Region Of Epileptic Focus Research Articles

Comparison of Ensemble Machine Learning Methods for Automated Classification of Focal and Non-Focal Epileptic EEG Signals

This research presents the epileptic focus region localization during epileptic seizures by applying different signal processing and ensemble machine learning techniques in intracranial recordings of electroencephalogram (EEG). Multi-scale Principal Component Analysis (MSPCA) is used for denoising EEG signals and the autoregressive (AR) algorithm will extract useful features from the EEG signal. The performances of the ensemble machine learning methods are measured with accuracy, F-measure, and the area under the receiver operating characteristic (ROC) curve (AUC). EEG-based focus area localization with the proposed methods reaches 98.9% accuracy using the Rotation Forest classifier. Therefore, our results suggest that ensemble machine learning methods can be applied to differentiate the EEG signals from epileptogenic brain areas and signals recorded from non-epileptogenic brain regions with high accuracy.

FNIRS-EEG study of focal interictal epileptiform discharges

Functional near-infrared spectroscopy (fNIRS) acquired with electroencephalography (EEG) is a relatively new non-invasive neuroimaging technique with potential for long term monitoring of the epileptic brain. Simultaneous EEG-fNIRS recording allows the spatio-temporal reconstruction of the hemodynamic response in terms of the concentration changes in oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) associated with recorded epileptic events such as interictal epileptic discharges (IEDs) or seizures. While most previous studies investigating fNIRS in epilepsy had limitations due to restricted spatial coverage and small sample sizes, this work includes a sufficiently large number of channels to provide an extensive bilateral coverage of the surface of the brain for a sample size of 40 patients with focal epilepsies. Topographic maps of significant activations due to each IED type were generated in four different views (dorsal, frontal, left and right) and were compared with the epileptic focus previously identified by an epileptologist. After excluding 5 patients due to the absence of IEDs and 6 more with mesial temporal foci too deep for fNIRS, we report that significant HbR (respectively HbO) concentration changes corresponding to IEDs were observed in 62% (resp. 38%) of patients with neocortical epilepsies. This HbR/HbO response was most significant in the epileptic focus region among all the activations in 28%/21% of patients.

Clinical factors associated with postictal headache in Chinese patients with partial epilepsy

PurposeTo investigate the incidence of postictal headache (PIH) and the factors potentially related to the occurrence of PIH in a Chinese epileptic center. MethodsConsecutive adult patients with epilepsy, referred to the outpatient clinic of the Epilepsy Center of the PLA General Hospital between February 01, 2012, and May 10, 2013, were recruited to this study. 854 patients with partial epilepsy completed a questionnaire regarding headache, 466 patients with temporal lobe epilepsy (TLE), 82 patients with occipital lobe epilepsy (OLE) and 306 patients with frontal lobe epilepsy (FLE). A semi-structured interview was performed in those who confirmed headache. ResultsPIH occurred in 328 (38.41%) of the subjects. By type of epilepsy, PIH was found in 164 (35.19%) of the patients with TLE, 46 (56.01%) of the patients with OLE, and 118 (38.56%) of the patients with FLE. The incidence of PIH in OLE was significantly higher than in TLE and FLE (P<0.05). It occurs more frequently after generalized tonic–clonic seizures than other seizure types. Logistic regression analysis revealed that age at onset, type of seizure and classification of epilepsy were each significantly related to the occurrence of PIH. ConclusionThe results of our study revealed possible relationships between PIH and the region of epileptic focus and area of spread of epileptic discharges.

Impact of seizure activity on free extracellular phenytoin concentrations in amygdala-kindled rats

