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186. Individual assessment of chronic brain tissue changes in MRI – The role of focal lesions for brain atrophy development. A voxel-guided morphometry study
Society Proceedings / Clinical Neurophysiology 120 (2009) e9–e88
The development of a computer-based algorithm enables a more reliable classification of these EEG-vigilance stages than a visual inspection of EEG data does. These EEG-vigilance stages were used as regressors for the analysis of the simultaneous functional magnetic resonance imaging (fMRI) and EEG measurements in healthy controls. It has been found that the occurrence of occipital, parietal and frontal BOLD signal patterns are associated with the different EEG vigilance stages. Resting state networks and their temporal dynamics seem to be related to the EEG-vigilance levels. Further, the EEG-vigilance classification has been used to analyze differences in the timecourse of EEG-vigilance stages in patients with obsessive compulsive disorder (OCD), borderline patients and healthy controls. Borderline patients more often exhibit a labile vigilance regulation with a faster vigilance decrease over time than patients suffering from OCD. These results provide evidence that the EEG-vigilance stages and the regulation of these functional brain states can be used to investigate pathological mechanisms of vigilance regulation in different psychiatric disorders. doi:10.1016/j.clinph.2008.07.183
186. Individual assessment of chronic brain tissue changes in MRI – The role of focal lesions for brain atrophy development. A voxel-guided morphometry study—M. Kraemer 1, T. Schormann 2, A. Dabringhaus 1, J. Hirsch 3, K.M. Stephan 1, V. Hömberg 1, L. Kappos 4, A. Gass 3 (1 St. Mauritius Therapieklinik, Neurologie, Meerbusch, Germany, 2 Institut für Anatomie I, Düsseldorf, Germany, 3 Universitätsspital, Neuroradiologie, Basel, Schweiz, 4 Universitätsspital, Neurologie, Basel, Schweiz) Despite considerable progress in the treatment of MS, it is still the most frequent cause of neurological disability in young and middle-aged adults. The known neuropathological mechanisms leading to progressive disability are immune-mediated demyelination and axonal loss. Several MRI studies demonstrated brain volume reduction, consisting of white and grey matter loss as an in vivo marker of MS. As this brain atrophy is positively correlated with disability, atrophy measures have been adopted as secondary outcomes in a number of trials of disease-modifying drugs. As neurodegeneration is irreversible, brain atrophy measurements may be viewed as an important biomarker of MS brain pathology. In our study we used a new method Voxel-Guided Morphometry (VGM) for detailed individual and focal assessment of brain structural changes in 100 MS patients. The method combines high accurracy resulting in the detection of structural changes <1 mm with high reproducibility due to a fully automated analysis procedure and the possibility of individual morphometrical assessments. Corresponding 3D MRI scans of each individual were segmented for the removement of non-brain structures and were aligned to each other. Using a four-step procedure, exact comparisons of local brain volume were performed (IEEE TMI, 22: 62–74, 2003). In short, the 4 steps are (1) coarse linear alignment by use of the extended principle axes theory (ePAT) generalized to affine movements; (2) a cross-correlation-based technique using a matrix-norm for fine linear alignment; (3) application of a high-dimensional multiresolution full multigrid method for the determination of nonlinear deformations, thereby achieving complete exploitation of information and effective processing; and (4) the determination of volume alterations between two brains imaged 12 months apart and visualization using color scale encoding.
