Learn how to interpret and use intracranial EEG findings.

Epilepsy surgery is the therapy of choice for many patients with drug-resistant focal epilepsy. Recognizing and describing ictal and interictal patterns with intracranial electroencephalography (EEG) recordings is important in order to most efficiently leverage advantages of this technique to accurately delineate the seizure-onset zone before undergoing surgery. In this seminar in epileptology, we address learning objective "1.4.11 Recognize and describe ictal and interictal patterns with intracranial recordings" of the International League against Epilepsy curriculum for epileptologists. We will review principal considerations of the implantation planning, summarize the literature for the most relevant ictal and interictal EEG patterns within and beyond the Berger frequency spectrum, review invasive stimulation for seizure and functional mapping, discuss caveats in the interpretation of intracranial EEG findings, provide an overview on special considerations in children and in subdural grids/strips, and review available quantitative/signal analysis approaches. To be as practically oriented as possible, we will provide a mini atlas of the most frequent EEG patterns, highlight pearls for its not infrequently challenging interpretation, and conclude with two illustrative case examples. This article shall serve as a useful learning resource for trainees in clinical neurophysiology/epileptology by providing a basic understanding on the concepts of invasive intracranial EEG.

Training and teaching of vagus nerve stimulation surgery: Worldwide survey and future perspectives.

OBJECTIVE: Vagus nerve stimulation (VNS) therapy has been used for more than two decades to treat drug resistant epilepsy and depression and most recently received FDA approval for stroke rehabilitation. Expanding indications will renew the interest in the technique and increase the number of surgeons to be trained. The aim of this study was to survey surgeons with substantial expertise on optimal teaching and training approaches. METHODS: Anonymous forms comprising 16 questions were sent by e-mail to surgeons with substantial expertise. Statistical analyses were used to compare the answers of the most experienced surgeons (>5 years) with the less experienced ones (<5 years). RESULTS: Fully-completed forms were collected from 57 experts from 20 countries. The placement of the helical coils was deemed to be the most difficult step by 36 (63.2%) experts, and the use of optical magnification during this step was deemed necessary by 39 (68.4%) experts. Vocal cord palsy should be largely avoidable with proper surgical technique according to 44 (77.2%) experts. The teaching tool considered the most useful was mentoring (38, 66.7%). The future of VNS surgery teaching was deemed to be in anatomical workshops (29, 50.9%) and surgical simulation (26, 45.6%). Overall, answers did not vary significantly according to experience. CONCLUSIONS: VNS surgery should be mastered by actively participating in dedicated practical training courses and by individual mentoring during actual surgery, which is still the best way to learn. This study highlights the need for a formal training course and possible specific accreditation.

Basal temporal lobe epilepsy: SEEG electroclinical characteristics.

OBJECTIVE: Temporal lobe epilepsy is the most common type of focal drug-resistant epilepsy. Seizures with predominant involvement of basal temporal regions (BTR) are not well characterized. In this stereo electroencephalography (SEEG) study, we aimed at describing the ictal networks involving BTR and the associated clinical features. METHODS: We studied 24 patients explored with SEEG in our center with BTR sampling. We analyzed their seizures using a quantitative method: the "epileptogenicity index". Then we reported the features of the patients with maximal epileptogenicity within BTR, especially ictal network involved, ictal semiology and post-surgical outcome. RESULTS: We found that rhinal cortex, parahippocampal cortex and posterior fusiform gyrus were the most epileptogenic structures within the BTR (mean EI: 0.57, 0.55, 0.54 respectively). Three main groups of epileptogenic zone organization were found: anterior (23% of total seizures) posterior (30%) and global (47%, both anterior and posterior). Contralateral spread was found in 35% of left seizures and 20% of right seizures. Naming deficit was more prevalent in left BTR (71% vs 29% in right seizures; p = 0.01) whereas automatic speech production was preferentially represented in right seizures (11% vs 54%; p = 0.001). Surgery was proposed for 11 patients (45.8%), leading to seizure freedom in 72% (Engel Class I). One patient presented post-operative permanent functional deficit. CONCLUSION: Basal-temporal lobe epilepsy seems to be a specific entity among the temporal epilepsy spectrum with specific clinical characteristics. Resective surgery can be proposed with good outcomes in a significant proportion of patients and is safe provided that adequate language assessment has been preoperatively made.

