Consciousness Seizures Research Articles

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.

Consciousness transitions during epilepsy seizures through the lens of integrated information theory

Consciousness is one of the most complex aspects of human experience. Studying the mechanisms involved in the transitions among different levels of consciousness remains as one of the greatest challenges in neuroscience. In this study we use a measure of integrated information (ΦAR) to evaluate dynamic changes during consciousness transitions. We applied the measure to intracranial electroencephalography (SEEG) recordings collected from 6 patients that suffer from refractory epilepsy, taking into account inter-ictal, pre-ictal and ictal periods. We analyzed the dynamical evolution of ΦAR in groups of electrode contacts outside the epileptogenic region and compared it with the Consciousness Seizure Scale (CCS). We show that changes on ΦAR are significantly correlated with changes in the reported states of consciousness.

Consciousness alteration in focal epilepsy is related to loss of signal complexity and information processing

Alteration of awareness is a main feature of focal epileptic seizures. In this work, we studied how the information contained in EEG signals was modified during temporal lobe seizures with altered awareness by using permutation entropy (PE) as a measure of the complexity of the signal. PE estimation was performed in thirty-six seizures of sixteen patients with temporal lobe epilepsy who underwent SEEG recordings. We tested whether altered awareness (based on the Consciousness Seizure Score) was correlated with a loss of signal complexity. We estimated global changes in PE as well as regional changes to gain insight into the mechanisms associated with awareness impairment. Our results reveal a positive correlation between the decrease of entropy and the consciousness score as well as the existence of a threshold on entropy that could discriminate seizures with no alteration of awareness from seizures with profound alteration of awareness. The loss of signal complexity was diffuse, extending bilaterally and to the associative cortices, in patients with profound alteration of awareness and limited to the temporal mesial structures in patients with no alteration of awareness. Thus PE is a promising tool to discriminate between the different subgroups of awareness alteration in TLE.

Epilepsy-Specific Anxiety: A Potential Clue to the Seizure Onset Zone.

Anticipatory Anxiety of Seizures is Associated With Ictal Emotional Distress and Amygdala Onset Seizures Tarrada A, Aron O, Vignal JP, Ertan D, Maillard L, Hingray C. Epilepsia. 2022;63(5):1130-1140. doi:10.1111/epi.17215.Objective:Anxiety disorders are a frequent psychiatric condition in patients with epilepsy. Anticipatory anxiety of seizures (AAS) is described as a daily persistent fear or excessive worry of having a seizure. AAS seems to be related to “subjective ictal anxiety” reported by patients. The current study aimed to assess the association between objective ictal features and the presence of AAS.Methods:Ninety-one patients with drug-resistant focal epilepsy underwent a standardized psychiatric assessment, specific for epilepsy, and presurgical long-term video-electroencephalography (EEG) or stereo-EEG (SEEG). We compared seizure semiology and epilepsy features of patients with AAS (n = 41) to those of patients without AAS (n = 50). We analyzed emotional and motor behavior ictal signs as well as ictal consciousness. We further assessed amygdala ictal involvement in seizures recorded with SEEG (n = 28).Results:AAS was significantly associated with the presence of ictal emotional distress; negative emotional behavior (P < .01) and negative emotion were explicitly reported to the examiner during recording (P = .015), regardless of the ictal level of consciousness. Among the patients recorded with SEEG, we found a significant involvement of amygdala within the seizure onset zone (P < .01) for patients with AAS.Significance:Higher risk of developing AAS is associated with seizures expressing negative emotional symptoms, independently of ictal consciousness level. Persistent interictal fear of seizures might be viewed as the consequence of a reinforcement of the emotional networks secondary to amygdala involvement in seizures of temporal origin. Physicians should screen for AAS not only to assess the impact of epilepsy on daily life, but also as an interictal biomarker of ictal semiology and emotional network involvement at seizure onset.

