PMC10131120_01
A) Coronal skull base CT and T2 MRI brain showing a left anterior inferior temporal lobe encephalocele and a left choroidal fissure cyst respectively. B) T1 MRI brain oblique view showing sEEG electrode (LL) with distal contacts in the encephalocele and coronal FLAIR MRI showing sEEG electrode sampling the region around the left temporal choroidal cyst C) Post surgical CT head showing pneumocephalus and extent of resection limited to the encephalocele and surrounding cortex sparing the mesial temporal structures.
gr1.jpg
PMC10131120_01_gr1.jpg
f0005
Imaging with skull-based CT and MRI brain showed a left anterior inferior temporal lobe encephalocele and a left choroidal fissure cyst that were stable on repeat imaging (Fig. 1A). A single electrode (LL) that would directly sample the encephalocele was planned (Fig. 1B). Based on the results of the sEEG, a limited encephalocele resection was planned (Fig. 1C).
A) Example of a recorded seizure during sEEG monitoring showing sample recording with 3 leads LA (entry middle temporal gyrus, target left amygdala), LC (entry middle temporal gyrus, target left hippocampal body) and LL (entry superior temporal gyrus, target encephalocele). Onset of ictal activity with low amplitude 32 Hz activity is seen over LL1-4 (contacts in the encephalocele). Activity in LA 11-12(left middle temporal) and LC 7-10(left middle temporal) was noted interictally. Slower less organized activity was present early in LL 9-13 which evolved later than LL 1-4 into organized rhythmic discharges. Sensitivity 50 uV/mm, timebase 5 mm/sec B), C) front and left view of 3D rendering of coregistered sEEG electrodes and MRI/post-op CT imaging using Curry 8.0 software (Neuroscan Compumedics, Charlotte, NC) where contacts corresponding to seizure onset are in red and showing earliest spread to the cingulate and insula in orange. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
gr2.jpg
PMC10131120_01_gr2.jpg
f0010
Stereo-EEG (sEEG) targeting primarily the left limbic region was planned to better localize the seizure onset zone in this dominant temporal lobe epilepsy given the presence of both the encephalocele and choroidal fissure cyst (Fig. 2A). One typical focal to bilateral tonic-clonic seizure and two focal seizures with impaired awareness were captured with onset in the left temporal pole encephalocele contacts (LL 1-4) with subsequent earliest spread to the cingulate, insula, left superior temporal gyrus (LL 11-12) and early spread to left mesial temporal electrodes. (Fig. 2A, 2B, 2C). LA 11-12(left middle temporal) and LC 7-10(left middle temporal) bursts of spikes seen in Fig. 2 were present interictally and did not represent the ictal onset contact. Slower less organized activity was present early in LL 9-13(Fig. 2) which evolved later than LL 1-4 into organized rhythmic discharges indicating that these contacts were not involved in seizure onset and likely represent activation due to volume conduction.