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Biomedical subjects

U Meier

Publications and source records attributed to U Meier.

At least 55 records · Page 3Linked to original sources
PubMed2001

Surgical management of single and multiple brain metastases: results of a retrospective study.

BACKGROUND: Advancement in diagnosis and treatment of various cancer entities led to an increasing incidence of brain metastases in the last decades. Surgical excision of single and multiple brain metastases is one of the central treatment options beside radiotherapy, radiosurgery and chemotherapy. To evaluate the benefit of surgery with/without whole-brain radiation therapy (WBRT) in single brain metastases and the influence of image guidance for brain metastases resection, 104 patients were retrospectively evaluated for post-operative outcome. PATIENTS AND METHODS: Between January 1994 and December 1999 150 patients were surgically treated for brain metastases at the Department of Neurosurgery at the Technical University of Dresden. Outcome could be evaluated in 104 patients with respect to special treatment strategies and survival time (69 patients with single and 35 patients with multiple lesions). RESULTS: Most metastases originated from primary lung and breast tumours. Karnofsky performance score improved on average by 10 after surgery. The extent of the extracerebral tumour burden was the main influence on survival time. Patients' age below 70 years was combined with prolonged survival time (median survival time, MST: 4.5 months vs. 7 months). Patients with solitary cerebral metastasis had a MST of 16 months, whereas patients with singular lesions had a MST of 7 and 4 months, depending on the extent of the extracerebral tumour growth. Additional post-operative WBRT with 30 Gy was combined with an increase in MST in patients with single brain metastasis (surgery + WBRT: MST 13 months; surgery only: MST 8 months). In addition, the rate of recurrent cerebral tumour growth was distinctly higher in the non-WBRT group. Neuronavigation did not significantly improve post-operative survival time. In 80% of patients extracerebral tumour growth limited patients' survival. CONCLUSION: Surgery is an initial treatment option in patients with single and multiple brain metastases especially with large tumours (> 3 cm). Post-operative WBRT seems to prolong survival time in patients with single brain metastasis by decreasing local and distant tumour recurrence. Neuronavigational devices permit a targeted approach. Multiple processes can be extirpated in one session without prolonging the hospitalisation time for the patient. However, neuronavigational devices cannot assure complete tumour resection.

Aged↗
PubMed2001

Alteration of fatty acid profiles in different pulmonary surfactant phospholipids in acute respiratory distress syndrome and severe pneumonia.

Impairment of alveolar surfactant function has been documented in the acute respiratory distress syndrome (ARDS) and in severe pneumonia (PNEU); however, the underlying mechanisms are not completely understood. In the current report we present a detailed analysis of fatty acid (FA) profiles of different surfactant phospholipid (PL) classes isolated from bronchoalveolar lavage fluids (BALF) and large surfactant aggregates (LSA) from mechanically ventilated patients with ARDS (n = 8), ARDS associated with lung infection (ARDS + PNEU, n = 9), and PNEU (n = 22). Healthy volunteers served as control subjects (n = 8). PLs were isolated by thin-layer chromatography, and the FA profile of each PL class was assessed by gas chromatography. In addition, the minimal surface tension (gamma min) of untreated LSA and of LSA after supplementation with additional dipalmitoylated phosphatidylcholine (DPPC) was analyzed (pulsating bubble surfactometer). As compared with control LSA, the percentage of palmitic acid in phosphatidylcholine (PC) was significantly decreased in all patient groups (ARDS 63.0 +/- 2.0%, ARDS + PNEU 64.6 +/- 4.9%, PNEU 65.6 +/- 1.5%, control subjects 80.1 +/- 1.7%), whereas the relative amount of unsaturated species in PC increased significantly in all groups. Phosphatidylglycerol (PG) and phosphatidylinositol (PI) presented similar FA profiles in control subjects, but differed in the patients. The FA pattern of sphingomyelin (SPH) and phosphatidylethanolamine (PE) displayed only minor changes under conditions of respiratory failure. As compared with control subjects a highly significant increase of gamma min from near zero to approximately 16 mN/m was observed in all patients and was found to be inversely correlated to the percentage of palmitic acid in PC of LSA or BALF. Accordingly, values for gamma min were significantly improved upon secondary supplementation of LSA with DPPC up to control values. We conclude that marked changes in the FA composition of the predominant surfactant PL classes occur, both in ARDS triggered by nonpulmonary events and PNEU. The marked reduction of palmitic acid in the PC fraction may be related to changes in surfactant function under these conditions.

