Simultaneously recorded intracranial and scalp high frequency oscillations help identify patients with poor postsurgical seizure outcome

ObjectiveHigh frequency oscillations (HFO) between 80–500 Hz are markers of epileptic areas in intracranial and maybe also scalp EEG. We investigate simultaneous recordings of scalp and intracranial EEG and hypothesize that scalp HFOs provide important additional clinical information in the presurgical setting.MethodsSpikes and HFOs were visually identified in all intracranial scalp EEG channels. Analysis of correlation of event location between intracranial and scalp EEG as well as relationship between events and the SOZ and zone of surgical removal was performed.Results24 patients could be included, 23 showed spikes and 19 HFOs on scalp recordings. In 15/19 patients highest scalp HFO rate was located over the implantation side, with 13 patients having the highest scalp and intracranial HFO rate over the same region. 17 patients underwent surgery, 7 became seizure free. Patients with poor post-operative outcome showed significantly more regions with HFO than those with seizure free outcome.ConclusionsScalp HFOs are mostly located over the SOZ. Widespread scalp HFOs are indicative of a larger epileptic network and associated with poor postsurgical outcome.SignificanceAnalysis of scalp HFO add clinically important information about the extent of epileptic areas during presurgical simultaneous scalp and intracranial EEG recordings.     

Predictive value of intraoperative blink reflex monitoring for surgical outcome during microvascular decompression for hemifacial spasm

ObjectiveTo investigate the prognostic and predictive value of intraoperative blink reflex (BR) monitoring during microvascular decompression (MVD) for hemifacial spasm (HFS).MethodsWe retrospectively reviewed 41 patients with HFS undergoing MVD with intraoperative BR and lateral spread response (LSR) monitoring. Facial spasm was evaluated for six months postoperatively.ResultsThe BR resolved in 38 patients and persisted in three after MVD. For patients who exhibited BR resolution, 1-day, 1-month, and 6-month follow-ups revealed that 35 (92.1%), 35 (92.1%), and 38 (100%) patients had spasm resolution, respectively. However, of the three patients with persistent BR, one (33.3%), one (33.3%), and zero (0%) patients exhibited spasm resolution at the three corresponding follow-ups. We found a statistically significant difference in spasm resolution between the persistent and resolved BR groups at six months postoperatively. A comparison between intraoperative BR and LSR monitoring revealed that BR was a better predictor of clinical outcomes.ConclusionsIntraoperative BR monitoring is a potentially useful tool to help facilitate an adequate decompression and is a reliable prognostic predictor of surgical outcome.SignificanceThis study is the first to document the relationship between intraoperative BR monitoring and surgical outcome in patients with HFS.     

The “Connectivity Epileptogenicity Index ” (cEI), a method for mapping the different seizure onset patterns in StereoElectroEncephalography recorded seizures

ObjectiveLocalization of epileptogenic brain regions is a crucial aim of pre-surgical evaluation of patients with drug-resistant epilepsy. Several methods have been proposed to identify the seizure onset zone, particularly based on the detection of fast activity. Most of these methods are inefficient to detect slower patterns of onset that account for 20–30% of commonly observed Stereo-Electro-Encephalography (SEEG) patterns. We seek to evaluate the performance of a new quantified measure called the Connectivity Epileptogenicity Index (cEI) in various types of seizure onset patterns.MethodsWe studied SEEG recorded seizures from 51 patients, suffering from focal drug-resistant epilepsy. The cEI combines a directed connectivity measure (“out-degrees”) and the original epileptogenicity index (EI). Quantified results (Out-degrees, cEI and EI) were compared to visually defined seizure onset zone (vSOZ). We computed recall (sensitivity) and precision (proportion of correct detections within all detections) with vSOZ as a reference. The quality of the detector was quantified by the area under the precision-recall curve.ResultsBest results (in terms of match with vSOZ) were obtained for cEI. For seizures with fast onset patterns, cEI and EI gave comparable results. For seizures with slow onset patterns, cEI gave a better estimation of the vSOZ than EI.ConclusionsWe observed that cEI discloses better performance than EI when seizures starts with slower patterns and equal to EI in seizures with fast onset patterns.SignificanceThe cEI is a promising new tool for epileptologists, that helps characterizing the seizure onset zone in sEEG, in a robust way despite variations in seizure onset patterns.     

