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Biomedical subjects

Michael Schocke

Publications and source records attributed to Michael Schocke.

At least 19 recordsLinked to original sources
PubMed2006

A widespread distinct pattern of cerebral atrophy in patients with alcohol addiction revealed by voxel-based morphometry.

BACKGROUND: Patients with alcohol addiction show a number of transient or persistent neurological and psychiatric deficits. The complexity of these brain alterations suggests that several brain areas are involved, although the definition of the brain alteration patterns is not yet accomplished. AIM: To determine brain atrophy patterns in patients with alcohol dependence. METHODS: Voxel-based morphometry (VBM) of grey matter (GM) and white matter (WM) was performed in 22 patients with alcohol dependence and in 22 healthy controls matched for age and sex. RESULTS: In patients with alcohol dependence, VBM of GM revealed a significant decrease in density (p<0.001) in the precentral gyrus, middle frontal gyrus, insular cortex, dorsal hippocampus, anterior thalamus and cerebellum compared with controls. Reduced density of WM was found in the periventricular area, pons and cerebellar pedunculi in patients with alcohol addiction. CONCLUSIONS: Our findings provide evidence that alcohol addiction is associated with altered density of GM and WM of specific brain regions. This supports the assumption that alcohol dependence is associated with both local GM dysfunction and altered brain connectivity. Also, VBM is an effective tool for in vivo investigation of cerebral atrophy in patients with alcohol addiction.

Adult↗
PubMed2006

Neural correlates of verbal semantic memory in patients with temporal lobe epilepsy.

Functional imaging data suggest that the core network engaged in verbal semantic memory (SM) processing encompasses frontal and temporal lobe structures, with a strong left lateralization in normal right handers. The impact of long term temporal lobe epilepsy (TLE) on this network has only partly been elucidated. We studied verbal SM in 50 patients with chronic, intractable TLE (left TLE=26, right TLE=24) and 35 right handed normal controls using a verbal fMRI semantic decision paradigm. All patients had language lateralized to the left hemisphere, as verified by the intracarotid amobarbital procedure. Within and between group analyses showed remarkable, group-specific activation profiles. The control group activated frontal and temporal areas bilaterally, with a strong left predominance. Left TLE patients showed a shift of activations of left frontal and medial temporal areas to homologous regions in the right hemisphere. Furthermore, left TLE subjects utilized subcortical structures such as the thalamus and putamen to accomplish the verbal SM task. Contrastively, the activation pattern of right TLE patients resembled that of normal controls, but exhibited "hypofrontality" with a shift from frontal to posterior regions in the temporal, parietal and occipital lobe. Our results show that chronic epileptic activity originating from temporal seizure foci is associated with an alteration of neural circuits which support semantic language processing and that side of seizure focus has a specific impact on the resulting activation network. These findings presumably result from morphological changes and from functional reorganization which are both inherent to chronic TLE.

Adult↗
PubMed2006

Isolated numerical skills in posterior cortical atrophy--an fMRI study.

Posterior cortical atrophy (PCA) is characterized by bilateral parieto-occipito-temporal atrophy and hypometabolism. Neuropsychological impairments include complex visual disturbances, alexia, agraphia, finger agnosia, right-left disorientation and dyscalculia. A recent case study reported severe numerical deficits with some selectively preserved numerical skills in a patient affected by PCA [Delazer, M., Karner, E., Zamarian, L., Donnemiller, E., & Benke, T. (2006). Number processing in posterior cortical atrophy--a neuropsycholgical case study. Neuropsychologia]. In a functional magnetic resonance imaging (fMRI) study brain activation patterns related to these selectively preserved numerical skills were analyzed. Recitation of multiplication tables and counting forward were contrasted to word recitation in a block design. Contrasts between experimental conditions and control condition yielded significant activation of inferior and medial temporal structures. Since numerical processing is generally associated with parietal activation, it was hypothesized that preserved brain structures would compensate for the functional deficits.

Acoustic Stimulation↗
PubMed2006

Cortical atrophy in the cerebellar variant of multiple system atrophy: a voxel-based morphometry study.

