Role of magnetoencephalography in predicting the epileptogenic zone and post-operative seizure outcome - A retrospective study.

PURPOSE: Study assessed the role of MSI in predicting the post-operative seizure outcome. METHODS: This retrospective study included patients who underwent MEG and epilepsy surgery and had a minimum 6 months of postoperative follow-up. Concordance of MEG cluster with post-surgical resection cavity was classified as follows Class I) Concordant and region-specific, Class II) Concordant and region non-specific, Class III) Concordant lateralization only and Class IV) Discordant lateralization. The relationship between MSI concordance and post-operative seizure outcome was assessed. RESULTS: A total of 183 patients (M: F = 109:74) were included. The mean age at onset of seizures: 8.0 ± 6.4 years. The dipoles were frequent in 123(67.2 %). The primary cluster orientation was regular in 59 (32.2 %) and mixed in 124 (67.8 %) patients. Concordance between MEG and resection cavity: Class I - 124 (67.8 %), class II- 30 (16.4 %), class III- 23 (12.6 %), and class IV- 6 (3.3 %). The post-surgically mean duration of follow-up was 19.52 ± 11.27 months. At 6-month follow-up period, 144 (78.7 %) patients had complete seizure freedom out of which 106 (73.6 %) had class I concordance. Concordance of MEG with resection cavity was associated with a good outcome at 6 months (p = 0.001), 1 year (p = 0.001), 2 years (p = 0.0005) and 5 years (p = 0.04). MEG cluster characteristics had no association with seizure outcome except the strength of the cluster and outcome at 3 years (p = 0.02) follow-up. CONCLUSION: The study supports that the complete resection of the MEG cluster had high chance of seizure-freedom and can be used as a complementary noninvasive presurgical evaluation tool.

Network alterations in eating epilepsy during resting state and during eating using Magnetoencephalography.

OBJECTIVE: Eating epilepsy presents various imaging and electrophysiological features along with various seizure triggers. As such, network changes in eating epilepsy have not been comprehensively explored. This study was conducted to illustrate resting state network changes in eating epilepsy and to study the changes in network configurations during eating. METHODS: Magnetoencephalography recordings of nineteen patients with drug-resistant eating epilepsy were compared with healthy controls during resting state. A subgroup of nine patients and 12 controls had MEG recordings during eating. Network changes were analyzed using phase lag index across 5 frequency bands [delta, theta, alpha, beta, and gamma] using clustering coefficient (CC), betweenness centrality (BC), path length (PL), modularity (Q), and small worldness (SW). RESULTS: During the resting state, PL was decreased in patients with epilepsy in the delta, theta, and gamma band. Q was lower in patients with epilepsy in the beta and gamma bands. During eating, in patients with epilepsy, PL and SW were increased in all frequency bands, and Q was decreased in the beta band and increased in the rest of the frequency bands. Patients with mixed types of seizures showed higher PL in all bands except alpha, higher Q in all bands, and higher SW in the alpha and beta bands. Node-wise changes in CC and BC implicated changes in DMN and 'eating' networks. CONCLUSION: Reflex Eating epilepsy presents with a hyperconnected network that exacerbates during eating. The cause of seizure onset and loss of consciousness in eating epilepsy might be due to aberrant network interaction between the regions of the brain involved with eating, such as the sensorimotor cortex, lateral parietal cortex, and insula with the limbic cortex and default mode network across multiple frequency bands.

EEG-based P300 in mesial temporal lobe epilepsy and its correlation with cognitive functions: A case-control study.