Source imaging of seizure onset predicts surgical outcome in pediatric epilepsy

ObjectiveTo assess whether ictal electric source imaging (ESI) on low-density scalp EEG can approximate the seizure onset zone (SOZ) location and predict surgical outcome in children with refractory epilepsy undergoing surgery.MethodsWe examined 35 children with refractory epilepsy. We dichotomized surgical outcome into seizure- and non-seizure-free. We identified ictal onsets recorded with scalp and intracranial EEG and localized them using equivalent current dipoles and standardized low-resolution magnetic tomography (sLORETA). We estimated the localization accuracy of scalp EEG as distance of scalp dipoles from intracranial dipoles. We also calculated the distances of scalp dipoles from resection, as well as their resection percentage and compared between seizure-free and non-seizure-free patients. We built receiver operating characteristic curves to test whether resection percentage predicted outcome.ResultsResection distance was lower in seizure-free patients for both dipoles (p = 0.006) and sLORETA (p = 0.04). Resection percentage predicted outcome with a sensitivity of 57.1% (95% CI, 34–78.2%), a specificity of 85.7% (95% CI, 57.2–98.2%) and an accuracy of 68.6% (95% CI, 50.7–83.5%) (p = 0.01).ConclusionIctal ESI performed on low-density scalp EEG can delineate the SOZ and predict outcome.SignificanceSuch an application may increase the number of children who are referred for epilepsy surgery and improve their outcome.     

Measuring the effects of first antiepileptic medication in Temporal Lobe Epilepsy: Predictive value of quantitative-EEG analysis

ObjectiveTo determine the quantitative EEG responses in a population of drug-naïve patients with Temporal Lobe Epilepsy (TLE) after Levetiracetam (LEV) initiation as first antiepileptic drug (AED). We hypothesized that the outcome of AED treatment can be predicted from EEG data in patients with TLE.MethodsTwenty-three patients with TLE and twenty-five healthy controls were examined. Clinical outcome was dichotomized into seizure-free (SF) and non-seizure-free (NSF) after two years of LEV. EEG parameters were compared between healthy controls and patients with TLE at baseline (EEG^pre) and after three months of AED therapy (EEG^pre-post) and between SF and NSF patients. Receiver Operating Characteristic curves models were built to test whether EEG parameters predicted outcome.ResultsAED therapy induces an increase in EEG power for Alpha (p = 0.06) and a decrease in Theta (p < 0.05). Connectivity values were lower in SF compared to NSF patients (p < 0.001). Quantitative EEG predicted outcome after LEV treatment with an estimated accuracy varying from 65.2% to 91.3% (area under the curve [AUC] = 0.56–0.93) for EEG^pre and from 69.9% to 86.9% (AUC = 0.69–0.94) for EEG^pre-post.ConclusionsAED therapy induces EEG modifications in TLE patients, and such modifications are predictive of clinical outcome.SignificanceQuantitative EEG may help understanding the effect of AEDs in the central nervous system and offer new prognostic biomarkers for patients with epilepsy.     

Phase-amplitude coupling of ripple activities during seizure evolution with theta phase

