Brain Magnetic Resonance Imaging Techniques in the Diagnosis of Parkinsonian Syndromes

An overview: Radiotracers and nano-radiopharmaceuticals for diagnosis of Parkinson's disease

Parkinson's disease (PD) is a widespread progressive neurodegenerative disease. Clinical diagnosis approaches are insufficient to provide an early and accurate diagnosis before a substantial of loss of dopaminergic neurons. PET and SPECT can be used for accurate and early diagnosis of PD by using target-specific radiotracers. Additionally, the importance of BBB penetrating targeted nanosystems has increased in recent years. This article reviews targeted radiopharmaceuticals used in clinics and novel nanocarriers for research purposes of PD imaging.

Multimodality imaging of neurodegenerative disorders with a focus on multiparametric magnetic resonance and molecular imaging

Neurodegenerative diseases afflict a large number of persons worldwide, with the prevalence and incidence of dementia rapidly increasing. Despite their prevalence, clinical diagnosis of dementia syndromes remains imperfect with limited specificity. Conventional structural-based imaging techniques also lack the accuracy necessary for confident diagnosis. Multiparametric magnetic resonance imaging and molecular imaging provide the promise of improving specificity and sensitivity in the diagnosis of neurodegenerative disease as well as therapeutic monitoring of monoclonal antibody therapy. This educational review will briefly focus on the epidemiology, clinical presentation, and pathologic findings of common and uncommon neurodegenerative diseases. Imaging features of each disease spanning from conventional magnetic resonance sequences to advanced multiparametric methods such as resting-state functional magnetic resonance imaging and arterial spin labeling imaging will be described in detail. Additionally, the review will explore the findings of each diagnosis on molecular imaging including single-photon emission computed tomography and positron emission tomography with a variety of clinically used and experimental radiotracers. The literature and clinical cases provided demonstrate the power of advanced magnetic resonance imaging and molecular techniques in the diagnosis of neurodegenerative diseases and areas of future and ongoing research. With the advent of combined positron emission tomography/magnetic resonance imaging scanners, hybrid protocols utilizing both techniques are an attractive option for improving the evaluation of neurodegenerative diseases.

Imaging modalities in differential diagnosis of Parkinson’s disease: opportunities and challenges

Background

Parkinson’s disease (PD) diagnosis is yet largely based on the related clinical aspects. However, genetics, biomarkers, and neuroimaging studies have demonstrated a confirming role in the diagnosis, and future developments might be used in a pre-symptomatic phase of the disease.

Main text

This review provides an update on the current applications of neuroimaging modalities for PD diagnosis. A literature search was performed to find published studies that were involved on the application of different imaging modalities for PD diagnosis. An organized search of PubMed/MEDLINE, Embase, ProQuest, Scopus, Cochrane, and Google Scholar was performed based on MeSH keywords and suitable synonyms. Two researchers (TM and JPI) independently and separately performed the literature search. Our search strategy in each database was done by the following terms: ((Parkinson [Title/Abstract]) AND ((“Parkinsonian syndromes ”[Mesh]) OR Parkinsonism [Title/Abstract])) AND ((PET [Title/Abstract]) OR “SPECT”[Mesh]) OR ((Functional imaging, Transcranial sonography [Title/Abstract]) OR “Magnetic resonance spectroscopy ”[Mesh]). Database search had no limitation in time, and our last update of search was in February 2021. To have a comprehensive search and to find possible relevant articles, a manual search was conducted on the reference list of the articles and limited to those published in English.

Conclusion

Early diagnosis of PD could be vital for early management and adequate neuroprotection. Recent neuroimaging modalities such as SPECT and PET imaging using radiolabeled tracers, MRI, and CT are used to discover the disease. By the modalities, it is possible to early diagnose dopaminergic degeneration and also to differentiate PD from others parkinsonian syndromes, to monitor the natural progression of the disease and the effect of neuroprotective treatments on the progression. In this regard, functional imaging techniques have provided critical insights and roles on PD.

Differentiating PSP from MSA using MR planimetric measurements: a systematic review and meta-analysis

Differential diagnosis of parkinsonian syndromes is considered one of the most challenging in neurology. Quantitative MR planimetric measurements were reported to discriminate between progressive supranuclear palsy (PSP) and non-PSP-parkinsonism. Several studies have used midbrain to pons ratio (M/P) and the Magnetic Resonance Parkinsonism Index (MRPI) in distinguishing PSP patients from those with Parkinson's disease. The current meta-analysis aimed to compare the performance of these measures in discriminating PSP from multiple system atrophy (MSA). A systematic MEDLINE review identified 59 out of 2984 studies allowing a calculation of sensitivity and specificity using the MRPI or M/P. Meta-analyses of results were carried out using random effects modelling. To assess study quality and risk of bias, the QUADAS-2 tool was used. Eight studies were suitable for analysis. The meta-analysis showed a pooled sensitivity and specificity for the MRPI of PSP versus MSA of 79.2% (95% CI 72.7-84.4%) and 91.2% (95% CI 79.5-96.5%), and 84.1% (95% CI 77.2-89.2%) and 89.2% (95% CI 81.8-93.8%), respectively, for the M/P. The QUADAS-2 toolbox revealed a high risk of bias regarding the methodological quality of patient selection and index test, as all patients were seen in a specialized outpatient department without avoiding case control design and no predefined threshold was given regarding MRPI or M/P cut-offs. Planimetric brainstem measurements, in special the MRPI and M/P, yield high diagnostic accuracy for the discrimination of PSP from MSA. However, there is an urgent need for well-designed, prospective validation studies to ameliorate the concerns regarding the risk of bias.

Differentiating Between Low- and High-grade Glioma Tumors Measuring Apparent Diffusion Coefficient Values in Various Regions of the Brain

Objectives

Our study aimed to apply the apparent diffusion coefficient (ADC) values to quantify the differences between low- and high-grade glioma tumors.

