Stereotactic-EEG-guided radiofrequency multiple hippocampal transection (SEEG-guided-RF-MHT) for the treatment of mesial temporal lobe epilepsy: a minimally invasive method for diagnosis and treatment

For the treatment of mesial temporal lobe epilepsy on the language-dominant side in patients at high risk of memory decline, we propose a minimally invasive diagnostic and treatment technique, adopting the principles of multiple hippocampal transections (MHT) using stereo-electroencephalography-guided radiofrequency (SEEG-guided-RF-MHT). This new technique allows targeting of the longitudinal fibers in the hippocampus critical for seizure spreading, while sparing the transverse circuits which are considered important for memory processing and avoiding discomfort and longer post-operatory recovery time associated with craniotomies. We report the efficacy and safety of this procedure in a preliminary observational study of cases. Five patients at high risk of memory decline, including three with non-lesional hippocampi on MRI, had temporal lobe epilepsy (TLE) necessitating depth electrode implantation. A new strategy of SEEG electrode placement was used to mimic MHT. After confirming hippocampal seizure onset, all the patients had three linear ablations perpendicular to the amigdalohippocampal complex. The procedure was performed at the patient's bedside with the patient awake during the full length of the procedure. Four out of five patients were seizure-free (average follow up: 14-18 months). There were no associated complications. Visual inspection of brain MRI of patients at six months following SEEG-guided RF-MHT showed significant hippocampal volume preservation. Subjects who received the procedure in the dominant side reported no subjective memory complaints in the follow-up clinic assessments at six months. Our preliminary seizure outcome seems very promising since the majority of our patients (four out of five patients) were seizure-free. Since no lesions are made outside the amygdalo-hippocampal complex using this technique and the temporal stem remains intact, more favorable memory and language outcome is expected in patients at high risk of memory decline.