ObjectiveHigh-frequency activities (HFAs) and phase-amplitude coupling (PAC) are key neurophysiological biomarkers for studying human epilepsy. We aimed to clarify and visualize how HFAs are modulated by the phase of low-frequency bands during seizures.MethodsWe used intracranial electrodes to record seizures of focal epilepsy (12 focal-to-bilateral tonic-clonic seizures and three focal-aware seizures in seven patients). The synchronization index, representing PAC, was used to analyze the coupling between the amplitude of ripples (80–250 Hz) and the phase of lower frequencies. We created a video in which the intracranial electrode contacts were scaled linearly to the power changes of ripple.ResultsThe main low frequency band modulating ictal-ripple activities was the θ band (4–8 Hz), and after completion of ictal-ripple burst, δ (1–4 Hz)-ripple PAC occurred. The ripple power increased simultaneously with rhythmic fluctuations from the seizure onset zone, and spread to other regions.ConclusionsRipple activities during seizure evolution were modulated by the θ phase. The PAC phenomenon was visualized as rhythmic fluctuations.SignificanceRipple power associated with seizure evolution increased and spread with fluctuations. The θ oscillations related to the fluctuations might represent the common neurophysiological processing involved in seizure generation.     

Navigated repetitive transcranial magnetic stimulation improves the outcome of postsurgical paresis in glioma patients – A randomized,double-blinded trial

BackgroundNavigated repetitive transcranial magnetic stimulation (nrTMS) is effective therapy for stroke patients. Neurorehabilitation could be supported by low-frequency stimulation of the non-damaged hemisphere to reduce transcallosal inhibition.ObjectiveThe present study examines the effect of postoperative nrTMS therapy of the unaffected hemisphere in glioma patients suffering from acute surgery-related paresis of the upper extremity (UE) due to subcortical ischemia.MethodsWe performed a randomized, sham-controlled, double-blinded trial on patients suffering from acute surgery-related paresis of the UE after glioma resection. Patients were randomly assigned to receive either low frequency nrTMS (1 Hz, 15 min) or sham stimulation directly before physical therapy for 7 consecutive days. We performed primary and secondary outcome measures on day 1, on day 7, and at a 3-month follow-up (FU). The primary endpoint was the change in Fugl-Meyer Assessment (FMA) at FU compared to day 1 after surgery.ResultsCompared to the sham stimulation, nrTMS significantly improved outcomes between day 1 and FU based on the FMA (mean [95% CI] +31.9 [22.6, 41.3] vs. +4.2 [-4.1, 12.5]; P = .001) and the National Institutes of Health Stroke Scale (NIHSS) (−5.6 [-7.5, −3.6] vs. −2.4 [-3.6, −1.2]; P = .02). To achieve a minimal clinically important difference of 10 points on the FMA scale, the number needed to treat is 2.19.ConclusionThe present results show that patients suffering from acute surgery-related paresis of the UE due to subcortical ischemia after glioma resection significantly benefit from low-frequency nrTMS stimulation therapy of the unaffected hemisphere.Clinical trial registrationLocal institutional registration: 12/15; ClinicalTrials.gov number: NCT03982329     

Association of cortical spreading depression and seizures in patients with medically intractable epilepsy

ObjectiveMonitoring of the ultra-low frequency potentials, particularly cortical spreading depression (CSD), is excluded in epilepsy monitoring due to technical barriers imposed by the scalp ultra-low frequency electroencephalogram (EEG). As a result, clinical studies of CSD have been limited to invasive EEG. Therefore, the occurrence of CSD and its interaction with epileptiform field potentials (EFP) require investigation in epilepsy monitoring.MethodsUsing a novel AC/DC-EEG approach, the occurrence of DC potentials in patients with intractable epilepsy presenting different symptoms of aura was investigated during long-term video-EEG monitoring.ResultsVarious forms of slow potentials, including simultaneous negative direct current (DC) potentials and prolonged EFP, propagated negative DC potentials, and non-propagated single negative DC potentials were recorded from the scalp of the epileptic patients. The propagated and single negative DC potentials preceded the prolonged EFP with a time lag and seizure appeared at the final shoulder of some instances of the propagated negative DC potentials. The slow potential deflections had a high amplitude and prolonged duration and propagated slowly through the brain. The high-frequency EEG was suppressed in the vicinity of the negative DC potential propagations.ConclusionsThe study is the first to report the recording of the propagated and single negative DC potentials with EFP at the scalp of patients with intractable epilepsy. The negative DC potentials preceded the prolonged EFP and may trigger seizures. The propagated and single negative DC potentials may be considered as CSD.SignificanceRecordings of CSD may serve as diagnostic and prognostic monitoring tools in epilepsy.     

