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• The most prevalent seizure-onset patterns (SOPs) are low frequency periodic spikes (LFPS) and low-voltage fast activity (LVFA). • LFPS had the most divergent terminology, whereas LVFA had the most reproducible terminology. • Some SOP terms were inconsistent with standard EEG terminology. Increasing evidence suggests that the seizure-onset pattern (SOP) in stereo-electroencephalography (SEEG) is important for localizing the "true" seizure onset. Specifically, SOPs with low-voltage fast activity (LVFA) are associated with seizure-free outcome (Engel I). However, several classifications and various terms corresponding to the same pattern have been reported, challenging its use in clinical practice. Following the Preferred Reporting Items of Systematic reviews and Meta-Analyses (PRISMA) guideline, we performed a systematic review of studies describing SOPs along with accompanying figures depicting the reported SOP in SEEG. Of 1799 studies, 22 met the selection criteria. Among the various SOPs, we observed that the terminology for low frequency periodic spikes exhibited the most variability, whereas LVFA is the most frequently used term of this pattern. Some SOP terms were inconsistent with standard EEG terminology. Finally, there was a significant but weak association between presence of LVFA and seizure-free outcome. Divergent terms were used to describe the same SOPs and some of these terms showed inconsistencies with the standard EEG terminology. Additionally, our results confirmed the link between patterns with LVFA and seizure-free outcomes. However, this association was not strong. These results underline the need for standardization of SEEG terminology. [ABSTRACT FROM AUTHOR]

• Resection should include ictal single equivalent current dipole (SECD), interictal SECD and MRI lesion localization, when feasible. • Concordant ictal and interictal SECDs can be a favorable predictor of seizure freedom if the areas can be safely resected. • Among SECD, dynamic statistical parametric mapping, and linearly constrained minimum variance, SECD should be considered the first line of analysis for ictal MEG when the data is amenable to SECD source localization. The significance of ictal magnetoencephalography (MEG) is not well appreciated. We evaluated the relationships between ictal MEG, MRI, intracranial electroencephalography (ICEEG), surgery and postoperative seizure outcome. A total of 45 patients (46 cases) with ictal MEG who underwent epilepsy surgery was included. We examined the localization of each modality, surgical resection area and seizure freedom after surgery. Twenty-one (45.7%) out of 46 cases were seizure-free at more than 6 months follow-up. Median duration of postoperative follow-up was 16.5 months. The patients in whom ictal, interictal single equivalent current dipole (SECD) and MRI lesion localization were completely included in the resection had a higher chance of being seizure-free significantly (p < 0.05). Concordance between ictal and interictal SECD localizations was significantly associated with seizure-freedom. Concordance between MRI lesion and ictal SECD, concordance between ictal ICEEG and ictal and interictal SECD, as well as concordance between ictal ICEEG and MRI lesion were significantly associated with seizure freedom. Ictal MEG can contribute useful information for delineating the resection area in epilepsy surgery. Resection should include ictal, interictal SECDs and MRI lesion localization, when feasible. Concordant ictal and interictal SECDs on MEG can be a favorable predictor of seizure freedom. [ABSTRACT FROM AUTHOR]

• High-density (hd) ECoG increases the number of Fast Ripples (FR) detected during epilepsy surgery. • hd-ECoG improves the prediction of seizure outcome after resective epilepsy surgery. • hd-ECoG may advance seizure freedom after epilepsy surgery. Residual fast ripples (FR) in the intraoperative ECoG are highly specific predictors of postsurgical seizure recurrence. However, a FR is generated by a small patch of cortical tissue. Spatial sampling with standard electrodes may thus miss clinically relevant information. We analyzed FR rates in the intraoperative ECoG of 22 patients that underwent resective epilepsy surgery. We used standard electrodes with 10 mm inter-contact spacing (standard ECoG) in 14 surgeries and high-density grid electrodes with 5 mm spacing (hd-ECoG) in 8 surgeries. We detected FR using a previously validated automatic detector. Postoperative seizure freedom was achieved in 14/22 (64%) cases. Across all 42 ECoG recordings, FR rates were higher for hd-ECoG than for standard ECoG. In the 14 seizure free patients (ILAE 1), no residual FR were detected (specificity = 100%). In the 8 patients with seizure recurrence (ILAE > 1), residual FR were detected in 1/7 standard ECoG and 1/1 hd-ECoG (Accuracy ACC standard ECoG = 57%, CI [29% 82%], ACC hd-ECoG = 100%, CI [63% 100%]). Denser spatial sampling by hd-ECoG improved FR detection compared to standard ECoG. Hd-ECoG may advance seizure freedom after epilepsy surgery. [ABSTRACT FROM AUTHOR]

