Functional and anatomical connectivity predict brain stimulation's mnemonic effects.

Closed-loop direct brain stimulation is a promising tool for modulating neural activity and behavior. However, it remains unclear how to optimally target stimulation to modulate brain activity in particular brain networks that underlie particular cognitive functions. Here, we test the hypothesis that stimulation's behavioral and physiological effects depend on the stimulation target's anatomical and functional network properties. We delivered closed-loop stimulation as 47 neurosurgical patients studied and recalled word lists. Multivariate classifiers, trained to predict momentary lapses in memory function, triggered the stimulation of the lateral temporal cortex (LTC) during the study phase of the task. We found that LTC stimulation specifically improved memory when delivered to targets near white matter pathways. Memory improvement was largest for targets near white matter that also showed high functional connectivity to the brain's memory network. These targets also reduced low-frequency activity in this network, an established marker of successful memory encoding. These data reveal how anatomical and functional networks mediate stimulation's behavioral and physiological effects, provide further evidence that closed-loop LTC stimulation can improve episodic memory, and suggest a method for optimizing neuromodulation through improved stimulation targeting.

A Learned Map for Places and Concepts in the Human Medial Temporal Lobe.

Distinct lines of research in both humans and animals point to a specific role of the hippocampus in both spatial and episodic memory function. The discovery of concept cells in the hippocampus and surrounding medial temporal lobe (MTL) regions suggests that the MTL maps physical and semantic spaces with a similar neural architecture. Here, we studied the emergence of such maps using MTL microwire recordings from 20 patients (9 female, 11 male) navigating a virtual environment featuring salient landmarks with established semantic meaning. We present several key findings. The array of local field potentials in the MTL contains sufficient information for above-chance decoding of subjects' instantaneous location in the environment. Closer examination revealed that as subjects gain experience with the environment the field potentials come to represent both the subjects' locations in virtual space and in high-dimensional semantic space. Similarly, we observe a learning effect on temporal sequence coding. Over time, field potentials come to represent future locations, even after controlling for spatial proximity. This predictive coding of future states, more so than the strength of spatial representations per se, is linked to variability in subjects' navigation performance. Our results thus support the conceptualization of the MTL as a memory space, representing both spatial- and nonspatial information to plan future actions and predict their outcomes.SIGNIFICANCE STATEMENT Using rare microwire recordings, we studied the representation of spatial, semantic, and temporal information in the human MTL. Our findings demonstrate that subjects acquire a cognitive map that simultaneously represents the spatial and semantic relations between landmarks. We further show that the same learned representation is used to predict future states, implicating MTL cell assemblies as the building blocks of prospective memory functions.

Edge-wise analysis reveals white matter connectivity associated with focal to bilateral tonic-clonic seizures.

OBJECTIVE: Focal to bilateral tonic-clonic seizures (FBTCS) represent a challenging subtype of focal temporal lobe epilepsy (TLE) in terms of both severity and treatment response. Most studies have focused on regional brain analysis that is agnostic to the distribution of white matter (WM) pathways associated with a node. We implemented a more selective, edge-wise approach that allowed for identification of the individual connections unique to FBTCS. METHODS: T1-weighted and diffusion-weighted images were obtained from 22 patients with solely focal seizures (FS), 43 FBTCS patients, and 65 age/sex-matched healthy participants (HPs), yielding streamline (STR) connectome matrices. We used diffusion tensor-derived STRs in an edge-wise approach to determine specific structural connectivity changes associated with seizure generalization in FBTCS compared to matched FS and HPs. Graph theory metrics were computed on both node- and edge-based connectivity matrices. RESULTS: Edge-wise analyses demonstrated that all significantly abnormal cross-hemispheric connections belonged to the FBTCS group. Abnormal connections associated with FBTCS were mostly housed in the contralateral hemisphere, with graph metric values generally decreased compared to HPs. In FBTCS, the contralateral amygdala showed selective decreases in the structural connection pathways to the contralateral frontal lobe. Abnormal connections in TLE involved the amygdala, with the ipsilateral side showing increases and the contralateral decreases. All the FS findings indicated higher graph metrics for connections involving the ipsilateral amygdala. Data also showed that some FBTCS connectivity effects are moderated by aging, recent seizure frequency, and longer illness duration. SIGNIFICANCE: Data showed that not all STR pathways are equally affected by the seizure propagation of FBTCS. We demonstrated two key biases, one indicating a large role for the amygdala in the propagation of seizures, the other pointing to the prominent role of cross-hemispheric and contralateral hemisphere connections in FBTCS. We demonstrated topographic reorganization in FBTCS, pointing to the specific WM tracts involved.

