Abstracts

Rationale: Malformations of cortical development (MCDs) are disturbances in brain formation that arise from abnormalities affecting the processes of cortical development and involve cells that under normal circumstances would participate in formation of the cerebral cortex. Medically-intractable Epilepsy has been increasingly associated with MCDs. Functional MR (fMRI) may have the potential to detect structural reorganization patterns in patients with MCDs. The purpose of this study is to determine whether functional reorganization of primary sensorimotor cortex occurs in patients with epileptogenic malformations of cortical development of the rolandic and perirolandic regions and to evaluate the use of functional MRI as a tool for the assessment of brain reorganization due to malformations of cortical development.Methods: Sensory fMRI data were obtained for seven controls and nine patients (cortical dysplasia, polymicrogyria, and heterotopia). Data were acquired on a 3.0T Siemens Magnetom Tim Trio MRI, using a 12 channel head RF coil. fMRI data were acquired with a multi-slice EPI pulse sequence (repetition time (TR)/Echo time (TE) = 3200/25 ms, acquisition matrix 64x64, 5 mm isotropic resolution). A total of 132 image sets were collected, divided into 7 task-rest cycles with 12 sets in each state. For evaluation of the somatosensory cortex, the skin of each palm was stimulated avoiding movement of the hand and fingers. The analysis of the information obtained from the fMRI was completed using SPM2. Results: The fMRI response of the control subjects exhibited typical responses to sensory stimuli as found in literature. Significant clusters of activation were found in the primary somatosensory cortex (SI), the secondary somatosensory cortex (SII), the precentral gyrus, posterior insula, posterior parietal regions and the posterior cingulate. Figure 1 shows primary sensory cortex activations in a subset of 4 right handed patients and controls. There was a decrease and reorganization of activation in the sensory cortex for dominant hand (DH) and/or non-dominant hand (NDH) tasks in patients compared to controls. Evidence of neuronal dysfunction in patients with MCD may have relevance for the mechanisms of seizure generation in these forms of epilepsy. Conclusions: This preliminary study demonstrates the presence of cortical reorganization in patients with MCDs in comparison to control subjects. The small sample size did not allow specific analysis of each group of malformations. Further recruitment is necessary as there may be some particular findings pertaining to each different type of MCDs. fMRI data will also be compared to intracranial EEG mapping of cortical function to test its effectiveness as a pre-surgical evaluation tool. Funding for this project was provided by the Ontario Brain Institute Epilepsy Discovery Project.