Predictive factors for the development of epilepsy after ischemic stroke

ObjectivesIschemic stroke is one of the most common causes of epilepsy in adults. The incidence of post-stroke epilepsy (PSE) is approximately 7%. Risk factors are higher stroke severity, cortical localization, higher National Institute of Health Stroke Scale (NIHSS) upon admission and acute symptomatic seizures. We analyzed the predictive factors of PSE development in our population.Materials and methodsRetrospective observational cohort of adult patients (age ≥ 18 years) with ischemic stroke assessed between January 2012 and June 2020. Patients with personal history of epilepsy and potentially epileptogenic structural injury other than acute or chronic stroke were excluded. Demographic, clinical and imaging variables were evaluated in a multivariate analysis for independent risk factors associated with PSE.ResultsMedical records of 1586 stroke patients were reviewed, 691 met the inclusion criteria and had at least one year of follow-up. Of them, 428 (61.9%) were males. During follow-up, 6.2% had diagnosis of PSE (42/691) with a higher frequency of: previous ischemic stroke, higher NIHSS upon admission, treatment with rt-PA, higher Fazekas scale grade, cortical involvement, hemorrhagic transformation, acute symptomatic seizures, longer hospitalization and higher modified Rankin Scale (mRS) at discharge compared to the group without PSE. In a multivariate analysis, acute symptomatic seizures (OR=3.22, p: 0.033), cortical involvement (OR=0.274, p < 0.05), Fazekas scale score (OR=0.519, p < 0.05) and mRS at discharge (OR=1.33, p: 0.043) were independent risk factors.ConclusionsThe variables related to higher risk of PSE were similar to those reported in the literature, highlighting the importance of neuroimaging findings, acute symptomatic seizures during hospitalization and neurological deficit at discharge. The data obtained will serve as the basis for construction of predictive models, allowing to individualize PSE probability in our population.     

Evidence of state-dependence in the effectiveness of responsive neurostimulation for seizure modulation

BackgroundAn implanted device for brain-responsive neurostimulation (RNS® System) is approved as an effective treatment to reduce seizures in adults with medically-refractory focal epilepsy. Clinical trials of the RNS System demonstrate population-level reduction in average seizure frequency, but therapeutic response is highly variable.HypothesisRecent evidence links seizures to cyclical fluctuations in underlying risk. We tested the hypothesis that effectiveness of responsive neurostimulation varies based on current state within cyclical risk fluctuations.MethodsWe analyzed retrospective data from 25 adults with medically-refractory focal epilepsy implanted with the RNS System. Chronic electrocorticography was used to record electrographic seizures, and hidden Markov models decoded seizures into fluctuations in underlying risk. State-dependent associations of RNS System stimulation parameters with changes in risk were estimated.ResultsHigher charge density was associated with improved outcomes, both for remaining in a low seizure risk state and for transitioning from a high to a low seizure risk state. The effect of stimulation frequency depended on initial seizure risk state: when starting in a low risk state, higher stimulation frequencies were associated with remaining in a low risk state, but when starting in a high risk state, lower stimulation frequencies were associated with transition to a low risk state. Findings were consistent across bipolar and monopolar stimulation configurations.ConclusionThe impact of RNS on seizure frequency exhibits state-dependence, such that stimulation parameters which are effective in one seizure risk state may not be effective in another. These findings represent conceptual advances in understanding the therapeutic mechanism of RNS, and directly inform current practices of RNS tuning and the development of next-generation neurostimulation systems.     