This study aimed to determine in vivo the atrophy patterns in clinically established cerebellar variant of multiple-system atrophy (MSA-C) using voxel-based morphometry (VBM). Thirteen patients with MSA-C (12 probable, 1 possible) and 13 healthy controls matched for age and sex were included. High-resolution MR images were acquired with a 1.5 T scanner. Images were normalized onto a study-specific template, segmented into the tissue compartments, modulated with the Jacobian determinants, and finally smoothed with a Gaussian kernel filter of 10 mm. The general linear model was used to assess statistical differences in gray and white matter. Infratentorial atrophy was observed in the cerebellar hemispheres, vermis, mesencephalon, and pons of MSA-C patients. Supratentorial volume loss was found in orbitofrontal and mid-frontal regions as well as in temporomesial and insular areas of both hemispheres. A negative correlation was observed between a cerebellar ataxia score and the volume of cerebellar hemispheres, peduncles, and pons. To compare this atrophy pattern to that of spinocerebellar ataxia (SCA2), which was previously reported by our group, a conjunction analysis was assessed. We observed a volume loss shared by both disorders comprising the cerebellum, vermis, pons, mesencephalon, orbitofrontal, mid-frontal, and temporomesial cortex of both hemispheres as well as the left insular cortex.

Adult↗
PubMed2005

Voxel-based morphometry in narcolepsy.

BACKGROUND AND PURPOSE: Voxel-based morphometry (VBM) is a magnetic resonance imaging (MRI)-based indirect volumetry, which allows the investigation of the entire brain without restriction of predefined regions-of-interest. Recent studies using this technique reported controversial results in patients with narcolepsy. PATIENTS AND METHODS: In this study, 12 patients with narcolepsy according to the criteria of the International Classification of Sleep Disorders were compared to 12 age-matched controls with normal MR images using VBM. Sex and global differences in voxel intensities were used as confounding covariates. RESULTS: Significant gray matter loss was found in the right prefrontal and frontomesial cortex of patients with narcolepsy. White matter comparison revealed no significant changes in patients or controls. The comparison of cerebrospinal fluid partition detected an enlargement of subarachnoidal space of controls close to the prefrontal cortex. CONCLUSIONS: The volume reduction of gray matter in narcoleptic patients could indicate a disease-related atrophy pattern. However, the results of VBM studies in narcolepsy are contradictory. A possible systematic bias due to inhomogeneous patient groups, stimulant medication history or pre-statistical image processing must be considered. We suggest that studies with drug-naive patients and/or region-of-interest-based volumetric studies should be performed in areas defined by VBM.

Adult↗
PubMed2005

Chemical shift magnetic resonance spectroscopy of cingulate grey matter in patients with minimal hepatic encephalopathy.

Minimal hepatic encephalopathy (MHE) is frequently diagnosed in patients with liver cirrhosis who do not show overt clinical cirrhosis-associated neurological deficits. This condition manifests primarily with visuo-motor and attention deficits. We studied the association between visuo-motor deficits and magnetic resonance spectroscopic parameters in cingulate grey matter and white matter of centrum semiovale in patients with liver cirrhosis. The data revealed an increase in the glutamate-glutamine/creatine ratio and a decrease in choline/creatine and inositol/creatine ratios in patients with liver cirrhosis. The analysis of the data showed that cirrhosis-associated deterioration of the visuo-motor function significantly correlates with a decrease in the choline/creatine ratio and an increase in N-acetylaspartate/choline in cingulate grey matter but not in the neighbouring white matter. Furthermore, the increase in the glutamate-glutamine/creatine ratio correlated significantly with the increase in the N-acetylaspartate/creatine ratio. These data suggest an association between altered choline, glutamate-glutamine and NAA metabolism in cingulate grey matter and symptoms of MHE, and underline the importance of differentiation between grey and white matter in magnetic resonance spectroscopic studies on patients with cirrhosis-associated brain dysfunction.

Aspartic Acid↗
PubMed2005

Dialysis-related amyloidosis revisited.

OBJECTIVE: Dialysis-related amyloidosis occurs secondarily to the deposition of beta(2)-microglobulin. Dialysis-related amyloidosis predominantly involves the osteoarticular system and is clinically manifested by erosive and destructive osteoarthropathies, destructive spondyloarthropathy, and carpal tunnel syndrome. This article illustrates the radiographic, sonographic, CT, and MRI findings of dialysis-related amyloid arthropathies. CONCLUSION: Dialysis-related amyloidosis is characterized by various imaging appearances. In evaluating amyloidosis, MRI provides considerably more information than that obtained from conventional radiographic, CT, and sonographic studies.

Amyloidosis↗
PubMed2004

Basal forebrain atrophy is a distinctive pattern in dementia with Lewy bodies.