Prediction tools and risk stratification in epilepsy surgery.

OBJECTIVE: This study was undertaken to conduct external validation of previously published epilepsy surgery prediction tools using a large independent multicenter dataset and to assess whether these tools can stratify patients for being operated on and for becoming free of disabling seizures (International League Against Epilepsy stage 1 and 2). METHODS: We analyzed a dataset of 1562 patients, not used for tool development. We applied two scales: Epilepsy Surgery Grading Scale (ESGS) and Seizure Freedom Score (SFS); and two versions of Epilepsy Surgery Nomogram (ESN): the original version and the modified version, which included electroencephalographic data. For the ESNs, we used calibration curves and concordance indexes. We stratified the patients into three tiers for assessing the chances of attaining freedom from disabling seizures after surgery: high (ESGS = 1, SFS = 3-4, ESNs > 70%), moderate (ESGS = 2, SFS = 2, ESNs = 40%-70%), and low (ESGS = 2, SFS = 0-1, ESNs < 40%). We compared the three tiers as stratified by these tools, concerning the proportion of patients who were operated on, and for the proportion of patients who became free of disabling seizures. RESULTS: The concordance indexes for the various versions of the nomograms were between .56 and .69. Both scales (ESGS, SFS) and nomograms accurately stratified the patients for becoming free of disabling seizures, with significant differences among the three tiers (p < .05). In addition, ESGS and the modified ESN accurately stratified the patients for having been offered surgery, with significant difference among the three tiers (p < .05). SIGNIFICANCE: ESGS and the modified ESN (at thresholds of 40% and 70%) stratify patients undergoing presurgical evaluation into three tiers, with high, moderate, and low chance for favorable outcome, with significant differences between the groups concerning having surgery and becoming free of disabling seizures. Stratifying patients for epilepsy surgery has the potential to help select the optimal candidates in underprivileged areas and better allocate resources in developed countries.

Pathological neurons generate ripples at the UP-DOWN transition disrupting information transfer.

OBJECTIVE: To confirm and investigate why pathological high-frequency oscillations (pHFOs), including ripples (80-200 Hz) and fast ripples (200-600 Hz), are generated during the UP-DOWN transition of the slow wave and if information transmission mediated by ripple temporal coupling is disrupted in the seizure-onset zone (SOZ). METHODS: We isolated 217 total units from 175.95 intracranial electroencephalography (iEEG) contact-hours of synchronized macro- and microelectrode recordings from 6 patients. Sleep slow oscillation (.1-2 Hz) epochs were identified in the iEEG recording. iEEG HFOs that occurred superimposed on the slow wave were transformed to phasors and adjusted by the phase of maximum firing in nearby units (i.e., maximum UP). We tested whether, in the SOZ, HFOs and associated action potentials (APs) occur more often at the UP-DOWN transition. We also examined ripple temporal correlations using cross-correlograms. RESULTS: At the group level in the SOZ, HFO and HFO-associated AP probability was highest during the UP-DOWN transition of slow wave excitability (p < < .001). In the non-SOZ, HFO and HFO-associated AP was highest during the DOWN-UP transition (p < < .001). At the unit level in the SOZ, 15.6% and 20% of units exhibited more robust firing during ripples (Cohen's d = .11-.83) and fast ripples (d = .36-.90) at the UP-DOWN transition (p < .05 f.d.r. corrected), respectively. By comparison, also in the SOZ, 6.6% (d = .14-.30) and 8.5% (d = .33-.41) of units had significantly less firing during ripples and fast ripples at the UP-DOWN transition, respectively. Additional data shows that ripple and fast ripple temporal correlations, involving global slow waves, between the hippocampus, entorhinal cortex, and parahippocampal gyrus were reduced by >50% in the SOZ compared to the non-SOZ (N = 3). SIGNIFICANCE: The UP-DOWN transition of slow wave excitability facilitates the activation of pathological neurons to generate pHFOs. Ripple temporal correlations across brain regions may be important in memory consolidation and are disrupted in the SOZ, perhaps by pHFO generation.