Anticipatory anxiety of seizures is associated with ictal emotional distress and amygdala onset seizures

Anxiety disorders are a frequent psychiatric condition in patients with epilepsy. Anticipatory anxiety of seizures (AAS) is described as a daily persistent fear or excessive worry of having a seizure. AAS seems to be related to "subjective ictal anxiety" reported by patients. The current study aimed to assess the association between objective ictal features and the presence of AAS. Ninety-one patients with drug-resistant focal epilepsy underwent a standardized psychiatric assessment, specific for epilepsy, and presurgical long-term video-electroencephalography (EEG) or stereo-EEG (SEEG). We compared seizure semiology and epilepsy features of patients with AAS (n=41) to those of patients without AAS (n=50). We analyzed emotional and motor behavior ictal signs as well as ictal consciousness. We further assessed amygdala ictal involvement in seizures recorded with SEEG (n=28). AAS was significantly associated with the presence of ictal emotional distress; negative emotional behavior (p<.01) and negative emotion were explicitly reported to the examiner during recording (p=.015), regardless of the ictal level of consciousness. Among the patients recorded with SEEG, we found a significant involvement of amygdala within the seizure onset zone (p<.01) for patients with AAS. Higher risk of developing AAS is associated with seizures expressing negative emotional symptoms, independently of ictal consciousness level. Persistent interictal fear of seizures might be viewed as the consequence of a reinforcement of the emotional networks secondary to amygdala involvement in seizures of temporal origin. Physicians should screen for AAS not only to assess the impact of epilepsy on daily life, but also as an interictal biomarker of ictal semiology and emotional network involvement at seizure onset.

Time- and frequency-resolved covariance analysis for detection and characterization of seizures from intracraneal EEG recordings.

The amount of power in different frequency bands of the electroencephalogram (EEG) carries information about the behavioral state of a subject. Hence, neurologists treating epileptic patients monitor the temporal evolution of the different bands. We propose a covariance-based method to detect and characterize epileptic seizures operating on the band-filtered EEG signal. The algorithm is unsupervised and performs a principal component analysis of intra-cranial EEG recordings, detecting transient fluctuations of the power in each frequency band. Its simplicity makes it suitable for online implementation. Good sampling of the non-ictal periods is required, while no demands are imposed on the amount of data during ictal activity. We tested the method with 32 seizures registered in 5 patients. The area below the resulting receiver-operating characteristic curves was 87% for the detection of seizures and 91% for the detection of recruited electrodes. To identify the behaviorally relevant correlates of the physiological signal, we identified transient changes in the variance of each band that were correlated with the degree of loss of consciousness, the latter assessed by the so-called Consciousness Seizure Scale, summarizing the performance of the subject in a number of behavioral tests requested during seizures. We concluded that those crisis with maximal impairment of consciousness tended to exhibit an increase in variance approximately 40s after seizure onset, with predominant power in the theta and alpha bands and reduced delta and beta activity.

F175. Connectivity changes in selected EEG-networks during partial seizures with different types of alteration in consciousness: Ictal and interictal findings in 10 cases

Introduction Consciousness is a central concept in epilepsy: a transient loss characterizes generalized seizures and different types of consciousness impairment may occur during partial ones. Jackson described the “dreamy state” and suggested a consciousness dissociation caused by electrical disturbances at higher levels in hierarchical neural networks. The following decades accumulated evidence of ictal and interictal experiential phenomena and several physiopathogenic hypotheses were raised. Yet, even after the EEG breakthrough, the mechanisms of impaired consciousness and its relation to partial seizures remains elusive. Focal discharges cannot explain the flexibility and variability of experiential phenomena. Current models of brain function imply multiple processes in hierarchical modular assemblies with dynamical non-linear interactions. From this perspective, a focal discharge can modify network connectivity (NC) resulting in more varied and longer lasting changes. OBJECTIVES: (1) to identify changes in NC accompanying ictal and peri-ictal discharges in 10 patients that presented seizures with different psychic contents and (2) to correlate NC changes with the type of consciousness impairment during the seizure. Methods Seizures with altered consciousness, no motor component, were documented in 10 psychiatric patients. The Ictal Consciousness Inventory scored level (ICI-L) and content (ICI-C) of consciousness; psychotic features obtained from the Positive and Negative Symptom Scale (PANSS-P). Two minutes of EEG seizure activity, artifact free, eyes-closed, were analyzed with Neuroguide software to generate Low Resolution Electromagnetic Topography (LORETA) scores for each of the Broadman Areas (BA). Pearson correlations of spectral power and phase differences for each of the BA pairs in selected networks: Anxiety (AN), Dorsal Attention (DAN), Ventral Attention (VAN), Default-Mode (DMN), Affective (AN), Executive (EN), Memory (MN) and Language (LN). Connectivity Z-scores were calculated with Neuroguide normative database. Multiple correlation analysis tested correlations between affected networks and clinical scales. Results Seizures defined by EEG ictal activity were accompanied by psychic changes in all subjects. Psychic changes and NC patterns differed among patients. The DMN was altered in all subjects, differing in direction and magnitude in correlation with ICI-l. AN and VAN correlated with the PANSS scales. Changes in other networks varied across subjects, uncorrelated with clinical scales. Conclusion Our findings suggest that: (1) EEG-networks can be used to study different types of ictal consciousness impairment, (2) level, content and reality testing may vary independently, (3) variations correlate with patterns of altered NC, (4) DMN structures modulate ICI-L, (5) AN and VAN are involved in reality testing.

