Minimal Electrophysiology and Imaging Enhanced Deep Brain Stimulation

In deep brain stimulation (DBS), accurate implantation of the stimulation electrode into the surgical target is crucial for a successful clinical outcome. The classic technique for surgical planning uses stereotactic atlases developed from a limited number of post-mortem samples. To better account for individual variability, imaging- and electrophysiology-based techniques have been developed. Electrophysiological techniques may offer intraoperative insight into anatomical positioning. Macrostimulation and microelectrode recording are gold-standards for simulating the therapeutic effects of stimulation during surgery, as well as predicting the threshold of stimulation-induced side effects. However, these techniques result in increased procedural time, reduced accuracy due to brain shift, and increased procedural risk due to the up to five electrode penetrations through brain tissue for testing. Motor evoked potentials (MEPs) deliver stimulation across the test and final implanted electrode to predict distance to the motor tract, and have been previously shown by our group to be an effective predictor of therapeutic threshold and side effects.

High-resolution magnetic resonance imaging (MRI) may be used to directly visualize target structures for individual patients, such as the subthalamic nucleus (STN), internal globus pallidus (GPi), and ventral intermediate nucleus of the thalamus (VIM). However, differentiating between the target and surrounding tissue is challenging for some surgical targets, and pre-surgical MRI may give imprecise coordinates of brain structures due to brain shift during surgery. Advances in machine learning have led to the development of software for assisting with detecting surgical targets from MRI images and for merging intraoperative images with the preoperative MRI images to represent the stereotactic space and verify the electrode position within the operating room setting.

Currently, our center uses MEPs, microelectrode recordings, and macrostimulation with software and intraoperative imaging plan and conduct DBS surgeries. Macrostimulation and microelectrode recordings may be redundant with the introduction of intraoperative MEP testing. This study aims to assess the safety, accuracy and clinical outcomes of using the streamlined procedure of MEP testing with imaging and assistive software only. This technique will be referred to as the MiXT technique.