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1.
Educ. med. (Ed. impr.) ; 18(supl.1): 51-56, mar. 2017. tab, graf
Article in Spanish | IBECS | ID: ibc-194575

ABSTRACT

Se describe la metodología de instrucción y evaluación en práctica clínica y el grado de implicación del profesorado en esta tarea en la Unidad Docente del Hospital 12 de Octubre (Facultad de Medicina, Universidad Complutense de Madrid). A pesar de algunas disfunciones curriculares, nuestros estudiantes alcanzan un buen nivel de competencia clínica al final del grado. Algunos profesores tienen un conocimiento limitado de los roles docentes que pueden asumir, por lo que deberían recibir formación específica. Idealmente, la enseñanza clínica ha de implicar a todos los profesionales que cuidan del paciente en el contexto extra- e intrahospitalario


We describe the methodology for instruction and assessment of clinical practice and analyze the profile and teaching roles of faculty at the Teaching Unit of the Hospital 12 de Octubre (Faculty of Medicine, Complutense University of Madrid). Despite some structural limitations in curriculum development our students reach a good final level of clinical competence. The need for trainers to understand the different roles they can assume, improving faculty development and involving all the professionals taking care of the patient in the teaching process are emphasized


Subject(s)
Humans , Education, Medical/trends , Schools, Medical/organization & administration , Evidence-Based Practice/education , Hospitals, Teaching/organization & administration , Hospitals, University/organization & administration , Faculty/standards , Teacher Training/trends , Curriculum/trends , Educational Measurement , Hospital Accreditation
2.
Neurocir. - Soc. Luso-Esp. Neurocir ; 26(2): 53-63, mar.-abr. 2015.
Article in Spanish | IBECS | ID: ibc-135033

ABSTRACT

Introducción: El método para seleccionar a los graduados que acceden a los puestos de residencia condiciona decisivamente el funcionamiento curricular en las escuelas de medicina, incluyendo la manera de estudiar y aprender del estudiante y la actitud docente del profesorado. La metodología usada actualmente en España puede ser fácilmente mejorada, por lo que tomando como referencia las metodologías multicriterio empleadas en el Reino Unido y los EE. UU. proponemos una similar para ser aplicada en nuestro país. Objetivos del estudio: Analizar las limitaciones del método para la selección de los residentes utilizado en España y proponer uno nuevo que mejore el ordenamiento de los candidatos y evite la distorsión producida por el actual sobre la dinámica curricular. Aparte de proponer la modificación del examen MIR, se comenta la necesidad de mejorar las enseñanzas prácticas y evaluar el nivel de competencia clínica de los estudiantes. Conclusiones: El método de selección aplicado en España, basado fundamentalmente en un test teórico, resulta inapropiado y debería ser sustituido por otro que evalúe mejor la capacidad la contextualización clínica de los conocimientos y el nivel de competencia clínica y que tenga en cuenta el rendimiento global del estudiante a lo largo del grado de forma ponderada


Introduction: The method for selecting medical graduates for residency positions has a strong influence on teaching and learning strategies in medical schools. The methodology currently used in Spain does not seem appropriate for ranking the candidates or improving curriculum development. Thus, and taking into account the most consistent methodologies used in the United Kingdom and USA, we have designed a new method to be used in our country. Objectives: To analyze the limitations of the methodology used in Spain, and propose a new one aimed to improve the accuracy of selection itself and avoiding the negative influence of the current method on curricular development. In addition, we emphasize the necessity of improving teaching and learning in the clinical context to assure that graduating students reach an adequate level of clinical competence. Conclusions: The method for selecting candidates to residency post currently used in Spain, which relies mainly on testing theoretical knowledge, should be changed for an alternative methodology taking into account student’s performance through the course and assessing his/her ability for clinical contextualization of knowledge and level of clinical competence


Subject(s)
Humans , Internship and Residency/organization & administration , Neurosurgery/education , Specialization/trends , Clinical Competence , School Admission Criteria , Aptitude Tests , Health Postgraduate Programs , Educational Measurement
3.
Neurocirugia (Astur) ; 26(2): 53-63, 2015.
Article in Spanish | MEDLINE | ID: mdl-25724619

