Diffusion tensor imaging and mild parkinsonian signs in cerebral small vessel disease

Mild Motor Signs in Healthy Aging Are Associated with Lower Synaptic Density in the Brain

OBJECTIVE

To investigate whether mild motor signs (MMS) in old age correlate with synaptic density in the brain.

BACKGROUND

Normal aging is associated with a decline in movement quality and quantity, commonly termed "mild parkinsonian signs" or more recently MMS. Whether MMS stem from global brain aging or pathology within motor circuits remains unresolved. The synaptic vesicle glycoprotein 2A positron emission tomography (PET) ligand 11 C-UCB-J allows the investigation of brain-motor associations at the synaptic level in vivo.

METHOD

Fifty-eight healthy older adults (≥50 years) were included from two monocentric control cohorts. Brain magnetic resonance imaging and 11 C-UCB-J PET data were available in 54 participants. 11 C-UCB-J PET binding was quantified by standardized uptake value ratio (SUVR) values in grey matter (GM) volumes of interest (VOIs): caudate, putamen, globus pallidus, substantia nigra, thalamus, cerebellum, and the frontal, parietal, temporal, and occipital cortex. Multiple linear regression analyses were performed with Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III score measuring MMS as the dependent variable and mean SUVR values in each VOI as the independent variable with age, Fazekas score (white matter lesion [WML] load), VOI and cohort as covariates.

RESULTS

Participants (68 ± 7.5 years; 52% female) had an average MDS-UPDRS part III score of 3.3 ± 2.8. The MDS-UPDRS part III score was inversely associated with synaptic density, independently of WML load or GM volume, in the caudate, substantia nigra, thalamus, cerebellum, and parietal, occipital, temporal cortex. Cohen's f2 showed moderate effect sizes for subcortical (range, 0.30-0.35), cortical (0.28-0.35) and cerebellar VOIs (0.31).

CONCLUSION

MMS in healthy aging are associated with lower synaptic density throughout the brain. © 2023 International Parkinson and Movement Disorder Society.

Contrast agent-free state-of-the-art magnetic resonance imaging on cerebral small vessel disease - Part 2: Diffusion tensor imaging and functional magnetic resonance imaging

Cerebral small vessel disease (cSVD) has been widely studied using conventional magnetic resonance imaging (MRI) methods, although the association between MRI findings and clinical features of cSVD is not always concordant. We assessed the additional contribution of contrast agent-free, state-of-the-art MRI techniques, particularly diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI), to understand brain damage and structural and functional connectivity impairment related to cSVD. We performed a review following the PICOS worksheet and Search Strategy, including 152 original papers in English, published from 2000 to 2022. For each MRI method, we extracted information about their contributions regarding the origins, pathology, markers, and clinical outcomes in cSVD. In general, DTI studies have shown that changes in mean, radial, and axial diffusivity measures are related to the presence of cSVD. In addition to the classical deficit in executive functions and processing speed, fMRI studies indicate connectivity dysfunctions in other domains, such as sensorimotor, memory, and attention. Neuroimaging metrics have been correlated with the diagnosis, prognosis, and rehabilitation of patients with cSVD. In short, the application of contrast agent-free, state-of-the-art MRI techniques has provided a complete picture of cSVD markers and tools to explore questions that have not yet been clarified about this clinical condition. Longitudinal studies are desirable to look for causal relationships between image biomarkers and clinical outcomes.

Cortico-striatal functional connectivity and cerebral small vessel disease: Contribution to mild Parkinsonian signs

BACKGROUND AND PURPOSE

Mild Parkinsonian signs (MPS) are common in older adults. We hypothesized that MPS are associated with lower functional connectivity (FC) in dopamine-dependent cortico-striatal networks, and these associations vary with white matter hyperintensity (WMH), a risk factor for MPS.

METHODS

We examined resting-state functional MRI in 266 participants (mean age 83; 57% female; 41% African American) with data on MPS (Unified Parkinson's Disease Rating Scale), demographics, cognition, muscle-skeletal, and cardiometabolic health. FC between cortex and striatum was examined separately for sensorimotor, executive, and limbic functional subregions. Logistic regression tested the association of FC in each network with MPS, adjusted for covariates. Interactions of FC by WMH were tested; and analyses were repeated stratified by WMH above/below the median.

RESULTS

Compared to those without MPS, those with MPS had lower cortico-striatal FC in the left executive network (adjusted odds ratio [95% confidence interval], p-value: 0.188 [0.043, 0.824], .027). The interaction with WMH was p = .064; left executive FC was inversely associated with MPS for high WMH (0.077 [0.010, 0.599], .014) but not low WMH participants (1.245 [0.128, 12.132], .850).

