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Biomedical subjects

Peter Raab

Publications and source records attributed to Peter Raab.

12 recordsLinked to original sources
PubMed2006

Radiological evaluation of unstable (acute) slipped capital femoral epiphysis treated by pinning with Kirschner wires.

Treatment of slipped capital femoral epiphysis is still controversial with regard to the implants used for stabilization and the need for prophylactic treatment of the contralateral, unaffected, side. The objective of this study was to ascertain whether prophylactic transfixation of the epiphysis with Kirschner wires in patients with unstable slipped capital femoral epiphysis resulted in significant disturbance of the growth plate and impairment of further growth of the femoral neck and head. Between 1990 and 1999, 29 patients with unstable slipped capital femoral epiphysis were simultaneously treated with internal fixation of the epiphysis and metaphysis with 3-4 Kirschner wires on the affected and the not (yet) affected side. After a mean follow-up of 3.5 years, we evaluated the hip joints radiologically, analysing different roentgenological parameters (CCD angle, femoral head diameter, length of the femoral neck and sphericity of the femoral head). CCD angle, femoral head diameter and length of the femoral neck showed statistically significant (P<0.001, Student's t-test) differences between the affected and unaffected, but prophylactically pinned, sides. Asphericity of the femoral head was found in six cases only on the affected side, whereas all hips, which were operated prophylactically, showed spherical femoral heads at follow-up (P<0.02, Pearson's chi test). These results indicate that the slip itself may cause impairment of the femoral growth plate in patients with unstable slipped capital femoral epiphysis and not stabilization with Kirschner wires. Compared with other series from the literature using different implants (screws, nails), prophylactic transfixation of the epiphysis and metaphysis with Kirschner wires is less compromising to the growth plate on the not (yet) affected side.

Acute Disease↗
PubMed2005

Brain surface reformatted images for fast and easy localization of perirolandic lesions.

OBJECT: The goal of this study was to evaluate a novel form of brain surface representation that allows simple, reliable mapping of the surface neuroanatomy for the preoperative evaluation of the spatial relationship between a focal lesion and the precentral gyrus. METHODS: High-resolution three-dimensional (3D) magnetic resonance (MR) imaging data sets were postprocessed using a curved multiplanar reformatting technique to create brain surface reformatted (BSR) images. These BSR images were reconstructed in less than 5 minutes and demonstrated the entire central sulcus with adjacent surface structures in one view. Two experienced neuroradiologists determined the localization of lesions near the central sulcus in 27 patients on standard MR images in three orthogonal planes and on BSR images. In addition, these observers judged whether the lesions were easy or difficult to localize on standard MR and BSR images, and whether diagnoses based on these methods were certain or doubtful. Anatomical localization based on BSR images was compared with that based on functional MR (fMR) images or intraoperative mapping of motor function. The BSR images yielded a perfect concordance with the fMR images and intraoperative mapping (Cohen kappa 1.0) and optimal diagnostic accuracy in localizing perirolandic lesions (both sensitivity and specificity were 100%). Localization was judged to be easy for 48 of 54 diagnoses based on BSR images compared with 26 of 54 based on standard MR images. Diagnoses were assessed as certain for 52 cases based on BSR images and 34 cases based on standard MR images. CONCLUSIONS: Brain surface reformatted imaging improves the diagnostic accuracy of standard anatomical MR imaging for localizing superficial brain lesions in relation to the precentral gyrus. The complementary use of this technique with standard two-dimensional imaging is supported by the fast and simple postprocessing technique and may provide useful information for preoperative surgical planning.

Adult↗
PubMed2003

Event-related fMRI for the suppression of speech-associated artifacts in stuttering.

The purpose of this study was to establish functional magnetic resonance imaging (fMRI) for the investigation of brain function during overt speech production in stuttering. Up to now this technique has rarely been used for the investigation of speech production paradigms because artifacts related to overt speaking largely impair the sensitivity toward task-related activation. Recently, the temporal delay of the hemodynamic response has been exploited to achieve a suppression of speech-related artifacts. By the limitation to very short utterances (one word), a temporal segregation of the respective effects was accomplished by means of an event-related experimental design. However, the investigation of speech production in persons who stutter requires a more extensive speaking situation. Since longer and more complex utterances evoke more symptoms of stuttering than reading of single words, a useful task should at least include the reading of full sentences. In this study we performed simulations to investigate the correlation of speech-related artifacts with the respective hemodynamic response in dependency on speech duration and rate of data sampling. Furthermore, we show that prolonged stimulus durations and repetition times of 3 s still allow an effective suppression of speech-related artifacts in fluent as well as in nonfluent speakers. Not only were obvious false activations at high contrast cerebrospinal fluid tissue borders widely eliminated, subjects also displayed consistent activation in speech-related and motor areas. As these results widely resemble those obtained by earlier neuroimaging studies on language production, event-related fMRI seems to be capable of recording neurophysiological correlates of overt speech production.

