In this study, we quantified the coverage of gray and white matter during intracranial electroencephalography in a cohort of epilepsy patients with surface and depth electrodes. We included 65 ...patients with strip electrodes (n = 12), strip and grid electrodes (n = 24), strip, grid, and depth electrodes (n = 7), or depth electrodes only (n = 22). Patient-specific imaging was used to generate probabilistic gray and white matter maps and atlas segmentations. Gray and white matter coverage was quantified using spherical volumes centered on electrode centroids, with radii ranging from 1 to 15 mm, along with detailed finite element models of local electric fields. Gray matter coverage was highly dependent on the chosen radius of influence (RoI). Using a 2.5 mm RoI, depth electrodes covered more gray matter than surface electrodes; however, surface electrodes covered more gray matter at RoI larger than 4 mm. White matter coverage and amygdala and hippocampal coverage was greatest for depth electrodes at all RoIs. This study provides the first probabilistic analysis to quantify coverage for different intracranial recording configurations. Depth electrodes offer increased coverage of gray matter over other recording strategies if the desired signals are local, while subdural grids and strips sample more gray matter if the desired signals are diffuse.
Interictal epileptiform discharges (IEDs) are intermittent high-amplitude electrical signals that occur between seizures. They have been shown to propagate through the brain as traveling waves when ...recorded with epicortical grid-type electrodes and small penetrating microelectrode arrays. However, little work has been done to translate experimental IED analyses to more clinically relevant platforms such as stereoelectroencephalography (SEEG). In this pilot study, the authors aimed to define a computational method to identify and characterize IEDs recorded from clinical SEEG electrodes and leverage the directionality of IED traveling waves to localize the seizure onset zone (SOZ).
Continuous SEEG recordings from 15 patients with medically refractory epilepsy were collected, and IEDs were detected by identifying overlapping peaks of a minimum prominence. IED pathways of propagation were defined and compared to the SOZ location determined by a clinical neurologist based on the ictal recordings. For further analysis of the IED pathways of propagation, IED detections were divided into triplets, defined as a set of 3 consecutive contacts within the same IED detection. Univariate and multivariate linear regression models were employed to associate IED characteristics with colocalization to the SOZ.
A median (range) of 22.6 (4.4-183.9) IEDs were detected per hour from 15 patients over a mean of 23.2 hours of recording. Depending on the definition of the SOZ, a median (range) of 20.8% (0.0%-54.5%) to 62.1% (19.2%-99.4%) of IEDs per patient traversed the SOZ. IEDs passing through the SOZ followed discrete pathways that had little overlap with those of the IEDs passing outside the SOZ. Contact triplets that occurred more than once were significantly more likely to be detected in an IED passing through the SOZ (p < 0.001). Per our multivariate model, patients with a greater proportion of IED traveling waves had a significantly greater proportion of IEDs that localized to the SOZ (β = 0.64, 95% CI 0.01-1.27, p = 0.045).
By using computational methods, IEDs can be meaningfully detected from clinical-grade SEEG recordings of patients with epilepsy. In some patients, a high proportion of IEDs are traveling waves according to multiple metrics that colocalize to the SOZ, offering hope that IED detection, with further refinement, could serve as an alternative method for SOZ localization.
In patients with drug-resistant epilepsy, electrical stimulation of the brain in response to epileptiform activity can make seizures less frequent and debilitating. This therapy, known as closed-loop ...responsive neurostimulation (RNS), aims to directly halt seizure activity via targeted stimulation of a burgeoning seizure. Rather than immediately stopping seizures as they start, many RNS implants produce slower, long-lasting changes in brain dynamics that better predict clinical outcomes. Here we hypothesize that stimulation during brain states with less epileptiform activity drives long-term changes that restore healthy brain networks. To test this, we quantified stimulation episodes during low- and high-risk brain states-that is, stimulation during periods with a lower or higher risk of generating epileptiform activity-in a cohort of 40 patients treated with RNS. More frequent stimulation in tonic low-risk states and out of rhythmic high-risk states predicted seizure reduction. Additionally, stimulation events were more likely to be phase-locked to prolonged episodes of abnormal activity for intermediate and poor responders when compared to super-responders, consistent with the hypothesis that improved outcomes are driven by stimulation during low-risk states. These results support the hypothesis that stimulation during low-risk periods might underlie the mechanisms of RNS, suggesting a relationship between temporal patterns of neuromodulation and plasticity that facilitates long-term seizure reduction.
