Interictal Period Research Articles

Effects of Vagus Nerve Stimulation on Sustained Seizure Clusters: A Case Report

Seizure clusters (SCs) are acute repetitive seizures with acute episodes of deterioration during seizure control. SCs can be defined as a series of grouped seizures with short interictal periods. Vagus nerve stimulation (VNS) is a treatment option for drug-resistant epilepsy. We present a case where VNS suppressed epileptic SCs, which had persisted for several months. A 13-year-old boy with congenital cerebral palsy and mental retardation had drug-resistant epilepsy with daily jerking movements and spasms in both sides of his body. The seizures were often clustered, and he experienced two sustained SC episodes that persisted for a few months even with prolonged use of continuous intravenous midazolam (IV-MDZ). The patient underwent VNS device placement at the second sustained SC and rapid induction of VNS. Because the tapering of IV-MDZ did not exacerbate the SC, midazolam was discontinued 4 weeks after VNS initiation. Non-refractory SCs also disappeared 10 months after VNS. The seizure severity was improved, and the frequency of seizures reduced from daily to once every few months. The epileptic activity on electroencephalography (EEG) significantly decreased. This case highlights VNS as an additional treatment option for SC. VNS may be a therapeutic option if SC resists the drugs and sustains. Additional studies are necessary to confirm our findings and to investigate how device implantation and stimulation parameters affect the efficacy of VNS.

Pitfalls of Commonly Used Ischemic and Dementia Models Due to Early Seizure by Carotid Ligation.

While the bilateral common carotid artery (CCA) ligation model is widely used in cerebrovascular disease and dementia studies, it can frequently cause seizures. We examined the validity of seizure as an experimental model of ischemia. Eight-week-old male Wistar and Sprague-Dawley (SD) rats were implanted with electrocorticography (ECoG) electrodes and bilateral CCA ligation was performed and compared to the sham groups. ECoG monitoring was used to confirm the seizure discharge and count the number of spikes in the interictal phase 2 h after ligation, followed by power spectral analysis. Magnetic resonance imaging (MRI) was performed 6 h after bilateral CCA ligation to assess fractional anisotropy (FA), apparent diffusion coefficient (ADC), and cerebral blood flow (CBF) values. Magnetic resonance spectroscopy (MRS) was also performed and the ischemic parameters and electrophysiological changes were compared. The Wistar rat group had significantly higher mortality, frequency of seizures, incidence of non-convulsive seizures, and number of spikes in the interictal period compared to those in the SD rat group. Power spectral analysis showed increased power in the delta band in both Wistar and SD rat groups. MRI, after CCA ligation, showed significantly lower ADC values, lower glutamine and glutamate levels, and higher lactate values in Wistar rats, although there was no difference in FA values. Metabolic and electrophysiological changes after CCA ligation differed according to the rat strain. Wistar rats were prone to increased lactate and decreased glutamine and glutamate levels and the development of status epilepticus. Seizures can affect the results of ischemic experiments.

Evaluation of migraine without aura patients by visual evoked potentials with different spatial frequencies

Objective: The objective of our study was to investigate changes in pattern reversal visual evoked potentials (PVEPs) of migraine without aura patients recorded with two different check sizes (15’ and 62’) in accordance with International Society for Clinical Electrophysiology of Vision (ISCEV) standards during the interictal period. 
 Materials and Methods: Patients' demographic data were documented from headache diaries of patients, such as duration of disease, headache characteristics, the number of attacks in a month, the average duration of attacks, complaints accompanying headache, mean severity of headache according to visual analog scale. Twenty migraine patients without aura and 14 healthy volunteers were examined with PVEPs recorded with two different check-sizes (15’ and 62’). The stimulation sequences were randomized both for the check-size of checkerboard and the side of stimulation (right-15', right-62', left-15', left-62'). The latency of N75, P100 and peak-to-peak amplitude of N75-P100 
 were analyzed. 
 Results: There were no statistical difference between healthy subjects and migraine without aura patients in the means of latency and amplitude of PVEPs results for both check-sizes (p>0,05). 
 Conclusion: In migraine patients without aura, we did not detect magnocellular pathway dysfunction by PVEPs with different spatial frequencies. Studies on larger patient groups and combining PVEPs with psychophysical tests are needed.

