients with unfavourable outcome, however, had increased levels throughout which showed either a further increase or only a slow decrease within approximately two weeks (p=0.0001). INTERPRETATION: These preliminary results suggest that, analogous to cerebral disorders, protein S-100b might be a promising serum marker to predict functional outcome in symptomatic spinal cord compression.

Biomarkers↗
PubMed2004

Severe delayed diffuse cerebral vasospasm and cerebral infarctions following spinal subdural hemorrhage.

BACKGROUND: We report a rare case of severe delayed cerebral vasospasm with cerebral infarctions after spinal subdural hemorrhage. CASE REPORT: A 56-year-old woman presented with an acute onset of paraplegia. MR-imaging revealed an extensive intraspinal hemorrhage reaching from T1 to L1. The hematoma was evacuated via a T8-laminectomy. At the 7th postoperative day the patient developed visual disturbances. MR-scanning revealed extensive infarctions and cerebral angiography showed severe diffuse vasospasms. INTERPRETATION: This case demonstrates that cerebral vasospasm may be caused by a spinal subdural hemorrhage, supporting the hypothesis that cerebral vasospasm may be triggered by factors from a remote site and that a direct contact of blood clots with the vessel is not mandatory.

Cerebral Infarction↗
PubMed2004

Cerebral venous sinus thrombosis manifesting as bilateral subdural effusion.

Three patients with bilateral subdural effusion, an exclusive manifestation of cerebral venous sinus thrombosis (CVST), are presented. A possible explanation of this rare occurrence is provided, and the differential therapeutic strategies are discussed. We propose to consider CVST in cases of subdural effusions of obscure origin. Appropriate imaging studies should not be delayed if there is suspicion of sinus thrombosis to enable adequate therapy to be started as soon as possible.

Aged↗
PubMed2004

Tissue at risk concept for endovascular treatment of severe vasospasm after aneurysmal subarachnoid haemorrhage.

OBJECTIVE: To report a case of severe vasospasm after subarachnoid haemorrhage (SAH) where "tissue at risk" was identified by magnetic resonance imaging (MRI), and to demonstrate the haemodynamic consequences with either resolution of the perfusion-diffusion mismatch by balloon angioplasty or evolution of an infarct. METHODS: A 45 year old women with SAH underwent surgical treatment of a ruptured middle cerebral artery (MCA) aneurysm. On day 3 she became obtunded and developed a right hemiparesis. Diffusion weighted (DWI) and perfusion weighted (PWI) imaging were done before and after transluminal balloon angioplasty (TBA) of multifocal proximal vasospasm. RESULTS: The initial MRI revealed no DWI lesion but PWI showed a severe perfusion deficit of 6.7 to 16.4 seconds in the complete left MCA territory. Digital subtraction angiography confirmed severe segmental narrowing of left C1 and M1. The spastic segments were successfully dilated by TBA. Follow up MRI showed that the PWI-DWI mismatch resolved in the anterior and middle MCA territory with no tissue infarction, whereas in the terminal dorsal MCA territory a severe mismatch remained and cerebral infarction evolved. CONCLUSIONS: PWI/DWI can identify tissue at risk for infarction in severe vasospasm following SAH. This may allow selection of patients for angioplasty and the monitoring of treatment effects.

Angioplasty, Balloon↗
PubMed2004

Experimental approaches to evaluate endothelin-A receptor antagonists.

A large body of evidence suggests a substantial role of the endothelin (ET) system in the pathophysiology of a variety of disease states, mainly of the cardiovascular system. Recently bosentan, an ET receptor antagonist, has received approval by the Food and Drug Administration (FDA) for use in pulmonary artery hypertension. The ET system may also be involved in cerebrovascular disorders such as stroke and, most notably, development of cerebral vasospasm following subarachnoid hemorrhage. The pathophysiological mechanisms contributing to the development of a cerebral vasospasm after subarachnoid hemorrhage may be taken as a paradigm to explore mechanisms leading to secondary ischemic brain damages in a variety of insults such as stroke and trauma. The present review provides the evidence to evaluate ET receptor antagonists for potential prophylactic and therapeutic use in patients suffering from subarachnoid hemorrhage. The rationale to develop selective ETA receptor antagonists is given with respect to basic and applied studies. This may be useful to better define the desired profile of action of a given compound, and it may also help to design appropriate preclinical and clinical trials, most desirably in close cooperation with pharmaceutical companies and neurosurgical departments.

Animals↗
PubMed2003

Pertreatment radiation induced oedema causing acute hydrocephalus after radiosurgery for multiple cerebellar metastases.

BACKGROUND: Most complications of radiosurgery occur after 6-12 months and some long term complications up to after 5-10 years. Although severe, immediate side effects are rare, we report a patient who shows that this possibility should be taken into account when large volumes are treated especially in the posterior fossa. CASE REPORT: A patient was treated with radiosurgery for multiple brain metastases, of which 5 were located in the posterior fossa. Deterioration occurred, radiosurgery was halted abortion and CT showed acute hydrocephalus caused by a significant edema in the posterior fossa, not present in an MR examination performed some 6 hours earlier. After intubation and external ventricular CSF drainage, a permanent shunt was inserted, the edema resolved, and the patient recovered to her pretreatment condition within 10 days. The remaining metastases were treated during the first session and MR images showed the hydrocephalus resolved when all the radiated tumors had significantly decreased in size. INTERPRETATION: Care should be taken when treating with radiosurgery patients posterior fossa metastases and signs of compressed CSF pathways. Exceptionally, an acute radiation induced edema could result in a block of the CSF pathways, necessitating a surgical intervention. Prophylactic shunt insertion or hospitalization the night following the treatment should be considered.

Acute Disease↗