We determined brain atrophy patterns in dementia with Lewy bodies and Alzheimer's disease using voxel-based morphometry, an indirect volumetry. Ten patients with dementia with Lewy bodies, 10 patients with Alzheimer's disease and 10 controls were included. All groups were matched for age; sex and global differences in voxel intensities were included as confounding covariates. We observed basal forebrain atrophy discriminating dementia with Lewy bodies from Alzheimer's disease. Compared to controls, atrophy of lateral prefrontal cortex and left premotor cortex was seen in dementia with Lewy bodies whereas atrophy of the medial temporal cortex, posterior parietal cortex, thalamus and temporo-occipital areas was observed in Alzheimer's disease. Atrophy of insular cortex was found in both patient groups.

Aged↗
PubMed2004

Accurate, simplified and rapid three-dimensional echocardiographic volume quantifications: Comparison of different algorithms in symmetric and asymmetric left ventricular geometry.

OBJECTIVE: A comparative investigation of dynamic three-dimensional freehand echocardiography (D3DFE) and magnetic resonance imaging (MRI) was conducted to determine the accuracy and rapidity of the average rotation method (ARM) and the disk summation method (DSM) for volumetric analysis. METHODS: In 15 patients with an asymmetric left ventricle and 12 normal subjects, end-diastolic and end-systolic left ventricular volumes were assessed by D3DFE and by MRI. Both DSM and ARM were used for volume determination. All echocardiographic readings were performed by two examiners blinded to each other and to the MRI results. The times needed for echocardiographic data acquisition and volumetric analysis with either algorithm were determined. RESULTS: Correlation between ARM and MRI measurements was tighter than between DSM and MRI measurements (end-diastolic volume: r=0.95, P<0.0001 versus r=0.94, P<0.0001 in asymmetric ventricles; and r=0.97, P<0.0001 versus r=0.96, P<0.0001 in symmetric ventricles; end-systolic volume: r=0.94, P<0.0001 versus r=0.93, P<0.0001 in asymmetric ventricles and r=0.96, P<0.0001 versus r=0.94, P<0.0001 in symmetric ventricles). In addition, ARM analysis was less time-consuming than DSM (6.4+/-0.4 min versus 7.6+/-0.3 min, P<0.05). CONCLUSIONS: For D3DFE, ARM is the most accurate and rapid approach to left ventricular volume determination. ARM benefits from advanced two-dimensional imaging and can be easily added to any standard transthoracic echocardiographic examination.

Adult↗
PubMed2003

Atrophy pattern in SCA2 determined by voxel-based morphometry.

We applied voxel-based morphometry, an indirect volumetric technique, to MRI volumes of patients carrying the spinocerebellar ataxia type 2 mutation to determine patterns of brain atrophy. Nine patients were compared to 27 controls matched for age, sex and handedness. An optimised voxel-based morphometry protocol was used for pre-processing to minimize systematic bias. We observed significant volume loss in the cerebellar hemispheres, vermis, pons, mesencephalon and thalamus. Also affected were several supratentorial areas such as the right orbito-frontal cortex, right temporo-mesial cortex and the primary sensorimotor cortex bilaterally. The volumetric changes of cerebellar hemispheres were inversely correlated to cerebellar symptoms rated by a cerebellar ataxia scale. Two mechanisms could contribute to the observed cortical atrophy. It could be either the result of primary supratentorial degeneration as part of the disease process and/or secondary atrophy due to cerebellar deafferentation.

Ataxins↗
PubMed2003

Medial temporal lobe activation during semantic language processing: fMRI findings in healthy left- and right-handers.

Medial temporal lobe (MTL) areas are well known to serve episodic memory functions; their contribution to semantic memory has been occasionally noticed but not studied in detail. In the present fMRI study, 35 right-handed and 35 left-handed healthy subjects performed a semantic decision paradigm during which subjects heard spoken concrete nouns designating objects and had to decide on whether these objects were available in the supermarket and cost lest then a certain amount of money. The control paradigm consisted of sequences of low and high tones where subjects had to decide whether a sequence contained two high tones. The resulting contrast activation of semantic decision versus tone decision involved neocortical temporal, parietal, and prefrontal areas. Additional significant, bilateral activations in the MTL, the hippocampal formation, and adjacent areas were found. The exact incidence and location of activation was studied in a single-subject analysis for all 70 subjects. At the chosen threshold of P<0.001, 94% of subjects showed activations in the MTL and inferior temporal lobe (ITL). Activations were found along the longitudinal axis of the MTL, including the hippocampal formation and the parahippocampal gyrus. In the ITL, parts of the fusiform and lingual gyri were activated. Activations were similar in right- and left-handers. We conclude from this study that the MTL and parts of the ITL can be added to the areas activated by semantic verbal memory processing.