Adult↗
PubMed2001

[Pressure-dependent outflow resistance in cerebrospinal fluid dynamics: evaluation a calculation model for diagnosis of normal pressure hydrocephalus in an animal experiment with H-Tx rats].

The internationally accepted methods of calculating cerebrospinal fluid dynamics proceed from the assumption of a pressure-independent resistance to CSF outflow. Our new model focusses on the pressure-dependency of this resistance. In it, we monitor the entire pressure course over time, p(t) during and after infusion. A comparison of the pressure rise, On(p), during infusion, and the decrease, Off(p), to the same pressure level, permits the creation of all the formulas for C(p) and R(p). The simultaneous measurement of resistance and compliance during a single intervention allows us to minimize patient exertion. In contrast to the classical methods, it is not necessary for the ICP to reach a plateau. Our mathematical model differs from the static examination model by describing a pressure-dependent slope of the function for the resistance. This has been demonstrated in a study using H-Tx rats. In this way, we are able to take the non-linearity of the CSF resorption into consideration.

Animals↗
PubMed2001

[The importance of neuronavigation in endoscopic operations in neurosurgery].

Intracranial endoscopy as minimal invasive surgery for the treatment of hydrocephalus and intracranial cysts cannot be disregarded after 10 years of clinical practicing. The advantages are low traumatization of brain tissue and good visual control of the operation field. Neuronavigation qualifies as a method of increased operation safety for lesions which are deep seated or difficult to access. A combination of both systems partially neutralizes the respective disadvantages. On the one hand, the neuronavigation ensures the endoscopic approach up to the intracranial caverns and especially supports the endoscopy in cases of bad vision or pathologic anatomy. Endoscopy, on the other hand, enables the surgeon to recognize discrepancies and mistakes of the neuronavigation due to optical control. Increased expenses and time and staff requirements are counterbalanced by the increased cumulated operation safety. An advantageous side-effect of the combination of neuronavigation and intracranial endoscopy is the high learning potential for assistants. For all these reasons the application of neuronavigation in intracranial endoscopy is considered very important and strongly recommended.

Brain↗
PubMed2000

Clinical experiences with the dual-switch valve in patients with normal pressure hydrocephalus.

In patients with normal pressure hydrocephalus (NPH) we compared the postoperative results reference to the implanted valve type. In 117 patients diagnosed with normal pressure hydrocephalus there was placement of 47 Cordis Standard valves (CSV), 20 Cordis Orbis Sigma valves type I (OSV) and 50 Miethke Dual-switch valves (DSV). Ninety-five patients (36/19/40) were re-evaluated. Normal pressure hydrocephalus was graduated according to the results of the intrathecal infusion test in an early and late stage. There were no statistical differences in mechanical and infective complications between the different valve types. We found significant differences in overdrainages and subdural hematomas. Two patients (6%) with a CSV, 3 patients (16%) with an OSV and 1 patient (3%) with a DSV developed clinical symptoms due to this. The course of disease in patients with NPH is influenced by the stage of disease--degree of cerebral atrophy--and also by the implanted valve type. The great amount of overdrainage complications and subdural hematomas in the Cordis Orbis Sigma valve group may be an argument against this valve. Our clinical experiences with the Miethke Dual-switch valve show that this hydrostatic valve may be advantageous for patients with NPH.

Equipment Design↗
PubMed2000

Endoscopic ventriculostomy versus shunt operation in normal pressure hydrocephalus: diagnostics and indication.

In contrast to shunt operation the indication for an endoscopic ventriculostomy in patients diagnosed for normal pressure hydrocephalus is not scientifically established. From September 1997 to March 1999 we operated on 36 patients diagnosed for normal pressure hydrocephalus. Diagnosis was established by means of the intrathecal lumbar or ventricular infusion test, the cerebrospinal fluid tap test and MRI-CSF flow studies pre- and post-operatively. In 30 patients (83%) we implanted a ventriculo-peritoneal shunt, and in 6 patients (17%) we performed the endoscopic assisted third ventriculostomy. With our created NPH recovery rate and use of the clinical grading for normal pressure hydrocephalus created by Kiefer and Steudel we compared the operative results of both patient groups. In patients with a pathologically increased resistance to CSF outflow in the lumbar infusion test a shunt implantation is indicated. Patients whose outflow resistance is increased in the ventricular infusion test but with a physiological lumbar infusion test are suspected for a functional aqueduct stenosis and should be treated by means of an endoscopic assisted ventriculostomy.

Cerebrospinal Fluid Pressure↗
PubMed2000

The use of decompressive craniectomy for the management of severe head injuries.

