Cirugía de la Epilepsia.- Estudios Clínicos Neurofisiológicos


En esta sección se ponen a disposición de todos los usuarios y pacientes, una lista de publicaciones relacionadas con la Cirugía de la Epilepsiar en los que han participado activamente miembros del equipo médico de la Unidad de Neurocirugía.

Esta sección dada su importancia, se subdivide en otras cuatros subsecciones:

Tratamiento Quirúrgico

Estudios Clínicos Neurofisiológicos

Estudios Neuroradiológicos

Estudios Neuropsicológicos

Estudios Anatomopatológicos

Estudios Preoperatorios

Hyper-Synchronization, de-Synchronization, Synchronization and Seizures

Jesús Pastor, Rafael García de Sola and Guillermo J. Ortega
Introduction:
Ranging from its most basic mechanisms to the clinical symptoms, epilepsy is tightly associated with the word “synchronization”. In fact, synchronization phenomena underlying epilepsy are described in several mechanisms at different temporal and spatial scales. At the lowest spatial scale, hippocampal and neocortical interictal spikes appear as the result of synchronized activity of pyramidal cells. At a larger spatial scale, epileptic seizures are usually described as a state of “hypersynchrony” encompassing extended cortical areas. Synchronization and epilepsy are so associated one to each other that lack of synchronization, or desynchronization, has been highlighted in recent years as a key aspect of the underlying dynamic in this pathology. The word synchronization comes from two Greek words, chronos and same, which means “sharing the same time”; therefore, a synchronized event is always composed by the temporal coincidence of two or more actions. However, it is usually understood the existence of an underlying mechanism that cause the synchronization itself. In this sense, synchronization is assumed differently from chance, because no deterministic causal effect exists in the last one. On the other hand, the use of the word synchronization is generally associated with a mechanism, known or not, that makes possible the temporal coincidence. In the above sense, and from the very beginning of epilepsy research, the word synchronization is found in many aspects of this pathology. Every time we found the word synchronization in epilepsy, one is tempted to think in a pathological substrate that would make it possible. However, it seems that synchronization in epilepsy has suffered from bifurcating routes since the beginnings of the quantitative descriptions of epileptic phenomena. The very clever and insightful descriptions made by the epilepsy researches in the late 40’s and 50’s (Penfield & Jasper, 1954) were plagued by the words synchronization and hypersynchronization, and today they are still used almost in the same fashion that were originally used. However, since the first description of the synchronization phenomena by Christian Huygens in 1673 to now- days, there has been a profound revision and enlargement of the concept of synchronization especially in the last years (Pikovsky et al., 2001). Chaos theory, complex networks methodologies and nonlinear time series analysis have dug into the traditional concept of synchronization with the net result of a completely new proposal of what synchronization actually is. Today, in fact, there is no more a single synchronization phenomena, but instead, the traditional term has been split in several, more specific terms to characterize the numerous forms of the underlying mechanism but also, of the different kind of synchronized objects. It seems that the new understanding we have today of synchronization is far from being adopted by the epileptologists, especially by the physician community. New terms as lag or full synchronization are rarely seen in clinical works, which is rather frustrating, because synchronization research in the last years has opened up new and powerful techniques, which would very useful in the improvement of diagnostic or therapeutic techniques.
This chapter is intended to review some of the new advances in synchronization in general and specifically in epilepsy research. A very brief mathematical introduction will be presented in order to fully understand the whole range of synchronization concepts presented in the chapter, either in the theoretical or empirical fields. Our aim thus is to show only the most basic methods and applications of synchronization and epilepsy.
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Extrahippocampal Desynchronization in Nonlesional Temporal Lobe Epilepsy