ABSTRACT

INTRODUCTION: The method for selecting medical graduates for residency positions has a strong influence on teaching and learning strategies in medical schools. The methodology currently used in Spain does not seem appropriate for ranking the candidates or improving curriculum development. Thus, and taking into account the most consistent methodologies used in the United Kingdom and USA, we have designed a new method to be used in our country. OBJECTIVES: To analyze the limitations of the methodology used in Spain, and propose a new one aimed to improve the accuracy of selection itself and avoiding the negative influence of the current method on curricular development. In addition, we emphasize the necessity of improving teaching and learning in the clinical context to assure that graduating students reach an adequate level of clinical competence. CONCLUSIONS: The method for selecting candidates to residency post currently used in Spain, which relies mainly on testing theoretical knowledge, should be changed for an alternative methodology taking into account student,s performance through the course and assessing his/her ability for clínical contextualization of knowledge and level of clinical competence.


Subject(s)
Clinical Competence , Internal Medicine/education , Internship and Residency , Personnel Selection , Humans , Spain
4.
Neurocir. - Soc. Luso-Esp. Neurocir ; 26(1): 3-12, ene.-feb. 2015.
Article in Spanish | IBECS | ID: ibc-133393

ABSTRACT

Introducción: El diseño de una metodología apropiada para la selección de los graduados que acceden a los puestos de residencia tiene gran importancia porque, aparte de su eficiencia en la elección de los candidatos, condiciona decisivamente el funcionamiento curricular en las escuelas de medicina, incluyendo la manera de estudiar y aprender del estudiante y la actitud docente del profesorado y su motivación para perseguir la innovación curricular. En la actualidad existe una gran dispersión en los métodos de selección de los residentes en diferentes países, evidenciando que no hay ninguno perfecto. El uso aislado de criterios tales como el peso del expediente académico, los test de conocimiento teórico, determinadas pruebas prácticas de la competencia clínica, o las entrevistas tienen un valor limitado para predecir qué candidatos van a ser más competentes durante la residencia o la práctica autónoma. Objetivos: Describir las metodologías utilizadas para la selección de los residentes en los países de nuestro entorno prestando especial atención a las empleadas en el Reino Unido y los EE. UU. donde se analiza de manera sistemática el funcionamiento de los currícula en las escuelas de medicina. Se comentan las ventajas y desventajas de los exámenes de ámbito nacional para otorgar el grado y/o construir el listado de acceso a la residencia, y su utilidad para favorecer el proceso de convergencia y armonización de los grados y los programas de residencia a nivel transnacional europeo o internacional. El presente análisis se utiliza para establecer una comparación con la metodología de selección aplicada actualmente en España en un intento de diseñar un nuevo método multicriterio más eficiente que se describirá en otro artículo publicado en el próximo número de esta revista Conclusiones: Los métodos multicriterio para la selección de los residentes en el Reino Unido y los EE. UU. parecen los más consistentes por lo que serán utilizados para construir el nuevo método que podría ser aplicado en España. Aunque muchos expertos en docencia médica rechazan los exámenes de ámbito nacional para otorgar el grado y/o establecer el orden de acceso a los puestos de residencia porque limitan la diversidad y la innovación curriculares, cuando están bien diseñados sirven para verificar el alcance del nivel mínimo aceptable de competencia clínica del graduado sin distorsionar el buen funcionamiento y la mejora progresiva del currículum


Introduction: The design of an appropriate method for the selection of medical graduates for residency posts is extremely important, not only for the efficiency of the method itself (accurate identification of most competent candidates), but also for its influence on the study and teaching methodologies operating in medical schools. Currently, there is a great variation in the criteria used in different countries and there is no definitively appropriate method. The use of isolated or combined criteria, such as the marks obtained by students in medical schools, their performance in tests of theoretical knowledge and evaluations of clinical competence, or personal interviews, have a limited value for identifying those candidates who will perform better during the residency and later on during independent practice. Objectives: To analyse the variability in the methodologies used for the selection of residents employed in different countries, in particular those used in the United Kingdom and USA, where external agencies and medical schools make systematic analyses of curriculum development. The advantages and disadvantages of national or transnational licensing examinations on the process of convergence and harmonization of medical degrees and residency programmes through Europe are discussed. The present analysis is used to design a new and more efficient multi-criteria methodology for resident selection in Spain, which will be published in the next issue of this journal. Conclusions: Since the multi-criteria methods used in UK and USA appear to be most consistent, these have been employed for designing the new methodology that could be applied in Spain. Although many experts in medical education reject national examinations for awarding medical degrees or ranking candidates for residency posts, it seems that, when appropriately designed, they can be used to verify the level of competence of graduating students without necessarily distorting curriculum implementation or improvement


