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.

Olfactory Bulb Volume, Olfactory Sulcus Depth in Parkinson's Disease, Atypical Parkinsonism.

Background: About 70-90% of Parkinson's disease (PD) patients have olfactory deficits which is considered as pre-motor symptom of PD. Lewy bodies have been demonstrated in the olfactory bulb (OB) in PD. Objective: To assess the OB volume (OBV), olfactory sulcus depth (OSD) in PD and compare with progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and vascular parkinsonism (VP) patients and determine the cut-off volume of OB that will aid in the diagnosis of PD. Methods: This was a cross-sectional, hospital based, single-center study. Forty PD, 20 PSP, 10 MSA, 10 VP patients and 30 controls were recruited. OBV and OSD was assessed using 3-T magnetic resonance imaging (MRI) brain. Olfaction was tested using Indian Smell Identification test (INSIT). Results: The mean total OBV in PD was 113.3 ± 79.2 mm3 and 187.4 ± 65.0 mm3 in controls (P = 0.003) which was significantly lower in PD. The mean total OSD in PD was 19.4 ± 8.1 and 21.1 ± 2.2 mm in controls (P = 0.41) with no difference. The mean total OBV was significantly lower in PD as compared to that of PSP, MSA and VP patients. There was no difference in the OSD among the groups. The total OBV in PD had no association with age at onset, duration of disease, dopaminergic drugs dosage, motor and non-motor symptoms severity but had positive correlation with cognitive scores. Conclusion: OBV is reduced in PD patients as compared to PSP, MSA, VP patients and controls. OBV estimation by MRI adds to the armamentarium in the diagnosis of PD.

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.