The atypical subthalamic nucleus--an anatomical variant relevant for stereotactic targeting

BACKGROUND: The improvement of PD motor symptoms by DBS of the STN depends on exact targeting.

METHODS: A combination of MRI and multitrajectory microrecordings was used for localization of the STN in a group of 228 consecutive PD patients.

RESULTS: In 1% of our cases, the STN was consistently shifted in the anterior (3.3 ± 0.8mm) and medial (3.0 ± 0.9 mm) direction within the target plane, compared to controls. Adjustment of the original target coordinates after intraoperative reevaluation of the MRI and confirmation by typical subthalamic neuronal recordings along the deviant trajectory allowed the implantation of clinically effective electrodes in all cases. The relative improvement of the motor UPDRS at 6-months follow-up in patients with an atypical and typical STN was comparable.

CONCLUSION: An atypical position of the STN does not need to complicate DBS surgery, if detected by a combination of MRI-based targeting and electrophysiological guidance.