Continuous electroencephalography characteristics and acute symptomatic seizures in COVID-19 patients

ObjectiveAs concerns regarding neurological manifestations in COVID-19 (coronavirus disease 2019) patients increase, limited data exists on continuous electroencephalography (cEEG) findings in these patients. We present a retrospective cohort study of cEEG monitoring in COVID-19 patients to better explore this knowledge gap.MethodsAmong 22 COVID-19 patients, 19 underwent cEEGs, and 3 underwent routine EEGs (<1 h). Demographic and clinical variables, including comorbid conditions, discharge disposition, survival and cEEG findings, were collected.ResultscEEG was performed for evaluation of altered mental status (n = 17) or seizure-like events (n = 5). Five patients, including 2 with epilepsy, had epileptiform abnormalities on cEEG. Two patients had electrographic seizures without a prior epilepsy history. There were no acute neuroimaging findings. Periodic discharges were noted in one-third of patients and encephalopathic EEG findings were not associated with IV anesthetic use.ConclusionsInterictal epileptiform abnormalities in the absence of prior epilepsy history were rare. However, the discovery of asymptomatic seizures in two of twenty-two patients was higher than previously reported and is therefore of concern.SignificancecEEG monitoring in COVID-19 patients may aid in better understanding an epileptogenic potential of SARS-CoV2 infection. Nevertheless, larger studies utilizing cEEG are required to better examine acute epileptic risk in COVID-19 patients.     

EEG functional connectivity contributes to outcome prediction of postanoxic coma

ObjectiveTo investigate the additional value of EEG functional connectivity features, in addition to non-coupling EEG features, for outcome prediction of comatose patients after cardiac arrest.MethodsProspective, multicenter cohort study. Coherence, phase locking value, and mutual information were calculated in 19-channel EEGs at 12 h, 24 h and 48 h after cardiac arrest. Three sets of machine learning classification models were trained and validated with functional connectivity, EEG non-coupling features, and a combination of these. Neurological outcome was assessed at six months and categorized as “good” (Cerebral Performance Category [CPC] 1–2) or “poor” (CPC 3–5).ResultsWe included 594 patients (46% good outcome). A sensitivity of 51% (95% CI: 34–56%) at 100% specificity in predicting poor outcome was achieved by the best functional connectivity-based classifier at 12 h after cardiac arrest, while the best non-coupling-based model reached a sensitivity of 32% (0–54%) at 100% specificity using data at 12 h and 48 h. Combination of both sets of features achieved a sensitivity of 73% (50–77%) at 100% specificity.ConclusionFunctional connectivity measures improve EEG based prediction models for poor outcome of postanoxic coma.SignificanceFunctional connectivity features derived from early EEG hold potential to improve outcome prediction of coma after cardiac arrest.     

Parieto-premotor functional connectivity changes during parietal lobe seizures are associated with motor semiology

ObjectivesParietal lobe seizures (PLS) are characterized by multiple clinical manifestations including motor signs. The mechanisms underlying the occurrence of motor signs are poorly understood. The main objective of this work was to estimate the functional coupling of brain regions associated with this clinical presentation.MethodsWe retrospectively selected patients affected by drug-resistant epilepsy who underwent Stereoelectroencephalography (SEEG) for pre-surgical evaluation and in whom the seizure onset zone (SOZ) was located in the parietal cortex. The SOZ was defined visually and quantitatively by the epileptogenicity index (EI) method. Two groups of seizures were defined according to the presence (“motor seizures”) or the absence (“non-motor seizures”) of motor signs. Functional connectivity (FC) estimation was based on pairwise nonlinear regression analysis (h² coefficient). To study FC changes between parietal, frontal and temporal regions, for each patient, z-score values of 16 cortico-cortical interactions were obtained comparing h² coefficients of pre-ictal, seizure onset and seizure propagation periods.ResultsWe included 22 patients, 13 with “motor seizures” and 9 with “non-motor seizures”. Resective surgery was performed in 14 patients, 8 patients had a positive surgical outcome (Engel’s class I and II). During seizure onset period, a decrease of FC was observed and was significantly more important (in comparison with background period) in “motor” seizures. This was particularly observed between parietal operculum/post-central gyrus (OP/PoCg) and mesial temporal areas. During seizure propagation, a FC increase was significantly more important (in comparison with seizure onset) in “motor seizures”, in particular between lateral pre-motor (pmL) area and precuneus, pmL and superior parietal lobule (SPL) and between inferior parietal lobule (IPL) and supplementary motor area (SMA).ConclusionsOur study shows that motor semiology in PLS is accompanied by an increase of FC between parietal and premotor cortices, significantly different than what is observed in PLS without motor semiology.SignificanceOur results indicate that preferential routes of coupling between parietal and premotor cortices are responsible for the prominent motor presentation during PLS.     

