Abstracts

Rationale: Deep brain stimulation using thalamic targets for seizure control is currently under investigation. The centro-medium nuclei were initially targeted and followed by the antero-ventral thalamic nuclei . We have targeted the centro-medium nucleus in patients with generalized epilepsy. We report on non-seizure related findings in these patients. Methods: Four patients with refractory generalized epilepsy who were submitted to bilateral alternated thalamic centro-medium stimulation using Kinetra electrodes were studied. Patients were submitted to electrode implantation under general anesthesia targeting the centro-medium nucleus 10 mm off the midline at the posterior commissural plane. Final parameters were 2V, 300usec and 130 Hz. Intra-operative EEG recordings were obtained and generalized recruiting responses prevailing over the frontal lobes were noted in all patients during low-frequency (6-8 Hz) stimulation. Results: We noted a progressive decline of generalized seizure frequency when stimulation intensity reached at least 1.4V (130 Hz, 300 usec). On the other hand, a clear increase in attention level could be seen in all patients when stimulation reached lower intensity (0.4-0.6V). This attention level increment persisted at higher stimulation parameters. There was no somnolence after bilateral alternated centro-medium stimulation. Although we were not able the quantitatively document this increase in attention, patients had a clear decrease in verbal response latency, higher verbal output, performed daily tasks more easily and had extended concentration capability (more time following TV programs, more focus on rehabilitation exercises, prolonged and more organized dialogues etc). Conclusions: It is not clear so far if this increased attention resulted from the centro-medium nucleus stimulation itself or is related to an initial decrease in interictal spiking. It preceded the decrease in seizure frequency in every patient. A quantitative analysis of attention level is mandatory in the future, although this might represent a challenge in a population with varying degrees of mental retardation.