The assessment of consciousness during partial seizures

What does it mean for consciousness to be multidimensional? A narrative review

A recent development in the psychological and neuroscientific study of consciousness has been the tendency to conceptualize consciousness as a multidimensional phenomenon. This narrative review elucidates the notion of dimensionality of consciousness and outlines the key concepts and disagreements on this topic through the viewpoints of several theoretical proposals. The reviewed literature is critically evaluated, and the main issues to be resolved by future theoretical and empirical work are identified: the problems of dimension selection and dimension aggregation, as well as some ethical considerations. This narrative review is seemingly the first to comprehensively overview this specific aspect of consciousness science.

Tests for consciousness in humans and beyond

Which systems/organisms are conscious? New tests for consciousness ('C-tests') are urgently needed. There is persisting uncertainty about when consciousness arises in human development, when it is lost due to neurological disorders and brain injury, and how it is distributed in nonhuman species. This need is amplified by recent and rapid developments in artificial intelligence (AI), neural organoids, and xenobot technology. Although a number of C-tests have been proposed in recent years, most are of limited use, and currently we have no C-tests for many of the populations for which they are most critical. Here, we identify challenges facing any attempt to develop C-tests, propose a multidimensional classification of such tests, and identify strategies that might be used to validate them.

Stereo-EEG features of temporal and frontal lobe seizures with loss of consciousness

The loss of consciousness (LOC) during seizures is one of the most striking features that significantly impact the quality of life, even though the neuronal network involved is not fully comprehended. We analyzed the intracerebral patterns in patients with focal drug-resistant epilepsy, both with and without LOC. We assessed the localization, lateralization, stereo electroencephalography (SEEG) patterns, seizure duration, and the quantification of contacts exhibiting electrical discharge. The degree of LOC was quantified using the Consciousness Seizure Scale. Thirteen patients (40 seizures) with focal drug-resistant epilepsy underwent SEEG. In cases of temporal lobe epilepsy (TLE, 6 patients and 15 seizures), LOC occurred more frequently in seizures with mesial rather than lateral temporal lobe onset. On the other hand, in cases of frontal lobe epilepsy (7 patients; 25 seizures), LOC was associated with pre-frontal onset, a higher number of contacts with epileptic discharge compared to the onset count and longer seizure durations. Our study revealed distinct characteristics during LOC depending on the epileptogenic zone. For temporal lobe seizures, LOC was associated with mesial seizure onset, whereas in frontal lobe epilepsy, seizure with LOC has a significant increase in contact showing epileptiform discharge and a pre-frontal onset. This phenomenon may be correlated with the broad neural network required to maintain consciousness, which can be affected in different ways, resulting in LOC.

Prevalence and clinical correlates of non-convulsive status epilepticus in elderly patients with acute confusional state: A systematic literature review

Non-convulsive status epilepticus (NCSE) is a potentially treatable condition that poses considerable diagnostic challenges. NCSE is thought to be more common in the elderly than in the general population, however additional diagnostic challenges complicate its recognition in older patients, because of the wide differential diagnosis with common underlying causes of acute confusional state in this age group. We set out to review the existing evidence on the clinical correlates of NCSE in the elderly population. A systematic literature review was conducted according to the methodological standards outlined in the PRISMA statement to assess the clinical correlates of NCSE in patients aged 60 or older. Our literature search identified 11 relevant studies, which confirmed that the incidence of NCSE increases with age, in particular with regard to focal forms with impairment of consciousness. Female gender, history of epilepsy (or a recently witnessed seizure with motor features), and abnormal ocular movements appeared to correlate with the diagnosis of NCSE in the elderly, prompting prioritization of electroencephalography tests for diagnostic confirmation. Epidemiological data in the elderly vary widely because of the heterogeneity of definitions and diagnostic criteria applied across different studies. Based on our findings, it is recommended to keep a low threshold for requesting electroencephalography tests to confirm the diagnosis of NCSE in elderly patients with acute confusional state, even in the presence of a presumed symptomatic cause.

