gms | German Medical Science

Objective: Since 2000 we implanted 550 depth electrodes in 196 patients suffering from pharmacologically intractable seizures for diagnostic purposes. In a retrospective study we analyzed the benefit and the risk of stereotactic implantation of depth electrodes for presurgical invasive monitoring.

Methods: Most of these patients were implanted in the mesiotemporal lobes by a temporo-lateral (59 patients) or posterior-occipital (82) approach or by a combination of both (12) in order to determine the side and precise location of the primary epileptogenic focus. 36 patients received extratemporal electrodes (mean 1.9 per patient), 20 of these patients in combination with the temporal electrodes.

In another group of 16 patients we used up to fifteen (mean 9.36) cortically implanted electrodes in a wide variety of locations in order to register a stereo-EEG. This technique allows recording from infolded cortical structures such as the insula and the cingular gyrus.

Furthermore 13 patients were implanted with a variable number of additional microwire bundles in combination with standard macroelectrodes. These microwire bundles, consisting of 8 individually isolated 40µm wires and a reference wire, were used to record unit activity of single nerve cells as well as local field potential oscillations. Special tools were designed in cooperation with industrial partners in order to optimize this stereotactic procedure. The purpose of this technique is both clinical as well as cognitive state of the art research.

Apart from these diagnostic procedures, four patients with progressive myoclonic epilepsy received a total of 14 deep brain stimulation electrodes in the substantia nigra pars reticulata (SNR), subthalamic nucleus (STN) and ventral intermediate nucleus (VIM) of the thalamus in order to control debilitating myoclonus.

Results: For all implantations, diagnostic and therapeutic, we recognized only two minor adverse events without any impact on the clinical condition of these two patients: one intracerebral bleeding along one of the macroelectrode tracts in a first, and one small sized subdural hematoma in a second patient.

Conclusions: Stereotactic implantation of depth electrodes for invasive epilepsy diagnostics is a safe neurosurgical procedure, providing substantial benefit for both patients and clinical research. It is based on optimized technical tools and careful preoperative planning within a well established and routinely performed frame-based operative program.