Biomedical subjects

U Meier

Publications and source records attributed to U Meier.

At least 19 recordsLinked to original sources

PubMed2007

[Idiopathic normal-pressure hydrocephalus. Flow measurement of cerebrospinal fluid using phase contrast MRI and its diagnostics importance].

AIM: The measurement of CSF flow in the aqueduct has been a focus of interest since the development of MR imaging (MRI) techniques for this purpose in diagnosing idiopathic normal-pressure hydrocephalus (iNPH).The purpose of this prospective study was to determine the ability of this diagnostic tool to replace invasive methods in establishing the diagnosis of iNPH. PATIENTS AND METHODS: Between January 2003 and April 2005, 61 patients with the Hakim triad of clinical symptoms and dilated ventricular systems underwent the intrathecal infusion test, cerebrospinal tap test, and phase-contrast MRI to measure CSF flow rate in the aqueduct. Shunted patients were controlled 12 months postoperatively. Pre- and postoperative clinical symptoms were evaluated with the Kiefer score. Outcome was calculated according to the NPH recovery rate. RESULTS: According to these criteria the patients were classified into groups of 41 with iNPH and 20 with brain atrophy. Of the iNPH patients, 39 were shunted and two did not agree to surgery. The mean Kiefer score of the shunted patients was statistically significantly lower after surgery. The aqueductal CSF flow rate of these patients was statistically analyzed and showed that a flow rate of more than 24.5 ml/min is 95% specific to iNPH. CONCLUSIONS: Measurement of the CSF flow rate in the aqueduct using phase-contrast MRI is a highly specific preselective method for diagnosing iNPH.

Adult↗

PubMed2006

Gravitational valves: relevant differences with different technical solutions to counteract hydrostatic pressure.

Two different technical principles of gravitational valves (G-valves) have been presented: counterbalancer and switcher G-valves. The objective of our prospective study was to look for clinically relevant differences between both. A total of 54 patients with normal-pressure hydrocephalus (NPH) were treated; 30 patients received an Aesculap-Miethke GA-Valve (GAV; counterbalancer), and in 24 patients an Aesculap-Miethke Dualswitch-Valve (DSV; switcher) was implanted. The opening pressure of the posture-independent valve was 5 cm H2O in both devices. The outcome was clearly better with the usage of the GAV than with the DSV. The frequency and severity of complications was pronounced in the DSV group. We recommend the Aesculap-Miethke-GAV valve with a low opening pressure in a posture-independent valve for patients with NPH.

Adult↗

PubMed2006

Predictors of outcome in patients with normal-pressure hydrocephalus.

From 1982 until 2000 we examined 200 patients diagnosed with normal-pressure hydrocephalus (NPH) in a prospective study. From the patients who were surgically treated by a shunt implantation we could re-examine 155 (78%) at a mean time interval of 7 months after the operation. NPH differed in severity 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 focused on the possible predictors: patient age; length of disease; clinical signs including gait ataxia, dementia, and bladder incontinence; idiopathic vs. secondary origin; implanted valve type and the resistance of the valve to cerebrospinal fluid outflow. In 80 patients without cerebral atrophy and a short course of disease (< 1 year), a slight amount of dementia and an implanted Miethke Dualswitch-Valve were significant predictors for a positive postoperative outcome. The outflow resistance measured in the intrathecal infusion test showed only minimal relevance for outcome. Seventy-five patients with cerebral atrophy had a better outcome when dementia was not present, outflow resistance was above 20 mmHg/mL/min, the CSF tap-test was positive, and a Miethke Dualswitch-Valve was implanted.

Cerebrospinal Fluid Shunts↗

PubMed2006

On the optimal opening pressure of hydrostatic valves in cases of idiopathic normal-pressure hydrocephalus: a prospective randomized study with 123 patients.