Methods

We conducted a multicenter, retrospective study between September to December 2019. Magnetic resonance imaging (MRI) diffusion-weighted images (DWIs), and the pathologic findings of 56 patients with glioma tumors (low grade = 28 and high grade = 28) were assessed to measure the ADC values in the tumor center, tumor edema, boundary area between tumor with normal tissue, and inside the healthy hemisphere. These values were compared between the two groups, and cut-off values were calculated using the receiver operating characteristic curve.

Results

We saw significant differences between the mean ADC values measured in the tumor center and edema between high- and low-grade tumors (p< 0.005). The ADC values in the boundary area between tumors with normal tissue and inside healthy hemisphere did not significantly differ in the groups. The ADC values at tumor center and edema were higher than 1.12 × 10^-3 mm²/s (sensitivity = 100% and specificity = 96.0%) and 1.15 × 10^-3 mm²/s (sensitivity = 75.0% and specificity = 64.0%), respectively, could be classified as low-grade tumors.

Conclusions

The ADC values from the MRI DWIs in the tumor center and edema could be used as an appropriate method for investigating the differences between low- and high-grade glioma tumors. The ADC values in the boundary area and healthy tissues had no diagnostic values in grading the glioma tumors.

Investigating the 1-year decline in midbrain-to-pons ratio in the differential diagnosis of PSP and IPD

Background

A reliable measure of PSP-specific midbrain atrophy, the midbrain-to-pons ratio (MTPR) has been reported to support the differential diagnosis of progressive supranuclear palsy (PSP) from idiopathic Parkinson’s disease (IPD). Since longitudinal analyses are lacking so far, the present study aimed to evaluate the diagnostic value of the relative change of MTPR (relΔt_MTPR) over a 1-year period in patients with PSP, IPD, and healthy controls (HC).

Methods

Midsagittal individual MRIs of patients with PSP (n = 15), IPD (n = 15), and healthy controls (HC; n = 15) were assessed and the MTPR at baseline and after 1 year were defined. The diagnostic accuracy of the MTPR and its relative change were evaluated using ROC curve analyses.

Results

PSP-patients had a significantly lower MTPR at baseline (M = 0.45 ± 0.06), compared to both non-PSP groups (F (2, 41) = 62.82, p < 0.001), with an overall predictive accuracy of 95.6% for an MTPR ≤ 0.54. PSP-patients also presented a significantly stronger 1-year decline in MTPR compared to IPD (p < 0.001). Though predictive accuracy of relΔ_t_MTPR for PSP (M = − 4.74% ± 4.48) from IPD (M =  + 1.29 ± 3.77) was good (76.6%), ROC analysis did not reveal a significant improvement of diagnostic accuracy by combining the MTPR and relΔ_t_MTPR (p = 0.670). Still, specificity for PSP increased, though not significantly (p = 0.500).

Conclusion

The present results indicate that the relΔ_t_MTPR is a potentially useful tool to support the differential diagnosis of PSP from IPD. For its relative 1-year change, still, more evaluation is needed.

ACR Appropriateness Criteria® Movement Disorders and Neurodegenerative Diseases

Movement disorders and neurodegenerative diseases are a variety of conditions that involve progressive neuronal degeneration, injury, or death. Establishing the correct diagnosis of a movement disorder or neurodegenerative process can be difficult due to the variable features of these conditions, unusual clinical presentations, and overlapping symptoms and characteristics. MRI has an important role in the initial assessment of these patients, although a combination of imaging and laboratory and genetic tests is often needed for complete evaluation and management. This document summarizes the imaging appropriateness data for rapidly progressive dementia, chorea, Parkinsonian syndromes, suspected neurodegeneration with brain iron accumulation, and suspected motor neuron disease. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

No effect of age, gender and total intracranial volume on brainstem MR planimetric measurements

Objectives

MR planimetry of brainstem structures can be helpful for the discrimination of Parkinsonian syndromes. It has been suggested that ageing might influence brainstem MR measurements assessed by MR planimetry, while effects of gender and total intracranial volume (TIV) have not been assessed so far. The aim of this study was to evaluate age, gender and TIV effects on brainstem MR planimetric measures.

Methods

Brainstem MR planimetric measures of diameters (midbrain, pons, middle and superior cerebellar peduncle) and areas (pons and midbrain), the derived ratios, and the magnetic resonance Parkinsonism index (MRPI) were assessed on 1.5-T MR images in a large cohort of 97 healthy controls and analysed for the influence of age, gender and TIV with univariate and multivariate linear models.

Results

Neither gender nor age effects on planimetric measurements were observed in the population relevant for the differential diagnosis of neurodegenerative Parkinsonism, aged 50 to 80 years, except for single area-derived measurements, with gender effects on pontine area (p = 0.013) and age effects on midbrain area (p = 0.037). Results were similar upon inclusion of the TIV in the analyses.

Conclusions

There is no need to correct for age, gender or TIV when using brainstem-derived MR planimetric measurements in the differential diagnosis of neurodegenerative Parkinsonism.

Key Points

• There were no gender effects on single or combined imaging measurements of the brainstem in the population aged 50 to 80 years, the age range relevant for the differential diagnosis of neurodegenerative Parkinsonism (except for pontine area).

• There were no age effects on single or combined imaging measurements of the brainstem in the population aged 50 to 80 years, the age range relevant for the differential diagnosis of neurodegenerative Parkinsonism (except for midbrain area).

• There is no need for age- or gender-specific cut-offs for the relevant age group.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06504-1) contains supplementary material, which is available to authorized users.

Cortico-basal white matter alterations occurring in Parkinson's disease

Magnetic resonance imaging studies typically use standard anatomical atlases for identification and analyses of (patho-)physiological effects on specific brain areas; these atlases often fail to incorporate neuroanatomical alterations that may occur with both age and disease. The present study utilizes Parkinson's disease and age-specific anatomical atlases of the subthalamic nucleus for diffusion tractography, assessing tracts that run between the subthalamic nucleus and a-priori defined cortical areas known to be affected by Parkinson's disease. The results show that the strength of white matter fiber tracts appear to remain structurally unaffected by disease. Contrary to that, Fractional Anisotropy values were shown to decrease in Parkinson's disease patients for connections between the subthalamic nucleus and the pars opercularis of the inferior frontal gyrus, anterior cingulate cortex, the dorsolateral prefrontal cortex and the pre-supplementary motor, collectively involved in preparatory motor control, decision making and task monitoring. While the biological underpinnings of fractional anisotropy alterations remain elusive, they may nonetheless be used as an index of Parkinson's disease. Moreover, we find that failing to account for structural changes occurring in the subthalamic nucleus with age and disease reduce the accuracy and influence the results of tractography, highlighting the importance of using appropriate atlases for tractography.