Which terms should be used to describe medications used in the treatment of seizure disorders? An ILAE position paper.

A variety of terms, such as "antiepileptic," "anticonvulsant," and "antiseizure" have been historically applied to medications for the treatment of seizure disorders. Terminology is important because using terms that do not accurately reflect the action of specific treatments may result in a misunderstanding of their effects and inappropriate use. The present International League Against Epilepsy (ILAE) position paper used a Delphi approach to develop recommendations on English-language terminology applicable to pharmacological agents currently approved for treating seizure disorders. There was consensus that these medications should be collectively named "antiseizure medications". This term accurately reflects their primarily symptomatic effect against seizures and reduces the possibility of health care practitioners, patients, or caregivers having undue expectations or an incorrect understanding of the real action of these medications. The term "antiseizure" to describe these agents does not exclude the possibility of beneficial effects on the course of the disease and comorbidities that result from the downstream effects of seizures, whenever these beneficial effects can be explained solely by the suppression of seizure activity. It is acknowledged that other treatments, mostly under development, can exert direct favorable actions on the underlying disease or its progression, by having "antiepileptogenic" or "disease-modifying" effects. A more-refined terminology to describe precisely these actions needs to be developed.

Quantification of [99Tc]TcO4- in urine by means of anion-exchange chromatography-aerosol desolvation nebulization-inductively coupled plasma-mass spectrometry.

To sensitively determine 99Tc, a new method for internal quantification of its most common and stable species, [99Tc]Tc O 4 - , was developed. Anion-exchange chromatography (IC) was coupled to inductively coupled plasma-mass spectrometry (ICP-MS) and equipped with an aerosol desolvation system to provide enhanced detection power. Due to a lack of commercial Tc standards, an isotope dilution-like approach using a Ru spike and called isobaric dilution analysis (IBDA) was used for internal quantification of 99Tc. This approach required knowledge of the sensitivities of 99Ru and 99Tc in ICP-MS. The latter was determined using an in-house prepared standard manufactured from decayed medical 99mTc-generator eluates. This standard was cleaned and preconcentrated using extraction chromatography with TEVA resin and quantified via total reflection X-ray fluorescence (TXRF) analysis. IC coupled to ICP-MS enabled to separate, detect and quantify [99Tc]Tc O 4 - as most stable Tc species in complex environments, which was demonstrated in a proof of concept. We quantified this species in untreated and undiluted raw urine collected from a patient, who previously underwent scintigraphy with a 99mTc-tracer, and determined a concentration of 19.6 ± 0.5 ng L-1. The developed method has a high utility to characterize a range of Tc-based radiopharmaceuticals, to determine concentrations, purity, and degradation products in complex samples without the need to assess activity parameters of 99(m)Tc.

Direct brain recordings suggest a causal subsequent-memory effect.

Endogenous variation in brain state and stimulus-specific evoked activity can both contribute to successful encoding. Previous studies, however, have not clearly distinguished among these components. We address this question by analysing intracranial EEG recorded from epilepsy patients as they studied and subsequently recalled lists of words. We first trained classifiers to predict recall of either single items or entire lists and found that both classifiers exhibited similar performance. We found that list-level classifier output-a biomarker of successful encoding-tracked item presentation and recall events, despite having no information about the trial structure. Across widespread brain regions, decreased low- and increased high-frequency activity (HFA) marked successful encoding of both items and lists. We found regional differences in the hippocampus and prefrontal cortex, where in the hippocampus HFA correlated more strongly with item recall, whereas, in the prefrontal cortex, HFA correlated more strongly with list performance. Despite subtle differences in item- and list-level features, the similarity in overall classification performance, spectral signatures of successful recall and fluctuations of spectral activity across the encoding period argue for a shared endogenous process that causally impacts the brain's ability to learn new information.

