Abstracts

Rationale: The study of propagation of epileptic activity is an interesting field in epileptology, not only for the traditional field of resective surgery but also for new therapeutical strategies such as deep brain stimulation. The insight from clinical studies from patients can be methodically limited due to several restrictions, such as repeatability, recording time and site of recoding. In the following results from a modified established non-human primate model is presented, allowing repeated, reversible induction of neurophysiological and clinical seizure manifestation. Methods: For this study three up to five micro electrodes where temporally implanted into the motor cortex of a non-human motor cortex in order to record cortical brain activity after electrical stimulation. To analyze the relationship of epileptic spike characteristics and stimulation parameters in a first run of this experiment the electrical stimulation amperage varied between 10 and 500 µA for a stimulation time of 2 or 4 seconds with a fixed frequency at 60 Hertz. The following results are based on five trails recorded at different days with 201 stimulations in total. Epileptic spikes were manually detected and grouped. To characterize the spikes we grouped the stimulations by amperage and calculated the means and standard deviations for the amount of recognized spikes, their amplitude, the duration of spiking activity after stimulation and the frequency of these spikes. Additionally, we used Morlet wavelets to determine the frequency components of the mean (4 second long) spike waveforms. A co-registered video recorded clinical manifestations. Results: The amount of spikes, spike frequency and duration of spiking activity after stimulation are independent of the choice of stimulation amperage. At 120 and 160 µA, there was an incremental spike amplitude increase. Motor seizures (partly with a Jacksonian'march) were seen at 90 to 500 µA. Additionally we were able to identify two different types of spike patterns which are clearly distinguishable by their waveform, there occurrence and even by their inherent frequency components. No change in behavior was observed inbetween experiments. Conclusions: These preliminary results showed that cortical induced electrical stimulation results into a stable manifestation both neurophysiologically (cortical, epileptiform EEG-activity) and clinically (motor seizures). Only the amperage seems to be the key influencing parameter in this model, which proofed to be reversible and not-harmful. Further studies are warranted for a precise model characterisation.