Use of Magnetic Resonance Imaging and Artificial Intelligence in Studies of Diagnosis of Parkinson's Disease

Parkinson's disease (PD) is a common neurodegenerative disorder. It has a delitescent onset and a slow progress. The clinical manifestations of PD in patients are highly heterogeneous. Thus, PD diagnosis process is complex and mainly depends on the professional knowledge and experience of the physician. Magnetic resonance imaging (MRI) could detect the small changes in the brain of PD patients, and quantitative analysis of brain MRI may improve the clinical diagnosis efficiency. However, due to the complexity of clinical courses in PD and the high dimensionality in multimodal MRI data, traditional mathematical analysis could not effectively extract the huge information in them. Up to now, the accuracy of PD diagnosis in large sample size is still unsatisfying. As artificial intelligence (AI) is becoming more mature, varieties of statistical models and machine learning (ML) algorithms have been used for quantitative imaging data analysis to explore a diagnostic result. This review aims to state an overview of existing research recently that used statistical ML/AI methods to perform quantitative analysis of MR image data for the study of PD diagnosis. First we review the recent research in three subareas: diagnosis, differential diagnosis, and subtyping of PD. Then we described the overall workflow from MR image to classification result. Finally, we summarized a critical assessment of the current research and provide some recommendations for likely future research developments and trends.

The Application of Unsupervised Clustering Methods to Alzheimer's Disease

Clustering is a powerful machine learning tool for detecting structures in datasets. In the medical field, clustering has been proven to be a powerful tool for discovering patterns and structure in labeled and unlabeled datasets. Unlike supervised methods, clustering is an unsupervised method that works on datasets in which there is no outcome (target) variable nor is anything known about the relationship between the observations, that is, unlabeled data. In this paper, we focus on studying and reviewing clustering methods that have been applied to datasets of neurological diseases, especially Alzheimer’s disease (AD). The aim is to provide insights into which clustering technique is more suitable for partitioning patients of AD based on their similarity. This is important as clustering algorithms can find patterns across patients that are difficult for medical practitioners to find. We further discuss the implications of the use of clustering algorithms in the treatment of AD. We found that clustering analysis can point to several features that underlie the conversion from early-stage AD to advanced AD. Furthermore, future work can apply semi-clustering algorithms on AD datasets, which will enhance clusters by including additional information.

Corticobasal syndrome: neuroimaging and neurophysiological advances

Corticobasal degeneration (CBD) is a neurodegenerative condition characterized by 4R tau protein deposition in several brain regions that clinically manifests itself as a heterogeneous atypical parkinsonism typically expressed in adulthood. The prototypical clinical phenotype of CBD is corticobasal syndrome (CBS). Important insights into the pathophysiological mechanisms underlying motor and higher cortical symptoms in CBS have been gained by using advanced neuroimaging and neurophysiological techniques. Structural and functional neuroimaging studies often show asymmetric cortical and subcortical abnormalities, mainly involving perirolandic and parietal regions and basal ganglia structures. Neurophysiological investigations including electroencephalography and somatosensory evoked potentials provide useful information on the origin of myoclonus and on cortical sensory loss. Transcranial magnetic stimulation demonstrates heterogeneous and asymmetric changes in the excitability and plasticity of primary motor cortex and abnormal hemispheric connectivity. Neuroimaging and neurophysiological abnormalities in multiple brain areas reflect asymmetric neurodegeneration, leading to asymmetric motor and higher cortical symptoms in CBS.

Structural Imaging in Atypical Parkinsonism

Qualitative and quantitative structural magnetic resonance imaging offer objective measures of the underlying neurodegeneration in atypical parkinsonism. Regional changes in tissue volume, signal changes and increased deposition of iron as assessed with different structural MRI techniques are surrogate markers of underlying neurodegeneration and may reflect cell loss, microglial proliferation and astroglial activation. Structural MRI has been explored as a tool to enhance diagnostic accuracy in differentiating atypical parkinsonian disorders (APDs). Moreover, the longitudinal assessment of serial structural MRI-derived parameters offers the opportunity for robust inferences regarding the progression of APDs. This review summarizes recent research findings as (1) a diagnostic tool for APDs as well as (2) as a tool to assess longitudinal changes of serial MRI-derived parameters in the different APDs.

Clinical Application of Brain MRI in the Diagnostic Work-up of Parkinsonism

BACKGROUND

Differentiating Parkinson's disease and atypical parkinsonism on clinical parameters is challenging, especially in early disease courses. This is due to large overlap in symptoms and because the so called red flags, i.e. symptoms indicating atypical parkinsonism, have not (fully) developed. Brain MRI can aid to improve the accuracy and confidence about the diagnosis.

OBJECTIVE AND METHODS

In the current paper, we discuss when brain MRI should be performed in the diagnostic work-up of parkinsonism, our preferred brain MRI scanning protocol, and the diagnostic value of specific abnormalities.

RESULTS AND CONCLUSIONS

The main purpose of brain MRI is to assess cerebrovascular damage, and to exclude other possible - and sometimes treatable - causes of parkinsonism, such as normal pressure hydrocephalus. Furthermore, brain MRI can support the possible or probable diagnosis of a specific form of atypical parkinsonism.