Does the opening pressure of hydrostatic shunts influence the clinical outcome for patients suffering from idiopathic normal-pressure hydrocephalus (NPH)? Between September 1997 and January 2003, 123 patients with idiopathic NPH were surgically treated by implanting a hydrostatic shunt at the Departments of Neurosurgery of the Unfallkrankenhaus Berlin and the University Homburg/Saar. As part of a prospective randomized study, all patients were examined preoperatively, postoperatively, and 1 year after the intervention. Forty-three percent of the patients showed a very good outcome, 25% good outcome, 20% fair outcome, and 12% poor outcome 1 year after the shunt implantation. Patients treated with an opening pressure rating of 50 mmH2O in the low-pressure stage of the gravitational valve showed a better outcome than those with an opening pressure of 100 or 130 mmH2O. According to present knowledge, hydrostatic shunts with an opening pressure of 50 mmH2O for the low-pressure stage are the best option for patients with idiopathic NPH. Due to the prompt switching function when the patient changes posture (lying down, standing, sitting, slanting etc.), the Miethke gravity-assisted valve (GAV) is more suitable in such cases than the Miethke Dual-Switch valve (DSV).

Adult↗

PubMed2006

First clinical experiences in patients with idiopathic normal-pressure hydrocephalus with the adjustable gravity valve manufactured by Aesculap (proGAV(Aesculap)).

OBJECTIVE: Improved clinical outcomes after implantation of a low pressure valve in patients with idiopathic normal-pressure hydrocephalus is usually achieved at the expense of a higher overdrainage rate. Can an adjustable valve with a gravitational unit provide optimal results? METHOD: In a prospective clinical outcome study conducted in the Unfallkrankenhaus Berlin, 30 patients with idiopathic normal-pressure hydrocephalus were treated surgically between June 2004 and May 2005 with the valve combination described above, and reexamination 3 months or 6 months postoperatively. RESULTS: Clinical outcome correlates with opening pressure level of the valve. Controlled adjustment of the valve from 100 mmH2O to 70 mmH2O, and then to 50 mmH2O after 3 months, permits optimum adaptation of the brain to the implanted valve without overdrainage complications. CONCLUSIONS: Advantages of this programmable gravity valve include: 1) the absence of unintentional readjustment through external magnets, and 2) the possibility of controlling the valve setting using an accessory instrument without the need for x-ray monitoring. A significant disadvantage is adjusting the valve after implantation. From the clinical point of view, this new "proGAV(Aesculap)" valve is a necessary development in the right direction, but at the moment it is still beset with technical problems.

Cerebrospinal Fluid Shunts↗

PubMed2006

Decompressive craniectomy for severe head injury in patients with major extracranial injuries.

Neurosurgical therapy aims to minimize secondary brain damage after a severe head injury. This includes the evacuation of intracranial space-occupying hematomas, the reduction of intracranial volumes, external ventricular drainage, and aggressive therapy in order to influence increased intracranial pressure (ICP) and decreased P(ti)O2. When conservative treatment fails, a decompressive craniectomy might be successful in lowering ICP. From September 1997 until December 2004, we operated on 836 patients with severe head injuries, of whom 117 patients (14%) were treated by means of a decompressive craniectomy. The prognosis after decompression depends on the clinical signs and symptoms at admission, patient age, and the existence of major extracranial injuries. Our guidelines for decompressive craniectomy after failure of conservative interventions and evacuation of space-occupying hematomas include: patient age below 50 years without multiple trauma, patient age below 30 years in the presence of major extracranial injuries, severe brain swelling on CT scan, exclusion of a primary brainstem lesion or injury, and intervention before irreversible brain stem damage.

Comorbidity↗

PubMed2006

Clinical outcome of patients with idiopathic normal pressure hydrocephalus three years after shunt implantation.