Prognostic Factors in Glioblastoma: Is There a Role for Epilepsy?

The prognostic relevance of epilepsy at glioblastoma (GBMs) onset is still under debate. In this study, we analyzed the value of epilepsy and other prognostic factors on GBMs survival. We retrospectively analyzed the clinical, radiological, surgical and histological data in 139 GBMs. Seizures were the presenting symptoms in 50 patients out of 139 (35.9%). 123 patients (88%) were treated with craniotomy and tumor resection while 16 (12%) with biopsy. The median overall survival was 9.9 months from surgery. At univariable Cox regression, the factors that significantly improved survival were age less than 65 years (P = 0.0015), focal without impairment of consciousness seizures at presentation (P = 0.043), complete surgical resection (P < 0.001), pre-operative Karnofsky performance status (KPS) > 70 (P = 0.015), frontal location (P < 0.001), radiotherapy (XRT) plus concomitant and adjuvant TMZ (P < 0.001). A multivariable Cox regression showed that the complete surgical resection (P < 0.0001), age less than 65 years (P = 0.008), frontal location (P = 0.0001) and XRT adjuvant temozolomide (TMZ) (P < 0.0001) were independent factors on longer survival. In our series epilepsy at presentation is not an independent prognostic factor for longer survival in GBM patients. Only in the subgroup of patients with focal seizures without impairment of consciousness, epilepsy was associated with an increased significant overall survival at univariate analysis (P = 0.043). Main independent factors for relatively favorable GBMs outcome are complete tumor resection plus combined XRT-TMZ, frontal location and patient age below 65 years old.

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

Background and PurposeDifferences in consciousness during seizures depend on the location of the seizure onset.MethodsThe 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.ResultsThe 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.ConclusionsPatients 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.

Altered states of consciousness in epilepsy: a DTI study of the brain

Background: A disturbance in the level of consciousness is a classical clinical sign of several seizure types. Recent studies have shown that altered states of consciousness in seizures are associated with structural and functional changes of several brain regions. Prominent among these are the thalamus, the brain stem and the default mode network, which is part of the consciousness system. Our study used diffusion tensor imaging (DTI) to evaluate these brain regions in patients with three different types of epilepsies that are associated with altered consciousness: complex partial seizures (CPS), primary generalized tonic–clonic seizures (PGTCS) or secondary generalized tonic–clonic seizures (SGTCS). Additionally, this study further explores the probable mechanisms underlying impairment of consciousness in seizures. Materials and methods: Conventional MRI and DTI scanning were performed in 51 patients with epilepsy and 51 healthy volunteers. The epilepsy group was in turn subdivided into three subgroups: CPS, PGTCS or SGTCS. Each subgroup comprised 17 patients. Each subject involved in the study underwent a DTI evaluation of the brain to measure the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values of nine regions of interest: the postero-superior portion of midbrain, the bilateral dorsal thalamus, the bilateral precuneus/posterior cingulate, the bilateral medial pre-frontal gyri and the bilateral supramarginalgyri. The statistical significance of the measured ADC and FA values between the experimental and control groups was analysed using the paired t-test, and one-way analysis of variance was performed for a comparative analysis between the three subgroups. Results: Statistically significantly higher ADC values ( p < 0.01) were observed in the bilateral dorsal thalamus and postero-superior aspect of the midbrain in the three patient subgroups than in the control group. There were no significant changes in the ADC values ( p > 0.05) in the bilateral precuneus/posterior cingulate, bilateral medial pre-frontal gyri or bilateral supramarginalgyri in the experimental group. Among the three patient subgroups and the ADC values of corresponding brain regions, there were no statistically significant changes. Statistically significantly lower FA values ( p < 0.05) were observed in the bilateral dorsal thalamus of the patients in the three subgroups than in the control group. Significantly lowered FA values from the postero-superior aspect of the mid brain ( p < 0.01) were observed in patients with PGTCS compared with the control group. There were no significant changes in the FA values ( p > 0.05) from the bilateral precuneus/posterior cingulate, bilateral medial frontal gyri or bilateral supramarginalgyri in the experimental group. Among the three patient subgroups and the FA values of the corresponding brain regions, there were no statistically significant changes. Conclusion: In epileptic patients with CPS, PGTCS or SGTCS, there seems to be a long-lasting neuronal dysfunction of the bilateral dorsal thalamus and postero-superior aspect of the midbrain. The thalamus and upper brain stem are likely to play a key role in epileptic patients with impaired consciousness.