Dynamic learning framework for epileptic seizure prediction using sparsity based EEG Reconstruction with Optimized CNN classifier

The World Health Organization (WHO) recently stated that epilepsy affects nearly 65 million people of the world population. Early forecast of the oncoming seizures is of paramount importance in saving the life of epileptic patients. This paper demonstrates a phase transition-based seizure prediction approach from multi-channel scalp electroencephalogram (EEG) recordings. The primary focus of this work is to discriminate the seizure and seizure-free EEG signals by learning the dynamics of preictal, interictal and ictal period. We propose an adaptive optimization approach using non-linear conjugate gradient technique in conjunction with Sparsity based EEG Reconstruction (SER) and three-dimensional Optimized Convolutional Neural Network (3D OCNN) classifier, based on Fletcher Reeves (FR) algorithm. Sparsity based artifact removal approach along with a 3D OCNN classifier, classifies the various states of seizures. FR algorithm is deployed with the deep neural network architecture to accelerate the convergence rate and to reduce the complexity of the proposed non-linear model. The Principle Component Analysis (PCA) algorithm replacing the Singular Value Decomposition (SVD) in the K-SVD algorithm, further reduces the time and complexity of the pre-processing stage. We further propose a Phase Transition based Kullback-Leibler divergence (PTB-KL) predictor for obtaining the Optimal Seizure Prediction Horizon (OSPH). The proposed model is evaluated using three diverse databases such as CHB-MIT, NINC and SRM respectively. Empirical results on the three EEG databases of 300 recordings outperforms the state-of-art approaches with an accuracy score of 0.98, sensitivity score of 0.99 and False Prediction Rate (FPR) of 0.07 FP/h. Statistical assessment of the proposed predictor gains an OSPH of about 1.1 h prior to the seizure onset. Experimental results prove that the phase transition-based seizure prediction approach is a promising one for accurate real-time prediction of epilepsy using scalp EEG data.

Increased Phase Cone Turnover in 80-250 Hz Bands Occurs in the Epileptogenic Zone During Interictal Periods.

We found that phase cone clustering patterns in EEG ripple bands demonstrate an increased turnover rate in epileptogenic zones compared to adjacent regions. We employed 256 channel EEG data collected in four adult subjects with refractory epilepsy. The analysis was performed in the 80–150 and 150–250 Hz ranges. Ictal onsets were documented with intracranial EEG recordings. Interictal scalp recordings, free of epileptiform patterns, of 240-s duration, were selected for analysis for each subject. The data was filtered, and the instantaneous phase was extracted after the Hilbert transformation. Spatiotemporal contour plots of the unwrapped instantaneous phase with 1.0 ms intervals were constructed using a montage layout of the 256 electrode positions. Stable phase cone patterns were selected based on criteria that the sign of spatial gradient did not change for a minimum of three consecutive time samples and the frame velocity was consistent with known propagation velocities of cortical axons. These plots exhibited increased dynamical formation and dissolution of phase cones in the ictal onset zones, compared to surrounding cortical regions, in all four patients. We believe that these findings represent markers of abnormally increased cortical excitability. They are potential tools that may assist in localizing the epileptogenic zone.

The Effect of Low Magnesium Concentration on Ictal Discharges In A Non-Synaptic Model.

Magnesium (Mg[Formula: see text] is an essential mineral for several cellular functions. The concentration of this ion below the physiological concentration induces recurrent neuronal discharges both in slices of the hippocampus and in neuronal cultures. These epileptiform discharges are initially sensitive to the application of [Formula: see text]-methyl-D-aspartate (NMDA) receptor antagonists, but these antagonists may lose their effectiveness with prolonged exposure to low [Mg[Formula: see text]], when extracellular Ca[Formula: see text] reduction occurs, typical of ictal periods, indicating the absence of synaptic connections. The study herein presented aimed at investigating the effect of reducing the [Mg[Formula: see text]] during the induction of Nonsynaptic Epileptiform Activities (NSEA). As an experimental protocol, NSEA were induced in rat hippocampal dentate gyrus (DG), using a bath solution containing high-K[Formula: see text] and zero-added-Ca[Formula: see text]. Additionally, computer simulations were performed using a mathematical model that represents electrochemical characteristics of the tissue of the DG granular layer. The experimental results show that the reduction of [Mg[Formula: see text]] causes an increase in the duration of the ictal period and a reduction in the interictal period, intensifying epileptiform discharges. The computer simulations suggest that the reduction of the Mg[Formula: see text] level intensifies the epileptiform discharges by a joint effect of reducing the surface charge screening and reducing the activity of the Na/K pump.