Access of antiepileptic drugs (AEDs) to the epileptic focus region is considered to be influenced by seizure-associated changes in blood–brain barrier (BBB) function and blood flow. Enhanced leakiness of the BBB has been reported as a consequence of seizure activity, and this is controversially discussed to either favor accumulation of AEDs in epileptic tissue or to limit free extracellular concentrations of AEDs due to enhanced protein extravasation. On the other hand, multidrug transporter overexpression has been described following seizure activity, which can limit brain penetration of AEDs in brain regions involved in seizure generation and spread. Aim of the present study was to determine, how these complex alterations at the BBB influence penetration of a standard AED to the site of seizure initiation. Microdialysis experiments were performed in amygdala-kindled rats and in electrode-implanted, non-kindled rats with the microdialysis probe located directly adjacent to the stimulation-recording depth electrode. Penetration of the AED phenytoin to the extracellular fluid in the focus region was investigated at different time points in relation to seizure activity elicited in kindled rats. Integrity of the BBB was determined by Evans blue. Access of phenytoin to the amygdala proved to be comparable in non-kindled, electrode-implanted control rats and in kindled rats 2 h or fourteen days following a single generalized seizure. When a single generalized seizure was elicited 10 min following phenytoin administration, average phenytoin brain dialysate levels were significantly lower (up to 45%) than those of control animals. During a self-sustained status epilepticus, phenytoin access to the site of seizure initiation tended to be lower in the early phase following drug administration, but reached control level 2 h later. The data clearly demonstrate that seizure-induced alterations in BBB integrity and function do not increase extracellular brain levels of phenytoin in affected brain regions, but rather tend to decrease the free concentration of phenytoin in the extracellular compartment.

P-Glycoprotein-mediated efflux of phenobarbital, lamotrigine, and felbamate at the blood–brain barrier: evidence from microdialysis experiments in rats

Although a series of new antiepileptic drugs (AEDs) have been launched in the last two decades, drug-refractoriness remains a major problem concerning 20–30% of epileptic patients. The fact that most patients with refractory epilepsy are resistant to several AEDs acting via different targets points to an involvement of unspecific mechanisms like changes in local uptake of AEDs in the epileptic focus region. Increased expression of multidrug transporters has been reported in epileptogenic brain tissue from pharmacoresistant patients undergoing epilepsy surgery. However, only limited information exists on the extent to which AEDs are transported by multidrug transporters like P-glycoprotein (PGP). In the present study, the effect of PGP inhibition by verapamil on brain access of the AEDs phenobarbital, lamotrigine, and felbamate was investigated by in vivo microdialysis in rats. Local perfusion of verapamil via the microdialysis probe increased the concentration of the three AEDs in the extracellular fluid of the cerebral cortex in a significant manner. The data indicate that overexpression of PGP in epileptic tissue is likely to limit brain access of the AEDs phenobarbital, lamotrigine, and felbamate, thus favoring the hypothesis that multidrug transporters play a crucial role in the phenomenon of drug-refractory epilepsy.

A comparison of post-ictal headache between patients with occipital lobe epilepsy and temporal lobe epilepsy

We investigated post-ictal headaches (PIH) using a questionnaire to ascertain their characteristics and compare them among different types of epilepsy. The subjects consisted of 34 patients with occipital lobe epilepsy (OLE) and 75 patients with temporal lobe epilepsy (TLE). PIH occurred in 62% of OLE and 23% of TLE (P< 0.05). The quality of pain in PIH was ‘steady’ in 71% of OLE and 29% of TLE (P< 0.05) as opposed to ‘pounding’. Other factors, such as frequency, severity, duration, and accompanying symptoms showed no significant differences. We found very few patients with migraine-like headaches. Analyses of clinical factors, such as age at onset, duration of epilepsy, seizure frequency, family history of headache, and interictal headache did not reveal any relationship to PIH, although generalized tonic–clonic seizures are associated with PIH in TLE (P< 0.05). These results suggest that the nature of PIH may be different between OLE and TLE, and that the region of epileptic focus or spreading area of epileptic discharge may have a close relation to the induction of PIH. An association with migraine, which has been reported previously, was unclear in our study.

Tomografia por emissão de fóton único em epilepsia temporal: estudos intercríticos e críticos com análise visual e semi quantitativa

Single photon emission tomography (SPECT) was performed in 27 patients with refractory complex partial seizures from the temporal lobes due to mesial temporal sclerosis. Independent blinded observers assessed the 28 interictal studies and 9 ictal/postictal studies. Visual analysis of interictal studies detected hypoperfusion in 22, ipsilateral to the epileptogenic zone in 19 (67%) and contralateral in 3 (10.7%). Quantified temporal lobe asymmetry, greater than a previously derived normal range, correctly identified the epileptogenic zone in 16 (61.5%) with false lateralization in 4 (15.3%). In all 9 cases in which they were performed, ictal/postictal studies showed hyperperfusion at the region of epileptic focus. In 3 patients with complex partial seizures followed by symmetric generalized tonic-clonic seizures, hyperperfusion restricted to the temporal lobe was demonstrated. In 5 of these patients the interical studies were unable to demonstrate localized changes. There were no significant correlations between SPECT findings and clinical parameters or EEG slowing in the temporal lobes.