PMC6019859_01
Diagnostic evaluation for seizure localization.. (a) Interictal scalp EEG showing a left temporal spike. Scalp EEG during seizures (not shown) did not reveal a clear ictal pattern. (b) 3 Tesla brain MRI with axial (left) and coronal (right) T2 FLAIR sequences showing suspected FCD (arrowheads) extending from the left transverse temporal gyrus to the lateral ventricle (full extent of lesion not appreciable in single slices). (c) MEG showing spike dipoles (triangles with lines) clustering near the lesion. (d) Intracranial recording of seizure onset showing initial emergence of low-voltage fast activity in the lesional depth electrode channels with early involvement of the anterior STG, an area that was subsequently resected. Other seizures started in the lesional depth electrode but showed early spread to cortex of the angular gyrus and posterior STG (not shown). Vertical lines in (a) and (d) are spaced by 1 s.
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Interictal EEG findings included intermittent left temporal slowing and occasional left frontotemporal spikes (Fig. 1a). MRI revealed a linear T2-hyperintense lesion in the left temporal lobe extending from the superior temporal gyrus (STG) to the left lateral ventricle (Fig. 1b), suggestive of transmantle focal cortical dysplasia (FCD). Magnetoencephalography (MEG) revealed spikes clustered in the region of the lesion (Fig. 1c). Intracranial EEG recordings revealed seizure onset from the lesional depth electrodes, with rapid spread to the posterior STG and angular gyrus as well as an anatomically distinct focus in the anterior STG (Fig. 1d).
RNS System implantation and recordings.. (a) 3D reconstruction showing location of RNS System electrodes (red dots). Insular cortex is colored in blue for reference. (b) Coronal T1 brain MRI co-registered with post-operative head CT to show location of RNS depth lead in the region of the presumed FCD (compare Fig. 1b). (c) RNS System ECoG capturing a seizure before responsive stimulation was enabled. (d) RNS System ECoG showing putative seizure termination by responsive stimulation. As in (c), low-voltage fast activity arises from the lesional depth electrode channels but, following delivery of responsive therapy (vertical blue line), an ictal pattern does not develop.
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Post-operative head computed tomography (CT) scan co-registered with pre-operative brain MRI confirmed expected RNS System electrode locations (Fig. 2a, b). Electrocorticograms (ECoGs) stored by the RNS System revealed several electrographic seizures (Fig. 2c) which correlated well with the patient's clinical seizure diary. By the second post-operative follow-up appointment two months later, several instances of putative seizure termination by responsive stimulation were evident on stored ECoGs (Fig. 2d).