Jesús Pastor, Eduardo G. Navarrete, Rafael G. Sola, and Guillermo J. Ortega
Resumen
Although temporal lobe epilepsy (TLE) is traditionally associated with both hypersynchronous activity in the form of interictal epileptic discharges and hippocampal sclerosis, recent findings suggest that desynchronization also plays a central role in the dynamics of this pathology. The objective of this work is to show the imbalance existing between mesial activities in patients suffering from mesial TLE, with normal mesial structures. Foramen ovale recordings from six patients with mesial TLE and one with lateral TLE were analyzed through a cluster analysis and synchronization matrices. None of the patients present findings in the MRI presurgical evaluation. Numerical analysis was carried out in three different situations: awake and sleep interictal and also during the preictal stage. High levels of desynchronization ipsilateral to the epileptic side were present in mesial TLE patients. Low levels of desynchronization were present in the lateral TLE patient during the interictal stage and almost zero in the preictal stage. Implications of these findings in relation with seizure spreading are discussed.

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Análisis complejo de la actividad eléctrica en la epilepsia del lóbulo temporal: registros con electrodos de foramen oval.

Iván Herrera-Peco,Jesús Pastor,Concepción Alonso-Cerezo, Rafael G. Sola, Guillermo J. Ortega

Resumen:

Introducción. La epilepsia del lóbulo temporal (ELT) se asocia comúnmente al proceso de sincronización durante la etapa interictal, manifestándose como ‘puntas’ en los registros neurofisiológicos, y también a la actividad hipersincrónica durante las crisis clínicas. No obstante, la desincronización parece desempeñar un papel importante también en el proceso de la epileptogénesis, favoreciendo la iniciación de las crisis.
Objetivos. Mostrar cómo las nuevas técnicas de análisis complejo y redes aplicadas a los registros de electrodos de foramen oval proveen nueva y valiosa información sobre la dinámica de la actividad mesial en la ELT y, en particular, que la desincronización de la actividad mesial desempeña un papel importante en la ELT.
Pacientes y métodos. Mediante una técnica de cluster, se analizaron los registros de seis pacientes con ELT durante la etapa interictal y dos crisis durante el período ictal.
Resultados. La actividad eléctrica en el lado ipsilateral se comporta de una manera menos sincrónica que la del lado contralateral. Existe una clara tendencia en la zona mesial del lado epiléptico a organizarse en grupos aislados de actividad sincrónica en comparación con el lado contralateral, organizado en forma de grandes grupos de actividad sincronizada.
Conclusiones. El análisis de los registros neurofisiológicos, en particular de los electrodos de foramen oval, por medio del análisis de clusters y redes suministra nueva información no accesible al análisis clásico de puntas. La mayor desincronización en el lado ipsilateral favorecería la aparición y origen de las crisis en ese lado.
Palabras clave. Cluster. Electrodos de foramen oval. Epilepsia del lóbulo temporal. Redes complejas. Sincronización.

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Fuentes de voltaje en la región temporal mesial inducidas por etomidato

Iván Herrera-Peco, Guillermo J. Ortega, Virgilio Hernando-Requejo, Rafael G. Sola, Jesús Pastor

Resumen:

Introducción. Recientemente se ha mostrado que la activación del electroencefalograma (EEG) mediante etomidato es una técnica específica y segura durante la valoración de pacientes candidatos a cirugía de la epilepsia.

Objetivo. Analizar las propiedades fisiopatológicas de la actividad interictal inducida mediante etomidato y compararla con la actividad espontánea interictal.

Pacientes y métodos. Se estudió a 13 pacientes mediante vídeo-EEG con electrodos de foramen oval y se administró eto- midato (0,1 mg/kg) para activar la región epileptógena. La actividad de los electrodos del foramen oval se ajustó a una fuente de voltaje monopolar.

Resultados. La actividad interictal mediada por el etomidato se ajusta extraordinariamente a un modelo monopolar, al igual que ocurre con la actividad interictal basal. La distribución de las fuentes de voltaje registradas durante la actividad interictal basal y en presencia de etomidato es semejante. No hay diferencias en la dispersión entre la actividad interictal basal y la de etomidato. Se ha encontrado un incremento de la carga equivalente inducida por el etomidato.

