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Influence of the location and type of epileptogenic lesion on scalp interictal epileptiform discharges and high‐frequency oscillations
Author(s) -
CuelloOderiz Carolina,
Ellenrieder Nicolas,
Dubeau François,
Gotman Jean
Publication year - 2017
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/epi.13922
Subject(s) - ictal , scalp , electroencephalography , lesion , epilepsy , stereoelectroencephalography , temporal lobe , neuroscience , medicine , anatomy , pathology , psychology
Summary Objective To increase the diagnostic power of scalp electroencephalography ( EEG ) by investigating whether lesion type and location influence the morphology of interictal epileptic discharges ( IED s) and the likelihood that IED s and high‐frequency oscillations ( HFO s) are present. Methods We studied EEG activity in epilepsy patients with lesional epilepsy. Lesions were classified by type and by location (region and depth). We marked a maximum of 50 IED s during deep non–rapid eye movement sleep. IED s were identified as spikes or sharp waves with or without slow waves, or bursts of spikes or sharp waves with or without slow waves. We analyzed HFO s in the studies showing at least 50 IED s. Results In 192 scalp EEG studies, the differences in the percentage of studies showing IED s in each depth‐related group were not statistically significant, whereas HFO s (55 studies) predominated in patients exhibiting superficial lesions (p<0.001). Sharp waves, as predominant pattern, were more prevalent in hippocampal abnormalities (p < 0.001), whereas bursts predominated in patients with malformations of cortical development (p < 0.001). Significance The depth of the lesion does not influence the presence of IED s, as one might expect, but it influences that of HFO s. This is explained as follows. HFO s are generated in the epileptogenic region, do not propagate, and hence are only visible on scalp EEG with superficial lesions. IED s can result from a nearby focus or propagate from a deep generator and are therefore equally present with deep, intermediate, and superficial lesions. Additionally, IED morphology provides information in determining the lesion type.