Automated Seizure Detection Based on State-Space Model Identification.

In this study, we developed a machine learning model for automated seizure detection using system identification techniques on EEG recordings. System identification builds mathematical models from a time series signal and uses a small number of parameters to represent the entirety of time domain signal epochs. Such parameters were used as features for the classifiers in our study. We analyzed 69 seizure and 55 non-seizure recordings and an additional 10 continuous recordings from Thomas Jefferson University Hospital, alongside a larger dataset from the CHB-MIT database. By dividing EEGs into epochs (1 s, 2 s, 5 s, and 10 s) and employing fifth-order state-space dynamic systems for feature extraction, we tested various classifiers, with the decision tree and 1 s epochs achieving the highest performance: 96.0% accuracy, 92.7% sensitivity, and 97.6% specificity based on the Jefferson dataset. Moreover, as the epoch length increased, the accuracy dropped to 94.9%, with a decrease in sensitivity to 91.5% and specificity to 96.7%. Accuracy for the CHB-MIT dataset was 94.1%, with 87.6% sensitivity and 97.5% specificity. The subject-specific cases showed improved results, with an average of 98.3% accuracy, 97.4% sensitivity, and 98.4% specificity. The average false detection rate per hour was 0.5 ± 0.28 in the 10 continuous EEG recordings. This study suggests that using a system identification technique, specifically, state-space modeling, combined with machine learning classifiers, such as decision trees, is an effective and efficient approach to automated seizure detection.

Elemental Imaging of Long-term Gadolinium Retention in Rodent Femur.

Background The use of gadolinium-based contrast agents (GBCAs) is linked to gadolinium retention in the skeleton of healthy individuals. The mechanism of gadolinium incorporation into bone tissue is not fully understood and requires spatially resolved analysis to locate the gadolinium. Purpose To compare the quantitative distribution of gadolinium retained over time in rodent femur following the administration of gadodiamide and gadobutrol at three different time points. Materials and Methods In this animal study conducted between May 2018 and April 2020, 108 9-week-old healthy rats were repeatedly injected with either gadodiamide, gadobutrol, or saline solution and were killed 1, 3, or 12 months after the last injection. The femurs of six female and six male rats per each group and time point were collected. Quantitative elemental imaging of gadolinium in longitudinal thin sections was performed on one sample per sex with use of laser ablation inductively coupled plasma mass spectrometry (ICP-MS). Gadolinium concentration was determined with use of ICP-MS on the samples of all animals (six per group). Mann-Whitney U tests were applied on pairwise comparisons to determine potential sex effect and GBCA effect on gadolinium concentrations. Results The highest gadolinium retention was observed in the gadodiamide group (concentration, 97-200 nmol · g-1), exceeding the mean concentration in the gadobutrol group (6.5-17 nmol · g-1). However, the gadolinium distribution pattern was similar for both contrast agents, showing prominent gadolinium retention at endosteal surfaces, in the bone marrow, and in small tissue pores. Gadolinium distribution in cortical bone changed over time, initially showing a thin rim of higher concentration close to the periosteum, which appeared to grow wider and move toward the interior of the femur over 1 year. Conclusion For both gadolinium-based contrast agents, gadolinium retention in rat bone was initially located close to the periosteum and bone cavities and changed with bone remodeling processes. The relevance to long-term storage of gadolinium in humans remains to be determined. © RSNA, 2022 Online supplemental material is available for this article.

Rare Genetic Variation and Outcome of Surgery for Mesial Temporal Lobe Epilepsy.

