Abstracts

The use of high frequency electrical stimulation (HFS) of brain structures has become an interesting tool in the therapy of several neurological disorders and is clinically established most notably as a treatment for Parkinson[apos]s disease (PD). In epilepsy, HFS is of potential interest as an adjunctive treatment option for pharmacoresistant epilepsy. However, a detailed knowledge about the correct parameters and location for stimulation is missing. Pharmacological inhibition of the subthalamo-nigral network has been shown to be anticonvulsant in experimental epilepsy. HFS of the subthalamic nucleus (STN) is believed to have a dual effect on the target structure. While the net effect is thought to be inhibitory, recent data indicate that stimulation might evoke a new activity pattern, thereby overcoming a pathological rhythm. In our study, we investigated the effects of bilateral HFS (biphasic, bipolar, 130 Hz, 60 [micro]s stimulus width, individual currents) of the STN on the seizure threshold in the amygdala kindling model of epilepsy. We compared the effects of continuous versus intermittent (30 sec every 5 min or 5 sec every 5 min) STN-HFS, as well as different times of HFS preceding the amygdala-stimulation (2 and 5 sec, 1 and 24 hrs). Preliminary data did not reveal robust anticonvulsant effects. However, we observed that continuous STN-HFS and preceding times of 2 sec or 24 hrs seem to be potentially effective in increasing seizure thresholds in kindled rats. We conclude that anticonvulsant effects of bilateral HFS of the STN are highly dependent on the stimulation parameters used. Further studies are needed to decide, which stimulation parameters need to be chosen or whether STN-HFS in epilepsy is not as promising as in PD. (Supported by a grant from the International Neurobionic Foundation, Hannover.)