Abstracts

Rationale: Simultaneous functional MRI (fMRI) and EEG is increasingly being used as a multimodal tool in epilepsy research [1]. Spike timings identified in EEG signals can be used to generate functional images in fMRI and localize spike activation within the brain. This technique has been used to identify brain regions that are associated with interictal activity and may be assessed for target identification for surgical resection [2]. It is important in surgical decision making to not only identify a focal target for resection but also to investigate possible networks of epileptogenic activity. We use functional connectivity with epileptic focal target as the seed to investigate brain networks associated with that focal region.Methods: Thirty eight subjects with intractable epilepsy who were candidates for epileptogenic resection were scanned using a simultaneous fMRI-EEG protocol. Resting state fMRI data were collected on a Siemens MRI scanner using 10 min. runs with 64x64 matrix, alpha=80, TE/TR=30/1550ms. Interictal spike activity timings in their EEGs were visually identified and used in an event-related fMRI analysis to generate functional images of epileptic focal points. These focal points were then used as seed region in the functional connectivity analysis covering the entire brain. The 3D connectivity map was obtained by first averaging the fMRI time activities in the focal region and correlating it with time activities from every voxel in the brain. Networks of epileptogenic activity were visually identified and evaluated.Results: The results of the analysis show that the functional connectivity map with the epileptic focus as seed region can reveal associated networks. Figure 1a shows the seed region from fMRI data of one of the subjects. The associated connectivity map using this as seed region is shown in Figure 1b. It is clearly seen that the hippocampus and associated network are revealed in the connectivity map. Similar results were obtained in other subjects with different epileptic foci. Conclusions: This work shows that simultaneous fMRI-EEG along with functional connectivity analysis can reveal networks of epileptogenic activity in patients who are candidates for surgical intervention. This method can be a powerful tool in the decision making process for surgical intervention in epilepsy. References: 1. Jean Gotman et.al. Combining EEG and fMRI: A multimodal tool for epilepsy research. J Magnetic Resonance Imaging. 2006:23:906-920. 2. Frederique Liegeois, et.al. Role of fMRI in the decision-making process: Eplilepsy surgery for children. Acknowledgment: This work was supported by NIH grant NS047605