Longitudinal analysis of interictal electroencephalograms in patients with temporal lobe epilepsy with hippocampal sclerosis

Abstract Background While studies have shown the progression of atrophy in temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS), little is known about the long-term dynamics of interictal epileptiform discharges (IEDs). Objectives To investigate long-term IEDs distribution in routine EEGs. Methods We evaluated 314 patients with TLE and MRI signs of HS (TLE-HS). Six had bilateral, 163 had left, and 145 had right HS. We analyzed 3655 routine EEGs (average 11.6 EEGs/patient). The EEGs were classified into four groups: (i) ipsilateral-IEDs (n = 1485), EEGs with only IEDs ipsilateral to the HS; (ii) bilateral-IEDs (n = 390); (iii) contralateral-IEDs (n = 186); and (iv) normal-EEGs (n = 1594). The duration of epilepsy at the time of the EEG (average 27.9 years) was divided into four groups: (a) 30 years (n = 1845). We performed ANOVA with Tukey’s pairwise comparisons and linear regression analysis between the duration of epilepsy and the EEG groups. Results The ANOVA showed a difference in the distribution of IEDs over time (p Conclusions Contrary to our expectations, contralateral-IEDs remained stable over time, whereas normal-EEGs decreased and ipsilateral-IEDs increased. Contralateral-IEDs may reflect early abnormalities and not epilepsy progression.