The effect of propofol on effective brain networks

Objective: We compared the effective networks derived from Single Pulse Electrical Stimulation (SPES) in intracranial electrocorticography (ECoG) of awake epilepsy patients and while under general propofol-anesthesia to investigate the effect of propofol on these brain networks. Methods: We included nine patients who underwent ECoG for epilepsy surgery evaluation. We performed SPES when the patient was awake (SPES-clinical) and repeated this under propofol-anesthesia during the surgery in which the ECoG grids were removed (SPES-propofol). We detected the cortico-cortical evoked potentials (CCEPs) with an automatic detector. We constructed two effective networks derived from SPES-clinical and SPES-propofol. We compared three network measures (indegree, outdegree and betweenness centrality), the N1-peak-latency and amplitude of CCEPs between the two effective networks. Results: Fewer CCEPs were observed during SPES-propofol (median: 6.0, range: 0–29) compared to SPES-clinical (median: 10.0, range: 0–36). We found a significant correlation for the indegree, outdegree and betweenness centrality between SPES-clinical and SPES-propofol (respectively r s = 0.77, r s = 0.70, r s = 0.55, p &lt; 0.001). The median N1-peak-latency increased from 22.0 ms during SPES-clinical to 26.4 ms during SPES-propofol. Conclusions: Our findings suggest that the number of effective network connections decreases, but network measures are only marginally affected. Significance: The primary network topology is preserved under propofol.</p

Regional Differences in the Sensitivity of MEG for Interictal Spikes in Epilepsy

MEG interictal spikes as recorded in epilepsy patients are a reflection of intracranial interictal activity. This study investigates the relationship between the estimated sources of MEG spikes and the location, distribution and size of interictal spikes in the invasive ECoG of a group of 38 epilepsy patients that are monitored for pre-surgical evaluation. An amplitude/surface area measure is defined to quantify and rank ECoG spikes. It is found that all MEG spikes are associated with an ECoG spike that is among the three highest ranked in a patient. Among the different brain regions considered, the fronto-orbital, inter-hemispheric, tempero-lateral and central regions stand out. In an accompanying simulation study it is shown that for hypothesized extended sources of larger sizes, as suggested by the data, source location, orientation and curvature can partly explain the observed sensitivity of MEG for interictal spikes

Accurate differentiation between physiological and pathological ripples recorded with scalp-EEG

OBJECTIVE: To compare scalp-EEG recorded physiological ripples co-occurring with vertex waves to pathological ripples co-occurring with interictal epileptiform discharges (IEDs). METHODS: We marked ripples in sleep EEGs of children. We compared the start of ripples to vertex wave- or IED-start, and duration, frequency, and root mean square (RMS) amplitude of physiological and pathological ripples using multilevel modeling. Ripples were classified as physiological or pathological using linear discriminant analysis. RESULTS: We included 40 children with and without epilepsy. Ripples started (χ2(1) = 38.59, p < 0.001) later if they co-occurred with vertex waves (108.2 ms after vertex wave-start) than if they co-occurred with IEDs (4.3 ms after IED-start). Physiological ripples had longer durations (75.7 ms vs 53.0 ms), lower frequencies (98.3 Hz vs 130.6 Hz), and lower RMS amplitudes (0.9 μV vs 1.8 μV, all p < 0.001) than pathological ripples. Ripples could be classified as physiological or pathological with 98 % accuracy. Ripples recorded in children with idiopathic or symptomatic epilepsy seemed to form two subgroups of pathological ripples. CONCLUSIONS: Ripples co-occurring with vertex waves or IEDs have different characteristics and can be differentiated as physiological or pathological with high accuracy. SIGNIFICANCE: This is the first study that compares physiological and pathological ripples recorded with scalp EEG

Neocortical electrical stimulation for epilepsy: Closed-loop versus open-loop

The aim of this review is to evaluate whether open-loop or closed-loop neocortical electrical stimulation should be the preferred approach to manage seizures in intractable epilepsy.Twenty cases of open-loop neocortical stimulation with an implanted device have been reported, in 5 case studies. Closed-loop stimulation with an implanted device has been investigated in a larger number of patients in the RNS System clinical trials. With 230 patients enrolled at the start of the Long-term Treatment Trial, 115 remained at the last reported follow-up. Open-loop stimulation reduced seizure frequency in patients on average with over 90% compared to baseline. Closed-loop stimulation reduces seizure frequency with 60%–65%.Even though open-loop neocortical electrical stimulation has only been reported in 20 patients, and closed-loop in much a larger sample, evidence suggests that both approaches are effective in reducing seizures. It remains an open question which should be clinically preferred. Therefore, a head-to-head adaptive clinical study comparing both approaches is propose