Authors :
Presenting Author: Jonathan Ho, BS – University of Pittsburgh
Thandar Aung, MD – University of Pittsburgh; Donald Crammond, PhD – University of Pittsburgh; Arianna Damiani, MS – University of Pittsburgh; Jorge Gonzalez-Martinez, MD PhD – University of Pittsburgh; Arka Mallela, MD – University of Pittsburgh
Rationale:
Neurostimulations, such as vagal nerve stimulator (VNS), deep brain stimulator (DBS) and responsive neurostimulator (RNS), have been widely used. Over the last decade, the focus of stimulation has been on the subcortical structures,
mainly the thalamus. Among all, stimulation of the anterior nucleus of the thalamus has been FDA approved for epilepsy treatment and medial pulvinar stimulation has shown promise to reduce severe seizures while improving neuropsychological testing. In addition, there are ongoing trials for generalized epilepsy with the centromedian nucleus being the target of stimulation. However, there is no evidence-based guideline as to where the target of electrode for neurostimulator should be placed within the thalamus and strategies can vary greatly between surgeons. Here, we aim to establish finding the perfect target for implanting neurostimulator’s electrode based upon the micro-recording of the cell density in the subthalamic target in relation to the effect on the scalp EEG intraoperatively. Methods:
We recruited two patients undergoing RNS implantation of the centromedian nucleus of the thalamus. While advancing an AlphaOmega micro-electrode recorder through the centromedian nucleus, we measured neuronal firing rates to characterize cell density. Afterwards, we applied stimulation at 147Hz for 40 seconds while recording through scalp electroencephalogram (EEG) at various depths in the centromedian nucleus. We created a spectrogram of the scalp EEG recordings pre-stimulation, during stimulation and post-stimulation at the different depths and then calculated the power at different frequency bands.
Results:
In the two patients, we observe that cortical activity mostly between 0-5Hz. When we compared cortical activity in the scalp EEGs while stimulating at depths with different cell densities, we observed that stimulation in areas with sparse cell density created a significantly higher power in the 0-5Hz band both during and after stimulation when compared to stimulation in areas with higher cell density (Fig. 1). We observed this increase in 0-5Hz band during stimulation of low cell density across 14 out of 15 scalp EEGs.
Conclusions:
These results demonstrate that stimulation of areas with lower cell density, such as white matter tracts, are correlated with increased cortical activity in the 0-5Hz range. This suggests a change in the paradigm of selecting thalamic targets of interest, potentially selecting areas of lower cell density or white matter tracts, to maximize influence modifying cortical activity, especially in the case for epilepsy treatment.
Funding: Hamot Foundation and Departmental Funds