The aim of Neurosurgical care is to minimise the secondary brain damage that occurs after a severe head injury. This includes the evacuation of an intracranial space occupying haematoma, the reduction of intracranial volume, external ventricular drainage with hydrocephalus, and conservative therapy to reduce intracranial pressure (ICP) and to maintain tissue oxygen p(ti)O2. When conservative treatment fails, a decompressive craniectomy might be successful in lowering ICP. From September 1997 until April 1999 we operated on 128 patients with severe head injuries. 19 patients (15%) were treated by means of a decompressive craniectomy. The prognosis after decompression depends on clinical signs and symptoms on admission, patients' age and the existence of major extracranial injuries. Our guidelines for decompressive craniectomy after failure of conservative intervention and evacuation of space occupying hematomas included: a patient's age below 50 years without multiple trauma or a patient's age below 30 years in the presence of major extracranial injuries; severe brain swelling on CT scan (primary brainstem injuries were excluded). In 8 patients conservative 1TU treatment had failed.

Adolescent↗
PubMed2000

[Clinical experience with various shunt systems in normal pressure hydrocephalus].

In patients with normal pressure hydrocephalus in the late stage conventional differential valves have the disadvantage that they open abruptly while changing the body position to the vertical line and that they can therefore induce a suction on the ventricles of the atrophic brain. Can these disadvantages and overdrainage complications be minimized by hydrostatic valves? In 117 patients diagnosed for normal pressure hydrocephalus we have implanted 47 Cordis Standard Valves (CSV), 20 Cordis Orbis Sigma Valves Type I (OSV) and 50 Miethke Dual Switch Valves (DSV). 95 patients (36/19/40) could be re-evaluated by means of a control examination. Normal pressure hydrocephalus was graduated according to the results of the intrathecal infusion test in an early and late stage. According to our NPH-Recovery-Rate and to the clinical grading of normal pressure hydrocephalus by Kiefer and Steudel we compared the post-operative results of each group of patients. There were no statistical differences in mechanical and infectious complications between the different valve types. We found significant differences in overdrainage and subdural hematomas. 4 patients (11%) with a CSV, 5 patients (26%) with an OSV and 2 patients (5%) with a DSV had a decrease of the ventricular width visualised in the CT. Of those patients 2 (6%) with a CSV, 3 patients (16%) with an OSV and 1 patient (3%) with a DSV developed clinical symptoms. The course of the disease in patients with normal pressure hydrocephalus is influenced by the stage of the disease--degree of cerebral atrophy--and also by the implanted valve type. The high amount of overdrainage complications and subdural hematomas in the Cordis Orbis Sigma Valve Type I group is an argument against its use. Our clinical experiences with the Miethke Dual Switch Valve show that this hydrostatic valve is of advantage for patients with a normal pressure hydrocephalus.

Cerebrospinal Fluid Shunts↗
PubMed2000

Endoscopic ventriculostomy versus shunt operation in normal pressure hydrocephalus: diagnostics and indication.

In contrast to the shunt operation the indication for an endoscopic ventriculostomy in patients diagnosed for normal pressure hydrocephalus is not scientifically established. Between September 1997 and December 1999 we operated on 48 patients diagnosed for normal pressure hydrocephalus. The diagnosis was established by means of the intrathecal lumbar or ventricular infusion test, the cerebrospinal fluid tap test and MRI-CSF flow studies pre- and postoperatively. In 37 patients (77%) we have implanted a ventriculo-peritoneal shunt, and in 11 patients (23%) we performed the endoscopic assisted third ventriculostomy. With our created NPH recovery rate and use of the clinical grading for normal pressure hydrocephalus created by Kiefer and Steudel we compared the operative results of both groups of patients. In patients with a pathologically increased resistance to CSF outflow in the lumbar infusion test a shunt implantation is indicated. Patients whose outflow resistance is increased in the ventricular infusion test but with a physiological lumbar infusion test are suspected for a functional aqueduct stenosis and should be treated by means of endoscopic assisted ventriculostomy.

Cerebral Aqueduct↗
PubMed2000

[Violence in the school--imported or self-produced?].

The empirical results of the Bielefeld Research Project "Violence in Schools" provide information about the kind and frequency of violent behaviors of pupils, about a possible increase in the level of violence in German schools since the 1970s and about relevant risk factors inside and outside of the school which influence the number of violent acts committed by pupils. The identification of specific conditions in different areas of socialization makes it possible to determine to what degree violence is imported into the school from outside or is produced from within. On the basis of these findings, recommendations are made for the prevention of violence in schools.