Subjective and objective characteristics of altered consciousness during epileptic seizures.

Conscious states are inner states and processes of awareness. These states are by definition subjective. We analyzed subjective and objective characteristics of alteration of consciousness (AOC) during epileptic seizures, including its involvement in both the level of awareness and subjective content of consciousness. We evaluated AOC using the Consciousness Seizure Scale, the Ictal Consciousness Inventory, and a new structured survey developed by our group: the Seizure Perception Survey, which incorporates patients' subjective experiences before and after they watch a video-electroencephalographic recording of their own seizure. We included 35 patients (105 seizures) with drug-resistant epilepsy. Most seizures caused profound AOC. The content of consciousness was lower during temporal seizures with profound AOC. We uncovered a correlation between the subjective perception and objective duration of a seizure using the Seizure Perception Survey regarding memory; the patients had a better recall of ictal onset during wakefulness regardless of the epileptogenic zone, laterality, or magnitude of AOC. Nonetheless, the recovery of memory at the end of a seizure took more time in patients who showed greater AOC, less vivid content of consciousness, or a longer seizure. For 85% of the patients, this was the first time they were able to view their own seizures. The majority of the patients requested to view them again because this procedure allowed them to compare the recordings with their own memories and emotions during a seizure and to verify the real duration of the seizure. Alteration of consciousness is one of the most dramatic clinical manifestations of epilepsy. Usually, practitioners or relatives assume that the patients with AOC may not have any knowledge on their seizures. In this study, however, we found that most patients with AOC had a fairly accurate perception of the duration of a seizure and retained their memory of ictal onset. In contrast, for the majority of the patients, watching their own seizure was an extremely positive experience, and most patients stated that they were surprised as well as glad to view what really happened, without expressing negative opinions. Inclusion of subjective characteristics of AOC into the analysis yielded complete assessment of various dimensions of consciousness and therefore allowed us to gain a more detailed understanding of consciousness.

Altered synchrony and loss of consciousness during frontal lobe seizures

ObjectiveLoss of consciousness (LOC) in frontal lobe epilepsy (FLE) has been rarely specifically studied until now. In this study we evaluated the LOC in a population of patients with FLE and studied the relationship between changes in synchrony and degree of LOC. Methods24 patients undergoing stereoelectroencephalography (SEEG) during pre-surgical evaluation of FLE were studied. The LOC intensity was scored using the Consciousness Seizure Scale (CSS). For each studied seizure (n=52), interdependencies between signals recorded from 5 brain regions were estimated as a function of time by using non-linear regression analysis (h2 coefficient). ResultsSeizures were divided into 3 groups according to the CSS scale: group A (no LOC) with a score ⩽2, group B (intermediate or partial LOC) with a score ranging from 3 to 5, and group C (maximal LOC) with a score ⩾6. The majority of seizures in FLE patients disclosed significant LOC, particularly for patients with prefrontal lobe seizures. Mean correlation values were significantly different between groups A and C (p<0.001), the maximal values of synchrony being observed in group C. Differences were significant for interaction affecting the external prefrontal cortex (p=0.004) (p=0.01) and the parietal cortex. In addition, a significant correlation was found between CSS scores and correlations values (h2) of the prefrontal and the parietal region but not with the premotor cortex. ConclusionsThis study indicates that in FLE, prefrontal seizures frequently alter consciousness. As in other focal seizures, LOC appears to be related to changes in synchrony in prefrontal and parietal associative cortices. SignificanceLOC in FLE is frequent and as in other focal epilepsies is related to an alteration of prefrontal–parietal network.

Commentary: The return of consciousness to epilepsy seizure classification.

Commentary: The return of consciousness to epilepsy seizure classification.

Consciousness as a useful concept in epilepsy classification.