e77
To assess brain volume changes, two time points 12 months apart were analysed for each patient. Focal as well as widespread brain volume changes were detected in the consecutive MRI scans of the 100 individuals. Preliminary results of the analysis of patients that developed a new lesion during the 1 year interscan period demonstrate that new lesions are detected with a high sensitivity by VGM. It was also shown that large parts of the brain beyond the lesion site appear morphologically stable. CSF structures close to the lesion were enlarged in size, corresponding to focal brain was affected and showed a slight otherwise invisible volume decrease. These changes were related to the location of the lesion but extended up to adjacent white matter and cortical areas, demonstrating the remote effects of the focal lesion on brain morphology. In summary, VGM demonstrated focal brain structure alterations after the development of new lesions in MS patients. These structural changes included the detection of the lesion itself with high sensitivity as well as morphological alterations exceeding the lesion itself that could not be detected otherwise. Thus, VGM provides some information on the mechanisms of brain atrophy development and may be a suitable method for individual high accuracy detection of focal brain volume changes in MS patients over time. doi:10.1016/j.clinph.2008.07.184
187. Intraoperative subcortical stimulation and fiber tracking: Does the stimulation current predict the distance to subcortical fibers?—J. Rathert 1, A. Szelenyi 1, E. Hattingen 2, T. Gasser 1, C. Senft 1, V. Seifert 1, A. Raabe 1 (1 Johann Wolfgang Goethe-Universität, Klinik und Poliklinik für Neurochirurgie, Frankfurt a. M., Germany, 2 Johann Wolfgang Goethe-Universität, Institut für Neuroradiologie, Frankfurt a. M., Germany) Objective: In subcortical glioma surgery, preservation of fibers originating in the precentral gyrus is still challenging. Preoperative DTI-based fiber tracking allows an approximation of the course of fibers but it is intraoperatively limited due to brain shift. Therefore, the intraoperative cortical and subcortical elicitation of motorevoked potentials (MEPs) is commonly used to localize and continuously evaluate in real time the function and integrity of these fibers. The disappearance of MEP or the increase of the motor threshold is a strong predictor for postoperative morbidity. The correlation between stimulating current and distance from the stimulation site to the stimulated fibers is evaluated. Methods: In 11 patients with deep white matter lesions adjacent to the corticospinal tract (CTS), fiber tracking of the CTS was done pre- and postoperative. Therefore fMRI of the motor cortex and diffusion tensor imaging (12 different directions) were acquired employing a 3 T MR-scanner. Fiber tracking was performed according to the anatomical and functional data sets with separate segmentation of the CTS relating to the foot-, hand- and tongue-motor-area. The resulting bundle was confirmed by anatomical landmarks and segmented three-dimensionally (iPlan 2.5Cranial, BrainLabÒ, Feldkirchen). During and at the end of tumor resection, monopolar subcortical stimulation (five pulses, cathodal, 0.5 ms monophasic pulsewidth, ISI = 4 ms) in the resection cavity was performed alongside of the course of fibers, starting with 20 mA and decreasing to the lowest current with a MEP response. After postoperative fiber tracking and fusion with anatomical imaging, the shortest distance between the resection cavity and the CTS bundles was three-dimensional by measured and correlated
The development of a computer-based algorithm enables a more reliable classification of these EEG-vigilance stages than a visual inspection of EEG data does. These EEG-vigilance stages were used as regressors for the analysis of the simultaneous functional magnetic resonance imaging (fMRI) and EEG measurements in healthy controls. It has been found that the occurrence of occipital, parietal and frontal BOLD signal patterns are associated with the different EEG vigilance stages. Resting state networks and their temporal dynamics seem to be related to the EEG-vigilance levels. Further, the EEG-vigilance classification has been used to analyze differences in the timecourse of EEG-vigilance stages in patients with obsessive compulsive disorder (OCD), borderline patients and healthy controls. Borderline patients more often exhibit a labile vigilance regulation with a faster vigilance decrease over time than patients suffering from OCD. These results provide evidence that the EEG-vigilance stages and the regulation of these functional brain states can be used to investigate pathological mechanisms of vigilance regulation in different psychiatric disorders. doi:10.1016/j.clinph.2008.07.183
186. Individual assessment of chronic brain tissue changes in MRI – The role of focal lesions for brain atrophy development. A voxel-guided morphometry study—M. Kraemer 1, T. Schormann 2, A. Dabringhaus 1, J. Hirsch 3, K.M. Stephan 1, V. Hömberg 1, L. Kappos 4, A. Gass 3 (1 St. Mauritius Therapieklinik, Neurologie, Meerbusch, Germany, 2 Institut für Anatomie I, Düsseldorf, Germany, 3 Universitätsspital, Neuroradiologie, Basel, Schweiz, 4 Universitätsspital, Neurologie, Basel, Schweiz) Despite considerable progress in the treatment of MS, it is still the most frequent cause of neurological disability in young and middle-aged adults. The known neuropathological mechanisms leading to progressive disability are immune-mediated demyelination and axonal loss. Several MRI studies demonstrated brain volume reduction, consisting of white and grey matter loss as an in vivo marker of MS. As this brain atrophy is positively correlated with disability, atrophy measures have been adopted as secondary outcomes in a number of trials of disease-modifying drugs. As neurodegeneration is irreversible, brain atrophy measurements may be viewed as an important biomarker of MS brain pathology. In our study we used a new method Voxel-Guided Morphometry (VGM) for detailed individual and focal assessment of brain structural changes in 100 MS patients. The method combines high accurracy resulting in the detection of structural changes <1 mm with high reproducibility due to a fully automated analysis procedure and the possibility of individual morphometrical assessments. Corresponding 3D MRI scans of each individual were segmented for the removement of non-brain structures and were aligned to each other. Using a four-step procedure, exact comparisons of local brain volume were performed (IEEE TMI, 22: 62–74, 2003). In short, the 4 steps are (1) coarse linear alignment by use of the extended principle axes theory (ePAT) generalized to affine movements; (2) a cross-correlation-based technique using a matrix-norm for fine linear alignment; (3) application of a high-dimensional multiresolution full multigrid method for the determination of nonlinear deformations, thereby achieving complete exploitation of information and effective processing; and (4) the determination of volume alterations between two brains imaged 12 months apart and visualization using color scale encoding.
