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Search Results: 1 - 10 of 200806 matches for " Rafael G. Sola "
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New network and synchronization approaches in focal epilepsy research and treatment  [PDF]
Jesús Pastor, Rafael G. Sola, Lorena Vega Zelaya, Oscar Garnés, Guillermo Ortega
Health (Health) , 2013, DOI: 10.4236/health.2013.56A1001

Traditional approaches to focal epileptic surgery rely in the identification and resection of the epileptic zone. However, a significant minority of epileptic patients continue to experience seizures after surgery, a fact that shows how difficult it is to define this concept. In this work we will review some of the recent advances in the use of complex network theory and synchronization analysis in the study of neurophysiological epileptic records which shed new light on fragmented understanding of the epilepsy dynamic we have today. More important would be the potential treatments which could be implemented from the new information and change of perspective gathered by using this methodology, particularly the substitution of the traditional resective surgery in temporal lobe epilepsy patients.

Extrahippocampal Desynchronization in Nonlesional Temporal Lobe Epilepsy
Jesús Pastor,Eduardo G. Navarrete,Rafael G. Sola,Guillermo J. Ortega
Epilepsy Research and Treatment , 2012, DOI: 10.1155/2012/823683
Abstract: 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. 1. Introduction Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy, where the epileptogenic area is located at some part of the temporal lobe. Mesial TLE (MTLE) refers to those cases where the suspected source of epileptogenic activity is located in the mesial area of the temporal lobe [1], and lateral TLE (LTLE), instead, where the focus is located in the lateral side. MTLE is often associated with structural lesions and/or functional deficiency in one or several (dual pathology) mesial structures of the temporal lobe, with hippocampal sclerosis (HS) as the most common underlying abnormality [2]. However, pathological findings of damage in the amygdala and parahippocampal region, which in turn is subdivided into the entorhinal cortex (EC), perirhinal cortex (PC), and parahippocampal cortex (PPC), are also reported [3, 4]. A significant minority of MTLE patients have no pathological findings on magnetic resonance imaging (MRI), even though lateralization may be correctly performed by neurophysiological methods [5, 6]. Normal underlying mesial structures play a key role in our understanding of the pathogenesis of MTLE, as they oblige us to ask whether mesial sclerosis (MS) is either the cause or the effect in MTLE [7]. Pathophysiology in MTLE can be explained according to two models: (1) the “focal” model suggests that a single pathological region in the mesial temporal lobe is responsible for seizure origin, establishing a link
First true initial ictal SPECT in partial epilepsy verified by electroencephalography
Jesús Pastor,Luis Domínguez-Gadea,Rafael G Sola,Virgilio Hernando
Neuropsychiatric Disease and Treatment , 2008,
Abstract: Jesús Pastor1, Luis Domínguez-Gadea2, Rafael G Sola3, Virgilio Hernando3, María Luisa Meilán4, Eva De Dios4, José Luis Martínez-Chacón4, Marcos Martínez51Clinical Neurophysiology; 2Nuclear Medicine; 3Neurosurgery; 4Anaesthesiology and Reanimation; Hospital Universitario “La Princesa”, Madrid, Spain; 5Anaesthesiology and Reanimation, Cardiovascular Unit of Adults, Hospital Ramón y Cajal, Madrid, SpainAbstract: Drug-resistant epilepsy can sometimes be treated by surgery. In these cases, an accurate identification of the epileptogenic area must be addressed before resection. Ictal SPECT is one of the presurgical evaluations that can be performed, but usually, the increase in the regional cerebral perfusion observed is produced by diffusion of ictal activity. Here we describe a patient studied with v-EEG and foramen ovale electrodes that suffered a seizure after intravenous infusion of etomidate. The sequence of etomidate administration, followed by radiotracer and seizure was good enough for us to suspect that a true initial ictal SPECT was observed. We have implemented a kinetic model with four compartments, previously described (Andersen 1989), in order to estimate the fraction of hydrophilic radiotracer in the brain during the pre-ictal and ictal periods. This model has shown that the fraction of hydrophilic radiotracer during the seizure into the brain would be between 18.9% and 42.3% of total infused. We show the first true initial ictal SPECT demonstrated by bioelectrical recordings of the brain activity, obtained by a correct succession of events and compatible with theoretical data obtained from the kinetic model.Keywords: etomidate, foramen ovale electrodes, mathematical model, temporal lobe epilepsy
Identification of redundant and synergetic circuits in triplets of electrophysiological data
Asier Erramuzpe,Guillermo J. Ortega,Jesus Pastor,Rafael G. de Sola,Daniele Marinazzo,Sebastiano Stramaglia,Jesus M. Cortes
Quantitative Biology , 2014,
Abstract: Neural systems are comprised of interacting units, and relevant information regarding their function or malfunction can be inferred by analyzing the statistical dependencies between the activity of each unit. Whilst correlations and mutual information are commonly used to characterize these dependencies, our objective here is to extend interactions to triplets of variables to better detect and characterize dynamic information transfer. Our approach relies on the measure of interaction information (II). The sign of II provides information as to the extent to which the interaction of variables in triplets is redundant (R) or synergetic (S). Here, based on this approach, we calculated the R and S status for triplets of electrophysiological data recorded from drug-resistant patients with mesial temporal lobe epilepsy in order to study the spatial organization and dynamics of R and S close to the epileptogenic zone (the area responsible for seizure propagation). In terms of spatial organization, our results show that R matched the epileptogenic zone while S was distributed more in the surrounding area. In relation to dynamics, R made the largest contribution to high frequency bands (14-100Hz), whilst S was expressed more strongly at lower frequencies (1-7Hz). Thus, applying interaction information to such clinical data reveals new aspects of epileptogenic structure in terms of the nature (redundancy vs. synergy) and dynamics (fast vs. slow rhythms) of the interactions. We expect this methodology, robust and simple, can reveal new aspects beyond pair-interactions in networks of interacting units in other setups with multi-recording data sets (and thus, not necessarily in epilepsy, the pathology we have approached here).
