The medial subthalamic nucleus (STN) border may be a more appropriate anatomical reference than the midcommissural point for determining the optimal location for deep brain stimulation (DBS) in patients with Parkinson disease, according to study findings published in the Journal of Neurology, Neurosurgery, and Psychiatry.
Participants with Parkinson disease from a multicenter randomized controlled trial who underwent STN DBS were selected for this study. Investigators collected postoperative computed tomography and unilateral Unified Parkinson’s Disease Rating Scale motor examination scores at 12 months after surgery. Among 33 patients with Parkinson disease undergoing intervention, 65 electrodes were used. Motor improvements at 12 months were subdivided into nonresponding (n=17), responding (n=30), and optimally responding (n=18) body sides. To determine potential DBS hotspots, investigators used stereotactic coordinates of optimal electrode contacts in relation to the midcommissural point and the medial STN border.
Investigators discovered a significant negative correlation (Pearson’s correlation, −0.52; P <.01) between individual Unified Parkinson’s Disease Rating Scale motor improvement and Euclidean distance from the stimulation center to the DBS “hotspot” when using the medial STN border as an anatomical reference.
According to the investigators, the hotspot was found at 1.7 mm anterior, 2.8 mm lateral, and 2.5 mm superior to the medial STN border. When researchers excluded the optimally responding body sides from the assessment, a similar negative correlation existed (Pearson’s correlation, −0.49; P <.01). No correlation was found when using the midcommissural point as a reference.
The investigators were unable to evaluate the location of stimulation relative to axial motor symptom improvement, as the study was focused on assessing right- and left-sided motor scores separately. In addition, the researchers note that the determination of the precise interrelationship of dorsolateral STN and contact localization was suboptimal because of limitations in magnetic resonance imaging image quality.
When identified, this new reference point appears to be “well feasible at 1.5 T [magnetic resonance imaging,] and therefore readily applicable for all DBS teams.”
Bot M, Schuurman PR, Odekerken VJJ, et al. Deep brain stimulation for Parkinson’s disease: defining the optimal location within the subthalamic nucleus [published online January 20, 2018]. J Neurol Neurosurg Psychiatry. doi: 10.1136/jnnp-2017-316907