Psychogenic non-epileptic seizures: Chronology of multidisciplinary team approach to diagnosis and management.

While the diagnosis and management of psychogenic non-epileptic seizures (PNES) remain challenging, certain evidence-based guidelines exist, which can help to optimize patient care. A multidisciplinary team approach appears to have many benefits. Current recommendations exist for some aspects of diagnosis and management of PNES, including levels of diagnostic certainty as proposed by the International League Against Epilepsy's expert Task Force on PNES. Other aspects of clinical still care lack clear consensus, including use of suggestion techniques for recording PNES and optimal terminology, since the term "functional seizures" has recently been proposed as a possible term to replace "PNES". The present article aims to (1) review current recommendations and (2) discuss our own team's experience in managing patients with PNES. This is organized chronologically in terms of the roles of the neurologist, psychiatrist and psychologist, and discusses diagnostic issues, psychiatric assessment and treatment, and psychotherapeutic approaches.

Deep brain activities can be detected with magnetoencephalography.

The hippocampus and amygdala are key brain structures of the medial temporal lobe, involved in cognitive and emotional processes as well as pathological states such as epilepsy. Despite their importance, it is still unclear whether their  neural activity can be recorded non-invasively. Here, using simultaneous intracerebral and magnetoencephalography (MEG) recordings in patients with focal drug-resistant epilepsy, we demonstrate a direct contribution of amygdala and hippocampal activity to surface MEG recordings. In particular, a method of blind source separation, independent component analysis, enabled activity arising from large neocortical networks to be disentangled from that of deeper structures, whose amplitude at the surface was small but significant. This finding is highly relevant for our understanding of hippocampal and amygdala brain activity as it implies that their activity could potentially be measured non-invasively.

Electroencephalographic neurofeedback: Level of evidence in mental and brain disorders and suggestions for good clinical practice.

The technique of electroencephalographic neurofeedback (EEG NF) emerged in the 1970s and is a technique that measures a subject's EEG signal, processes it in real time, extracts a parameter of interest and presents this information in visual or auditory form. The goal is to effectuate a behavioural modification by modulating brain activity. The EEG NF opens new therapeutic possibilities in the fields of psychiatry and neurology. However, the development of EEG NF in clinical practice requires (i) a good level of evidence of therapeutic efficacy of this technique, (ii) a good practice guide for this technique. Firstly, this article investigates selected trials with the following criteria: study design with controlled, randomized, and open or blind protocol, primary endpoint related to the mental and brain disorders treated and assessed with standardized measurement tools, identifiable EEG neurophysiological targets, underpinned by pathophysiological relevance. Trials were found for: epilepsies, migraine, stroke, chronic insomnia, attentional-deficit/hyperactivity disorder (ADHD), autism spectrum disorder, major depressive disorder, anxiety disorders, addictive disorders, psychotic disorders. Secondly, this article investigates the principles of neurofeedback therapy in line with learning theory. Different underlying therapeutic models are presented didactically between two continua: a continuum between implicit and explicit learning and a continuum between the biomedical model (centred on "the disease") and integrative biopsychosocial model of health (centred on "the illness"). The main relevant learning model is to link neurofeedback therapy with the field of cognitive remediation techniques. The methodological specificity of neurofeedback is to be guided by biologically relevant neurophysiological parameters. Guidelines for good clinical practice of EEG NF concerning technical issues of electrophysiology and of learning are suggested. These require validation by institutional structures for the clinical practice of EEG NF.

[What the patient's history tells us about their nonepileptic seizures]. / Comment ce que disent les patients peut nous renseigner sur leurs crises non épileptiques psychogènes.

