Technical Aspects of SEEG and Its Interpretation in the Delineation of the Epileptogenic Zone

Khoo, Hui Ming; Hall, Jeffery A.; Dubeau, François; Tani, Naoki; Oshino, Satoru; Fujita, Yuya; Gotman, Jean; Kishima, Haruhiko

doi:10.2176/nmc.st.2020-0176

Cited by 24 publications

(16 citation statements)

References 59 publications

(91 reference statements)

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“…6,7 Stereo-EEG (SEEG) is a minimally invasive intracranial monitoring method used to localize seizure onset for surgery. 8,9 During SEEG, ASMs are typically weaned in the epilepsy monitoring unit (EMU) to elicit seizures to localize EZs.…”

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confidence: 99%

SEEG Functional Connectivity Measures to Identify Epileptogenic Zones

et al. 2022

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Background and Objective:Functional connectivity (FC) measures can be used to differentiate epileptogenic zones (EZs) from non-EZs in patients with medically refractory epilepsy. However, little work has been done to evaluate stability of stereoelectroencephalography (SEEG) FC measures over time and their relationship with anti-seizure medication (ASM) use – a critical confounder in epilepsy FC studies to date. In this study, we aim to answer the following questions: 1) are SEEG FC measures stable over time, 2) are they influenced by ASMs, and 3) are they impacted by patient data collection state?Methods:In 32 patients with medically-refractory focal epilepsy, we collected a single two-minute prospective SEEG resting-state (awake, eyes closed) data set, and consecutive two-minute retrospective pseudo-rest (awake, eyes open) data sets for days 1-7 post-implantation. ASM dosages were recorded for days 1-7 post-implantation and drug load score (DLS) per day was calculated to standardize and compare across patients. FC was evaluated using directed and nondirected measures. Standard clinical interpretation of ictal SEEG was used to classify brain regions as EZs and non-EZs.Results:Over seven days, presumed EZs consistently had higher FC than non-EZs when using Between Imaginary Coherence (ImCoh) and Partial Directed Coherence (PDC) Inward strength, without accounting for DLS. These measures were demonstrated to be stable over a short-term period of three consecutive days with the same DLS. Between ImCoh FC differences between EZs and non-EZs were reduced with DLS decreases, whereas other measures were not affected by DLS. FC differences between EZs and non-EZs were seen during both resting-state and pseudo-rest conditions; ImCoh values were strongly correlated between the two conditions, whereas PDC values were not.Discussion:Inward and non-directed SEEG FC is higher in presumed EZs versus non-EZs, and measures are stable over time. However, certain measures may be impacted by ASM dose, as Between ImCoh differences between EZs and non-EZs are less pronounced with lower doses, and other measures such as PDC are poorly correlated across recording conditions. These findings allow novel insight into how SEEG FC measures may aid surgical localization, and how they are influenced by ASMs and other factors.

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confidence: 99%

SEEG Functional Connectivity Measures to Identify Epileptogenic Zones

et al. 2022

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“…In Japan, the more widespread use of stereotactic electroencephalography, as well as the introduction of new surgical therapies such as the responsive neurostimulator system (RNS System; NeuroPace, Inc., Mountain View, CA, USA), laser ablation (Visualase MRI-guided Laser Ablation System; Medtronic, Minneapolis, MN, USA), and deep brain stimulation, is expected to contribute to increasing the number of patients with epilepsy who can be treated surgically in the near future. [19][20][21]…”

Section: Discussionmentioning

confidence: 99%

Current Status and Future Objectives of Surgical Therapies for Epilepsy in Japan

Mikuni

Usui

Otsubo

et al. 2021

Neurol. Med. Chir.(Tokyo)

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This study investigated the number of epilepsy surgeries performed over time in Japan, and conducted a questionnaire survey of the Japan Neurosurgical Society (JNS) training program core hospitals to determine the current status and future objectives of surgical therapies and epilepsy training programs for physicians in Japan. This article presents part of a presentation delivered as a presidential address at the 44th Annual Meeting of the Epilepsy Surgery Society of Japan held in January 2021. The number of epilepsy surgeries performed per year has increased in Japan since 2011 to around 1,200 annually between 2015 and 2018. The questionnaire survey showed that 50% of the responding hospitals performed epilepsy surgery and 29% had an epilepsy center, and that these hospitals provided senior residents with education regarding epilepsy surgery. The presence of an epilepsy center in a hospital was positively correlated with the availability of long-term video electroencephalography monitoring beds as well as the number of epilepsy surgeries performed at the hospital. In regions with no medical facilities offering specialized surgical therapies for epilepsy, the JNS training program core hospitals may help improve epilepsy diagnosis and treatment. They may also increase the number of safe and effective surgeries by establishing epilepsy centers that can perform long-term video electroencephalography monitoring, providing junior neurosurgeons with training regarding epilepsy, and playing a core role in surgical therapies for epilepsy in tertiary medical areas in close cooperation with neighboring medical facilities.

