Clinical study on mesial temporal lobe epilepsy monitored by stereotactic implantation of depth electrode into hippocampus

Objective To observe the effects of stereotactic implanting depth electrode into the hippocampus on monitoring mesial temporal lobe epilepsy. Methods Thirteen patients with pharmacoresistant epilepsy were included in the present study. The epileptogenic zone might be located in the hippocampus based on the symptoms and MRI data. Eight-contact depth electrode was implanted into the patients’ hippocampus by stereotactic procedures to record the electroencephalogram(EEG). The duration of monitoring lasted for 24—72 hours or more, so as to be sure if the epileptogenic zone was located in the hippocampus, and to provide evidences for surgical resection of epileptic focus. Results Thirteen patients with mesial temporal lobe epilepsy underwent video electroencephalogram monitoring for 72 hours. Twenty-nine epileptic seizures in 7 patients were detected. Ictal EEG changes manifested as paroxysmal slow wave or spike and slow waves on the background. The epileptiform discharges started from some electrode points, and then propagated to others or the contralateral electrode. After 1—2 seconds of delay, high amplitude slow waves with the frequency of 3—4 Hz were observed on the ipsilateral scalp EEG. Clinical epileptic seizures were not detected in 6 patients during monitoring, depth electrode showed paroxysmal focal high amplitude slow wave or spike and sharp waves, scalp EEG did not find abnormality. Six of thirteen patients received surgical resection of epileptic foci, the outcome during follow-up of 3—8 months was satisfactory. Conclusions To record hippocampal EEG in patients with intractable epilepsy by stereotactic implanting depth electrode into the hippocampus might be a safe and reliable method. It might provide strong evidences for the diagnosis of patients with mesial temporal lobe epilepsy, and for the location of epileptogenic zone. Key words: Epilepsy;  temporal lobe; Hippocampus; Electrodes;  implanted; Stereotaxic techniques; Electroencephalography