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K Ebmeier

Publications and source records attributed to K Ebmeier.

14 recordsLinked to original sources
PubMed2006

Cognitive impairment and fMRI in major depression.

Cognitive impairment in depression may be one of the more practically important aspects of the illness, responsible for much of its morbidity. It also is at the heart of its psychopathology, may contribute to strategies of treatment, and may give us a more easily quantifiable measure of impaired function to correlate with brain activity. Functional magnetic resonance imaging (fMRI) is ideally suited to examine brain function in depression. It has the correct time window to repeatedly sample cognitive task performance; it does not require exposure to radioactive tracers and can therefore be repeated many times; it also can be linked with high resolution structural images acquired in the same imaging session that help identify the regions of activation and support the spatial transformation necessary to compare the scans of different subjects. fMRI has already produced a series of consistent results in depression, identifying increased activity of rostral anterior cingulate and other medial prefrontal structures during effortful tasks and on occasion also increased dorsolateral prefrontal activity, suggesting increased possibly compensatory activity to maintain task performance. Investigating the interplay between limbic (orbitomedial) and 'cognitive' dorsolateral structures clearly has the potential to clarify important illness mechanisms of depressive illness.

Brain↗
PubMed2003

Intraoperative computerized tomography for improved accuracy of spinal navigation in pedicle screw placement of the thoracic spine.

We report on our experiences with the use of intraoperative CT imaging in surgery of the thoracic spine and on our results of pedicle screw insertion using spinal navigation and implantable fiducial markers. For our operations we used the Tomoscan M-EG and the EasyGuideSpine (Philips Medical Systems). During the operation the patient was positioned on the mobile CT table. Following dorsal preparation, small titanium screws were implanted in the vertebrae so as to serve as fiducial markers. Image data were obtained by performing a spiral CT scan. Ventilation was suspended for the duration of the CT scan. Screw insertion as well as vertebral biopsies were performed using spinal navigation. Intraoperative CT scans were obtained to confirm the position of the implants and to assess the amount of bony decompression as well as the realignment. Since 1998, 112 patients with various disorders of the thoracic spine have been operated on using the described technique. 365 screws were inserted in the area of T1 to T12. There were 23 (6.3%) misplacements of pedicle screws. In 42 cases (11.5%) we observed a minimal lateral perforation (<2 mm) of the pedicle wall. No neurological, cardiovascular, or pulmonary injury occurred. Intraoperative CT imaging influenced surgical decisions as well as the final result of surgery. Despite the use of intraoperative imaging and accurate spinal navigation, pedicle screw placement in the thoracic spine remains extremely challenging.

Bone Screws↗
PubMed2000

Incorporation of intraoperative computerized tomography in a newly developed spinal navigation technique.

OBJECTIVE: We report on the first successful incorporation of intraoperative computerized tomography in spinal navigation procedures. MATERIALS AND METHODS: All operations were performed with the aid of a Tomoscan M mobile CT system (Philips Medical Systems, Eindhoven, The Netherlands). The system comprises a mobile gantry, a mobile patient examination table, and a mobile workstation. Three different navigation systems were used: the EasyGuide (Philips Medical Systems, Eindhoven, The Netherlands), the Surgical Tool Navigator (Zeiss, Oberkochen, Germany), and a prototype of an ultrasound navigation system developed by ourselves (IVS GbR, Chemnitz, Germany). All surgical operations were performed with the patient positioned on the mobile table of the CT system. Following dorsal preparation of the vertebral region, the surgeon implanted small titanium screws in the vertebrae to serve as fiducial markers. Image data acquisition and image-to-patient registration were performed after implantation of the marker screws. The pedicle screws were inserted using the navigation system, and the position of each implant was confirmed by intraoperative CT scans. RESULTS: To date, 35 patients with various spine disorders have been operated upon using the technique described, and 161 pedicle screws have been inserted. There were no misplacements of pedicle screws. In three (1. 9 %) cases we observed lateral perforation (maximum 2 mm) of the lateral pedicle wall. We achieved a registration error of 0.85 mm (RMSE) +/- 0.42 mm (SD). CONCLUSIONS: The combination of intraoperative computerized tomography and spinal navigation allows easy navigation with a high application accuracy of 0.8 mm +/- 0.4 mm (SD) at the target point (measured in experiments with a plastic spine model). The possibility of performing an intraoperative quality check on demand markedly improves the safety of these procedures.

Adolescent↗
PubMed2000

Source localization and possible causes of interictal epileptic activity in tumor-associated epilepsy.

Electrophysiological studies in gliomas have demonstrated action potentials in neoplastic cells. These "spiking tumor cells" are, however, an enigma. In attempt to find evidences for spikes within tumoral borders, 21 patients with different intracerebral tumors were preoperatively screened for the occurrence of epileptogenic discharges using multichannel MEG and EEG. A correlation between histopathology and the distance between dipole and tumor border could be found. Glioma patients showed epileptic activities closer to the border than those with mixed glioneuronal neoplasms and metastases. Four glioma patients demonstrated epileptic activity within the tumor boundary, however, not in the deep center of the tumor. Patch-clamping of cells from acute glioma slices did not yield a correlation between the presence of voltage-gated sodium channels in tumor cells and the MEG/EEG data. Our results demonstrate that the zone with the highest epileptogenic potential is different in gliomas and other brain tumors. However, our data do not strongly suggest that glioma cells are directly involved in the generation of tumor-associated epilepsy in vivo via their capability to generate action potentials.