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“…To quantify the overall direction of a node's connectivity, reciprocal connectivity was calculated as the difference between each node's inward and outward connectivity. All connectivity was analyzed in the theta [4][5][6][7], alpha [8][9][10][11][12], beta [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], and gamma oscillatory bands.…”

Section: Resting-state Seeg Connectivitymentioning

confidence: 99%

“…When conducting SPES on non-SOZ SEEG contacts, we observed that the SOZ power was markedly attenuated compared to baseline and significantly attenuated compared to noninvolved regions in the lowest frequency band measured (theta, 4-7 Hz) for the 23 patients consented for neurostimulation (Figure 3A, SOZ single-population t-test, p-value=2.28e-4, one-way ANOVA, p-value=2.50e-3, post-hoc pairwise t-test comparison SOZ-Non, p-value=1.80e-3). The SOZ and PZ power was not significantly altered in the alpha band [8][9][10][11][12] Hz] (Figure 3B). The SOZ and PZ power was elevated compared to baseline in both beta [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] and gamma bands , but post-hoc multiple comparisons revealed that the SOZ elevation in power was only significantly different from non-involved regions in the beta band and only from PZs in the gamma band (Figure 3C-D, beta: SOZ single-population t-test p-value=9.00e-3, one-way ANOVA p-value=2.98e-2, post-hoc pairwise t-test comparison SOZ-Non p-value=2.24e-2; gamma: SOZ single-population t-test p-value=6.70e-3, one-way ANOVA p-value=1.11e-2, post-hoc pairwise t-test comparison SOZ-PZ p-value=1.33e-2).…”

Section: Low Frequency Power Is Attenuated In Sozs When the Network I...mentioning

confidence: 99%

“…10 If these techniques fail to accurately localize SOZs, then invasive monitoring with stereotactic-electroencephalography (SEEG) can be pursued. 11 To properly localize SOZs with SEEG, the patient must remain in the hospital for days to weeks to record many seizures (ictal events). 12, 13 To reduce the morbidity of long intracranial recordings, brief resting-state (interictal) SEEG analysis has shown promise in identifying SOZs.…”

Section: Introductionmentioning

confidence: 99%

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The Interictal Suppression Hypothesis in Focal Epilepsy: Electrographic and Structural Evaluation

Johnson

Doss

Morgan

et al. 2022

Preprint

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Why are people with focal epilepsy not constantly seizing? Previous molecular work has implicated gamma-aminobutyric acid balance as integral to seizure generation and termination, but is the high-level distributed brain network involved in suppressing seizures? Recent intracranial electrographic evidence has suggested that seizure onset zones have an increased inward connectivity. Accordingly, we hypothesize that seizure onset zones are actively suppressed by the rest of the brain network during interictal states.We tested this hypothesis on 81 subjects with drug resistant focal epilepsy undergoing presurgical evaluation. We utilized intracranial electrographic resting-state and neurostimulation recordings to evaluate the network connectivity of seizure onset, propagative, and non-involved regions. We then utilized diffusion imaging to acquire estimates of white matter connectivity to evaluate structure-function coupling effects on connectivity findings. Finally, using our observations, we generated a resting-state classification model to assist clinicians in detecting seizure onset and propagative zones without the need for multiple ictal recordings.Our findings indicate that seizure onset and propagative zones demonstrate markedly increased inward connectivity and decreased outward connectivity on both resting-state and neurostimulation analyses. When controlling for distance between regions, the difference between inward vs. outward connectivity remained stable up to 80 mm between brain connections. Structure-function coupling analyses revealed that seizure onset zones exhibit abnormally enhanced coupling (hypercoupling) of surrounding regions compared to presumably healthy tissue. Using these observations, our classification models achieved a maximum held-out testing set accuracy of 92.0±2.2%.These results indicate that seizure onset zones are actively segregated and suppressed by a widespread brain network. Furthermore, this electrographically observed functional suppression is disproportionate to any observed structural connectivity alterations of the seizure onset zones. These findings have implications for the identification of seizure onset zones using only brief resting-sate recordings to reduce patient morbidity and augment the presurgical evaluation of drug resistant epilepsy. Furthermore, testing of the interictal suppression hypothesis can provide insight into potential new resective, ablative, and neuromodulation approaches to improve surgical success rates in those suffering from drug resistant focal epilepsy.

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Technical Aspects of SEEG and Its Interpretation in the Delineation of the Epileptogenic Zone

Cited by 24 publications

References 59 publications

SEEG Functional Connectivity Measures to Identify Epileptogenic Zones

SEEG Functional Connectivity Measures to Identify Epileptogenic Zones

Current Status and Future Objectives of Surgical Therapies for Epilepsy in Japan

The Interictal Suppression Hypothesis in Focal Epilepsy: Electrographic and Structural Evaluation

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