OBJECTIVE: To investigate the outcomes of surgical treatment of idiopathic normal pressure hydrocephalus (iNPH). PATIENTS AND METHODS: We prospectively investigated 51 patients treated for iNPH by insertion of a ventriculoperitoneal shunt with gravitational valve. RESULTS: The proportion of excellent, good, and satisfactory outcomes immediately following surgery was 80%; the same clinical outcome was later verified in 67% of patients on average of 34 months postoperatively. These results are similar to those reported in the literature. Ventricle volume decreased minimally during the course of treatment using Evans' index, which was concordant with recent literature and with current understanding of hydrocephalus treatment. CONCLUSIONS: A gravitational valve for treatment of iNPH is the logical implementation of current knowledge of the pathophysiology of this illness enabling us to solve the problem of cerebrospinal fluid drainage with the lowest possible opening pressure while simultaneously protecting from overdrainage. The use of programmable valves, in combination with a gravitational component, is the next evolutionary stage, potentially making revision operations unnecessary.

Adult↗

PubMed2006

Is it possible to optimize treatment of patients with idiopathic normal pressure hydrocephalus by implanting an adjustable Medos Hakim valve in combination with a Miethke shunt assistant?

A better course of the disease after implantation of a low-pressure valve in patients with idiopathic normal pressure hydrocephalus normally comes at the cost of a distinctly higher rate of overdrainage. Can combining an adjustable valve with a gravity unit produce optimization of treatment results? In a prospective observation of the course of the disease, 18 patients with idiopathic normal pressure hydrocephalus were surgically treated with the aforementioned valve combination during the period January to June 2004 at the Unfallkrankenhaus Berlin and examined after 6 and 12 months. The course of the disease correlates with the opening pressure level of the valve. The controlled setting of the valve from 100 mmH2O to 70 mmH2O, then to 50 mmH2O after 3 months permits the brain to adapt optimally to the implanted valve without complications from overdrainage. In our view, combining an adjustable differential pressure valve with a gravity unit currently represents the optimal treatment variant for patients with idiopathic normal pressure hydrocephalus. In the future, the gravity valve should also be adjustable.

Adult↗

PubMed2005

Microscale localized spectroscopy with a magnetic resonance force microscope.

Magnetic resonance force microscopy is combined with spin-echo spectroscopy to obtain spatially and spectrally resolved NMR signals of micrometer-scale objects. The experimental spatial resolution for the demonstration experiment on a sample consisting of Ba(ClO3)2.H2O and (NH4)2SO4 single crystals is 3.4 microm. The spectral resolution of 3.4 kHz is sample limited. Improvements in resolution and extensions of the method to more than one spatial dimension and to multidimensional spectroscopy are possible.

Algorithms↗

PubMed2005

The importance of major extracranial injuries by the decompressive craniectomy in severe head injuries.

Neurosurgical therapy aims to minimise 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 July 2004 we operated on 737 patients with severe head injuries. 103 patients (14%) 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 generalised brain damage has occurred.

Adult↗

PubMed2005

Gravity valves for idiopathic normal-pressure hydrocephalus: a prospective study with 60 patients.

OBJECTIVE: Are hydrostatic valves superior to conventional differential pressure shunts in patients with normal-pressure hydrocephalus, with regard to the postoperative results of treatment and possible complications? METHODS: From September 1997 to January 2002, 60 patients with idiopathic normal-pressure hydrocephalus were treated by surgical implantation of hydrostatic valve at the Unfallkrankenhaus Berlin. In a prospective study, the clinical examination and a CT examination were carried out preoperatively, postoperatively and 1 year after the operation. RESULTS: One year after the operation, the clinical picture was very good for 33% of the patients, good for 33% and satisfactory or poor for 17%, each, of the patients. 3 dislocations (5%) of ventricular or abdominal catheters and three valve infections were found as valve-independent. As valve-dependent complications, underdrainage was found in 4 patients (7%) and radiological signs of overdrainage in 2 patients (3%), while 1 patient (1.7%) showed symptomatic over-drainage. CONCLUSION: According to our experience, hydrostatic Dual-switch valves Aesulap are superior to conventional differential pressure shunts without an additional gravity unit especially with regard to the treatment of patients with idiopathic normal-pressure hydrocephalus, concerning both the postoperative results and the incidence of possible complications. A clinical improvement can be achieved for 83% of such patients.