Adolescent↗
PubMed2000

Strategies in management of ruptured aneurysms--own experiences with various therapeutical procedures in severe SAH.

A retrospective analysis of 58 patients with spontaneous SAH was conducted. 33 patients suffered on severe SAH, clinical grading IV and V (Hunt, Hess). 11 died without treatment due to decerebrate rigidity. 22 patients were treated, 16 underwent a clipping procedure and 6 were selected for endovascular coilembolization. A total of 14 SAH were associated with intracerebral, intraventricular or subdural hemorrhages. In fact of these in 10 patients first an evacuation of the haematoma or a ventricular drainage was necessary, two times combined with a decompressive craniectomy. In 4 patients the removal of haematoma was combined with clipping of aneurysm in one operation. After occlusion of aneurysm decompressive craniectomy was required in 3 patients, an evacuation of an intracerebral bleeding in 1 patient. 6 patients needed a permanent shunting system. The outcome according the Glasgow Outcome Score was: 4 died (GOS1), 12 were severely disabled (GOS3) and 6 were moderately disabled (GOS4).

Adult↗
PubMed1999

Multivisceral resection of advanced colorectal carcinoma.

BACKGROUND AND AIMS: In about 10% of patients with carcinoma of the colorectum, the tumour has already invaded contiguous organs or else inflammatory tumorous adhesions involving neighbouring structures are found. In such a situation, the question arises whether one should perform a multivisceral resection, the usefulness of which in terms of surgical risk and late oncological results have been investigated in the present study. PATIENTS AND METHODS: A total of 173 patients with colorectal carcinoma who underwent a multivisceral resection during the period between 1984 and 1995 are reported. Excluded from the study were patients with recurrent tumour or distant metastases. RESULTS: In the majority of cases (63%), the primary tumour originated in the sigmoid colon or rectum. In 102 patients, only a single neighbouring organ was additionally involved, while the remaining patients had involvement of two or more contiguous organs. In 140 patients, the resection was curative, while in the remaining patients an R1/2 situation presented. In the curative group, tumour infiltration was confirmed histologically in 55% of the cases, while in the remaining patients a peritumourous adhesion had mimicked tumour invasion. Postoperative surgical complications occurred in only 1.4% of the interventions, a figure identical to the incidence of complications seen with conventional limited operations. The same applied to the postoperative 30-day mortality rate of 3.6%. The 5-year survival rate of the overall group of patients undergoing multivisceral resection was 42%, that of the subgroup undergoing curative surgery was 51%, and that of the subgroup receiving only palliative resection was 0%. Calculation of the stage-related 5-year survival rates for Union Internationale Contra la Cancrum stage-II and stage-III tumours revealed figures of 58% and 43%, respectively. After non-extended resection, the respective survival rates were identical (60% and 41%). CONCLUSION: An identical surgical risk and survival rates for curative resection, equally as good as those seen with conventional, non-extended procedures, justify the liberal use of multivisceral resection in the surgical treatment of colorectal carcinomas directly invading neighbouring organs.

Abdominal Muscles↗
PubMed1999

Diagnostic in normal pressure hydrocephalus: A mathematical model for determination of the ICP-dependent resistance and compliance.

The internationally accepted calculation methods concerning cerebrospinal fluid dynamics proceed from a pressure independent resistance to cerebrospinal fluid outflow. In a new model we focus our attention on the pressure dependency of resistance. In our calculation model we are monitoring the complete pressure course p(t) over the time during and after the infusion. The comparison of the pressure rise On(p) during the infusion and the descent Off(p) after the infusion at the same pressure level allows one to construct all formulas for the compliance C(p) and resistance R(p). The computerized analysis of the results of the intrathecal infusion test using our mathematical computation leads to a simplification of this investigation. The simultaneous measurement of the resistance and compliance during a single investigation allows one to minimize the patient's discomfort. In contrast to the classical methods it is not necessary that the ICP reaches a plateau. Our mathematical method diverges with the description of a pressure dependent slope of the function for the resistance from the static examination models. For that we are able to take the non-linearity of the cerebrospinal fluid resorption into consideration.

Computer Simulation↗
PubMed1999

Signs, symptoms and course of normal pressure hydrocephalus in comparison with cerebral atrophy.

