Clinical Utility of Interictal High-Frequency Oscillations Recorded with Subdural Macroelectrodes in Partial Epilepsy

BACKGROUND AND PURPOSE: There is growing interest in high-frequency oscillations (HFO) as electrophysiological biomarkers of the epileptic brain. We evaluated the clinical utility of interictal HFO events, especially their occurrence rates, by comparing the spatial distribution with a clinically determined epileptogenic zone by using subdural macroelectrodes. METHODS: We obtained intracranial electroencephalogram data with a high temporal resolution (2000 Hz sampling rate, 0.05-500 Hz band-pass filter) from seven patients with medically refractory epilepsy. Three epochs of 5-minute, artifact-free data were selected randomly from the interictal period. HFO candidates were first detected by an automated algorithm and subsequently screened to discard false detections. Validated events were further categorized as fast ripple (FR) and ripple (R) according to their spectral profiles. The occurrence rate of HFOs was calculated for each electrode contact. An HFO events distribution map (EDM) was constructed for each patient to allow visualization of the spatial distribution of their HFO events. RESULTS: The subdural macroelectrodes were capable of detecting both R and FR events from the epileptic neocortex. The occurrence rate of HFO events, both FR and R, was significantly higher in the seizure onset zone (SOZ) than in other brain regions. Patient-specific HFO EDMs can facilitate the identification of the location of HFO-generating tissue, and comparison with findings from ictal recordings can provide additional useful information regarding the epileptogenic zone. CONCLUSIONS: The distribution of interictal HFOs was reasonably consistent with the SOZ. The detection of HFO events and construction of spatial distribution maps appears to be useful for the presurgical mapping of the epileptogenic zone.

Differentiation of Temporal Lobe Epilepsy by Scalp Ictal EEG and Its Correlation with Surgical Outcome / 대한간질학회지

PURPOSE: Ebersole and Pacia recently introduced a classification of scalp ictal EEG in temporal lobe epilepsy (TLE). So we investigated whether scalp ictal EEG without sphenoidal electrode can differentiate mesial TLE from neocortical TLE and can be predictive of surgical outcome after temporal lobectomy. METHODS: A consecutive 77 patients (male 43, female 34) with TLE were included who had temporal lobectomy after the comprehensive presurgical evaluation. The patients with mesial TLE were 59 and those with neocortical TLE 18. The total 358 seizures were analyzed using bipolar and monopolar montage without sphenoidal electrodes. Scalp ictal EEGs were categorized into 3 types based on Ebersole and Pacia's classification and then were evaluated with regard to the differentiation of TLE and its correlation with surgical outcome. RESULTS: 1) Out of the total 77 patients, type 1 pattern was observed in 23 (30%), type 2 in 51 (65%), and type 3 in 3 (5%). The number of patients with mesial TLE were 17 (74%) out of 23 with type 1, 41 (80%) out of 51 with type 2, 1 out of 3 with type 3. Type 1 pattern was relatively specific (74%) but not sensitive (30%) for mesial TLE. Also the lesion location of neocortical TLE with type 1 onset was not limited to medial temporal area. 2) Scalp ictal EEG patterns were significantly correlated with surgical outcome only in the subgroup of mesial TLE (p=0.006) but not in neocortical TLE. Type 1 onset pattern in mesial TLE was associated with favorable outcome comparing to type 2 onset. CONCLUSIONS: Scalp ictal EEG onset pattern cannot accurately differentiate mesial TLE from neocortical TLE. However, its onset pattern can be predictive of surgical outcome.

Cortical Dysplasia and Mesial Temporal Sclerosis in Temporal Lobe Epilepsy Pre-operative Clinical Feature and Surgical Outcome between Patients with Dual Pathology and Patients with Mesial Temporal Sclerosis

BACKGROUND: Mesial temporal sclerosis (MTS) is a well-known cause of temporal lobe epilepsy. Coexistence with cortical dysplasia (CD) has been reported, but its role is not well recognized. This study aims to determine whether there is any difference about clinical feature and surgical outcome between patients with MTS and coexistent CD (group 1) and patients with isolated MTS (group 2). METHODS: Retrospectively, surgical series of 45 patients (male:22, female:23) diagnosed as temporal lobe epilepsy were reviewed. We excluded patients who had another pathology (e. g., tumor, vascular malformation) except MTS or CD. The pathology, case histories, interictal EEG, and surgical outcome were compared. RESULTS: There was a tendency for group 1 patients to have earlier seizure onset age (10.9+/-6.35 versus 14.5+/-6.03, p=0.06) There was no statistically significant difference in the history of febrile convulsions (68.4% versus 53.8%, p>0.16) No statistically significant difference between groups were also found in disease duration, the head trauma/mental retardation history, seizure frequency, interictal EEG, and surgical outcome. CONCLUSIONS: CD in MTS appears to have an influence on seizure onset. The relationships among CD, febrile convulsion, and mesial temporal sclerosis must be more investigated.

Cortical Dysplasia and Mesial Temporal Sclerosis in Temporal Lobe Epilepsy Pre-operative Clinical Feature and Surgical Outcome between Patients with Dual Pathology and Patients with Mesial Temporal Sclerosis

BACKGROUND: Mesial temporal sclerosis (MTS) is a well-known cause of temporal lobe epilepsy. Coexistence with cortical dysplasia (CD) has been reported, but its role is not well recognized. This study aims to determine whether there is any difference about clinical feature and surgical outcome between patients with MTS and coexistent CD (group 1) and patients with isolated MTS (group 2). METHODS: Retrospectively, surgical series of 45 patients (male:22, female:23) diagnosed as temporal lobe epilepsy were reviewed. We excluded patients who had another pathology (e. g., tumor, vascular malformation) except MTS or CD. The pathology, case histories, interictal EEG, and surgical outcome were compared. RESULTS: There was a tendency for group 1 patients to have earlier seizure onset age (10.9+/-6.35 versus 14.5+/-6.03, p=0.06) There was no statistically significant difference in the history of febrile convulsions (68.4% versus 53.8%, p>0.16) No statistically significant difference between groups were also found in disease duration, the head trauma/mental retardation history, seizure frequency, interictal EEG, and surgical outcome. CONCLUSIONS: CD in MTS appears to have an influence on seizure onset. The relationships among CD, febrile convulsion, and mesial temporal sclerosis must be more investigated.