Individualized parcellation of the subthalamic nucleus in patients with Parkinson's disease with 7T MRI

Abstract

Deep brain stimulation of the subthalamic nucleus (STN) is a widely performed surgical treatment for patients with Parkinson's disease. The goal of the surgery is to place an electrode centered in the motor region of the STN while lowering the effects of electrical stimulation on the non-motor regions. However, distinguishing the motor region from the neighboring associative and limbic areas in individual patients using imaging modalities was until recently difficult to obtain in vivo. Here, using ultra-high field MR imaging, we have performed a dissection of the subdivisions of the STN of individual Parkinson's disease patients. We have acquired 7T diffusion-weighted images of seventeen patients with Parkinson's disease scheduled for deep brain stimulation surgery. Using a structural connectivity-based parcellation protocol, the STN's connections to the motor, limbic, and associative cortical areas were used to map the individual subdivisions of the nucleus. A reproducible patient-specific parcellation of the STN into a posterolateral motor and gradually overlapping central associative area was found in all STNs, taking up on average 55.3% and 55.6% of the total nucleus volume. The limbic area was found in the anteromedial part of the nucleus. Our results suggest that 7T MR imaging may facilitate individualized and highly specific planning of deep brain stimulation surgery of the STN.

Keywords: Deep brain stimulation; Parcellation; Parkinson's disease; Patient-specific; Subthalamic nucleus; Ultra-high field MRI.

Fig. 1

The STN is parcellated based on its connections to the limbic, associative, motor, and remaining cortical areas. A–B) Division of the cortex into limbic (red), associative (green), motor (blue) and remaining (yellow) cortical areas. C–D) Visualization of the hypointense STNs in the axial (C) and coronal (D) planes. E–H) Example of the parcellation of the STNs of one subject in axial (E,G) and coronal (F,H) views.

Fig. 2

Connectivity mapping of the thalamus. A) Manual segmentation of the cortex into prefrontal and temporal (purple), motor (orange), somatosensory (blue), and parieto-occipital (yellow) cortical areas as defined by Behrens et al. (2003). B) A patient specific thalamic subdivision in one of our subjects. C) Thalamic subdivision as demonstrated by Adopted from Behrens et al. (2003).

Fig. 3

Examples of the subdivisions of the left (A,C,E) and right (B,D,F) subthalamic nuclei of three subjects into a limbic (red), associative (green), and motor (blue) zone. Intermediate colors show overlap between the motor and associative zones (light blue) and between the associative and limbic zones (brown).

Fig. 4

Relative volumes of each functional zone compared to the total STN volume within the left and right STN (left and right bar) of each subject.

Fig. 5

Comparison of the intra-subject (light bars) standard deviations (σ) and inter-subject (dark bars) standard deviations of the volumes of the subthalamic nucleus (STN) and the relative volumes of the zones.

Fig. 6

The percentage of connectivity to the motor (blue), associative (green), limbic (red) and remaining (yellow) cortical areas in three axial slices through the left and right STN ordered from inferior to superior in three subjects (A, B, and C).

Fig. 7

Examples of the electrode position in five STNs. The active contacts (red) lie within the computed motor areas.