CONCLUSIONS

MPS appear related to lower executive network FC, robust to adjustment for other risk factors, and stronger for those with higher burden of WMH. Future longitudinal studies should examine the interplay between cerebral small vessel disease and connectivity influencing MPS.

Mild Parkinsonian Signs: A Systematic Review of Clinical, Imaging, and Pathological Associations

Mild parkinsonian signs (MPS) have been widely studied during the past 3 decades and proposed as a risk marker for neurodegenerative disease. This systematic review explores the epidemiology, clinical and prognostic associations, radiological features, and pathological findings associated with MPS in older adults free from neurodegenerative disease. We find that MPS as currently defined are strongly associated with increasing age and increased risk of development of Parkinson's disease (PD), all-cause dementia, disability, and death. Positive associations with later PD are found mainly in younger populations and those with other features of prodromal PD. There are currently no consistent radiological findings for MPS, and pathological studies have shown that MPS, at least in the oldest old, are often underpinned by mixed neuropathologies, including those associated with Alzheimer's disease, cerebrovascular disease, nigral neuronal loss, and Lewy bodies. Different subcategories of MPS appear to convey varying risk and specificity for PD and other outcomes. MPS overall are not specific for parkinsonian disorders and, although associated with increased risk of PD, can reflect multiple pathologies, particularly in older individuals. "Mild motor signs" appears a more appropriate term to avoid prognostic and pathological implications, and larger future studies to prospectively examine outcomes and associations of specific MPS subcategories are required. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Diffusion tensor imaging revealed different pathological processes of white matter hyperintensities

Background

Although increasing evidence showed the correlations between white matter hyperintensities (WMHs) and cognitive impairment, the relationship between them is still modest. Many researchers began to focus on the variation caused by the heterogeneity of WMH. We tried to explore the pathological heterogeneity in WMH by using diffusion tensor imaging (DTI), so as to provide a new insight into the future research.

Methods

Diffusion weighted images (DWIs) of the brain were acquired from 73 patients with WMH and 18 healthy controls, which were then modeled by DTI. We measured fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of white matter of the periventricular frontal lobe (pFL), periventricular occipital lobe (pOL), periventricular parietal lobe (pPL) and deep centrum ovales (dCO), and grouped these measures according to the Fazekas scale. Then we compared the DTI metrics of different regions with the same Fazekas scale grade.

Results

Significantly lower FA values (all p < 0.001), and higher MD (all p < 0.001) and RD values (all p < 0.001) were associated with WMH observed in the periventricular frontal lobe (pFL) compared to all other regions with the same Fazekas grades. The AD of WMH in the pFL was higher than that of pPL and dCO, but the differences between groups was not as high as of MD and RD, as indicated by the effect size. In the normal control group, DTI metrics between pFL and other regions were not significantly different or less significant different. The difference of DTI metrics of WMH between pPL, pOL and dCO was lower than that of normal white matter, as indicated by the effect size.

Conclusion

Distinct pathological processes can be revealed by DTI between frontal periventricular WMH and other regions. These processes may represent the effects of severe demyelination within the frontal periventricular WMH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02140-9.

Clinical and neuroimaging correlates of progression of mild parkinsonian signs in community-dwelling older adults

INTRODUCTION

Mild parkinsonian signs (MPS) are associated with morbidity. Identification of MPS progression markers may be vital for preventive management, yet has not been pursued. This study aimed to ascertain clinical/neuroimaging features predictive of MPS progression.

METHODS

205 participants in the Health ABC Study were included. MPS was defined using published guidelines. MPS progression was evaluated by determining UPDRS-III change between baseline and follow-up ≥2 years later. Standard brain MRI and DTI were obtained at baseline. Correlation coefficients between demographics, vascular risk factors, imaging markers, and UPDRS-III change were adjusted for follow-up time. Linear regression was used to adjust for possible confounders in the relationship between imaging markers and MPS progression.

RESULTS

30% of participants had baseline MPS. Demographics and risk factors did not differ significantly between participants with MPS (MPS+) and without MPS (MPS-). Mean follow-up time was 3.8±0.8 years. Older age, male gender, diabetes were associated with faster rate of UPDRS-III change in MPS- but not MPS+ participants. Among MPS- participants, the only imaging marker associated with faster UPDRS-III progression was higher gray matter mean diffusivity (MD), widespread in various cortico-subcortical bihemispheric regions, independent of age, gender, diabetes. No imaging features were associated with UPDRS-III change among MPS+ participants.

CONCLUSIONS

Lower gray matter integrity predicted MPS progression in those who did not have baseline MPS. Microstructural imaging may capture early changes related to MPS development, prior to macrostructural change. Any future management promoting gray matter preservation may inhibit MPS development.