e77
To assess brain volume changes, two time points 12 months apart were analysed for each patient. Focal as well as widespread brain volume changes were detected in the consecutive MRI scans of the 100 individuals. Preliminary results of the analysis of patients that developed a new lesion during the 1 year interscan period demonstrate that new lesions are detected with a high sensitivity by VGM. It was also shown that large parts of the brain beyond the lesion site appear morphologically stable. CSF structures close to the lesion were enlarged in size, corresponding to focal brain was affected and showed a slight otherwise invisible volume decrease. These changes were related to the location of the lesion but extended up to adjacent white matter and cortical areas, demonstrating the remote effects of the focal lesion on brain morphology. In summary, VGM demonstrated focal brain structure alterations after the development of new lesions in MS patients. These structural changes included the detection of the lesion itself with high sensitivity as well as morphological alterations exceeding the lesion itself that could not be detected otherwise. Thus, VGM provides some information on the mechanisms of brain atrophy development and may be a suitable method for individual high accuracy detection of focal brain volume changes in MS patients over time. doi:10.1016/j.clinph.2008.07.184
187. Intraoperative subcortical stimulation and fiber tracking: Does the stimulation current predict the distance to subcortical fibers?—J. Rathert 1, A. Szelenyi 1, E. Hattingen 2, T. Gasser 1, C. Senft 1, V. Seifert 1, A. Raabe 1 (1 Johann Wolfgang Goethe-Universität, Klinik und Poliklinik für Neurochirurgie, Frankfurt a. M., Germany, 2 Johann Wolfgang Goethe-Universität, Institut für Neuroradiologie, Frankfurt a. M., Germany) Objective: In subcortical glioma surgery, preservation of fibers originating in the precentral gyrus is still challenging. Preoperative DTI-based fiber tracking allows an approximation of the course of fibers but it is intraoperatively limited due to brain shift. Therefore, the intraoperative cortical and subcortical elicitation of motorevoked potentials (MEPs) is commonly used to localize and continuously evaluate in real time the function and integrity of these fibers. The disappearance of MEP or the increase of the motor threshold is a strong predictor for postoperative morbidity. The correlation between stimulating current and distance from the stimulation site to the stimulated fibers is evaluated. Methods: In 11 patients with deep white matter lesions adjacent to the corticospinal tract (CTS), fiber tracking of the CTS was done pre- and postoperative. Therefore fMRI of the motor cortex and diffusion tensor imaging (12 different directions) were acquired employing a 3 T MR-scanner. Fiber tracking was performed according to the anatomical and functional data sets with separate segmentation of the CTS relating to the foot-, hand- and tongue-motor-area. The resulting bundle was confirmed by anatomical landmarks and segmented three-dimensionally (iPlan 2.5Cranial, BrainLabÒ, Feldkirchen). During and at the end of tumor resection, monopolar subcortical stimulation (five pulses, cathodal, 0.5 ms monophasic pulsewidth, ISI = 4 ms) in the resection cavity was performed alongside of the course of fibers, starting with 20 mA and decreasing to the lowest current with a MEP response. After postoperative fiber tracking and fusion with anatomical imaging, the shortest distance between the resection cavity and the CTS bundles was three-dimensional by measured and correlated