Syndrome of mesial temporal lobe epilepsy associated with hippocampal sclerosis: clinical and electrophysiological characteristics

INTRODUCTION. Mesial temporal lobe epilepsy associated with hippocampal sclerosis (MTLE-HS) is a major cause of drug-resistant temporal lobe epilepsy; the relationship between hippocampal morphology and clinical-EEG features/network configuration remains insufficiently characterized. We aimed to compare clinical presentation and scalp EEG in MTLE-HS with and without structural hippocampal changes.

MATERIALS AND METHODS. Ninety-five adults (18–45 years) with MTLE-HS were included (eligibility per ILAE2017; seizure classification per ILAE-2024). All underwent long-term video-EEG; scalp EEG was graded using a six-category scale. Cohorts: MRI-positive structural hippocampal change (n=66) and MRI-negative variants (n=29). We compared seizure phenotypes and scalp EEG patterns and analysed correlations of EEG “severity” with age, age at onset, and disease duration.

RESULTS. Three seizure phenotypes were identified; two-type combinations predominated (58 %), whereas all three cooccurred only with structural hippocampal compromise (c2=7.166; p<0.05). Scalp EEG distributions differed between subgroups (c2=11.610; p<0.05); structural cases more often exhibited complex network configurations, including independent bitemporal foci. In the structural subgroup, EEG “severity” inversely correlated with current age and age at onset, but not with disease duration; overall, EEG abnormality magnitude was independent of illness duration.

CONCLUSION. Hippocampal integrity shapes clinical-EEG phenomenology in MTLE-HS and, when structurally compromised, is associated with a more complex epileptic network (including independent bitemporal foci). The independence of EEG severity from disease duration supports integrated use of clinical, neuroimaging, and neurophysiological data for presurgical planning.

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