Papers by Attila Schwarcz
We read with interest the recent article by Kucinski et al. 1 The authors observed a decrease in ... more We read with interest the recent article by Kucinski et al. 1 The authors observed a decrease in the apparent diffusion coefficient (ADC) in diffusion-weighted MR imaging and a corresponding decrease in CT density in patients suffering from acute ischemic stroke of the anterior cerebral circulation. CT measurements showed a continuous linear decrease of 0.4 Hounsfield U/h, whereas the decrease in ADC was almost complete after 1.5 hours. Thus, a different time course was found between the 2 phenomena. A correlation between the decrease in ADC and that of CT density was found. They concluded that the severity of diffusion restriction correlated with net water uptake in acute ischemic stroke.
P3. 128< sup> 1</sup> H-MRS after bilateral DBS of the STN in Parkinson's disease
Quantitative MRI Studies of Chronic Brain White Matter Hyperintensities in Migraine Patients
Headache: The Journal of Head and Face Pain, 2013
The aim of this study was to examine chronic brain white matter hyperintensities in migraine and ... more The aim of this study was to examine chronic brain white matter hyperintensities in migraine and to gain data on the characteristics of the lesions. Migraine associates with a higher incidence of magnetic resonance imaging (MRI)-visible white matter signal abnormalities. Several attack-related pathomechanisms have been proposed in the lesion development, including the effect of repeated intracerebral hemodynamic changes. Supratentorial white matter hyperintensities of 17 migraine patients were investigated interictally with quantitative MRI, including quantitative single voxel spectroscopy, diffusion, and perfusion MRI at 3.0-Tesla. The findings were compared with data measured in the contralateral, normal-appearing white matter of migraineurs and in the white matter of 17 healthy subjects. Significantly higher apparent diffusion coefficient values, prolonged T2 relaxation times, and decreased N-acetyl-aspartate and creatine/phosphocreatine concentrations were found in the white matter hyperintensities. The cerebral blood flow and blood volume values were mildly decreased inside the hyperintensities. Differences were not present between the migraine patients&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; normal-appearing white matter and the white matter of healthy subjects. The MRI measurements denote tissue damage with axonal loss, low glial cell density, and an enlarged extracellular space with an increased extracellular water fraction. These radiological features might be the consequences of microvascular ischemic changes during migraine attacks.
Brain and Cognition, 2013
Most people are left-hemisphere dominant for language. However the neuroanatomy of language later... more Most people are left-hemisphere dominant for language. However the neuroanatomy of language lateralization is not fully understood. By combining functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI), we studied whether language lateralization is associated with cerebral white-matter (WM) microstructure. Sixteen healthy, left-handed women aged 20-25 were included in the study. Left-handers were targeted in order to increase the chances of involving subjects with atypical language lateralization. Language lateralization was determined by fMRI using a verbal fluency paradigm. Tract-based spatial statistics analysis of DTI data was applied to test for WM microstructural correlates of language lateralization across the whole brain. Fractional anisotropy and mean diffusivity were used as indicators of WM microstructural organization. Right-hemispheric language dominance was associated with reduced microstructural integrity of the left superior longitudinal fasciculus and left-sided parietal lobe WM. In left-handed women, reduced integrity of the left-sided language related tracts may be closely linked to the development of right hemispheric language dominance. Our results may offer new insights into language lateralization and structure-function relationships in human language system.
[Functional MRI at 1 Tesla. Basic paradigms and clinical application]
Ideggyógyászati szemle, Jan 30, 2007
To perform functional MRI experiments at low magnetic field, and to set up routine protocol to he... more To perform functional MRI experiments at low magnetic field, and to set up routine protocol to help the planning of neurosurgical operations and the examination of epilepsy patients. An optimized 2D EPI sequence was applied to yield functional MR images in basic paradigms such as finger tapping and internal word generation. Further, activation was induced also by a task involving mental navigation based on the retrieval of individually familiar visuo-spatial knowledge. Low resolution (matrix of 64x64) functional MR images satisfactorily visualized moto-sensor strip and speech centers. In the mental navigation task bilateral activation of the hippocampal formation was observed. Determination of motor area was also performed in an epilepsy patient whose seizure focus had been found in the area of pre- and post-central gyrus. The dislocation of the motor cortex was demonstrated. Functional MR images with fine quality can be obtained in basic paradigms even at low magnetic field if MR i...
