Spatiotemporal source analysis in scalp EEG vs. intracerebral EEG and SPECT: a case study in a 2-year-old child.

OBJECTIVE: This case study aims to demonstrate that spatiotemporal spike discrimination and source analysis are effective to monitor the development of sources of epileptic activity in time and space. Therefore, they can provide clinically useful information allowing a better understanding of the pathophysiology of individual seizures with time- and space-resolved characteristics of successive epileptic states, including interictal, preictal, postictal, and ictal states. METHODS: High spatial resolution scalp EEGs (HR-EEG) were acquired from a 2-year-old girl with refractory central epilepsy and single-focus seizures as confirmed by intracerebral EEG recordings and ictal single-photon emission computed tomography (SPECT). Evaluation of HR-EEG consists of the following three global steps: (1) creation of the initial head model, (2) automatic spike and seizure detection, and finally (3) source localization. During the source localization phase, epileptic states are determined to allow state-based spike detection and localization of underlying sources for each spike. In a final cluster analysis, localization results are integrated to determine the possible sources of epileptic activity. The results were compared with the cerebral locations identified by intracerebral EEG recordings and SPECT. RESULTS: The results obtained with this approach were concordant with those of MRI, SPECT and distribution of intracerebral potentials. Dipole cluster centres found for spikes in interictal, preictal, ictal and postictal states were situated an average of 6.3mm from the intracerebral contacts with the highest voltage. Both amplitude and shape of spikes change between states. Dispersion of the dipoles was higher in the preictal state than in the postictal state. Two clusters of spikes were identified. The centres of these clusters changed position periodically during the various epileptic states. CONCLUSION: High-resolution surface EEG evaluated by an advanced algorithmic approach can be used to investigate the spatiotemporal characteristics of sources located in the epileptic focus. The results were validated by standard methods, ensuring good spatial resolution by MRI and SPECT and optimal temporal resolution by intracerebral EEG. Surface EEG can be used to identify different spike clusters and sources of the successive epileptic states. The method that was used in this study will provide physicians with a better understanding of the pathophysiological characteristics of epileptic activities. In particular, this method may be useful for more effective positioning of implantable intracerebral electrodes.

Heterotopia associated with hippocampal sclerosis: an under-recognized cause of early onset epilepsy in children operated on for temporal lobe epilepsy.

PURPOSE: The aim of this study is to report on 52 children operated on for pharmacoresistant temporal lobe epilepsy, with special emphasis on histopathology and correlation with clinical features. METHODS: Charts were retrospectively analyzed. All children underwent comprehensive clinical, electrophysiological and radiological investigations before surgery. Surgical procedures were tailored according to scalp, foramen ovale and eventually depth electrode recordings. Histopathology was compared with clinical variables (χ (2) and Fisher's exact tests). Outcome was evaluated using the Engel scale. RESULTS: Developmental tumor was found in 14 cases, malformation of cortical development (MCD) in 26, isolated hippocampal sclerosis (HS) in 5 and gliosis in 7. Dual pathology (DP) affected 18 patients and the main extrahippocampal lesion consisted of microscopic sub-cortical heterotopias (HS-HT) for 15 patients who shared a particular clinical pattern: a history of febrile seizures (FS) and/or brain injury, early onset of epilepsy without latent period from FS to the first temporal seizure, and a particularly good outcome following surgery. CONCLUSION: In our pediatric temporal lobe surgery series, the prevalence for MCD and for DP was higher than in adult series. Age at seizure onset depends on pathology, and is earlier when involving the neocortex rather than only the hippocampus. We identify the association HS-HT (the most frequent DP in this series), with particular clinical features.

[Epilepsy surgery during infancy and early childhood in France]. / Chirurgie de l'épilepsie de l'enfant et du nourrisson en France.

