John Libbey Eurotext

Propagation of seizures in a case of lesional mid-cingulate gyrus epilepsy studied by stereo-EEG Volume 18, issue 4, December 2016

Figure 1

Summary of presurgical workup, intracranial stereo-EEG implantation, and statistical analysis of transformed EEG data during a seizure recorded by depth electrodes. (A) Summary of neuroimaging findings. Sagittal T1-weighted MRI showing the mid-cingulate and anterior cingulate abnormalities on the left side (red arrows), and the relationship of the mid-cingulate lesion to the VPC line (yellow), i.e. the vertical line through the posterior commissure. Encircled on the axial and sagittal FLAIR images are areas of increased signal intensity surrounding the lesion within the mid-cingulate gyrus (blue arrow), and the encephalomalacia within the orbitofrontal region (green arrow) respectively. The upper right-sided image depicts a colour-coded FDG-PET scan showing hypometabolism in the bilateral fronto-parietal regions, more pronounced on the left. The lower two axial images are the results of SISCOM analysis of the patient's ictal SPECT study which showed two discrete areas of hyperperfusion in proximity to the two MRI lesions, with the predominant focus originating from the mid-cingulate lesion. (B) Ten-second window of scalp EEG data at seizure onset viewed in anterior posterior bipolar montage. Notice the widespread electric decrements along with low-amplitude evolving alpha/theta rhythms. The patient had 2 stereotypical habitual events recorded during this scalp video-EEG evaluation. Clinically, the seizures consisted of brief hypermotor behaviour, while EEG rhythms were obscured by movement artefacts. (C) Stereo-EEG coverage of the left hemisphere. Individual axial and sagittal images show the location of electrode contacts that were implanted within the cingulate and orbitofrontal regions. (D) Statistically-transformed EEG data of Seizure 3 weighted by t-value compared to baseline. The horizontal axis represents time and the vertical axis individual electrode contacts. The corresponding sagittal MRI images show location of electrodes involved sequentially by the ictal discharge. The asterisks mark other anterior cingulate contacts, which are relatively uninvolved until late during the course of the seizure. The grey-scaled boxes at the bottom denote the clinical behaviour observed during the seizure, and the duration of each component corresponds to the width of the box.

FLAIR: fluid attenuated inversion recovery; FDG-PET: fluoro-deoxy-glucose positron emission tomography; SPECT: single photon emission computed tomography; SISCOM: subtracted ictal SPECT co-registered with MRI; NCS: no clinical signs (i.e. subclinical electrographic seizure); GTC: generalized tonic-clonic seizure.

Figure 2

Intracranial EEG tracing of seizures using LF 3-Hz, and HF 100-Hz filter settings and referential montage (reference in diploic space).(A) Zoom in on the contact of onset. (B) EEG background in all contacts at the time of onset marked in red, and by the red arrow pointing at contacts of onset X1, X2. The blue arrows mark contacts with earliest spread of paroxysmal fast activity outside the cingulate. Each vertical line marks a second.Notice the burst of non-evolving theta at onset in frontal contacts.

Figure 3

Statistical transformation in time-frequency space of EEG activity recorded by two electrode contacts weighted by t-value for significant changes compared to baseline. The upper plot is an example of an electrode contact recording an early non-evolving buzz of paroxysmal fast activity. The lower one depicts an electrode contact that does not record any paroxysmal fast changes early during the course of the seizure.