Highlights • Prospective study evaluating the significance of epileptic activity in ECoGs in children. • Relationship between fast activity recorded in the ECoGs and unfavourable seizure outcomes. • Fast activity recorded with a relatively simple ECoG-equipment might be an alternative to high-frequency oscillations. Abstract Objective To evaluate prospectively the informative/prognostic value of epileptic discharges in the post-resection ECoGs of children with drug-resistant epilepsies and Focal Cortical Dysplasia type II (FCD-II). Methods Included were consecutive patients with focal epilepsies and suspected FCD-II who were planned for single-stage epilepsy surgery based on non-invasive presurgical evaluation results. Intraoperative ECoGs were recorded using a 32-channel system with strip- and/or grid-electrodes. Spikes were defined as transients with a mainly negative component and duration of 20–70 ms. Fast activity was defined as rhythmic bursts of polyspikes >13 Hz. All ECoGs were analysed visually. The significance of both spikes and fast activity in the post-resection ECoG for seizure outcomes 24 months after surgery was evaluated. Results Data from 18 patients (five girls) were analysed. 10/18 patients (55.6%) showed spikes in their post-resection ECoGs, five of them showed additional fast activity. 24 months after surgery, 12/18 patients (66.7%) were seizure-free. There was a significant correlation between unfavorable seizure outcomes and fast activity in the post-resection ECoGs (p = 0.009), whereas spikes alone were not predictive (p = 0.502). Conclusion Even when recorded with non-sophisticated techniques, presence of fast activity in post-resection ECoGs might be a valid negative outcome-predictor after surgery in paediatric patients with FCD-II associated drug-resistant epilepsies. Significance Fast activity recorded with a relatively simple ECoG equipment seems also to have prognostic significance and by this might be an alternative to HFOs recorded with highly sophisticated and expensive technologies. [ABSTRACT FROM AUTHOR]

Objective To evaluate the prognostic value of postoperative EEGs to estimate post anterior temporal lobectomy (ATL) seizure outcome. Methods We studied postoperative EEGs in 325 consecutive patients who had minimum five years of post-ATL followup. Interictal epileptiform discharges (IEDs) present only during sleep were classified as sleep IEDs. We defined favorable final-year outcome as no seizures during the final one year and favorable absolute-postoperative outcome as no seizures during the entire postoperative period. Results At mean follow-up of 7.3 ± 1.8 years, 281 (86.5%) patients had favorable final-year outcome while 161 (49.5%) had favorable absolute-postoperative outcome. IEDs on three months and one year EEG were associated with unfavorable outcomes while IEDs at 7th day had no association with outcomes. Sleep record increased the yield of IEDs by 30% at each time-point without compromising predictive value. EEG at one year predicted the risk of seizure recurrence on drug withdrawal. Conclusion While EEG at three months and at one-year after ATL predicted seizure outcome, EEG at 7th day was not helpful. Sleep record increases the sensitivity of postoperative EEG without compromising specificity. Significance Both awake and sleep EEG provide useful information in postoperative period following ATL. [ABSTRACT FROM AUTHOR]

Objective High frequency oscillations (HFOs) and in particular fast ripples (FRs) in the post-resection electrocorticogram (ECoG) have recently been shown to be highly specific predictors of outcome of epilepsy surgery. FR visual marking is time consuming and prone to observer bias. We validate here a fully automatic HFO detector against seizure outcome. Methods Pre-resection ECoG dataset ( N = 14 patients) with visually marked HFOs were used to optimize the detector’s parameters in the time–frequency domain. The optimized detector was then applied on a larger post-resection ECoG dataset ( N = 54) and the output was compared with visual markings and seizure outcome. The analysis was conducted separately for ripples (80–250 Hz) and FRs (250–500 Hz). Results Channel-wise comparison showed a high association between automatic detection and visual marking ( p < 0.001 for both FRs and ripples). Automatically detected FRs were predictive of clinical outcome with positive predictive value PPV = 100% and negative predictive value NPV = 62%, while for ripples PPV = 43% and NPV = 100%. Conclusions Our automatic and fully unsupervised detection of HFO events matched the expert observer’s performance in both event selection and outcome prediction. Significance The detector provides a standardized definition of clinically relevant HFOs, which may spread its use in clinical application. [ABSTRACT FROM AUTHOR]