BACKGROUND AND PURPOSE: We present the epilepsy surgery activity in infants and children at the Fondation Rothschild Hospital, the main center dedicated to this activity in France. METHOD: A prospective study was conducted from 2003 to 2007 based on three populations: (1) children selected as candidates for surgery, (2) children undergoing presurgical evaluation and (3) children undergoing surgical procedures for epilepsy. RESULTS: Children selected as candidates for surgery: 304 children were referred and discussed by our multidisciplinary staff. They came from Paris and its suburbs (40%), the provinces (43%) or from other countries (14%). Sixty-one percent of them were included in our surgery program and 24% were excluded. Sixty-one percent of them were under 10 years of age. Children undergoing presurgical evaluation: 296 children were recorded: 140 EEG (47%), 46 with foramen ovale electrodes (16%) and 110 with invasive recording techniques (37%). Seventy percent of these children were under 10 years of age. Children undergoing surgical procedures: 316 children underwent surgery; 68% of them were under 10 years of age. The surgical procedures were focal resection (136 children), vertical parasagittal hemispherotomy (77 children), resection and or disconnection for hypothalamic hamartoma (69 children) and 34 had palliative surgery (callosotomy or vagal nerve stimulation). CONCLUSION: Eighty to 100 children undergo surgery each year in our department for drug-resistant partial epilepsy; 70% of them are less than 10 years of age. This activity is part of a network of pediatric neurologists who are deeply involved in treatment of severe epilepsy in children.

[Electrophysiological investigations in childhood epilepsy surgery]. / Explorations électroencéphalographiques préchirurgicales de l'enfant.

Epilepsy surgery in children is a functional surgery: its goal is to perform the resection of the epileptic brain tissue while sparing the eloquent cortex. Prolonged scalp video-EEGs allow recording of all types of seizures and play a crucial role in localizing the epileptogenic zone. Furthermore, EEG data correlation with clinical and radiological findings provides a guide for the surgical strategy: either resection without further investigations or an invasive recording procedure. In prehemispherotomy evaluation, EEG recordings confirm that limited resections are not indicated and demonstrate that the opposite hemisphere is not involved. If invasive recordings are needed, they consist in foramen ovale electrode insertion, which provides valuable information in mesial temporal lobe epilepsy, stereoelectroencephalography for children older than two years, and subdural grids associated with depth electrodes in infants or when the eloquent areas need to be carefully investigated. Such investigations allow tailoring surgery to each child.

[Long-term outcome after hemispheric disconnection]. / Evaluation à long terme des déconnexions hémisphériques.

Hemispheric disconnection has been largely proposed for patients with severe epilepsy associated with a congenital or acquired hemispheric cerebral pathology. The classical procedure of anatomical hemispherectomy was progressively abandoned by neurosurgeons in order to avoid postoperative complications since then hemispherotomy techniques have been developed. Globally, with hemispheric disconnection, the rate of patients becoming seizure-free has been between 50 and 80%. The factors affecting seizure control have not been completely elucidated, but several authors suggested that differences in etiology as well as the hemispheric disconnection technique used may partially explain this variability. The percentage of seizure-free patients is higher with hemispherotomy techniques and in the group of patients with Rasmussen encephalitis, Sturge-Weber syndrome, and vascular insults. Depending on overall long-term progression, there is an improvement compared to preoperative status even if children exhibit heterogenous abilities. The lowest scores are observed for motor skills but communication and socialization are relatively well-preserved and strongly related to the duration of epilepsy: the longer the duration, the lower the scores were. Neuropsychological outcome following hemispheric disconnection makes it possible to study the development of hemispheric specialization during infancy and to provide information on cognitive recovery. Cerebral reorganization has been proved to exist in motor and language recovery. Ipsilateral corticospinal pathways seem to be involved in the movement of hemiplegic limbs. Everyday language can be supported by both hemispheres, but there is an early hemispheric specialization of the left hemisphere according to metaphonologic abilities.

[Surgery for intractable focal epilepsy in children]. / Chirurgie de l'épilepsie chez l'enfant.

