A System for Combined Laser Doppler Flowmetry and Microelectrode Recording during Deep Brain Stimulation Implantation.

Microelectrode recording (MER) and intraoperative test stimulations are commonly used during stereotactic implantation of deep brain stimulation (DBS) electrodes but they can increase the risk of hemorrhage. The aim of the study is to present and evaluate a system combining laser Doppler flowmetry (LDF) and MER. An optical probe was designed with an inner metal tube for the microelectrode. Calibration of the MER-LDF probe in a standard microsphere solution showed expected LDF pattern. No interferences of the MER probe with the LDF signals could be observed. LDF was also acquired in one Parkinson patient undergoing DBS implantation. LDF data were obtained along the precalculated trajectory i.e. from cortex towards the target in the subthalamic nucleus (STN). Results demonstrated the technical feasibility of the combined MER-LDF probe during in-vitro experiences and in one patient. The perfusion signal representing the microcirculation showed stable values with clear peaks from each heartbeat. This agreed with previous investigation using an optical probe without the MER function. Due to the forward-looking probe design, this new technology has a high potential to avoid vessels during MER recording. In addition, it could be possible to detect changes in microcirculatory blood flow during stimulation.