Concurrent brain structural and functional alterations in patients with migraine without aura: an fMRI study

ObjectivesTo explore the possible concurrent brain functional and structural alterations in patients with migraine without aura (MwoA) patients compared to healthy subjects (HS).MethodsSeventy-two MwoA patients and forty-six HS were recruited. 3D-T1 and resting state fMRI data were collected during the interictal period for MwoA and HS. Voxel-based morphometry (VBM) for structure analysis and regional homogeneity (Reho) for fMRI analysis were applied. The VBM and Reho maps were overlapped to determine a possible brain region with concurrent functional and structural alteration in MwoA patients. Further analysis of resting state functional connectivity (FC) alteration was applied with this brain region as the seed.ResultsCompared with HS, MwoA patients showed decreased volume in the bilateral superior and inferior colliculus, periaqueductal gray matter (PAG), locus ceruleus, median raphe nuclei (MRN) and dorsal pons medulla junction. MwoA patients showed decreased Reho values in the middle occipital gyrus and inferior occipital gyrus, and increased Reho values in the MRN. Only a region in the MRN showed both structural and functional alteration in MwoA patients. Pearson correlation analysis showed that there was no association between volume or Reho values of the MRN and headache frequency, headache intensity, disease duration, self-rating anxiety scale or self-rating depression scale in MwoA patients. Resting state functional connectivity (FC) with the MRN as the seed showed that MwoA patients had increased FC between the MRN and PAG.ConclusionsMRN are involved in the pathophysiology of migraine during the interictal period. This study may help to better understand the migraine symptoms.Trial registrationNCT01152632. Registered 27 June 2010.

Effect of migraine attack on pupil size, accommodation and ocular aberrations.

To evaluate the pupil size, accommodation, and ocular higher-order aberrations (HOAs) in patients with migraine during migraine attacks and compare them with interictal period and healthy controls. This prospective, case-control study included 48 eyes of 24 patients with migraine and 48 eyes of 24 age and sex-matched healthy controls. Measurements were performed using a Hartmann Shack aberrometer. Accommodative responses to accommodative stimulus ranging from 0 to 5 diopters (D) in increments of 0.5 D were recorded. Spherical, coma, trefoil aberration, and root mean square (RMS) of total HOAs were assessed. Patients with migraine were measured twice during the interictal phase and during migraine attack. The mean pupil size significantly decreased during migraine attack (5.85 ± 0.19 mm) compared with the interictal phase (6.05 ± 0.19 mm) in the patients with migraine (p = 0.012). There was a significant increase in the accommodative response to accommodative stimulus of 1.5 to 5 D during migraine attack. No significant change was observed in HOAs during migraine attack. In addition, no ictal or interictal period measurements were statistically significantly different from the controls. Comparing symptomatic and non-symptomatic sides in 17 migraine patients with unilateral headache, no significant difference was found in any of the measurements in both ictal and interictal periods. Our results suggest the presence of a subtle oculosympathetic hypofunction in patients with migraine during the ictal period compared to the interictal period. The accommodation status of the eye seems to be affected by this autonomic dysfunction.