Acoustic Stimulation↗
PubMed2003

Detection and characterization of intracranial aneurysms with MR angiography: comparison of volume-rendering and maximum-intensity-projection algorithms.

OBJECTIVE: The purpose of this study was to compare volume rendering and maximum intensity projection as postprocessing techniques of MR angiography in the detection and characterization of intracranial aneurysms. MATERIALS AND METHODS: Three-dimensional time-of-flight MR angiography studies performed in 82 patients were retrospectively evaluated by two independent reviewers who were unaware of digital subtraction angiography findings, the standard of reference. Panoramic maximum-intensity-projection and volume-rendered angiograms were produced from each data set to investigate the presence of underlying aneurysms. Each detected aneurysm was then interactively evaluated with subvolume maximum-intensity-projection and targeted volume-rendering algorithms to evaluate aneurysm morphology and size. Aneurysm detection and characterization were evaluated by means of the receiver operating characteristic analysis, and aneurysm size was evaluated using the limits-of-agreement method. Image quality, aneurysm neck depiction, and vascular delineation were also compared between maximum-intensity-projection and volume-rendered images. The time required for the generation and interpretation of maximum-intensity-projection and volume-rendered images was assessed. RESULTS: Volume rendering tended to improve the diagnostic confidence (A(z) [area under the receiver operating characteristic curve] = 0.95 vs A(z) = 0.90 for maximum intensity projection) and yielded a considerable improvement in sensitivity (89% vs 71% for maximum intensity projection), particularly in the detection of small cerebral aneurysms. Regarding aneurysm morphology, volume rendering performed significantly better than maximum intensity projection in lobulation detection (p < 0.001) and slightly better in neck categorization (p > 0.238). Limits-of-agreement analysis showed a trend toward improved assessment of the aneurysm size by volume rendering (-0.31 +/- 1.62 mm vs -1.27 +/- 2.84 mm by maximum intensity projection). Overall image quality and vascular delineation of involved vessels on volume-rendered images were rated better than that obtained by maximum intensity projections (p < or = 0.007 and p < or = 0.001, respectively). Evaluation of time-of-flight MR angiography data sets was significantly facilitated with volume rendering (p < 0.001). CONCLUSION: The volume-rendering technique facilitates the evaluation of cerebral time-of-flight MR angiography data sets and allows better detection and more reliable characterization of intracranial aneurysms than does maximum intensity projection.

Adolescent↗
PubMed2002

Evaluation of striatal dopamine transporter function in rats by in vivo beta-[123I]CIT pinhole SPECT.

Striatal dopamine transporter (DAT) function was evaluated in rats by in vivo SPECT-MRI coregistration using the radioligand 2-beta-carbomethoxy-3-beta-(4-[123I]iodophenyl)tropane (beta-[123I]CIT). The reconstructed transaxial resolution of 3.5 mm full width at half-maximum and the system sensitivity of 0.081 c/s/kBq using a 2.0-mm pinhole collimator aperture provided adequate spatial detail and sufficient sensitivity for imaging striatal beta-[123I]CIT uptake. SPECT images, coregistered onto a MRI template, showed high accuracy in the coronal and transverse planes (maximum mismatch of 1.3 mm). Following estimation of the in vivo binding equilibrium of beta-[123I]CIT in the healthy rat striatum, we evaluated the 6-hydroxydopamine-induced loss of striatal DAT function using beta-[123I]CIT SPECT and MRI coregistration and correlated these findings with dopaminergic cell counts in the substantia nigra pars compacta using TH immunohistochemistry. A subtotal unilateral DAT deficit was detected by beta-[123I]CIT SPECT in all animals which correlated significantly with the cell counting of the remaining dopaminergic neurons. beta-[123I]CIT pinhole SPECT provides a powerful and widely available tool for in vivo investigations of rat striatal DAT function. In contrast to classical autoradiography, the present method will be helpful in imaging dynamic changes of neurotransmission in the CNS by virtue of serial study designs. Depending on SPECT ligand availability, a wide range of other CNS receptors may be imaged as well using the presented in vivo technique.

Animals↗
PubMed2002

The influence of hyperoxia on regional cerebral blood flow (rCBF), regional cerebral blood volume (rCBV) and cerebral blood flow velocity in the middle cerebral artery (CBFVMCA) in human volunteers.

