Clinical Neuroscience

[The methodology and objectives of registrating high frequency oscillation in epilepsy]


SEPTEMBER 23, 2011

Clinical Neuroscience - 2011;64(09-10)

[Technological advances in digital EEG allowed the recording the full frequency band of the EEG. Activity beyond the traditional 0.3-70 Hz band reflects both physiological and pathological processes. High frequency activity recorded from the epileptic brain has been related to both epileptogenicity and epileptogenesis. The article reviews research avenues, clinical applications, and the methodology of detecting and quantifying high frequency activity.]



Further articles in this publication

Clinical Neuroscience

[Functional magnetic resonance imaging for cortical mapping in epilepsy]

KOZÁK Lajos Rudolf, TÓTH Vivien, BARSI Péter, RUDAS Gábor

[It is not only the total curative resection of pathological tissue or the minimization of symptoms to be considered in epilepsy surgery or other neurosurgical procedures, it is equally desirable to maintain the best possible quality of life. Cortical mapping methods can help achieve this goal by delineating eloquent areas, i.e. brain regions that are vital for providing an acceptable quality of life, albeit not prone to compensatory reorganization. These areas include among others the Broca and Wernicke regions for speech, the primary motor, sensory and visual cortices. Functional MRI gained importance in the last decade as a non-invasive clinical cortical mapping technique. This method is capable of localizing cortical areas selectively activated by a given task condition. Thus, selecting appropriate tasks can help mapping eloquent brain regions. Using functional MRI provides information that is complementary to other mapping methods. Moreover, it can replace invasive methods such as the Wada test. Here, we explain the background of functional MRI, compare it to other clinical mapping methods, explain the intricacies of paradigm selection, and show the limitations of the technique while also pointing out alternative uses.]

Clinical Neuroscience

[Magnetic resonance measuring and analitic methods in epilepsy]


[Neuroradiology and magnetic resonance imaging (MRI) as its leading tool play a basic role in the diagnostics of epilepsy. The result of the MRI examination is of utmost importance in patients with therapy resistent focal epilepsy possibly requiring neurosurgical intervention. Based on the continuously developing MRI techniques, we can use an optimal imaging protocol. Cerebral structures can be evaluated on a microanatomical level on high-resolution images with thin slices. The three-dimensional (3D) sequence has high spatial resolution, properly distinguishes cerebral grey and white matter, provides the possibility of surface rendering and volumetry, as well as an anatomical basis for other methods like tractography, functional MRI and neuronavigation. Diffusion weighted and diffusion tensor imaging (DWI, DTI) and tractography has an important role in differential diagnostics and tractography visualizes the main white matter tracts and their relation with brain pathologies. MR perfusion (MRP) provides help in differential diagnostics and may have a future role in the determination of the epileptogenic focus in multifocal pathologies. MR spectroscopy (MRS) is important in differential diagnostics, lateralization of focal epilepsy and in the confirmation of hippocampal sclerosis. Several of these methods need special hardware, software and expertise, but the basic MRI protocol for epilepsy can be implemented in all modern MR scanners of middle or high field strength.]

Clinical Neuroscience

[LORETA (Low Resolution Electromagnetic Tomography): A three-dimensional EEG source localization method]


[The author presents a brief overview of the EEG source localization method LORETA (Low Resolution Electromagnetic Tomography) with special reference to the not widely discussed data.]

Clinical Neuroscience

[Prolonged EEG-monitoring]


[Prolonged EEG monitoring and video-EEG monitoring are basic methods on the level of epilepsy centers. These methods are able to make differences between epilepsy and non epileptic paroxysmal manifestations like psychogenic non epileptic seizures, parasomniac phenomena, narcolepsy. The application of the method, at least the video-EEG variant, needs team work, high level organisation, highly educated staff and high tech electrographic devices. Running the method even with these requirements is beneficial from the cost-benefit aspect as well.]

Clinical Neuroscience

[Role of deep brain stimulation in epilepsy]

JANSZKY József, BALÁS István, KOVÁCS Norbert

[The deep brain stimulation (DBS) is an emerging treatment option in brain disorders in which randomized multicenter trials proved its efficacy leading to licensing different DBS methods in various brain diseases. More recently more and more brain structures have become candidates for being “target” in a possible DBS treatment of epilepsy. At present, only the DBS of the anterior nucleus of the thalamus (ANT) can be considered as a proved method for epilepsy treatment. Other potential targets for DBS treatment in epilepsy are the subthalamic nuclei, and the amygdala- hippocampus complex. There are some ongoing randomized studies to investigating their therapeutical role. The therapeutical outcome of ANT-DBS treatment in drug-resistant epilepsy seems to be better than the new antiepileptic drugs, but much worse than the results of a potential epilepsy surgery. At about 10% of patients may become seizure-free and 50% of patients may have a significant improvement. Nowadays ANT-DBS should be considered as an “ultima ratio” in those adult drug-resistant epilepsy patients with normal intelligence in which neither new antiepileptic drugs nor resective epilepsy surgery are a reasonable therapeutical options.]

