Localisation of eloquent cortex using magnetoencephalography and its clinical implications.

OBJECTIVES: This study aimed to localise the eloquent cortex and measure evoked field (EF) parameters using magnetoencephalography in patients with epilepsy and tumours near the eloquent cortex. METHODS: A total of 41 patients (26 with drug-refractory epilepsy and 15 with tumours), with a mean age of 33 years, were recruited. Visual evoked field (VEF), auditory evoked field (AEF), sensory evoked field (SSEF), and motor-evoked field (MEF) latencies, amplitudes, and localisation were compared with those of a control population. Subgroup analyses were performed based on lobar involvement. Evoked Field parameters on the affected side were compared with those on the opposite side. The effect of distance from the lesion on nearby and distant evoked fields was evaluated. RESULTS: AEF and VEF amplitudes and latencies were reduced bilaterally (p < 0.05). Amplitude in the ipsilateral SSEF was reduced by 29.27% and 2.16% in the AEF group compared to the contralateral side (p = 0.02). In patients with temporal lobe lesions, the SSEF amplitude was reduced bilaterally (p < 0.02), and latency was prolonged compared with controls. The MEF amplitude was reduced and latency was prolonged in patients with frontal lobe lesions (p = 0.01). EF displacement was 32%, 57%, 21%, and 16% for AEF, MEF, VEF, and SSEF respectively. Patients in the epilepsy group had distant EF abnormalities. CONCLUSIONS: EF amplitude was reduced and latency was prolonged in the involved hemisphere. Distant EF amplitudes were more affected than latencies in epilepsy. Amplitude and distance from the lesion had negative correlation for all EF. EF changes indicated eloquent cortical displacement which may not be apparent on MRI.

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.

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.

EEG Observations in Probable Sporadic CJD.

INTRODUCTION: Sporadic Creutzfeldt Jakob Disease, the most common reported prion disease, is a fatal neurodegenerative disease caused by the misfolding of protein PrPC to PrPSC. EEG is the first in vivo test to support the clinical diagnosis of sporadic CJD (sCJD). This study is carried out to describe the comprehensive electroencephalography changes in a cohort of patients with probable sCJD from south India. METHODOLOGY: This retrospective observational study is conducted by reviewing case records from 2013-2020. Demographic, clinical, imaging details were noted. Electroencephalogram (EEG) recordings were retrieved and reviewed independently by two qualified epileptologists and the findings were visually analyzed and correlated with clinical and imaging abnormalities. RESULTS: Fifty patients with probable sCJD with the availability of artefact-free EEG were included in the study. The mean age was 59.76 ± 8.17 years and M: F was 31:19. Magnetic resonance imaging (MRI) brain showed abnormality defining CJD in 48/50, i.e., 96%patients. EEG showed specific and or nonspecific abnormalities in 88%. The specific abnormalities, i.e., periodic sharp wave complexes (PSWC), were noted 66%. PSWC were mostly asymmetric (90%) and more frequently seen in the right hemisphere (57.6%). Amplitude maximum in the occipital region was noted in 42.4% and in frontal region in 36.4%. The sensitivity of EEG specific abnormalities to diagnose probable sCJD according to CDC 2018 criteria with positive MRI findings was 68.75%. CONCLUSION: This study showed that EEG is a relatively inexpensive and sensitive tool and assists in the diagnosis of sCJD. However, it can be normal or show nonspecific abnormalities in the early stages of the disease.