Gamma amplitude is coupled to opposed hippocampal theta-phase states during the encoding and retrieval of episodic memories in humans

Computational models and in vivo studies in rodents suggest that the emergence of gamma activity (40-140 Hz) during memory encoding and retrieval is coupled to opposed-phase states of the underlying hippocampal theta rhythm (4-9 Hz).^{1,2,3,4,5,6,7,8,9,10} However, direct evidence for whether human hippocampal gamma-modulated oscillatory activity in memory processes is coupled to opposed-phase states of the ongoing theta rhythm remains elusive. Here, we recorded local field potentials (LFPs) directly from the hippocampus of 10 patients with epilepsy, using depth electrodes. We used a memory encoding and retrieval task whereby trial unique sequences of pictures depicting real-life episodes were presented, and 24 h later, participants were asked to recall them upon the appearance of the first picture of the encoded episodic sequence. We found theta-to-gamma cross-frequency coupling that was specific to the hippocampus during both the encoding and retrieval of episodic memories. We also revealed that gamma was coupled to opposing theta phases during both encoding and recall processes. Additionally, we observed that the degree of theta-gamma phase opposition between encoding and recall was associated with participants' memory performance, so gamma power was modulated by theta phase for both remembered and forgotten trials, although only for remembered trials the dominant theta phase was different for encoding and recall trials. The current results offer direct empirical evidence in support of hippocampal theta-gamma phase opposition models in human long-term memory and provide fundamental insights into mechanistic predictions derived from computational and animal work, thereby contributing to establishing similarities and differences across species.

Influence of personality profile in patients with drug-resistant epilepsy on quality of life following surgical treatment: A 1-year follow-up study

The objectives of this study are to determine the influence of personality profile in patients with drug-resistant epilepsy on quality of life (QoL) after surgical treatment and compare the results with a non-surgical control group at the 1-year follow-up. We conducted a prospective, comparative, controlled study, including 70 patients suffering from drug-resistant epilepsy. Demographic, psychiatric, neurological, and psychological data were recorded at the baseline and at the 1-year follow-up. Assessment of personality dimensions was performed using the NEO-FFI-R questionnaire; severity of anxiety and depression were assessed by the Hospital Anxiety and Depression Scale (HADS), and QoL was evaluated using the QOLIE-31. At the 1-year follow-up, comparing the control and the surgical groups, we detected differences in scores of most items of QoL, which were higher in those patients who had undergone surgery. High levels of Conscientiousness and Openness to experience at the baseline in patients who underwent surgery predicted better post-surgical outcomes in the QoL scores, whereas high neurotic patients showed worse QoL results. Postoperative changes in QoL in patients were associated with the personality profile at the baseline. QoL measures significantly improved in the surgical group compared with the non-surgical group but were not associated with baseline or postoperative seizure frequency at 1 year.

Interpretable surface-based detection of focal cortical dysplasias: a Multi-centre Epilepsy Lesion Detection study

One outstanding challenge for machine learning in diagnostic biomedical imaging is algorithm interpretability. A key application is the identification of subtle epileptogenic focal cortical dysplasias (FCDs) from structural MRI. FCDs are difficult to visualize on structural MRI but are often amenable to surgical resection. We aimed to develop an open-source, interpretable, surface-based machine-learning algorithm to automatically identify FCDs on heterogeneous structural MRI data from epilepsy surgery centres worldwide. The Multi-centre Epilepsy Lesion Detection (MELD) Project collated and harmonized a retrospective MRI cohort of 1015 participants, 618 patients with focal FCD-related epilepsy and 397 controls, from 22 epilepsy centres worldwide. We created a neural network for FCD detection based on 33 surface-based features. The network was trained and cross-validated on 50% of the total cohort and tested on the remaining 50% as well as on 2 independent test sites. Multidimensional feature analysis and integrated gradient saliencies were used to interrogate network performance. Our pipeline outputs individual patient reports, which identify the location of predicted lesions, alongside their imaging features and relative saliency to the classifier. On a restricted 'gold-standard' subcohort of seizure-free patients with FCD type IIB who had T1 and fluid-attenuated inversion recovery MRI data, the MELD FCD surface-based algorithm had a sensitivity of 85%. Across the entire withheld test cohort the sensitivity was 59% and specificity was 54%. After including a border zone around lesions, to account for uncertainty around the borders of manually delineated lesion masks, the sensitivity was 67%. This multicentre, multinational study with open access protocols and code has developed a robust and interpretable machine-learning algorithm for automated detection of focal cortical dysplasias, giving physicians greater confidence in the identification of subtle MRI lesions in individuals with epilepsy.