Adult↗

PubMed2005

Does the ventricle size change after shunt operation of normal-pressure hydrocephalus?

OBJECTIVES: The aim of this study was to determine whether ventricular size correlates with a positive clinical outcome following shunt placement. Hydrostatic valves (Dual-Switch-Valves) were implanted in 80 patients with NPH at Unfallkrankenhaus Berlin between September 1997 and January 2002. One year postoperatively, these patients underwent computerized tomography scanning, and their ventricular size was ascertained using the Evans-Index. Among 80% of the patients who showed no postoperative change in ventricular volume, 59% nonetheless had good to excellent clinical improvements, 17% satisfactory clinical improvement, and 24% no improvement. Furthermore, a moderate reduction in ventricular size was observed in 14% of patients in this cohort. Among these, 36% experienced a good to excellent clinical improvement, 28% a satisfactory improvement, and 36% unsatisfactory improvement. A marked reduction in ventricular size was observed in 6% of the patients. Of this group, 60% demonstrated good to excellent outcomes, whereas 40% had unsatisfactory outcomes. Favourable outcomes following the implantation of a hydrostatic shunt in patients with NPH did not correlate with decreased ventricular volume 1 year after surgery. In fact, better clinical outcomes were observed in patients with little or no alteration in ventricular size, compared with those in patients with marked decrease in ventricular size. A postoperative change in ventricular volume should be assessed differently in patients with NPH compared with those suffering from hypertensive hydrocephalus.

Aged↗

PubMed2005

Real-time deformable models for surgery simulation: a survey.

Simulating the behaviour of elastic objects in real time is one of the current objectives of computer graphics. One of its fields of application lies in virtual reality, mainly in surgery simulation systems. In computer graphics, the models used for the construction of objects with deformable behaviour are known as deformable models. These have two conflicting characteristics: interactivity and motion realism. The different deformable models developed to date have promoted only one of these (usually interactivity) to the detriment of the other (biomechanical realism). In this paper, we present a classification of the different deformable models that have been developed. We present the advantages and disadvantages of each one. Finally, we make a comparison of deformable models and perform an evaluation of the state of the art and the future of deformable models.

Biomechanical Phenomena↗

PubMed2005

Experience with five different intervertebral disc spacers for cervical spondylodesis.

The ventral spondylodesis with autologeous bone graft for degenerative disease of the cervical spine bears the disadvantage of complications and heavy pain at the superior pelvic straight. To reduce these problems the intervertebral disc spacer was developed. Between September 1997 and January 2002 we operated on 207 patients suffering from degenerative disease -- osteochondrosis and/or disc prolapse -- of the cervical spine. Without any patient selection, e. g. according to a randomized sample, we implanted the different disc spacer by a ventral approach after microsurgical discectomy and removal of the dorsal osteophytes by a high-speed drill. The Titanium disc spacer by Aesculap, Weber, Intromed, and Medinorm were used in 66, 54, 52 and 18 cases and the Carbonium disc spacer of AcroMed in 17 cases. We evaluated the handling, X-ray contrast, costs of implantation and the clinical results after 3 months and 1 year. All the five disc spacers are suitable for the ventral spondylodesis of the cervical spine. The titanium spacer from Weber is characterized by its comfortable handling and a price in the mean range. A good cost effectiveness and an easy handling is given by the Intromed-cage. The X-ray contrast of the Carbonium spacer by AcroMed is insufficient in the lower cervical spine. The handling is good, but the price is too high. The AcroMed, Medinorm and Intromed spacer have the tendency to migrate into the vertebral endplates. A final statement can only be given after the achievement of long-term results.

Adult↗

PubMed2004

Tunneling-induced spin alignment at low and zero field.