Impaired consciousness has important practical consequences for people living with epilepsy. Recent pathophysiologic studies show that seizures with impaired level of consciousness always affect widespread cortical networks and subcortical arousal systems. In light of these findings and their clinical significance, efforts are underway to revise the International League Against Epilepsy (ILAE) 2010 report to include impaired consciousness in the classification of seizures. Lüders and colleagues have presented one such effort, which we discuss here. We then propose an alternative classification of impaired consciousness in epilepsy based on functional neuroanatomy. Some seizures involve focal cortical regions and cause selective deficits in the content of consciousness but without impaired overall level of consciousness or awareness. These include focal aware conscious seizures (FACS) with lower order cortical deficits such as somatosensory or visual impairment as well as FACS with higher cognitive deficits including ictal aphasia or isolated epileptic amnesia. Another category applies to seizures with impaired level of consciousness leading to deficits in multiple cognitive domains. For this category, we believe the terms "dyscognitive" or "dialeptic" should be avoided because they may create confusion. Instead we propose that seizures with impaired level of consciousness be described based on underlying pathophysiology. Widespread moderately severe deficits in corticothalamic function are seen in absence seizures and in focal impaired consciousness seizures (FICS), including many temporal lobe seizures and other focal seizures with impaired consciousness. Some simple responses or automatisms may be preserved in these seizures. In contrast, generalized tonic-clonic seizures usually produce widespread severe deficits in corticothalamic function causing loss of all meaningful responses. Further work is needed to understand and prevent impaired consciousness in epilepsy, but the first step is to keep this crucial practical and physiologic aspect of seizures front-and-center in our discussions.

Commentary: Consciousness of epilepsy.

Words matter. We should be conscious of their impact. Or would it be better to say we should be aware of their impact? The articles by Lüders et al.1 and accompanying commentary by Blumenfeld and Meador2 provide thoughtful analyses of the inadequacies of a simple concept of consciousness to characterize seizures. No fewer than five varieties of alterations of consciousness are needed to span the behaviors commonly seen during seizures. With such a large range, how practical is consciousness as a descriptor? Consciousness is beyond dispute as an important aspect of human experience and as an area for scientific study, but seizure classifiers need to be definable and detectable in a simple, replicable way. Consciousness is neither of these. What are the alternatives? One approach is to define focal seizures as a single large category, with no formal subdivisions, as proposed by the 2010 International League Against Epilepsy (ILAE) Commission.3 This takes consciousness out of the picture, except as an optional descriptor. A second approach is to define a subcategory called “focal dyscognitive seizures,” as was done by Blume et al.4 and the 2001 ILAE Glossary task force. As pointed out by Blumenfeld and Meador,2 focal dyscognitive is understandable, but not equivalent to common current use of the term complex partial. Dyscognitive does not imply loss of consciousness. A more practical approach would be to base seizure classification on measurable behaviors, such as memory, responsiveness, and awareness, as well as specific motor, sensory, autonomic, and cognitive malfunctions. Numerous studies of consciousness use awareness, memory, responsiveness5 or orientation, language, visual processing, motor praxis, sensorimotor responses, and visual tracking6 as testable surrogates for the level of consciousness, although not to the exclusion of subjective phenomena. While awake, it is possible to be conscious and unresponsive or conscious and amnestic, but probably not conscious and unaware of the external world. Professor Blumenfeld commented that “An altered level of consciousness, evidenced by decreased overall arousal and responsiveness [italics added], is the defining feature of complex partial seizures.”7 Given that arousal, awareness, and responsiveness comprise the defining features, and consciousness can be measured only via surrogates and subjective reports, why propose, as Blumenfeld and Meador do in their commentary, “Focal Aware Conscious Seizures,” instead of “Focal Aware Seizures.” This is not the place to propose a specific classification, but only to argue that a seizure classification should be based on measurable behaviors and simple subjective perceptions, such as numbness. We can decide whether someone should be driving based on awareness, responsiveness, and sensorimotor abilities during a seizure. Specification of details of consciousness is not required. Einstein advised us that “Everything should be made as simple as possible, but no simpler,”8 Consciousness does not simplify classification of seizures. I have no conflicts of interest to disclose. I confirm that I have read the Journal's position on issues involved in ethical publication and affirm that this report is consistent with those guidelines. Dr. Robert S. Fisher is the Maslah Saul MD Professor of Neurology & Neurological Sciences at Stanford University in Stanford, California.

Commentary – Should consciousness be included in the classification of focal (partial) seizures?