OBJECTIVE: Genetic factors have long been debated as a cause of failure of surgery for mesial temporal lobe epilepsy (MTLE). We investigated whether rare genetic variation influences seizure outcomes of MTLE surgery. METHODS: We performed an international, multicenter, whole exome sequencing study of patients who underwent surgery for drug-resistant, unilateral MTLE with normal magnetic resonance imaging (MRI) or MRI evidence of hippocampal sclerosis and ≥2-year postsurgical follow-up. Patients with either sustained seizure freedom (favorable outcome) or ongoing uncontrolled seizures since surgery (unfavorable outcome) were included. Exomes of controls without epilepsy were also included. Gene set burden analyses were carried out to identify genes with significant enrichment of rare deleterious variants in patients compared to controls. RESULTS: Nine centers from 3 continents contributed 206 patients operated for drug-resistant unilateral MTLE, of whom 196 (149 with favorable outcome and 47 with unfavorable outcome) were included after stringent quality control. Compared to 8,718 controls, MTLE cases carried a higher burden of ultrarare missense variants in constrained genes that are intolerant to loss-of-function (LoF) variants (odds ratio [OR] = 2.6, 95% confidence interval [CI] = 1.9-3.5, p = 1.3E-09) and in genes encoding voltage-gated cation channels (OR = 2.4, 95% CI = 1.4-3.8, p = 2.7E-04). Proportions of subjects with such variants were comparable between patients with favorable outcome and those with unfavorable outcome, with no significant between-group differences. INTERPRETATION: Rare variation contributes to the genetic architecture of MTLE, but does not appear to have a major role in failure of MTLE surgery. These findings can be incorporated into presurgical decision-making and counseling. ANN NEUROL 2022.

Long-term outcomes of mesial temporal laser interstitial thermal therapy for drug-resistant epilepsy and subsequent surgery for seizure recurrence: a multi-centre cohort study.

BACKGROUND: Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive alternative to surgical resection for drug-resistant mesial temporal lobe epilepsy (mTLE). Reported rates of seizure freedom are variable and long-term durability is largely unproven. Anterior temporal lobectomy (ATL) remains an option for patients with MRgLITT treatment failure. However, the safety and efficacy of this staged strategy is unknown. METHODS: This multicentre, retrospective cohort study included 268 patients consecutively treated with mesial temporal MRgLITT at 11 centres between 2012 and 2018. Seizure outcomes and complications of MRgLITT and any subsequent surgery are reported. Predictive value of preoperative variables for seizure outcome was assessed. RESULTS: Engel I seizure freedom was achieved in 55.8% (149/267) at 1 year, 52.5% (126/240) at 2 years and 49.3% (132/268) at the last follow-up ≥1 year (median 47 months). Engel I or II outcomes were achieved in 74.2% (198/267) at 1 year, 75.0% (180/240) at 2 years and 66.0% (177/268) at the last follow-up. Preoperative focal to bilateral tonic-clonic seizures were independently associated with seizure recurrence. Among patients with seizure recurrence, 14/21 (66.7%) became seizure-free after subsequent ATL and 5/10 (50%) after repeat MRgLITT at last follow-up≥1 year. CONCLUSIONS: MRgLITT is a viable treatment with durable outcomes for patients with drug-resistant mTLE evaluated at a comprehensive epilepsy centre. Although seizure freedom rates were lower than reported with ATL, this series represents the early experience of each centre and a heterogeneous cohort. ATL remains a safe and effective treatment for well-selected patients who fail MRgLITT.

Failure to use new breakthrough treatments for epilepsy.

