Use of intraoperative CT to predict the accuracy of microelectrode recording during deep brain stimulation surgery. A proof of concept study

Objectives Intraoperative computed tomography (iCT) is currently used to confirm the target location of the microelectrode (ME) during microelectrode recording (MER) and ultimate location of deep brain stimulation (DBS) leads at our institution. We evaluated whether iCT can be used to predict the trajectory and accuracy of the ME track. Patients and methods Intraoperative imaging profiles of ten consecutive patients who had undergone DBS surgery were retrospectively reviewed. We found that cranial iCT, in addition to visualizing the target, also visualizes the extra-cranial segment of the guide tube (ECGT) used to insert the ME. We propose a hypothetical technique that extrapolates the trajectory of only the ECGT down to target depth using planning software. In order to provide a proof of concept analysis of this hypothetical technique, we retrospectively assessed post MER placement iCT studies and used planning software to visualize only the ECGT. An extrapolated vector was drawn along the long axis of the ECGT down to the same depth (z) as the ME. The obtained x and y coordinates were subsequently recorded and compared to the x and y coordinates of the ME tip to validate this technique. Results The average radial error between ECGT trajectory coordinates and final ME tip coordinates was 0.93 ± 0.1 mm (mean±SEM). Conclusion The use of iCT to predict accuracy of microelectrode location is feasible. In the future, performing iCT before guide tube penetration of dura can allow for trajectory prediction and if needed, correction of the ME, thereby potentially improving accuracy and reducing the number of MER tracks.