The aetiology of "psychogenic" non-epileptic seizures (NES) remains poorly understood and the differentiation of NES from epilepsy can be a difficult. In the first part of this review article we focus on recent insights into the neurobiological underpinnings of NES. We summarise a number of studies demonstrating the importance of abnormalities of emotion regulation in patients with NES. Evidence for abnormal emotion regulation comes from both self-report and experimental studies of pre-conscious cognitive processes. These studies show that NES are not the only manifestation of abnormal mental processing in these patients and that excessive social threat avoidance and emotional dysregulation are also evident between seizures and may therefore contribute to disability beyond the seizures themselves. In the second part of this review, we describe the findings of a number of studies, which have examined differences between the communication behaviour of patients with NES and those with epilepsy. We argue, that, whilst these studies initially aimed to help clinicians with the differential diagnosis of NES and epilepsy, close sociolinguistic analysis of patient's talk can also provide clues about the aetiology of NES. We conclude that the interaction of patient with NES with the doctor can be interpreted as a manifestation of avoidance and a demonstration of helplessness perhaps intended to secure active support from the doctor. In the third part of this review, we suggest that a close reading of a transcript of the interaction between a patient with NES and her doctor (and perhaps attentive listening to how patients' talk about themselves and their disorder) can yield clues to the causes of NES in individual cases.

Neural networks underlying hyperkinetic seizures of "temporal lobe" origin.

PURPOSE: Hyperkinetic seizures are most often considered to originate from prefrontal cortex. Recently however, it has been suggested that hyperkinetic seizures can be found in patients with temporal lobe seizures. The objective of this study was to determine the features of temporal epilepsy with hyperkinetic seizures and the functional anatomy of involved brain networks. METHODS: We retrospectively identified patients investigated by depth electrodes (SEEG) in whom hyperkinetic manifestations were proved to be linked to initial temporal lobe involvement. Seizure organisation was determined according to the "Epileptogenicity Index" (EI), a new way to quantify rapid discharges at seizure onset. RESULTS: We found 7 patients among 130 SEEG investigations that fulfilled the inclusion criteria. Most of the patients presented with hyperkinetic occurring (or predominating) during sleep. SEEG signal analysis demonstrated a common temporo-frontal network in which the temporal pole played a central role. Major involvement of the orbito-frontal cortex and to a lesser extent the cingulate gyrus was also a particular feature of these seizures. DISCUSSION: Seizures originating in the temporal lobe must be recognized as an important cause of hyperkinetic seizures. The temporal pole and its connexions with medio-basal prefrontal cortex represent the main structures involved in epileptogenic networks.

What is the significance of interictal water diffusion changes in frontal lobe epilepsies?

The aim of this study was to better understand the significance of interictal changes in water molecule diffusivity defined by diffusion-weighted imaging (DWI) in frontal lobe epilepsy (FLE), as well as to test the accuracy of interictal DWI in the definition of the epileptogenic zone (EZ). DWI was carried out in 14 patients with refractory FLE (9 negative-MRI) as well as in 25 controls. Statistical mapping analysis (SPM2) of diffusivity maps was used to detect, for each subject, significant diffusivity alterations. We then studied the relationships between diffusion and depth recorded electrical abnormalities. Clinical correlates of the extent of diffusivity changes were also tested. We found areas of significantly increased diffusivity (SID) in 13 patients. Eight had SID in the EZ, 9 within the irritative zone (IZ) and 12 outside, mainly in connected areas. We found a correlation between the extent of SID and the duration of epilepsy (p corrected=0.026, R=0.621). In addition, SID was significantly less widespread in negative-MRI patients (p=0.028). However, we found no significant differences concerning either seizure frequency (p=0.302), seizure generalization (p=0.841), history of status (p=0.396), or surgical outcome (p=0.606). We suggest that SID in normal appearing areas is not a specific signature of epileptogenicity in FLE, and is more likely to reflect multifactorial and potentially evolving neuro-glial injuries.

Gender differences in psychogenic non-epileptic seizures.

PURPOSE: To determine whether male and female populations of patients with psychogenic non-epileptic seizures (PNES) are similar, in terms of demographic and social factors, aetiological factors, the clinical characteristics of events and path to diagnosis. METHODS: Prospective study by semi-structured interview of 160 consecutive patients (117 female and 43 male) with video EEG confirmed diagnosis of PNES + epileptic seizures (ES). RESULTS: Most parameters showed no significant differences. Males were, however, more likely to be unemployed (P = 0.028), and females were six times more likely to self-harm (P = 0.050), though the numbers were small in these categories. Men were more likely to attribute their PNES to a predisposing factor for epilepsy (P = 0.001), and women were over eight times more likely to report sexual abuse (P = 0.001). Event semiology was similar, but women were more likely to weep after events (P = 0.017). The carers and family of men with PNES were three times less likely to accept the diagnosis of PNES (P = 0.017). CONCLUSIONS: Our samples showed few significant gender differences, suggesting that other male and female populations of patients with PNES are likely to be similar also. Some of the differences we found may give insight into causation of PNES.