Action Potentials↗
PubMed2000

Neuronavigation in surgery of intracranial and spinal tumors.

PURPOSE: To demonstrate the new possibilities and advantages of neuronavigation in the surgery of intracranial and spinal tumors, based on patient populations treated in our hospital. MATERIALS AND METHODS: An infrared navigation system with integrated microscope guidance was used for frameless intracranial neuronavigation. The biopsies of intracranial tumors were carried out using a frame-based stereotactic technique. Intracranial navigation was, in part, combined with the use of an intraoperative CT scanner and a three-dimensional ultrasound system for data acquisition, correction of brain shifts, and intraoperative quality control. The navigation was also supported by presurgical brain mapping with magnetic source imaging. Navigation in spinal surgery was exclusively performed using an infrared navigation system in combination with an intraoperative CT scanner. RESULTS: The stereotactic tumor biopsies (n = 57) were carried out with an accuracy of 91.4% as compared with the histological diagnosis. The work flow of stereotactic procedures could be increased by using the intraoperative CT scanner. Fifty-seven patients with intracranial tumors were treated with the aid of neuronavigation between July 1997 and December 1999. These patients showed an improvement from 80% to 86% on the Karnofsky index 8 weeks postoperatively. The majority of intracranial cases were primary brain tumors (n = 30) and metastases (n = 13) in functionally important areas of the brain. In four patients, a significant brain shift was observed during neuronavigation, and could be corrected by an image update using either the intraoperative CT scanner (n = 2) or the three-dimensional ultrasound system (n = 2). The presurgical brain mapping with magnetoencephalography was shown to be reliable in the sensory cortex (n = 25). Eleven patients with a thoracic or lumbar tumor were treated by open surgery or stabilization, using a combination of spinal neuronavigation and the intraoperative CT scanner. Two patients with spinal tumors underwent navigated biopsies. Neither of them showed a reduction in the clinical stage, but the Karnofsky index improved from 63% up to 72% 8 weeks postoperatively. CONCLUSION: Neuronavigation allows very precise intracranial and spinal surgery. The problem of brain shift during the navigation procedures has been solved by intraoperative image acquisition. The use of neuronavigation was shown to improve the postoperative quality of life of patients suffering from brain and spinal tumors.

Adult↗
PubMed1999

Depressive illness.

WHO estimate that by the beginning of the next century major unipolar depression will be one of the most important causes of ill health overall. Whereas the cause of depression is still obscure, it is becoming clear that a number of diverse factors are likely to be implicated, both genetic and environmental. Effective treatment of depression similarly involves a variety of methods, from electro-convulsive therapy to inter-personal psychotherapy. The pathophysiology of depression is gradually becoming accessible through research strategies, such as functional neuroimaging paired with mood altering interventions.

Adolescent↗
PubMed1994

Clonidine infusion increases uptake of 99mTc-Exametazime in anterior cingulate cortex in Korsakoff's psychosis.

The effects upon regional brain function of infusing either saline or clonidine (1.5 microgram/kg) has been examined in 18 patients with alcoholic Korsakoff's psychosis using 99mTc-hexamethylpropyleneamineoxime (99mTc-HMPAO or 99mTc-Exametazime) and Single Photon Emission Tomography (SPET or SPECT). The hypothesis tested was that frontal lobe function would be increased by adrenoceptor stimulation. This was confirmed by an increase in the uptake of 99mTc-Exametazime into anterior cingulate regions of the frontal lobes. Patients were scanned before and after saline or clonidine infusion during performance of a verbal fluency task. There was a significantly increased performance of verbal fluency in patients given clonidine. This effect was variable and could not be unequivocably distinguished from increases in performance in the saline treated group. Nevertheless, the increase in neuropsychological performance was also correlated with increased function in left dorsolateral frontal cortex within the clonidine treated group. An exploratory examination of other brain areas suggested that relative increases in posterior cingulate cortex and changes in the symmetry of function within the thalamus may also be produced by acute infusion of clonidine in Korsakoff patients. The findings support the idea that adrenergic mechanisms may modulate cognitive performance by actions on attentional systems within the brain. These appear to be located primarily within limbic cortex. It is, of course, notable that this can occur in patients with profound and disabling amnesia.

Adult↗
PubMed1990

Low plasma iron status and akathisia.

Thirty patients were examined to test the hypothesis that a depletion of iron levels is associated with symptoms of akathisia. Fifteen akathisic patients were pair-matched with 15 non-akathisic patients. Plasma ferritin levels were significantly decreased in the akathisic patients, and there was a significant inverse correlation between plasma iron levels and akathisia rating. In addition, akathisia ratings were found to be correlated with a scale measuring symptoms of tardive dyskinesia.

Adult↗
PubMed1975

[Histological and biochemical changes in the lung in relation to survival time following femoral fracture in the dog].

Following an experimentally applied fracture of the upper limb fat embolism can be demonstrated in the lungs. By quantitative histological evaluation and biochemical lipid analysis a definite correlation can be observed between the amount of fat in the lungs and the time interval that had elapsed between fracture and death of the animals. More fat is to found in lungs histologically as well as biochemically in those animals, in which the time interval was shorter (165 minutes) than in those which survived for a longer period of time (168 hours). The electronmicroscopic morphometric examination turned out an increased volume of the interstitium 72 hours after the fracture.

Animals↗