Adult↗
PubMed2003

Evidence for compensation for stuttering by the right frontal operculum.

There is recent evidence of focal alteration in fibre tracts underlying the left sensorimotor cortex in persistent developmental stuttering (PDS) [Lancet 360 (2002) 380]. If, as proposed, this anatomical abnormality is the cause of PDS, then overactivation in the right hemisphere seen with functional neuroimaging in stutterers may reflect a compensatory mechanism. To investigate this hypothesis, we performed two functional magnetic resonance imaging (fMRI) experiments. The first showed systematic activation of a single focus in the right frontal operculum (RFO) in PDS subjects during reading, which was not observed in controls. Responses in this region were negatively correlated with the severity of stuttering, suggesting compensation rather than primary dysfunction. Negative correlation was also observed during the baseline task that consisted in passive viewing of meaningless signs, indicating that RFO compensation acts independently of specific demands on motor speech output. The second experiment, that involved a covert semantic decision task, confirmed that RFO activation does not require overt utterances or motor output. In combination these findings suggest that the RFO serves a nonspecific compensatory role rather than one restricted to the final stages of speech production.

Adult↗
PubMed2003

Preoperative proton-MR spectroscopy of gliomas--correlation with quantitative nuclear morphology in surgical specimen.

A comparison between data from proton-MR spectroscopy (1HMRS) and quantitative histomorphology of tumor cell nuclei in gliomas has not been reported up to now. Therefore, the question must be answered, if there are any significant correlations between histomorphology of gliomas and quantitative data from 1HMRS concerning tissue metabolites. Surgical glioma specimen (glioblastomas, astrocytomas, oligodendrogliomas) from 46 patients with tumor grades II-IV according to WHO have been evaluated by means of a digital image analysis system using Ki-67-immunostained paraffin sections. Nuclear density, Ki-67-proliferation index, nuclear area and shape variables (roundness factor, Fourier-amplitudes) have been determined from 200 randomly selected tumor cell nuclei in each tumor specimen. These data have been correlated with preoperative data from 1HMRS. A positive correlation between Fourier-amplitudes, choline peak and lipide peak was observed, as well as a negative correlation between these variables and the nuclear roundness factor. This result indicates higher choline and lipide peaks with increasing irregularity of nuclear outlines. Proliferation index Ki-67 was positively correlated with the lipide peak, nuclear density showed a positive correlation with the choline peak. Glioblastomas (n = 29) showed an additional positive correlation between mean nuclear size and total creatine. Anaplastic gliomas (n = 12) showed a positive correlation between lactate peak and the standard deviation of the nuclear roundness factor. Further multivariate analyses have shown, that for the present collective of 46 cases, histometric variables have a higher significance than spectroscopic data for the differentiation of the different tumor grades. These results verify a significant correlation between preoperative data from 1HMRS and histomorphology of tumor cell nuclei in gliomas, supporting the biological significance of both histomorphometry and 1HMRS for the evaluation of these tumors.

Brain Neoplasms↗
PubMed2003

Correlation between preoperative magnetic resonance spectroscopic data on high grade gliomas and morphology of Ki-67-positive tumor cell nuclei.