Neurophysiology and neurochemistry of corticobasal syndrome

Corticobasal syndrome is a rare neurodegenerative disorder, which presents with a progressive, asymmetrical, akinetic rigid syndrome and early cortical signs. However, clinical, pathological, and electrophysiological heterogeneity makes the understanding of this syndrome challenging. Corticobasal syndrome can have various pathological substrates including corticobasal degeneration, Alzheimer's disease, Fronto-temporal degeneration with TDP inclusions, Creutzfeldt-Jakob disease, and progressive supranuclear palsy (PSP). Furthermore, tools such as transcranial magnetic stimulation (TMS) and functional neuroimaging techniques like PET and SPECT have not been adequately used to supplement the clinico-pathological heterogeneity. TMS studies in CBS have revealed changes in cortical excitability and transcortical inhibition. Despite the availability of more than 2 decades, its potential in CBS has not been fully utilized in studying the cortical plasticity and effect of Levodopa on central neurophysiology. PET and SPECT studies in CBS have shown abnormalities in regional glucose metabolism, asymmetrical involvement of presynaptic dopaminergic system, and ascending cholinergic connections to the cortex. While most studies have shown normal D2 receptor-binding activity in striatum of CBS cases, the results have not been unanimous. Functional neuroimaging and TMS studies in CBS have shown the involvement of GABAergic, muscarinic, and dopaminergic systems. In this review, we aim to provide the current state of understanding of central neurophysiology and neurochemistry of CBS using TMS and functional neuroimaging techniques. We also highlight the heterogeneous nature of this disorder and the existing knowledge gaps.

[Degenerative cerebellar diseases and differential diagnoses]

CLINICAL/METHODICAL ISSUE

Cerebellar syndromes result in distinct clinical symptoms, such as ataxia, dysarthria, dysmetria, intention tremor and eye movement disorders.

STANDARD RADIOLOGICAL METHODS

In addition to the medical history and clinical examination, imaging is particularly important to differentiate other diseases, such as hydrocephalus and multi-infarct dementia from degenerative cerebellar diseases. Degenerative diseases with cerebellar involvement include Parkinson's disease, multiple system atrophy as well as other diseases including spinocerebellar ataxia.

ACHIEVEMENTS

In addition to magnetic resonance imaging (MRI), nuclear medicine imaging investigations are also helpful for the differentiation.

PRACTICAL RECOMMENDATIONS

Axial fluid-attenuated inversion recovery (FLAIR) and T2-weighted sequences can sometimes show a signal increase in the pons as a sign of degeneration of pontine neurons and transverse fibers in the basilar part of the pons. The imaging is particularly necessary to exclude other diseases, such as normal pressure hydrocephalus (NPH), multi-infarct dementia and cerebellar lesions.

Magnetic resonance imaging for the diagnosis of Parkinson's disease

The differential diagnosis of parkinsonian syndromes is considered one of the most challenging in neurology and error rates in the clinical diagnosis can be high even at specialized centres. Despite several limitations, magnetic resonance imaging (MRI) has undoubtedly enhanced the diagnostic accuracy in the differential diagnosis of neurodegenerative parkinsonism over the last three decades. This review aims to summarize research findings regarding the value of the different MRI techniques, including advanced sequences at high- and ultra-high-field MRI and modern image analysis algorithms, in the diagnostic work-up of Parkinson's disease. This includes not only the exclusion of alternative diagnoses for Parkinson's disease such as symptomatic parkinsonism and atypical parkinsonism, but also the diagnosis of early, new onset, and even prodromal Parkinson's disease.

Diffusion tensor imaging in Parkinson's disease: Review and meta-analysis

BACKGROUND

Neuroimaging studies help us better understand the pathophysiology and symptoms of Parkinson's disease (PD). In several of these studies, diffusion tensor imaging (DTI) was used to investigate structural changes in cerebral tissue. Although data have been provided as regards to specific brain areas, a whole brain meta-analysis is still missing.

METHODS

We compiled 39 studies in this meta-analysis: 14 used fractional anisotropy (FA), 1 used mean diffusivity (MD), and 24 used both indicators. These studies comprised 1855 individuals, 1087 with PD and 768 healthy controls. Regions of interest were classified anatomically (subcortical structures; white matter; cortical areas; cerebellum). Our statistical analysis considered the disease effect size (DES) as the main variable; the heterogeneity index (I2) and Pearson's correlations between the DES and co-variables (demographic, clinical and MRI parameters) were also calculated.

RESULTS

Our results showed that FA-DES and MD-DES were able to distinguish between patients and healthy controls. Significant differences, indicating degenerations, were observed within the substantia nigra, the corpus callosum, and the cingulate and temporal cortices. Moreover, some findings (particularly in the corticospinal tract) suggested opposite brain changes associated with PD. In addition, our results demonstrated that MD-DES was particularly sensitive to clinical and MRI parameters, such as the number of DTI directions and the echo time within white matter.

CONCLUSIONS

Despite some limitations, DTI appears as a sensitive method to study PD pathophysiology and severity. The association of DTI with other MRI methods should also be considered and could benefit the study of brain degenerations in PD.

Gray Matter Abnormalities in Idiopathic Parkinson's Disease: Evaluation by Diffusional Kurtosis Imaging and Neurite Orientation Dispersion and Density Imaging

Mapping gray matter (GM) pathology in Parkinson's disease (PD) with conventional MRI is challenging, and the need for more sensitive brain imaging techniques is essential to facilitate early diagnosis and assessment of disease severity. GM microstructure was assessed with GM-based spatial statistics applied to diffusion kurtosis imaging (DKI) and neurite orientation dispersion imaging (NODDI) in 30 participants with PD and 28 age- and gender-matched controls. These were compared with currently used assessment methods such as diffusion tensor imaging (DTI), voxel-based morphometry (VBM), and surface-based cortical thickness analysis. Linear discriminant analysis (LDA) was also used to test whether subject diagnosis could be predicted based on a linear combination of regional diffusion metrics. Significant differences in GM microstructure were observed in the striatum and the frontal, temporal, limbic, and paralimbic areas in PD patients using DKI and NODDI. Significant correlations between motor deficits and GM microstructure were also noted in these areas. Traditional VBM and surface-based cortical thickness analyses failed to detect any GM differences. LDA indicated that mean kurtosis (MK) and intra cellular volume fraction (ICVF) were the most accurate predictors of diagnostic status. In conclusion, DKI and NODDI can detect cerebral GM abnormalities in PD in a more sensitive manner when compared with conventional methods. Hence, these methods may be useful for the diagnosis of PD and assessment of motor deficits. Hum Brain Mapp 38:3704-3722, 2017. © 2017 Wiley Periodicals, Inc.

