Guido Rubboli

Encephalopathy with electrical status epilepticus during slow sleep or ESES syndrome including the acquired aphasia

Encephalopathy with electrical status epilepticus during sleep or ESES is an age-dependent and self-limited syndrome whose distinctive features include a characteristic age of onset (with a peak around 4-5 years), heterogeneous seizures types (mostly partial motor or unilateral seizures during sleep and absences or falls while awake), a typical EEG pattern (with continuous and diffuse paroxysms occupying at least 85% of slow wave sleep) and a variable neuropsychological regression consisting of IQ decrease, reduction of language (as in acquired aphasia or Landau-Kleffner syndrome), disturbance of behaviour (psychotic states) and motor impairment (in the form of ataxia, dyspraxia, dystonia or unilateral deficit). Despite the long-term favourable outcome of epilepsy and status epilepticus during sleep (SES), the prognosis is guarded because of the persistence of severe neuropsychological and/or motor deficits in approximately half of the patients. No specific treatment has been advocated for this syndrome, but valproate sodium, benzodiazepines and ACTH have been shown to control the seizures and the SES pattern in many cases, although often only temporarily. Subpial transection is proposed in some instances as in non-regressive acquired aphasia. Recent data support the concept that ESES syndrome may include a large subset of developmental or acquired regressive conditions of infancy.

Central pattern generators for a common semiology in fronto-limbic seizures and in parasomnias. A neuroethologic approach.

Central pattern generators (CPGs) are genetically determined neuronal aggregates in the mesencephalon, pons and spinal cord subserving innate motor behaviours essential for survival (feeding, locomotion, reproduction etc.). In higher primates CPGs are largely under neocortical control. We describe how certain motor events observed in parasomnias and epileptic seizures could have similar features and resemble motor behaviours, which can be the expression of the same CPG. Both epilepsy and sleep can lead to a temporary loss of control of neomammalian cortex that facilitates through a common platform (arousal) the emergences of stereotyped inborn fixed action patterns. Therefore we suggest that, independently from the nature of the trigger, be it a seizure or a parasomnia, the same CPGs can be involved, “caught up”, leading to a common motor semiology (the “Carillon theory”).

Permutation entropy to detect vigilance changes and preictal states from scalp EEG in epileptic patients. A preliminary study

Permutation entropy (PE) was recently introduced as a very fast and robust algorithm to detect dynamic complexity changes in time series. It was also suggested as a useful screening algorithm for epileptic events in EEG data. In the present work, we tested its efficacy on scalp EEG data recorded from three epileptic patients. With a receiver operating characteristics (ROC) analysis, we evaluated the separability of amplitude distributions of PE resulting from preictal and interictal phases. Moreover, the dependency of PE on vigilance state was tested by correlation coefficients. A good separability of interictal and preictal phase was found, nevertheless PE was shown to be sensitive to changes in vigilance state. The changes of PE during the preictal phase and at seizure onset coincided with changes in vigilance state, restricting its possible use for seizure prediction on scalp EEG; this finding however suggests its possible usefulness for an automated classification of vigilance states.SommarioÈ stato recentemente introdotto un algoritmo denominato Permutation Entropy (PE) a cui gli autori Bandt e Pompe (2002) attribuiscono due caratteristiche interessanti: la robustezza e la relativa rapidità di implementazione, proprietà entrambe utili nell’individuazione delle variazioni di complessità in serie temporali. Sulla scia di un iniziale ottimismo, la PE è stata suggerita come un possibile ausilio di ricerca su dati elettroencefalografici relativi a crisi epilettiche. Un primo obiettivo del nostro studio era testare l’efficacia dell’algoritmo, su dati elettroencefalografici di scalpo, registrati da 3 pazienti epilettici. Mediante l’applicazione di una ROC (Receiver Operating Characteristics) analisi abbiamo valutato la separabilità delle distribuzioni delle ampiezze di PE, rispettivamente per la fase preictale per quella interictale, su ogni registrazione di scalpo. Il secondo obiettivo è stato quello di indagare le eventuali correlazioni sussistenti fra l’andamento della PE e gli stati di vigilanza. Troviamo una buona separabilità fra le curve di dati preictali e interictali di ciascun paziente, seppure è evidente che la PE sia sensibile al cambio di stati di vigilanza, poiché spesso l’inizio di un evento accessuale era concomitante a cambi di stati di vigilanza. Alla luce di queste osservazioni, concludiamo che al momento non è possibile valutare l’affidabilità della PE come algoritmo predittore di crisi su dati elettroencefalografici di superficie, mentre appare sicuramente più attendibile come classificatore automatico degli stati di vigilanza.

Cognition and Paroxysmal EEG Activities: From a Single Spike to Electrical Status Epilepticus during Sleep

Summary:u2002 Epileptic EEG paroxysms can interfere with cognitive processes producing transitory effects, such as those related to a single spike, as well as long‐lasting effects, such as in electrical status epilepticus during slow‐wave sleep (ESES). Focal spike‐related disruption of cortical functions can produce transitory cognitive impairment, with neuroanatomical specificity between the site of the epileptic focus and the impaired cognitive tasks. ESES represents a model of the long‐lasting effects of continuous spike‐wave activity on higher cortical functions. The duration of ESES and the localization of interictal foci seem to play a major role in influencing the degree and type of cognitive dysfunction, suggesting that the ESES clinical picture results from a localized disruption of EEG activity caused by focal epileptic activity during sleep. Recently, Giulio Tononis group reported that a local increase of slow‐wave activity (SWA) during sleep after learning is associated with improved performance of the learned task after sleep (Huber et al., Nature 2004;430:78–81). On the basis of these findings, we can speculate that prolonged focal epileptic activity during sleep (as occurring in ESES) interferes with local SWA at the site of the epileptic focus, impairing the neural processes and, possibly, the local plastic changes associated with learning and other cognitive functions.