OBJECTIVE: To investigate possible statistical correlations between metabolic data from preoperative proton magnetic resonance spectroscopy (1HMRS) and morphology of proliferating tumor cell nuclei in anaplastic gliomas and glioblastomas. STUDY DESIGN: Ki-67-positive tumor cell nuclei in paraffin sections of surgical specimens from 36 patients (7 anaplastic gliomas, World Health Organization grade 3; 29 glioblastomas, World Health Organization grade 4) were investigated by means of a digital image analysis system. Stringent inclusion criteria were formulated for all cases with respect to histologic quality and spectroscopic examination. As morphometric variables, nuclear area, shape variables (roundness factor, size-invariate Fourier amplitudes) and density of Ki-67-positive tumor cell nuclei per reference area were determined. RESULTS: Correlation analysis according to Spearman revealed a significant positive correlation between the total creatine (TCR) peak and nuclear area (P = .005). This correlation was also found within the glioblastoma group (P = .019). There was also a significant negative correlation of nuclear area with the ratio between choline and TCR in all cases (P = .014) and within the glioblastoma group (P = .046). No significant correlation of spectroscopic data was found with nuclear shape or density of Ki-67-positive tumor cell nuclei. CONCLUSION: The results demonstrate a correlation between spectroscopic data and morphology of proliferating tumor cell nuclei (nuclear size) in high grade gliomas. This study is part of a detailed investigation of the interrelationship between preoperative 1HMRS and quantitative histomorphology of gliomas.

Biomarkers, Tumor↗
PubMed2003

Clinical outcome in monosegmental fusion of degenerative lumbar instabilities:instrumented versus non-instrumented.

BACKGROUND: Degenerative lumbar instabilities are one of the major reasons for low back pain, especially in elderly people. There is still controversy in the literature about the clinical outcome of instrumented monosegmental fusions compared to noninstrumented posterolateral fusions. MATERIAL/METHODS: In this study we described the postoperative outcome of 33 patients who underwent posterolateral monosegmental spinal fusion:instrumented (17 patients)or noninstrumented (16 patients).All patients received the same instrumentation system. Medical history (considering daily activities,sports,social contacts and quality of life),clinical examination and radiological analysis served as evaluation parameters. Data were collected by a questionnaire based on the Oswestry Disability Score for low back pain. RESULTS: 86.6%of all subjects showed an improvement of postoperative health status. Although patients with fusion without internal fixation needed a reduced dose of postoperative analgesics compared to the monosegmental non-instrumented group,there were no statistical differences in patient-reported,clinical and radiographical outcome between the two groups. CONCLUSIONS: The results do not indicate a benefit in outcome from added instrumentation in elective lumbar fusions. This should be considered in each single case when a spinal fusion in the treatment of degenerative lumbar instability is indicated.

Adult↗
PubMed2002

Diabetic nephropathy.

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Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2002

Increased choline levels coincide with enhanced proliferative activity of human neuroepithelial brain tumors.

Proton MR spectroscopy ((1)H MRS)-visible total choline-containing compounds (tCho-compounds) are derivatives of membrane phospholipids and, in part, may act as a long-term second-messenger system for cellular proliferation. Experimental evidence suggests increasing concentrations of tCho-compounds during cellular proliferation. The present study was conducted in order to test the hypothesis that in vivo measurements of tCho-concentrations using (1)H MRS allow assessment of the proliferative activity of neuroepithelial brain tumors presurgically. Single-voxel (1)H MRS (PRESS, TR 1500 ms, TE 135 ms) was performed in 101 patients with neuroepithelial brain tumors prior to surgery and 19 healthy volunteers. Histological diagnoses were confirmed postsurgically according to the WHO classification. Measured tCho-compound signal intensities were corrected for coil loading, numbers of acquisitions and voxel size, and tCho concentrations calculated as institutional arbitrary units. They were matched with the mean immunohistochemical marker of cell proliferation, the Ki-67 (MIB.1) labeling index, using correlation analysis according to Spearman. Compared with low-grade tumors (i.e. WHO grade I/II) and normal white brain matter, high-grade tumors (i.e. WHO grade III/IV) revealed significantly (p < 0.05) elevated labeling indices paralleled by increasingly elevated tCho-concentrations. In contrast tCho-concentrations in low-grade tumor did not differ significantly from physiological values. A highly significant positive correlation (p < 0.0001, r(2) = 0.81) was found between the tCho-concentration and the labeling index. It was concluded that the determination of tCho-concentrations using in vivo (1)H MRS could provide a novel and noninvasive assessment of the proliferative activity of neuroepithelial brain tumors, pointing at (1)H MRS as a useful method for differentiating proliferating from non-proliferating tissues. Hence, potential indications for the clinical application of (1)H MRS are grading tumors presurgically, early detection of anaplastic transformation, and monitoring treatment.

