Advanced Imaging of Stroke, Epilepsy & Traumatic Brain Injury
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Wednesday 9 May 2012
Room 202  10:00 - 12:00 Moderators: Yulin Ge, Pratik Mukherjee

10:00 0368.   
Functional MRI in stroke following tDCS and brain-computer interface-assisted motor imagery rehabilitation
Irvin Teh1, Cuntai Guan2, Kai Keng Ang2, Kok Soon Phua2, Ling Zhao3, Chang Wu Chen3, and Effie Chew3
1A*STAR-NUS Clinical Imaging Research Centre, Singapore, Singapore, 2Institute for Infocomm Research, A*STAR, Singapore, Singapore, 3National University Health System, Singapore, Singapore

We investigated the imaging outcomes of a novel approach combining transcranial direct current stimulation (tDCS) with robot-assisted motor imagery and brain-computer interface (MI-BCI) therapy to facilitate motor recovery in chronic stroke patients with upper limb impairment. fMRI data showed reduced activation in bilateral SM1, PMC and SMA and increased activation in the SMA, contralateral SM1, ipsilateral PMC and PPC during a calibrated hand squeeze task of the unaffected and affected hand respectively. These findings were consistent with our transcranial magnetic stimulation (TMS) data, and present evidence of training-induced cortical plasticity that underscore its therapeutic potential to chronic stroke rehabilitation.

10:12 0369.   Enhancement of Functional Connectivity within Contralesional Hemisphere after Recovery of Stroke
Woo Hyun Shim1, Bruce Rosen2, Jaeseung Jeong1, and Young Ro Kim2
1Bio & Brain, Korea Advanced Institute of Science and Technology, (KAIST), Daejoen, Daejoen, Korea, Republic of, 2Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, United States

The restorative mechanism of stroke has been of high interest but has not yet been fully understood. In this regard, we investigated both task-induced fMRI responses and resting-state connectivity using the rat models recovered from impaired sensorimotor functions after severe ischemic stroke. Our results show that the electrical stimulation of stroke affected forelimbs induce no fMRI responses in the entire brain and also demonstrate the markedly increased functional connectivity in the contralesional (non-stroke) hemisphere. This result implies that the restoration of sensorimotor function may be associated with the increase and spatial expansion of functional connectivity mostly within the contralesional hemisphere.

10:24 0370.   Brain Rhythms Alterations and their effect in Functional Networks: A Simultaneous EEG/fMRI Study in Fixation-Off Epilepsy
Ana Beatriz Solana1, Juan Antonio Hernández-Tamames1, Elena Molina1, Kenia Martínez2, Juan José Alcalá1, Rafael Toledano3, Victoria San Antonio-Arce3, Irene García-Morales3, Antonio Gil-Nagel3, Ceferino Maestu1, Juan Alvarez-Linera3, Eva Alfayate4, and Francisco del Pozo1
1Neuroimaging lab., Center for Biomedical Technology - Universidad Politécnica de Madrid and Universidad Rey Juan Carlos, Pozuelo de Alarcón, Madrid, Spain, 2Universidad Autónoma de Madrid, Madrid, Spain, 3Hospital Ruber Internacional, Madrid, Spain, 4Fundación Reina Sofía - Fundación CIEN, Madrid, Spain

The underlying mechanisms of Fixation Off Sensitivity and the characterization of a pure FOS epilepsy remain unclear. Here, we performed simultaneous EEG-fMRI in two FOS patients. The power fluctuations of the EEG rhythms were used in the fMRI analyses as regressores. Results showed different electrical patterns for both patients after eyes closure indicating different kind of FOS. Patient’s fMRI beta band maps included not only brain areas previously reported to be related to beta in control subjects, but also brain regions related to alpha. This finding suggests an alteration in the attentional networks in these patients.

10:36 0371.   Imaging of pentylenetetrazol-induced seizures by fMRI: a novel method for detecting seizure onset zone in experimental post-traumatic epilepsy permission withheld
Antti M Airaksinen1, Joanna K Huttunen1, Artem Shatillo1, Juha-Pekka Niskanen1,2, Asla Pitkänen3,4, and Olli Gröhn1
1Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland, 2Department of Applied Physics, University of Eastern Finland, Kuopio, Finland, 3Department of Neurobiology, Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sci, University of Eastern Finland, Kuopio, Finland, 4Department of Neurology, Kuopio University Hospital, Kuopio, Finland

The aim of the study was to investigate onset region for pentylenetetrazol-induced seizures after traumatic brain injury (TBI) utilizing simultaneous local field potential (LFP) and fMRI measurements. In all animals, PTZ caused detectable responses in BOLD and LFP signals. PTZ induced seizures originate from the periphery of the lesion in 7/13 animals 2 months after TBI and bilaterally in the cortex in all sham operated rats.

10:48 0372.   
Network analysis of resting-state fMRI reveals increased centrality in regions generating focal epileptiform spikes
Richard Masterton1, and Graeme Jackson1,2
1Brain Research Institute, Florey Neuroscience Institutes, Melbourne, Victoria, Australia, 2The University of Melbourne, Melbourne, Victoria, Australia

A data-driven network analysis of resting-state fMRI applied to patients with benign rolandic epilepsy. Network nodes identified with high centrality provided good correspondence with the presumed epileptogenic zone in these non-lesional focal epilepsy patients.

