Assessing the microlesion effect of subthalamic deep brain stimulation surgery with FDG PET.

Object: The authors investigated whether the insertion of deep brain stimulation electrodes into the subthalamic nucleus can alter regional brain metabolism in the absence of stimulation.

Methods: Six patients with Parkinson disease (PD) underwent preoperative FDG PET scanning, and again after STN electrode implantation with stimulation turned off.

Results: Compared with baseline values, glucose utilization was reduced in the postoperative off-stimulation scans in the putamen/globus pallidus and in the ventral thalamus (p < 0.01), and there was increased metabolism in the sensorimotor cortex and cerebellum (p < 0.005). The expression of a specific PD-related spatial covariance pattern measured in the FDG PET data did not change after electrode implantation (p = 0.36), nor was there a significant change in clinical motor ratings (p = 0.44). Differences in PD-related spatial covariance pattern expression among the patients after electrode implantation did, however, correlate with the number of microelectrode recording trajectories placed during surgery (r = -0.82, p < 0.05).

Conclusions: These findings suggest that electrode implantation can impart a microlesion effect on regional brain function. Nonetheless, these local changes did not cross the threshold of network modulation needed to achieve clinical benefit.