[The use of minimally invasive instrumental spinal surgical technique in lumbar diseases of degenerative or traumatic origin]
Ideggyógyászati szemle, Jan 30, 2013
Paradigm change has recently taken place in spine surgery with the application of minimally invas... more Paradigm change has recently taken place in spine surgery with the application of minimally invasive techniques. Minimally invasive techniques have several advantages over the open traditional techniques: less blood loss, preservation of spine muscle integrity, shorter hospitalization, early mobilization, reduced pain levels, lower risk of infection. The presented cases cover following lumbar pathologies: segmental spinal instability, LV-SI grade II. spondylolisthesis, degenerative spondylolisthesis, spine trauma. Unilateral or bilateral mini-open technique was employed in the degenerative cases, depending on symptoms and signes. If unilateral symptoms--pathology was identified, screws and rod were implanted percutaneously on the side contralateral to the pathology. The segmental fusion between vertebral bodies was always assured by a cage and autologous bone. The presented trauma case involved combined AO type A2 and B fractures. The anterior column was strengthened with vertebral ...
Journal of neuroradiology. Journal de neuroradiologie, 2011
To demonstrate the capability of a clinical 3T human scanner in performing quantitative MR experi... more To demonstrate the capability of a clinical 3T human scanner in performing quantitative MR experiments in the rat brain. In vivo, measurements on eight Wistar rats were performed. Longitudinal relaxation time (T1) and transverse relaxation time (T2) measurements were set up at a spatial resolution of 0.3×0.3×1mm(3). Diffusion-weighted imaging was also applied and the evaluation included both mono- and biexponential approaches (b-value up to 6000s/mm(2)). Besides quantitative imaging, the rat brain was also scanned at a microscopic resolution of 130×130×130μm(3). Quantitative proton spectroscopy was also carried out on the rat brain with water as internal reference. T1 and T2 for the rat brain cortex were 1272±85ms and 75±2ms, respectively. Diffusion-weighted imaging yielded accurate diffusion coefficient measurements at both low and high b-value ranges. The concentrations of MR visible metabolites were determined for the major resonances (i.e., N-acetyl-aspartate, choline and creati...
It is generally believed that the apparent diffusion coefficient (ADC) changes measured by diffus... more It is generally believed that the apparent diffusion coefficient (ADC) changes measured by diffusion-weighted imaging (DWI) in brain pathologies are related to alterations in the water compartments. The aim of this study was to elucidate the role of compartmentalization in DWI via biexponential analysis of the signal decay due to diffusion. DWI experiments were performed on mouse brain over an extended range of b-values (up to 10000 mm -2 s) under intact, global ischemic, and cold-injury conditions. DWI was additionally applied to centrifuged human erythrocyte samples with a negligible extracellular space. Biexponential signal decay was found to occur in the cortex of the intact mouse brain. During global ischemia, in addition to a drop in the ADC in both components, a shift from the volume fraction of the rapidly diffusing component to the slowly diffusing one was observed. In cold injury, the biexponential signal decay was still present despite the electron-microscopically validated disintegration of the membranes. The biexponential function was also applicable for fitting of the data obtained on erythrocyte samples. The results suggest that compartmentalization is not an essential feature of biexponential decay in diffusion experiments. Magn Reson Med 51:278 -285, 2004.
Journal of neurotrauma, Jan 9, 2015
Midline shift following severe traumatic brain injury (sTBI) detected on CT scans is an establish... more Midline shift following severe traumatic brain injury (sTBI) detected on CT scans is an established predictor of poor outcome. We hypothesized that lateral ventricular volume (LVV) asymmetry is an earlier sign of developing asymmetric intracranial pathology than midline shift. This retrospective analysis was performed on data from 84 adults with blunt sTBI requiring a ventriculostomy who presented to a Level I Trauma Center. Seventy-six patients underwent serial CTs within 3 hours and an average of 3 scans within the first 10 days of sTBI. Left and right LVVs were quantified by computer assisted manual volumetric measurements. LVV ratios (LVR) were determined on the admission CT to evaluate ventricular asymmetry. The relationship between the admission LVR value and subsequent midline shift development was tested using ROC analysis, odds ratio (OR) and relative risk (RR) tests. Sixty patients had no >5mm midline shift on the initial admission scan. Of these, 15 patients developed ...
