Investigation of morphometric variability of subthalamic nucleus, red nucleus, and substantia nigra in advanced Parkinson's disease patients using automatic segmentation and PCA‐based analysis

Abstract

Subthalamic nucleus (STN) deep brain stimulation (DBS) is an effective surgical therapy to treat Parkinson's disease (PD). Conventional methods employ standard atlas coordinates to target the STN, which, along with the adjacent red nucleus (RN) and substantia nigra (SN), are not well visualized on conventional T1w MRIs. However, the positions and sizes of the nuclei may be more variable than the standard atlas, thus making the pre-surgical plans inaccurate. We investigated the morphometric variability of the STN, RN and SN by using label-fusion segmentation results from 3T high resolution T2w MRIs of 33 advanced PD patients. In addition to comparing the size and position measurements of the cohort to the Talairach atlas, principal component analysis (PCA) was performed to acquire more intuitive and detailed perspectives of the measured variability. Lastly, the potential correlation between the variability shown by PCA results and the clinical scores was explored.

Toward an In Vivo Neuroimaging Template of Human Brainstem Nuclei of the Ascending Arousal, Autonomic, and Motor Systems

“…We further identified [as in previous work, see, for instance, Xiao et al (2014)] midbrain nuclei, as the SN, the RN, and also, in the diencephalon, the STh (Fig. 5), by inspection of hypo-intense areas in T2-weighted images (see also Supplementary Fig.…”

“…‰ homeostasis, sensory-motor functions, sleep and wakefulness cycles, defensive behaviors, and nociception , visualization of Bn in vivo by structural MRI has shown slower progress compared with imaging of other brain areas. Indeed, except for a few midbrain nuclei (e.g., the SN and RN) and the STh (Chowdhury et al, 2013;Keuken et al, 2014;Kwon et al, 2012;Menke et al, 2010;Xiao et al, 2014), the lower relaxivity-based MRI contrast of Bn compared with the cortex (see for instance Fig. 1) has been a barrier to the in vivo structural identification of most Bn and hindered investigation of their functional and structural connections.…”

“…Except for a few midbrain and diencephalic nuclei [e.g., the substantia nigra (SN), the red nucleus (RN), and the subthalamic nucleus (STh) (Chowdhury et al, 2013;Keuken et al, 2014;Kwon et al, 2012;Menke et al, 2010;Xiao et al, 2014)], a major obstacle to precisely localizing individual Bn in vivo is the limited sensitivity and contrast between these small regions and adjacent white matter (WM) using standard neuroimaging methods, such as relaxivity-based magnetic resonance imaging (MRI).…”

“…These nuclei included the median raphe (MnR), the dorsal raphe (DR), the raphe magnus (RMg), and the periaqueductal gray (PAG). To demonstrate the reliability of our approach, we also defined motor relay nuclei already identified in previous work using in vivo relaxivity-based images (Chowdhury et al, 2013;Keuken et al, 2014;Kwon et al, 2012;Menke et al, 2010;Xiao et al, 2014), such as the SN, the RN, and, in the diencephalon, the STh. Notably, to advance the in vivo investigation of these motor Bn in humans, we exploited our multi-contrast method to parcellate each of these nuclei into anatomically distinct subnuclei (e.g., by dividing the SN into two subregions compatible with pars compacta and pars reticulata).…”

Patch-based label fusion segmentation of brainstem structures with dual-contrast MRI for Parkinson’s disease

“…In conventional DBS planning procedures, the location of the STN is determined either by scaling standard brain atlases [17,18] to fit the patient's anatomy as seen in the pre-operative T1w MRI or by inferring the position of the STN relative to landmarks such as anterior and posterior commissure points. However, some studies [19][20][21] have shown that high anatomical variability exists for the STN and consequently simple atlas-fitting cannot sufficiently capture the large variance in the location, size and orientation of the nucleus. More recent indirect methods employ either hierarchical affine [22] or nonlinear registration [23] to deform digitized atlases to improve anatomical alignment, and lend automation to structural identification.…”