Surgery of drug resistant epilepsy in children is a functional surgery which aims at the suppression of the epileptogenic focus. The surgical decision is adopted or rejected as a result of the clinical examination and complementary investigations following a multidisciplinary discussion in which the benefit-risk ratio is being carefully weighed. The objective of the presurgical investigations, dominated by scalp-recorded video-electroencephalography and magnetic resonance imaging, is the localization of the epileptogenic focus. The invasive surgical investigations with intracranial electrode placement are indicated when the limits of a planned resection have to be defined precisely or when the focus is located nearby a functionally eloquent region (sensori-motor and language region). Their identification is possible by means of electrical stimulation. Two methods of exploration are available: The combination of subdural and intracerebral electrode placement through craniotomy and the stereotactic placement of intracerebral depth electrodes (Stereo-EEG). The choice of either of these two methods depends on the child's age and on the topography of the epileptogenic focus. Surgery can be either palliative, with the purpose of reducing the intensity and/or the frequency of a certain seizure type (callosotomy, multiple subpial transsections) or curative, aiming at a suppression of the epileptogenic focus through a resective or a disconnective surgical procedure. We have operated on a population of 148 children and infants between 3 months and 10 years of age during the years 1993 to 2001: In the infant group, dysplastic lesions represented the predominant etiology. In the age group of 3 to 10 years, the underlying pathology was more distributed (dysplastic lesions, epileptogenic tumors, Rasmussen's encephalitis, hypothalamic hamartomas). Extratemporal focal resections required, in the majority of cases, an invasive preoperative exploration and hemispherotomy was frequent in this group (44 p. 100). Sixty-seven percent of the children were seizure-free, with an acceptable morbidity rate, primarily due to shunt placement following hemispherotomy in children with dysplastic lesions. Our preliminary results concerning quality of life and socialization are encouraging and favor surgical treatment at an early stage.

Behavioural epileptic seizures: a clinical and intracranial EEG study in 8 children with frontal lobe epilepsy.

We report on eight children who underwent prolonged invasive video-EEG recording (IC-EEG) for intractable frontal lobe epilepsy and whose seizures consisted of behaviour changes. Seizures were recorded on a BMSI computer with 128 channels connected to the Gotman software of a stellate system; their identification was made both clinically and by automatic detection of paroxysmal electrical events. Behavioural epileptic seizures (BES) consisted of various clinical signs comprising mood change, sudden agitation, unexpected quietness, and subtle change of awareness or awakening. In 2 patients, seizures consisted in repetitive movements that we referred to as epileptic stereotypes. BES came from the prefrontal areas of the brain. Most of them were overlooked or misdiagnosed as behavioural manifestations, especially in children with mental deficiency and autistic features. Given the improvement of behaviour and mental functions following surgery, we assume that BES may contribute to generate mental and behavioural dysfunction.

Ictal SPECT in children with epilepsy: comparison with intracranial EEG and relation to postsurgical outcome.

In order to validate the ability of ictal single photon emission computed tomography (SPECT) to localize the epileptogenic zone (EZ) in children, we compared in 20 patients aged from 10 months to 17 years (mean 6.5 years) the topography of the area of increased ictal perfusion (IPA), determined on the basis of ictal minus interictal scan values, with that of the EZ determined by intracranial EEG recordings and assessed its relationship with the postsurgical outcome. Eighteen patients had symptomatic epilepsy and 10 had extratemporal epilepsy. All patients except one had an ictal injection (mean time lag from clinical seizure onset was 18 s). Ictal and interictal SPECT images were successively co-registered, normalized, subtracted, smoothed and superimposed on MRI. All patients with ictal injection exhibited one or several IPAs. The topography of the 'highest' IPA, i.e. the maximal cerebral blood flow (CBF) change between ictal and interictal SPECT, significantly colocalized with the site of onset of the discharge, and that of the lower IPAs with that of the area of propagation (P < 0.0001). At a threshold of 30% of the maximal CBF change, the IPAs detected the onset of the discharge with a sensitivity of 0.80 and a specificity of 0.70. The highest IPA localized the EZ in 12 out of 15 patients. In the three others it missed the EZ and showed the area of propagation because of rapid seizure propagation or of infraclinical seizure onset. Among the patients with favourable surgery outcome, the highest IPA colocalized with the resected area in 70% of cases. Ictal SPECT could therefore plays an important role as a non-invasive presurgical method of investigation by optimizing the placement of intracranial electrodes, thus improving the postsurgery outcome of paediatric partial epilepsy.

Hot water epilepsy: a benign and unrecognized form.