Multiparametric EEG analysis of brain network dynamics during neonatal seizures

BackgroundOne of the most challenging issues in paediatric neurology is the diagnosis of neonatal seizures, whose delayed treatment may affect the neurodevelopment of the newborn. Formulation of the correct diagnosis is conditioned by the high number of perceptually or automatically detected false positives. New MethodNew methodologies are proposed to assess neonatal seizures trend over time. Our approach is based on the analysis of standardized trends of two properties of the brain network: the Synchronizabilty (S) and the degree of phase synchronicity given by the Circular Omega Complexity (COC). Qualitative and quantitative methods based on network dynamics allow differentiating seizure events from interictal periods and seizure-free patients. ResultsThe methods were tested on a public dataset of labelled neonatal seizures. COC shows significant differences among seizure and non-seizure events (p-value <0.001, Cohen’s d 0.86). Combining S and COC in standardized temporal instants provided a reliable description of the physiological behaviour of the brain’s network during neonatal seizures. Comparison with Existing Method(s)Few of the existing network methods propose an operative way for carrying their analytical approach into the diagnostic process of neonatal seizures. Our methods offer a simple representation of brain network dynamics easily implementable and understandable also by less experienced staff. ConclusionsOur findings confirm the usefulness of the evaluation of brain network dynamics over time for a better understanding and interpretation of the complex mechanisms behind neonatal seizures. The proposed methods could also reliably support existing seizure detectors as a post-processing step in doubtful cases.

Current Conceptual Understanding of the Epileptogenic Network From Stereoelectroencephalography-Based Connectivity Inferences.

Localization of the epileptogenic zone (EZ) is crucial in the surgical treatment of focal epilepsy. Recently, EEG studies have revealed that the EZ exhibits abnormal connectivity, which has led investigators to now consider connectivity as a biomarker to localize the EZ. Further, abnormal connectivity of the EZ may provide an explanation for the impact of focal epilepsy on more widespread brain networks involved in typical cognition and development. Stereo-electroencephalography (sEEG) is a well-established method for localizing the EZ that has recently been applied to examine altered brain connectivity in epilepsy. In this manuscript, we review recent computational methods for identifying the EZ using sEEG connectivity. Findings from previous sEEG studies indicate that during interictal periods, the EZ is prone to seizure generation but concurrently receives inward connectivity preventing seizures. At seizure onset, this control is lost, allowing seizure activity to spread from the EZ. Regulatory areas within the EZ may be important for subsequently ending the seizure. After the seizure, the EZ appears to regain its influence on the network, which may be how it is able to regenerate epileptiform activity. However, more research is needed on the dynamic connectivity of the EZ in order to build a biomarker for EZ localization. Such a biomarker would allow for patients undergoing sEEG to have electrode implantation, localization of the EZ, and resection in a fraction of the time currently needed, preventing patients from having to endure long hospital stays and induced seizures.

Effect of the COVID-19 pandemic on drug compliance and stigmatization in patients with epilepsy

ObjectivePandemics like coronavirus disease 2019 (COVID-19) bring along many individual and social problems. We aimed to investigate what changes the COVID-19 pandemic can cause in patients with epilepsy on drug compliance and stigmatization. Material and methodModified Morisky Scale (MMS) and stigmatization scales were used between October and November 2019 to assess drug compliance and stigmatization in epilepsy patients. These scales were renewed in June and July 2020 in the same patient group to assess the impact of the epidemic on drug compliance and stigmatization in patients with epilepsy. Statistical analysis was performed using the statistical software SPSS 17.0 for Windows (SPSS, Inc). Demographic and clinical characteristics of the patients were recorded in SPSS. The interviews were conducted during the interictal period. Paired-samples t-test was used to compare the stigma scale results of epilepsy patients before and during COVID-19. The Wilcoxon test was used to compare MMS groups before and during COVID-19. ResultsA total of 110 patients were included in the study. There was no significant difference between the pre-pandemic and pandemic period in epilepsy stigma scale used to evaluate stigmatization levels in patients. During the pandemic period, it was observed that patients had higher motivation and higher knowledge than before the pandemic (p = 0.048). There were seven patients (6.4%) whose seizure frequency increased during the pandemic period. There were two patients (1.8%) who had difficulty in accessing drugs during the pandemic period. In multivariate analysis, only parameter that predicted an increase in seizure frequency was the number of drugs used In the of COVID-19 period. In correlation analysis, a negative correlation was found between the stigma total score during COVID-19 period and education level. ConclusionA slight increase in the frequency of seizures was observed in our patients during the pandemic period, and no significant problem was experienced in accessing drugs. The COVID-19 pandemic made patients more motivated and informed in drug compliance in the patient group and had no effect on stigmatization.

Simultaneous Electroencephalographic and Electocorticographic Recordings of Lateralized Periodic Discharges in Temporal Lobe Epilepsy.

