Characterizing Aging in the Human Brainstem Using Quantitative Multimodal MRI Analysis

Abstract

Aging is ubiquitous to the human condition. The MRI correlates of healthy aging have been extensively investigated using a range of modalities, including volumetric MRI, quantitative MRI (qMRI), and diffusion tensor imaging. Despite this, the reported brainstem related changes remain sparse. This is, in part, due to the technical and methodological limitations in quantitatively assessing and statistically analyzing this region. By utilizing a new method of brainstem segmentation, a large cohort of 100 healthy adults were assessed in this study for the effects of aging within the human brainstem in vivo. Using qMRI, tensor-based morphometry (TBM), and voxel-based quantification (VBQ), the volumetric and quantitative changes across healthy adults between 19 and 75 years were characterized. In addition to the increased R2* in substantia nigra corresponding to increasing iron deposition with age, several novel findings were reported in the current study. These include selective volumetric loss of the brachium conjunctivum, with a corresponding decrease in magnetization transfer and increase in proton density (PD), accounting for the previously described “midbrain shrinkage.” Additionally, we found increases in R1 and PD in several pontine and medullary structures. We consider these changes in the context of well-characterized, functional age-related changes, and propose potential biophysical mechanisms. This study provides detailed quantitative analysis of the internal architecture of the brainstem and provides a baseline for further studies of neurodegenerative diseases that are characterized by early, pre-clinical involvement of the brainstem, such as Parkinson’s and Alzheimer’s diseases.

Functional MRI of the Brainstem: Common Problems and their Solutions

“…While white matter forms tracts just like in the cortex (although smaller) the gray matter is mostly organized in nuclei that are embedded in and connected by these tracts. However, there are also structures like the reticular formation, where the distinction of white and gray matter is rather artificial, especially at the MR image resolution available for in vivo studies [30]. Furthermore, the brainstem differs from the cortex in that nuclei with completely unrelated functions can be located in close proximity.…”

A Case Analysis on Different Registration Methods on Multi-modal Brain Images

“…Today, there are a multitude of medical imaging modalities (conventional radiology, CT scans [3], Magnetic Resonance Imaging (MRI) [4], ultrasonography, scintigraphy, single photon emission tomography (SPECT) [5], emission tomography Positons (PET) [6], etc. ), each providing specific and complementary information.…”

Investigating the human brainstem with structural and functional MRI

“…We have assembled articles from a number of scientists who have made important contributions to this evolving field, and continue to shape it. The articles have been divided into a functional (Brooks et al, 2013;Henderson and Macefield, 2013;Ress and Chandrasekaran, 2013;Ritter et al, 2013) and a structural section (Deistung et al, 2013;Ford et al, 2013;Lambert et al, 2013;Yeo et al, 2013;Singleton et al, 2014).The functional section starts with a review by Brooks et al The wealth of methods and applications covered by the authors indicates that functional and structural brainstem-MRI methods have developed to a point where they can be applied to study of a wide range of neuroscientific problems. It is the hope of the editors that the brainstem will soon lose its label of a terra incognita and become a region of major interest in the neuroscience community.…”

“…We have assembled articles from a number of scientists who have made important contributions to this evolving field, and continue to shape it. The articles have been divided into a functional (Brooks et al, 2013;Henderson and Macefield, 2013;Ress and Chandrasekaran, 2013;Ritter et al, 2013) and a structural section (Deistung et al, 2013;Ford et al, 2013;Lambert et al, 2013;Yeo et al, 2013;Singleton et al, 2014).…”

“…Lambert et al (2013) use quantitative MRI and tensor based morphometry in a large study sample to characterize aging in the human brainstem. Singleton et al (2014) apply volumetric methods to demonstrate gray matter changes related to meditation and mindfulness-based intervention.…”