Patients
The study population consisted of patients with drug-resistant TLE treated between June 2012 and September 2021. The diagnosis of TLE was made by experienced epilepsy specialists according to criteria from the International League Against Epilepsy (ILAE) classification of epilepsies and epileptic syndromes (Commission on Classification and Terminology of the International League Against Epilepsy, 2017). All patients underwent EEG recordings and brain magnetic resonance imaging (MRI). Seizure origin was confirmed using EEG in all patients. Drug-resistant epilepsy was defined as the failure of two tolerated and appropriately chosen anti-seizure drug schedules (whether as monotherapies or in combination) to achieve sustained seizure inhibition (Kwan et al., 2010). The exclusion criteria were as follows: (1) epileptiform discharges over other regions except the temporal lobe on EEG; (2) concomitant seizures originating in non-temporal regions; (3) brain MRI revealing obvious lesions in non-temporal areas, which may influence seizure type or cognition; and (4) complications of other neurological disorders that may influence seizure or cognition, including tumor, trauma, stroke, mental retardation, neurodegenerative disease, and inherited neurological diseases, such as tuberous sclerosis.
Patients who met the following criteria were included in the abnormal cognition (AC) group: (1) complaints of cognitive decline, which interfered with daily routines and work performance; (2) declined calculation ability (< four correct, subtract 7 from 100, continued five times); and (3) impaired memory ability (< 2 points, recall the names of three objects learned earlier). The criteria of normal cognition (NC) group were as follows: (1) no complaints of cognitive dysfunction, qualified for job, and (2) normal calculation and memory abilities. The Wechsler Intelligence Scale (WIS) was used in 30 patients in the AC group and 31 patients in the NC group. All patients underwent video EEG monitoring using a 40-channel video-EEG monitoring system (Nicolet, USA) at the hospital for over 24 h. We also enrolled 18 sex- and age-matched healthy controls (HC). Recording electrodes were placed according to the international 10–20 system, densely in the bilateral temporal regions based on the international 10–10 system, with a sampling frequency of 512 Hz. The 40 electrodes included Fp1, Fp2, F3, Fz, F4, F7, F8, C3, Cz, C4, T7, T8, P3, Pz, P4, P7, P8, O1, Oz, O2, AF7, AF8, F9, F10, FC5, FC6, FT7, FT8, FT9, FT10, C5, C6, T9, T10, CP5, CP6, TP7, TP8, TP9, TP10.
Hippocampal tissue was available from seven patients who underwent surgery. There were four patients in the AC group and three in the NC group. The mini-mental state examination (MMSE) was performed in these patients for cognitive evaluation. Hippocampal sclerosis was observed in all the pathology reports.