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Background: Magnetoencephalography (MEG) plays a preponderant role in the preoperative assessment of patients with drug‐resistant epilepsy (DRE). However, the magnetoencephalography of patients with drug‐resistant epilepsy can be difficult without sedation and/or general anesthesia. Our objective is to describe our experience with intravenous dexmedetomidine as sedation for magnetoencephalography and its effect, if any, on the ability to recognize epileptic spikes. Methods: In this retrospective study, we reviewed the records of 89 children who presented for Magnetoencephalography/electroencephalography (EEG) scans between August of 2008 and May of 2015. Data analyzed included demographics and the frequency of epileptic spikes. Sedated magnetoencephalography recordings were compared to nonsedated video‐electroencephalography (vEEG) recordings in the same patients to determine the impact of dexmedetomidine. Results: Spike frequency between magnetoencephalography with sedation and video‐electroencephalography without sedation was compared in 85 patients. Magnetoencephalography and video‐electroencephalography were considered clinically concordant in 80 patients (94.1%) and discordant in 5 patients (5.9%), all with less spikes during Magnetoencephalography. The median (range) bolus dose of dexmedetomidine was 2 (1‐2) mcg/kg. The median (range) infusion rate of dexmedetomidine was 2 (0.5‐4) mcg/kg/h. All patients experienced reductions in heart rate after administration of dexmedetomidine; these reductions were statistically, but not clinically, significant. Conclusions: Our results suggest that dexmedetomidine‐based protocol provides reliable sedation in children undergoing MEG scanning because of the high success rate, limited interictal artifacts, and minimal impacts on spike frequency. [ABSTRACT FROM AUTHOR]

Acute migraine could be associated with neurophysiological and cognitive changes. This study evaluates the neurophysiological changes in auditory information processing in adolescents with acute migraine by means of magnetoencephalography. The multifeature sound mismatch negativity (MMN) paradigm was used to study nine adolescents with an acute migraine and nine age- and gender-matched healthy controls. Latencies and amplitudes of M100, M150, M200, and MMN m responses were evaluated. Migraine subjects had smaller M150 amplitudes than healthy subjects. The latencies of MMN m response for the frequency change were delayed in both hemispheres in migraine subjects, as compared with healthy controls. Our results indicate that the function of neural substrates, responsible for different stages of auditory information processing, is impaired during the acute migraine. The identification of underlying cortical dysfunction during an acute migraine can lead to future identification of neurophysiological biomarkers for studying acute migraine and response to treatment. [ABSTRACT FROM AUTHOR]

The discontinuous patterns in neonatal magnetoencephalographic (MEG) data are quantified with a novel Hilbert phase (HP) based approach. The expert neurologists' scores were used as the gold standard. The performance of this approach was analyzed using a receiver operating characteristic (ROC) curve, and it was compared with two other approaches, namely spectral ratio (SR) and discrete wavelet transform (DWT) that have been proposed for the detection of discontinuous patterns in neonatal EEG. The area under the ROC curve (AUC) was used as a performance measure. AUCs obtained for SR, HP, and DWT were 0.87, 0.80, and 0.56, respectively. Although the performance of HP was lower than SR, it carries information about the frequency content of the signal that helps to distinguish brain patterns from artifacts such as cardiac residuals. Based on this property, the HP approach was extended to fetal MEG data. Further, using the frequency property of the HP approach, burst duration and interburst interval were computed for the discontinuous patterns detected and they are in agreement with reported values. [ABSTRACT FROM AUTHOR]

Objective The abnormality of intrinsic brain activity in autism spectrum disorders (ASDs) is still inconclusive. Contradictory results have been found pointing towards hyper-activity or hypo-activity in various brain regions. The present research aims to investigate the spatial and spectral signatures of aberrant brain activity in an unprecedented frequency range of 1–2884 Hz at source levels in ASD using newly developed methods. Materials and methods Seven ASD subjects and age- and gender-matched controls were studied using a high-sampling rate magnetoencephalography (MEG) system. Brain activity in delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz), low gamma (30–55 Hz), high gamma (65–90 Hz), ripples (90–200 Hz), high-frequency oscillations (HFOs, 200–1000 Hz), and very high-frequency oscillations (VHFOs, 1000–2884 Hz) was volumetrically localized and measured using wavelet and beamforming. Results In comparison to controls, ASD subjects had significantly higher odds of alpha activity (8–12 Hz) in the sensorimotor cortex (mu rhythm), and generally high-frequency activity (90–2884 Hz) in the frontal cortex. The source power of HFOs (200–1000 Hz) in the frontal cortex in ASD was significantly elevated as compared with controls. Conclusion The results suggest that ASD has significantly altered intrinsic brain activity in both low- and high-frequency ranges. Increased intrinsic high-frequency activity in the frontal cortex may play a key role in ASD. [ABSTRACT FROM AUTHOR]

Summary: Purpose: We aimed to determine the changes in neural correlates of auditory information processing such as auditory detection, encoding, and sensory discrimination in pediatric patients with intractable epilepsy. Methods: In this magnetoencephalography (MEG) study, 10 patients and 10 age- and gender-matched healthy controls were investigated with the multi-feature mismatch negativity (MMN) paradigm. Latencies and amplitudes of M100, M150, M200, and MMN event-related fields were evaluated. Results: All event-related fields in response to standard stimuli (M100, M150 and M200) and responses to occasional five deviant sounds, deviating from the standard stimuli either in duration, frequency, intensity, location, or by including a silent gap were reduced in amplitude in epilepsy patients compared with healthy controls. Conclusions: Our study suggests that auditory information processing is impaired in patients with drug-resistant epilepsy, being evident both in stimulus feature encoding (as reflected by changes of early event-related components, e.g., M100) and in cortical sound discrimination (as reflected by MMNm). The neural changes involving diminished M100 as well as MMNms for all five deviant sound types suggest wide-spread auditory information processing impairments in these patients. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, there has been a growing interest on the role of gamma band (>30Hz) neural oscillations in motor control, although the function of this activity in motor control is unknown clearly. With the goal of discussing the high frequency sources non-invasively and precisely during unilateral index finger movement, we investigated gamma band oscillations in 20 right-handed normal adults with magnetoencephalography (MEG). The results showed that gamma band activity appeared only during finger movement. Nineteen subjects displayed consistently contralateral event-related synchronization (C-ERS) within high gamma band (70–150Hz) in primary motor cortex (M1) of both hemispheres. Interestingly, 15 subjects displayed ipsilateral event-related desynchronization (I-ERD) and C-ERS within broad gamma band (30–150Hz). The locations of the broad gamma band I-ERD and C-ERS revealed hemispherical symmetry in M1. These findings demonstrate that there are consistent high gamma C-ERS and inconsistent low gamma I-ERD during a simple finger movement in the motor cortex. This study provides new evidence for the use of high gamma frequency oscillations as biomarkers in the analyses of functional brain activity and the localization of the motor cortex. [ABSTRACT FROM AUTHOR]