Predictive value of the combination between the intracranial arterial culprit plaque characteristics and the Essen Stroke Risk Score for short-term stroke recurrence

AimIn the current study we aim the identification of the culprit plaque characteristics of intracranial arteries using high-resolution magnetic resonance vessel wall imaging (HR-MR-VWI). Moreover, we target the evaluation of the predictive value of culprit plaque characteristics for short-term stroke recurrence combined with ESRS.Materials and methodsWe conducted a prospective cohort study on 342 patients diagnosed with symptomatic intracranial atherosclerotic stenosis (sICAS), out of which 243 were men and 99 were women with an average age of 64 ± 12 years. 184 cases of anterior circulation ischemia (ACIS) and 158 cases of posterior circulation ischemia (PCIS) were included in the study. All of them underwent HR-MR-VWI during the period between February 2020 and June 2021 in the Second Affiliated Hospital of Nantong University, Nantong, China. The culprit vessel and culprit plaque characteristics were assessed based on HR-MR-VWI images, and the patients' ESRS were obtained from the electronic medical records of the hospital. Concerning the obtained results from the 6-month follow-up, the patients were divided into the non-recurrence group and the recurrence group, and the differences in the above-mentioned features between the two groups were compared. The univariate Cox regression analysis combined with ESRS was performed to screen out the independent risk factors associated with recurrent stroke with P < 0.1. Receiver operating characteristic curves (ROC curves) were plotted to analyze the predictive performance of the culprit plaque characteristics, ESRS and combined variables for stroke recurrence. We used the area under the curve (AUC) ROC, while the sensitivity and specificity were calculated at the optimal threshold. The Delong test was employed to compare the quality of the AUC of the predictors.ResultsA total of 15.5% (53/342) of patients had a stroke recurrence within six months, with statistically significant differences (P < 0.05) between the two groups regarding the ESRS, medical history of diabetes mellitus, myocardial infarction, data for previous acute ischemic stroke (AIS) or transient ischemic attack(TIA), history of peripheral vascular disease, and serum brain natriuretic peptide level. In the patients with ACIS, the incidence of hyperintensity on the T1-weighted imaging (T1WI) was significantly different between the recurrence and the non-recurrence groups (P < 0.05). In the patients with PCIS, statistically significant differences between the recurrence and the non-recurrence group were detected in the culprit plaque burden, degree of enhancement, and incidence of hyperintensity on T1WI (P < 0.05). The ESRS (hazard ratios [HR], 1.598, 95% confidence interval [CI], 1.193–2.141, P = 0.002) ,degree of enhancement (HR = 1.764, 95% CI 0.985–3.087, P = 0.047) and hyperintensity on T1WI (HR = 2.745, 95% CI 1.373–5.488, P = 0.004) proved to be independent risk factors for stroke recurrence. The ESRS predicted stroke recurrence with AUC = 0.618 (95% CI 0.564–0.670), while the best cut-off value was 2 points. Furthermore, the registered sensitivity and specificity were 60.4% and 58.5%, respectively. Regarding the degree of enhancement in the culprit plaque, the prediction of stroke recurrence was with AUC = 0.628 (95% CI 0.574–0.679) as well as with sensitivities and specificities of 58.5% and 64.4%, respectively. Regarding the hyperintensity on T1WI in culprit plaque, the prediction of stroke recurrence was with AUC = 0.678 (95% CI 0.626–0.727) as well as with sensitivities and specificities of 66.0% and 70.0%, respectively. The ESRS combined with the degree of enhancement predicted stroke recurrence with an AUC = 0.685 (95CI% 0.633–0.734), while the recorded sensitivity and specificity were 56.6% and 73.4%, respectively. The ESRS combined with hyperintensity on the T1WI predicted stroke recurrence with an AUC = 0.745 (95CI% 0.696–0.791). The recorded sensitivity and specificity were 64.2% and 76.8%, respectively. The AUC quality of the ESRS combined with hyperintensity on T1WI was higher than that of other indices (P < 0.05).ConclusionsThe hyperintensity on T1WI of the culprit plaque in intracranial arteries combined with ESRS demonstrated better predictive ability for short-term stroke recurrence. We consider this of high importance for clinical application since it provides an easier way of obtaining data for precise diagnosis.     

