Interictal HFO and FDG-PET correlation predicts surgical outcome following SEEG

Anatomical categorization of insulo-opercular focal cortical dysplasia and the spatial patterns of stereoelectroencephalography

OBJECTIVE

This study was undertaken to anatomically categorize insulo-opercular focal cortical dysplasia (FCD) lesions according to their location and extent, and to summarize corresponding stereoelectroencephalographic (SEEG) patterns to guide preoperative evaluation and surgical planning.

METHODS

Patients who underwent epilepsy surgery for insulo-opercular FCD between 2015 and 2022 were enrolled. FCD lesions were categorized into insular, peri-insular, opercular, and complex types based on their location and extent, as ascertained from electroclinical and neuroimaging data. SEEG signals from the seizure onset electrodes were collected for quantitative analysis. The normalized interictal spike counts, high-frequency oscillation (HFO) counts, and ictal epileptogenicity index (EI) values of the insular and opercular channels were calculated. The spatial patterns of the spike counts, HFO counts, and EI values were analyzed. Cluster analyses utilizing spike counts, HFO counts, and EI values were performed for automatic categorization, and the results were compared with the manual categorization from the preoperative evaluations.

RESULTS

A total of 53 patients were included, comprising 10 insular, 17 peri-insular, 24 opercular, and two complex cases. Thirty-eight patients were included in the quantitative SEEG analysis. Spike, HFO, and EI analyses indicated that in insular FCDs, the values of the three parameters were higher in insular channels than in opercular channels. In peri-insular FCDs, the values in insular and opercular channels were comparable, whereas in opercular FCDs, the values were higher in opercular channels than in insular channels. The accuracies of the cluster analysis based on the spike counts, HFO counts, and EI values were 71.05% (27/38), 76.32% (29/38), and 86.84% (33/38), respectively. Surgical strategies were proposed according to the anatomical categorization, achieving a favorable postoperative seizure-free rate of 84.91%.

SIGNIFICANCE

Insulo-opercular FCDs can be categorized into insular, peri-insular, opercular, and complex types. SEEG patterns can facilitate the automatic categorization of insulo-opercular FCDs, thereby enhancing preoperative planning and surgical outcomes.

SEEG seizure onset patterns in mesial temporal lobe epilepsy: A cohort study with 76 patients

OBJECTIVES

In the present study with a large cohort, we aimed to characterize intracerebral seizure onset patterns (SOP) of mesial temporal lobe epilepsy (mTLE), with or without hippocampal sclerosis (HS) as identified via magnetic resonance imaging (MRI).

METHODS

We retrospectively analyzed 255 seizures of 76 consecutive patients with mTLE explored by stereoelectroencephalography (SEEG), including HS-mTLE (n = 52) and non-HS- mTLE (n = 24). Relevant results were obtained by a combination of spectral analysis and manual review. High-frequency oscillations (HFO) were quantified across different SOP by an automatic detection method.

RESULTS

We identified six SOP according to previous work by Lagarde et al.: (1) Low-voltage fast activity (LVFA); (2) Rhythmic spikes followed by LVFA; (3) Burst of spikes followed by LVFA; (4) Periodic spikes or spike-wave followed by LVFA; (5) Rhythmic spike or spike-wave; (6) Theta or alpha sharp activity. Notably, Periodic spikes or spike-wave followed by LVFA had a high prevalence in all seizures (37 %). A significant association was established between Periodic spike followed by LVFA and HS-mTLE (P < 0.05). Furthermore, the counts of ripples and fast ripples were significantly higher in SOP displaying LVFA compared to those that did not (P < 0.05). Rhythmic spikes followed by LVFA had the best prognosis (92 % seizure-free), while Burst of spikes followed by LVFA were linked to poorest prognosis (67 % SF).

CONCLUSION

HS-mTLE and non-HS-mTLE exhibit distinct SOP characteristics, which can offer valuable prognostic insights with a more informative interpretation of ictal iEEG for clinical guidance.

Recent advances in clinical electroencephalography

PURPOSE OF REVIEW

Clinical electroencephalography (EEG) is a conservative medical field. This explains likely the significant gap between clinical practice and new research developments. This narrative review discusses possible causes of this discrepancy and how to circumvent them. More specifically, we summarize recent advances in three applications of clinical EEG: source imaging (ESI), high-frequency oscillations (HFOs) and EEG in critically ill patients.

RECENT FINDINGS

Recently published studies on ESI provide further evidence for the accuracy and clinical utility of this method in the multimodal presurgical evaluation of patients with drug-resistant focal epilepsy, and opened new possibilities for further improvement of the accuracy. HFOs have received much attention as a novel biomarker in epilepsy. However, recent studies questioned their clinical utility at the level of individual patients. We discuss the impediments, show up possible solutions and highlight the perspectives of future research in this field. EEG in the ICU has been one of the major driving forces in the development of clinical EEG. We review the achievements and the limitations in this field.

SUMMARY

This review will promote clinical implementation of recent advances in EEG, in the fields of ESI, HFOs and EEG in the intensive care.