Long-term electrocorticographic monitoring and pathological high-frequency oscillations in tumor-related epilepsy
Special issue of Epilepsia dedicated to the 31stInternational Epilepsy Congress Istanbul, Turkey 5th–9th September, 2015
Phase synchronization among neuronal oscillations within the same frequency band has been hypothesized to be a major mechanism for communication between different brain areas. On the other hand, cross-frequency communications are more flexible allowing interactions between oscillations with different frequencies. Among such cross-frequency interactions amplitude-to-amplitude interactions are of a special interest as they show how the strength of spatial synchronization in different neuronal populations relates to each other during a given task. While, previously, amplitude-to-amplitude correlations were studied primarily on the sensor level, we present a source separation approach using spatial filters which maximize the correlation between the envelopes of brain oscillations recorded with electro-/magnetoencephalography (EEG/MEG) or intracranial multichannel recordings. Our approach, which is called canonical source power correlation analysis (cSPoC), is thereby capable of extracting genuine brain oscillations solely based on their assumed coupling behavior even when the signal-to-noise ratio of the signals is low. In addition to using cSPoC for the analysis of cross-frequency interactions in the same subject, we show that it can also be utilized for studying amplitude dynamics of neuronal oscillations across subjects. We assess the performance of cSPoC in simulations as well as in three distinctively different analysis scenarios of real EEG data, each involving several subjects. In the simulations, cSPoC outperforms unsupervised state-of-the-art approaches. In the analysis of real EEG recordings, we demonstrate excellent unsupervised discovery of meaningful power-to-power couplings, within as well as across subjects and frequency bands.
Pharmacoresistant epilepsy is a chronic neurological condition in which a basal brain hyperexcitability results in paroxysmal hypersynchronous neuronal discharges. Human temporal lobe epilepsy has been associated with dysfunction or loss of the potassium-chloride cotransporter KCC2 in a subset of pyramidal cells in the subiculum, a key structure generating epileptic activities. KCC2 regulates intraneuronal chloride and extracellular potassium levels by extruding both ions. Absence of effective KCC2 may alter the dynamics of chloride and potassium levels during repeated activation of GABAergic synapses due to interneuron activity. In turn, such GABAergic stress may itself affect Cl− regulation. Such changes in ionic homeostasis may switch GABAergic signaling from inhibitory to excitatory in affected pyramidal cells and also increase neuronal excitability. Possibly these changes contribute to periodic bursting in pyramidal cells, an essential component in the onset of ictal epileptic events. We tested this hypothesis with a computational model of a subicular network with realistic connectivity. The pyramidal cell model explicitly incorporated the cotransporter KCC2 and its effects on the internal/external chloride and potassium levels. Our network model suggested the loss of KCC2 in a critical number of pyramidal cells increased external potassium and intracellular chloride concentrations leading to seizure-like field potential oscillations. These oscillations included transient discharges leading to ictal-like field events with frequency spectra as in vitro. Restoration of KCC2 function suppressed seizure activity and thus may present a useful therapeutic option. These simulations therefore suggest that reduced KCC2 cotransporter activity alone may underlie the generation of ictal discharges.
33rd international Epilepsy Congress Bangkok, Thailand | 22–26 June 2019 Satellite Symposia Abstracts
Abstracts of the 12th European Congress on Epileptology
Research on comparative efficаcy and tolerability of monotherapy with Depakine chronosphere, drugs of Carbamazepine group with ex- tended release and oxcarbazepine in symptomatic and cryptogenic focal epilepsy has been conducted at Svt. Luka’s Institute of Child Neurol- ogy and Epilepsy (ICNE) (Moscow). This retrospective study covers a random sample of patients treated in ICNE in the period from Decem- ber 1, 2013 to September 1, 2014. The study included 131 patients aged 1 to 18 years with symptomatic and cryptogenic focal epilepsy receiving treatment with one of the study drugs in monotherapy: group 1 - monotherapy with Depakine chronosphere (n = 56); group 2 - monotherapy with drugs of carbamazepine group with extended release (n = 55); group 3 - monotherapy with oxcarbazepine (trileptal) (n = 20).The obtained results allow us to conclude that the effectiveness of Depakin chronosphere, carbamazepine with extended release and oxcar- bazepine in monotherapy of symptomatic and cryptogenic focal epilepsy was comparable (statistically significant differences in efficacy were not found). However, carbamazepine was awarded the highest frequency of seizures aggravation.Drugs showed approximately same tolerability (statistically significant differences in tolerability were not found). However, withdrawal of the drug due to side effects was the rarest in Depakine (3.5 %), and withdrawal due to intolerance was higher in carbamazepine and oxcarbazepine (5 and 10 % respectively).Depakinum and oxcarbazepine had the best results in the blocking of pathological activity on the electroencephalogram, whereas carbam- azepine was clearly inferior to them. In this regard, complete clinical-electroencephalographic remission (lasting 12 months or more) was achieved under treatment of Depakine chromosphere in 21.5 % of cases, oxcarbazepine - 20 %, and carbamazepine - only 11 %. Holding on therapy for 12 months was similar in all study drugs.Considering that the objective of epilepsy treatment is to achieve complete control over seizures, or at least substantially reduce and weaken them in the absence of significant side effects that disturb the patient’s quality of life, it can be concluded that the best treatment results were obtained in group of depakine chronosphere therapy.