Biomedical subjects

U Meier

Publications and source records attributed to U Meier.

At least 37 records · Page 2Linked to original sources

PubMed2004

[Predictors of outcome in patients with normal pressure hydrocephalus].

Despite emerging knowledge over 40 years, the postoperative results after shunt implantations in patients diagnosed for normal pressure hydrocephalus (NPH) did not improve significantly during the last decade. For that reason predictors have to be identified in order to predict preoperatively the course of disease. From 1982 until 2000 we examined in a prospective study 200 patients diagnosed for NPH. From the patients, who were surgically treated by a shunt implantation we could reexamine 155 (78%) in a meantime interval of seven month after the operation. The NPH was graduated according to the results of the intrathecal infusion test in an early state NPH (without brain atrophy) and late state NPH (with brain atrophy). In our study, we focussed the attention on the possible predictors: patients age, length of disease, clinical signs--like gait ataxia, dementia and bladder incontinence, aetiology idiopathic/secondary as well as implanted valve type and the value of resistance to cerebrospinal fluid outflow. To measure the outcome we used the NPH-Recovery-Rate, as statistical test the Chi-square according to Pearson. In 80 patients with an early stage NPH (without cerebral atrophy) a short course of disease (< 1 year), a just slight distinct of dementia and an implanted Miethke-Dual-Switch valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only a minimal relevance for the outcome. Those 75 patients with a late state NPH (with cerebral atrophy) had a better outcome when dementia was not present, the outflow resistance was above 20 mm Hg*min/ml, the CSF tap-test was positive and a Miethke-Dual-Switch valve was implanted.

Age Factors↗

PubMed2003

Is there a correlation between operative results and change in ventricular volume after shunt placement? A study of 60 cases of idiopathic normal-pressure hydrocephalus.

In patients with communicating or normal-pressure hydrocephalus, ventricular volume decreases following implantation of differential pressure valves. We implanted hydrostatic (Miethke dual-switch) valves in 60 patients with normal-pressure hydrocephalus (NPH) between September 1997 and December 2001. The patients underwent CT 1 year after operation, and we measured the Evans index. Although 83% of the patients showed no change in ventricular volume as assessed by this index, 72% nevertheless showed good to excellent and 16% satisfactory clinical improvement, while 12% showed no improvement. Moderate or marked reduction in ventricular size was observed in 17%, of whom 40% of these patients showed good to excellent and 20% satisfactory clinical improvement; 40% showed unsatisfactory improvement. The favourable outcome following implantation of a hydrostatic shunt thus did not correlate with decreased ventricular volume 1 year after operation, better outcomes being observed in patients with little or no alteration in ventricular size than in those with a marked decrease. Postoperative change in ventricular volume in NPH thus does not have the same significance as in patients with high-pressure hydrocephalus.

Aged↗

PubMed2003

Is decreased ventricular volume a correlate of positive clinical outcome following shunt placement in cases of normal pressure hydrocephalus?

It is well known that in patients with communicating hydrocephalus or normal pressure hydrocephalus, ventricular volume decreases following implantation of differential pressure valved shunts. Hydrostatic valves (Miethke dual-switch valves) were implanted in 60 normal pressure hydrocephalus patients at Unfallkrankenhaus Berlin between September 1997 and September 2001. One year postoperatively, these patients underwent CT scan, and their ventricular size was ascertained using the Evans index. Although 77% of these patients showed no postoperative change in ventricular volume, 65% nonetheless showed good to excellent clinical improvement, 13% satisfactory improvement and 22% no improvement. A moderate reduction in ventricular size was observed in 17% of the patients in our cohort. 40% of these patients showed good to excellent clinical improvement, 20% satisfactory improvement, and 40% unsatisfactory improvement. A marked reduction in ventricular size was observed in 6% of our patients. Of these latter patients, 50% showed good to excellent outcomes, while 50% had unsatisfactory outcomes. The favorable outcomes following implantation of a hydrostatic shunt in patients with normal pressure hydrocephalus did not correlate with decreased ventricular volume one year after operation. Better clinical outcomes were observed in patients with little or no alteration in ventricular size than in patients with a marked decrease in ventricular size. Postoperative change in ventricular volume should be assessed differently for patients with normal pressure hydrocephalus than in patients with hypertensive hydrocephalus.

