In vivo Exploration of the Connectivity between the Subthalamic Nucleus and the Globus Pallidus in the Human Brain Using Multi-Fiber Tractography

The basal ganglia is part of a complex system of neuronal circuits that play a key role in the integration and execution of motor, cognitive and emotional function in the human brain. Deep Brain Stimulation (DBS) of the subthalamic nucleus and the globus pallidus pars interna provides an efficient treatment to reduce symptoms and levodopa-induced side effects in Parkinson’s Disease patients. While the underlying mechanism of action of DBS is still unknown, the potential modulation of white matter tracts connecting the surgical targets has become an active area of research. With the introduction of advanced diffusion MRI acquisition sequences and sophisticated post-processing techniques, the architecture of the human brain white matter can be explored in-vivo. The goal of this study is to investigate the white matter connectivity between the subthalamic nucleus and the globus pallidus. Two multi-fiber tractography methods were used to reconstruct pallido-subthalamic, subthalamo-pallidal and pyramidal fibers in five healthy subjects datasets of the Human Connectome Project. The anatomical accuracy of the identified tracts was evaluated by two expert neuroanatomists. Both multi-fiber approaches enabled the detection of complex fiber architecture in the basal ganglia. The evaluation by the neuroanatomists showed that the identified tracts were in agreement with the expected anatomy. False-negative tracts demonstrated the current limitations of the methods for clinical decision-making. Multi-fiber tractography methods combined with state-of-the art diffusion MRI data have the potential to help identify white matter tracts connecting DBS targets in functional neurosurgery intervention.