Epileptic high-frequency network activity in a model of non-lesional temporal lobe epilepsy.
High-frequency cortical activity, particularly in the 250-600 Hz (fast ripple) band, has been implicated in playing a crucial role in epileptogenesis and seizure generation. Fast ripples are highly specific for the seizure initiation zone. However, evidence for the association of fast ripples with epileptic foci depends on animal models and human cases with substantial lesions in the form of hippocampal sclerosis, which suggests that neuronal loss may be required for fast ripples. In the present work, we tested whether cell loss is a necessary prerequisite for the generation of fast ripples, using a non-lesional model of temporal lobe epilepsy that lacks hippocampal sclerosis. The model is induced by unilateral intrahippocampal injection of tetanus toxin. Recordings from the hippocampi of freely-moving epileptic rats revealed high-frequency activity (>100 Hz), including fast ripples. High-frequency activity was present both during interictal discharges and seizure onset. Interictal fast ripples proved a significantly more reliable marker of the primary epileptogenic zone than the presence of either interictal discharges or ripples (100-250 Hz). These results suggest that fast ripple activity should be considered for its potential value in the pre-surgical workup of non-lesional temporal lobe epilepsy.
Jiruska
Premysl
P
Neuronal Networks Group, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK.
Finnerty
Gerald T
GT
Powell
Andrew D
AD
Lofti
Noosheen
N
Cmejla
Roman
R
Jefferys
John G R
JG
D000818:Animals; D002540:Cerebral Cortex / Q000503:physiopathology; D004594:Electrophysiology; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D006624:Hippocampus / Q000473:pathology / Q000503:physiopathology; D008297:Male; D009415:Nerve Net / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013744:Tetanus Toxin
D013744:Tetanus Toxin
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