Two types of clinical ictal direct current shifts in invasive EEG of intractable focal epilepsy identified by waveform cluster analysis

Kajikawa, Shunsuke; Matsuhashi, Masao; Kobayashi, Katsuya; Hitomi, Takefumi; Daifu-Kobayashi, Masako; Tamaki, Kunihiko; Yamao, Yukihiro; Kikuchi, Takayuki; Yoshida, Kazumichi; Kunieda, Takeharu; Matsumoto, Riki; Kakita, Akiyoshi; Namiki, Takao; Tsuda, Ichiro; Miyamoto, Susumu; Takahashi, Ryōsuke; Ikeda, Akio

doi:10.1016/j.clinph.2022.02.021

Cited by 6 publications

(18 citation statements)

References 29 publications

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“…RDP was observed more frequently in the current study (76.5%) than in previous studies by Gnatkovsky et al 22 . (69.5%) and Kajikawa et al 21 . (60.8%).…”

Section: Discussioncontrasting

confidence: 63%

“…These findings suggest that wide‐band ictal EEG activities, especially icDCs, can represent the core epileptogenic area 15–17 . Similar studies have also supported the importance of icDCs before resective epilepsy surgeries 19–21 …”

Section: Introductionsupporting

confidence: 60%

“…8 In the chronic state of intractable focal epilepsy, active DC shifts are generated by the depolarization of the astrocytes in the tripartite synapse as the functional syncytium, usually before ciEEG onset by reflecting the extracellular potassium homeostasis impairment such as decreased Kir 4.1 channel on the membrane surface of astrocytes. 8,15,21 To the best of our knowledge, this is the first study to examine icDCs recorded with TC2s in detail. At several institutes worldwide, the currently available clinical digital EEG equipment includes an AC amplifier with TC2s but not with TC10s.…”

Section: Discussionmentioning

confidence: 98%

“…The characteristics of each waveform are shown in Figure 4. Based on a previous report, icDCs with TC10s were quantitatively divided into two types with a cutoff value of 8.9 s for peak latency via cluster analysis and logistic regression 21 . Therefore, we defined icDCs with a peak latency value of <8.9 s and >8.9 s as RDP and SDP, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…Based on a previous report, icDCs with TC10s were quantitatively divided into two types with a cutoff value of 8.9 s for peak latency via cluster analysis and logistic regression. 21 Therefore, we defined icDCs with a peak latency value of <8.9 s and >8.9 s as RDP and SDP, respectively. We examined the occurrence rates of RDP and SDP per electrode and per seizure at TC2s.…”

Section: Analysis Of Two Types Of Icdcs With Tc2smentioning

confidence: 99%

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Focal ictal direct current shifts by a time constant of 2 seconds were clinically useful for resective epilepsy surgery

Izumi,

Kobayashi,

Kajikawa

et al. 2023

Epilepsia

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ObjectiveIctal direct current shifts (icDCs) and ictal high‐frequency oscillations (icHFOs) have been reported as surrogate markers for better surgical outcomes in epilepsy surgery. icDCs have been classified into two types: rapid and slow development. icDCs have been investigated with a time constant of 10 s (TC10s); however, many institutes use electroencephalography with a time constant of 2 s (TC2s). This study aimed to evaluate whether icDCs can be observed adequately with TC2s; moreover, it examined the relationship between the resected core area of icDCs or icHFOs and surgical outcomes, occurrence rate of each type of icDCs, and relationship between each type of icDCs and pathology.MethodsTwenty‐five patients with intractable focal epilepsy were analyzed retrospectively. icDCs and icHFOs were defined according to common metrics. The amplitude of icDCs was defined at >200 μV and even <200 μV. The two electrodes producing the most prominent icDCs and icHFOs were defined as core electrodes. The correlation between the resected core electrode area and degree of seizure control after surgery was analyzed. icDCs were classified into two types based on a peak latency value cutoff of 8.9 s, and the occurrence rates of both patterns were investigated.ResultsicDCs (142/147 seizures [96.6%]) and icHFOs (135/147 seizures [91.8%]) occurred in all patients (100%). Compared with the amplitude of icDCs with TC10s reported in previous studies, the amplitude of icDCs with TC2s was attenuated in the current study. A significant positive correlation was observed between the resected core electrode area and degree of seizure control in both icDCs and icHFOs. A rapid development pattern was observed in 202 of 264 electrodes (76.5%).SignificanceSimilar to icDCs with TC10s, those with TC2s were observed adequately. Furthermore, favorable outcomes are expected using TC2s, which is currently available worldwide.

