gms | German Medical Science

Objective: Therapeutic effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN) in Parkinson’s disease (PD) in parts be may attributed to the stimulation of white matter near the targeted structure. The dentatorubrothalamic (DRT) tract, supposed to improve tremor control in patients with essential tremor, could be one candidate structure.

To investigate the effect of stimulation proximity to the DRT on tremor control in patients with tremor-dominant (TD)-PD treated with STN-DBS.

Methods: Twelve consecutive patients (age 64±11 years) with TD-PD treated with DBS were included. Stereotactic implantation of DBS-electrodes into the motor-area of the STN was performed using direct MRI-based targeting and intraoperative microelectrode recording. Tremor severity was assessed preoperatively and at regular intervals post-operatively (Unified Parkinson’s Disease Rating Scale III). The DRT was visualized in 24 hemispheres after probabilistic fiber tracking (3T-MRI). The position of active electrode contacts was defined on intraoperative stereotactic X-rays and postoperative CT-images after co-registration with 3D-treatment planning MRI/CT-images. We determined the shortest distance of the contacts to the ipsilateral DRT tracts on perpendicular view slices and correlated this value with tremor change percentage.

Results: Three patients had unilateral tremor and accordingly, 3 hemispheres were excluded from further imaging analysis. The remaining 21 hemispheres were associated with contralateral resting tremor. The mean distance between active electrode contacts and the DRT was shorter when the resting tremor improved (N=16 hemispheres, 1.42±0.86 mm) compared to five non-responding hemispheres (2.28±1.51 mm) (p=0.283).

Conclusion: This retrospective analysis suggests that in STN-DBS better tremor control correlates with the distance of active electrode contacts to the DRT. Tractography techniques may optimize DBS targeting individually.