Abstracts

Rationale: MCD are a common cause of intractable focal epilepsy. Studies of structural MRIs and PET data have found widespread changes outside the visually identified lesions. Furthermore, studies using MEG have suggested a reorganization of functional cortex in some of these MCDs. Methods: Patients with MCD attending our Epilepsy Program were enrolled. The diagnosis of MCD was done by standard 1.5T anatomical MRI during epilepsy presurgical evaluation. All patients later underwent 3T fMRI studies during somatosensory stimulation and finger tapping, MRS and DTI. Somatosensory stimulation was carried out using repetitive tactile stimulation applied by a painless pneumatic pressure device that was clipped to a given hand digit. The three-dimensional locations of the center of gravity for the somatosensory and motor cortices in each hemisphere were identified in the MNI map, using SPM 2 software. Also, peak percent of signal change, and percent of cluster changes in Brodman areas (BA) 4 and 6 were obtained for each case and compared with controls. Localization of somatosensory and motor areas were identified in 10 healthy controls and compared with cases. Random effect analysis was applied to compare each patient with all 10 controls. We also compared the DTI and spectroscopic results with control data, with the latter one for detection of significant abnormalities for Cr/NA ratio and Cho/Cr. Results: 5 patients were enrolled (2 with polymicrogyria, 2 with cortical dysplasia, and 1 with schizencephaly and polymicrogyria). Areas of abnormal anisotropy were found in all patients on DTI. Patients with focal cortical dysplasia showed metabolic abnormalities in correspondence with the structural lesions, whereas patients with heterotopia and polymicrogyria did not. The activation of the motor cortex during left finger tapping was found to be located in the right hemisphere in all patients, with the exception of one patient (schizencephaly and polymicrogyria), which was found in the ipsilateral hemisphere. During finger tapping, we found in the controls a peak % of signal change at the center of gravity of 1.188% (right finger tapping), 2.031% (left finger tapping), and 0.743% (left fingers sensory stimulation); 60.5% (right finger tapping), 39.5% (left finger tapping), and 60.5% (left finger stimulation) percent cluster change were found in BA 6, and 23.7% (right finger tapping), 9.8% (left finger tapping) and 4.7%(left finger sensory stimulation) in BA 4. There was an average increase of 1.08 (right finger tapping), 0.84 (left finger tapping), and 0.48 (left sensory stimulation) in the peak percent of signal change in all patients with respect to the controls, 7.88% average decrease in the percent of cluster changes at BA 6, and there was no activation at BA 4 in 4 patients. Conclusions: These preliminary findings suggest that MRSI-based metabolic abnormalities, changes in diffusion, and the localization of functional cortex analyzed with fMRI, in patients with MCDs are variable and are likely to be associated with complex cellular mechanisms.