OBJECTIVE: P300 is an event-related potential, being explored as an objective tool to assess cognition. This study aimed to investigate the characteristics of auditory and visual P300 in patients with TLE having unilateral HS using electroencephalography (EEG) and to study its correlation with cognition. METHODS: This is a cross-sectional case-control study, where P300 characteristics in thirty patients with unilateral hippocampal sclerosis with refractory epilepsy were compared with fifteen age-, gender-, and years of education-matched healthy controls (M: F-10:5, mean age-28 ±â€¯4.76 years). Among patients, 15 belonged to the right HS group (M: F-9:6, age at onset-12.92 ±â€¯10.22 years, duration of epilepsy-16.67 ±â€¯9.38 years) and 15 to the left HS group (M: F-8:7, age at onset-10.62 ±â€¯7.18 years, duration of epilepsy-15.53 ±â€¯10.14 years). All subjects underwent EEG-based auditory and visual oddball tasks and cognitive assessment. The P300 latencies (in milliseconds) as well as amplitudes (in microvolts) were predicted in EEG and were correlated with cognitive scores. Source localization of P300 was performed with the CLARA algorithm. RESULTS: The auditory P300 latencies in controls, right HS, and left HS were 323.93 ±â€¯40.28, 351.06 ±â€¯47.23, and 328.80 ±â€¯36.03, respectively (p = 0.18) and its amplitudes were 2.3040 ±â€¯1.46, 2.77 ±â€¯1.19, and 2.68 ±â€¯1.78, respectively (p = 0.48). Visual P300 latencies in controls, right HS, and left HS were 365.87 ±â€¯47.37, 359.67 ±â€¯64.45, and 376.00 ±â€¯60.06, respectively (p = 0.51) and its amplitudes were 3.93 ±â€¯2.28, 2.09 ±â€¯1.45, and 3.56 ±â€¯1.74, respectively (p = 0.014). Further, when compared to the control group the cognitive scores were lower in the patient group (p < 0.05). SIGNIFICANCE: In comparison to the controls, patients with right HS recorded lesser amplitude on visual P300 and lower scores on cognitive tests. P300 and cognitive parameters exhibited varied relationship. P300 could be a complementary objective tool to assess cognition in patients with TLE.

Magnetic source imaging in presurgical evaluation of paediatric focal drug-resistant epilepsy and its predictive value of surgical outcome in lesional cases: A single-centre experience from South India.

OBJECTIVE: This study aims to evaluate the utility of magnetoencephalography in presurgical planning and in predicting post-surgical seizure outcome. METHODS: This study included a cohort of 231 children (1-18 years) with focal drug-resistant epilepsy who underwent MEG as a part of their presurgical workup. Characteristics of MEG observations were described in all children. The concordance and agreement of Magnetic Source Imaging (MSI) of interictal discharges (IED) was estimated with either of the 3 subgroups - MRI lesion; presumed epileptogenic zone (EZ); or resection cavity. In operated children group, MEG dipole characteristics between good and poor outcome groups were assessed. RESULTS: A total of 153 cases (66.2%) showed frequent IEDs (60 spikes/60 min). Of the 173 cases where MSI showed clusters (74.9%), 151 had lesions and 22 were non-lesional. amongst patients with lesional epilepsy and MEG clusters, class I concordance (MEG localization either completely included or overlapped at least 60% with the MRI lesion) was seen in 60.92% with a Cohen's kappa of 0.608. In non-lesional epilepsy, class I concordance of MEG with presumed EZ was found in (81.81%) with an agreement of 0.317. Fifty-three children underwent surgery of whom 39 (73.58%) showed a good outcome (Engel I). In operated children, concordance between MEG focus and resection cavity was observed in 23 (58.97%) with good outcome and in 12 (86.72%) with poor outcome with no significant difference (p>0.05). However, MEG cluster regular organization and clusterectomy are associated with good seizure outcome postoperatively (p< 0.05). Presence of scatters were associated with poor outcome (p<0.05) in children with focal cortical dysplasia. CONCLUSIONS: MEG provides useful information that can serve as a biomarker for prognosticating the surgical outcome in paediatric epilepsy. Cluster removal and regular cluster organization shows predictive power in post-surgical prognostication in children and the presence of scatters predicts poor outcome in children with focal cortical dysplasia.

An investigation on the influence of yogic methods on heart rate variability.

BACKGROUND: The role of underlying mechanisms of yogic strategies which exert beneficiary effects on cardiac autonomic control is poorly understood. We have performed heart rate variability (HRV) analysis on subjects performing yogic methods and control subjects who mimic them through paced breathing and focused attention tasks using external cues. METHODS: Heart rate (HR) time series is generated from electrocardiogram measured from subjects of yogic group (YG); performing yogic practices (n = 15), paced breathing group (PBG); involved in breathing exercises cued at breathing rates (BR) from 3 to 15 cycles per minute (cpm) (n = 23), normal breathing group (NBG) under regular breathing (n = 15), and subjects performing three different cognitive tasks designated as focused attention group (FAG), (n = 24). HRV is analyzed using coherence plots, spectrograms, HRV parameters, and instantaneous frequency recurrence plots (IFRP). RESULTS: HRV is similar among YG and PBG (at BR <12 cpm) and significantly different for YG vs. NBG (p < 0.001) and PBG vs. NBG (p < 0.001). Regularity of breathing oscillations observed in HR is quantified using IFRP and is identical among FAG, PBG, and YG and significantly different for YG vs. NBG (p < 0.01), PBG vs. NBG (p < 0.01), and FAG vs. NBG (p < 0.05). CONCLUSIONS: Low-frequency breathing (BR <12 cpm) plays a primary role in eliciting physiologically significant changes in HRV. By identifying a similarity in breathing oscillations of HR of FAG, YG, and PBG, the results recognize the coexistence of attention and breathing strategies and postulate their joint role in sustaining autonomic benefits, while effects induced by breathing alone on HRV could be attained even intermittently.