Despite the approval of ~20 additional antiseizure medications (ASMs) since the 1980s, one-third of epilepsy patients experience seizures despite therapy. Drug-resistant epilepsy (DRE) is associated with cognitive and psychiatric comorbidities, socioeconomic impairment, injuries, and a 9.3-13.4 times higher mortality rate than in seizure-free patients. Improved seizure control can reduce morbidity and mortality. Two new ASMs were launched in the United States in 2020: cenobamate for focal epilepsy in adults and fenfluramine for Dravet syndrome (DS). They offer markedly improved efficacy. Cenobamate achieved 21% seizure freedom with the highest dose and decreased tonic-clonic seizures by 93% during maintenance treatment in a randomized clinical trial (RCT). In long-term, open-label studies, 10%-36% of patients were seizure-free for a median duration of ~30-45 months. Fenfluramine treatment in DS reduced convulsive seizure frequency by 56% over placebo at the highest dose, with 8% of patients free of convulsive seizures, and 25% with only one convulsive seizure over 14 weeks. These results were sustained for up to 3 years in open-label extension studies. Mortality was reduced 5-fold. These results are superior to all other approved ASMs, placing these two drugs among the most effective antiseizure therapies. The adverse event profiles resemble those of other ASMs. Despite greater efficacy and similar toxicity, these medications are infrequently used. Two years after US market entry, < 5% of either adults with focal DRE or patients with DS were treated with either cenobamate or fenfluramine. We believe this is a failure of our medical system, resulting from limited knowledge about these drugs stemming partly from the separation of academia from industry; restrictions to access created by health care payors, hospitals, and regulatory agencies; and insufficient post-launch information about the efficacy and safety of these ASMs.

Sudden unexpected death in epilepsy during cenobamate clinical development.

OBJECTIVE: We assessed mortality, sudden unexpected death in epilepsy (SUDEP), and standardized mortality ratio (SMR) among adults treated with cenobamate during the cenobamate clinical development program. METHODS: We retrospectively analyzed deaths among all adults with uncontrolled focal (focal to bilateral tonic-clonic [FBTC], focal impaired awareness, focal aware) or primary generalized tonic-clonic (PGTC) seizures who received ≥1 dose of adjunctive cenobamate in completed and ongoing phase 2 and 3 clinical studies. In patients with focal seizures from completed studies, median baseline seizure frequencies ranged from 2.8 to 11 seizures per 28 days and median epilepsy duration ranged from 20 to 24 years. Total person-years included all days that a patient received cenobamate during completed studies or up to June 1, 2022, for ongoing studies. All deaths were evaluated by two epileptologists. All-cause mortality and SUDEP rates were expressed per 1000 person-years. RESULTS: A total of 2132 patients (n = 2018 focal epilepsy; n = 114 idiopathic generalized epilepsy) were exposed to cenobamate for 5693 person-years. Approximately 60% of patients with focal seizures and all patients in the PGTC study had tonic-clonic seizures. A total of 23 deaths occurred (all in patients with focal epilepsy), for an all-cause mortality rate of 4.0 per 1000 person-years. Five cases of definite or probable SUDEP were identified, for a rate of .88 per 1000 person-years. Of the 23 overall deaths, 22 patients (96%) had FBTC seizures, and all 5 of the SUDEP patients had a history of FBTC seizures. The duration of exposure to cenobamate for patients with SUDEP ranged from 130 to 620 days. The SMR among cenobamate-treated patients in completed studies (5515 person-years of follow-up) was 1.32 (95% confidence interval [CI] .84-2.0), which was not significantly different from the general population. SIGNIFICANCE: These data suggest that effective long-term medical treatment with cenobamate may reduce excess mortality associated with epilepsy.

Stimulation better targets fast-ripple generating networks in super responders to the responsive neurostimulator system.

How responsive neurostimulation (RNS) decreases seizure frequency is unclear. Stimulation may alter epileptic networks during inter-ictal epochs. Definitions of the epileptic network vary but fast ripples (FRs) may be an important substrate. We, therefore, examined whether stimulation of FR-generating networks differed in RNS super responders and intermediate responders. In 10 patients, with subsequent RNS placement, we detected FRs from stereo-electroencephalography (SEEG) contacts during pre-surgical evaluation. The normalized coordinates of the SEEG contacts were compared with those of the eight RNS contacts, and RNS-stimulated SEEG contacts were defined as those within 1.5 cm3 of the RNS contacts. We compared the post-RNS placement seizure outcome to (1) the ratio of stimulated SEEG contacts in the seizure-onset zone (SOZ stimulation ratio [SR]); (2) the ratio of FR events on stimulated contacts (FR SR); and (3) the global efficiency of the FR temporal correlational network on stimulated contacts (FR SGe). We found that the SOZ SR (p = .18) and FR SR (p = .06) did not differ in the RNS super responders and intermediate responders, but the FR SGe did (p = .02). In super responders, highly active desynchronous sites of the FR network were stimulated. RNS that better targets FR networks, as compared to the SOZ, may reduce epileptogenicity more.

