PMC9483572_01
Pre- and post-surgical brain MRI and post-processing analysis. Presurgical MRI: a) T2-weighted transverse turbo spin-echo (TSE) and b) T2-weighted transverse TSE fluid-attenuated inversion-recovery (FLAIR) axial sequences. c) and d) T2-weighted transverse TSE fluid-attenuated inversion-recovery (FLAIR) coronal sequences. Arrows indicate the presumed lesion. Post-surgical MRI: e) T2-weighted transverse TSE FLAIR axial sequences. f) MAP post-processing analysis.
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In the right hemisphere, particularly in the right frontal regions, no lesions were observed (Fig. 1). The post-processing analysis supported this hypothesis (Fig. 1).
3D schema of stereo-EEG electrode implantation demonstrating the left (a) and right (b) implantations.
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We extensively explored the central, precentral, and insulo-opercular regions with electrodes in the first temporal gyrus to explore the inferior part of the insula and to check for secondary propagation to temporal regions (Fig. 2).
Ictal stereo-EEG findings. The figure illustrates the ictal discharge during stereo-EEG. Left-sided electrodes are shown in black, right-sided ones are shown in blue. The seizure started in electrode J (mesial and lateral), one second later the mesial leads of electrode F are involved (red arrows, panel a and b). Notice the fast involvement of the right motor cortex and contralateral homologous regions. At the end of the seizure, electrical depression was evident in the right premotor and motor areas (panel c and d). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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We recorded only one spontaneous seizure clinically as described above, clearly arising from the right precentral region with fast propagation to the homolateral primary motor cortex and with important but late contralateral hemispheric field of spread (Fig. 3).
Intracerebral electrical stimulations. In panels a)-d), the high frequency stimulation of F6-7 at 1 mA inducing a seizure similar to the spontaneous one. In the panels e) and f), the high frequency stimulation of L'6-7 at 0.8 mA provoked just the motor manifestations in the contralateral side. Left-sided electrodes are shown in black, right-sided electrodes are shown in blue. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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Interestingly, we induced a spontaneous seizure by stimulating electrode contact F6-7 with 1 mA at 50 Hz (Fig. 4). At 50 Hz stimulation of the contralateral homologous contacts L'6-7 with 0.8 mA of current induced motor clonic manifestations in the right hemibody, associated with a post-discharge involving only the left electrodes (Fig. 4).