Cortical stimulation study of the role of rhinal cortex in déjà vu and reminiscence of memories.

OBJECTIVE: To study the role of perirhinal (PC) and entorhinal cortices (EC) in dreamy state symptoms (déjà vu and reminiscence of scenes). These phenomena have been attributed to functional alteration of memory networks supported by the medial temporal lobes, principally involving the amygdala and hippocampus. The role of sub-hippocampal structures (EC and PC) in inducing these phenomena has not previously been addressed. METHODS: The authors studied the symptoms evoked by direct electrical stimulations of PC and EC in comparison with those obtained after stimulation of the amygdala and hippocampus. Stimulations were performed in a group of 24 patients with epilepsy, during stereoelectroencephalographic (SEEG) recordings in the setting of presurgical evaluation. All patients had electrodes that sampled the rhinal cortices, amygdala, and hippocampus. RESULTS: A total of 280 stimulations were analyzed. Entorhinal and perirhinal stimulations induced classic mesial temporal lobe responses (emotional, dysautonomic) but also more specific responses, particularly the déjà vu phenomenon and reminiscence of scenes. Such déjà vu or déjà vécu type responses were produced proportionately more often by stimulation of the EC than by stimulation of the amygdala and hippocampus. In particular, déjà vu was associated with stimulation of the EC and reminiscence of memories with PC stimulation. CONCLUSION: This study strongly suggests that experiential symptoms are largely dependent upon functional modification of the physiology of the rhinal cortices.

Use of short term video EEG in the diagnosis of attack disorders.

BACKGROUND: Distinguishing epileptic from psychogenic non-epileptic seizures (PNES) often requires video electroencephalography (EEG) recording. Inpatient recording is a limited resource; some evidence suggests that short term video EEG (SVEEG) is useful, but its role in practice has yet to be evaluated. OBJECTIVE: To assess the usefulness of SVEEG in the diagnosis of attack disorders. METHODS: One hundred and forty three SVEEG recordings were performed during an 18 month period. RESULTS: A diagnostic event was recorded in 72 of 143 (50.3%): PNES (n = 51), epilepsy (n = 7), or other attacks, such as movement disorders (n = 14). CONCLUSIONS: SVEEG is a robust and useful diagnostic technique, which complements existing resources.

Outpatient video EEG recording in the diagnosis of non-epileptic seizures: a randomised controlled trial of simple suggestion techniques.

OBJECTIVE: To assess the yield of recorded habitual non-epileptic seizures during outpatient video EEG, using simple suggestion techniques based on hyperventilation and photic stimulation. DESIGN: Randomised controlled trial of "suggestion" v "no suggestion" during outpatient video EEG recording. SETTING: Regional epilepsy service (tertiary care; single centre). PARTICIPANTS: 30 patients (22 female, 8 male), aged over 16 years, with a probable clinical diagnosis of non-epileptic seizures; 15 were randomised to each group. MAIN OUTCOME MEASURES: Yield of habitual non-epileptic seizures recorded, and requirement for additional inpatient video EEG. RESULTS: 10/15 patients had habitual non-epileptic seizures with suggestion; 5/15 had non-epileptic seizures with no suggestion (p = 0.058; NS); 8/9 patients with a history of previous events in medical settings had non-epileptic seizures recorded during study. Logistic regression analysis with an interaction clause showed a significant effect of suggestion in patients with a history of previous events in medical settings (p = 0.003). An additional inpatient video-EEG was avoided in 14 of the 30 patients (47%). CONCLUSIONS: Habitual non-epileptic seizures can be recorded reliably during short outpatient video EEG in selected patients. Simple (non-invasive) suggestion techniques increase the yield at least in the subgroup with a history of previous events in medical settings. Inpatient video EEG can be avoided in some patients.

Nonsteroidal anti-inflammatory drug associated diaphragm disease.

We present a case of anaemia and intestinal obstruction in a 78-year-old woman taking nonsteroidal anti-inflammatory drugs who was found to have diaphragm disease at laparotomy.