gms | German Medical Science

Strip electrodes are implanted via burr holes either alone or together with grid and/or depth electrodes. The indication for the placement of subdural strip electrodes is the same as for depth electrodes. Their usefulness, especially in temporal lobe epilepsy, is still controversial. The aim of this study was to elucidate the role of subdural strip electrodes in an invasive epilepsy surgery protocol. Depending on the electrocorticographically (ECoG) obtained results the further investigations and treatment were planned according to our invasive protocol.

Thirty-nine patients with pharmacoresistant and disabling epilepsy were included. Subdural strip electrodes were implanted in all patients by using a burr hole either to identify lateralisation or to delineate the lobe affected by the epileptogenic focus. Depending on the electrocorticographically (EcoG) obtained results the further investigations and treatment were planned according to our invasive protocol.

In 22 of the 39 patients (56%) the subdural electrodes allowed identification of an epileptogenic focus and resection. 6 patients (15%) underwent grid implantation for further invasive mapping. In 15 patients (39%) conservative treatment was continued; two patients (5%) underwent vagus nerve stimulation. Of the 22 patients who underwent operations, 82% were completely seizure free (Engel Ia). No transient or permanent complications were observed in this series.

Subdural strip electrodes provide a safe, reliable, and minimal invasive method for long-term invasive ictal monitoring in the presurgical evaluation of patients being considered for epilepsy surgery. They also provide sufficient information to lateralise an epileptogenic focus when recording from the amygdala or hippocampus. Thus, we were able to proceed with a successful focal resection in most of the cases.