The electrical discharge of neurons associated with seizure activity stimulates a marked rise in cerebral metabolic activity. Estimates from animal experiments indicate that energy utilization during seizures increases by more than 200", while tissue adenosine triphosphate (ATP) levels remain at more than 95" of control, even during prolonged status epilepticus. The brain generally withstands the metabolic challenge of seizures quite well because enhanced cerebral blood flow delivers additional oxygen and glucose. Mild to moderate degrees of hypoxemia that commonly accompany seizures are usually harmless. However, severe seizures and status epilepticus can sometimes produce an imbalance between metabolic demands and cerebral perfusion, especially if severe hypotension or hypoglycemia is present. A marked increase in glutamate release, which occurs during a prolonged seizure, is likely to result in the activation of all types of glutamate receptors. Although kainic acid produces seizures in the immature brain, it produces little cytotoxicity.
Your search for all content returned 180 results
This chapter presents a brief review of the enzymes, transporters, and cofactor producers of the urea cycle. Seizures have long been associated with urea cycle disorders (UCDs), thought to be caused by high levels of ammonia. Furthermore, the brain damage obtained during metabolic crisis has been thought to damage critical structures, leading to epilepsy after the conclusion of the crisis. The first and most critical step of successful treatment of UCDs is recognition. Neurologic monitoring is an essential part of the emergency management of UCDs. The neurological abnormalities observed in patients with urea cycle defects are vast. Controlling ammonia levels by dialysis and complementary medication are needed. EEG monitoring should be initiated early, as this may be very useful for clinical management and indication of untreated metabolic crises. Furthermore, aggressive treatment of clinical and subclinical seizure activity may be helpful in optimizing outcomes for these patients.Source:
Stereo electroencephalography (
EEG) has become the predominant method across the world to invasively explore patients with focal epilepsy who are potential candidates for resective surgery. This required many epilepsy centers to introduce major workflow adaptations, investment in surgical and imaging technologies, and seek training in placement and interpretation of depth electrodes recordings. It became evident that a comprehensive, practical textbook outlining the different steps and nuances of the methodology was missing. This book covers all practical aspects of stereo EEGand is a quintessential staple for anybody learning and working in the field of epilepsy surgery, including adult and pediatric epileptologists and neurophysiologists, functional neurosurgeons, technologists, and trainees in these areas. The book is a complete and practical guide to thinking and doing stereoelectroencephalography ( SEEG) which will be a solid reference to practitioners around the world. Almost all chapters feature illustrative cases to explain specific aspects and key concepts of the SEEGmethodology. The section covering the practical approach to specific epilepsy syndromes includes voice-over slide presentations demonstrating the process of a systematic patient discussion, hypothesis generation, and electrode planning followed by data interpretation and delineation of surgical resection. The book starts with the historical background and principles of stereo EEGand discusses the role of the noninvasive evaluation and patient selection. It describes technical aspects of electrodes, multimodal data coregistration, and guidelines for invasive monitoring. The book then presents the conceptual framework of stereo EEGfollowed by surgical aspects of stereo EEGelectrode placement covering robotic and frame-based approaches, specific pediatric aspects, and potential complications. It describes data interpretation of physiologic, interictal, and ictal epileptic activity, and outlines conceptual and methodological aspects of electrical stimulation mapping. The book ends with discussing surgical procedures to remove the epileptogenic zone and a review of seizure and cognitive outcome with stereo EEG.
Surgical resection in frontal lobe epilepsy (
FLE) is considered less successful than in temporal lobe epilepsy ( TLE), with positive seizure outcome situated at around 50% in more recent studies, although great variability exists depending on series. Such variability concerns also prognostic factors, such as the absence of a visible lesion on MRIwhich is often reported within negative outcome predictors, namely in series without systematic use of stereoelectroencephalography ( SEEG). The first challenge of SEEGin FLEis being able to formulate appropriate hypotheses about the likely sublobar organization of seizures. The next challenge is to perform adequate sampling of the presumed epileptogenic zone ( EZ) within the large volume of the lobe. This chapter briefly reviews some anatomo-functional aspects, then focuses on different types of FLSsaccording to a sublobar organization, with illustrative cases to describe clinical and SEEGfeatures and to provide some practical tips about implantation strategies.
The goal of intracerebral depth electrode electroencephalography (
EEG) recording is to record seizures and the propagation pattern of the seizures in order to delineate the extent of the epileptogenic zone ( EZ). This chapter focuses on the interpretation of IEDsrecorded by chronically implanted depth electrodes and discusses its role in the epilepsy presurgical evaluation. Combining interictal epileptiform discharges ( IEDs) with high frequency oscillations and functional MRIcould potentially increase the value of IEDsin localizing the EZ. Quantitative EEGcould increase efficiency and improve interreader reliability. Ultimately, the usefulness of stereoelectroencephalography IEDsin localization is limited by the areas sampled by depth electrodes, which in turn are driven by where the electrodes are implanted. Fundamental to IEDassessment, therefore, is a set of meaningful hypotheses for the location of the seizure onset zone ( SOZ) prior to electrode implantation.
