A Quantitative EEG Signal Analysis Approach for the Evaluation of Neurophysiological Changes Associated with Mesial Temporal Lobe Epilepsy

Mesial Temporal lobe epilepsy (MTLE) is one the most common form of focal epilepsy in adults. Electroencephalography (EEG) is the gold standard for diagnosis and treatment of these patients where accurate seizure-onset lateralization and localization is based on a visually-interpretation. Instead, quantitative EEG (qEEG) analysis provide objective, automated measures of brain activity, allowing for a more comprehensive interpretation of EEG findings, with particular interest towards the features that can be difficult to detect during EEG analysis overcoming limitations of visual interpretation. In this work, visually-normal EEG signals from 26 patients with MTLE and 26 healthy controls (HC) were analyzed with the aim of compared spectral parameters between two groups of subjects to identify differences. In Matlab environment, with an ad hoc procedure, we calculated the total power of all EEG frequency bands and determined alpha-theta (ATR) and alpha-delta (ADR) power ratios for the whole brain and for the anterior, posterior, and temporal regions. We used statistical t-tests to compare the spectral parameters between two groups (p<0.05). Results showed that ATR and ADR ratios were significantly decreased in patients with MTLE compared to HC and on the contrary no differences have been observed for the power values of frequency bands. This study indicates that there is a difference in the power spectrum of qEEG between patients with MTLE and HC. Specifically, the power spectrum of qEEG in patients with MTLE is shifted towards lower frequencies, compared to HC. Moreover, these findings were observed in visually normal recordings, and this suggests that qEEG could be a valuable tool in the diagnosis and evaluation of MTLE even in cases where traditional visual analysis might not reveal any clear signs of epilepsy.