Pain-related autonomic response is modulated by the medial prefrontal cortex: An ECG–fMRI study in men
Journal of the Neurological Sciences, 2015
Our goal was to identify brain structures responsible for pain-related autonomic changes by the c... more Our goal was to identify brain structures responsible for pain-related autonomic changes by the correlation of simultaneously acquired functional magnetic resonance imaging (fMRI) and electrocardiogram (ECG) data. Eighteen healthy men (age: 22.89 ± 1.96) were involved. Painful sensation was evoked by heat. Simultaneously recorded brain fMRI and ECG data during pain were compared to data acquired during a non-painful heat sensation. From the ECG data, time- and frequency domain parameters of heart rate variability (HRV) were extracted. We found that: (1) among the common elements of both pain network and central autonomic network (CAN) only the medial prefrontal frontal cortex (MPFC) showed significant correlation with HRV; (2) the parasympathetic response to the painful stimuli showed a positive, while the sympathetic response a negative association with pain related BOLD-signal change observed in MPFC; (3) time domain parameters of HRV were negatively associated with MPFC activation. The novelty of our study-compared to previous ECG-fMRI studies-is that we used pain as stimulus and investigated both frequency- and time-domain parameters of HRV. Compared to other stimuli used in earlier studies to activate the CAN, pain sensation can be standardized easier and might allow us to better understand the functional organization of CAN. The results of the current ECG-fMRI study may have direct clinical relevance in understanding the pathomechanisms of several clinical conditions. There are some simultaneous ECG-fMRI and ECG-Positron Emission Tomography (PET) studies, but limited information is available about the pain-related brain function-HRV relations. The novelty of our study is that we used pain as stimulus to activate the central autonomic network and investigated both frequency- and time-domain parameters of HRV.
P3.128 1H-MRS after bilateral DBS of the STN in Parkinson's disease
Parkinsonism & Related Disorders, 2009
1H-MRS experiences after bilateral DBS of the STN in Parkinson's disease
Parkinsonism & Related Disorders, 2008
The objective of this study was to evaluate the changes in the concentrations of certain brain me... more The objective of this study was to evaluate the changes in the concentrations of certain brain metabolites in 13 patients with Parkinson&#39;s disease before and after bilateral subthalamic nucleus (STN DBS). The N-acetylaspartate (NAA)/choline (Chol), NAA/creatine (Cr), Chol/Cr ratios were determined by single voxel Proton magnetic resonance spectroscopy ((1)H-MRS) studies on 1.0T unit using short TE stimulated echo acquisition mode (STEAM) sequence. Spectra were obtained from the right and left globus pallidus, and left fronto-basal cortex. The patients were also assessed according to the UPDRS part III, in the &quot;medication-on and off&quot; conditions. after STN DBS cortical NAA/Cho, NAA/Cr ratios increased significantly, which were highly correlated with the significant improvements of the UPDRS scores.
Are there any gender differences in the hippocampus volume after head-size correction? A volumetric and voxel-based morphometric study
Neuroscience Letters, 2014
Previous findings on normal sexual dimorphism in hippocampal volume have not always been consiste... more Previous findings on normal sexual dimorphism in hippocampal volume have not always been consistent. This study investigated gender differences in hippocampal volume using different head-size correction strategies. T1-weighted MR images were collected in 99 healthy, Caucasian, university students (66 female subjects; mean age: 23.1 ± 2.3, range: 19-31 years). Sexual dimorphism in hippocampus was investigated by automated MRI volumetry and voxel-based morphometry (VBM) using both general linear model (GLM) and proportion head-size correction strategies. Absolute hippocampal volumes were larger in men than women. After adjusting for head-size, the proportion method indicated larger hippocampi in women than men, while no gender differences were found using the GLM approach. Investigating absolute hippocampal volumes in 15 head-size matched pairs of males and females indicated no gender differences. We suggest that there is no sexual dimorphism in hippocampal size and the apparent gender differences found by the proportion method may have more to do with head-size than with sex. The GLM and proportion head-size correction strategies are not interchangeable and may yield different results. The importance of the present findings is mostly related to scientific reproducibility across MRI volumetry or VBM studies.
