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Epileptic Disorders

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Electroclinical features of lateral and medial orbitofrontal epilepsy: a case series Volume 22, issue 6, December 2020

Figure 1

SEEG recordings of Patient 1. (A) Three-dimensional MRI reconstruction of the depth electrodes. The electrodes explored the medial and lateral part of the right frontal lobe. The middle part of electrode A (latOrG) and internal contact of electrode E (from MFG to latOrG) captured the seizure onset. (B) The actual placement of electrodes A and E shown on a 3D MRI image. (C) Seizures started with low-voltage fast activities in the latOrG (vertical bar indicates seizure onset), then propagated to SFS and IFG. SEEG power in the time-frequency plane (below): SOZ is characterized by early rapid discharges and high-frequency energy in latOrG, followed by SFS and IFG. (D) The high-frequency signal was superimposed on the 3D reconstruction image, showing early involvement of the latOrG and transfer of high-frequency energy from the latOrG (0 s) to the lateral part of the frontal lobe (2-3 s), then energy increased when symptoms appeared (5–6 s). (E) The patient had no symptoms at the beginning of the seizure; when propagating to the lateral part of the frontal lobe, the patient woke up with pelvic thrusting, pedaling or raising of the legs. (F) Epileptogenicity index values are shown as a colour scale overlying the MRI; the highest epileptogenicity index value was confined to latOrG. (G) Illustration showing sites of thermocoagulation in the latOrG (in red circle); the patient had a simple partial seizure after 14 months.

LatOrG: lateral orbital gyrus; OFG: orbitofrontal gyri; SFS: superior frontal sulcus; IFG: inferior frontal gyrus; SOZ: seizure onset zone.

Figure 2

SEEG recordings of Patient 2. (A) Three-dimensional MRI reconstruction of the depth electrodes. The electrodes explored the medial and lateral part of the bilateral frontal lobe, mainly on the right. Electrodes G (from MFG to LatOrG) and H (from MFG to LatOrG, almost parallel to G and more inside) captured the seizure onset. (B) The actual placement of electrodes G and H shown on the 3D MRI image. (C) Seizures started with low-voltage fast activities in the latOrG, then propagated to the MFG and trIFG. SEEG power in the time-frequency plane: SOZ with early rapid discharges and high-frequency energy in latOrG, followed by opIFG, MFG, and trIFG. There was no high-frequency response in the temporal lobe. (D) The high-frequency signal on the 3D reconstruction image showing early involvement of the latOrG (0 s), followed by the activation of the lateral part of the frontal lobe (12 s). (E) The patient had no symptoms at the beginning of the seizure; when propagating to the lateral part of the frontal lobe, he presented with the same symptoms as Patient 1. (F) Based on epileptogenicity index analysis, the seizure onset of the patient was confined to latOrG. (G) Illustration showing sites of thermocoagulation in the latOrG. The patient was seizure-free for 12 months, then seizures recurred; he had right orbitofrontal lobe resection after which no seizures occurred.

opIFG: pars opercularis; MFG: middle frontal gyrus; trIFG: pars triangularis.

Figure 3

SEEG recordings of Patient 3. (A) The electrodes mainly explored the medial and lateral part of the left frontal lobe. Electrodes A (from SFG to anterior RG) and B (from SFG to posterior RG) captured the seizure onset. (B) The actual placement of electrodes A and B shown on a 3D MRI image. (C) Seizures started with low-voltage fast activities in the RG (internal leads of electrodes A and B), then propagated to AM and Hi, and the patient showed oro-alimentary automatism. There was no high-frequency response in the lateral part of the frontal lobe (MFG). (D) The high-frequency signal on the 3D reconstruction image showing early involvement of the RG (0 s), followed by the activation of the mesial temporal lobe (20 s). (E) Based on epileptogenicity index analysis, the seizure onset of the patient was confined to RG. (F, G) The patient underwent two surgical resections. Part of the RG was missed in the first resection (in red circle), and he still had seizures; the missed part was then removed, and he was seizure-free after 10 months of follow-up.

RG: rectus gyrus; postOrG: posterior orbital gyrus; InsP: insular pole; AM: amygdala nuclei; SFG: superior frontal gyrus.

Figure 4

SEEG recordings of Patient 4. (A) The electrodes explored the bilateral medial and lateral part of the frontal and temporal lobe. Electrodes A’ (from SFG to posterior RG) and B’ (from SFG to anterior RG) captured the seizure onset. (B) The actual placement of electrodes A’ and B’ (internal contact of electrode) is shown on the MRI image. (C) Seizures started with low-voltage fast activities in the RG (internal leads of electrodes A’ and B’) then propagated to the insular pole and temporal pole and hippocampus; the patient showed symptoms of oro-alimentary and hand automatism when these areas were involved. (D) The high-frequency signal on the 3D reconstruction image showing early involvement of the RG (0 s), followed by the activation of the insular pole, temporal pole (60 s), and mesial temporal lobe (70-80 s). (E) Based on epileptogenicity index analysis, the seizure onset of the patient was confined to RG. (F) RF-TC was performed in the left rectus gyrus, and the patient became seizure-free after 14 months of follow-up; sites of thermocoagulation in the RG are depicted on the MRI image.

SFG: superior frontal gyrus; RG: rectus gyrus; InsP: insular pole; TP: temporal pole; Hi: hippocampus; HH: head of hippocampus.