Stimulation of the Presupplementary Motor Area Cluster of the Subthalamic Nucleus Predicts More Consistent Clinical Outcomes

BACKGROUND:The development of diffusion tensor imaging and tractography has raisedincreasing interest in the functional targeting of deep brain stimulation of the subthalamicnucleus (STN) in Parkinson disease.OBJECTIVE:To study, using deterministic tractography, the functional subdivisions of theSTN and hyperdirect white matter connections located between the STN and the medialfrontal cortex, especially the presupplementary motor area (preSMA), SMA, primary motorarea (M1), and dorsolateral premotor cortex, and to study retrospectively whether thisinformation correlates with clinical outcome.METHODS:Twenty-two patients with Parkinson disease who underwent STN deep brainstimulation were analyzed. Using 3 T MR images, the medial frontal cortex was manuallysegmented into preSMA, SMA, M1, and dorsolateral premotor cortex, which were then usedto determine the functional subdivisions of the lateral border of the STN. The intersectionalquantities of the volume of activated tissue (VAT) and the hyperdirect white matter con-nections were calculated. The results were combined with clinical data including unilateral12-month postoperative motor outcome and levodopa equivalent daily dose.RESULTS:Stimulated clusters of the STN were connected mostly to the cortical SMA andpreSMA regions. Patients with primarily preSMA cluster stimulation (presmaVAT%=50%)had good responses to the treatment with unilateral motor improvement over 40% andlevodopa equivalent daily dose reduction over 60%. Larger VAT was not found to correlatewith better patient outcomes.CONCLUSION:Our study is thefirst to suggest that stimulating, predominantly, the STNcluster where preSMA hyperdirect pathways are located, could be predictive of moreconsistent treatment results.

Automated summary

This study utilized deterministic tractography to investigate the functional subdivisions of the subthalamic nucleus (STN) and the white matter connections with the medial frontal cortex in Parkinson's disease. The results suggest that stimulating the cluster located in the preSMA region of the STN may predict better treatment outcomes, including motor improvement and reduced levodopa equivalent daily dose.