Testing an Adapted Auditory Verbal Learning Test Paradigm for fMRI to Lateralize Verbal Memory in Patients with Epilepsy

BACKGROUND AND PURPOSE

fMRI is a noninvasive tool for predicting postsurgical deficits in candidates with pharmacoresistant temporal lobe epilepsy. We aimed to test an adapted paradigm of the Rey Auditory Verbal Learning Test to evaluate differences in memory laterality indexes between patients and healthy controls and its association with neuropsychological scores.

MATERIALS AND METHODS

We performed a prospective study of 50 patients with temporal lobe epilepsy and 22 healthy controls. Participants underwent a block design language and memory fMRI. Laterality indexes and the hippocampal anterior-posterior index were calculated. Language and memory lateralization was organized into typical and atypical on the basis of laterality indexes. A neuropsychological assessment was performed with a median time from fMRI of 8 months and was compared with fMRI performance.

RESULTS

We studied 40 patients with left temporal lobe epilepsy and 10 with right temporal lobe epilepsy. Typical language occurred in 65.3% of patients and 90.9% of healthy controls (P = .04). The memory fMRI laterality index was obtained in all healthy controls and 92% of patients. The verbal memory laterality index was bilateral (24.3%) more frequently than the language laterality index (7.69%) in patients with left temporal lobe epilepsy. Atypical verbal memory was greater in patients with left temporal lobe epilepsy (56.8%) than in healthy controls (36.4%), and the proportion of bilateral laterality indexes (53.3%) was larger than right laterality indexes (46.7%). Atypical verbal memory might be associated with higher cognitive scores in patients. No relevant differences were seen in the hippocampal anterior-posterior index according to memory impairment.

CONCLUSIONS

The adapted Rey Auditory Verbal Learning Test paradigm fMRI might support verbal memory lateralization. Temporal lobe epilepsy laterality influences hippocampal memory laterality indexes. Left temporal lobe epilepsy has shown a higher proportion of atypical verbal memory compared with language, potentially to memory functional reorganization.

Personality changes in patients suffering from drug-resistant epilepsy after surgical treatment: a 1-year follow-up study

OBJECTIVE

To determine changes in dimensions of personality in a sample of patients suffering from drug-resistant epilepsy at the 1-year follow-up following surgery, compared to non-surgically treated controls.

METHODS

We conducted a prospective comparative controlled study, including drug-resistant epilepsy surgery candidates. Demographic, psychiatric, neurological, and psychological data were recorded. Presurgical and 12-months follow-up evaluations were performed. Personality dimensions were measured by the NEO Five-Factor Inventory, Revised version (NEO-FFI-R), anxiety and depression symptoms were assessed by the Hospital Anxiety and Depression Scale (HADS: HADA-Anxiety and HADD-Depression), psychiatric evaluations were performed using the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) Axis-I disorders classification. Statistical analysis consisted of comparative tests, correlation analysis, and the stepwise multiple regression test (ANOVA).