A Fully Automated, Atlas-Based Approach for Superior Cerebellar Peduncle Evaluation in Progressive Supranuclear Palsy Phenotypes

BACKGROUND AND PURPOSE

The superior cerebellar peduncle is damaged in progressive supranuclear palsy. However, alterations differ between progressive supranuclear palsy with Richardson syndrome and progressive supranuclear palsy-parkinsonism. In this study, we propose an automated tool for superior cerebellar peduncle integrity assessment and test its performance in patients with progressive supranuclear palsy with Richardson syndrome, progressive supranuclear palsy-parkinsonism, Parkinson disease, and healthy controls.

MATERIALS AND METHODS

Structural and diffusion MRI was performed in 21 patients with progressive supranuclear palsy with Richardson syndrome, 9 with progressive supranuclear palsy-parkinsonism, 20 with Parkinson disease, and 30 healthy subjects. In a fully automated pipeline, the left and right superior cerebellar peduncles were first identified on MR imaging by using a tractography-based atlas of white matter tracts; subsequently, volume, mean diffusivity, and fractional anisotropy were extracted from superior cerebellar peduncles. These measures were compared across groups, and their discriminative power in differentiating patients was evaluated in a linear discriminant analysis.

RESULTS

Compared with those with Parkinson disease and controls, patients with progressive supranuclear palsy with Richardson syndrome showed alterations of all superior cerebellar peduncle metrics (decreased volume and fractional anisotropy, increased mean diffusivity). Patients with progressive supranuclear palsy-parkinsonism had smaller volumes than those with Parkinson disease and controls and lower fractional anisotropy than those with Parkinson disease. Patients with progressive supranuclear palsy with Richardson syndrome had significantly altered fractional anisotropy and mean diffusivity in the left superior cerebellar peduncle compared with those with progressive supranuclear palsy-parkinsonism. Discriminant analysis with the sole use of significant variables separated progressive supranuclear palsy-parkinsonism from progressive supranuclear palsy with Richardson syndrome with 70% accuracy and progressive supranuclear palsy-parkinsonism from Parkinson disease with 74% accuracy.

CONCLUSIONS

We demonstrate the feasibility of an automated approach for extracting multimodal MR imaging metrics from the superior cerebellar peduncle in healthy subjects and patients with parkinsonian. We provide evidence that structural and diffusion measures of the superior cerebellar peduncle might be valuable for computer-aided diagnosis of progressive supranuclear palsy subtypes and for differentiating patients with progressive supranuclear palsy-parkinsonism from with those with Parkinson disease.

Brain imaging findings in idiopathic REM sleep behavior disorder (RBD) - A systematic review on potential biomarkers for neurodegeneration

Idiopathic rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by the loss of physiological atonia of skeletal muscles with abnormal behavior during dream sleep. RBD may be the initial manifestation of neurodegenerative diseases, particularly of α-synucleinopathies such as Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). However, gauging the individual risk of subsequent phenoconversion and making assumptions on the type of disease that may subsequently follow RBD is challenging. Over the past years, a growing number of studies have sought to establish reliable neuroimaging markers to detect neurodegenerative brain changes in RBD subjects at the earliest possible stage. The present review summarizes recent advances in brain imaging in RBD and provides recommendations for the application of currently available structural and functional neuroimaging modalities to monitor disease progression and risk of subsequent phenoconversion. Further imaging research applying multimodal approaches is encouraged to enhance accuracy of prognoses. Additionally, more longitudinal studies are warranted to validate findings from cross-sectional studies on RBD progression and risk of subsequent phenoconversion. Aside from enabling reliable prognoses on a single-subject-level in the near future, this might give further insight into RBD pathophysiology, and finally augment the development of intervention strategies and disease-modifying therapies.

In vivo imaging of neuroinflammation in schizophrenia

In recent years evidence has accumulated to suggest that neuroinflammation might be an early pathology of schizophrenia that later leads to neurodegeneration, yet the exact role in the etiology, as well as the source of neuroinflammation, are still not known. The hypothesis of neuroinflammation involvement in schizophrenia is quickly gaining popularity, and thus it is imperative that we have reliable and reproducible tools and measures that are both sensitive, and, most importantly, specific to neuroinflammation. The development and use of appropriate human in vivo imaging methods can help in our understanding of the location and extent of neuroinflammation in different stages of the disorder, its natural time-course, and its relation to neurodegeneration. Thus far, there is little in vivo evidence derived from neuroimaging methods. This is likely the case because the methods that are specific and sensitive to neuroinflammation are relatively new or only just being developed. This paper provides a methodological review of both existing and emerging positron emission tomography and magnetic resonance imaging techniques that identify and characterize neuroinflammation. We describe \how these methods have been used in schizophrenia research. We also outline the shortcomings of existing methods, and we highlight promising future techniques that will likely improve state-of-the-art neuroimaging as a more refined approach for investigating neuroinflammation in schizophrenia.

Computer-based magnetic resonance imaging as a tool in clinical diagnosis in neurodegenerative diseases

Magnetic resonance imaging (MRI) is one of the core elements within the differential diagnostic work-up of patients with neurodegenerative diseases such as dementia syndromes, Parkinsonian syndromes, and motor neuron diseases. Currently, computerized MRI analyses are not routinely used for individual diagnosis; however, they have improved the anatomical understanding of pathomorphological alterations in various neurodegenerative diseases by quantitative comparisons between patients and controls at the group level. For multiparametric MRI protocols, including T1-weighted MRI, diffusion-weighted imaging, and intrinsic functional connectivity MRI, the potential as a surrogate marker is a subject of investigation. The additional value of MRI with respect to diagnosis at the individual level and for future disease-modifying multicentre trials remains to be defined. Here, we give an overview of recent applications of multiparametric MRI to patients with various neurodegenerative diseases. Starting from applications at the group level, continuous progress of a transfer to individual diagnostic classification is ongoing.