Brain↗
PubMed2002

Prospective evaluation of a clinical score for 60-day mortality after transjugular intrahepatic portosystemic stent-shunt: Bonn TIPSS early mortality analysis.

OBJECTIVE: Transjugular intrahepatic portosystemic stent-shunt (TIPSS) is increasingly used to treat complications of portal hypertension, but proven tools for risk assessment of early mortality are lacking. DESIGN: The prospective evaluation of a new 60-day mortality score. PATIENTS AND METHODS: In a tertiary medical centre, 30 consecutive TIPSS patients were analysed for early mortality predictors, such as Child-Pugh score, TIPSS urgency (elective: > or = 36 h or emergency: < 36 h after variceal bleeding), comorbidity (Acute Physiology and Chronic Health Evaluation [APACHE]-II) and clinical data. Main predictors (P< 0.01) in this group (group-1: Child-Pugh score 10A, 10B, 10C) were graded (1, 2 or 3 points representing low, medium and high risk, respectively) and summarized as a Bonn TIPSS early mortality (BOTEM) score. This score was then tested prospectively in the next 73 TIPSS patients (group-2: Child-Pugh score 14A, 42B, 17C). RESULTS: Group 1 early mortality (30%) depended primarily on bilirubin (P< 0.005), APACHE-II (P < 0.001) and TIPSS urgency (P< 0.001). Added risk points (1, 2, 3) for bilirubin (< 3 mg/dl, 3-6 mg/dl, > 6 mg/dl, respectively), APACHE-II (< 10, 10-20, > 20 points, respectively) and urgency (elective, emergency, active bleeding, respectively) represented individual BOTEM score points. BOTEM was the best mortality predictor (P< 0.001); < or = / > 6 score points was the optimal cut-off, with 56% sensitivity, 100% specificity, 100% positive predictive value, 84% negative predictive value and 87% accuracy. In group 2, early mortality (8.2%) was again best predicted by BOTEM (P < 0.01) with the same cut-off and 67% sensitivity, 99% specificity, 80% positive predictive value, 97% negative predictive value and 96% accuracy. CONCLUSION: BOTEM score based on bilirubin, comorbidity and TIPSS-urgency predicts rather reliably post-TIPSS 60-day mortality and might optimize TIPSS treatment.

Aged↗
PubMedDate not supplied

Cholesterol metabolism in patients with chronic renal failure on hemodialysis.

Premature atherosclerosis is a major concern in patients on chronic dialysis and the identification of risk factors is important for preventive and interventional strategies. Other than the recognized atherogenic lipoprotein levels, little is known about overall cholesterol metabolism in patients on chronic hemodialysis (HD) and the best therapeutic intervention is still being debated. Therefore, we investigated intestinal cholesterol absorption, cholesterol and bile acid synthesis, and non-cholesterol plasma sterols in eight patients on dialysis and compared the results to those of 16 healthy male controls matched for body mass index and dietary cholesterol intake. Total, low-density lipoprotein (LDL) cholesterol, and triglycerides did not differ between the groups, but dialysis patients had a significantly lower high-density lipoprotein (HDL) cholesterol level (39 +/- 11 mg/dL vs. 48 +/- 10 mg/dL, p < 0.045). However, fractional cholesterol absorption, was significantly lower in dialysis patients (42.8 +/- 10.9% vs. 53.4 +/- 11%, p < 0.035), whereas plasma plant sterol concentrations and their ratios to cholesterol did not differ. Bile acid and total cholesterol synthesis were lower in dialysis patients (40% and -25%, respectively), although the differences were not significant. In contrast, lathosterol and its ratio to cholesterol in plasma was significantly lower in dialysis patients (0.176 +/- 0.084 mg/dL vs. 0.251 +/- 0.102 mg/dL, p < 0.024 and 0.733 +/- 0.353 microg/mg vs. 1.172 +/- 0.407 microg/mg, p < 0.017, respectively), indicating reduced hepatic de novo cholesterol synthesis. It is concluded that reduced HDL cholesterol and reduced bile acid synthesis contributes to atherosclerosis pathogenesis in dialysis patients, whereas intestinal cholesterol absorption and hepatic cholesterol synthesis did not seem dominant in this process at this stage of disease. Consequently, treatment with bile acid binding resins could be preferable to treatment with cholesterol absorption and synthesis inhibitors.

Adult↗