Wide band frequency analysis reveals multiple focal cortical generators in patients with absence epilepsy
Abstract number :
1.128
Submission category :
3. Neurophysiology / 3D. MEG
Year :
2016
Submission ID :
194610
Source :
www.aesnet.org
Presentation date :
12/3/2016 12:00:00 AM
Published date :
Nov 21, 2016, 18:00 PM
Authors :
Sanjib Sinha, National Institute of Mental Health and Neurosciences (NIMHANS), India; Velmurugan Jayabal, NIMHANS, Bangalore, India; Mariyappa Narayanan, NIMHANS, Bangalore, India; Veeranna Gadad, NIMHANS; Parthasarathy Satishchandra, National Institute o
Rationale: Focal cortical generators in patients with absence epilepsy (AE) are less studied. We investigated the ictal discharges in AE with wide band frequency (1-200Hz) source localization, using magnetoencephalography (MEG). Methods: Nineteen patients (M: F=10:9; age: 10.253.39 years; duration of illness: 2.551.56 years), with drug-naive childhood (n=11) and juvenile (n=8) absence epilepsies underwent MEG-EEG recording (2 kHz sampling-rate). Preprocessed data was filtered (1-45Hz), for manual marking of sporadic or generalized spike-wave discharges (GSWD) lasting for >5 seconds(s) as 'ictal' spike wave discharges (ictal SWD). Subsequently, data was analyzed at 3 different bandwidths; 1-30Hz (conventional or C), 30-80Hz (gamma or G) and 80-200Hz (ripple or high frequency oscillation or R). For a single patient, 11 contiguous 50msec ictal spike segments with 50% overlap were concatenated and subjected to source localization over a cortical grid using adaptive spatial filtering method. Differences in the source localization between different frequency bands were evaluated using chi-square test. Results: A total of 119 (5.951.2) ictal MEG-EEG epochs were recorded in 19 patients which included 5135 (232.3749.82) independent ictal GSWD. Ictal GSWD localized to frontal (C/G/R=12/10/11), temporal (C/G/R=4/4/2), parietal (C/G/R=4/5/5), occipital (C/G/R=6/4/6) cortices and bi-lobar (C/G/R=4/5/3). There was no significant differences between source localization regions obtained at 3 frequency bands (p>0.05). The various localized cortical regions were pre-frontal & dorsolateral frontal, pre-cuneus, anterior cingulate, cuneus, paracentral lobule, superior-parietal, somatosensory and primary occipital cortices. Conclusions: The cortical regions identified using 3 different frequency bands suggested multiple focal/region generators, contrary to the 'generalized discharges in EEG/MEG'. The distributions of cortical generators were dominantly in the anterior hemisphere. These findings improve our understanding of the electrophysiology of focal abnormalities in IGE syndromes and might support the hypothetical concept of a focal pathological drive in a generalized network. Funding: nil
Neurophysiology