Time cells in the human hippocampus and entorhinal cortex support episodic memory.

The organization of temporal information is critical for the encoding and retrieval of episodic memories. In the rodent hippocampus and entorhinal cortex, evidence accumulated over the last decade suggests that populations of "time cells" in the hippocampus encode temporal information. We identify time cells in humans using intracranial microelectrode recordings obtained from 27 human epilepsy patients who performed an episodic memory task. We show that time cell activity predicts the temporal organization of retrieved memory items. We also uncover evidence of ramping cell activity in humans, which represents a complementary type of temporal information. These findings establish a cellular mechanism for the representation of temporal information in the human brain needed to form episodic memories.

Delta oscillation coupled propagating fast ripples precede epileptiform discharges in patients with focal epilepsy.

Epileptiform spikes are used to localize epileptogenic brain tissue. The mechanisms that spontaneously trigger epileptiform discharges are not yet elucidated. Pathological fast ripple (FR, 200-600 Hz) are biomarkers of epileptogenic brain, and we postulated that FR network interactions are involved in generating epileptiform spikes. Using macroelectrode stereo intracranial EEG (iEEG) recordings from a cohort of 46 patients we found that, in the seizure onset zone (SOZ), propagating FR were more often followed by an epileptiform spike, as compared with non-propagating FR (p < 0.05). Propagating FR had a distinct frequency and larger power (p < 1e-10) and were more strongly phase coupled to the peak of iEEG delta oscillation, which likely correspond with the DOWN states during non-REM sleep (p < 1e-8), than non-propagating FR. While FR propagation was rare, all FR occurred with the highest probability within +/- 400 msec of epileptiform spikes with superimposed high-frequency oscillations (p < 0.05). Thus, a sub-population of epileptiform spikes in the SOZ, are preceded by propagating FR that are coordinated by the DOWN state during non-REM sleep.

Long-term Gadolinium Retention in the Healthy Rat Brain: Comparison between Gadopiclenol, Gadobutrol, and Gadodiamide.

Background Safety concerns caused by gadolinium retention call for the development of high-relaxivity gadolinium-based contrast agents (GBCAs) allowing minimal dosing. Purpose To investigate brain gadolinium retention in healthy rats after exposure to gadopiclenol (Elucirem, Guerbet; macrocyclic GBCA) compared with gadobutrol (Gadovist or Gadavist, Bayer; macrocyclic GBCA) and gadodiamide (Omniscan, GE Healthcare; linear GBCA) over 1 year. Materials and Methods In this study conducted between May 2018 and April 2020, 9-week-old healthy Sprague Dawley rats received five injections of either gadopiclenol, gadobutrol, or gadodiamide (2.4 mmol of gadolinium per kilogram of body weight for each), or saline (control animals) over a period of 5 weeks. Rats were randomly assigned to different groups (six female and six male rats per group). MRI examinations were performed before euthanasia at 1, 3, 5, or 12 months after the last injection. Brains were sampled to determine the total gadolinium content via inductively coupled plasma mass spectrometry (ICP-MS), to characterize gadolinium species with size exclusion chromatography (SEC)-ICP-MS, and to perform elemental mapping with laser ablation (LA)-ICP-MS. Mann-Whitney tests were performed on pairwise comparisons of the same time points. Results For both macrocyclic agents, no T1 signal hyperintensities were observed in the cerebellum, and approximately 80% of gadolinium washout was found between 1 month (gadobutrol, 0.30 nmol/g; gadopiclenol, 0.37 nmol/g) and 12 months (gadobutrol, 0.062 nmol/g; gadopiclenol, 0.078 nmol/g). After 12 months, only low-molecular-weight gadolinium species were detected in the soluble fraction. Gadodiamide led to significantly higher gadolinium concentrations after 1 month in the cerebellum (gadodiamide, 2.65 nmol/g; P < .001 vs both macrocyclics) combined with only 15% washout after 12 months (gadodiamide, 2.25 nmol/g) and with gadolinium detected bound to macromolecules. Elemental bioimaging enabled visualization of gadolinium deposition patterns colocalized with iron. Conclusion Gadopiclenol and gadobutrol demonstrated similar in vivo distribution and washout of gadolinium in the healthy rat brain, markedly differing from gadodiamide up to 12 months after the last injection. © RSNA, 2022 Online supplemental material is available for this article.

