Spectrum analysis in targeting the epileptogenic lobe in temporal epilepsy

Aim: Source modeling of MEG has been used to identify epileptogenic zones, because it can target the lobes of spike origination, especially for multi-foci epilepsy. From our tests, thus far, we found the spectrum analysis of MEG recording is also favorable for confirming the temporal lobe that generates seizure.

Methods: The MEG recordings of 19 temporal epilepsy patients identified with source modeling software were reanalyzed with spectrum analysis in bilateral temporal lobes. 11 left temporal epilepsy and 9 right temporal epilepsy patients. The wave from 1 to 90 Hz was segregated into 6 frequency bands, 1–4 Hz (delta band), 4–8 Hz (theta band), 8–13 Hz (alpha band), 13–30 Hz (beta band), 30–48 Hz (low gamma band) and 52–90 Hz (high gamma band). The power amplitude of the 6 frequency bands was evaluated in the bilateral temporal lobes.

Results: When the epileptogenic focus is located in the left temporal, the power amplitude of the temporal lobe with focus is significantly higher in alpha band (P = 0.008) and high gamma band (P = 0.004) relative to the other temporal lobe. When the epileptogenic focus is located in the right temporal, the power amplitude of the temporal lobe with focus is remarkably higher in high gamma band (P = 0.01) relative to the other temporal lobe.

Conclusions: The spectrum analysis is helpful in confirming the epileptogenic zone of temporal epilepsy, besides the identification with source modeling in MEG, especially by the increment in the power amplitude of high gamma band comparing to the other side.