Investigation of patient and observer agreement on description of seizures at initial clinical visit

There have been few studies of agreement between seizure descriptions obtained from patients and observers. We investigated 220 patients and observers who completed structured questionnaires about patients’ semiological seizure features at the initial clinical visit. Inter‐rater reliability was assessed using Cohen’s kappa and indices of positive and negative agreement. Patients and observers had excellent agreement on the presence of memory impairment and generalized shaking and stiffness during seizures. In addition, patients under‐reported seizure descriptions more easily observed externally, whereas observers under‐reported change in patient location at seizure end. These findings may guide interpretation of clinical histories obtain in epilepsy care.

Structured testing during seizures: A practical guide for assessing and interpreting ictal and postictal signs during video EEG long term monitoring

BACKGROUND

Ictal and postictal testing carried out in long-term epilepsy monitoring units is often sub-optimal. Recently, a European consensus protocol for testing patients during and after seizures was developed by a joint taskforce of the International League Against Epilepsy - Commission on European Affairs and the European Epilepsy Monitoring Unit Association.

AIM

Using this recently developed standardised assessment battery as a framework, the goal of this narrative review is to outline the proposed testing procedure in detail and explain the rationale for each individual component, focusing on the underlying neurobiology. This is intended to serve as an educational resource for staff working in epilepsy monitoring units.

METHODS

A literature review of PubMed was performed; using the search terms "seizure", "ictal", "postictal", "testing", "examination", and "interview". Relevant literature was reviewed and relevant references were chosen. The work is presented as a narrative review.

RESULTS

The proposed standardised assessment battery provides a comprehensive and user-friendly format for ictal-postictal testing, and examines consciousness, language, motor, sensory, and visual function.

CONCLUSION

The standardised approach proposed has the potential to make full use of data recorded during video EEG increasing the diagnostic yield with regards to lateralisation and localisation, aiding both presurgical and diagnostic studies.

Déjà-rêvé: Prior dreams induced by direct electrical brain stimulation

BACKGROUND

Epileptic patients sometimes report experiential phenomena related to a previous dream they had during seizures or electrical brain stimulation (EBS). This has been alluded to in the literature as "déjà-rêvé" ("already dreamed"). However, there is no neuroscientific evidence to support its existence and this concept is commonly mixed up with déjà-vu. We hypothesized that déjà-rêvé would be a specific entity, i.e., different from other experiential phenomena reported in epileptic patients, induced by EBS of specific brain areas.

METHODS

We collected all experiential phenomena related to dreams induced by electrical brain stimulations (EBS) in our epileptic patients (2003-2015) and in a review of the literature. The content of these déjà-rêvé and the location of EBS were analyzed.

RESULTS

We collected 7 déjà-rêvé in our database and 35 from the literature, which corresponds to an estimated prevalence of 0.3‰ of all EBS-inducing déjà-rêvé. Déjà-rêvé is a generic term for three distinct entities: it can be the recollection of a specific dream ("episodic-like"), reminiscence of a vague dream ("familiarity-like") or experiences in which the subject feels like they are dreaming (literally "a dreamy state"). EBS-inducing "episodic-like" and "familiarity-like" déjà-rêvé were mostly located in the medial temporal lobes. "Dreamy states" were induced by less specific EBS areas although still related to the temporal lobes.

CONCLUSIONS

This study demonstrates that déjà-rêvé is a heterogeneous entity that is different from déjà-vu, the historical "dreamy state" definition and other experiential phenomena. This may be relevant for clinical practice as it points to temporal lobe dysfunction and could be valuable for studying the neural substrates of dreams.