Structural and functional imaging in parkinsonian syndromes

Movement disorders with parkinsonian features are common, and in recent years imaging has assumed a greater role in diagnosis and management. Thus, it is important that radiologists become familiar with the most common imaging patterns of parkinsonism, especially given the significant clinical overlap and diagnostic difficulty associated with these disorders. The authors review the most common magnetic resonance (MR) and molecular imaging patterns of idiopathic Parkinson disease and atypical parkinsonian syndromes. They also discuss the interpretation of clinically available molecular imaging studies, including assessment of cerebral metabolism with 2-[fluorine-18]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET), cortical amyloid deposition with carbon 11 ((11)C) Pittsburgh compound B and fluorine 18 ((18)F) florbetapir PET, and dopaminergic activity with iodine 123 ((123)I) ioflupane single photon emission computed tomography (SPECT). Although no single imaging test is diagnostic, a combination of tests may help narrow the differential diagnosis. Findings at (123)I ioflupane SPECT can confirm the loss of dopaminergic neurons in patients with parkinsonism and help distinguish these syndromes from treatable conditions, including essential tremor and drug-induced parkinsonism. FDG PET uptake can demonstrate patterns of neuronal dysfunction that are specific to a particular parkinsonian syndrome. Although MR imaging findings are typically nonspecific in parkinsonian syndromes, classic patterns of T2 signal change can be seen in multiple system atrophy and progressive supranuclear palsy. Finally, positive amyloid-binding PET findings can support the diagnosis of dementia with Lewy bodies. Combined with a thorough clinical evaluation, multimodality imaging information can afford accurate diagnosis, allow selection of appropriate therapy, and provide important prognostic information.

Role of neuroimaging in multidisciplinary approach towards Non-Alzheimer's dementia

Dementia is defined as chronic deterioration of intellectual function and cognitive skills significant enough to interfere with the ability to perform daily activities. Recent advances in the treatment of dementia have renewed interest in the use of various neuroimaging techniques that can assist in the diagnosis and differentiation of various subtypes. Neuroimaging and computational techniques have helped the radiological community to monitor disease progression of various neurodegenerative conditions presenting with dementia, such as Alzheimer disease, frontotemporal lobe dementia (FTLD), progressive supranuclear palsy (PSP) and multisystem atrophy-cerebellar variant (MSA-C), and their response to newer therapies. Prompt identification of treatable or reversible forms of dementia, such as tumours, subdural haemorrhage and intracranial dAVF, is crucial for the effective management of these conditions. It is also prudent to recognize the imaging spectrum of metabolic, infective and autoimmune diseases with rapidly progressing dementia, such as methanol toxicity, central pontine myelinolysis (CPM), delayed post hypoxic leukoencephalopathy (DPHL), HIV, Creutzfeldt-Jakob Disease (CJD), Sjogren's syndrome, multiple sclerosis (MS), radiation necrosis and Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS), which are difficult to treat and often require palliative care. This pictorial review emphasizes various non-Alzheimer’s dementia entities and discusses their imaging highlights.

Teaching Points

• Non Alzheimer’s dementia constitutes a broad spectrum of conditions.

• Neuroimaging plays an important role in differentiating treatable from irreversible dementia.

• Neuroimaging is often non-specific in early stages of neurodegenerative conditions with dementia.

• Neuroimaging plays an important role in the multimodal approach towards management of dementia.

Differentiating multiple-system atrophy from Parkinson's disease

The purpose of this review is to illustrate the differentiating features of multiple-system atrophy from Parkinson's disease at MRI. The various MRI sequences helpful in the differentiation will be discussed, including newer methods, such as diffusion tensor imaging, MR spectroscopy, and nuclear imaging.

Chemical exchange saturation transfer MR imaging of Parkinson's disease at 3 Tesla

OBJECTIVES

To demonstrate the feasibility of using chemical exchange saturation transfer (CEST) imaging to detect Parkinson's disease (PD) in patients at 3 Tesla.

METHODS

Twenty-seven PD patients (17 men and 10 women; age range, 54-77 years) and 22 age-matched normal controls (13 men and 9 women; age range, 55-73 years) were examined on a 3-Tesla MRI system. Magnetization transfer spectra with 31 different frequency offsets (-6 to 6 ppm) were acquired at two transverse slices of the head, including the basal ganglia and midbrain. One-way analysis of variance tests was used to compare the differences in CEST imaging signals between PD patients and normal controls.

RESULTS

Total CEST signal between the offsets of 0 and 4 ppm in the substantia nigra was significantly lower in PD patients than in normal controls (P = 0.006), which could be associated with the loss of dopaminergic neurons. Protein-based CEST imaging signals at the offset of 3.5 ppm in the globus pallidus, putamen and caudate were significantly increased in PD patients, compared to normal controls (P < 0.001, P = 0.003, P < 0.001, respectively).

CONCLUSIONS

CEST imaging signals could potentially serve as imaging biomarkers to aid in the non-invasive molecular diagnosis of PD.

KEY POINTS

• Total CEST signal in substantia nigra decreased in PD patients • Protein-based CEST signals in basal ganglia increased in PD patients • CEST could assist with the non-invasive molecular diagnosis for PD patients.

A voxel based comparative analysis using magnetization transfer imaging and T1-weighted magnetic resonance imaging in progressive supranuclear palsy

Aims:

In progressive supranuclear palsy (PSP) tissue damage occurs in specific cortical and subcortical regions. Voxel based analysis using T1-weighted images depict quantitative gray matter (GM) atrophy changes. Magnetization transfer (MT) imaging depicts qualitative changes in the brain parenchyma. The purpose of our study was to investigate whether MT imaging could indicate abnormalities in PSP.

Settings and Design:

A total of 10 patients with PSP (9 men and 1 woman) and 8 controls (5 men and 3 women) were studied with T1-weighted magnetic resonance imaging (MRI) and 3DMT imaging. Voxel based analysis of T1-weighted MRI was performed to investigate brain atrophy while MT was used to study qualitative abnormalities in the brain tissue. We used SPM8 to investigate group differences (with two sample t-test) using the GM and white matter (WM) segmented data.

