Discovery of recurrent multiple brain states in non-convulsive status epilepticus

Objective We study burst-like patterns of epileptiform discharges in non-convulsive status epilepticus (SE). Methods Epileptiform burst-like transients were identified by estimating the amplitude envelope of the EEG signal, and recurrence and similarities were identified by pairwise matching in the time-domain. Results We identified similarities in the onset of a significant fraction of the epileptiform bursts, and a bimodal distribution of the burst durations. Conclusions Bursts of epileptiform discharges during a non-convulsive SE are manifestations of multiple patterns of recurring brain states. Significance Quantitative description of ictal phenomena in epilepsy and status epilepticus adds to the knowledge of abnormal brain behavior and may assist in improved patient care

Dynamica van het brein

Een van de standaard procedures op een afdeling Klinische Neurofysiologie is het meten van een Elektro-EncefaloGram (EEG). In Nederland worden naar schatting ruim 150-duizend EEG’s per jaar gemaakt om eventuele afwijkingen in hersenfuncties te kunnen vaststellen. Bij een gewone EEG-registratie worden 21 elektroden op de schedel aangebracht, waarmee op de schedelhuid elektrische signalen van ongeveer 10-100 μV gemeten kunnen worden, maar voor sommige indicaties is het aantal elektroden groter dan honder

Small-world characteristics of EEG patterns in post-anoxic encephalopathy

Post-anoxic encephalopathy (PAE) has a heterogenous outcome which is difficult to predict. At present, it is possible to predict poor outcome using somatosensory evoked potentials in only a minority of the patients at an early stage. In addition, it remains difficult to predict good outcome at an early stage. Network architecture, as can be quantified with continuous electroencephalography (cEEG), may serve as a candidate measure for predicting neurological outcome. Here, we explore whether cEEG monitoring can be used to detect the integrity of neural network architecture in patients with PAE after cardiac arrest. From 56 patients with PAE treated with mild therapeutic hypothermia, 19-channel cEEG data were recorded starting as soon as possible after cardiac arrest. Adjacency matrices of shared frequencies between 1 and 25Hz of the EEG channels were obtained using Fourier transformations. Number of network nodes and connections, clustering coefficient (C), average path length (L), and small-world index (SWI) were derived. Outcome was quantified by the best cerebral performance category (CPC)-score within 6months. Compared to non-survivors, survivors showed significantly more nodes and connections. L was significantly higher and C and SWI were significantly lower in the survivor group than in the non-survivor group. The number of nodes, connections, and the L were negatively correlated with the CPC-score. C and SWI correlated positively with the CPC-score. The combination of number of nodes, connections, C, and L showed the most significant difference and correlation between survivors and non-survivors and CPC-score. Our data might implicate that non-survivors have insufficient distribution and differentiation of neural activity for regaining normal brain function. These network differences, already present during hypothermia, might be further developed as early prognostic markers. The predictive values are however still inferior to current practice parameters. Keywords: small-world network, continuous EEG, post-anoxic encephalopathy, prognosis, resuscitatio

Reduced Synaptic Vesicle Recycling during Hypoxia in Cultured Cortical Neurons

Improvement of neuronal recovery in the ischemic penumbra, an area around the core of a brain infarct with some remaining perfusion, has a large potential for the development of therapy against acute ischemic stroke. However, mechanisms that lead to either recovery or secondary damage in the penumbra largely remain unclear. Recent studies in cultured networks of cortical neurons showed that failure of synaptic transmission (referred to as synaptic failure) is a critical factor in the penumbral area, but the mechanisms that lead to synaptic failure are still under investigation. Here we used a Styryl dye, FM1-43, to quantify endocytosis and exocytosis in cultures of rat cortical neurons under normoxic and hypoxic conditions. Hypoxia in cultured cortical networks rapidly depressed endocytosis and, to a lesser extent, exocytosis. These findings support electrophysiological findings that synaptic failure occurs quickly after the induction of hypoxia, and confirms that the failing processes are at least in part presynaptic

Diffusing Substances during Spreading Depolarization: Analytical Expressions for Propagation Speed, Triggering, and Concentration Time Courses

Spreading depolarization (SD) is an important phenomenon in stroke and migraine. However, the processes underlying the propagation of SD are still poorly understood, and an elementary model that is both physiological and quantitative is lacking. We show that, during the onset and propagation of SD, the concentration time courses of excitatory substances such as potassium and glutamate can be described with a reaction- diffusion equation. This equation contains four physiological parameters: (1) a concentration threshold for excitation; (2) a release rate; (3) a removal rate; and (4) an effective diffusion constant. Solving this equation yields expressions for the propagation velocity, concentration time courses, and the minimum stimulus that can trigger SD. This framework allows for analyzing experimental results in terms of these four parameters. The derived time courses are validated with measurements of potassium in rat brain tissue. © 2013 the authors

Single pulse versus pulse train cutaneous electrical stimulation during cold pressor test.

In the present study the effect of the cold pressor test (CPT) on the processing of electrical single pulses (SP) with changing amplitude and pulse trains (PT) with fixed amplitude was analysed using subjective pain ratings and evoked potentials. Healthy subjects were electrically stimulated at the left middle fingertip in a CPT and control protocol. In the CPT protocol the hand was immersed in water of 0-1°C; in the control protocol in water of 32°C. A total of 105 stimuli were applied in a protocol of five different stimulus amplitudes or number of pulses (NoP). The results showed a decrease of amplitude of EP wave components and decrease of subjective ratings by CPT, for both SP and PT. The relationship between NRS or EP amplitude and stimulus amplitude (SP) or NoP (PT) was unchanged by CPT

Predicting success of vagus nerve stimulation (VNS) from interictal EEG

AbstractPurposeVagus nerve stimulation (VNS) has shown to be an effective treatment for drug resistant epilepsy in numerous patients, however, not in all. It is still not possible to predict which patients will profit from VNS. In this pilot study, we explore predictive interictal EEG features for seizure reduction after VNS.Methods19 Patients with medically refractory epilepsy and an implanted VNS system were included. Interictal EEG registrations, recorded before implantation, were retrospectively analysed. A quantative symmetry measure, the pair wise derived brain symmetry index (pdBSI), was tested to predict VNS outcome. Reduction in seizure frequency was used to define the responders.Results10 Patients did respond to VNS, of whom 7 patients had a seizure reduction of at least 50% in a follow-up period of 2 years. On average, we find higher pdBSI values for delta, theta, alpha and beta bands for non-responders than for responders. The average pdBSI of the theta and alpha bands could significantly discriminate between responders and non-responders.ConclusionIn this study, quantifying EEG symmetry using the pdBSI shows promising results in predicting the reduction of seizure frequency after VNS treatment