Semi-quantitative electromyography as a predictor of nerve transfer outcome

ObjectivesEvaluate correlation between donor nerve semi-quantitative electromyography (sqEMG) and strength outcome in nerve transfer surgery.MethodsRetrospective review of pre-operative donor nerve semi-quantitative neurophysiology and post-operative recipient muscle force after at least one-year follow-up. The semi-quantitative technique is the average motor unit number estimate associated with needle recorded interference patterns in the donor muscle (IP-AMUNE), which was correlated with hand-held manometry, standardized as a percent of the contralateral arm, using multivariable linear regression with backward selection.ResultsTwenty-eight nerve transfer cases were included. The correlation between the donor nerve IP-AMUNE and the recipient muscle strength was moderate to strong and highly significant (r = 0.67, p < 0.001). Medical Research Council (MRC) grading did not predict strength (p > 0.54).ConclusionsIP-AMUNE is a good predictor of strength after nerve transfer surgery and should be considered in the evaluation and planning of patients undergoing nerve transfer to aid in donor nerve selection.SignificanceIP-AMUNE may significantly benefit those undergoing nerve transfer surgery for the restoration of movement.     

Individual localization value of resting-state fMRI in epilepsy presurgical evaluation: A combined study with stereo-EEG

ObjectiveTo examine the individual-patient-level localization value of resting-state functional MRI (rsfMRI) metrics for the seizure onset zone (SOZ) defined by stereo-electroencephalography (SEEG) in patients with medically intractable focal epilepsies.MethodsWe retrospectively included 19 patients who underwent SEEG implantation for epilepsy presurgical evaluation. Voxel-wise whole-brain analysis was performed on 3.0 T rsfMRI to generate clusters for amplitude of low-frequency fluctuations (ALFF), regional homogeneity (ReHo) and degree centrality (DC), which were co-registered with the SEEG-defined SOZ to evaluate their spatial overlap. Subgroup and correlation analyses were conducted for various clinical characteristics.ResultsALFF demonstrated concordant clusters with SEEG-defined SOZ in 73.7% of patients, with 93.3% sensitivity and 77.8% PPV. The concordance rate showed no significant difference when subgrouped by lesional/non-lesional MRI, SOZ location, interictal epileptiform discharges on scalp EEG, pathology or seizure outcomes. No significant correlation was seen between ALFF concordance rate and epilepsy duration, seizure-onset age, seizure frequency or number of antiseizure medications. ReHo and DC did not achieve favorable concordance results (10.5% and 15.8%, respectively). All concordant clusters showed regional activation, representing increased neural activities.ConclusionALFF had high concordance rate with SEEG-defined SOZ at individual-patient level.SignificanceALFF activation on rsfMRI can add localizing information for the noninvasive presurgical workup of intractable focal epilepsies.     