The main goal of stimulation studies during stereoelectroencephalography (
SEEG) is to trigger habitual seizures, in order to help define the epileptogenic zone ( EZ). Direct electrical stimulation ( DES) studies during SEEGrepresent a key component of methodology for defining the EZ. On the one hand, habitual seizures triggered by stimulation are considered evidence in favor of an epileptogenic role for the stimulated structure, and tend to show cortical epileptic discharge involving the same structures as observed for spontaneous seizures, associated with partial or complete habitual semiology. On the other hand, relatively little work has explored underlying physiological mechanisms and many aspects of DESin general remain poorly understood. This chapter describes clinical approaches to stimulation for seizure induction during SEEGand discusses how stimulation studies can help in defining EZ, as well as highlighting potential pitfalls and areas for future research.
SEEG) was invented in the late 50s by Jean Talairach, a neurosurgeon, and Jean Bancaud, a neuropsychiatrist and electroencephalographer. This method was based upon recording of brain electrical activity by intracerebral electrodes, stereotactically implanted in preidentified cortical and subcortical structures. SEEGoffered high spatial and temporal resolution and a high power of localization. The ultimate objective of SEEGis to provide the surgeon with an integrated view of the epileptogenic process, based on the definition of the epileptogenic zone and its overlap with the lesional zone. SEEGinterpretation was based on ictal anatomo-electro-clinical correlations. A better comprehension of seizure build-up in the human brain led to major pathophysiological advances. SEEG-guided epilepsy surgery was performed only in Paris during the first 25 years, and then adopted in Switzerland and Canada. Its recent worldwide expansion confirms its universally recognized rationality and its perfect adjustment to brain imaging.
Ambulatory electroencephalogram (
AEEG) is a diagnostic extension of standard EEG. It is a well established technique that is best suited for assessing paroxysmal neurological events in patients with epilepsy or in those suspected to have seizures. AEEGuses prolonged overnight EEGmonitoring that takes place in the patient’s habitual environment. Like other techniques recording EEG, AEEGis primarily used to support the clinician’s suspicion of an epilepsy diagnosis. Psychogenic nonepileptic attacks represent a “conversion disorder with seizures”. The diagnosis is based upon clinical features that may resemble convulsive movements of people with epilepsy. Syncope is the most common physiological nonepileptic event encountered that mimics epileptic seizures. Syncope manifests as episodes or “spells” with loss of consciousness. AEEGidentifies, classifies seizure type, and quantifies seizure frequency and duration. Artifact is present in essentially every EEGand may be over-interpreted to be mistaken for an electrographic seizure.Source:
Temporal lobe epilepsy (
TLE) surgery is the most frequent type of surgical treatment offered to patients with drug-resistant focal seizures. Despite the demonstrated superiority of TLEsurgery over medical treatment, long-term surgical outcome remains suboptimal. Temporal plus epilepsy ( TPE), a complex epileptogenic network including the temporal lobe and the closed neighbored structures, represents a major determinant of TLEsurgery failures. Based on the extratemporal areas included in the epileptogenic network, three TPEsubgroups have been identified, that is, a temporo-perisylvian, temporo-frontal and temporo-parieto-occipital subgroup. Invasive recordings, especially stereo electroencephalography ( EEG), are mandatory when TPEis suspected in order to identify the multilobar epileptogenic network. The stereo EEGimplantation strategy is guided by the individual electroclinical hypotheses of the possible temporal plus network. TLEsurgery demonstrated superiority over medical treatment in randomized controlled trials. This chapter discusses the best approach to the invasive investigation of the different TPEsubtypes.
Epilepsy surgery is a powerful treatment that can offer a cure for patients suffering from seizures. The main goal of a presurgical workup is to identify who may benefit from surgery. The first step to this goal is through noninvasive testing. Several so-called “zones of the brain” and their relationship to one another are to be defined and used to help guide an evaluation for surgery. They include the symptomatogenic zone, the irritative zone, the ictal onset zone, the functional deficit zone, the epileptogenic lesion, and the eloquent cortex. The final region, called the “epileptogenic zone” (
EZ), is the ultimate goal and is defined as the minimal area of brain to be removed or disconnected to render the patient seizure free. This chapter illustrates how an understanding of these zones helps to approximate the EZand describe the common methodologies utilized to assess each zone.