Ictal stereo-electroencephalography onset patterns of mesial temporal lobe epilepsy and their clinical implications

The differences in mesial temporal epilepsy (MTE) stereo-electroencephalography (SEEG) seizure-onset patterns and their clinical implications remains unclear. We analyzed consecutive patients with MTE undergoing non-invasive workup, SEEG evaluation and resective surgery. Cases were classified into either mesial temporal sclerosis (MTS) group or non-MTS group based on magnetic resonance imaging (MRI). Seizure-onset patterns of SEEG were classified to analyze their correlation with surgical outcome and clinical subtypes. Twenty-eight patients were studied. Twenty (71.4%) patients had Engel I outcome. Thirteen patients had one seizure-onset pattern, 15 had two or more patterns. Five patterns of seizure-onset were identified and seizure-onset zones differed significantly across the 5 patterns. No difference was observed in surgical outcome between patients with single or multiple seizure-onset patterns. Periodic spike-onset pattern was associated with MTS (P = 0.003) while burst-onset was associated with non-MTS lesions (P = 0.003). Patients with seizure-onsets outside the resected temporal lobe (multiple onsets) had poorer prognosis (P = 0.0046). We identified 5 distinct onset patterns of MTE and correlated two of them with MRI findings. Multiple seizure-onset patterns in MTE may not necessarily suggest poor outcome. Patients with multi-focal seizure-onsets including seizures originating outside the resected temporal lobe have poorer outcome. This study identifies distinct onset patterns of MTE and their clinical implications.