Asunto(s)
Mapeo Encefálico/métodos , Corteza Cerebral/fisiopatología , Electroencefalografía/métodos , Epilepsia/diagnóstico , Mapeo Encefálico/instrumentación , Electroencefalografía/estadística & datos numéricos , Epilepsia/fisiopatología , Epilepsia del Lóbulo Temporal/diagnóstico , Epilepsia del Lóbulo Temporal/fisiopatología , Cabeza/fisiología , Humanos , Imagen por Resonancia Magnética/métodos , Imagen por Resonancia Magnética/estadística & datos numéricos , Modelos Biológicos , Modelos Neurológicos , Células Piramidales/fisiología , Lóbulo Temporal/fisiopatologíaRESUMEN
Intracranial EEG monitoring before epilepsy surgery, while becoming less commonly performed in patients with unilateral mesial temporal lobe epilepsy, is still widely used when bilateral independent temporal lobe seizures are suspected or when extratemporal foci cannot be ruled out by noninvasive means. Additionally, many epilepsy centers are reporting excellent surgical outcome in patients with neocortical temporal lobe epilepsy, when resections are guided by intracranial EEG studies. This article reviews the indications, technical aspects, risks, and interpretation of intracranial EEG in patients with temporal lobe seizures. It also considers intracranial EEG features predictive of surgical outcome.
Asunto(s)
Encéfalo/fisiopatología , Electroencefalografía , Epilepsia del Lóbulo Temporal/fisiopatología , Electrodos Implantados/efectos adversos , Epilepsia del Lóbulo Temporal/cirugía , Humanos , Periodo Intraoperatorio , Neocórtex/fisiopatología , Resultado del TratamientoRESUMEN
Long-term audiovisual scalp EEG monitoring is an essential diagnostic tool for the evaluation of paroxysmal disorders. The definitive classification of both nonepileptic and epileptic events is often possible only with the use of this technique. Assessment of response to treatment and the noninvasive presurgical localization of seizure foci are other important uses. The optimization of both clinical semiology and electrophysiologic data obtained from such studies is the subject of significant research efforts. Outcomes studies and advanced EEG analysis research should ultimately serve to minimize the cost of this valuable technique as well as maximizing its utility.
Asunto(s)
Electroencefalografía , Epilepsia , Adulto , Niño , Preescolar , Electroencefalografía/economía , Electroencefalografía/métodos , Epilepsia/diagnóstico , Epilepsia/tratamiento farmacológico , Epilepsia/fisiopatología , Humanos , Pacientes Internos , Monitoreo Fisiológico , Grabación en VideoRESUMEN
PURPOSE: We investigated whether visual and quantitative ictal EEG analysis could predict surgical outcome after anteromesial temporal lobectomy (AMTL) in which mesial structures, basal, and temporal tip cortex were resected. METHODS: We retrospectively reviewed 282 presurgical scalp-recorded ictal EEGs (21- to 27-channel) from 75 patients who underwent AMTL. We examined the pattern of seizure onset (frequency, distribution, and evolution) and estimated the principal underlying cerebral generators by using a multiple fixed dipole model that decomposes temporal lobe activity into four sublobar sources (Focus 1.1). We correlated findings with a 2-year postoperative outcome. RESULTS: Sixteen patients had seizures with a well-lateralized, regular 5 to 9-Hz rhythm at onset, that most often had a temporal or subtemporal distribution. All patients became seizure free after surgery. In 51 patients, seizure onset was remarkable for lateralized slow rhythms (<5 Hz), which sometimes appeared as periodic discharges, were often irregular and stable only for short periods (<5 s), and had a widespread lateral temporal distribution. Among these a favorable surgical outcome was encountered in patients with seizures having prominent anterior-tip sources ( 16 of 17 seizure free), whereas those with dominant lateral or oblique sources had a less favorable outcome (three of 14 and 13 of 18, respectively). Irregular, nonlateralized slowing characterized seizure onsets in eight patients. Three patients became seizure free after surgery. CONCLUSIONS: Both visual and quantitative sublobar source analysis of scalp ictal EEG can predict surgical outcome in most cases after AMTL and complement non-invasive presurgical evaluation.