All articles in the issue

Related contents

Clinical Neuroscience

[10 years, 600 monitoring sessions - our experience with the video EEG monitoring of children]


[Introduction- The only Hungarian video EEG laboratorywhere children of ages 0-18 can be continuously monitoredfor several days was opened 1 June 2001 at Department ofNeurology of Bethesda Children’s Hospital.Objectives- Summarizing our 10 years of experience withthe video EEG monitoring (VEM) of children and defining theplace of VEM in the treatment of childhood epilepsy inHungary.Patients and methods- We have processed data from 597monitoring sessions on 541 patients between June 1, 2001and 31 May, 2011 based on our database and the detailedsummaries of the procedures. Results- 509 patients were under the age of 18. The average length of the sessions was 3.1 days. We haveobserved habitual episodes or episodes in question in 477(80%) sessions. 241 (40%) sessions were requested with anepilepsy surgery indication, and 74 patients had 84 opera-tions. 356 (60%) were requested with a differential diagnosisindication, and 191 (53%) cases of epilepsy werediagnosed. We most commonly diagnosed symptomaticgeneralized epilepsy (57 cases). In 165 sessions the episodein question was not diagnosed as epilepsy. Among theparoxysmal episodes we have identified events ofpsychogenic origin, movement disorders, sleep disordersand behavioral disorders. Only 3% of the differential diag-nosis procedures brought no additional clinical information.Discussion- The diagnostic efficiency in our VEM laborato-ry is in accordance with the data found in the literature.Besides epilepsy surgery VEM is recommended if suspectedepileptic episodes occur and interictal epileptiform signs arenot present or are not in accordance with the symptoms, ifthere is no explanation for therapy resistance and if paroxys-mal episodes of non-epileptic origin are suspected but theycannot be identified based on the anamnesis. VEM is also helpful in diagnosing subtle seizures. The procedure hasnumerous additional benefits in patient care and in trainingthe parents and hospital staff. ]

Clinical Neuroscience

[Questions of epileptogenesis and prevention in symptomatic epilepsies]

NIKL János

[Symptomatic epilepsies usually report themselves after a longer period of time after brain injury, after the so-called latent period. During this period progressive functional and structural changes occur which finally cause an increased excitatory condition. The process of epileptogenesis may be examined in animal models, such as in the kindling, status epilepticus, hypoxicischaemic models. Data gained from such sources support the hypothesis that the first injury results in a lower seizure threshold, but genetical and enviromental factors also contribute to the development of epilepsy and most probably further insults may be needed. The development of epilepsy can be traced back to several reasons. In spite of this, the latent period provides opportunity for the prevention of epilepsy or for the influence of epileptogenesis in such a manner that later treatment can become more succesful. Prevention should be an aim in clinical practice, as well. Medication used presently are more like to have anticonvulsive properties and their antiepileptogenic effect is questionable. Due to this fact, development of new drugs is necessary with new theoretical background. The most important influence on the incidence of epilepsy in recent years has been provided by the improvement in neonatal care. This highlights the fact that such optimal medical care should be provided in the acute period of brain injury which can terminate or lessen the risk of epilepsy.]

Clinical Neuroscience

[The role of neuronavigation in the preoperative invasive evaluation and surgical treatment of drug resistant epilepsies]

ERÕSS Loránd

[For localizing the epileptogenic zone in cases of focal epilepsies detailed clinical investigations, imaging studies and electrophysiological methods are in use. In lesional epilepsies the intrapreoperatíve localization of the lesion and it’s location to the eloquent cortex is essential for the neurosurgeon. The development in image guided neurosurgery lead us to use neuronavigation systems to localize intracerebral lesions or functionally eloquent cortical areas or subcortical pathways during surgery. Neuronavigation brought changes in preoperatíve evaluation and in resective surgery in epilepsy as well. In this article we describe the basics of neuronavigation and enhance the advantages of the technique in epilepsy surgery during the presurgical evaluation with invasive electrodes, in resective surgery and DBS for epilepsy.]

Clinical Neuroscience

[Intracranial EEG monitoring methods]

TÓTH Márton, JANSZKY József

[Resective surgery is considered to be the best option towards achieving seizure-free state in drug-resistant epilepsy. Intracranial EEG (iEEG) is necessary if the seizure-onset zone is localized near to an eloquent cortical area, or if the results of presurgical examinations are discordant, or if an extratemporal epilepsy patient is MRI-negative. Nowadays, 3 kinds of electrodes are used: (1) foramen ovale (FO) electrodes; (2) subdural strip or grid electrodes (SDG); (3) deep electrodes (stereo-electroencephalographia, SEEG). The usage of FO electrode is limited to bitemporal cases. SDG and SEEG have a distinct philosophical approach, different advantages and disadvantages. SDG is appropriate for localizing seizure-onset zones on hemispherial or interhemispherial surfaces; it is preferable if the seizure-onset zone is near to an eloquent cortical area. SEEG is excellent in exploration of deeper cortical structures (depths of cortical sulci, amygdala, hippocampus), although a very precise planning is required because of the low spatial sampling. The chance for seizure-freedom is relatively high performing both methods (SDG: 55%, SEEG: 64%), beside a tolerable rate of complications.]

Clinical Neuroscience

[Supplementary sensory-motor seizures - symptomatology, etiology, and surgical management with illustrative case reports]

HALÁSZ Péter, JUHOS Vera, ERÕSS Loránd, TÓTH Szabolcs, BALOGH Attila, GYÖRGY Ilona, BARSI Péter, KELEMEN Anna, BARCS Gábor

[In the past decade, owing to the advance of epilepsy surgery, growing knowledge has accumulated on the role of the supplementary motor area, described by Penfield and coworkers in the early fifties, in movement regulation and on the characteristics of seizures involving this area. In the Hungarian neurological literature this topic - despite its neurophysiological and practical clinical importance - has been hardly touched. The authors, based on their own experience obtained from surgeries performed within the framework of the "Co-operative Epilepsy Surgery Program", describe the electrophysiological features of this area, its role in movement regulation and the symptoms of epileptic seizures stemmed from or spread onto this area. Using cases as illustrations, they demonstrate the reasoning and various algorithms of the multidisciplinary examination necessary to explore the seizure onset zone and the pathways of seizure spread. Details of the surgical solution are also described.]