Subject(s)
Humans , Internship and Residency/organization & administration , Medical Staff, Hospital/statistics & numerical data , Specialization , Professional Competence , Job Description
5.
Neurocirugia (Astur) ; 26(1): 3-12, 2015.
Article in Spanish | MEDLINE | ID: mdl-25600341

ABSTRACT

INTRODUCTION: The design of an appropriate method for the selection of medical graduates for residency posts is extremely important, not only for the efficiency of the method itself (accurate identification of most competent candidates), but also for its influence on the study and teaching methodologies operating in medical schools. Currently, there is a great variation in the criteria used in different countries and there is no definitively appropriate method. The use of isolated or combined criteria, such as the marks obtained by students in medical schools, their performance in tests of theoretical knowledge and evaluations of clinical competence, or personal interviews, have a limited value for identifying those candidates who will perform better during the residency and later on during independent practice. OBJECTIVES: To analyse the variability in the methodologies used for the selection of residents employed in different countries, in particular those used in the United Kingdom and USA, where external agencies and medical schools make systematic analyses of curriculum development. The advantages and disadvantages of national or transnational licensing examinations on the process of convergence and harmonization of medical degrees and residency programmes through Europe are discussed. The present analysis is used to design a new and more efficient multi-criteria methodology for resident selection in Spain, which will be published in the next issue of this journal. CONCLUSIONS: Since the multi-criteria methods used in UK and USA appear to be most consistent, these have been employed for designing the new methodology that could be applied in Spain. Although many experts in medical education reject national examinations for awarding medical degrees or ranking candidates for residency posts, it seems that, when appropriately designed, they can be used to verify the level of competence of graduating students without necessarily distorting curriculum implementation or improvement.


Subject(s)
Internship and Residency , Personnel Selection/methods , Spain , United Kingdom , United States
6.
Clin Neurophysiol ; 125(2): 231-8, 2014 Feb.
Article in English | MEDLINE | ID: mdl-23972389

ABSTRACT

OBJECTIVES: To evaluate the lateralizing and localizing values of interictal focal slow activity (IFSA), single pulse electrical stimulation (SPES) and (18)FDG PET, in order to estimate their potential to complement ictal intracranial recordings and reduce prolonged monitoring in patients with temporal lobe epilepsy. METHODS: The study includes 30 consecutive patients with bilateral temporal subdural electrodes and focal seizure onset. IFSA, SPES and (18)FDG PET when available, were visually assessed and their combined lateralization was based on the majority of the individual lateralizing tests. RESULTS: In the 18 patients who had all three tests, lateralization was congruent with seizure onset areas in 15 (83%). When lateralized (15 patients), (18)FDG PET was always congruent with intracranial seizure onset. In all 12 patients without (18)FDG PET, lateralization combining IFSA and SPES was congruent with seizure onset, including two with bilateral independent seizure onset on subdural monitoring. 22 out of the 23 patients who had surgery enjoyed favorable outcome (Engel I or II). CONCLUSION: Intracranial IFSA and SPES can reliably predict the side and site (mesial versus lateral temporal) of seizure onset when they lateralize to the same side. SIGNIFICANCE: (18)FDG PET can be useful in planning electrode implantation. During intracranial recordings, IFSA and SPES have the potential to reduce telemetry time, risks and costs.


