Abstracts

Rationale: Motor cortex can undergo significant reorganization in patients with a variety of neurological diseases. Reorganization of language networks has also been shown in patients with temporal lobe epilepsy (Jensen et al. 2011, Epilepsia 52:2013-2021; Jensen et al. 2011, Epilepsy Res 93:155-163), but such reorganization has not been demonstrated to date in human subjects with frontal lobe epilepsy (FLE). FLE may cause subtle changes in motor cortex organization, which could explain functional motor deficits experienced by these patients. Indeed, experimentally induced seizures in animals produce abnormal expansion of movement representations within the motor cortex (Teskey et al. 2002, Cereb Cortex 12:98-105). However, it is not known whether such reorganization occurs specifically in humans and if this would allow for the maintenance of normal motor function. Therefore, cortical motor organization in patients with FLE was studied using functional magnetic resonance imaging (fMRI). Methods: Ten subjects with right FLE and ten control subjects were studied. All participants were right handed and between the ages of 18 and 65. fMRI was performed at 3T and participants underwent a series of hand movement sequences. The first task required participants to tap their fingers in time with a visual stimulus, both unimanually and bimanually. The second task required participants to execute a series of coordinated unimanual or bimanual hand movements as instructed by visual stimuli. Each task involved 6 runs of 12 movements per run, taking approximately one hour to complete. fMRI data was analyzed using standard methods, and first level analysis for each task was then entered into three separate group analyses with subject group (right FLE, control) and motor task (right/left unimanual, bimanual) entered as variables. Maps were generated for each task to determine brain regions exhibiting a significant difference in response magnitude between groups and tasks (Z>2.3, corrected cluster significance p=0.05). Results: Patients with right FLE had significantly decreased activation in the hemisphere ipsilateral to the seizure focus during the bimanual and left handed finger-tapping tasks compared to controls. Patients with right FLE had significantly increased activation in the hemisphere contralateral to the seizure focus during the bimanual and left-handed coordination tasks compared to controls. No significant difference was found between patients with right FLE and controls during the right-handed tasks. Conclusions: Reorganization of the motor cortex occurs in patients with right FLE, therefore giving us a better understanding of the long-term effects of FLE on cortical organization. The possibility that seizures induce brain reorganization has important implications for epilepsy surgery, and supports the notion that a combination of methods, including fMRI, should be used when brain mapping is required.