11:00 0373.   Resting State fMRI Reveals Altered Functional Connectivity in Cortical and Subcortical Networks One Month after Mild Traumatic Brain Injury
Yi-Ou Li1, Sara LaHue1,2, Roger Chen1, Shelly Cooper1,2, John Yue1,2, Geoffrey Manley2, and Pratik Mukherjee1
1Radiology, University of California San Francisco, San Francisco, CA, United States, 2Neurosurgery, University of California San Francisco, San Francisco, CA, United States

Based on current studies of functional connectivity after traumatic brain injury (TBI), we focus on 14 brain regions and apply seed region correlation analysis to the resting state fMRI of 51 mild brain trauma patients one month after injury and 45 demographically matched healthy controls. The statistical tests on the brain connectivity maps reveal reduced functional connectivity of multiple networks, most prominently the default mode network and hippocampus; however, connectivity is increased in a motor-SMA network that includes the dACC. These initial results demonstrate that resting state fMRI has promise as an imaging biomarker for clinical outcome after mild TBI.

11:12 0374.   Small World Properties Changes in Mild Traumatic Brain Injury (MTBI)
Yongxia Zhou1, Yulin Ge1, Yvonne W Lui1, Joseph Reaume1, and Robert I Grossman1
1Radiology/CBI, New York University Langone Medical Center, New York, NY, United States

Small world properties such as betweenness centrality and clustering coefficient based on resting-state fMRI were used to evaluate global and local efficiency changes in 33 MTBI patients compared to 45 controls, and their changes were correlated with axonal injury by diffusion tensor imaging and postconcussive syndrome (PCS) in patients. We found reduced betweenness centrality and increased clustering coefficient in patients and these abnormalities correlated with white matter fractional anisotropy reductions and PCS. Our results suggest that disrupted global axonal integrity may cause decreased global efficiency of neuronal source utilization accompanying with local network upregulation as a compensatory mechanism in MTBI.

11:24 0375.   High-sensitivity and High-specificity of Traumatic Brain Injury diagnostic method using Magnetic Resonance Imaging – Diffusion Tensor Imaging
Keumsil Lee1, Varin Tsai1, Steven Potkin1, and Joseph Wu1
1Brain Imaging Center, Psychiatry and Human Behavior, University of California, Irvine, Irvine, CA, United States

Traumatic brain injury (TBI) is a leading cause of injury, death, and disability in the United States. The purpose of this study is to improve sensitivity and specificity in diagnosing the TBI patients by finding out the white matter (WM) abnormality based on the MRI DTI images. Fractional anisotropy (FA) is the measure of the WM tract directionality. When the directionality and/or connectivity of the WM tracts are altered, the patients are likely to have a neurological abnormality. By providing the patterns of white matter abnormality for TBI patients, characterization of TBI can be achieved with high-sensitivity and high-specificity.

11:36 0376.   
A longitudinal evaluation of diffusion kurtosis imaging in patients with mild traumatic brain injury
Jesse A Stokum1, Jiachen Zhuo1, Jacqueline Janowich1, and Rao Gullapalli1
1Magnetic Resonance Research Center, Department of Radiology & Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States

Diffusion kurtosis imaging (DKI) has been shown to be sensitive to microstructural changes and may provide additional information that complements information from diffusion tensor imaging (DTI) in evaluation of traumatic brain injury (TBI). In this prospective study, parameters from these techniques were evaluated on 36 patients who suffered mild TBI at three time points following injury in gray and white matter regions and were compared with reaction times on neurocognitive tests. DKI parameters in the internal capsule appear to be sensitive to the underlying demyelination pathological changes and are inversely correlated with reaction times on neurocognitive tests.

11:48 0377.   Quantitative Susceptibility Mapping of Hemorrhages in TBI Using the 3D multi-echo Gradient Echo MRI at 3T
Haiying Tang1, Tian Liu2, Wei Liu3, Hai Pan3, Reed Selwyn1, Terry Oakes4, Yi Wang2, and Gerard Riedy4
1Radiology, Uniformed Services University of the Health Sciences, Bethesda, MD, United States, 2Biomedical Engineering, Cornell University, New York, NY, United States, 3Center for Neuroscience and Regenerative Medicine, Henry M Jackson Foundation, Bethesda, MD, United States, 4National Intrepid Center of Excellence, Walter Reed National Military Medical Center, Bethesda, MD, United States

In the military, the Iraq and Afghanistan wars have potentially exposed more than 300,000 soldiers to mild traumatic brain injury (TBI), with more than 45,000 soldiers diagnosed with TBIs. The true incidence of TBI in the military is unknown since many cases, especially mild TBI, will have negative findings using typical clinical imaging protocols. Diagnosis of TBI with high sensitivity and specificity is a top priority for military medicine. Diffuse axonal injury (DAI), marked by petechial hemorrhage, is a trademark brain injury following blast-induced and acceleration brain movements and is not observable using conventional MRI or CT. Yet, susceptibility weighted imaging (SWI) and quantitative susceptibility mapping (QSM) can detect and quantify petechial hemorrhages, iron deposition, and calcifications that may predict DAI. We hypothesize that QSM will provide new information that is not obtained using other quantitative imaging, such as diffusion tensor imaging (DTI), which is quickly becoming the de facto standard for TBI imaging.