Quantitative EEG biomarkers of cognitive performance in drug-resistant temporal lobe epilepsy

Abstract

Background: This study aimed to explore quantitative electroencephalography (qEEG) biomarkers of cognitive performance in drug-resistant temporal lobe epilepsy (TLE) and analyze their relationship with clinical characteristics. Methods: Cross-sectional study including adult patients with drug-resistant TLE and a control group. Resting-state, eyes-closed qEEG samples were analyzed using the fast Fourier transform approach. Power spectral density was calculated for four frequency bands: delta (1–3.9 Hz), theta (4–7.9 Hz), alpha (8–12.9 Hz), and beta (13–18 Hz). Neuropsychological tests were administered to TLE patients. Results: Twenty-nine TLE patients (mean age 42 ± 8.2 years; 44.8 % women) and 23 age- and sex-matched controls were enrolled. Clinically significant cognitive impairment was found in 86.2 % of patients (58.6 % amnestic). Compared to controls, TLE patients showed increased ipsilateral power spectral density for the theta (p = 0.045), alpha (p = 0.023) and beta bands in the anterior region (p = 0.029) and for the delta band in the posterior region (p = 0.03). Alpha/theta ratio (ATR) was lower in the posterior quadrant of the epileptogenic hemisphere (p = 0.013), and higher seizure frequency correlated with a lower ATR in the ipsilateral temporal region (r: −0.425; p = 0.021). Patients with amnestic cognitive impairment exhibited higher power spectral density across most frequency bands (p < 0.005). Impaired verbal memory and executive function were associated with increased power density. Conclusion: Increased power spectral density was evident in all frequency bands in the epileptogenic hemisphere, particularly in those patients with amnestic cognitive impairment. Moreover, higher seizure frequency correlated with a lower ATR in the temporal region. Power spectral analysis can provide useful information in drug-resistant TLE patients.