Agnès Trébuchon

Frontal lobe seizures: From clinical semiology to localization

Frontal lobe seizures are difficult to characterize according to semiologic and electrical features. We wished to establish whether different semiologic subgroups can be identified and whether these relate to anatomic organization.

Source localization of scalp-EEG interictal spikes in posterior cortex epilepsies investigated by HR-EEG and SEEG

Purpose:  To determine the validity of scalp‐electroencephalography (EEG)‐interictal spike (IIS) source localization in posterior cortex epilepsies (PCE).

Intra-Cranial Recordings of Brain Activity During Language Production

Recent findings in the neurophysiology of language production have provided a detailed description of the brain network underlying this behavior, as well as some indications about the timing of operations. Despite their invaluable utility, these data generally suffer from limitations either in terms of temporal resolution, or in terms of spatial localization. In addition, studying the neural basis of speech is complicated by the presence of articulation artifacts such as electro-myographic activity that interferes with the neural signal. These difficulties are virtually absent in a powerful albeit much less frequent methodology, namely the recording of intra-cranial brain activity (intra-cranial electroencephalography). Such recordings are only possible under very specific clinical circumstances requiring functional mapping before brain surgery, most notably in patients that suffer from pharmaco-resistant epilepsy. Here we review the research conducted with this methodology in the field of language production, with explicit consideration of its advantages and drawbacks. The available evidence is shown to be diverse, both in terms of the tasks and the cognitive processes tested and in terms of the brain localizations being studied. Still, the review provides valuable information for characterizing the dynamics of the neural events occurring in the language production network. Following modality specific activities (in auditory or visual cortices), there is a convergence of activity in superior temporal sulcus, which is a plausible neural correlate of phonological encoding processes. Later, between 500 and 800 ms, inferior frontal gyrus (around Broca’s area) is involved. Peri-rolandic areas are recruited in the two modalities relatively early (200–500 ms window), suggesting a very early involvement of (pre-) motor processes. We discuss how some of these findings may be at odds with conclusions drawn from available meta-analysis of language production studies.

Seizure-onset patterns in focal cortical dysplasia and neurodevelopmental tumors: Relationship with surgical prognosis and neuropathologic subtypes.

The study of intracerebral electroencephalography (EEG) seizure‐onset patterns is crucial to accurately define the epileptogenic zone and guide successful surgical resection. It also raises important pathophysiologic issues concerning mechanisms of seizure generation. Until now, several seizure‐onset patterns have been described using distinct recording methods (subdural, depth electrode), mostly in temporal lobe epilepsies or with heterogeneous neocortical lesions.

Intraoperative monitoring in pediatric orthopedic spinal surgery: three hundred consecutive monitoring cases of which 10% of patients were younger than 4 years of age.

Study Design. Analysis of a prospective series of 300 consecutive cases undergoing intraoperative monitoring in pediatric orthopedic spinal surgery, of which 10% were children younger than 4 years. Objective. Determine feasibility and performance of intraoperative monitoring in children younger than 4 years. Analyze distinct physiopathologic mechanisms of relevant alerts. Summary of Background Data. There are few studies in the literature concerning the intraoperative monitoring of children younger than 4 years. During childhood, the development of sensori-motor pathways is dominated by two coexisting phenomena, which have opposite effects: maturation decreasing latencies and height increasing them. Methods. We used intraoperative somatosensory-evoked potentials and neurogenic mixed evoked potentials with a flexible bipolar epidural electrode. Uniform total intravenous anesthesia was used. Results. Values of sensitivity and specificity of the monitoring showed slight differences between patients younger than 4 years versus older patients. There was no false-negative outcome. Various tendencies were highlighted. There were more true positive alerts for secondary etiologies than for idiopathic ones, for revision spinal surgeries than for index ones, and for boys than for girls. There were no more true positive alerts for children younger than 4 years than for older patients whereas the proportion of hemivertebrae was obviously greater for the younger group. Relevant monitoring alerts were more frequent in case of kyphoscoliosis. This is highlighted in case reports. Conclusion. In some cases of kyphoscoliosis, during a posterior-based vertebral column resection, monitoring changes were corrected by positioning a rod that allowed correction of the position of the spine in the sagittal plane. Intraoperative spinal cord monitoring can be performed in children younger than 4 years and allows real-time assessment of spinal functional integrity.

How familiarization and repetition modulate the picture naming network.