Asunto(s)
Electroencefalografía/estadística & datos numéricos , Epilepsia del Lóbulo Temporal/fisiopatología , Epilepsia del Lóbulo Temporal/cirugía , Lóbulo Temporal/fisiopatología , Lóbulo Temporal/cirugía , Electrodos Implantados , Electroencefalografía/clasificación , Epilepsia del Lóbulo Temporal/diagnóstico , Estudios de Seguimiento , Lateralidad Funcional , Hipocampo/fisiopatología , Humanos , Imagen por Resonancia Magnética , Pronóstico , Estudios Retrospectivos , Resultado del TratamientoRESUMEN
PURPOSE: To determine the intracranial EEG features responsible for producing the various ictal scalp rhythms, which we previously identified in a new EEG classification for temporal lobe seizures. METHODS: In 24 patients, we analyzed simultaneous intracranial and surface ictal EEG recordings (64 total channels) obtained from a combination of intracerebral depth, subdural strip, and scalp electrodes. RESULTS: Four of four patients with Type 1 scalp seizure patterns had mesial temporal seizure onsets. However, discharges confined to the hippocampus produced no scalp EEG rhythms. The regular 5- to 9-Hz subtemporal and temporal EEG pattern of Type 1a seizures required the synchronous recruitment of adjacent inferolateral temporal neocortex. Seizure discharges confined to the mesiobasal temporal cortex produced a vertex dominant rhythm (Type 1c) due to the net vertical orientation of dipolar sources located there. Ten of 13 patients with Type 2 seizures had inferolateral or lateral, temporal neocortical seizure onsets. Initial cerebral ictal activity was typically a focal or regional, low voltage, fast rhythm (20-40 Hz) that was often associated with widespread background flattening. Only an attenuation of normal rhythms was reflected in scalp electrodes. Irregular 2- to 4-Hz cortical ictal rhythms that commonly followed resulted in a comparably slow and irregular scalp EEG pattern (Type 2a). Type 2C seizures showed regional, periodic, 1- to 4-Hz sharp waves following intracranial seizure onset. Seven patients had Type 3 scalp seizures, which were characterized by diffuse slowing or attenuation of background scalp EEG activity. This resulted when seizure activity was confined to the hippocampus, when there was rapid seizure propagation to the contralateral temporal lobe, or when cortical ictal activity failed to achieve widespread synchrony. CONCLUSIONS: Type 1, 2, and 3 scalp EEG patterns of temporal lobe seizures are not a reflection of cortical activity at seizure onset. Differences in the subsequent development, propagation, and synchrony of cortical ictal discharges produce the characteristic scalp EEG rhythms.
Asunto(s)
Electroencefalografía/métodos , Epilepsia del Lóbulo Temporal/diagnóstico , Lóbulo Temporal/fisiopatología , Electrodos Implantados , Epilepsia del Lóbulo Temporal/clasificación , Epilepsia del Lóbulo Temporal/fisiopatología , Lateralidad Funcional , HumanosRESUMEN
Magnetoencephalographic (MEG) dipole source localization is a particularly promising new tool for noninvasive presurgical evaluation of epileptogenic foci. It is potentially more accurate than EEG localization techniques because magnetic fields are not attenuated or distorted by the skull and scalp, which allows cerebral sources to be modeled more simply. MEC spike and seizure sources are routinely co-registered with the patient's brain MRI for clinical interpretation. This has been called magnetic source imaging. Numerous studies have shown that MEG localization of foci agreed with lesion position, depth electrode and ECoG data, PET and MRI findings, and surgical success. The recent development of whole head sensor arrays has greatly enhanced the case with which epileptiform magnetic fields can be recorded and analyzed.