Conclusiones. La actividad interictal basal y aquella inducida por etomidato poseen unas características electrofisiológicas muy semejantes, lo que sugiere que activa las mismas estructuras responsables de la actividad irritativa, por lo que puede usarse como activador específico de las zonas epileptógenas en pacientes con epilepsia del lóbulo temporal.

Palabras clave. Actividad interictal. Epilepsia del lóbulo temporal. Etomidato. Fuentes de voltaje. Modelo monopolar.

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Cambios en la perfusión cerebral inducidos por etomidato en pacientes con epilepsia del lóbulo temporal

I. Herrera-Peco, R. Wix-Ramos, L. Domínguez-Gadea, M.L. Meilán-Paz, J.L. Martínez-Chacón, E. de Dios, R.G. Sola, J. Pastor

Resumen:

La epilepsia es uno de los mayores trastornos neurológicos. Afecta a alrededor del 0,5-2% de la po- blación mundial, y entre el 20-25% de los pacientes son resistentes a la medicación. Objetivo. Analizar la respuesta de la per- fusión cerebral –valorada mediante tomografía simple por emisión de fotón único (SPECT)– y la actividad bioeléctrica –en scalp y región temporal mesial– a la aplicación de etomidato. Pacientes y métodos. Se estudiaron 10 pacientes evaluados pre- quirúrgicamente y estudiados mediante videoelectroencefalograma (video-EEG) con electrodos de foramen oval (EFO) y SPECT. Se administró etomidato (0,1 mg/kg de peso), seguido por 99mTc-HmPAO, durante el estudio en el video-EEG + EFO. Resultados. Los efectos secundarios consistieron en mioclonías (n = 7) y dolor moderado (n = 2). No se han observado efec- tos cardiovasculares o respiratorios significativos. La actividad bioeléctrica en scalp consistió en una actividad rápida inicial breve, seguida por un patrón delta generalizado e hipervoltado durante varios minutos. En la región irritativa, se observó un marcado incremento de la actividad interictal. La perfusión cerebral aumentó, en general en todas las áreas estudiadas, espe- cialmente en la región temporal (lateral y mesial) y en las áreas talámicas. En la cola del hipocampo no epileptógeno, se ha observado el segundo mayor incremento en la perfusión cerebral, y es la única región que se diferencia de la contralateral. Conclusiones. La activación mediante etomidato da lugar a una respuesta específica y repetible sobre la actividad bioeléctri- ca. Además, la perfusión cerebral local muestra cambios relacionados directamente con la región epileptógena, y puede ser- vir, por tanto, como herramienta diagnóstica en un futuro inmediato. [REV NEUROL 2009; 49: 561-5]

Palabras clave: Epilepsia temporal. Esclerosis mesial. Hipoperfusión en SPECT. Perfusión cerebral.

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Complex network analysis of human ECoG data

Guillermo J. Ortega, Rafael G. Sola, Jesús Pastor

Resumen:

Localization of the epileptogenic zone (EZ) is an important issue in epileptology, even though there is not a unique definition of the epileptic focus. By using complex network analysis of electrocorticographic (ECoG) data we identify three singular areas in the temporal lobe of epileptic patients, the node with highest local synchronization power, the most connected node, and the node with highest interactions load. Connectivity in the data is extracted from the Minimum Spanning Tree (MST) of global correlations. We address the question whether removal of these nodes during the surgery is crucial in the suppression or reduction in the quantity of post-operative seizures. From five ECoG records, local areas with high synchronization power appear to be significantly involved in the development of epileptic seizures. The other two areas seem not to be fundamental in the seizures onset and development. Moreover, the approach proposed shed new light in cortical connectivity patterns in the human temporal lobe. All the analyzed records are during the interictal state.

Palabras clave: ECoG Synchronization, Temporal lobe epilepsy, Multivariate Complex network theory.