Conflicting results reported on the effects of hyperoxia on cerebral hemodynamics have been attributed mainly to methodical and species differences. In the present study contrast-enhanced magnetic resonance imaging (MRI) perfusion measurement was used to analyze the influence of hyperoxia (fraction of inspired oxygen (FiO2) = 1.0) on regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) in awake, normoventilating volunteers (n = 19). Furthermore, the experiment was repeated in 20 volunteers for transcranial Doppler sonography (TCD) measurement of cerebral blood flow velocity in the middle cerebral artery (CBFV(MCA)). When compared to normoxia (FiO2 = 0.21), hyperoxia heterogeneously influenced rCBV (4.95 +/- 0.02 to 12.87 +/- 0.08 mL/100g (FiO2 = 0.21) vs. 4.50 +/- 0.02 to 13.09 +/- 0.09 mL/100g (FiO2 = 1.0). In contrast, hyperoxia diminished rCBF in all regions (68.08 +/- 0.38 to 199.58 +/- 1.58 mL/100g/min (FiO2 = 0.21) vs. 58.63 +/- 0.32 to 175.16 +/- 1.51 mL/100g/min (FiO2 = 1.0)) except in parietal and left frontal gray matter. CBFV(MCA) remained unchanged regardless of the inspired oxygen fraction (62 +/- 9 cm/s (FiO2 = 0.21) vs. 64 +/- 8 cm/s (FiO2 = 1.0)). Finding CBFV(MCA) unchanged during hyperoxia is consistent with the present study's unchanged rCBF in parietal and left frontal gray matter. In these fronto-parietal regions predominantly fed by the middle cerebral artery, the vasoconstrictor effect of oxygen was probably counteracted by increased perfusion of foci of neuronal activity controlling general behavior and arousal.

Adult↗
PubMed2002

Model-based imaging of cardiac electrical excitation in humans.

Activation time (AT) imaging from electrocardiographic (ECG) mapping data has been developing for several years. By coupling ECG mapping and three-dimensional (3-D) + time anatomical data, the electrical excitation sequence can be imaged completely noninvasively in the human heart. In this paper, a bidomain theory-based surface heart model AT imaging approach was applied to single-beat data of atrial and ventricular depolarization in two patients with structurally normal hearts. In both patients, the AT map was reconstructed from sinus and paced rhythm data. Pacing sites were the apex of the right ventricle and the coronary sinus (CS) ostium. For CS pacing, the reconstructed AT pattern on the endocardium of the right atrium was compared with the CARTO map in both patients. The localization errors of the origins of the initial endocardial breakthroughs were determined to be 6 and 12 mm. The sites of early activation and the areas with late activation were estimated with sufficient accuracy. The reconstructed sinus rhythm sequence was in good qualitative agreement with the pattern previously published for the isolated Langendorff-perfused human heart.

Adult↗
PubMed2002

3D MR angiography of renal arteries: comparison of volume rendering and maximum intensity projection algorithms.

PURPOSE: To compare volume rendering (VR) and maximum intensity projection (MIP) as postprocessing techniques of magnetic resonance (MR) angiography for detection and quantification of renal artery stenosis. MATERIALS AND METHODS: Twenty-seven patients underwent three-dimensional contrast material-enhanced MR angiography of the renal arteries with a 1.5-T imager. For each renal artery, targeted MIP and VR images were reconstructed in oblique coronal and transverse orientations. For each modality, image generation and evaluation were performed interactively by two independent radiologists blinded to angiographic results. In comparison with digital subtraction angiography (DSA) findings, stenosis quantification and detection by using MIP and VR were evaluated with the use of 50% and 70% cutoff points by using linear regression analysis and 2 x 2 tables. Overall image quality and vascular delineation on MIP and VR images were also compared. RESULTS: All main and accessory renal arteries depicted at DSA were also demonstrated on MIP and VR images. VR performed slightly better than MIP for quantification of stenoses greater than 50% (VR: r(2) = 0.84, P <.001; MIP: r(2) = 0.38, P =.001) and significantly better for severe stenoses (VR: r(2) = 0.83, P <.001; MIP: r(2) = 0.21, P =.1). For detection of stenosis, VR yielded a substantial improvement in positive predictive value (VR: 95% and 90%; MIP: 86% and 68% for stenoses greater than 50% and 70%, respectively). Image quality obtained with VR was not significantly better than that with MIP; however, vascular delineation on VR images was significantly better. CONCLUSION: The VR technique of renal MR angiography enabled more accurate detection and quantification of renal artery stenosis than did MIP, with significantly improved vascular delineation.

Adult↗