Progression of White Matter Hyperintensities Preceded by Heterogeneous Decline of Microstructural Integrity

BACKGROUND AND PURPOSE

White matter hyperintensities (WMH) are frequently seen on neuroimaging of elderly and are associated with cognitive decline and the development of dementia. Yet, the temporal dynamics of conversion of normal-appearing white matter (NAWM) into WMH remains unknown. We examined whether and when progression of WMH was preceded by changes in fluid-attenuated inversion recovery and diffusion tensor imaging values, thereby taking into account differences between participants with mild versus severe baseline WMH.

METHODS

From 266 participants of the RUN DMC study (Radboud University Nijmegen Diffusion Tensor and Magnetic Resonance Imaging Cohort), we semiautomatically segmented WMH at 3 time points for 9 years. Images were registered to standard space through a subject template. We analyzed differences in baseline fluid-attenuated inversion recovery, fractional anisotropy, and mean diffusivity (MD) values and changes in MD values over time between 4 regions: (1) remaining NAWM, (2) NAWM converting into WMH in the second follow-up period, (3) NAWM converting into WMH in the first follow-up period, and (4) WMH.

RESULTS

NAWM converting into WMH in the first or second time interval showed higher fluid-attenuated inversion recovery and MD values than remaining NAWM. MD values in NAWM converting into WMH in the first time interval were similar to MD values in WMH. When stratified by baseline WMH severity, participants with severe WMH had higher fluid-attenuated inversion recovery and MD and lower fractional anisotropy values than participants with mild WMH, in all areas including the NAWM. MD values in WMH and in NAWM that converted into WMH continuously increased over time.

CONCLUSIONS

Impaired microstructural integrity preceded conversion into WMH and continuously declined over time, suggesting a continuous disease process of white matter integrity loss that can be detected using diffusion tensor imaging even years before WMH become visible on conventional neuroimaging. Differences in microstructural integrity between participants with mild versus severe WMH suggest heterogeneity of both NAWM and WMH, which might explain the clinical variability observed in patients with similar small vessel disease severity.

Association between Various Brain Pathologies and Gait Disturbance

BACKGROUND

Approximately 30% of older adults have disrupted gait. It is associated with increased risk of cognitive decline, disability, dementia, and death. Additionally, most older adults present with 1 or more neuropathologies at autopsy. Recently, there has been an effort to investigate the association between subclinical neuropathology and gait.

SUMMARY

We reviewed studies that investigated the association between gait and neuropathologies. Although all pathologies reviewed were associated with gait, grey matter atrophy was most consistently linked with poorer gait performance. Studies investigating the association between white matter and gait focused primarily on total white matter. Future research using more parsed regional analysis will provide more insight into this relationship. Evidence from studies investigating neuronal activity and gait suggests that gait disruption is associated with both under- and overactivation. Additional research is needed to delineate these conflicting results. Lastly, early evidence suggests that both amyloid and tau aggregation negatively impact multiple gait parameters, but additional studies are warranted. Overall, there was substantial methodological heterogeneity and a paucity of longitudinal studies. Key Messages: Longitudinal studies mapping changes in different types of neuropathology as they relate to changes in multiple gait parameters are needed to better understand trajectories of pathology and gait.

Patterns of focal gray matter atrophy are associated with bradykinesia and gait disturbances in older adults

OBJECTIVES

Identify the neuroimaging correlates of parkinsonian signs in older adults living in the community.

METHODS

Magnetic resonance imaging was obtained in 307 adults (82.9 years, 55% women, 39% blacks) concurrently with the Unified Parkinson Disease Rating scale-motor part. Magnetic resonance imaging measures included volume of whole-brain white matter hyperintensities and of gray matter for primary sensorimotor, supplementary motor, medial temporal areas, cerebellum, prefronto-parietal cortex, and basal ganglia.

RESULTS

About 25% of the participants had bradykinesia, 26% had gait disturbances, and 12% had tremor. Compared with those without, adults with any one of these signs were older, walked more slowly, had worse scores on tests of cognition, mood and processing speed, and higher white matter hyperintensities volume (all p ≤ .002). Gray matter volume of primary sensorimotor area was associated with bradykinesia (standardized odds ratio [95% confidence interval]: 0.46 [0.31, 0.68], p < .0001), and gray matter volume of medial temporal area was associated with gait disturbances (0.56 [0.42, 0.83], p < .0001), independent of white matter hyperintensities volume and age. Further adjustment for measures of muscle strength, cardiovascular health factors, cognition, processing speed, and mood or for gait speed did not substantially change these results.

CONCLUSIONS

Atrophy within primary sensorimotor and medial temporal areas might be important for development of bradykinesia and of gait disturbances in community-dwelling elderly adults. The pathways underlying these associations may not include changes in white matter hyperintensities volume, cognition, information processing speed, mood, or gait speed.