Intraoperative anatomical navigation in asleep deep brain stimulation as a tool for the interpretation of microelectrode recordings: a prospective study

• Introduction: Microelectrode Recording (MER) is still regarded as a fundamental feature of Deep Brain Stimulation (DBS). In awake DBS, MERs are better characterized due to lack of sedation. During asleep DBS, general anesthesia interferes with MERs. Therefore, basing intraoperative lead localization in asleep DBS on extracellular recordings alone, requires huge expertise by the surgeon, who risks sub-optimal final electrode placement. This study aims to investigate whether anatomical navigation during asleep DBS surgery is a reliable and useful additional tool. The intraoperative association of anatomical (imaging studies and 3D reconstructions) and electrophysiological (microelectrode recordings) information would in fact permit a facilitated surgical procedure. • Methods/Materials: Patients enrolled in this study undergo asleep DBS in the Pediatric and Functional Neurosurgery Department of Padova. During surgery, intraoperative MERs are integrated with deterministic anatomical imaging of the structures crossed by the trajectory, obtained using a dedicated software. This allows to visualize exact anatomical relationships of each point along the trajectory of the lead with the 3D reconstructed areas of interest. For Subthalamic Nucleus (STN) DBS these areas include the thalamus, the zona incerta, the STN and the substantia nigra, whereas for Globus Pallidus Internus (GPi) DBS these include the striatum, GPe, GPi, and the optic tract. To investigate whether this feature of anatomical navigation is a reliable and helpful additional factor in the decision-making for the placement of the definitive electrode, we compare the intraoperatively planned electrode placement with the postoperatively reconstructed electrode position. • Results: Preliminary results show that the mean distance between the intraoperatively planned target and the postoperatively reconstructed target is <1 mm and the mean trajectory deviation <1°. There is a significant increase in target deviation between the first performed trajectory and the second one. This is coherent with the hypothesis that there’s an increase of brain shift as the procedure goes on due to intraoperative liquor loss. • Discussion: The study suggests that intraoperative anatomical navigation in DBS, using the dedicated software may be adequate for facilitated precise electrode placement, as there is no relevant difference between the intraoperatively planned electrode placement and the postoperatively reconstructed electrode position. • Conclusion: Preliminary results suggest that the anatomical navigation is a useful and reliable tool to significantly facilitate the interpretation of intraoperative MERs.