Machine Learning Approach for the Outcome Prediction of Temporal Lobe Epilepsy Surgery
Rubén Arma?anzas, Lidia Alonso-Nanclares, Jesús DeFelipe-Oroquieta, Asta Kastanauskaite, Rafael G. de Sola, Javier DeFelipe, Concha Bielza, Pedro Larra?aga
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062819
Abstract: Epilepsy surgery is effective in reducing both the number and frequency of seizures, particularly in temporal lobe epilepsy (TLE). Nevertheless, a significant proportion of these patients continue suffering seizures after surgery. Here we used a machine learning approach to predict the outcome of epilepsy surgery based on supervised classification data mining taking into account not only the common clinical variables, but also pathological and neuropsychological evaluations. We have generated models capable of predicting whether a patient with TLE secondary to hippocampal sclerosis will fully recover from epilepsy or not. The machine learning analysis revealed that outcome could be predicted with an estimated accuracy of almost 90% using some clinical and neuropsychological features. Importantly, not all the features were needed to perform the prediction; some of them proved to be irrelevant to the prognosis. Personality style was found to be one of the key features to predict the outcome. Although we examined relatively few cases, findings were verified across all data, showing that the machine learning approach described in the present study may be a powerful method. Since neuropsychological assessment of epileptic patients is a standard protocol in the pre-surgical evaluation, we propose to include these specific psychological tests and machine learning tools to improve the selection of candidates for epilepsy surgery.
What Do Changes in Brain Perfusion Induced by Etomidate Suggest about Epilepsy in Human Patients?
Ivan Herrera-Peco,Rybel Wix Ramos,Luis Domínguez-Gadea,María Luisa Meilán,José Luis Martínez-Chacón,Eva de Dios,Rafael G. Sola,Jesús Pastor
Epilepsy Research and Treatment , 2010, DOI: 10.1155/2010/654265
Abstract: Epilepsy is one of the major neurological disorders, affecting roughly 1-2% of the world's population, of which approximately 20–25% of patients are drug resistant. A variety of drugs have been used to activate and identify the epileptic area in patients during presurgical evaluation. We studied the cerebral blood flow (CBF) by single photon-emission computed tomography (SPECT) and bioelectrical brain activity responses to etomidate in 11 patients. Etomidate (0.1?mg/kg) was administered while patients were monitored by video-electroencephalography with foramen ovale electrodes (FOEs). After etomidate administration, a brief period of high-frequency activity was observed, followed by a generalized, high-voltage delta pattern. Increased regional CBF was observed bilaterally in thalamus, putamen, and posterior hippocampus. Besides, the only interhemispheric difference was observed in the posterior hippocampus, where CBF decreased in the epileptic temporal lobe. Activation by etomidate induces a specific and repetitive response in the bioelectrical activity. In addition, CBF changes induced by etomidate may serve as a diagnostic tool in the near future. 1. Introduction Epilepsy affects 1–2% of the population worldwide and can be considered one of the most prevalent neurological illnesses [1]. Furthermore, between 20 and 25% of epileptic patients are resistant to drug treatment [2]. The most common type of drug-resistant epilepsy is temporal lobe epilepsy (TLE); however, patients with this form of epilepsy might be candidates for surgical resection of the epileptic focus [3, 4]. Before surgical resection, patients undergo a battery of tests during presurgical evaluation, including noninvasive ancillary tests such as video-electroencephalography (v-EEG), magnetic resonance imaging (MRI), single photon emission-computed tomography (SPECT), and positron emission tomography (PET) [3–5]. On occasion, invasive recordings are required, among which are foramen ovale (FOE), subdural, or depth electrodes [2]. SPECT is a technique that measure the regional cerebral blood flow (CBF) using radio-tracers [6, 7], and it can be used during ictal or interictal phases. Ictal SPECT is considered useful for identifying the epileptic zone (EZ, defined as the anatomical area necessary and sufficient for initiating seizures, and whose removal or disconnection is necessary for abolition of seizures), which is usually associated with regional hyper perfusion. On the other hand, the interictal SPECT is not performed regularly, but when performed the epileptogenic area shows
Money Supply and Inflation in Nigeria: Implications for National Development  [PDF]
Olorunfemi Sola, Adeleke Peter
Modern Economy (ME) , 2013, DOI: 10.4236/me.2013.43018

The study examines money supply and inflation rate in Nigeria. Secondary data that ranged between 1970-2008 were sourced from the CBN Statistical Bulletin. The study used Vector Auto Regressive (VAR) model. The stationary properties of the model were also explored. The results revealed that money supply and exchange rate were stationary at the level while oil revenue and interest rate were stationary at the first difference. Results from the causality test indicate that there exists a unidirectional causality between money supply and inflation rate as well as interest rate and inflation rate. The causality test runs from money supply to inflation, from the interest rate to inflation and from interest rate to money supply. The paper concludes that government should use the level of inflation as an operational guide in measuring the effectiveness of its monetary policy.

