International Journal of Epilepsy 2016; 03(01): 42-62
DOI: 10.1016/j.ijep.2015.12.029
Thieme Medical and Scientific Publishers Private Ltd. 2017

Resting-state fMRI abnormalities in temporal lobe epilepsy

John Stern
1   Professor, Dept of Neurology, UCLA, Los Angeles, USA
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12. Mai 2018 (online)

The differentiation of epilepsies into focal and generalized has been undergoing reconsideration, as is evident in the 2010 ILAE definitions. Focal is no longer defined as limited to one region of cerebral tissue and is now defined as network(s) limited to one hemisphere. Moreover, generalized is no longer defined as distributed across the whole head and is now defined as bilaterally distributed networks that do not encompass the whole cortex. The evidence for value in this re-conceptualization of epilepsy as a distributed or network abnormality includes the potential to treat at sites other than the ictal onset zone, as the anterior nucleus of the thalamus stimulation trial demonstrated. Better understanding of the network abnormality is arising from resting-state imaging studies. Resting-state imaging is the identification of regions of brain activity are not elicited by functional tasks. These regions were first identified through analyses of the rest-state across a variety of task-related imaging studies, such as language and motor mapping. Although an actual rest-state actually does not exist for the brain, resting-state imaging provides insights into the background functional connectivity across regions, as can be identified with several analysis approaches, including region-of-interest (seed) based connectivity, independent component analyses, and graph theory metrics. Connectivity has now been identified as abnormal in several brain disorders. For temporal lobe epilepsy, resting-state imaging has identified differences between left and right temporal lobe epilepsy and abnormalities of increased connectivity to some regions and decreased connectivity to others. Each finding clarifies the underlying abnormality of epilepsy.