Subject(s)
Epilepsy, Temporal Lobe/diagnostic imaging , Seizures/diagnostic imaging , Subdural Space/diagnostic imaging , Adolescent , Adult , Electric Stimulation , Electrodes, Implanted , Electroencephalography , Epilepsy, Temporal Lobe/physiopathology , Epilepsy, Temporal Lobe/surgery , Female , Humans , Male , Middle Aged , Radionuclide Imaging , Seizures/physiopathology , Seizures/surgery , Subdural Space/physiopathology , Subdural Space/surgery , Treatment Outcome
7.
Clin Neurophysiol ; 123(9): 1736-44, 2012 Sep.
Article in English | MEDLINE | ID: mdl-22410162

ABSTRACT

OBJECTIVE: To describe neuronal firing patterns observed during human spontaneous interictal epileptiform discharges (IEDs) and responses to single pulse electrical stimulation (SPES). METHODS: Activity of single neurons was recorded during IEDs and after SPES in 11 consecutive patients assessed with depth EEG electrodes and attached microelectrodes. RESULTS: A total of 66 neurons were recorded during IEDs and 151 during SPES. We have found essentially similar patterns of neuronal firing during IEDs and after SPES, namely: (a) a burst of high frequency firing lasting less than 100 ms (in 39% and 25% of local neurons, respectively for IED and SPES); (b) a period of suppression in firing lasting around 100-1300 ms (in 19% and 14%, respectively); (c) a burst followed by suppression (in 10% and 12%, respectively); (d) no-change (in 32% and 50%, respectively). CONCLUSIONS: The similarities in neuronal firing patterns associated with IEDs and SPES suggest that, although both phenomena are initiated differently, they result in the activation of a common cortical mechanism, probably initiated by brief synchronised burst firing in some cells followed by long inhibition. SIGNIFICANCE: The findings provide direct in vivo human evidence to further comprehend the pathophysiology of human focal epilepsy.


Subject(s)
Action Potentials/physiology , Brain Waves/physiology , Brain/pathology , Epilepsy/pathology , Epilepsy/physiopathology , Neurons/physiology , Adult , Electric Stimulation/methods , Electrodes, Implanted , Electroencephalography/methods , Female , Humans , Male , Middle Aged , Young Adult
8.
Opt Lett ; 36(9): 1560-2, 2011 May 01.
Article in English | MEDLINE | ID: mdl-21540927

ABSTRACT

We propose and demonstrate the use of a single semiconductor optical amplifier (SOA) and optical filtering to time demultiplex tributaries from an optical time division multiplexing-differential phase shift keying (OTDM-DPSK) signal. The scheme takes advantage of the fact that phase variations added to the target channel by cross-phase modulation from the control signal are effectively subtracted in the differential demodulation scheme employed for DPSK signals. Demultiplexing from 80 to 40 Gbit/s is demonstrated with moderate power penalty using an SOA with recovery time twice as long as the bit period at 80 Gbit/s. Large dynamic ranges for the input power and SOA current are experimentally demonstrated. The scheme is expected to be scalable toward higher bit rates.

9.
Opt Express ; 19(1): 155-61, 2011 Jan 03.
Article in English | MEDLINE | ID: mdl-21263552

ABSTRACT

Although patterning effects (PEs) are known to be a limiting factor of ultrafast photonic switches based on semiconductor optical amplifiers (SOAs), a simple approach for their evaluation in numerical simulations and experiments is missing. In this work, we experimentally investigate and verify a theoretical prediction of the pseudo random binary sequence (PRBS) length needed to capture the full impact of PEs. A wide range of SOAs and operation conditions are investigated. The very simple form of the PRBS length condition highlights the role of two parameters, i.e. the recovery time of the SOAs as well as the operation bit rate. Furthermore, a simple and effective method for probing the maximum PEs is demonstrated, which may relieve the computational effort or the experimental difficulties associated with the use of long PRBSs for the simulation or characterization of SOA-based switches. Good agrement with conventional PRBS characterization is obtained. The method is suitable for quick and systematic estimation and optimization of the switching performance.