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“…RDP was observed more frequently in the current study (76.5%) than in previous studies by Gnatkovsky et al 22 . (69.5%) and Kajikawa et al 21 . (60.8%).…”

Section: Discussioncontrasting

confidence: 63%

Section: Introductionsupporting

confidence: 60%

Section: Discussionmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Section: Analysis Of Two Types Of Icdcs With Tc2smentioning

confidence: 99%

See 3 more Smart Citations

Focal ictal direct current shifts by a time constant of 2 seconds were clinically useful for resective epilepsy surgery

Izumi,

Kobayashi,

Kajikawa

et al. 2023

Epilepsia

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Novel and reappraised wide-band EEG findings in migraineurs: Its correlation with several clinical variables

Hosokawa,

Usami,

Tatsuoka

et al. 2024

Clinical Neurophysiology

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Ictal direct current shifts contribute to defining the core ictal focus in epilepsy surgery

Nakatani

Inouchi

Daifu-Kobayashi

et al. 2022

Brain Communications

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Identifying the minimal and optimal epileptogenic area to resect and cure is the goal of epilepsy surgery. To achieve this, EEG analysis is recognized as the most direct way to detect epileptogenic lesions from spatiotemporal perspectives. Although ictal direct-current shifts (icDCs; below 1 Hz) and ictal high-frequency oscillations (icHFOs; above 80 Hz) have received increasing attention as good indicators that can add more specific information to the conventionally defined seizure-onset zone, large cohort studies on postoperative outcomes are still lacking. This work aimed to clarify whether this additional information, particularly icDCs which is assumed to reflect extracellular potassium concentration, really improve postoperative outcomes. To assess the usefulness in epilepsy surgery, we collected unique EEG datasets recorded with a longer time constant of 10 sec using an alternate current amplifier. 61 patients [15 with mesial temporal lobe epilepsy and 46 with neocortical epilepsy] who had undergone invasive presurgical evaluation for medically refractory seizures at five institutes in Japan, were retrospectively enrolled in this study. Among intracranially implanted electrodes, the two core electrodes of both icDCs and icHFOs were independently identified by board-certified clinicians based on unified methods. The occurrence patterns, such as their onset time, duration, and amplitude (power) were evaluated to extract the features of both icDCs and icHFOs. Additionally, we examined whether the resection ratio of the core electrodes of icDCs and icHFOs independently correlated with favorable outcomes. A total of 53 patients with 327 seizures were analyzed for wide-band EEG analysis, and 49 patients were analyzed for outcome analysis. icDCs were detected in the seizure-onset zone more frequently than icHFOs among both patients (92% vs. 71%) and seizures (86% vs. 62%). Additionally, icDCs significantly preceded icHFOs in patients exhibiting both biomarkers, and icDCs occurred more frequently in neocortical epilepsy patients than in mesial temporal lobe epilepsy patients. Finally, although a low corresponding rate was observed for icDCs and icHFOs (39%) at the electrode level, complete resection of the core area of icDCs significantly correlated with favorable outcomes, similar to icHFO outcomes. Our results provide a proof of concept that the independent significance of icDCs from icHFOs should be considered as reliable biomarkers to achieve favorable outcomes in epilepsy surgery. Moreover, the different distribution of the core areas of icDCs and icHFOs may provide new insights into the underlying mechanisms of epilepsy, in which not only neurons but also glial cells may be actively involved via extracellular potassium levels.

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Two types of clinical ictal direct current shifts in invasive EEG of intractable focal epilepsy identified by waveform cluster analysis

Cited by 6 publications

References 29 publications

Focal ictal direct current shifts by a time constant of 2 seconds were clinically useful for resective epilepsy surgery

Focal ictal direct current shifts by a time constant of 2 seconds were clinically useful for resective epilepsy surgery

Novel and reappraised wide-band EEG findings in migraineurs: Its correlation with several clinical variables

Ictal direct current shifts contribute to defining the core ictal focus in epilepsy surgery

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