RESULTS

A 1-year follow-up was completed by 70 out of 80 patients. Through the study, the surgical group decreased in neuroticism and increased in agreeableness. The controls increased in consciousness, and these changes were predicted by the earlier age of epilepsy onset and lesser score in HADD at the baseline. No personality changes were associated with seizure frequency. The presurgical evaluation concluded that both groups had no differences in demographic, psychiatric, or neurological variables with the only exception being for the number of seizures per month, which was higher in the surgical group. Psychiatric comorbidity in patients was associated with their higher degree of neuroticism and agreeableness at the baseline. Comparing control and surgical groups at the one-year follow-up, the agreeableness personality variable was higher in the surgical group, and as expected, HADS scores were higher in the control group, and seizure frequency was also higher in the control group.

SIGNIFICANCE

Higher agreeableness was the most relevant difference in personality dimensions in patients who underwent surgical treatment compared with the non-surgical treatment group. After surgery patients decreased in neuroticism and increased in agreeableness scores.

Volumetric and shape analysis of the hippocampus in temporal lobe epilepsy with GAD65 antibodies compared with non-immune epilepsy

Glutamic acid decarboxylase 65 antibodies (anti-GAD65) have been found in patients with late-onset chronic temporal lobe epilepsy (TLE). No prior neuroimaging studies have addressed how they affect hippocampal volume and shape and how they relate to cognitive abnormalities. We aimed to investigate both brain structure and function in patients with isolated TLE and high anti-GAD65 levels (RIA ≥ 2000 U/ml) compared to 8 non-immune mesial TLE (niTLE) and 8 healthy controls (HC). Hippocampal subfield volume properties were correlated with the duration of the disease and cognitive test scores. The affected hippocampus of GAD-TLE patients showed no volume changes to matched HC whereas niTLE volumes were significantly smaller. Epilepsy duration in GAD-TLE patients correlated negatively with volumes in the presubiculum, subiculum, CA1, CA2-3, CA4, molecular layer and granule cell-molecular layer of the dentate nucleus. We found differences by advanced vertex-wise shape analysis in the anterior hippocampus of the left GAD-TLE compared to HC whereas left niTLE showed bilateral posterior hippocampus deformation. Verbal deficits were similar in GAD-TLE and niTLE but did not correlate to volume changes. These data might suggest a distinct expression of hippocampal structural and functional abnormalities based on the immune response.

Psychiatric disorders in patients with resistant temporal lobe epilepsy two years after undergoing elective surgery. A longitudinal study

PURPOSE

Psychiatric morbidity in temporal lobe epilepsy (TLE) is frequent and negatively affects patients' life quality. Surgery is the procedure of choice when treating seizures, although the effects on psychiatric disorders remain unclear. We evaluate the effect of surgery on psychiatric disorders in patients with TLE two years after the intervention, to then shed light on how these are related to anxiety and depression symptoms, and Interictal Dysphoric Disorder (IDD).

METHODS

We included data from 65 patients with TLE whose psychiatric evaluations were performed according to DSM-IV criteria. Anxiety and depression symptoms were assessed using the Hospital Anxiety and Depression Scale (HADS) test.

RESULTS

At 2-year follow-up, anxiety and depressive disorders decreased, and psychotic disorders augmented without statistical significance. Baseline psychiatric disorders predisposed to psychiatric pathology at 2-year follow-up and did not correlate with epilepsy outcome after surgery. Postoperative psychiatric disorders correlated with the seizure incidence two years after the intervention, suggesting that epilepsy and psychiatric disorders were associated in processes such as surgery. De novo psychiatric disorders represented 52% of postoperative psychiatric pathology, 62% being psychotic disorders. De novo psychiatric disorders became more frequent from the first year of surgery, occurring mainly in patients free of seizures. The HADS test scores and IDD correlated with psychiatric disorders at 2-year follow-up.

CONCLUSIONS

Baseline psychiatric disorders did not influence surgery outcome, but correlated with psychiatric disorders' prevalence two years after surgery. Despite not finding statistical significance, surgery reduced the prevalence of psychiatric disorders, and de novo psychiatric disorders were associated with an improvement in the epilepsy course at 2-year follow-up.