Seizure latency and epilepsy localization as predictors of recurrence following epilepsy surgery.

OBJECTIVE: The primary purpose is to determine whether the time between epilepsy surgery and first seizure recurrence can estimate the timing of the next seizure event for temporal and extratemporal epilepsy. A secondary endpoint aimed to compare temporal and extratemporal epilepsy surgery and examine which subgroup has a higher hazard of subsequent seizure recurrence. METHODS: Data used were from a retrospective database at Thomas Jefferson University Hospital. Records were stratified into temporal (n = 943) and extratemporal (n = 125) surgeries. Analyses were done using SAS and utilized Cox proportional hazards models while controlling for demographics and clinical factors. The primary predictor of time between surgery and first recurrence was treated as a nominal variable binned into six segments, whereas secondary endpoints used a categorical predictor of epilepsy location while controlling for seizure latency. RESULTS: Generally, as seizure latency following surgery increased, the time between first seizure and second seizure increased. These results were statistically meaningful in the temporal set (Wald chi-squared = 40.4715, df = 5, p < .0001). Outcomes could also be interpreted based on predictor group; for instance, if Seizure 1 occurred 1-2 months following surgery in the temporal set, the median number of days until the next seizure was 35.5 days (95% confidence interval [CI] = 21-89 days). Secondary analysis showed that temporal lobe epilepsy had a lower hazard of a second seizure than extratemporal lobe epilepsy (89.2% reduction in hazard; 95% CI = .015-.795). SIGNIFICANCE: This analysis provides a framework to use initial seizure latency to predict the median number of days until the next seizure event, while stratifying based on epilepsy location and controlling for multiple variables. It also suggests that the hazard of seizure recurrence in temporal lobe epilepsy is lower than in extratemporal lobe epilepsy.

Practical considerations in epilepsy neurostimulation.

Neuromodulation is a key therapeutic tool for clinicians managing patients with drug-resistant epilepsy. Multiple devices are available with long-term follow-up and real-world experience. The aim of this review is to give a practical summary of available neuromodulation techniques to guide the selection of modalities, focusing on patient selection for devices, common approaches and techniques for initiation of programming, and outpatient management issues. Vagus nerve stimulation (VNS), deep brain stimulation of the anterior nucleus of the thalamus (DBS-ANT), and responsive neurostimulation (RNS) are all supported by randomized controlled trials that show safety and a significant impact on seizure reduction, as well as a suggestion of reduction in the risk of sudden unexplained death in epilepsy (SUDEP). Significant seizure reductions are observed after 3 months for DBS, RNS, and VNS in randomized controlled trials, and efficacy appears to improve with time out to 7 to 10 years of follow-up for all modalities, albeit in uncontrolled follow-up or retrospective studies. A significant number of patients experience seizure-free intervals of 6 months or more with all three modalities. Number and location of epileptogenic foci are important factors affecting efficacy, and together with comorbidities such as severe mood or sleep disorders, may influence the choice of modality. Programming has evolved-DBS is typically initiated at lower current/voltage than used in the pivotal trial, whereas target charge density is lower with RNS, however generalizable optimal parameters are yet to be defined. Noninvasive brain stimulation is an emerging stimulation modality, although it is currently not used widely. In summary, clinical practice has evolved from those established in pivotal trials. Guidance is now available for clinicians who wish to expand their approach, and choice of neuromodulation technique may be tailored to individual patients based on their epilepsy characteristics, risk tolerance, and preferences.