Cerebral Ventriculography↗

PubMed2003

The ICP-dependency of resistance to cerebrospinal fluid outflow: a new mathematical method for CSF-parameter calculation in a model with H-Tx rats.

The international accepted calculation methods concerning the 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 t during and after the infusion. The comparison of the pressure rise On(p) during the infusion and the descent Off(p) after the infusion in the same pressure level allows to construct all formulas for the compliance C(p) and resistance R(p). The simultaneous measurement of the resistance and complications during a single investigation allows minimizing the patient's exertion. In contrast to the classical methods it is not necessary that the ICP reach 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. We proved our mathematical method by the use of a dynamic infusion test in ten H-Tx rats without hydrocephalus and five hydrocephalic H-Tx rats. For that we are able to take the non-linearity of the CSF resorption into consideration.

Animals↗

PubMed2003

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

Neurosurgical therapy aims to minimize the secondary brain damage after a severe head injury. This includes the evacuation of an intracranial space occupying bleeding, the reduction of intracranial volumes, in hematocephalus an external ventricular drainage, and the conservative therapy in order to influence an increased intracranial pressure (ICP) and a decreased p(ti)02. When conservative treatment fails to act a decompressive craniectomy might be successful in lowering ICP. From September 1997 until August 2001 we operated on 439 patients with severe head injuries. 50 patients (11%) were treated by means of a decompressive craniectomy. The prognosis after decompression depends on the clinical signs and symptoms on admission, the patients age and the existence of major extracranial injuries. Our guidelines for an indication for decompressive craniectomy after failure of conservative interventions and evacuation of space occupying hematomas include a patients age below 50 years without multiple trauma, a patients age below 30 years in the presence of major extracranial injuries, a severe brain swelling on CT scan, the exclusion of a primary brainstem lesion or injury and the intervention before irreversible brainstem damage and secondarily while monitoring ICP and p(ti)02 in an interval up to 48 hours after the accident before irreversible brainstem damage or generalized brain damage has occurred.

Adult↗

PubMed2003

[Shunt operation versus endoscopic ventriculostomy in normal pressure hydrocephalus: diagnostics and outcome].

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 October 2001 we operated on 79 patients diagnosed for normal pressure hydrocephalus. Diagnosis was established by means of the intrathecal lumbal or ventricular infusion test, the cerebrospinal fluid tap test and MRI-CSF flow studies pre- and post-operatively. In 60 patients (76 %) we implanted a ventriculo-peritoneal shunt (Miethke Dual-Switch valve), and in 15 patients (19 %) 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 we compared the operative results of both patient groups. Immediately after the operation the results are the same for both treatments. In the follow-up examination after 12 and 27 months patients who underwent a ventriculostomy showed a better outcome, but the underdrainage rate was higher. Concerning the operation related complications the shunt treatment leaded to 10 revisions (17 %) because of four infections (7 %), two shunt insufficiencies (3 %), two overdrainages (3 %), two catheter dislocations (3 %). The ventriculostomy leaded to one case with a pneumatocephalus (7 %) and one ischemic thalamic lesion (7 %). In both operation methods we saw cases of underdrainages, three after valve implantation (5 %) and two after ventriculostomy (13 %). In that patients we performed a change of the implanted valve with a lower pressure level or rather an implantation of a valve system in the two cases who underwent a ventriculostomy. In patients with a pathologically increased resistance to CSF outflow in the lumbal infusion test a shunt implantation with the Miethke Dual-Switch valve is indicated. Patients whose outflow resistance is increased in the ventricular infusion test are suspected for a functional interventricular stenosis and should be treated by means of an endoscopic assisted ventriculostomy.

Cerebrospinal Fluid Shunts↗

PubMed2003

[Outcome predictors in patients with normal pressure hydrocephalus].

