A microsubthalamotomy (mSTN) effect has been frequently reported after implantation that improves Parkinson's motor disability. It is usually believed that mSTN effect reflects the post-traumatic tissue reaction within the STN. However, it has never, to our knowledge, been reported whether pre and intraoperative factors could predict this mSTN effect. Preoperative clinical characteristics, that is, age, disease duration, Mattis Dementia Rating Scale score, levodopa responsiveness, severity of motor fluctuations and dyskinesia, and intraoperative parameters, that is, the number of tracks, distance of typical STN neuronal activity recorded along all microelectrodes, and along the definitive electrodes, were assessed in 40 consecutive PD patients submitted for STN stimulation. Multiple stepwise regression analysis showed that only the number of tracks used for microelectrodes recordings was predictor of the contralateral mSTN effect (F (4,73) = 1.83, P = 0.02). This result suggests that the contralateral mSTN depends on the tissue changes along the entirety of surgical trajectories affecting both STN and its adjacent structures.