Usefulness and Limitations of Preoperative Evaluation by High-density Electroencephalography (HD-EEG) for Temporal Lobe Epilepsy
Abstract number :
2.314
Submission category :
9. Surgery / 9A. Adult
Year :
2023
Submission ID :
924
Source :
www.aesnet.org
Presentation date :
12/3/2023 12:00:00 AM
Published date :
Authors :
Presenting Author: Masami Fujii, MD, PhD – Yamaguchi Prefectural Grand Medical Center
Toshikazu Nagatsuna, MD, PhD – Neurosurgery – Yamaguchi Prefectural Grand Medical Center; Suguru Nagamitsu, MD – Neurosurgery – Yamaguchi Prefectural Grand Medical Center; Natsue Kaneko, MD – Neurosurgery – Yamaguchi Prefectural Grand Medical Center; Hiroaki Yasuda, MD, PhD – Neurosurgery – Yamaguchi Prefectural Grand Medical Center; Manabu Urakawa, MD, PhD – Neurosurgery – Yamaguchi Prefectural Grand Medical Center; Tetsuo Yamashita, MD, PhD – Neurosurgery – Yamaguchi Prefectural Grand Medical Center; Hironori Sasaki, Mr – Clinical Laboratory – Yamaguchi Prefectural Grand Medical Center; Masaki Iwane, Mr – Clinical Laboratory – Yamaguchi Prefectural Grand Medical Center; Toshihiro Fukusako, MD – Neurology – Yamaguchi Prefectural Grand Medical Center
Rationale:
Accurate detection of the epileptogenic zone is an important factor in obtaining a good surgical outcome in pharmaco-resistant patients with focal epilepsy. Electrical source imaging by high-density electroencephalography (HD-EEG) is a non-invasive, low-cost and accurate presurgical workup for localizing the epileptic zone. Here, we report the usefulness and limitations of HD-EEG as a preoperative examination for temporal lobe epilepsy.
Methods:
Seven patients (four males and three females) aged 21 to 65 years (mean 38 years) were included in the study. Interictal EEG showed focal spikes or sharp waves in frontotemporal or temporal regions, and the semiology of seizures was focal impaired awareness seizure (FIAS) in all cases. Anterior temporal lobectomy (ATL) was performed in six patients and removal of angioma with surrounding cortices in one. Postoperative outcomes were seizure-free in six patients and Engel’s class 2 in one patient. HD-EEG recording was conducted with the Geodesic Sensor Net using 256-channel electrodes covering the entire head, including the cheek and neck area, with inter-electrode distances of 20-25 mm. The HD-EEG was recorded for 30-40 minutes in a resting position with the eyes closed. Subsequently, interictal epileptogenic discharges (IEDs) were identified and reviewed by an EEG expert, and grouped according to similar patterns of spatial distribution. The classified IEDs were segmented (500 ms before and 500 ms after the spike peak) and averaged. The source obtained from the averaged IED was superimposed on an individual magnetic resonance image (MRI) using low-resolution electromagnetic tomography (LORETA).
Results:
The signal source was detected with HD-EEG in six of seven patients. In one case, spikes were attenuated by thick hair and the signal source could not be identified accurately. Spikes could be detected on the cheek and posterior neck, in addition to the scalp, on HD-EEG. Signal sources were detected at the bottom of the temporal lobe or anterior temporal lobe in five patients who were seizure-free after surgery. In the patient with residual seizures, spikes were classified into two groups and distributed at the bottom of the anterior and posterior temporal lobes. When a single signal source is detected at the bottom of the temporal lobe or anterior temporal lobe on HD-EEG, ATL could be performed without intracranial EEG recording. However, it is difficult to distinguish whether the epileptic focus exists in the hippocampus or in the bottom areas of the temporal lobe (uncus, amygdala, or inferior temporal, fusiform and parahippocampal gyri) by the HD-EEG recording.
Conclusions:
A single distribution of spikes in the anterior and bottom of the temporal lobe detected by HD-EEG source imaging indicates a good seizure outcome after anterior temporal lobectomy.
Funding: No
Surgery