Despite the accumulation of knowledge over the years, the postoperative results of shunt implantation in patients with normal pressure hydrocephalus (NPH) have shown little improvement. This means that reliable predictors of the course of the disease need to be identified. In a prospective study carried out between 1982 and 2000 we re-examined 155 (78%) of 200 NPH patients treated by shunt implantation, 7 months after their operation. On the basis of the results of the intrathecal infusion test NPH was graded early stage (no brain atrophy) or late stage (brain atrophy). We looked at the following factors as possible predictors: patient's age, disease duration, idiopathic or secondary aetiology, clinical signs such as gait ataxia, dementia and urinary incontinence, results of spinal tap, valve type and valve infection, and resistance to cerebral spinal fluid outflow and postoperative changes in ventricular size. As a measure for outcome we used the NPH recovery rate, and the Pearson chi-square test for statistical evaluation. 80 patients with early stage NPH, a history < 1 year, absence of dementia and an implanted Miethke dual-switch valve proved to be significant predictors of a positive outcome. Outflow resistance proved to have only minimal impact on outcome. The 75 patients with late-stage NPH had better outcome when dementia was absent, outflow resistance was > 20 mmHgmin/ml, the CSF tap test was positive, and a Miethke dual-switch valve was implanted.

Atrophy↗

PubMed2003

GeRTiSS: Generic Real Time Surgery Simulation.

Minimally invasive surgery is a technique that permits interventions through very small incisions. This minimises the patients' trauma and permits a faster recovery in comparison with classical surgery. The disadvantage of this surgery technique, though, is its complexity, requiring a high training effort of the surgeon. In this paper, we present a general surgery simulator for training surgeons in minimally invasive surgery. The application allows to create environments and interaction modes very similar to those encountered in real surgical interventions. The virtual environments are optionally composed of an actual patient's organs the intervention on which one desires to practice in a beforehand manner, or of synthetically generated organs with arbitrary pathologies. The intervention is carried out by means of haptic interfaces with force feedback, providing the surgeon with a sense of touch, a fundamental element of all types of surgery.

Computer Simulation↗

PubMed2002

[Acupuncture in diseases of the locomotor system. Status of research and clinical applications].

Acupuncture has been used for over 2000 years for a wide variety of complaints with minimal side effects. Based on the experience in Chinese medicine and the anticipated positive effects, acupuncture has been widely accepted in Western medicine as well. Some clinical evidence supports the efficacy of acupuncture treatment, but randomized controlled trials have been conducted for only a few of all possible locomotive disorder indications, and the results have been equivocal. Other indications have not yet been systematically studied, and application is based on clinical experience and consensus among practitioners. One of the outcomes on which consensus appears to exist is that 10-20 sessions are generally necessary, and that initial improvement can be expected to occur by the 10th treatment. Rigorous trials should be conducted to improve clinical validity and provide scientific proof of the efficacy of acupuncture. Clinical trials like the German Acupuncture Trials (gerac), funded by the German health insurance companies, have been launched with the aim of furthering knowledge in this area.

Acupuncture Therapy↗

PubMed2002

[Acupuncture in the treatment of locomotive disorders - status of research and situation regarding clinical application].

Acupuncture Therapy↗

PubMed2002

Five years experience with gravitational shunts in chronic hydrocephalus of adults.

OBJECTIVE: Gravitational shunts for management of chronic hydrocephalus are supposed to avoid or at least to reduce the risk of overdrainage. In order to find out if this hypothesis is correct, we did a prospective study and analysed the results of a series of 185 hydrocephalic adults, treated by using gravitational shunts. For the few cases in whom overdrainage occurred, we wanted to establish the reason for it. Especially it should be proven or excluded that overdrainage was caused by shortcomings of the principle of gravitational shunts. Another goal was to compare post-shunting changes of the ventricular size with clinical outcome. A comparably large study has not yet been published. METHODS: 185 adult patients who suffered from chronic hydrocephalus were shunted between 1996-2000, either using the combination of an adjustable Codmann Hakim Valve & Miethke Shunt Assistant (35 patients) or a Miethke Dual Switch Valve (150 patients). The clinical course of each patient has been followed until the end of 2000. Average follow-up time was 26 months (range 6-60 months). RESULTS: 88% of our patients were shunt responders, 70% had a good or excellent outcome. Overdrainage occurred in only 4%. It turned out that this complication was not a failure of the concept of gravitational shunts, but the result of a wrongly estimated intraperitoneal pressure. After shunting the ventricular size was reduced only marginally. In 92% of the patients the Evans-Index decreased less than 20% after the shunt insertion, but 69% of these patients had a good or excellent outcome. The most obvious difference comparing pre- and postoperative imaging was a better visibility of the high apical sulci after shunting. CONCLUSION: In our series gravitational shunts proved to be effective in preventing overdrainage. The 4% negative exceptions are mainly avoidable. There was no correlation between outcome and ventricular size reduction, and as a rule ventricular size was only marginally reduced.