Sudden unexpected death in epilepsy (SUDEP) and sleep

The risk of sudden unexpected death is considered to be notably higher in patients with epilepsy with respect to the general population. Sudden unexpected death in epilepsy (SUDEP) is probably caused by the peri-ictal concurrence of a number of different predisposing and precipitating factors. Among these, the presence of a seizure before the fatal event is the only feature that seems to be constantly present. Different mechanisms, namely cardiac arrhythmias, respiratory dysfunctions, dysregulation of systemic or cerebral circulation have been suggested as potential physiopathological mechanisms. Moreover, clinical data seem to suggest that SUDEP could occur preferentially during sleep. In order to assess a possible relationship between sleep and SUDEP, we have analyzed studies in which sufficient information about the circumstances of deaths was available. Our analysis confirms that the relationship between sleep and SUDEP is not given by chance as the percentage of possible sleep-related SUDEP is higher than 40% in the majority of studies. We will discuss the possible longstanding and precipitating mechanisms involved in the interaction between sleep and epilepsy likely to favour SUDEP occurrence. In this perspective, possible preventive measures will be hypothesized.

Facial emotion recognition impairment in chronic temporal lobe epilepsy.

Purpose:u2002 To evaluate facial emotion recognition (FER) in a cohort of 176 patients with chronic temporal lobe epilepsy (TLE).

Impaired fear processing in right mesial temporal sclerosis: a fMRI study

Lesion and neuroimaging studies have demonstrated that the mesial temporal lobe is crucial for recognizing emotions from facial expressions. In humans, bilateral amygdala damage is followed by impaired recognition of facial expressions of fear. To evaluate the influence of unilateral mesial temporal lobe damage we examined recognition of facial expressions and functional magnetic resonance (fMRI) brain activation associated with incidental processing of fearful faces in thirteen mesial temporal lobe epilepsy (MTLE) patients (eight with right MTLE, five with left MTLE). We also examined the effect of early versus later damage, comparing subjects with hippocampal-amygdalar sclerosis (MTS) and seizures occurring before five years of age to epilepsy patients with late onset seizures. Fourteen healthy volunteers participated as controls. Neuropsychological testing demonstrated that the ability of right MTLE patients to recognize fearful facial expressions is impaired. Patients with early onset of seizures were the most severely impaired. This deficit was associated with defective activation of a neural network involved in the processing of fearful expressions, which in controls and left MTLE included the left inferior frontal cortex and several occipito-temporal structures of both hemispheres.

Interhemispheric transfer following callosotomy in humans: Role of the superior colliculus

It is now common knowledge that the total surgical section of the corpus callosum (CC) and of the other forebrain commissures prevents interhemispheric transfer (IT) of a host of mental functions. By contrast, IT of simple sensorimotor functions, although severely delayed, is not abolished, and an important question concerns the pathways subserving this residual IT. To answer this question we assessed visuomotor IT in split-brain patients using the Poffenberger paradigm (PP), that is, a behavioral paradigm in which simple reaction time (RT) to visual stimuli presented to the hemifield ipsilateral to the responding hand is compared to stimuli presented to the contralateral hemifield, a condition requiring an IT. We tested the possibility that the residual IT is mediated by the collicular commissure interconnecting the two sides of the superior colliculus (SC). To this purpose, we used short-wavelength visual stimuli, which in neurophysiological studies in non-human primates have been shown to be undetectable by collicular neurons. We found that, in both totally and partially callosotomised patients, IT was considerably longer with S-cone input than with L-cone input or with achromatic stimuli. This was not the case in healthy participants in whom IT was not affected by color. These data clearly show that the SC plays an important role in IT of sensorimotor information in the absence of the corpus callosum.

EEG Diagnostic Procedures and Special Investigations in the Assessment of Photosensitivity

Summary:u2003 Photosensitivity can be assessed in laboratory conditions with different methods. The most common procedure is intermittent photic stimulation (IPS), whose effectiveness in detecting photosensitivity depends largely on methodologic aspects. Although IPS is a widespread and routinely used procedure in EEG laboratories, only recently has a standardization of the IPS method been proposed. Furthermore, other modalities of visual stimulation, including pattern stimulation and low‐luminance visual stimulation (LLVS), have proven their usefulness in detecting photosensitivity. We provide an overview of the methodologic aspects and clinical implications of these procedures, resulting from recent consensus meetings, and the diagnostic usefulness of the LLVS technique in photosensitive individuals whose seizures are triggered particularly by television images. Finally, we briefly illustrate the potential of advanced neurophysiological (magnetoencephalography and high‐density EEG) and functional imaging techniques in the investigation of the pathophysiologic mechanisms underlying photosensitivity.

Video-game epilepsy: a European study.

With the introduction of Nintendo video‐games on a large scale, reports of children having seizures while playing suggested a possible specific, provocative factor. Although 50% of the photosensitive patients are also sensitive to a 50‐Hz television, nonphotosensitive patients with a history of videogame seizures were described as well. The question arises whether this is a mere coincidence, provoked by fatigue and stress, is related to the reaction to the television screen itself, or depends on the movement and color of the pictures of this specific game.