Objective
Responsive neurostimulation is an effective therapy for patients with refractory mesial temporal lobe epilepsy. However, clinical outcomes are variable, few patients become seizure‐free, ...and the optimal stimulation location is currently undefined. The aim of this study was to quantify responsive neurostimulation in the mesial temporal lobe, identify stimulation‐dependent networks associated with seizure reduction, and determine if stimulation location or stimulation‐dependent networks inform outcomes.
Methods
We modeled patient‐specific volumes of tissue activated and created probabilistic stimulation maps of local regions of stimulation across a retrospective cohort of 22 patients with mesial temporal lobe epilepsy. We then mapped the network stimulation effects by seeding tractography from the volume of tissue activated with both patient‐specific and normative diffusion‐weighted imaging. We identified networks associated with seizure reduction across patients using the patient‐specific tractography maps and then predicted seizure reduction across the cohort.
Results
Patient‐specific stimulation‐dependent connectivity was correlated with responsive neurostimulation effectiveness after cross‐validation (p = .03); however, normative connectivity derived from healthy subjects was not (p = .44). Increased connectivity from the volume of tissue activated to the medial prefrontal cortex, cingulate cortex, and precuneus was associated with greater seizure reduction.
Significance
Overall, our results suggest that the therapeutic effect of responsive neurostimulation may be mediated by specific networks connected to the volume of tissue activated. In addition, patient‐specific tractography was required to identify structural networks correlated with outcomes. It is therefore likely that altered connectivity in patients with epilepsy may be associated with the therapeutic effect and that utilizing patient‐specific imaging could be important for future studies. The structural networks identified here may be utilized to target stimulation in the mesial temporal lobe and to improve seizure reduction for patients treated with responsive neurostimulation.
Epitel has developed Epilog, a miniature, wireless, wearable electroencephalography (EEG) sensor. Four Epilog sensors are combined as part of Epitel's Remote EEG Monitoring platform (REMI) to create ...10 channels of EEG for remote patient monitoring. REMI is designed to provide comprehensive spatial EEG recordings that can be administered by non-specialized medical personnel in any medical center. The purpose of this study was to determine how accurate epileptologists are at remotely reviewing Epilog sensor EEG in the 10-channel “REMI montage,” with and without seizure detection support software. Three board certified epileptologists reviewed the REMI montage from 20 subjects who wore four Epilog sensors for up to 5 days alongside traditional video-EEG in the EMU, 10 of whom experienced a total of 24 focal-onset electrographic seizures and 10 of whom experienced no seizures or epileptiform activity. Epileptologists randomly reviewed the same datasets with and without clinical decision support annotations from an automated seizure detection algorithm tuned to be highly sensitive. Blinded consensus review of unannotated Epilog EEG in the REMI montage detected people who were experiencing electrographic seizure activity with 90% sensitivity and 90% specificity. Consensus detection of individual focal onset seizures resulted in a mean sensitivity of 61%, precision of 80%, and false detection rate (FDR) of 0.002 false positives per hour (FP/h) of data. With algorithm seizure detection annotations, the consensus review mean sensitivity improved to 68% with a slight increase in FDR (0.005 FP/h). As seizure detection software, the automated algorithm detected people who were experiencing electrographic seizure activity with 100% sensitivity and 70% specificity, and detected individual focal onset seizures with a mean sensitivity of 90% and mean false alarm rate of 0.087 FP/h. This is the first study showing epileptologists' ability to blindly review EEG from four Epilog sensors in the REMI montage, and the results demonstrate the clinical potential to accurately identify patients experiencing electrographic seizures. Additionally, the automated algorithm shows promise as clinical decision support software to detect discrete electrographic seizures in individual records as accurately as FDA-cleared predicates.
Objectives
Responsive neurostimulation (RNS) is an established therapy for drug‐resistant epilepsy that delivers direct electrical brain stimulation in response to detected epileptiform activity. ...However, despite an overall reduction in seizure frequency, clinical outcomes are variable, and few patients become seizure‐free. The aim of this retrospective study was to evaluate aperiodic electrophysiological activity, associated with excitation/inhibition balance, as a novel electrographic biomarker of seizure reduction to aid early prognostication of the clinical response to RNS.
Methods
We identified patients with intractable mesial temporal lobe epilepsy who were implanted with the RNS System between 2015 and 2021 at the University of Utah. We parameterized the neural power spectra from intracranial RNS System recordings during the first 3 months following implantation into aperiodic and periodic components. We then correlated circadian changes in aperiodic and periodic parameters of baseline neural recordings with seizure reduction at the most recent follow‐up.
Results
Seizure reduction was correlated significantly with a patient's average change in the day/night aperiodic exponent (r = .50, p = .016, n = 23 patients) and oscillatory alpha power (r = .45, p = .042, n = 23 patients) across patients for baseline neural recordings. The aperiodic exponent reached its maximum during nighttime hours (12 a.m. to 6 a.m.) for most responders (i.e., patients with at least a 50% reduction in seizures).