Aged↗

PubMed2002

The ICP-dependency of resistance to cerebrospinal fluid outflow: a new mathematical method for CSF-parameter calculation in a model with H-TX rats.

The international The simultaneous measurement of the resistance and compliance during a single investigation minimizes the patients exertion. In contrast to the classical method it is not necessary that the ICP reaches a plateau. Our mathematical method diverges with t he description of a pressure dependent slope of the function for the resistance from the static examination models. We proved our mathematical method by the use of a dynamic infusion test in 10 H-Tx rats without hydrocephalus and five hydrocephalic H-Tx rats. For that we are able to take the non linearity of the CSF resorption into consideration.

Animals↗

PubMed2002

The importance of the intrathecal infusion test in the diagnosis of normal pressure hydrocephalus.

The intrathecal infusion test is a reliable method in diagnosing normal pressure hydrocephalus. Between May 1982 and January 2000 we investigated 300 patients suspected of having normal pressure hydrocephalus (NPH) by carrying out an intrathecal infusion test in a constant flow technique. The resistance to cerebrospinal fluid outflow (R(out)) in the intrathecal infusion test was the main criterion of grouping patients into those with normal pressure hydrocephalus or those with cerebral atrophy. A further differentiation into early stage and late stage was made by measuring the compliance (C(p)) - this being the secondary criterion. In 162 patients (54%) the diagnosis of NPH could be confirmed. Of these, 154 patients (95%) underwent a shunt operation. Graduation of NPH and cerebral atrophy following the results of the infusion test at an early stage and an advanced stage allow the conclusion of prognostic evaluations about the course of disease to be made. Patients with NPH in an early stage report in the follow up an improvement of their symptoms after a shunt operation in 65 percent of cases, and those with advanced stage NPH, in 50 percent of cases. The computer aided infusion test allows a reliable differentiation between patients with NPH and those with cerebral atrophy.

Atrophy↗

PubMed2002

Endoscopy of intracranial cysts in the adult patient.

In this study we report about our experience in surgical therapy of patients with intracranial supratentorial cysts. The main interest herein lies in the difference between conventional surgery and the endoscopic approach. Since 1997 in the Unfallkrankenhaus Berlin 4 male and 4 female patients with intracranial cysts aged between 21 and 66 have been treated surgically. The intracranial endoscopy was performed in 6 patients. The initially complained, mostly unspecific, symptoms diminished post operatively and in the follow-up. As complications a transient hemiparesis and an aseptic bone necrosis have to be mentioned, the latter after use of conventional surgery. In clear diagnostic cases an operation of intracranial cysts seems appropriate. Both surgical methods, open and endoscopic approach, are appropriate. To avoid complications due to greater surgical wounds the endoscopic method should be preferred.

Adult↗

PubMed2002

Altered fatty acid composition of lung surfactant phospholipids in interstitial lung disease.