Psychotic symptoms in drug resistant epilepsy patients after cortical stimulation

PURPOSE

The use of invasive EEG (iEEG) recordings before epilepsy surgery has increased as more complex focal epilepsies are evaluated. Psychotic symptoms (PS) during iEEG have been scarcely reviewed. We aim to report our series of patients with psychotic symptoms (PS) brought about by cortical stimulation (CS) and to identify triggers.

METHODS

Retrospective cohort of patients who underwent iEEG and CS. We report patients who developed delusional thinking and/or disorganized behaviour within 24 h after CS. Exclusion criteria were primary psychiatric disorders or absence of CS.

RESULTS

We evaluated 32 (SEEG 23; subdural 9) patients with a median age of 38 years, 6 with PS. Patients underwent 2586 stimulations over 1130 contacts. Age at CS was significantly higher in patients with PS. Temporal lobe epilepsy was significantly more often documented in patients with PS (χ²: 3.94; p< 0.05). We found no correlation between stimulation of the limbic system and development of psychosis. Four (66.7 %) patients were stimulated in the non-dominant limbic system and developed psychosis compared to 7 (27 %) who did not [χ2: 3.41; p= 0.06].Epilepsy duration was significantly higher in PS patients (p=0.002). Patients with history of postictal psychosis were twice more likely to experience PS(p=0.04).

CONCLUSIONS

PS may arise more frequently in patients with PIP history, older age and longer epilepsy duration. The neurobiology and physiology of psychosis, that may share common mechanisms with epilepsy, is yet to be identified but we hypothesize that it may be triggered by CS due to alteration of brain networks dynamics.

The emerging role of the advanced practice epilepsy nurse: A comparative study between two countries

AIMS AND OBJECTIVES

The aim of the study was to compare advanced practice in epilepsy nurses in Spain and United Kingdom, identifying differences in the domains of standard advanced practice.

BACKGROUND

Europe has recently faced the challenge of providing high-quality care for patients with epilepsy, a disease that generates many health demands. In some countries, such as the United Kingdom, advanced practice nursing is well established and could serve as a guide for implantation in countries where it is still in development, as is the case of Spain.

DESIGN

A multicentre cross-sectional descriptive cohort study compared differences in the roles of advanced practice nurses in Spain and the United Kingdom.

METHODS

The Advanced Practice Role Delineation Tool and its validated Spanish version were administered using an online questionnaire in a cohort of advanced practice epilepsy nurses in both countries. A convenience sample was recruited between January to December 2019. The study complied with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist.

RESULTS

Most United Kingdom nurses in our sample came from community environments, in contrast to Spanish nurses who worked in hospital. All domains analysed in the survey had significantly higher scores in the United Kingdom than in the Spanish cohort, especially in the research and leadership domains.

CONCLUSIONS

The advanced practice role in Spain is underdeveloped compared with the United Kingdom. Differences in the settings of advanced roles in epilepsy nurses may be explained by greater community practice in the United Kingdom and differences in organisational and health systems.

RELEVANCE TO CLINICAL PRACTICE

Our study showed the need to implement specific policies to develop advance practice nurse roles in Spain to improve the quality of care of patients with epilepsy.

Emergency implementation of telemedicine for epilepsy in Spain: Results of a survey during SARS-CoV-2 pandemic

Teleneurology in Spain had not been implemented so far in clinical practice, except in urgent patients with stroke. Telemedicine was hardly used in epilepsy, and patients and neurologists usually preferred onsite visits. Our goal was to study impressions of adult and pediatric epileptologists about the use of telemedicine after emergent implementation during the new coronavirus 2019 (COVID-19) pandemic.

METHODS

An online survey was sent to the members of the Spanish Epilepsy Society and the members of the Epilepsy Study Group of the Catalan Neurological Society, inquiring about different aspects of telemedicine in epilepsy during the pandemic lockdown.