Magnetic Resonance in Medicine, 2003
Localized proton MR spectroscopy (MRS) was used to quantify cerebral metabolite concentrations in... more Localized proton MR spectroscopy (MRS) was used to quantify cerebral metabolite concentrations in NMRI (n ؍ 8), BALB/c (n ؍ 7), and C57BL/6 (n ؍ 8) mice in vivo and 1 hr after global irreversible ischemia (2.35 T, STEAM, TR/TE/TM ؍ 6000/20/10 ms, 4 ؋ 3 ؋ 4 mm 3 volume, corrections for cerebrospinal fluid). Anatomical MRI and proton MRS revealed significant differences of the C57BL/6 strain in comparison with both BALB/c and NMRI mice. While MRI volumetry yielded larger ventricular spaces of the C57BL/6 strain, proton MRS resulted in elevated concentrations of N-acetylaspartate (tNAA), creatine and phosphocreatine (tCr), choline-containing compounds (Cho), glucose (Glc), and lactate (Lac) relative to BALB/c mice and elevated Glc relative to NMRI mice. Apart from the expected decrease of Glc and increase of Lac 1 hr post mortem, C57BL/6 mice presented with significant reductions of tNAA, tCr, and Cho, whereas these metabolites remained unchanged in BALB/c and NMRI mice. The results support the hypothesis that the more pronounced vulnerability of C57BL/6 mice to brain ischemia is linked to strain-dependent differences of the cerebral energy metabolism. Magn Reson Med 49:822-827, 2003.
Magnetic Resonance in Medicine, 2004
It is generally believed that the apparent diffusion coefficient (ADC) changes measured by diffus... more It is generally believed that the apparent diffusion coefficient (ADC) changes measured by diffusion-weighted imaging (DWI) in brain pathologies are related to alterations in the water compartments. The aim of this study was to elucidate the role of compartmentalization in DWI via biexponential analysis of the signal decay due to diffusion. DWI experiments were performed on mouse brain over an extended range of b-values (up to 10000 mm -2 s) under intact, global ischemic, and cold-injury conditions. DWI was additionally applied to centrifuged human erythrocyte samples with a negligible extracellular space. Biexponential signal decay was found to occur in the cortex of the intact mouse brain. During global ischemia, in addition to a drop in the ADC in both components, a shift from the volume fraction of the rapidly diffusing component to the slowly diffusing one was observed. In cold injury, the biexponential signal decay was still present despite the electron-microscopically validated disintegration of the membranes. The biexponential function was also applicable for fitting of the data obtained on erythrocyte samples. The results suggest that compartmentalization is not an essential feature of biexponential decay in diffusion experiments. Magn Reson Med 51:278 -285, 2004.
Magnetic Resonance in Medicine, 2001
The aim of our study was to establish a simple in vivo method for water quantification in vasogen... more The aim of our study was to establish a simple in vivo method for water quantification in vasogenic edema, and provide data on imaging of mouse brain at 9.4 Tesla. Apparent T 1 and spin density values determined by MRI were found to strongly correlate with the gravimetric water content of mouse brain undergoing cold injury. Using a two-point calibration line between the spin density values for pure water and cortex of mouse brain, as well as the corresponding water contents in vivo, water could be quantified with satisfactory accuracy. Magn Reson Med 46: 1246 -1249, 2001.
Magnetic Resonance Imaging, 2009
The purpose of this study was to investigate the effects of biophysical factors on the diffusion ... more The purpose of this study was to investigate the effects of biophysical factors on the diffusion and the relaxation time T 2 independently. Certain properties of the extracellular and the intracellular space may change radically in pathological conditions resulting in water diffusion changes. A tissue model consisting of red blood cells was studied. The extra-and intracellular spaces were modified osmotically and by suspending medium concentration. Diffusion measurements were evaluated with regard to the effective medium theory. Neither the nature of the protein in the extracellular space nor an increased level of intracellular hydration caused a significant net water diffusion change in the cell suspension. The relaxation time T 2 exhibited very little dependence on the extracellular volume fraction or the concentration or the nature of the protein in the extracellular space. An increased level of intracellular hydration resulted in systematically larger T 2 values. It seems probable that increases in extracellular protein concentrations or in the extent of intracellular hydration do not play a significant role in the diffusion changes detected in pathological conditions. T 2 appears to depend on the level of hydration or the total water content but is seemingly less dependent of the concentration and the nature of the extracellular protein in our model solutions.
