MAGNETOENCEPHALOPRAPHIC (MEG) INVESTIGATION OF PARADOXICAL LATERALIZATION IN PARIETO-OCCIPITAL INTERICTAL SPIKES
Abstract number :
1.160
Submission category :
Year :
2004
Submission ID :
2040
Source :
www.aesnet.org
Presentation date :
12/2/2004 12:00:00 AM
Published date :
Dec 1, 2004, 06:00 AM
Authors :
1Katsumi Imai, 2Keiko Yanagihara, 3Toshiyuki Mano, 4Toshiki Yoshimine, and 1Keiichi Ozono
Pattern reversal hemi-field visual evoked potential (P-VEP) and posterior tibial nerve somatosensory evoked potential (PT-SEP) show higher amplitudes ipsilateral to the side of stimulation, which is known as paradoxical laterazation. Magnetoencephalogram (MEG) are reported to reveal the correct localization of dipoles showing the paradoxical laterazation, but there are a few reports concerning paradoxical lateralization of epileptic interictal spikes.
To reveal neurophysiological characteristics, we analysed parieto-occipital spikes by EEG and MEG because those are less concerned in transcallosal bilateralization than frontal spikes. We analysed EEG and MEG of 13 epileptic patients (2-19y, 7 symptomatic, 6 cryptogenic) with parieto-occipital spikes. MEG was recorded with whole-head 64 channel gradiometer system (CTF, Canada). Localization of spikes was estimated by single dipole model and superimposed on MRI images. EEG was recorded with international 10-20 scalp electrodes simultaneously with MEG.
Spike lateralization was considered [quot]concordant[quot] (CL) or [quot]paradoxical[quot] (PL) whether MEG estimated dipoles and maximum negative EEG spikes were located on the same side or the opposite side. 1) Ten cases were considered to show CL, and 3 cases PL.
2) In the cases with CL, MEG dipoles were estimated on the base or lateral surface of occipital lobe. The direction of dipoles were not constant but vertical in many cases.
3) In the cases with PL, MEG dipoles were located on the mesial surface of parieto-occipital lobe. The direction of dipoles were horizontal antero-lateral oblique.
4) Positive EEG spikes were observed on the opposite side of the negative EEG spikes in all of PL cases and some of CL cases in whom MEG dipoles were located on the mesial surface. 1) Interictal parieto-occipital spikes can show paradoxical lateralization only when the dipole is located on the mesial surface with horizontal antero-lateral oblique direction.
2) Above mentioned characteristics of paradoxical lateralization were common with P-VEP or PT-SEP which were also reported to show paradoxical lateralization.
3) Magnetoencephalographic (MEG) investigation was very useful in analyzing paradoxical lateralization of interictal spikes.