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Ausencia congénita en la región frontotemporal izquierda sin consecuencias neuropsicológicas

E. García Navarrete, P. Martín Plasencia, F. Carvajal, R. García de Sola

Resumen:

En la literatura neuropsicológica se han descrito un número muy reducido de pacientes con ausencia congénita de los lóbulos frontal y temporal. En relación con los mismos, algunos estudios indican que pueden tratarse de casos asintomáticos, si bien la mayoría coinciden en señalar que se asocian con discapacidad intelectual moderada o ligera, destacando las dificultades en atención, planificación y/o en habilidades visuoconstructivas. También se señala que, en ocasiones, guardan relación con trastornos conductuales que pueden llegar a asociarse con distintos cuadros psiquiátricos. En cualquier caso cabe destacar que no se ha encontrado que exista relación con alteraciones verbales o articulatorias tal como cabría esperar atendiendo a las funciones propias de los circuitos frontotemporales.

Palabras clave: neuropsicología, neurofisiología, quiste aracnoideo.

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Synchronization Clusters of Interictal Activity in the Lateral Temporal Cortex of Epileptic Patients

Guillermo J. Ortega, Liset Menendez de la Prida, Rafael G. Sola, Jesus Pastor

Resumen:

Drug-resistant temporal lobe epilepsy (TLE) can be treated by tailored surgery guided by electrocorticography (ECoG). Although its value is still controversial, ECoG activity can provide con- tinuous information on intracortical interactions that may be useful to understand the pathophysiol- ogy of TLE. The goal of this study is to characterize local interactions in multichannel ECoG recordings of the lateral cortex of TLE patients using three synchronization measures and to link this informa- tion with surgical outcome.
Our results show that synchronous in- traoperative ECoG activity emerges from specific cortical areas that are highly differentiated from the rest of the temporal cortex. This suggests that synchronization analysis could be used to function- ally map into the temporal cortex of TLE patients. Moreover, our results suggest that these sites might be involved in the circuits that participate in clinical seizures.
Palabras clave: ECoG, Temporal lobe epilepsy, Synchronization, Cross-correlation, Clusters.

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Voltage sources in mesial temporal lobe epilepsy recorded with foramen ovale electrodes

Jesús Pastor, Liset Menendez de la Prida, Virgilio Hernando, Rafael G. Sola

Resumen:

We introduce a monopole model to examine the sources of ictal and interictal activity in mesial temporal lobe epilepsy (MTLE) recorded using foramen ovale electrodes (FOE). Methods: Classical electrostatic theory was applied to derive mathematical expressions. Interictal and ictal activity was acquired using FOE and scalp video-electroencephalography (v-EEG) during awake and sleep states. A total of 2057 interictal spikes and 712 ictal spikes were analyzed. Thirty-five seizures from several consecutive episodes were examined. MRI and clinical data were correlated with voltage source localization.
Results: Patients (20) were grouped according to the spatial distribution of voltage sources of interictal activity. Voltage sources were located over 3.4 and 21.6 mm in the anterior-to-posterior axis of mesiotemporal structures and separated no more than 7 mm from this axis. In most patients (16), sources were restricted to 11.1 ± 1.5 mm, whereas other patients (4) exhibited a wider distribution (29.6– 43.5 mm). Sources of ictal and interictal activity partially overlapped, with ictal sources exhibiting a posterior localization at 20– 40 mm. Both interictal and ictal sources were anterior to MRI atrophy. No difference between awake and sleep states were found, neither correlation between source scattering and history of epilepsy.
Conclusions: Voltage source analysis applied to FOE suggests that, in most MTLE patients, interictal activity emerges from very restrict- ed areas. Some patients, however, exhibited sources which are distributed all along the mesiotemporal structures. Our data suggest an anterior-to-posterior alignment of the irritative, ictal and atrophic zones. Significance: The voltage source model applied to FOE can help to map the extension of the irritative and ictal areas in mesiotemporal structures.
2006 Published by Elsevier Ireland Ltd on behalf of International Federation of Clinical Neurophysiology.