Dynamic functional connectivity of the EEG in relation to outcome of postanoxic coma

ObjectiveEarly EEG contains reliable information for outcome prediction of comatose patients after cardiac arrest. We introduce dynamic functional connectivity measures and estimate additional predictive values.MethodsWe performed a prospective multicenter cohort study on continuous EEG for outcome prediction of comatose patients after cardiac arrest. We calculated Link Rates (LR) and Link Durations (LD) in the α, δ, and θ band, based on similarity of instantaneous frequencies in five-minute EEG epochs, hourly, during 3 days after cardiac arrest. We studied associations of LR and LD with good (Cerebral Performance Category (CPC) 1–2) or poor outcome (CPC 3–5) with univariate analyses. With random forest classification, we established EEG-based predictive models. We used receiver operating characteristics to estimate additional values of dynamic connectivity measures for outcome prediction.ResultsOf 683 patients, 369 (54%) had poor outcome. Patients with poor outcome had significantly lower LR and longer LD, with largest differences 12 h after cardiac arrest (LR_θ 1.87 vs. 1.95 Hz and LD_α 91 vs. 82 ms). Adding these measures to a model with classical EEG features increased sensitivity for reliable prediction of poor outcome from 34% to 38% at 12 h after cardiac arrest.ConclusionPoor outcome is associated with lower dynamics of connectivity after cardiac arrest.SignificanceDynamic functional connectivity analysis may improve EEG based outcome prediction.     

In pursuit of a sensitive EEG functional connectivity outcome measure for clinical trials in Alzheimer’s disease

ObjectiveIn clinical trials in Alzheimer’s Disease (AD), an improvement of impaired functional connectivity (FC) could provide biological support for the potential efficacy of the drug. Electroencephalography (EEG) analysis of the SAPHIR-trial showed a treatment induced improvement of global relative theta power but not of FC measured by the phase lag index (PLI). We compared the PLI with the amplitude envelope correlation with leakage correction (AEC-c), a presumably more sensitive FC measure.MethodsPatients with early AD underwent 12 weeks of placebo or treatment with PQ912, a glutaminylcyclase inhibitor. Eyes-closed task free EEG was measured at baseline and follow-up (PQ912 n = 47, placebo n = 56). AEC-c and PLI were measured in multiple frequency bands. Change in FC was compared between treatment groups by using two models of covariates.ResultsA significant increase in global AEC-c in the alpha frequency band was found with PQ912 treatment compared to placebo (p = 0.004, Cohen’s d = 0.58). The effect remained significant when corrected for sex, country, ApoE ε4 carriage, age, baseline value (model 1; p = 0.006) and change in relative alpha power (model 2; p = 0.004).ConclusionsFunctional connectivity in early AD, measured with AEC-c in the alpha frequency band, improved after PQ912 treatment.SignificanceAEC-c may be a robust and sensitive FC measure for detecting treatment effects.     

Median somatosensory evoked potential as a predictor of clinical outcome after urgent surgical extracranial internal carotid artery recanalization

ObjectiveChanges in the N20/P25 amplitude of somatosensory evoked potentials (SEP) of the median nerve have been found to correlate with those in cortical regional cerebral blood flow (rCBF). Our study presents the use of median nerve SEP amplitude in predicting the clinical outcome of urgent surgical internal carotid artery (ICA) recanalization.MethodsA total of 27 patients suffering an acute ischemic stroke (AIS) with extracranial ICA occlusion within 24 h were prospectively recruited. The primary preoperative endpoints included the SEP amplitude absolute value (SEP-amp) and the SEP amplitude side-to-side ratio (SEP-ratio).Clinical outcome at 3 months postoperatively was assessed using the modified Rankin scale (mRS-3M).ResultsThe positive predictive values (PPVs) for SEP-amp and SEP-ratio were 95.5% and 100%, respectively, with the negative predictive values (NPVs) being 60.0% and 100%, respectively. The SEP-ratio correlated fully with mRS-3M.ConclusionThe median SEP side-to-side N20/P25 amplitude ratio seems to be a very strong positive and negative predictor of the clinical outcome of urgent recanalization of an extracranial ICA occlusion.SignificanceThe results suggest that cortical evoked activity may help in selection patient for surgical recanalization and predict clinical recovery after an acute ischemic stroke.