The ILAE 2010 report does not classify focal seizures and instead uses “descriptors” to distinguish focal seizures with versus without impaired consciousness. Below, we recall a recent informal conversation that took place while traveling a back road in Australia (true story), discussing problems with the old terms as well as new biological and practical evidence separating events formerly known as complex partial versus simple partial seizures. Impaired level of consciousness is a core distinguishing feature of focal seizures, which arises from established physiological mechanisms and can be readily determined based on behavior in most cases. After some debate, we arrive at succinct terms compatible with the old as well as the new ILAE classification report: Focal Impaired Consciousness Seizures (FICS), and Focal Aware Conscious Seizures (FACS). We hope that this discussion will bring impaired consciousness off the back roads of epilepsy classification, and provide useful names for these two very common seizure types.

Impaired consciousness in epilepsy investigated by a prospective responsiveness in epilepsy scale (RES)

Impaired consciousness in epileptic seizures has a major negative impact on patient quality of life. Prior work on epileptic unconsciousness has mainly used retrospective and nonstandardized methods. Our goal was to validate and to obtain initial data using a standardized prospective testing battery. The responsiveness in epilepsy scale (RES) was used on 52 patients during continuous video-electroencephalography (EEG) monitoring. RES begins with higher-level questions and commands, and switches adaptively to more basic sensorimotor responses depending on patient performance. RES continues after seizures and includes postictal memory testing. Scoring was conducted based on video review. Testing on standardized seizure simulations yielded good intrarater and interrater reliability. We captured 59 seizures from 18 patients (35% of participants) during 1,420 h of RES monitoring. RES impairment was greatest during and after tonic-clonic seizures, less in partial seizures, and minimal in auras and subclinical seizures. In partial seizures, ictal RES impairment was significantly greater if EEG changes were present. Maximum RES impairment (lowest ictal score) was also significantly correlated with long postictal recovery time, and poor postictal memory. We found that prospective testing of responsiveness during seizures is feasible and reliable. RES impairment was related to EEG changes during seizures, as well as to postictal memory deficits and recovery time. With a larger patient sample it is hoped that this approach can identify brain networks underlying specific components of impaired consciousness in seizures. This may allow the development of improved treatments targeted at preventing dysfunction in these networks.

William Gowers’ interpretation of epileptogenic mechanisms: 1880-1906

In the 1870s, early in his neurologic career, William Gowers (1845-1911) was exposed to three main schools of thought concerning epileptogenesis, namely, that seizures resulted from (1) excessive neural activity in the medulla oblongata or pons (Marshall Hall, John Russell Reynolds, and Brown-Séquard), (2) excessive local cerebral cortical activity (Hughlings Jackson), or (3) suddenly decreased cerebral activity that released the intrinsic contractibility of skeletal muscle (Radcliffe). By 1881, Gowers had reasoned his way to the idea that epileptogenesis was best accounted for by local cortical overactivity. This overactivity might at times be initiated by local loss of inhibition. The overactivity in turn then might inhibit other parts of the central nervous system to explain loss of consciousness in seizures and postseizure temporary hemiparesis. The possibilities of the idea of inhibition, at first often called "resistance," continued to interest Gowers over the following 25 years. He settled on the synaptic gap as its likely site. However, the inhibition mechanism that he proposed, namely, retraction of dendrites, was rather extraordinary in the light of subsequent knowledge.

How to Assess Ictal Consciousness?

Despite the complexity and methodological difficulties in defining the concept of consciousness, it is a central concept in epileptology, and should thus be tractable for scientific analysis. In the present article, a two-dimensional model consisting of concepts related to the level and the contents of consciousness will be presented. This model has been found to be well suited for the description of seizure-induced alterations of consciousness, and is supported both by findings from neuroimaging and electrophysiological studies as well as from phenomenological studies. Further, we will review both traditional introspective methods as well as methods that have recently been developed or utilized in epilepsy research, summarize the main findings concerning first person experiences during epileptic seizures acquired with some of these methods, and discuss their strengths and weaknesses.

How to assess ictal consciousness?

Despite the complexity and methodological difficulties in defining the concept of consciousness, it is a central concept in epileptology, and should thus be tractable for scientific analysis. In the present article, a two-dimensional model consisting of concepts related to the level and the contents of consciousness will be presented. This model has been found to be well suited for the description of seizure-induced alterations of consciousness, and is supported both by findings from neuroimaging and electrophysiological studies as well as from phenomenological studies. Further, we will review both traditional introspective methods as well as methods that have recently been developed or utilized in epilepsy research, summarize the main findings concerning first person experiences during epileptic seizures acquired with some of these methods, and discuss their strengths and weaknesses.