Significance
These findings suggest that circadian modulation of baseline broadband activity is a biomarker of response to RNS early during therapy. This marker has the potential to identify patients who are likely to respond to mesial temporal RNS. Furthermore, we propose that less day/night modulation of the aperiodic exponent may be related to dysfunction in excitation/inhibition balance and its interconnected role in epilepsy, sleep, and memory.
To study generalized paroxysmal fast activity (GPFA) in patients with genetic generalized epilepsy (GGE).
GPFA is an electroencephalographic (EEG) finding in patients with symptomatic generalized ...epilepsy consisting of 15-25Hz bifrontally predominant generalized fast activity seen predominantly in sleep. Historically GPFA is linked to epileptic encephalopathy with drug resistant epilepsy and intellectual disability. However, GPFA has been rarely described as an atypical finding in patients with GGE without negative prognostic implication. We report cognitive profile and seizure characteristics in seven patients with GGE and GPFA.
The Vanderbilt EMU and EEG reports were searched for the keywords “idiopathic generalized epilepsy”, “GPFA”and “generalized spike and wave discharges (GSWD)”. We reviewed the EEG tracings and the electronic medical records of patients thus identified. The seizure type, frequency, neurological work-up, clinical profile and imaging data were recorded.
Awake and sleep states were captured on EEGs of all patients. On EEG tracing review six patients were confirmed to have GSWD and GPFA; one patient had GPFA but no GSWD. All patients had normal cognitive function. Four had a normal brain MRI and one a normal head CT (two were never imaged). None of the patients had tonic seizures. The main seizure type was generalized tonic-clonic seizures (GTCS) in five patients, absence in two. Age at onset of epilepsy ranged from 4 to 24years. The mean GTC seizure frequency at the time of EEG was 3; two patients were seizure free on two antiepileptic drugs (AEDs).
GPFA can be an unrecognized electrographic finding in patients with genetic generalized epilepsy. While GPFA remains an important diagnostic EEG feature for epileptic encephalopathy (Lennox-Gastaut syndrome) it is not specific for this diagnosis. Thus, GPFA may have a spectrum of variable phenotypic expression. The finding of GPFA is not necessarily indicative of unfavorable outcome.
•GPFA has been associated with symptomatic generalized epilepsy and drug-resistant seizures.•We report GPFA in seven patients with idiopathic generalized epilepsy and normal cognition.•GPFA may represent a spectrum of generalized epilepsies with variable phenotypic expression.
Localization value of ictal turning prone Arain, Amir M.; Umar, Azaz; Rawal, Pawan ...
Seizure (London, England),
July 2019, 2019-Jul, 2019-07-00, 20190701, Letnik:
69
Journal Article
Recenzirano
Odprti dostop
•Ictal turning prone (ITP) with rotation along the longitudinal body axis is seen in seizures.•Direction of ITP was uni-directional in 12 patients while 4 patients had ITP in opposite direction in ...different seizures.•ITP does not have a consistent single localizing or lateralizing value.•ITP can be seen with various epileptogenic zones including medial frontal, lateral frontal or temporal.•ITP direction can vary even with a single epileptogenic zone.
Ictal semiology complements ictal EEG in identifying the likely epileptogenic zone. Ictal turning prone (ITP) with body turning of 90 ° or more can be seen with frontal lobe epilepsies. The aim of our study was to evaluate the localizing value of ITP in a general population of patients undergoing long term video-EEG monitoring.
We reviewed our epilepsy monitoring unit database for adult patients with recorded habitual seizures with ITP. All 16 patients identified had continuous video-EEG monitoring using standard scalp electrodes; eight patients also had intracranial EEG monitoring. We only included focal seizures without evolution to bilateral tonic-clonic activity.
We identified 16 patients with ITP, mean age of 32.5 years (range 18–50). ITP was consistently seen in at least one focal impaired awareness seizure of all patients. Ictal onset zone on scalp EEG was left temporal in five, right temporal in three, left frontal convexity in two, right frontal convexity in two, probable right medial frontal in three and probable left medial frontal in one patient. Direction of ITP was uni-directional in 12 patients while 4 patients had ITP in opposite direction in different seizures.
Nine patients underwent epilepsy surgery; five patients had Engel class I outcome and four patients had Engel class III outcome.
Ictal turning prone does not have a consistent single localizing or lateralizing value and can be seen with various epileptogenic zones including medial frontal, lateral frontal or temporal. ITP direction can vary even with a single epileptogenic zone.
PDF
