Authors :
Presenting Author: Satoshi Maesawa, MD, PhD – Nagoya University
Tomotaka Ishizaki, MD, PhD – Department of Neurosurgery, Nagoya University Graduate School of Medicine; Takafumi Tanei, MD, PhD – Department of Neurosurgery, Nagoya University Graduate School of Medicine; Manabu Mutoh, MD – Department of Neurosurgery, Nagoya University Graduate School of Medicine; Yoshiki Ito, MD – Department of Neurosurgery, Nagoya University Graduate School of Medicine; Miki Hashida, MD – Department of Neurosurgery, Nagoya University Graduate School of Medicine; Koichi Fujiwara, PhD – Nagoya University Graduate School of Engeneering; Ryuta Saito, MD, PhD – Department of Neurosurgery, Nagoya University Graduate School of Medicine
Rationale:
Stereotactic electroencephalography (SEEG) is attracting increasing attention as a safe and effective technique in the invasive evaluation for epileptogenic zone (EZ) detection. Several international reports from large epilepsy centers found the following clinical advantages of SEEG: 1) three-dimensional analysis of structures, including bilateral and multilobar structures; 2) low rate of complications; and 3) a higher rate of good seizure control after resection. The main clinical question is whether the use of SEEG truly improves outcomes. Herein, we compared outcomes in our patients after three types of intracranial EEG (iEEG): SEEG, the subdural electrode (SDE), and a method combining depth and strip electrodes (SEEG+SDE).
Methods:
Forty-two consecutive patients (26.4 ± 13.1 years old) performed iEEG recordings at our hospital (Nagoya University Hospital, Japan) since 2017. SEEG was performed using a robot arm (Neuromate) with 9.5±1.8 depth electrodes. In the combined method, 6.8±1.7 depth electrodes with 3.0±0.4 strip electrodes were used. In the SDE method, grid electrodes with 67.5±16.6 contacts were used. We reviewed following factors: electrode placement methods, MRI findings, location of presumed EZs, presumed epileptic networks (A: confined to a single brain lobe, B: early propagation to adjacent lobes or C: contralateral propagation), complications, types of subsequent surgery, and postoperative seizure suppression (the Engel class). Logistic regression analysis was used to examine factors influencing subsequent surgery and good seizure prognosis.
Results:
The electrode placement methods were categorized into SEEG (25 cases), SEEG+SDE (13 cases), and SDE (4 cases). No MRI lesion was found in 59.5% of the cases, and most of the presumed EZs were in the temporal lobe (45.2%) and frontal lobe (35.7%). The network was classified as type A in 33.3%, type B in 38.1%, and type C in 28.6%. Intracerebral hemorrhages observed in two cases (SEEG=1, SEEG+SDE=1). Subsequent surgery was performed in 78.5% of the cases, of which two cases were radiofrequency thermocoagulation (RFTC). The rate of patients without subsequent surgery was high in the SEEG group (28%), but it was not significant. Engel class 1 was achieved in 51.5% of the cases, particularly the SEEG group showed the highest rate (66.7%). After RFTC, one patient was achieved in class 1, and the other was class 2. Logistic regression analysis revealed that the type of the epileptic network (type A preferred) and the implantation method (SEEG preferred) were significant factors on seizure prognosis (P=0.001). Other factors such as locations of the EZ or MRI-visible lesions were not significant.
Conclusions:
Early propagation to adjacent lobes or contralateral sides may lead to unfavorite prognosis, and careful consideration of indications for subsequent surgery is required. In this sense, SEEG is helpful, and three-dimensional understanding the EZ including bilateral and multilobar structures, improves subsequent surgical outcomes.
Funding: This research was supported by AMED under Grant Number JP21uk1024005.