Palabras clave: Voltage source localization; Foramen ovale electrodes; Interictal activity; Mesial sclerosis; Temporal epilepsy; Video-electroencephalography

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Bases fisiopatológicas de la epilepsia del lóbulo temporal: estudios en humanos y animales

J. Pastor, Y.G. Uzcátegui, B. Gal-Iglesias, G.J. Ortega, R.G. Sola, L. Menéndez de la Prida

Resumen:

Temporal lobe epilepsy (TLE) is the most frequent form of pharmaco-resistant epilepsy in human. Research using material from TLE patients undergoing surgery and animal models has significantly increased in the last decade. Development. We review recent findings obtained over the last years from electrophysiological and anatomical studies in human and animal models of TLE. Data suggest a large heterogeneity and inter-individual variability depending on the model and the system under study. However, a common principle that appears to underlie the epileptic condition is the reorganization of excitation and inhibition resulting in hyperexcitability. Recent research combining in vitro electrophysiology together with depth recordings in vivo and new analytical methodologies is also discussed. Conclusions. A multidisciplinary approach using both human and animal models can help to fill gaps in our knowledge and to provide unique insights into the pathophysiology of TLE. [REV NEUROL 2006; 42: 663-73]

Palabras clave: EEG. Intracellular recordings. Kindling. Membrane receptors. Mesial sclerosis. Microelectrodes. Temporal lobe epilepsy.

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Fundamentos biofísicos de la magnetoencefalografía

J. Pastor, R.G. Sola

Resumen:

It is sought to expose in a simple but rigorous way the physical, neurobiological and methodological foundations of the magnetoencephalography (MEG). Development. We start from the basic properties of the classical electromagnetism, analyzing in detail the concepts of electric and magnetic fields, the Maxwell’s equations and the multipolar development of potentials. All these tools are very important to know the peculiarities of the MEG studies. Later on, they are reviewed very briefly the different types of potentials generated by the neurons and their implication in the MEG. Lastly, some necessary technical characteristics will be commented for detection of the very weak neuromagnetic fields. It is shortly exposed the concept of tunnel effect, in one that detection systems used at the present time are based (SQUID). Conclusion. MEG is a very promising recent technique that is used in epilepsy studies, evoked potentials and other functional pathologies. Its utility in clinic continues being even controversial. However, it is fundamental to know the mechanisms that justify their use in order to know better their benefits and limitations.(REV NEUROL 2002; 34: 843-50)

Palabras clave: Action potentials. Electric field. Magnetic field. Post-synaptic potentials. SQUID. Tunnel effect.
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Fundamentos biofísicos de la actividad neuronal

Jesús. Pastor

Resumen:

It is sought to expose in a simple but rigorous way the fundamental basis of the classical biophysics. Development. I start from the basic properties of a simple system (two solutions separated by a semipermeable membrane) in order to analyze the process of development of differences of potential. It is analyzed with special interest the development of the Nernst and Nernst-Planck equations. Then it is studied how this difference potential can originate, with different ionic species, the resting potential (Goldman, Hodgkin and Katz model). The next step consists in to analyze how the action potential arises. To do this, it will be of capital importance the mathematical model developed by Hodgkin and Huxley in the fifties; for it will be analyzed it thoroughly. Finally, some properties of the ionic channels will be commented that symbolize the biological implementation of the previous model. Conclusion. The fundamental property of the nervous system that constitutes its biological sense is the handling of the information in a quick and sure way. This information codes it basically in form of potentials and its changes. For it, it would be important for clinical neurophysiologists, neurologists, neurosurgeons and psychiatrists to understand the mechanisms that underlie into the behavior of the nervous system. [REV NEUROL 2000; 30: 741-55] [http:// www.revneurol.com/3008/i080741.pdf]

Palabras clave: Action potential. Hodgkin and Huxley model. Ionic channels. Nernst potential. Nernst-Planck equation. Neuronal physiology. Resting potential.
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Revisión bibliográfica sobre la utilidad de la magnetoencefalografía en la epilepsia