Lateralized periodic discharges (LPDs), which constitute an abnormal electroencephalographic (EEG) pattern, are most often observed in critically ill patients with acute pathological conditions, and are less frequently observed in chronic conditions such as focal epilepsies, including temporal lobe epilepsy (TLE). Here we aim to explore the pathophysiological mechanism of LPD in TLE. We retrospectively selected 3 patients with drug-resistant TLE who simultaneously underwent EEG and electrocorticography (ECoG) and demonstrated LPDs. We analyzed the correlation between the EEG and ECoG findings. In patients 1 and 2, LPDs were recorded in the temporal region of the scalp during the interictal periods, when repeated spikes followed by slow waves (spike-and-wave complexes; SWs) and periodic discharges (PDs) with amplitudes of >600 to 800 µV appeared in the lateral temporal lobe over a cortical area of >10 cm2. In patient 3, when the ictal discharges persisted and were confined to the medial temporal lobe, repeated SWs were provoked on the lateral temporal lobe. When repeated SWs with amplitudes of >800 µV appeared in an area of the lateral temporal lobe of >10 cm2, the corresponding EEG discharges appeared on the temporal scalp. LPDs in patients with TLE originate from repeated SWs and PDs of the lateral temporal lobe, which might represent a highly irritable state of the lateral temporal cortex during both interictal and ictal periods.

S100B and neuron-specific enolase levels in episodic and chronic migraine.

In recent years, radiological and biochemical data have emerged regarding the development of cellular damage in the brain of patients with migraine, calling into question what has traditionally been accepted as a benign disorder. In order to investigate whether cellular damage develops in the brain of episodic migraine patient, serum levels of neuron-specific enolase (NSE) and S100B have been evaluated in recent studies. However, contradictory results were obtained in these studies. Moreover, there is no study on NSE and S100B in cases of chronic migraine. Patients with episodic migraine with or without aura and chronic migraine were included. In addition, 27 healthy volunteers were included as a control group. Control group was selected from healthy volunteers of the same age and sex. We investigated serum NSE and S100B levels during the interictal period in 26 patients with episodic migraine and 27 patients with chronic migraine. The serum NSE and S100B levels were significantly higher in both patients with episodic and chronic migraine than controls. Although there were no significant differences in the serum NSE and S100B levels between the two patients' groups, these markers were found to be higher in cases of chronic migraine. These results suggest that there is both neuronal and glial involvement in the two migraine groups. Elevations in these markers in cases of episodic migraine suggest that cellular damage not only results from headache episodes, but that there may be also an ongoing pathological process during the interictal period.

Role of High Frequency Oscillations of Somatosensory Evoked Potentials in Deciphering Pathophysiology of Migraine.

Background Habituation deficit is considered as a neurophysiological abnormality among migraineurs in the interictal period. For clear comprehension and clarity about the mechanism underlying habituation in migraine, a sophisticated method, i.e., high frequency oscillations (HFOs) evoked potentials, have been utilized. However, studies pertaining to this in the Indian context are rare. Objective The aim of the study is to determine the utility of HFO of somatosensory evoked potential (SSEP) in deciphering the pathophysiology of migraine. Materials and Methods Sixty subjects including 30 migraineurs in the interictal period and 30 healthy controls were considered for the study. Median nerve SSEP was recorded in patients and controls by standard protocols. HFO was extracted offline using the Digital zero-phase shift band-pass filtering at 450 and 750 Hz. The early and late HFOs were determined with respect to the N20 peak and were compared between the groups. Results Of total 30 migraineurs, 18 had hemicranial headache and 12 had holocranial headache. N20 latency, P25 latency, N20 onset to peak amplitude, and N20 onset to P25 amplitude were comparable in migraineurs and controls. The intraburst frequency of early HFOs in migraineurs was significantly higher ( p = 0.04), whereas the peak-to-peak amplitude was significantly lower ( p = 0.001). Conclusion Early HFOs on SSEP represent the thalamocortical excitatory drive in migraineurs. Overall, the study reports that reduced amplitude of early HFOs in the interictal period suggest reduced thalamocortical drive in migraineurs.