Objective: We hypothesized that high frequency oscillations (HFOs) are differently suppressed during rapid eye movement sleep (REM) between epileptogenic and less epileptogenic cortices, and that the suppressive effect can serve as a specific marker of epileptogenicity. Methods: Intracranial electroencephalography (EEG) was recorded in 13 patients with drug-resistant epilepsy. HFOs between 80 and 200 Hz were semi-automatically detected from total 15-min EEG epochs each for REM and slow wave sleep (SWS). z-Score of HFO occurrence rate was calculated from the baseline rate derived from non-epileptogenic cortex. Intracranial electrodes were labeled as REM dominant HFO (RdH) if REM z-score was greater than SWS z-score or as SWS dominant HFO (SdH) if SWS z-score was greater than REM z-score. Relationship of electrode location to the area of surgical resection was compared between RdH and SdH electrodes. Results: Out of 1070 electrodes, 101 were defined as RdH electrodes and 115 as SdH electrodes. RdH electrodes were associated with the area of resection in patients with postoperative seizure freedom (P < 0.001), but not in patients without seizure freedom. Conclusions: HFOs near the epileptogenic zone are less suppressed during REM. Significance: The less suppressive effect of REM may provide a specific marker of epileptogenicity. [ABSTRACT FROM AUTHOR]

Abstract: Objective: High-gamma oscillations (HGOs) (60–99Hz) have been suggested to correlate with seizure onset zones and seizure outcomes. We investigated the correlation between the extent of removal of ictal HGO generating areas and postoperative seizure outcome in neocortical epilepsy (NE). Methods: Twenty three patients with medically intractable NE underwent chronic intracranial electroencephalography (iEEG) using subdural electrodes. Ictal HGOs and superimposed undersampled ripples within ±3s of video-iEEG ictal onset were extracted by wavelet clustering and thresholding. Cluster epileptogenicity indices (CEIs) were calculated. The temporal analysis window was locked to the timing of the maximum CEI wavecluster. Root mean square amplitudes, cross-correlation synchronies and the local focus indices within the temporal window were calculated. Results: Percentages of resected maximum CEI waveclusters and HGO zones with high standardised amplitudes (>3), high cross-correlation synchronies (>0.9) and high local focus indices (>2) were significantly higher in the seizure-free group compared to the not seizure-free group (p =0.036, p =0.018, and p =0.026, respectively). Conclusions: The automatic quantitative ictal HGO analysis may be effective in delineating the epileptogenic zone. Significance: HGO analysis may be helpful for improving post-resection seizure outcome in NE in the future. [Copyright &y& Elsevier]

Abstract: Objective: To evaluate the antiepileptic effect of low-frequency rTMS (repetitive transcranial magnetic stimulation) in the patients with intractable epilepsy. Methods: We enrolled 35 patients with localization-related epilepsy who had experienced at least one complex partial seizure or a secondarily generalized seizure per week on a constant antiepileptic drug regimen over an 8-week period. rTMS was administered using a Rapid 2 magnetic stimulator with an air-cooled coil at 0.5Hz for 5 consecutive days at 100% of rMT (resting motor threshold). Patients were divided into a focal stimulation group with a localized epileptic focus, or a non-focal stimulation group with a non-localized or multifocal epileptic focus. These two groups were then randomly subdivided into four subgroups depending on the total number of stimulations administered, i.e., 3000 pulse and 1500 pulse subgroups. Weekly seizure frequencies were determined for 8 weeks before and after rTMS. To compare the number of interictal spikes before and after rTMS, EEG was recorded twice before (1st day) and after rTMS (5th day). Results: Mean weekly seizure frequency was non-significantly decreased after rTMS (8.4→6.8/week, −13.9%). Longer stimulation subgroups (3000 pulses, −23.0%) tended to have fewer seizures than shorter stimulation subgroups (1500 pulses, −3.0%), without statistical significance. TMS stimulation site and structural brain lesions did not influence seizure outcome. However, interictal spikes significantly decreased (−54.9%, P =0.012) after rTMS and they totally disappeared in 6 patients (17.1%, 6/35). Conclusions: Low-frequency rTMS reduced interictal spikes, but its effect on seizure outcome was not significant. Focal stimulation for a longer duration tended to further reduce seizure frequency. Significance: These findings may help clinicians to further investigate the therapeutic potential of the rTMS for patients with intractable epilepsy. [Copyright &y& Elsevier]