SPECT perfusion changes during ictal automatisms with preserved responsiveness in patients with right temporal lobe epilepsy

Ictal automatism with preserved responsiveness (APR) has been reported, particularly in nondominant temporal lobe epilepsy (TLE), but its pathophysiology remains poorly understood. This study sought to investigate the relationship between APRs and increased cerebral blood flow (CBF) using ictal single photon emission computed tomography (SPECT) in TLE. Forty-seven subjects with right mesial TLE (15 with and 32 without APR) were enrolled. Patients with APR (APR+) were subdivided into four groups according to degree of responsiveness during seizures. Cerebral blood flow changes during these seizures were semiquantitatively assessed by subtraction ictal SPECT coregistered to MRI (SISCOM). Hyperperfusion in temporal regions did not vary significantly between the APR+ and APR- groups. Cerebral blood flow changes in the frontal area, insula, cingulum, and occipital area were also nonsignificant. However, hyperperfusion in the ipsilateral parietal areas was more frequent in the APR- group than in the APR+ group. Furthermore, hyperperfusion of the contralateral basal ganglia showed an inclination to be more common in the APR- group, but without statistical significance. The study suggested that the involvement of the parietal association cortex during seizure may play an important role in ictal loss of consciousness in TLE. Further studies will be needed to elucidate the pathophysiology of changes in consciousness during temporal lobe seizures.

Evaluation of Ictal Consciousness in Temporal and Extra Temporal Epilepsy: Observations from a Tertiary Care Hospital in India

Background and Purpose

Differences in consciousness during seizures depend on the location of the seizure onset.

Methods

The present study evaluates ictal consciousness using the ictal consciousness inventory (ICI) in drug refractory mesial temporal (MTLE), neocortical temporal (NTLE) and extra temporal epilepsy (ETLE). This was a cross sectional cohort study with 45 patients with mesial temporal epilepsy, 47 with extra temporal and 11 patients with neocortical temporal epilepsy. The ICI a 20 item questionnaire was used to calculate the scores for level (L, question 1–10) and content (C, question 11–20) of consciousness.

Results

The patients in mesial temporal group had higher ICI-L scores, p = 0.0129 as compared to the extra temporal group, but no difference was observed in the content of consciousness. The ICI-L and C scores were not different in the mesial temporal and the neocortical temporal group (p = 0.53 and 0.65) respectively.

Conclusions

Patients with mesial temporal epilepsy had a higher level of consciousness than the extra temporal group but there was no difference in the content. Also there was no difference in the level and content of consciousness between mesial and the neocortical temporal group.

Neurophysiological investigations for the diagnosis of non-epileptic attack disorder in neuropsychiatry services: from safety standards to improved effectiveness

OBJECTIVE

The discipline of clinical neuropsychiatry currently provides specialised services for a number of conditions that cross the traditional boundaries of neurology and psychiatry, including non-epileptic attack disorder. Neurophysiological investigations have an important role within neuropsychiatry services, with video-electroencephalography (EEG) telemetry being the gold standard investigation for the differential diagnosis between epileptic seizures and non-epileptic attacks. This article reviews existing evidence on best practices for neurophysiology investigations, with focus on safety measures for video-EEG telemetry.

METHODS

We conducted a systematic literature review using the PubMed database in order to identify the scientific literature on the best practices when using neurophysiological investigations in patients with suspected epileptic seizures or non-epileptic attacks.

RESULTS

Specific measures need to be implemented for video-EEG telemetry to be safely and effectively carried out by neuropsychiatry services. A confirmed diagnosis of non-epileptic attack disorder following video-EEG telemetry carried out within neuropsychiatry units has the inherent advantage of allowing diagnosis communication and implementation of treatment strategies in a timely fashion, potentially improving clinical outcomes and cost-effectiveness significantly.

CONCLUSION

The identified recommendations set the stage for the development of standardised guidelines to enable neuropsychiatry services to implement streamlined and evidence-based care pathways.

Impaired consciousness in partial seizures is bimodally distributed

OBJECTIVE

To investigate whether impaired consciousness in partial seizures can usually be attributed to specific deficits in the content of consciousness or to a more general decrease in the overall level of consciousness.