A common strategy to reveal the components of the speech production network is to use psycholinguistic manipulations previously tested in behavioral protocols. This often disregards how implementation aspects that are nonessential for interpreting behavior may affect the neural response. We compared the electrophysiological (EEG) signature of two popular picture naming protocols involving either unfamiliar pictures without repetitions or repeated familiar pictures. We observed significant semantic interference effects in behavior but not in the EEG, contrary to some previous findings. Remarkably, the two protocols elicited clearly distinct EEG responses. These were not due to naming latency differences nor did they reflect a homogeneous modulation of amplitude over the trial time-window. The effect of protocol is attributed to the familiarization induced by the first encounter with the materials. Picture naming processes can be substantially modulated by specific protocol requirements controlled by familiarity and, to a much lesser degree, the repetition of materials.

18FDG-PET in different subtypes of temporal lobe epilepsy: SEEG validation and predictive value.

The objective of the study was to characterize interictal 18‐fluorodeoxyglucose–positron emission tomography (18FDG‐PET) whole‐brain voxel‐based metabolic patterns among distinct subtypes of temporal lobe epilepsy (TLE), as defined by stereo–electroencephalography (SEEG) and to determine predictive value of PET result on postoperative outcome.

Anti–tumor necrosis factor alpha therapy (adalimumab) in Rasmussen's encephalitis: An open pilot study

Rasmussens encephalitis (RE) is a severe chronic inflammatory brain disease affecting one cerebral hemisphere and leading to drug‐resistant epilepsy, progressive neurologic deficit, and unilateral brain atrophy. Hemispherotomy remains the gold standard treatment but causes permanent functional impairment. No standardized medical treatment protocol currently exists for patients prior to indication of hemispherotomy, although some immunotherapies have shown partial efficacy with functional preservation but poor antiseizure effect. Some studies suggest a role for tumor necrosis factor alpha (TNF‐α) in RE pathophysiology.

Reversible antisocial behavior in ventromedial prefrontal lobe epilepsy

Frontal lobe dysfunction is known to be associated with impairment in social behavior. We investigated the link between severe pharmacoresistant frontal lobe epilepsy and antisocial trait. We studied four patients with pharmacoresistant epilepsy involving the prefrontal cortex, presenting abnormal interictal social behavior. Noninvasive investigations (video-EEG, PET, MRI) and intracerebral recording (stereoelectroencephalography (SEEG)) were performed as part of a presurgical assessment. Comprehensive psychiatric and cognitive evaluation was performed pre- and postoperatively for frontal lobe epilepsy, with at least 7years of follow-up. All patients shared a characteristic epilepsy pattern: (1) chronic severe prefrontal epilepsy with daily seizures and (2) an epileptogenic zone as defined by intracerebral recording involving the anterior cingulate cortex, ventromedial PFC, and the posterior part of the orbitofrontal cortex, with early propagation to contralateral prefrontal and ipsilateral medial temporal structures. All patients fulfilled the diagnostic criteria (DSM-IV) of antisocial personality disorder, which proved to be reversible following seizure control. Pharmacoresistant epilepsy involving a prefrontal network is associated with antisocial personality. We hypothesize that the occurrence of frequent seizures in this region over a prolonged period produces functional damage leading to impaired prefrontal control of social behavior. This functional damage is reversible since successful epilepsy surgery markedly improved antisocial behavior in these patients. The results are in line with previous reports of impairment of social and moral behavior following ventromedial frontal lobe injury.

Electrical Stimulation for Seizure Induction and Functional Mapping in Stereoelectroencephalography

Summary: The challenge in epilepsy surgery is to remove the epileptogenic zone without compromising postoperative function. Electrical stimulation (ES) was developed to identify with greater anatomical and physiological precision cortical structures essential to language and motor function. Because the language network is widely distributed in the left (dominant) hemisphere, and often varies among patients, brain mapping should delineate eloquent areas at the individual level. Although ES for language is commonly performed during a presurgical investigation, the procedure remains nonstandardized among centers, and differences between grids and intracerebral depth electrodes (stereoelectroencephalography) should be taken into account when comparing results from different series. Electrical simulation exerts a complex summation effect in a given volume of brain tissue; the net result may be difficult to predict because this depends on methodological and physiological factors as follows: stimulation parameters, type of electrodes used, tasks used, presence or not of an after-discharge. We discuss in the present article some methodological aspects of the stimulation procedure influencing functional mapping because it pertains in particular to language mapping. In stereoelectroencephalography, the other goal of ES is to trigger seizures. Because seizures develop in neural networks that are imperfectly sampled by intracerebral electrodes, spontaneous seizure recording is not always sufficient to properly localize the epileptogenic zone. The rationale for performing ES is based on the electrophysiological distinction between local/regional after-discharge and seizure networks. A different response to ES-induced seizures can be seen for supra- and infra-sylvian epilepsies. The procedures for triggering seizures and for functional mapping should be performed in conjunction to answer the fundamental question whether or not there is a spatio-temporal overlap between the epileptogenic and the functional network. The exploration of both networks through stimulation exemplifies the importance of anatomo-electro-clinical correlations in stereoelectroencephalography.