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The architecture and hierarchical pathways in the subthalamic nucleus using isotropic imaging

Abstract:

Objective: the subthalamic nucleus (STN) has gained importance as a focus for histological, anatomical and imaging research due to its implications in modulation basal ganglia output and Parkinson's disease. Little is known about the intrinsic organization of the STN. More information is needed to understand its role in the central nervous system (CNS) and allow more accurate planning in Functional Neurosurgery. We describe a method capable of delineating the boundaries of gray matter that could be used to study the internal architecture of the STN. Methods: eighty-seven patients were randomly selected from a magnetic resonance (MR) diffusion tensor imaging (DTI) data bank. From these cases, we selected forty-four in which DTI showed the STN, but not the substantia nigra (SN) in the same image. After initial scrutiny, we excluded fourteen patients with tumors in the brain stem, mass effect, hydrocephalus or obvious malformations. We developed an algorithm by selecting the region of Interest in the STN as identified by the Isotropic Image instead of the Anisotropic one. Results: after reviewing these 30 studies, we identified regions of track concurrency (RTC). In all cases reviewed, RTC showed a hierarchical position from medial to lateral according to the longitudinal axis of the STN and the origin of the fibers. This arrangement revealed a more medial position of the fibers with connection to the parietal, frontal posterior and frontal polar cortex (Brodmann's areas 7, 4 and 11), a central position for the fibers interacting with the corpus callosum and a lateral position of the fibers interacting with the frontal-medial cortex. Conclusion: the technique described allows fiber tracking in the gray matter, undetectable by other imaging methods. It has helped detail the description of STN architecture, evidencing a constant hierarchical position regarding its interconnections. This information helps elucidate the architectural complexity of this nucleus and may prove of use during implantation and programming procedures employed in Deep Brain Stimulation (DBS). ©INNN, 2007.