Three step method for bilateral localization of hand motor cortex in functional magnetic resonance imaging (fMRI)

Society proceedings cal EEGs up to 24 channels. This low cost digital system allows the field of telephonic EEG to utilize QEEG. Neurologists, psychiatrists, small groups, or clinics can now provide QEEG services at their facility via digital telephonic EEG transmission. They can provide expanded neurodiagnostic services to their patients, and perform the professional interpretation. They will transmit to a central site which allows sharing of the costly analysis hardware, software, and qualified QEEG technicians. Dr. Schear is a major stock shareholder in TeleDiagnostic Systems. F130. Three step method for bilateral localization of hand motor cortex in functional magnetic resonance imaging (fMRI). Samuel R. Browda, Stella Legardab, Robin GilmoreC and Charles Widmerd (University of Florida, College of Medicine, Departments of aNeuroscience, bPediatrics, CNeurology, dCollege of Dentistry, Gainesville, FL 32610) Localization of specific motor homunculus representations is essential for accurate functional imaging when using a single slice subtraction image paradigm. We have used a three step method for accurately localizing and sampling homologous motor cortex activity in both hemispheres in fMR1 finger-tapping studies. Prior to fMR1 testing we acquire a Tl weighted whole-volume acquisition which is postprocessed into 3D renderings depicting cortical topography. The first fMR1 subtraction image is an oblique coronal aligned on a midsagittal scout. The 3D reconstruction is used (1) to identify the precentral gyrus (PreCG) on the midsgittal scout, (2) to determine the oblique slice angle representing the posterior to anterior descent of the left PreCG as it merges with the lateral sulcus. This protocol allows one subtraction slice to sample the entire left motor homunculus. After identifying the locus of left hemisphere activation, we take an axial subtraction image using a coronal scout. The axial subtraction image is oriented along a plane parallel to the anterior/posterior commissure and localized to the hand representation using coordinates of left motor homunculus activation Axial subtraction images are subsequently taken one slice above and below the original axial image to ensure the sampling of contralatera1 activation for interhemispheric comparison. F131: Visual and quantitative MRI evaluation of hippocampus and fornix in intractable complex partial epilepsy - Samuel R. Browd ’, Robin Gilmore2, Ronald Quisling3, Christina M. Leonard’, Steven N. Roper4, Timothy H. Lucas’ (‘University of Florida, College of Medicine, Departments of Neuroscience, 2Neurology, ‘Radiology, 4Neurosurgery, Gainesville, FL 32610-0244) Three MRI procedures were performed on 50 patients undergoing pre-surgical evaluation for intractable complex partial epilepsy. MRI procedures included: (1) visual evaluation of fast spin echo images for changes in hippocampal asymmetry/symmetry, hippocampal signal intensity, hippocampal atrophy, hippocampal subfield atrophy, and fornix atrophy. (2) hippocampal volumetrics on 1.25 mm sagittal Tl images; and (3) quantitative evaluation of T2 relaxation times, The sensitivity and positive predictive value (PPV) were defined by ictal scalp and/or invasive EEG, and outcome results. Preliminary analysis on 29 patients reveals that when EEG evaluation is ambiguous, MRI analysis contributes additional localizing information. To date, volumetric and visual assessment of abnormalities in hippocampi were both equally sensitive measures localizing 80% (16/20) of patients with temporal lobe epilepsy (TLE); however at least one of the three procedures correctly correlated with EEG localization in 85% (17/20 patients) of temporal lobe cases evaluated. No extra-temporal cases revealed abnormal hippocampal measures; however 2/5 cases considered non-local,izing by EEG were localized using MRI analysis. To date the PPV is 100%. Based on our complete findings from this study we will propose an optimal diagnostic imaging protocol in evaluating patients with uncontrolled seizures originating in the temporal lobe.

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F132: Magnetic source imaging of epileptic spikes compared with pre-surgical and intra-operative invasive monitoring *Maung Aung, **Barry J. Schwartz, *David F. Sobel, **Eugene Hirschkoff, and **Floyd E. Bloom (*The Scripps Clinic and Research Foundation, La Jolla, CA; **The Scripps Research Institute, La Jolla, CA) As part of a multi-center study involving 100 patients, 20 seizure surgery candidates have been measured using a dual 37.channel biomagnetometer (total 74 channels) system along with 21 channels of surface EEG. Locations of sources of spike activity were derived from the magnetic fields using a single equivalent dipole model and were then mapped onto MR slices as magnetic source images (MSI). The results were compared with those from recordings using phase 11 subdural grids or depth electrodes. Assessments of epileptic foci using MS1 showed strong agreement with the invasive procedures. Where available, post-surgical follow ups were made. Results suggest that biomagnetic spike locahzations are sensitive and accurate in comparison to conventional invasive procedures, and may be used to aid in planning surgery and in the presurgical placement of subdural electrodes. Drs. Schwartz and Hirschkoff are employees of Biomagnetic Technologies. F133: Clinical utility of interictal quantitative EEG in epilepsy Miles E. Drake, Jr., J. Layne Moore, Ann Pakalnis, and G.S. Mallik (The Ohio State University Medical Center, Columbus, Ohio) The interictal EEG is often normal in epilepsy patients, particularly with partial seizures of extratemporal origin. Quantitative techniques of EEG analysis may increase the yield of diagnostic abnormality in such patients. Thirty patients with partial seizures of frontal or temporal origin had EEG recorded from left frontal (F7C3) right frontal (F&t), left posterior (Tg-01) and right posterior (Tg-02) derivations. Four second epochs were used to compute power in the delta (0.25-4.0 Hz), theta (4.25-8.0 Hz) alpha (8.25-13 Hz) and beta (13.25-30 Hz) bands. The ratio of high (8.25-30 Hz) to low (0.25-8.0 Hz) power on left and right was measured, as was the ratio between left and right hemisphere total power. The mean frequency deviation in the alpha band between left and right hemispheres was also measured, and spectral mobility determined in the right and left frontal regions. These values were also calculated in normal subjects and in tension headache patients with normal EEGs, for a total of 20 controls. Seizure patients with abnormal interictal EEGs had increased slow power and greater interhemispheric alpha asymmetry ipsilateral to the EEG focus. These asymmetries were also present to a lesser extent in patients with a normal interictal EEG. Spectral mobility was reduced ipsilateral to an epileptogenic focus and was also reduced unilaterally in patients with normal EEGs in comparison to normal controls. Supported in part by the Davis Medical Research Foundation, The Ohio State University College of Medicine. F134:

Clinical utility of intraoperative electrocortiography for localization of low grade glioma - Gunwant Mallik”, Michael E. Miner”, Miles E. Drake, Jr.b, J. Layne Mooreb (“The Ohio State University Division of Neurosurgery; bThe Ohio State University Division of Epilepsy)

EEG has been shown to be reliable in localizing superficial cerebral hemisphere tumors. With the recent advances in neuroimaging, the clinical use of EEG has radically diminished. However, electrocortiography (ECOG) can be a significant tool in tumor localization when conventional intraoperative ultrasound has been helpful but is limited in noncalcified homogenous low grade gliomas. We present a case in which intraoperative ultrasound was not helpful m localization of low grade glioma that was successfully biopsied using intraoperative ECOG. M.S. is a 47 year old male who presented with left-sided