Stability of Synchronization Clusters and Seizurability in Temporal Lobe Epilepsy
Agostina Palmigiano, Jesús Pastor, Rafael García de Sola, Guillermo J. Ortega
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041799
Abstract: Purpose Identification of critical areas in presurgical evaluations of patients with temporal lobe epilepsy is the most important step prior to resection. According to the “epileptic focus model”, localization of seizure onset zones is the main task to be accomplished. Nevertheless, a significant minority of epileptic patients continue to experience seizures after surgery (even when the focus is correctly located), an observation that is difficult to explain under this approach. However, if attention is shifted from a specific cortical location toward the network properties themselves, then the epileptic network model does allow us to explain unsuccessful surgical outcomes. Methods The intraoperative electrocorticography records of 20 patients with temporal lobe epilepsy were analyzed in search of interictal synchronization clusters. Synchronization was analyzed, and the stability of highly synchronized areas was quantified. Surrogate data were constructed and used to statistically validate the results. Our results show the existence of highly localized and stable synchronization areas in both the lateral and the mesial areas of the temporal lobe ipsilateral to the clinical seizures. Synchronization areas seem to play a central role in the capacity of the epileptic network to generate clinical seizures. Resection of stable synchronization areas is associated with elimination of seizures; nonresection of synchronization clusters is associated with the persistence of seizures after surgery. Discussion We suggest that synchronization clusters and their stability play a central role in the epileptic network, favoring seizure onset and propagation. We further speculate that the stability distribution of these synchronization areas would differentiate normal from pathologic cases.
Braquiterapia guiada por imagen Image-guided brachytherapy
E. Villafranca,P. Romero,A. Sola,G. Asín
Anales del Sistema Sanitario de Navarra , 2009,
Abstract: La braquiterapia consiste en la administración de radiación en contacto íntimo con el tumor, con una baja exposición de los tejidos sanos circundantes. Empezó a utilizarse a comienzos del siglo XX y desde entonces ha ido desarrollándose: diferentes radioisótopos, sistemas de tratamiento a distancia, programas informáticos que permiten un cálculo individualizado de la dosis. Los cambios en los últimos a os dentro de la braquiterapia han afectado a dos aspectos. En primer lugar, la incorporación de las técnicas de imagen como la ecografía, la tomografía computarizada (TC) y la resonancia magnética (RM), imprescindibles para el diagnóstico y la estadificación tumoral. Su utilización mientras se realiza el implante ayuda a guiarlo y realizarlo con mayor precisión. En segundo lugar, la utilización de TC, RM y ecografía permiten mejorar la cobertura del tumor o reducir la dosis a los órganos sanos. Se utilizan dentro de sistemas de planificación inversa, que realizan el cálculo de dosis a partir de las recomendaciones de las dosis a administrar al tumor y a los órganos sanos. En estos programas de planificación es posible hacer los cálculos con mucha rapidez, teniendo en cuenta la colocación en cada momento de la fuente. Esta técnica, llamada planificación en tiempo real, empieza a mostrar ventajas en el tratamiento de los cánceres de próstata. La incorporación de las técnicas de imagen y las mejoras en los sistemas de cálculo han hecho que en la actualidad la braquiterapia juegue un papel importante en el tratamiento del cáncer de próstata, cérvix, mama, tumores de cabeza y cuello, bronquio o esófago. Brachytherapy consists in the administration of radiation in intimate contact with the tumour, with a low exposure of neighbouring healthy tissues. Its use began in the early XX century and it has developed since then: different radioisotopes, systems of remote treatment, computer programs making individual dose calculation possible. In recent years there have been changes affecting two aspects of brachytherapy. In the first place, the incorporation of imaging techniques such as echography, computerised tomography (CT) and magnetic resonance (MR), indispensable for diagnosis and tumoural staging. Their use when the implant is being done helps in guiding and carrying out the operation with greater precision. In the second place, the use of CT, MR and echography makes better coverage of the tumour possible, or reduces the dose to healthy organs. They are used in inverse planning systems, which carry out dose calculation on the basis of the doses to be administere
Risk of a first communityacquired spontaneous bacterial peritonitis in cirrhotics with low ascitic fluid protein levels
. Guarner C.,Sola R.,Soriano G.,Andreu M.
Annals of Gastroenterology , 2007,
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