The outcome literature of subthalamic nuclei (STN) deep brain stimulation (DBS) suggests that cognitive declines are commonly reported following surgery. We hypothesized that differences in electrode position and surgical trajectory may lead to a differential neuropsychological outcome.

We conducted a standardized evaluation of the location of the DBS electrode tip and the active electrodes, the surgical trajectory through which they were placed, and their relation to neuropsychological change scores (mental status, verbal memory, verbal fluency, and psychological measures) in 17 bilateral STN DBS patients using 6 month post-surgical magnetic resonance imaging data.

Declines in mental status scores were related to electrodes that were more posterior-laterally placed within the frontal quadrant in either hemisphere or those located superiorally in the left hemisphere. Electrodes that were closer to the approximated STN and more superiorally located in the left hemisphere were associated with verbal learning declines at 6-months following surgery. In the right hemisphere, the electrodes that were located more in the lateral direction were related to verbal short-term memory declines; while for verbal long-term memory declines were found for electrodes located more posterior-laterally in the left hemisphere. Declines in verbal fluency scores were more variable with associations found between change scores and electrodes in the lateral and superior directions in the left hemisphere and those electrodes closer to the approximated STN and more superiorally and posteriorally located in the right hemisphere. In contrast, semantic fluency declines were only related to right hemisphere electrodes located more superiorally. Declines in mood were related to those electrodes located further away from the approximated STN, particularly those located more inferiorally and laterally in the left hemisphere. Anxiety change scores were not associated withy the location of the electrodes.

The results provide preliminary evidence that 6-months following bilateral STN DBS cognitive and emotional changes may be related to the surgical trajectory and electrode placement.