Results:

T1-weighted imaging and MT are equally sensitive to detect changes in GM and WM in PSP. Magnetization transfer ratio images and magnetization-prepared rapid acquisition of gradient echo revealed extensive bilateral volume and qualitative changes in the orbitofrontal, prefrontal cortex and limbic lobe and sub cortical GM. The prefrontal structures involved were the rectal gyrus, medial, inferior frontal gyrus (IFG) and middle frontal gyrus (MFG). The anterior cingulate, cingulate gyrus and lingual gyrus of limbic lobe and subcortical structures such as caudate, thalamus, insula and claustrum were also involved. Cerebellar involvement mainly of anterior lobe was also noted.

Conclusions:

The findings suggest that voxel based MT imaging permits a whole brain unbiased investigation of central nervous system structural integrity in PSP.

A review of the use of magnetic resonance imaging in Parkinson's disease

To date, the most frequently used Parkinson's disease (PD) biomarkers are the brain imaging measures of dopaminergic dysfunction using positron emission tomography and single photon emission computed tomography. However, major advances have occurred in the development of magnetic resonance imaging (MRI) biomarkers for PD in the past decade. Although conventional structural imaging remains normal in PD, advanced techniques have shown changes in the substantia nigra and the cortex. The most well-developed MRI markers in PD include diffusion imaging and iron load using T2/T2* relaxometry techniques. Other quantitative biomarkers such as susceptibility-weighted imaging for iron load, magnetization transfer and ultra-high-field MRI have shown great potential. More sophisticated techniques such as tractography and resting state functional connectivity give access to anatomical and functional connectivity changes in the brain, respectively. Brain perfusion can be assessed using non-contrast-agent techniques such as arterial spin labelling and spectroscopy gives access to metabolites concentrations. However, to date these techniques are not yet fully validated and standardized quantitative metrics for PD are still lacking. This review presents an overview of new structural, perfusion, metabolic and anatomo-functional connectivity biomarkers, their use in PD and their potential applications to improve the clinical diagnosis of Parkinsonian syndromes and the quality of clinical trials.

Neuroimaging of rapidly progressive dementias, part 1: neurodegenerative etiologies

Most dementias begin insidiously, developing slowly and generally occurring in the elderly age group. The so-called rapidly progressive dementias constitute a different, diverse collection of conditions, many of which are reversible or treatable. For this reason, prompt identification and assessment of acute and subacute forms of dementia are critical to effective treatment. Numerous other entities within this category of presenile rapid-onset dementias are untreatable such as the prion-related diseases. Neuroimaging aids in the diagnosis and evaluation of many of these rapidly progressive dementias, which include myriad conditions ranging from variations of more common neurodegenerative dementias, such as Alzheimer disease, dementia with Lewy bodies, and frontotemporal dementia; infectious-related dementias such as acquired immune deficiency syndrome dementia; autoimmune and malignancy-related conditions; to toxic and metabolic forms of encephalopathy. This first of a 2-part review will specifically address the ability of MR imaging and ancillary neuroimaging strategies to support the diagnostic evaluation of rapidly progressive dementias due to neurodegenerative causes.

Nigrostriatal dopamine terminal imaging with dopamine transporter SPECT: an update

This article gives an update on nigrostriatal dopamine terminal imaging, with emphasis on SPECT performed with the presynaptic dopamine transporter (DAT) ligand (123)I-FP-CIT. The paper covers the rational use of this technique in the diagnostic work-up of patients with known or suspected parkinsonian syndromes. In detail, it addresses the impact of the method for the proof or exclusion of neurodegenerative parkinsonism, for its early and preclinical diagnosis, and for the evaluation of disease progression. The importance of normal DAT binding for differentiating symptomatic parkinsonism and relevant tremor syndromes from neurodegeneration is highlighted. Particularly emphasized is the role of DAT SPECT for diagnosing Lewy body dementia and its separation from Alzheimer dementia. Finally, some remarks deal with the economic aspects of the use of these imaging techniques in the clinical setting.

Neuromelanin magnetic resonance imaging in Parkinson's disease and multiple system atrophy

Pigmented neurons in the substantia nigra pars compacta (SNc) and locus coeruleus (LC) show decreased numbers differentially in Parkinson's disease (PD) and multiple system atrophy (MSA). Recent reports have described that fast spin-echo T1-weighted magnetic resonance imaging (MRI) by a 3-tesla machine can visualize neuromelanin-related contrast of the noradrenergic and dopaminergic neurons respectively in the LC and the SNc. Using neuromelanin MRI at 3 T, we investigated possible alterations of these catecholaminergic neurons in 32 PD and 9 MSA patients, and compared the results with those of 23 normal volunteers. The contrast ratio of the LC and SNc was decreased in MSA and PD patients, most prominently in the LC in MSA patients. The contrast ratio of the SNc was correlated with the Hoehn-Yahr stage of PD and the severity of neuroradiological abnormalities in MSA. These results indicate a potential diagnostic value of neuromelanin MRI to distinguish MSA patients from normal and PD patients.

Signal alterations of the basal ganglia in the differential diagnosis of Parkinson's disease: a retrospective case-controlled MRI data bank analysis

BACKGROUND

Based upon the acquainted loss of dopaminergic neurons in the substantia nigra in Parkinson's disease (PD), we hypothesised changes in magnetic resonance imaging signal intensities of the basal ganglia to be useful as an additional technical tool in the diagnostic work-up.

METHODS

Region-of-interest analyses (substantia nigra and globus pallidus internus) of T2-weighted scans were performed in seventy subjects with PD, 170 age- and gender-matched controls and 38 patients with an atypical form of neurodegenerative Parkinsonian syndrome (N = 11 multisystem atrophy, N = 22 progressive supranuclear palsy, N = 5 corticobasal syndrome).

RESULTS

In patients with PD, significant changes in signal intensities within the substantia nigra were observed compared to controls at p < 0.001. For the globus pallidus internus, signal alterations in PD and progressive supranuclear palsy were found to be significant (p < 0.001) if compared to controls. Furthermore, signal changes of substantia nigra correlated with signal intensities of globus pallidus internus in the ipsilateral hemisphere in both groups. Sensitivity was 86% and specificity was 90% for the combined analysis of substantia nigra and globus pallidus internus in the complete patient sample versus controls.