Analysis of Interictal EEG Signal Correlations for Diagnostics of Epilepsy

Principles are described for diagnosing epilepsy on the basis of the Memory Function Formalism. Auto- and cross-correlations of electroencephalograms from healthy subjects and patients with epilepsy recorded during the interictal period are studied. Characteristic types of the memory function power spectra and substantial changes in statistical memory effects in pathology are found. Disorders are revealed in the dynamic interconnection in areas of the cerebral cortex in epilepsy.

Melanopsin hypersensitivity dominates interictal photophobia in migraine.

To define the melanopsin and cone luminance retinogeniculate pathway contributions to photophobia in healthy controls and migraineurs. Healthy controls and migraineurs were categorized according to the International Classification of Headache Disorders criteria. Photophobia was measured under full-field illumination using electromyography in response to narrowband lights spanning the melanopsin and cone luminance action spectra. Migraineurs were tested during their interictal headache-free period. Melanopsin-mediated post-illumination pupil responses quantified intrinsically photosensitive Retinal Ganglion Cell (ipRGC) function. A model combining the melanopsin and cone luminance action spectra best described photophobia thresholds in controls and migraineurs; melanopsin contributions were ∼1.5× greater than cone luminance. In the illumination range causing photophobia, migraineurs had lower photophobia thresholds (∼0.55 log units; p < 0.001) and higher post-illumination pupil response amplitudes (p = 0.03) than controls. Photophobia is driven by melanopsin and cone luminance inputs to the cortex via the retino-thalamocortical pathway. In migraineurs, lower photophobia thresholds reflect hypersensitivity of ipRGC and cone luminance pathways, with the larger and prolonged post-illumination pupil response amplitude indicative of a supranormal melanopsin response. Our findings inform artificial lighting strategies incorporating luminaires with low melanopsin excitation and photopic luminance to limit the lighting conditions leading to photophobia.

Gray and White Matter Changes in Migraineurs: a Review of Literature

Several neuroimaging studies with advanced techniques have shown changes in gray and white matter in the brain of migraineurs. This narrative review highlights the structural and functional alterations and causality factors of migraine for the introduction of new treatment modalities. PubMed, Google Scholar, and Scopus were searched without any language restriction for the articles depicting gray and white matter changes in migraineurs. Using magnetic resonance imaging scans, multiple studies have demonstrated a reduction in white matter volume and presence of white matter hyperintensities and demyelinated white matter areas, especially in the frontal and parietal lobes. Similarly, voxel-based morphometry analysis has shown a greater reduction in gray matter in the frontal and cingulate cortex of chronic and episodic migraineurs. An overactivation of the frontal and cingulate cortex has been observed during the interictal period. These parts of gray matter are involved in cognitive, emotional, and autonomic aspects of nociception. Moreover, constituents of the limbic system, particularly the thalamus, hippocampus, amygdala, and cingulate gyrus, have also depicted predominant functional disturbances during migraine episodes. Recent studies highlighted a decrease in gray matter volume in the spinal trigeminal nucleus. These findings suggest that such changes might be the reason for dysfunction and pain regulation. Modern neuroimaging thus clearly helps in understanding the pathophysiology of migraine, which calls for novel therapeutic interventions in unresponsive or chronic migraineurs.

Coherence between the hippocampus and anterior thalamic nucleus as a tool to improve the effect of neurostimulation in temporal lobe epilepsy: An experimental study

BackgroundAlthough the mechanisms by which deep brain stimulation (DBS) modifies the activity of the ictal network are mostly undefined, recent studies have suggested that DBS of the anterior nucleus of the thalamus (ANT) can be an effective treatment for mesial temporal lobe epilepsy (MTLE) when resective surgery cannot be performed. In a nonhuman primate (NHP) model of MTL seizures, we showed that the ANT was actively involved during interictal and ictal periods through different patterns and that the hippocampus (HPC) and ANT synchronously oscillate in the high beta-band during seizures. ObjectiveBased on those findings, we evaluated whether the frequency of stimulation is an important parameter that interferes with seizures and how to adapt stimulation protocols to it. MethodsWe investigated the effects of low-frequency (40 Hz - determined as the ictal frequency of correlation between structures) and high-frequency (130 Hz - as commonly used in clinic) ANT stimulation in three monkeys in which MTLE seizures were initiated. ResultsLow-frequency stimulation had a strong effect on the number of seizures and the total time spent in seizure, whereas high-frequency stimulation had no effect. The coherence of oscillations between the HPC and the ANT was significantly correlated with the success of low-frequency stimulation: the greater the coherence was, the greater the antiepileptic effect of ANT-DBS. ConclusionOur results suggest that low-frequency stimulation is efficient in treating seizures in a nonhuman primate model. More importantly, the study of the coherence between the ANT and HPC during seizures can help to predict the anti-epileptic effects of ANT stimulation. Furthermore, the DBS paradigm could be customized in frequency for each patient on the basis of the coherence spectral pattern.