RESULTS

A total of 66 neurologists responded, mostly adult neurologists (80.3%), the majority with a monographic epilepsy clinic (4 out of 5). Of all respondents, 59.1% reported to attend more than 20 patients with epilepsy (PWE) a week. During the pandemic, respondents handled their epilepsy clinics mainly with telephone calls (88%); only 4.5% used videoconference. Changes in antiseizure medications were performed less frequently than during onsite visits by 66.6% of the epileptologists. Scales were not administered during these visits, and certain types of information such as sudden expected unrelated death in epilepsy (SUDEP) were felt to be more appropriate to discuss in person. More than 4 out of 5 of the neurologists (84.8%) stated that they would be open to perform some telematic visits in the future.

CONCLUSIONS

In Spain, emergent implantation of teleneurology has shown to be appropriate for the care of many PWE. Technical improvements, extended use of videoconference and patient selection may improve results and patient and physician satisfaction.

External trigeminal nerve stimulation for drug resistant epilepsy: A randomized controlled trial

BACKGROUND

External trigeminal nerve stimulation (ETNS) is an emergent, non-invasive neurostimulation therapy delivered bilaterally with adhesive skin electrodes. In previous studies, ETNS was associated to a decrease in seizure frequency in patients with focal drug-resistant epilepsy (DRE).

OBJECTIVE

To determine the long-term efficacy and tolerability of ETNS in patients with focal DRE. Moreover, to explore whether its efficacy depends on the epileptogenic zone (frontal or temporal), and its impact on mood, cognitive function, quality of life, and trigeminal nerve excitability.

METHODS

Forty consecutive patients with frontal or temporal DRE, unsuitable for surgery, were randomized to ETNS or usual medical treatment. Participants were evaluated at 3, 6 and 12 months for efficacy, side effects, mood scales, neuropsychological tests and trigeminal nerve excitability.

RESULTS

Subjects had a median of 15 seizures per month and had tried a median of 12.5 antiepileptic drugs. At 12 months, percentage of responders was 50% in ETNS group and 0% in control group. Seizure frequency in ETNS group decreased by -43.5% from baseline. Temporal epilepsy subgroup responded better than frontal epilepsy subgroup (55.56% vs. 45.45%, respectively). Median stimulation intensity was 6.2 mA. ETNS improved quality of life, but not anxiety or depression. Long-term ETNS affected neither neuropsychological function, nor trigeminal nerve excitability. No relevant adverse events were observed.

CONCLUSIONS

ETNS is an effective and well-tolerated therapy for focal DRE. Patients with temporal epilepsy showed a better response than those with frontal epilepsy. Future studies with larger populations may define its role compared to other neurostimulation techniques.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that ETNS reduces seizure frequency in patients with focal DRE.

Spanish version of the Satisfaction with Epilepsy Care questionnaire: Adaptation and psychometric properties

OBJECTIVE

The objective of this study was to perform a cross-cultural adaption and psychometric evaluation of the Spanish version of the Satisfaction with Epilepsy Care (SEC) questionnaire and analyze patient satisfaction with epilepsy care.

METHODS

Transcultural adaptation and validation of the SEC were carried out using translation and back-translation with pilot testing and an expert panel. The SEC-E (Spanish) was analyzed in 213 patients with epilepsy to examine construct and criterion validity and internal consistency.

RESULTS

The SEC-E achieved conceptual, semantic, and content equivalence with the original version. For content validity, one question was eliminated from the original questionnaire as it has little relevance in our cultural setting. Positive correlations for criterion validity were obtained using the gold standard measure (Satisfaction in Hospitalized Patients scale). Construct validity replicated the three dimensions of the original questionnaire. The scale showed adequate reliability through internal consistency (Cronbach's α of 0.94) and temporal stability on retest (n = 85). Patients scored (0 to 100) 77.5 [standard deviation (SD): 19.9] for satisfaction with communication, 76.9 (SD: 17) for organization, and 67.2 (SD: 22.1) for information.

SIGNIFICANCE

The SEC-E is a valid and reliable tool for the assessment of educational interventions aiming to improve the quality of care in patients with epilepsy in Spanish clinical practice. The results showed a good level of patient satisfaction with epilepsy care.