10.
Clin Neurophysiol ; 122(2): 244-52, 2011 Feb.
Article in English | MEDLINE | ID: mdl-20675188

ABSTRACT

OBJECTIVE: To determine the reliability of latency analysis in lateralising the origin of epileptiform discharges in pre-surgical assessment of Landau-Kleffner syndrome (LKS). METHODS: A computer aided-method was developed to identify leading regions and measure inter-hemispheric latencies before and after averaging discharges. Scalp and intracranial EEG recordings were studied from seven patients undergoing surgical treatment. The laterality suggested by latency analysis was compared with that suggested by pharmacological tests. RESULTS: Latency analysis of bilateral discharges showed a consistent leading hemisphere. The earliest low-amplitude deflections were located in temporal regions in all patients. Contralateral low-amplitude deflections, and ipsilateral and contralateral earliest large negative peaks were recorded in temporal and less frequently in parasagittal regions. Presurgical inter-hemispheric latencies ranged between 8 and 48 ms for the deflections and between 4 and 30 ms for the peaks. The leading hemisphere identified by latency analysis of the earliest low-amplitude deflections coincided with that suggested by pharmacological tests in all 7 patients, whereas latency of later components coincided in 6. CONCLUSIONS: Latency analysis appears to be a reliable method to estimate the hemisphere driving bilateral discharges in LKS. SIGNIFICANCE: It can be carried out non-invasively and could be used to confirm, and eventually replace, results from pharmacological tests.


Subject(s)
Electroencephalography/methods , Landau-Kleffner Syndrome/diagnosis , Landau-Kleffner Syndrome/physiopathology , Reaction Time/physiology , Brain/physiopathology , Child , Child, Preschool , Follow-Up Studies , Humans , Landau-Kleffner Syndrome/surgery
11.
Opt Express ; 18(20): 21121-30, 2010 Sep 27.
Article in English | MEDLINE | ID: mdl-20941008

ABSTRACT

We comprehensively analyze multiple WDM channels RZ-to-NRZ format conversion using a single microring resonator. The scheme relies on simultaneous suppression of the first order harmonic components in the spectra of all the RZ channels. An optimized silicon microring resonator with free spectral range of 100 GHz and Q value of 7900 is designed and fabricated for this purpose. Multi-channel RZ-to-NRZ format conversion is demonstrated experimentally at 50 Gbit/s for WDM channels with 200 GHz channel spacing using the fabricated device. Bit error rate (BER) measurements show very good conversion performances for the scheme.

12.
Epilepsia ; 50(7): 1793-803, 2009 Jul.
Article in English | MEDLINE | ID: mdl-19453705

ABSTRACT

PURPOSE: The usefulness of single-pulse electrical stimulation (SPES) during intracranial recordings was evaluated in a pediatric population. This method is useful in identifying epileptogenic cortex in adult subjects. METHODS: We studied 35 children who were undergoing intracranial electroencephalography (EEG) recordings from two hospitals (King's College Hospital and Great Ormond Street Hospital for Sick Children, London, United Kingdom). In each patient we studied all available contacts using a series of 10 or more single, brief (1ms) electrical stimuli. The cortical responses were reviewed in detail. The data were examined for associations between response type, ictal onset zone, lesion boundary, and seizure outcome. RESULTS: We identified cortical responses to SPES that were similar to those reported in adults. In agreement with previous studies we found that two types of responses ("delayed" and "repetitive" responses) were associated with the ictal onset zone and the area of the presumed epileptogenic lesion. When these responses were present (54% of cases), the removal of the entire area responsible for the abnormal responses to SPES was associated with good outcome. CONCLUSION: Cortical responses to SPES in children provide new and additional information in the investigation of epileptogenic cortex in children during assessment for epilepsy surgery. This may improve the outcome for this difficult but important group.


Subject(s)
Brain Mapping/methods , Cerebral Cortex/physiopathology , Electric Stimulation/methods , Electroencephalography/statistics & numerical data , Epilepsy/diagnosis , Adolescent , Adult , Brain Mapping/statistics & numerical data , Child , Electrodes, Implanted , Electroencephalography/methods , Epilepsy/physiopathology , Epilepsy/surgery , Female , Humans , Male , Preoperative Care
13.
Opt Express ; 16(3): 2005-14, 2008 Feb 04.
Article in English | MEDLINE | ID: mdl-18542280

ABSTRACT

We outline a novel method performing all-optical envelope detection of radio-frequency signals for radio-over-fiber links. A high frequency modulated signal with a slower-varying envelope is injected into a DFB laser which, due to gain suppression effects, recovers only the envelope of the optical signal. We characterize the DFB gain suppression effect in terms of injected signal wavelength and power level requirements. System performance is assessed, including experimental bit-error rate results; these illustrate successful envelope detection for a 20 GHz carrier with ASK modulation operating at 2.5 Gbit/second. Preliminary results at 5.5 Gbit/s show significant potential for application in hybrid optical-wireless communications networks.