Hot water epilepsy is a reflex epilepsy. Seizures are provoked by hot water, and result from the association of both cutaneous and heat stimuli. Described mainly in India and Japan, the condition seems to be rare in Europe, where it occurs in young children. We report five infants aged from 6 months to 2 years. They had brief seizures during bathing with activity arrest, hypotonia, and vasoactive modification; clonic movements were observed. A simple treatment-decreasing the bath temperature-can be sufficient. Sometimes an antiepileptic drug is required. Seizure course and psychomotor development are favorable. Hot water epilepsy is a benign form of epilepsy. Its incidence could be underestimated because of confusion with febrile convulsions, vagal fits, or aquagenic urticaria.

[Hot water epilepsy: a benign and underestimated form]. / L'épilepsie à l'eau chaude: une forme bénigne et méconnue.

BACKGROUND: Hot water epilepsy belongs to the group of reflex epilepsies. Seizures are provoked by hot water, due to the association of both cutaneous and heat stimuli. Described mainly in India and Japan, it seems to be rare in Europe where it occurs in young children. CASE REPORTS: Five infants aged between 6 months to 2 years had seizures during bathing with activity arrest, hypotonia and vasoactive modification. Sometimes clonic movements could be observed. The diagnosis was confirmed by EEG recorded during bath in the fives cases, with video for two of them. The course of the seizures and of the psychomotor development were favorable. CONCLUSION: Hot water epilepsy is a benign epilepsy. Its incidence could be underestimated because seizures can be confused with febrile convulsions or vagal fits.

[Surgery and epilepsy]. / Chirurgie et épilepsie.

Corpus callosotmy was introduced in 1940 as a palliative treatment for generalized epilepsies. The improvement of the surgical technique, and the simplification of the initial "total commissurotomy" made that procedure proposed in order to decrease the frequency and the severity of the seizures occurring in the secondary geralzed epilepsies. However the indication criteria remain unclear, due to the difficulty for analysing the results and the feterogenity of the series. A careful selection requiring a comprehensive epilepsy team remains mandatory despite the relative simplicity of the procedure.

[Problems related to neurosurgical treatment of epilepsy in children]. / Problèmes posés par la neurochirurgie de l'épilepsie de l'enfant.

Neurosurgery of epilepsy in children has undergone rapid development during the past decade. This was justified by the high incidence of intractable epilepsy and its consequences on cognitive development. Any decision in the area of surgery must take in account specific etiology and the rapid maturation of the infant's brain. As in adulthood, both the epileptogenic and the functional zones must be identified, but this is a challenge when the brain is not mature and the functions not yet developed. In addition, the ability to recover must be determined. At the present time no precise methodology can be advised for presurgical work-up and surgical indications.

Twenty-four-hour ambulatory EEG monitoring in infantile spasms.

Twenty-four-hour ambulatory EEG (AEEG) recordings were performed in 74 infants with West Syndrome (WS) who had not received corticosteroids before the recording. EEG analysis was performed visually for interictal background activity as well as for ictal events: spasms (isolated or in clusters) and other seizures either generalized or partial. Six hundred fifty-four seizures were recorded in 67 patients. Partial seizures (PS) were noted in 31 infants (51% of symptomatic WS cases, 33% of cryptogenic WS cases). In 14 patients, PS were immediately followed by a cluster of spasms consisting of a single ictal event. Patients with PS had an asymmetrical interictal background activity in 85% of cases, with no return to hypsarrhythmia between spasms in a given cluster. AEEG is a reliable method to detect and analyze ictal events in infants with WS. In this population, patients with unfavorable outcome of both epilepsy and psychomotor development have PS. Therefore, the existence of PS may contribute to etiologic diagnosis and prognostic evaluation.

Progabide for previously untreated absence epilepsy.

Ten patients suffering from absence epilepsy and showing generalized spike-wave paroxysms in the EEG were treated by progabide monotherapy. Findings concerning clinical data and serial 24 h long-term EEG recordings were compared for the pre-treatment and treatment period. The average total spike-wave duration in 24 h decreased slightly from 810 sec to 699 sec; at follow-up, in 4 cases this trend was found to have reversed. Concerning seizure frequency, a marked anticonvulsant effect could not be confirmed; an initial slight anti-absence activity in some cases seemed to be subjected to the development of tolerance. Side effects were rarely observed and if so were not severe.