Response inhibition alterations in migraine: evidence from event-related potentials and evoked oscillations

BackgroundMigraine is characterized by a hypersensitivity to environmental stimulation which climaxes during headache attacks but persists during attack-free period. Despite ongoing debates about the nature of the mechanisms giving rise to this abnormality, the presence of deficient inhibitory cortical processes has been proposed to be one possible mechanism underlying its pathogenesis. Empirical evidence supporting this claim is mainly based on previous accounts showing functional cortical disexcitability in the sensory domain. Considering that a general inhibitory control process can play an important role across early to later stage of information processing, this may indicate the important role other dimensions of inhibitory control can play in migraine disability. The present study examined the pathophysiological features of inhibitory control that takes place during suppression of prepotent responses in migraineurs.MethodsTwenty-two patients with migraine without aura (mean age = 30.86 ± 5.69 years; 19 females) during the interictal period and 25 healthy controls (mean age = 30.24 ± 3.52 years; 18 females) were recruited. We used a stop signal task in combination with event-related potentials (ERPs) to examine participants’ neural activity supporting response inhibition.ResultsBehaviorally, migraineurs exhibited prolonged stop signal reaction times relative to healthy controls. At the neural level, the amplitude of the stop-N2 over fronto-central, central and centro-parietal scalp regions, a component of the ERPs related to conflict monitoring during early, non-motoric stages of inhibition, was significantly increased in migraineurs. Meanwhile, the amplitude of the stop-P3 over central and centro-parietal scalp regions, a component of the ERPs reflecting late-stage inhibition of the motor system and cognitive evaluation of motor inhibition, was also significantly increased in migraineurs. Ultimately, our time-frequency analysis further revealed increased delta activity in migraineurs.ConclusionsConsistent with the theory that alterations in cognitive cortical processes are a key signature of migraine, our findings revealed an abnormal state of suppressing prepotent responses in migraineurs, which can be attributed to cortical disexcitability of the pre-frontal executive network and centro-parietal sensorimotor network. These novel findings extend to show the existence of dysfunctional inhibition control that occurs during suppression of prepotent responses in migraneurs.

Interictal hemodynamic abnormality during motor activation in sporadic hemiplegic migraine: An explorative study

IntroductionThe motor weakness in sporadic hemiplegic migraine (SHM) is a poorly understood aura manifestation. Cortical spreading depression affecting motor excitability and alterations of neurovascular coupling may be integral to the development of migraine aura. MethodsWe studied 10 right-handed SHM patients and 17 healthy controls with functional near-infrared spectroscopy (fNIRS) in the interictal period. Subjects performed a finger opposition task and had real time determination of oxyhemoglobin (OxyHb) and deoxyhemoglobin (deOxyHb) changes. Recordings were completed with 10 left and 10 right sided cortical channels. ResultsMean baseline to peak changes were significantly reduced in SHM patients as compared to controls bilaterally only for OxyHb measurements in the anteromedial channels. Mean time to peak changes were significant delayed in SHM patients compared to controls bilaterally largely for OxyHb measurements in the posterolateral channels, with the exception of 2 recording channels. ConclusionsOur findings suggest presence of abnormal interictal hemodynamic responses to increased metabolic demands during motor activation in SHM. These bilateral cerebrovascular changes involve OxyHb to a much larger degree than deOxyHb. Baseline to peak changes were evident more in the anteromedial channels, whereas time to peak changes were more evident in the posterolateral channels. These findings suggest that oxygen inflow into specific brain regions may be defective in SHM as opposed to oxygen utilization. Our findings suggest that in SHM, enduring hemodynamic deficits in response to an impending motor task are evident, which can be further explored in future studies, and possibly therapeutic trials.