Subject(s)
Communication , Computer-Aided Design , Fiber Optic Technology/instrumentation , Lasers , Microwaves , Models, Theoretical , Computer Simulation , Equipment Design , Equipment Failure Analysis , Radio Waves
14.
Epilepsia ; 49(3): 470-80, 2008 Mar.
Article in English | MEDLINE | ID: mdl-18028404

ABSTRACT

PURPOSE: To evaluate the use of EEG responses to transcranial magnetic stimulation (TMS-EEG responses) as a noninvasive tool for the diagnosis of focal epilepsy. METHODS: Fifteen patients and 15 healthy subjects were studied. TMS at an intensity set at resting corticomotor threshold were delivered at the standard EEG electrode positions. For each position, EEG responses to TMS were evaluated before and after averaging EEG recordings synchronized with the TMS pulse. RESULTS: Two types of TMS-EEG responses were seen: (A) early responses: consisting of a single slow wave seen after the TMS pulse; and (B) late TMS-EEG responses, which were subclassified into (b.1) delayed responses: waveforms resembling interictal epileptiform discharges induced by TMS; or (b.2) repetitive responses: onset of a new rhythym induced by TMS. Early responses were observed in patients and healthy subjects when stimulating at various sites and were considered normal responses to TMS. Late TMS-EEG responses were not seen in healthy subjects, whereas they were seen in 11 of the 15 epileptic patients. Late TMS-EEG responses occurred when stimulating the epileptogenic side in eight out of the nine patients who had lateralized late TMS-EEG responses. The combined use of late TMS-EEG responses and interictal scalp EEG would have suggested the diagnosis of focal epilepsy in all patients, despite the absence of late TMS-EEG responses in four patients and the presence of normal interictal scalp EEG in three. CONCLUSIONS: TMS-EEG responses can identify epileptogenic cortex and may substantially improve the diagnosis of focal epilepsy, particularly, if combined with standard EEG studies.


Subject(s)
Brain Mapping/methods , Cerebral Cortex/physiopathology , Electroencephalography/statistics & numerical data , Epilepsies, Partial/diagnosis , Epilepsies, Partial/physiopathology , Transcranial Magnetic Stimulation/statistics & numerical data , Adolescent , Adult , Control Groups , Electrodes, Implanted , Electroencephalography/methods , Female , Frontal Lobe/physiopathology , Functional Laterality/physiology , Humans , Male , Middle Aged , Monitoring, Physiologic/methods , Monitoring, Physiologic/statistics & numerical data , Prefrontal Cortex/physiopathology , Preoperative Care/methods , Transcranial Magnetic Stimulation/methods
16.
Lancet Neurol ; 4(11): 718-26, 2005 Nov.
Article in English | MEDLINE | ID: mdl-16239178

ABSTRACT

BACKGROUND: Abnormal late responses to single pulse electrical stimulation (SPES) in patients with intracranial recordings can identify epileptogenic cortex. We aimed to investigate the presence of neuropathological abnormalities in abnormal SPES areas and to establish if removal of these areas improved postsurgical seizure control. METHODS: We studied abnormal responses to SPES during chronic intracranial recordings in 40 consecutive patients who were thereafter operated on because of refractory epilepsy and had a follow-up period of at least 12 months. FINDINGS: 22 patients had abnormal responses to SPES exclusively located in resected regions (96% with favourable outcome), seven had abnormal responses to SPES located in resected and non-resected regions (71% with favourable outcome), three had abnormal responses to SPES exclusively outside the resected region (none with favourable outcome), and eight did not have abnormal responses to SPES (62.5% with favourable outcome). Surgical outcome was significantly better when areas with abnormal responses to SPES were completely resected compared with partial or no removal of abnormal SPES areas (p=0.006). Neuropathological examination showed structural abnormalities in the abnormal SPES areas in 26 of the 29 patients in whom these regions were resected, despite the absence of clear MRI abnormalities in nine patients. INTERPRETATION: Abnormal responses to SPES are functional markers of epileptogenic structural abnormalities, and can identify epileptogenic cortex and predict surgical outcome, especially when a frontal or temporal focus is suspected.