Scalp high frequency oscillations (HFOs) in absence epilepsy: An independent component analysis (ICA) based approach.

BACKGROUND: High frequency oscillations (HFOs) have provided a new insight in understanding ictogenesis and seizure localization. In absence seizures, HFOs were predominantly localized in the medial prefrontal cortex (MPFC) in MEG studies. METHODS: We studied HFOs (80-250 Hz) in scalp EEGs in patients with absence epilepsy, and evaluated their frequency bandwidth and spatial-temporal distribution. EEG of 9 patients with absence epilepsy (CAE:JAE-8:1; M:F=7:2; age: 8.1 ± 2.1 years; age at onset: 6.6 ± 1.3 years) were evaluated with scalp EEG (sampling rate: 2048 Hz). Finite impulse response filters on the unipolar or longitudinal bipolar montages were band-passed between 80 and 250 Hz using Cartool(®) and EEGLAB(®). Sensitivity and paper speed were modified accordingly to study the HFOs. Thousand four hundred and thirty eight artifact free 'spike-wave' epileptiform discharges were analyzed. Sleep ictal SW discharges, defined as runs of 3 Hz GSWDs lasting ≥ 4s in stages 1 and 2 sleep, were analyzed by independent component analysis and component time-frequency and channel time-frequency maps using cyclical tapering wavelet transform. A total of 926 HFOs were identified of 1438 GSWDS. RESULTS: The HFOs were associated with inter-ictal generalized spike-wave discharges (IiGSWDs-241/454), ictal GSWDs (IcGSWD-634/884), sporadic SWDs (sSWDs-51/100). The percentage of HFOs was higher in IcGSWD when compared to both IiGSWDs and sporadic SWDs together (χ(2)=52.864, d.o.f=1, p<0.0001). The mean frequency of HFOs was 96.4 ± 10.4 Hz. A channel wise analysis showed the maximum HFO band width in the right fronto-central region (F4=28 Hz, C4=24 Hz). CONCLUSION: Narrow bandwidth interictal and ictal HFOs can be identified in scalp EEG of patients with absence epilepsy. Further characterization of the various properties of pHFOs will be helpful in opening up a domain of clinical evaluation and interpretation of the various epileptic disorders. To improve the insights into the onset and spread of absence seizures, and to study the network properties, one could analyze the HFOs in high density EEG arrays with multimodal integration using MEG or fMRI.

Enhancing the reliability in the noninvasive measurement of the his bundle magnetic field using a novel signal averaging methodology.

BACKGROUND: Extraction of the weak electrical activity of the "His Bundle" (HB) by noninvasive methods has not been very successful in the past. The study reassesses the use of signal averaged magnetocardiography (SAMCG), overcoming some of the limitations in earlier studies including in the signal averaging methodology. METHODS: SAMCG on healthy subjects (14 male and 1 female) were performed using R-peak as the fiducial point in all cases and also using QRS-onset as the fiducial point in select cases. RESULTS: A conspicuous feature (H) with a magnitude up to 200 femto Tesla (fT) attributed to the HB activity was observed in the PR segment at several spatial positions on the thorax, with onset at 35-50 ms before the QRS-onset (V) in 15 out of 18 trials constituting 83% of cases studied. The QRS-onset as the fiducial point resolved the feature better compared to the conventionally used R-peak, especially in trials exhibiting spread in heart rate (HR). This is attributed to the fluctuations in Q(on) RD (the time interval between QRS-onset and R-peak) compared to the temporal stability of the H-V duration. conclusions: SAMCG reveals a well-resolved H feature. The double hump morphology of the feature extended at least up to a frequency of 150 Hz. The importance of the choice of QRS-onset as the fiducial point is unequivocally demonstrated, illustrated by measurements on subjects exhibiting considerable heart rate variability. The latter has a general validity and should be applicable to SAECG as well.