Between May 1982 and January 1997 we investigated 200 patients for normal pressure hydrocephalus (NPH) by performing an intrathecal infusion test. 168 patients (84%) presented with the clinical syndrome of gait ataxia, dementia and urinary incontinence, the so called Adams triad. In 107 patients (54%) the diagnosis of a NPH could be confirmed. Of these, 102 patients (95%) underwent a shunt operation. In a follow-up (7 month and 3 years later) we interviewed the patients or their relatives about the progression of the disease. At those time intervals we could evaluate the improvement after shunt operation or infusion test. In our experience gait ataxia is the guiding sign of NPH. Regarding dementia we could not find a significant difference compared to cerebral atrophy. Urinary incontinence can be characterized as a symptom of late stage NPH. The complete Adams triad should not be overestimated in differential diagnostic considerations. Subdivision of NPH into an early stage and a late stage allows one to conclude prognostic evaluations about the course of the disease. Patients with an early stage NPH reported at the follow-up an improvement of their symptoms after shunt operation in 65 percent and those with a late stage NPH in 50 percent. The computer aided infusion test allows a safe differentiation between patients with NPH and those with cerebral atrophy.

Ataxia↗
PubMed1999

Surfactant subtype conversion is related to loss of surfactant apoprotein B and surface activity in large surfactant aggregates. Experimental and clinical studies.

Conversion of the highly surface-active subtype of pulmonary surfactant known as large surfactant aggregates (LA) to small aggregates (SA) with poor surface activity has recently been shown to occur upon cyclic changes of the air-liquid interface area in vitro. By subjecting pooled rabbit bronchoalveolar lavage fluid (BALF) to this maneuver, we found that conversion of LA to SA was accompanied by a marked decline in the ability of the remaining LA fraction to reduce surface tension by adsorption and during film compression on a pulsating bubble surfactometer. SA obtained by centrifugation of noncycled rabbit BALF had a similar phospholipid (PL) but different neutral lipid (NL) composition than did the LA. Upon cycling, the increased formation of SA obliterated this difference. No substantial difference in the PL, NL, or fatty acid profile of LA was noted before and after cycling. In contrast, the content of surfactant apoprotein-B (SP-B) in the LA decreased dramatically to nearly undetectable levels during the cycling maneuver, and this decline in SP-B content was closely correlated with the decrease in proportional appearance of LA and loss of surface activity of this fraction. Reconstitution of LA with intact SP-B after cycling virtually fully restored the surface activity of this surfactant subtype. When comparing lavage samples from adults with acute respiratory distress syndrome (ARDS; n = 10) with samples from healthy controls (n = 11), we noted a marked reduction of SP-B in the LA fraction. There was a significant correlation between the SP-B content of the LA fraction and the relative percentage of LA in BALF or the lower surface activity of this surfactant subtype. We conclude that an SP-B-related loss of LA integrity and function may substantially contribute to the decline of this surfactant subtype and the loss of its surface activity during cycling in vitro and in clinical ARDS.

Adult↗
PubMed1999

[First experiences using microsurgical techniques for minimally invasive ventral interbody fusion of the lumbar spine (MINI-ALIF)].

Minimal invasive techniques recently have become more important in spine surgery. Ventral approaches for lumbar fusion techniques are known for a long time. Their disadvantages are their size and the associated trauma. Since the early nineties two schools of minimal invasive procedures were developed. On one hand surgeons developed laparascopic methods, on the other hand traditional ventral approaches were minimized and combined with microsurgical techniques, in a way that they offer all advantages of minimal invasive procedures. This technique widely known under the acronym MINI-ALIF, which stands for MINImal invasive Antero-Lumbar Interbody Fusion, was developed for retroperitoneal approaches to the segments L2/3, L3/4, L4/5 and for the transperitoneal approach to the segment L5/S1. Its advantages include reduced technical and personnel effort, minimal traumatized tissue, low blood-loss, short operating times and reduced rates of complications. Additionally the surgeon does not need to be experienced in laparascopic methods. The operation technique is explained and discussed from the neurosurgical point of view.

Humans↗
PubMed1999

[Quality securing procedures in neurosurgical operations. Experiences with intraoperative computed tomography and neuronavigation].

In the department of Neurosurgery of the Unfallkrankenhaus Berlin, experiences with neuronavigation and intraoperative computed tomography were acquired and reviewed on a descriptive basis. The main parameter for the evaluation was target point accuracy for the neuronavigation and image quality for the intraoperative ct. Additionally, both systems were evaluated about the requirement of time, staff and technical equipment. The analysis shows that both techniques are apted for quality control with the operation of intracranial lesions. Most problems with the handling of the new methods decreased with growing experience. On the technical aspect there are still problems with target accuracy for the neuronavigation and image quality for the ct-scans. However, solutions due to future technical improvement are perceived. The increase of time requirement is compensated with the rise of operation security. An even higher quality control is achieved with combination of both systems.

Brain↗