Describe the clinical, neurophysiological, and radiological characteristics of patients with mesial temporal lobe epilepsy (TLE) who underwent hippocampus-sparing anterior temporal lobectomy with a particular emphasis on the stereoelectroencephalographic (SEEG) findings that guided the decision to spare the hippocampus.

We included patients who underwent hippocampus-sparing anterior temporal lobectomy and stereoelectroencephalography at Lille University Hospital. We reported their clinical, characteristics as well as the results of their presurgical evaluation, neuroimaging data, and SEEG findings.

We report four patients with mesial TLE (three with dominant hemisphere TLE and one with non-dominant hemisphere TLE). In three patients, SEEG captured several seizures originating from the amygdala, with a consistent delay before hippocampal involvement. In the fourth patient, no spontaneous seizure was recorded during monitoring. However, stimulation of the amygdala successfully reproduced a full habitual seizure. All patients underwent hippocampus-sparing anterior temporal lobectomy and have been seizure-free since surgery (two Engel IA and two Engel IB). Post-surgery neuropsychological evaluations were stable or showed improvement in pre-surgical deficits.

Hippocampus-sparing anterior temporal lobectomy is a safe and effective treatment for patients in whom the hippocampus is not part of the seizure onset zone. SEEG is invaluable when considering hippocampus-sparing resection, as it provides definitive evidence that the hippocampus is not the primary site of seizure onset. Thorough and meticulous SEEG exploration is essential to accurately delineate the seizure onset zone. The decision-making process should integrate SEEG findings with neuroimaging and neuropsychological assessments, relying on a multidisciplinary approach tailored to each patient.