METHODS

Prospective testing during partial seizures was performed in patients with epilepsy using the Responsiveness in Epilepsy Scale (n = 83 partial seizures, 30 patients). Results were compared with responsiveness scores in a cohort of patients with severe traumatic brain injury evaluated with the JFK Coma Recovery Scale-Revised (n = 552 test administrations, 184 patients).

RESULTS

Standardized testing during partial seizures reveals a bimodal scoring distribution, such that most patients were either fully impaired or relatively spared in their ability to respond on multiple cognitive tests. Seizures with impaired performance on initial test items remained consistently impaired on subsequent items, while other seizures showed spared performance throughout. In the comparison group, we found that scores of patients with brain injury were more evenly distributed across the full range in severity of impairment.

CONCLUSIONS

Partial seizures can often be cleanly separated into those with vs without overall impaired responsiveness. Results from similar testing in a comparison group of patients with brain injury suggest that the bimodal nature of Responsiveness in Epilepsy Scale scores is not a result of scale bias but may be a finding unique to partial seizures. These findings support a model in which seizures either propagate or do not propagate to key structures that regulate overall arousal and thalamocortical function. Future investigations are needed to relate these behavioral findings to the physiology underlying impaired consciousness in partial seizures.

Epileptic qualia and self-awareness: a third dimension for consciousness

Over the last few decades, there has been increasing awareness among epileptologists about the need to refine our understanding and assessment of ictal consciousness, focusing on both subjective and behavioral aspects of seizures. Specifically, there have been suggestions that both the internal and external milieux - the former related to the phenomenal qualia of experience, the latter related to behavior - must be taken into account for a better understanding of altered states of consciousness in epilepsy. It has been proposed that clinical and experimental data from patients experiencing alterations of consciousness during epileptic seizures could be better understood within a bidimensional model, in which any manifestation of conscious experience can be plotted according to the level and contents of consciousness. The 'level' axis measures the degree of alertness/arousal, whereas the 'contents' axis measures the vividness of specific experiential phenomena reported by the patient. We argue that certain seizure types might require more rigorous conceptual models for their characterization, and we highlight the potential usefulness of a more refined framework which includes a further dimension related to the 'self', in addition to those of 'level' and 'contents'. This model could be visualized in a three-dimensional space to allow fine-grained distinctions between epileptic seizures.

Video-electroencephalography investigation of ictal alterations of consciousness in epilepsy and nonepileptic attack disorder: practical considerations

The ictal assessment of consciousness is of central importance in the differential diagnosis of epilepsy and nonepileptic attack disorder (NEAD). Long-term video-electroencephalography (video-EEG) is currently considered the gold standard investigative technique for the evaluation of patients with recurrent attacks associated with transient alterations of arousal (responsiveness) and/or awareness (experiential states). This paper offers a concise review focusing on the practical aspects of clinical relevance in the video-EEG diagnostic workout of inpatients with suspected epilepsy or NEAD, as outlined in existing guidelines and recommendations. The reviewed literature implies that both implementation of specific procedures (e.g., activation maneuvers) and interpersonal approach (e.g., monitoring protocols) during video-EEG should be tailored to the individual patient's presentation.

The quantitative measurement of consciousness during epileptic seizures

The assessment of consciousness is a fundamental element in the classification of epileptic seizures. It is, therefore, of great importance for clinical practice to develop instruments that enable an accurate and reliable measurement of the alteration of consciousness during seizures. Over the last few years, three psychometric scales have been specifically proposed to measure ictal consciousness: the Ictal Consciousness Inventory (ICI), the Consciousness Seizure Scale (CSS), and the Responsiveness in Epilepsy Scale--versions I and II (RES-I and RES-II). The ICI is a self-report psychometric instrument which retrospectively assesses ictal consciousness along the dimensions of the level/arousal and contents/awareness. The CSS has been used by clinicians to quantify the impairment of consciousness in order to establish correlations with the brain mechanisms underlying alterations of consciousness during temporal lobe seizures. The most recently developed observer-rated instrument is the RES-I, which has been used to assess responsiveness during epileptic seizures in patients undergoing video-EEG. The implementation of standardized psychometric tools for the assessment of ictal consciousness can complement clinical observations and contribute to improve accuracy in seizure classification.

