Abstracts

Activations and deactivations are frequently observed in response to interictal spikes during co-registered EEG-fMRI studies. In focal lesional epilepsy, activations have been more frequently observed in relation to the lesion and perilesional areas, whereas deactivations tend to occur at distant brain areas. This pattern may be correlated with increased neuronal activity and hyperexcitability in the focus and neuronal inhibition at a distance. Results assume normal neurovascular coupling and we therefore compared patients with probable vascular abnormalities to patients with unlikely vascular abnormalities., We evaluated 10 patients who had atrophic-gliotic brain lesions (8 with associated encephalomalacia) resulting from either a perinatal vascular insult or a traumatic brain injury. All patients underwent a 2-hours EEG-fMRI session in a 1.5Tesla scanner, and each spike type determined one EEG-fMRI study. Pattern and distribution of the BOLD responses in relation to the lesions were analyzed and compared to those found in patients with malformations of cortical development (MCDs)., Fifteen EEG-fMRI studies were analyzed. Activations were observed in 12 studies (80%): 4of 12 (33%) involved the lesional or perilesional areas and all showed also activations at a distance. Deactivations were found in 12 (80%) studies and in 9 of 12 (75%), at the borders of the cystic lesion or within the atrophic tissue, and hence related to the lesional and perilesional areas. Distant deactivation was found in 11 studies (91.5%).
These results were distinct from those found in 40 EEG-fMRI studies derived from 28 patients with different types of MCDs. Activations were seen in 31 studies (77.5%) and in 22 of them (71%) these responses involved the lesional or perilesional areas, with concomitant distant activation in 25 (81%). Deactivations were seen in 28 studies (70%), and in 11 of them (39%) with an involvement of the lesional or perilesional areas. Deactivation at distance was seen 25 (89%) studies.
Lesional/perilesional activations were more frequent than deactivations in patients with MCDs (Pearson[apos]s Chi-square [df=1], p=0.024) whereas lesional/perilesional deactivations were more frequent in patients with atrophic-gliotic lesions (Pearson[apos]s Chi-square [df=1], p=0.038)., Patients with atrophic-gliotic lesions have associated vascular abnormalities that may affect the BOLD responses during EEG-fMRI studies. The finding of a lower rate of activations and of a higher rate of deactivations in the lesional and perilesional areas during interictal spikes supports an abnormal, or different, neurovascular coupling in this type of brain lesions. The vascular environment of the epileptogenic lesions should be considered when evaluating metabolic responses to epileptic discharges., (Supported by Canadian Institutes of Health Research.)