CONCLUSIONS

Signal alterations of substantia nigra and globus pallidus internus in routine magnetic resonance imaging were useful to distinguish patients with PD from controls. In addition, signal changes in globus pallidus internus could be used to differentiate progressive supranuclear palsy patients from controls. These analyses have the potential to serve as an additional non-invasive technical tool to support the individual differential diagnosis of PD.

Progressive supranuclear palsy: high-field-strength MR microscopy in the human substantia nigra and globus pallidus

PURPOSE

To characterize changes in the magnetic resonance (MR) relaxation properties of progressive supranuclear palsy (PSP) and tissue from neurologically normal brains by using high-resolution (21.1-T, 900-MHz) MR microscopy of postmortem human midbrain and basal ganglia.

MATERIALS AND METHODS

This HIPAA-compliant study was approved by the institutional review board at the Mayo Clinic and informed consent was obtained. Postmortem tissue from age-matched PSP (n = 6) and control (n = 3) brains was imaged by using three-dimensional fast low-angle shot MR imaging with isotropic resolution of 50 μm. Relaxation times and parametric relaxation maps were generated from spin-echo and gradient-recalled-echo sequences. MR findings were correlated with histologic features by evaluating the presence of iron by using Prussian blue and ferritin and microglia burden as determined by a custom-designed color deconvolution algorithm. T2 and T2*, signal intensities, percent pixels (that could not be fitted in a pixel-by-pixel regression analysis due to severe hypointensity), and histologic data (total iron, ferritin, and microglia burden) were statistically analyzed by using independent sample t tests (P < .05).

RESULTS

PSP specimens showed higher iron burden in the cerebral peduncles and substantia nigra than did controls. However, only the putamen was significantly different, and it correlated with a decrease of T2* compared with controls (-48%; P = .043). Similarly, substantia nigra showed a significant decrease of T2* signal in PSP compared with controls (-57%; P = .028). Compared with controls, cerebral peduncles showed increased T2 (38%; P = .026) and T2* (34%; P = .014), as well as higher T2 signal intensity (57%; P = .049). Ferritin immunoreactivity was the opposite from iron burden and was significantly lower compared with controls in the putamen (-74%; P = .025), red nucleus (-61%; P = .018), and entire basal ganglia section (-63%; P = .016).

CONCLUSION

High-field-strength MR microscopy yielded pronounced differences in substantia nigra and globus pallidus of PSP compared with control brains. Histologic data also suggested that the predominant iron in PSP is hemosiderin, not ferritin. Iron in the brain is a contrast enhancer and potential biomarker for PSP.

Magnetic resonance imaging of the substantia nigra in Parkinson's disease

Until recently, conventional magnetic resonance imaging (MRI) was most often negative in Parkinson's disease or showed nonspecific findings. Recent developments in structural MRI, including relaxometry, magnetization transfer, and neuromelanin imaging, have demonstrated improved contrast and enabled more accurate visualization of deep brain nuclei, in particular, the substantia nigra. Meanwhile, diffusion imaging has provided useful biomarkers of substantia nigra degeneration, showing reduced anisotropy and anatomical connectivity with the striatum and thalamus. These advances in structural imaging are complemented by findings of magnetic resonance spectroscopy on brain metabolism and resting-state functional MRI on functional connectivity. This article presents an overview of these new structural, metabolic, and resting-state functional MRI techniques and their implications for Parkinson's disease. The techniques are reviewed in the context of their potential for better understanding the disease in terms of diagnosis and pathophysiology and as biomarkers of its progression.

The neuropathology, pathophysiology and genetics of multiple system atrophy

Multiple system atrophy (MSA) is an unrelenting, sporadic, adult-onset, neurodegenerative disease of unknown aetiology. Its clinically progressive course is characterized by a variable combination of parkinsonism, cerebellar ataxia and/or autonomic dysfunction. Neuropathological examination often reveals gross abnormalities of the striatonigral and/or olivopontocerebellar systems, which upon microscopic examination are associated with severe neuronal loss, gliosis, myelin pallor and axonal degeneration. MSA is a member of a diverse group of neurodegenerative disorders termed α-synucleinopathies, due to the presence of abnormal α-synuclein positive cytoplasmic inclusions in oligodendrocytes, termed glial cytoplasmic inclusions. These are the hallmark neuropathological lesion of MSA and are thought to play a central role in the pathogenesis of the disease. In this review, neuropathological features of MSA are described in detail, along with recent advances in the pathophysiology and genetics of the disease. Our current knowledge of the expression and accumulation of α-synuclein, and efforts to model the disease in vitro and in vivo, are emphasized in this paper and have helped formulate a working hypothesis for the pathogenesis of MSA.

Diffusion tensor MRI contributes to differentiate Richardson's syndrome from PSP-parkinsonism

This study investigated the regional distribution of white matter (WM) damage in Richardson's syndrome (PSP-RS) and progressive supranuclear palsy-Parkinsonism (PSP-P) using diffusion tensor (DT) magnetic resonance imaging (MRI). The DT MRI classificatory ability in diagnosing progressive supranuclear palsy (PSP) syndromes, when used in combination with infratentorial volumetry, was also quantified. In 37 PSP (21 PSP-RS, 16 PSP-P) and 42 controls, the program Tract-Based Spatial Statistics (TBSS; www.fmrib.ox.ac.uk/fsl/tbss) was applied. DT MRI metrics were derived from supratentorial, thalamic, and infratentorial tracts. The magnetic resonance parkinsonism index (MRPI) was calculated. All PSP harbored diffusivity abnormalities in the corpus callosum, frontoparietal, and frontotemporo-occipital tracts. Infratentorial WM and thalamic radiations were severely affected in PSP-RS and relatively spared in PSP-P. When MRPI and DT MRI measures were combined, the discriminatory power increased for each comparison. Distinct patterns of WM alterations occur in PSP-RS and PSP-P. Adding DT MRI measures to MRPI improves the diagnostic accuracy in differentiating each PSP syndrome from healthy individuals and each other.

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.