Laterality: Asymmetries of Body, Brain and Cognition, 2011
There are contradictory results on lateralization and localization of rhythm processing. Our aim ... more There are contradictory results on lateralization and localization of rhythm processing. Our aim was to test whether there is a hemispheric dissociation of metric and non-metric rhythm processing. We created a non-metric rhythm stimuli without a sense of meter and we measured the brain activities during the passive rhythm perception.
Right–left discrimination is related to the right hemisphere
Laterality: Asymmetries of Body, Brain and Cognition, 2008
We aimed to determine the functional localisation of right-left discrimination (RLD) by functiona... more We aimed to determine the functional localisation of right-left discrimination (RLD) by functional MRI (fMRI). In this study, 16 male volunteers were examined. There were three task sessions: one active and two baseline tasks. During the baseline tasks participants were instructed to show numbers with their fingers. The first baseline task was performed with the right hand, the second one with the left hand. During the active (RLD) task participants were also instructed to show numbers. The difference between baseline and active tasks was that during the active task the hand with which the participant should perform the instruction was assigned randomly. Thus, participants were unaware which hand should be used before the instruction command. During RLD, activations occurred in the right-sided frontal, precuneus, postcentral, angular, lingual, and superior temporal gyri. Activations also appeared in the left-sided temporal gyri and precuneus. Of the activations, 76.7% appeared in the right hemisphere, 23.3% in the left hemisphere. Conclusively, we found that RLD is mainly related to the right hemisphere, and requires activation of the parieto-temporo-occipital junction and the visual system including cuneus, precuneus, and gyrus lingualis.
Multi-Modal Magnetic Resonance Imaging in the Acute and Sub-Acute Phase of Mild Traumatic Brain Injury: Can We See the Difference?
Journal of Neurotrauma, 2013
Advanced magnetic resonance imaging (MRI) methods were shown to be able to detect the subtle stru... more Advanced magnetic resonance imaging (MRI) methods were shown to be able to detect the subtle structural consequences of mild traumatic brain injury (mTBI). The objective of this study was to investigate the acute structural alterations and recovery after mTBI, using diffusion tensor imaging (DTI) to reveal axonal pathology, volumetric analysis, and susceptibility weighted imaging (SWI) to detect microhemorrhage. Fourteen patients with mTBI who had computed tomography with negative results underwent MRI within 3 days and 1 month after injury. High resolution T1-weighted imaging, DTI, and SWI, were performed at both time points. A control group of 14 matched volunteers were also examined following the same imaging protocol and time interval. Tract-Based Spatial Statistics (TBSS) were performed on DTI data to reveal group differences. T1-weighted images were fed into Freesurfer volumetric analysis. TBSS showed fractional anisotropy (FA) to be significantly (corrected p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05) lower, and mean diffusivity (MD) to be higher in the mTBI group in several white matter tracts (FA=40,737; MD=39,078 voxels) compared with controls at 72 hours after injury and still 1month later for FA. Longitudinal analysis revealed significant change (i.e., normalization) of FA and MD over 1 month dominantly in the left hemisphere (FA=3408; MD=7450 voxels). A significant (p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.05) decrease in cortical volumes (mean 1%) and increase in ventricular volumes (mean 3.4%) appeared at 1 month after injury in the mTBI group. SWI did not reveal microhemorrhage in our patients. Our findings present dynamic micro- and macrostructural changes occurring in the acute to sub-acute phase in mTBI, in very mildly injured patients lacking microhemorrhage detectable by SWI. These results underscore the importance of strictly defined image acquisition time points when performing MRI studies on patients with mTBI.
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Papers by Attila Schwarcz