Abstracts

Rationale: Acquired brain insults, such as stroke, could result in the development of epilepsy. Stroke-related epilepsy is relatively understudied. Our goal is to explore a correlation between post-stroke epilepsy (PSE) and surrogate measures of network reorganization after cortical motor stroke in humans. Towards this end, we have compared the functional connectivity of the motor network, measured using resting state functional MRI (rsfMRI), in stroke patients with and without epilepsy. Methods: Subjects: We enrolled three patient groups in our studies: 1. Patients with post-stroke central motor epilepsy (PSE) (as determined by electroclinical and MRI criteria); 2. Patients with a history of stroke without epilepsy (SwoE); 3. Age and health-matched controls. MRI Image Acquisition: Scanning is performed with a 3.0 T scanner using a EPI sequence sensitive to BOLD contrast with a TR of 3 seconds for 30 minutes. For resting state studies, the subject is asked to lay still and refrain from sleep. fMRI acquisition is also acquired during the performance of a finger-tapping task. Data Analysis: Activations from the motor task are used to identify the nodes of the motor network for use as seed regions for revealing resting motor networks. To generate functional connectivity maps, we will compute connectivity values between each pair of nodes in the network. Comparison between the groups is assessed in a repeated measures analysis of variance. t tests are calculated to identify significant differences in coupling between the subject groups (p<0.05). Results: We studied 3 PSE patients and 3 normal controls to date (goal is 10 per group). Qualitative observations from the motor task in controls revealed several regions of activation including primary motor cortex (M1), supplementary motor area (SMA), primary and secondary sensory areas (S1/S2), thalamus, and cerebellum. This pattern of activation was similar in the PSE patients using the non-paretic hand (compare Fig 1D with 1C). However, there was a different pattern of activation in the PSE patients using the paretic hand: fewer subcortical areas were activated; cortically, there was bilateral M1 and SMA activation including significant activation of the normal, contra-lesional hemisphere in 2 out of 3 subjects (Fig 1A). We recently started analyzing the resting state data in controls using M1 as ROI. As expected, this task-free analysis identified bilateral elements of the motor network (Fig 2). Conclusions: 1. The motor task identified expected motor areas of activation in controls and aberrant activation of the unaffected hemisphere after stroke, 2. Resting state analysis revealed bilateral elements of the motor network in controls. In order to establish a possible correlation with epilepsy, our next steps are to quantify the inter-regional connectivities and perform group comparisons. This study could significantly impact the care of post-stroke epilepsy patients by developing therapy and prognosis-guiding biomarkers.