J. Pastor, P. Pulido, R.G. Sola

Resumen:

Magnetoencephalography (MEG) it is a non-invasive technique of recording the brain activity, based on the detection of magnetic fields. Aim. It is sought to determine the relative contribution of MEG to the handling of patients with epilepsy concerning to other diagnostic technics like scalp EEG, v-EEG (v-EEG), electrocorticography (EcoG), magnetic resonance (MR and MRf), positron emission tomography (PET) and single photon emission tomography (SPECT). Method. It has been carried out it a critical revision of the literature, using the approaches of the evidence-based medicine (EBM). In the databases MEDLINE and HEALTH-START, among the years 1996 and 2001, it were found 1169 references. After the one sieved, 36 were selected, of those that chose 22 definitively for their analysis: 3 articles were classified as of Technical Effectiveness and 19 as Effectiveness in Diagnostic Accuracy. For the methodological quality, 2 were classified as of group B, 16 in C and 4 in D. Eighteen articles make reference to MEG and pharmaco-resistant epilepsy, while other 4 they make reference to MEG and pharmaco-sensitive epilepsy. Sensibility is highly variable, being bigger in extratemporal epilepsy (44-92.9%), then in temporal (33.3-80%) and smaller in mesial temporal (42.3-53%). Specificity is bigger for patient with anatomical lesions. Conclusion. 1. Localization of interictal activity is better in neocortical lateral regions, diminishing in mesial ones, 2. The methodological deficiencies of the articles prevent to carry out a meta-analysis of the data.[REV NEUROL 2001; 33:]

Palabras clave: Electroencephalography. Epilepsy. Evidence-based medicine. Magnetic resonance. Magnetoencephalography. Positron emission tomography.
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Localización de la zona epileptógena mediante el análisis de dipolos electroencefalográficos

P. Rojo, A.G. Caicoya, M. Martín-Loeches, R.G. Sola, M.A. Pozo

Resumen:

In partial epilepsy with seizures which are resistant to drug treatment, better results may be obtained with surgery. This follows thorough assessment to identify the area of the brain responsible for the origin of the seizures, or the epileptogenic zone (EZ), and show that surgical operation will not cause neurological or cognitive damage which might handicap the patient. Objective. This study analyses the value in diagnosis of electroencephalographic dipoles in delimitation of the EZ in patients with refractory partial epilepsy who are candidates for surgical treatment. Patients and methods. In 43 patients we made EEG recordings whilst at rest with their eyes shut during 15 minutes. The signal was analysed by digital EEG apparatus and a map drawn of cerebral electrical activity based on the maximum average amplitude of the epileptic spikes. The electric dipole equivalent to epileptiform activity between seizures was obtained using the programme for analysis of electroencephalographic sources BESA. The localization of the EZ by means of the dipole was compared with the results of EEG, MR, SPECT and seizure video-EEG using intracranial electrodes. Results. The results of this study show that the dipole model used is highly sensitive for localization of EZ, and in cases in which the dipole and MR coincided, its sensitivity is similar to that of video-EEG during seizures. Conclusion. The model of dipole used in this study is of great help when indicating surgery for patients with drug-resistant epilepsy. [REV NEUROL 2001; 32: 315-20] [http://www.revneurol.com/3204/k040315.pdf]

Palabras clave: Dipole. Drug resistant partial epilepsy. Interictal epileptiform activity. Temporal lobe epilepsy.
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Magnetoencefalografía: una nueva técnica de diagnóstico funcional en neurociencia

C. Maestú, E. Gómez-Utrero, R. Piñeiro, R.G. Sola

Resumen:

