Can We Rely on Susceptibility-Weighted Imaging for Subthalamic Nucleus Identification in Deep Brain Stimulation Surgery?

BACKGROUND: Susceptibility-weighted imaging (SWI) offers significantly improved visibility of the subthalamic nucleus (STN) compared with traditional T2-weighted imaging. However, it is unknown whether the representation of the nucleus on SWI corresponds to the neurophysiological location of the STN. OBJECTIVE: To determine the correlation between the intraoperative electrophysiological activity of the STN and the representation of the nucleus on different magnetic resonance imaging (MRI) sequences used for deep brain stimulation target planning. METHODS: At stereotactic target depth, microelectrode recordings (MERs) of typical STN neuronal activity were mapped on 3 different preoperative MRI sequences: 1.5-T SWI, 1.5-T T2-weighted, and 3-T T2-weighted MRI. For each MRI sequence, it was determined whether the MER signal was situated inside or outside the contour of the STN. RESULTS: A total of 196 MER tracks in 34 patients were evaluated. In 165 tracks (84%), typical electrophysiological STN activity was measured. MER activity was situated more consistently inside hypointense STN contour representation on 1.5- and 3-T T2-weighted images compared with SWI (99% and 100% vs 79%, respectively). The 21% incongruence of electrophysiological STN activity outside the STN contour on SWI was seen almost exclusively in the anterior and lateral microelectrode channels. CONCLUSION: STN representation on SWI does not correspond to electrophysiological STN borders. SWI does not correctly display the lateral part of the STN. When aiming to target the superolateral sensorimotor part of the STN during deep brain stimulation surgery, SWI does not offer an advantage but a disadvantage compared with conventional T2. Future research is needed to determine whether these findings may also apply for high-field SWI.