Scherg M, Schulz R, Berg P, Cho JH, Bornfleth H, Kural MA, Woermann FG, Bien CG, Beniczky S. Relative Source Power: A novel method for localizing epileptiform EEG discharges.
Clin Neurophysiol 2021;
133:9-19. [PMID:
34788717 DOI:
10.1016/j.clinph.2021.10.005]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 10/13/2021] [Accepted: 10/21/2021] [Indexed: 11/15/2022]
Abstract
OBJECTIVE
To validate relative source power (RSP) imaging of extratemporal interictal epileptiform discharges (IEDs).
METHODS
The accuracy of RSP was validated in a cohort of patients with extratemporal focal epilepsy and a confined epileptogenic lesion (<19 cm3) using distance to the lesion, concordance with resected area and postoperative outcome. Performance was compared with three conventional methods: voltage maps, equivalent current dipole and a distributed source model.
RESULTS
Thirty-three of 41 consecutive patients (80%) had IED averages suitable for analysis. While the peak negativity in voltage maps localized above the epileptogenic lesion only in 18 cases, RSP-maps matched in 29 cases (88%, p < 0.0026). Source localization showed a median distance of 9.8 mm from the lesion. Source-regions with 20 mm radius included 98% of all source-to-lesion distances. In the 21 surgical cases, outcome showed a sensitivity of 82.35% and specificity of 50% without significant differences between the three source imaging methods.
CONCLUSIONS
RSP-maps provide a rapid, intuitive and more accurate source estimation than voltage maps. At sublobar level, RSP localizes with an accuracy similar to conventional methods and results of previous studies.
SIGNIFICANCE
The definition of a source region with 20 mm radius helps in guiding further exploration in extratemporal focal epilepsy.
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