Deterioration of pulmonary surfactant function has been reported in interstitial lung disease; however, the molecular basis is presently unclear. We analyzed fatty acid (FA) profiles of several surfactant phospholipid classes isolated from large-surfactant aggregates of patients with idiopathic pulmonary fibrosis (IPF; n = 12), hypersensitivity pneumonitis (n = 5), and sarcoidosis (n = 12). Eight healthy individuals served as controls. The relative content of palmitic acid in phosphatidylcholine was significantly reduced in IPF (66.8 +/- 2.5%; means +/- SE; P < 0.01) but not in hypersensitivity pneumonitis (78.5 +/- 1.8%) and sarcoidosis (78.2 +/- 3.1%; control 80.1 +/- 0.7%). In addition, the phosphatidylglycerol FA profile was significantly altered in the IPF patients, with a lower relative content of its major FA, oleic acid, at the expense of saturated FA. In the phosphatidylcholine class, a significant correlation between the impairment of biophysical surfactant function and decreased percentages of palmitic acid was noted. We conclude that significant alterations in the FA profile of pulmonary surfactant phospholipids occur predominantly in IPF and may contribute to the disturbances of alveolar surface activity in this disease.

Adult↗

PubMed2002

The grading of normal pressure hydrocephalus.

PATIENTS AND METHOD: During a period of 15 years we investigated 200 patients suspected of normal pressure hydrocephalus (NPH) by means of an intrathecal infusion test. In 107 patients (54%) the diagnosis of a normal pressure hydrocephalus could be confirmed. For the evaluation of the course of disease we used the Black-Grading-Scale for shunt assessment [1] and the clinical grading for chronic hydrocephalus (Kiefer-scale) [4] pre- and postoperatively as well as in a follow-up examination seven months after surgical treatment. The aim of our study was to find out a quick and easy-to-handle bed-side examination for the grading of NPH. DISCUSSION: The Black-Grading-Scale does not allow to distinguish between patients in an unchanged condition and those with a worsening of their symptoms. Therefore this scale is useful for patients with an obstructive hydrocephalus but not for those with a NPH. In our opinion the clinical grading of Kiefer [4] seems to be the most reliable scale for the grading and long term follow-up of a normal pressure hydrocephalus. CONCLUSION: Our own created NPH-Recovery-Rate is based on the clinical grading for chronic hydrocephalus (Kiefer-scale) [4]. It allows the interindividual comparison between the courses of disease in patients with normal pressure hydrocephalus.

Atrophy↗

PubMed2001

A new approach for the real-time simulation of tissue deformations in surgery simulation.

Simulation of the behaviour of elastic objects in real time is one of the present objectives of computer graphics. One of its fields of application lies in virtual reality, mainly in surgery simulation systems. Models used for the construction of objects with deformable behaviour in computer graphics are known as deformable models. These have two conflicting characteristics: interactivity and movement realism. The deformable models developed up till now have promoted one characteristic to the detriment of the other. In this paper, a new approach is proposed based on boundary element methods (BEM). This is characterised by a positive equilibrium between speed and realism and great robustness. These properties along with the experimental results described in this paper permit one to assert that establishing deformable models with BEM is a reliable method to model objects in virtual reality environments for surgery simulation. In addition to that, the required elasticity parameters could be obtained experimentally through the use of a pig's liver.

Algorithms↗

PubMed2001

The importance of the intrathecal infusion test in the diagnostic of normal-pressure hydrocephalus.

OBJECTIVE: The intrathecal infusion test is a reliable method for diagnosing normal-pressure hydrocephalus (NPH). METHODS: Between May 1982 and January 1997, we investigated 200 patients suspected of having NPH by carrying out an intrathecal infusion test with a constant-flow technique. The resistance to cerebrospinal fluid outflow in the intrathecal infusion test was the main criterion for grouping patients into those with NPH or those with cerebral atrophy. A further differentiation into early stage and advanced stage was made by measuring the compliance, this being the secondary criterion. RESULTS: In 107 patients (54%), the diagnosis of NPH could be confirmed. Of these, 102 patients (95%) underwent a shunt operation. Graduation of NPH and cerebral atrophy following the results of the infusion test at an early stage and an advanced stage allows prognostic evaluations about the course of disease to be made. Patients with NPH at an early stage reported an improvement of their symptoms in the follow-up after a shunt operation in 65% of cases, while 50% of those with advanced-stage NPH reported improvement. CONCLUSION: The computer- aided infusion test allows a reliable differentiation between patients with NPH and those with cerebral atrophy.

Atrophy↗