The transfer of rotational to spin angular momentum of CH3 groups according to the Haupt effect is shown to be independent of magnetic field strength, including zero field. Haupt enhanced pulsed nuclear resonance signals of gamma-picoline have been observed at fields below 50 mT with a sensitivity enhancement of more than 3 orders of magnitude over thermally polarized experiments.

Journal Article↗

PubMed2004

[Doctor reports of a neurological clinic in the view of permanent resident neurologists and nerve doctors].

Eight discharge reports involving five diagnoses (anterior territory ischemic stroke, epilepsy, Parkinson's syndrome, multiple sclerosis, polyneuropathy) from five neurological departments were peer-reviewed by five neurologists working in out-patient (private) practice. The review considered the diagnosis, case history, clinical status, laboratory investigation, differential diagnosis and treatment. Criticism mainly involved the quality of the clinical assessment, lack of clinical status at discharge, narrow or incomplete differential diagnosis and the quality of the neurophysiological investigations for epilepsy and polyneuropathy. Improvement potential was seen for the speed of reporting, better comprehensibility, omission of irrelevant information, greater participation of experienced neurologists in report writing, and standardization.

Ambulatory Care Facilities↗

PubMed2004

[Gravity valves for idiopathic normal pressure hydrocephalus. A Prospective study of 60 patients].

OBJECTIVE: Are hydrostatic valves superior to conventional differential pressure shunts in patients with normal- pressure hydrocephalus, with regard to the postoperative results of treatment and possible complications? METHODS: From September 1997 to January 2002, 60 patients with idiopathic normal-pressure hydrocephalus were treated by surgical implantation of a hydrostatic valve (Miethke dual-switch valve) at the Unfallkrankenhaus Berlin. RESULTS: One year after the shunt operation, the clinical picture was very good for 33% of the patients, good for 33%, satisfactory for 17%, and poor for 17%. At 20%, the rate of postoperative complications (catheter dislocations, valve infections, underdrainage and overdrainage) is still relatively high. The opening pressure of the Miethke dual-switch valve did not correlate with the postoperative results of treatment. CONCLUSION: According to our experience, hydrostatic Miethke dual-switch valves are superior to conventional differential pressure shunts without an additional gravity unit, especially with regard to the treatment of patients with idiopathic normal -pressure hydrocephalus, concerning both the postoperative results of the treatment and the incidence of possible complications. With differentiated diagnosis and therapy, a clinical improvement can be achieved for 83% of such patients.

Adult↗

PubMed2004

[Experiences with six different intervertebral disc spacers for spondylodesis of the cervical spine].

Spondylodesis of the cervical spine with autologous bone in cases of degenerative disease is associated with pain and complications in the os ilium region. Can this problem be solved when using intervertebral disc spacers? Between September 1997 and January 2003, 267 patients with degenerative disease of the cervical spine were treated operatively and monitored in a follow-up examination. In osteochondrosis of the cervical spine and/or disc herniation, we performed a discectomy using a ventral approach and removed dorsal osteophytes with a high-speed drill. The choice of the six different spacers was randomized. We used 66 titanium disc spacers manufactured by Aesculap, 54 titanium disc spacers by Weber, 52 titanium disc spacers by Intromed, 18 Wing spacers by Medinorm, 17 carbonium spacers by AcroMed, and 50 PEEK spacers by Intromed and did follow-up examinations after 3 and 12 months, respectively. The titanium spacer manufactured by Weber is characterized by good handling and a moderate price. The titanium cage from Intromed has the lowest price and good handling characteristics during operation. The X-ray contrast of the carbonium spacer made by AcroMed is not always sufficient for safe implantation, especially in the lower cervical spine. Handling is good, but the price is too high. The AcoMed, Medinorm, and Intromed titanium spacers show a tendency for penetrating ground plates of adjacent vertebra. The titanium cage Cespace manufactured by Aesculap has good handling characteristics and a moderate price. The PEEK spacer from Intromed can be implanted safely but shows a tendency for dislocation. Long-term results are yet to be reported.

Adult↗