COMPARISON OF EEG-FMRI DATA TO INVASIVE ELECTROPHYSIOLOGICAL REGISTRATION IN CRYPTOGENIC FOCAL EPILEPSY

Purpose: To compare different methodological approaches in a patient with cryptogenic epilepsy who underwent invasive neurophysiologic investigation. Method: A 15 year old boy with drug-resistant cryptogenic epilepsy underwent continuous EEG- fMRI acquisition using a 3T MR scanner. During the examination 26 interictal electric abnormalities were regis- tered. The fMRI data analysis was performed by different event-related (ER) design adopting respectively canonical hemodynamic response function (HRF), Fourier and Finite Impulse Response (FIR) basis func- tions. The localization of activation/deactivation clusters obtained by each statistical approach was compared with the localization of the‘‘sei- zure onset zone’’ obtained by invasive stereo-EEG. Result: Similar activation maps were obtained by ER design using FIR basis functions and Fourier basis functions as HRF. Both approaches pro- vided clusters of activation concordant with the‘‘seizure-onset’’ zone identified by depth electrodes. On the other hand, ER design combined with standard HRF was not able to identify clusters within the‘‘seizure- onset’’ zone. Conclusion: The ER approach using Fourier and FIR basis functions might provide adjunctive information with respect to standard HRF. The role of non-canonical approaches in identifying the epileptogenic zone needs to be evaluated on large series of patients.