Subject(s)
Electrodiagnosis , Neurosurgical Procedures , Seizures/diagnosis , Seizures/surgery , Adolescent , Adult , Brain Neoplasms/complications , Brain Neoplasms/surgery , Cerebral Cortex/pathology , Child , Child, Preschool , Electric Stimulation , Electrodes, Implanted , Electroencephalography , Female , Frontal Lobe/surgery , Humans , Magnetic Resonance Imaging , Male , Middle Aged , Prospective Studies , Seizures/pathology , Temporal Lobe/surgery , Treatment Outcome
17.
Clin Neurophysiol ; 115(6): 1423-35, 2004 Jun.
Article in English | MEDLINE | ID: mdl-15134711

ABSTRACT

OBJECTIVE: To determine scalp characteristics of epileptiform discharges arising from medial temporal structures (MT). METHODS: Signal-to-noise ratio was increased by averaging simultaneous recordings from intracranial and scalp electrodes synchronised on discharges recorded by foramen ovale (FO) electrodes. The topography, amplitude and distribution of averaged scalp signals were analysed. RESULTS: Four thousand three hundred and twenty-seven discharges from 20 patients were averaged into 77 patterns. Before averaging, only 9% of discharges were detectable on the scalp without the need of simultaneous FO recordings (SED). A further 72.3% of discharges fell into averaged patterns that could be detected on the scalp as small transients before or after averaging (STBA or STAA). In 18.7% of discharges, no scalp signal was seen after averaging. Whereas most SED patterns had largest amplitude on the scalp at anterior temporal electrodes, STBA and STAA patterns showed greater variability and more widespread scalp fields, suggesting a deeper source. Dipole source localisation modelled the majority of SED patterns as radial dipoles located just behind the eye. In contrast, dipoles corresponding to STBA or STAA patterns showed greater variability in location and orientation and tended to be located at MT. CONCLUSIONS: SED patterns seem to arise from widespread subtemporal and/or superficial neocortical activation, generating EEG fields that are distorted by the high electrical conductivity of anterior cranial foramina. In contrast, STBA and STAA patterns represent electrical fields from neuronal activity more restricted to MT, that reach the scalp highly attenuated by volume-conduction and less distorted by cranial foramina. SIGNIFICANCE: Low amplitude scalp signals can be related to MT activity and must be taken into consideration for the diagnosis of temporal lobe epilepsy, pre-surgical assessment and for valid modelling of deep sources from the scalp EEG and magnetoencephalogram.


Subject(s)
Brain Mapping , Cortical Synchronization , Epilepsy/physiopathology , Scalp/innervation , Temporal Lobe/physiopathology , Adolescent , Adult , Child , Cortical Synchronization/methods , Electrodes , Female , Humans , Male , Middle Aged , Scalp/physiology
18.
J Clin Neurophysiol ; 19(2): 163-71, 2002 Apr.
Article in English | MEDLINE | ID: mdl-11997728

ABSTRACT

The purpose of this study was to quantify the distortion of electrical fields by skull foramina using an in vitro model. Extracranial voltage generated by current dipoles located inside a human calva immersed in saline were measured when a 4-mm hole was open and when it was blocked with paraffin wax. Dipoles were located either along the internal surface of the bone (superficial dipoles) or at increasing distances from the bone (deep dipoles). With the hole open, extracranial signals had a substantially greater amplitude than with the hole blocked. The locations of the largest voltage values recorded outside the skull depended on the distance of the recording electrode from the hole rather than on the location of the internal dipole. For superficial dipoles, voltage values with the hole open were as much as 116 times greater than when the hole was blocked. Furthermore, when the hole was open, the largest extracranial signals were seen at the hole even when the dipole was 5 to 6 cm away from the hole. The effects of skull holes were less prominent for deep dipoles than for superficial dipoles. Skull discontinuities can be major determinants for the distribution of extracranial EEG signals. These results have implications for EEG interpretation and for source localization.


Subject(s)
Electric Conductivity , Electrodes/statistics & numerical data , Electroencephalography/instrumentation , Electroencephalography/methods , Humans , Models, Neurological , Skull/physiology
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