We present a review on the technical, methodological and clinical advances in the functional study of the brain by means of magneto-encephalography. We look back the milestones of its historical development, through the work of the major research groups on this field and through our group’ s works and database (including doctoral thesis). Discussion on the neurophysiological and biomagnetism basis is provided as well as description of technical develop- ments in superconducting detectors (SQUID, Superconducting Quantum Interference Device), signal processing, enhancement of noise-signal ratio and dipole modeling. Development. The need for brain functional studies has led to newer imaging procedures (functional magnetic resonance, PET, SPECT, etc.). Their spatial and temporal resolution and invasivity are compared to that of magneto-encephalography. Current equipments, up to 306 whole-head channels, may accurately detect cortical and subcortical activity. Apart from the physiological activity, it may be applied to a number of conditions: epilepsy (ictal, interictal and presurgical); dementiae, movement disorders, stroke, eloquent cortex delimitation prior to tumour or lesion resection; learning disabilities and foetal studies. Conclusions. Magnetoencephalography provides with an excellent temporal, very good spatial resolution, acquires in real-time, without references and minimal interference. It entails a great advance in the diagnostic approach in neurosciences [REV NEUROL 1999; 28: 1077-90].

Palabras clave: Clinical applications. Electroencephalography. Evoked fields. History. Magnetoencephalography. Review. Super- conducting Quantum Interference Device.
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Aspectos neurofisiológicos in vivo e in vitro de la epilepsia

L. Menéndez de la Prida, R.G. Sola, M.A. Pozo

Resumen:

Some electrophysiological aspects of the interictal activity in temporal lobe epilepsy (TLE) are under debate. However, surgery is often guided by both, pre- and intra-operative recordings of interictal activity. Some of these studies include intraoperative electrocorticography (ECoG) that guide tailored resection. Objective. To analyze several aspects of interictal activity recorded by ECoG and to explore its electrophysiological basis in vitro. Patients and methods. ECoGs from thirteen patients suffering drug-resistant TLE were analyzed. Both linear and non-linear methods were introduced to explore the ECoG signals. In two cases, neocortical tissue was also electrophysiologically studied in vitro. Results. Interictal ECoG activity showed a mesial origin, a cortical origin or a mixed mesial/temporal origin. Both in cortical and mesial/cortical origin, cortical interictal ECoG signals are characterized by spatiotemporal clusters of activity. In vitro study of cortical tissue from these clusters showed alterations in the synaptic control of excitability. Conclusion. Our results suggest an electrophysiological basis of interictal activity. Combination of linear and non-linear methods is a very useful tool to explore on-line the interictal ECoG activity during surgery. [REV NEUROL 2002; 34: 430-7]

Palabras clave: Correlation. Electrocorticography. In vitro. In vivo. Non-linear. Temporal lobe epilepsy.
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Análisis de fuentes de voltaje en estudios con electrodos de foramen oval

J. Pastor, P. Rojo, R.G. Sola

Resumen:

Paroxysmal activity in medial temporal lobe epilepsy is originated in either hippocampal or parahip- pocampal regions. This activity can be directly recorded by foramen ovale electrodes. That paroxysmal activity will start from irritative or ictal areas. However, anatomo-functional relations between both regions are still debated. Objective. We describe a new physical very simple model which allows to directly analysis the anatomo-physiological relations between sources for interictal an ictal areas. Results. 1) The mathematical model allows to fit with minimum error and great precision the voltage sources originated from monopoles. 2) We can obtain this degree of precision with a matrix using an internodal distance of 0.1 mm (300 × 200 nodes) 3) Triplets of potentials with double sources -with equal or specially with inverse charges- have bigger error than monopolar charges. 4) Fitting real data obtained from a patient shows an error of 0.29 ± 0.17% for interictal and 0.54 ± 1.22 % and 2.84 ± 3.00 % for two seizures (mean ± SD) Conclusions. This model allows directly to know the relative anatomo-physiological relations between interictal and ictal sources in MTLE, which have a very important implications so for patho-physiological as therapeutics and outcome implications. [REV NEUROL 2004; 38: 209-16]

Palabras clave: Ictal activity. Interictal activity. Mathematical model. Medial sclerosis. Temporal epilepsy. V-EEG.
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