Prospective assessment of ictal behavior using the revised Responsiveness in Epilepsy Scale (RES-II)

Impaired consciousness in epilepsy has a significant negative impact on patients' quality of life yet is difficult to study objectively. Here, we develop an improved prospective Responsiveness in Epilepsy Scale-II (RES-II) and report initial results compared with the earlier version of the scale (RES). The RES-II is simpler to administer and includes both verbal and non-verbal test items. We evaluated 75 seizures (24 patients) with RES and 34 seizures (11 patients) with RES-II based on video-EEG review. The error rate per seizure by test administrators improved markedly from a mean of 2.01 ± 0.04 with RES to 0.24 ± 0.11 with RES-II. Performance during focal seizures showed a bimodal distribution, corresponding to the traditional complex partial vs. simple partial seizure classification. We conclude that RES-II has improved accuracy and testing efficiency compared with the original RES. Prospective objective testing will ultimately lead to a better understanding of the mechanisms of impaired consciousness in epilepsy.

Epilepsy, unawareness of seizures and driving license: the potential role of 24-hour ambulatory EEG in defining seizure freedom

INTRODUCTION

Seizures represent a potential source of accidents/death. Permission to drive may, therefore, be granted in a seizure-free period. Laws and regulations regarding this issue vary widely, and the onus of reporting seizures ultimately rests on the individual. Unfortunately, as some patients are unaware of their seizures, their reports may be unreliable.

METHODS

In this retrospective study, we selected, from a group of 1100 consecutive patients, 57 cases (26 males/31 females; mean age: 42.5 years) in whom the AEEG documented ictal events (UIEs) not reported in a self-kept diary. By means of a simple questionnaire, we interviewed all these patients to collect information on driving licenses. We, thus, assessed how many of these patients (both drug resistant and seizure free) drove regularly.

RESULTS

Our study shows a relatively large number of patients with epilepsy and UIEs. Fifteen patients suffered from idiopathic generalized epilepsy (IGE) while 42 had partial epilepsy (PE). The patients were seizure free in 21 cases and 36 had drug-resistant seizures. Many patients in both these subgroups had a driving license and drove normally (active driving in 12/36 drug-resistant patients and in 18/21 seizure-free patients). Worthy of note is the finding that an "apparently" seizure-free group of patients drove regularly.

CONCLUSIONS

This study revealed a large number of patients (both drug resistant and seizure free) with AEEG-documented UIEs. This finding highlights the usefulness of AEEG in clinical practice as a means of more accurately ascertaining seizure freedom and supporting decisions involving the renewal or granting of a driving license.

Impaired consciousness in epilepsy

Consciousness is essential to normal human life. In epileptic seizures consciousness is often transiently lost, which makes it impossible for the individual to experience or respond. These effects have huge consequences for safety, productivity, emotional health, and quality of life. To prevent impaired consciousness in epilepsy, it is necessary to understand the mechanisms that lead to brain dysfunction during seizures. Normally the consciousness system-a specialised set of cortical-subcortical structures-maintains alertness, attention, and awareness. Advances in neuroimaging, electrophysiology, and prospective behavioural testing have shed light on how epileptic seizures disrupt the consciousness system. Diverse seizure types, including absence, generalised tonic-clonic, and complex partial seizures, converge on the same set of anatomical structures through different mechanisms to disrupt consciousness. Understanding of these mechanisms could lead to improved treatment strategies to prevent impairment of consciousness and improve the quality of life of people with epilepsy.