Voxelwise meta-analysis of white matter abnormalities in progressive supranuclear palsy

Structural correlates of survival in progressive supranuclear palsy

INTRODUCTION

Many studies of the Richardson's syndrome phenotype of progressive supranuclear palsy (PSP) have elucidated regions of progressive atrophy and neural correlates of clinical severity. However, the neural correlates of survival and how these differ according to variant phenotypes are poorly understood. We set out to identify structural changes that predict severity and survival from scanning date to death.

METHODS

Structural magnetic resonance imaging data from 112 deceased people with clinically defined 'probable' or 'possible' PSP were analysed. Neuroanatomical regions of interest volumes, thickness and area were correlated with 'temporal stage', defined as the ratio of time from symptom onset to death, time from scan to death ('survival from scan'), and in a subset of patients, clinical severity, adjusting for age and total intracranial volume. Forty-nine participants had post mortem confirmation of the diagnosis.

RESULTS

Using T1-weighted magnetic resonance imaging, we confirmed the midbrain, and bilateral cortical structural correlates of contemporary disease severity. Atrophy of the striatum, cerebellum and frontotemporal cortex correlate with temporal stage and survival from scan, even after adjusting for severity. Subcortical structure-survival relationships were stronger in Richardson's syndrome than variant phenotypes.

CONCLUSIONS

Although the duration of PSP varies widely between people, an individual's progress from disease onset to death (their temporal stage) reflects atrophy in striatal, cerebellar and frontotemporal cortical regions. Our findings suggest magnetic resonance imaging may contribute to prognostication and stratification of patients with heterogenous clinical trajectories and clarify the processes that confer mortality risk in PSP.

Phonemic fluency quantity and quality: Comparing patients with PSP, Parkinson's disease and focal frontal and subcortical lesions

Progressive supranuclear palsy (PSP) can be difficult to distinguish from Parkinson's disease (PD), but has a much graver prognosis. PSP is characterised severely reduced output on measures of phonemic fluency, suggesting that it may be a specific marker of PSP. However, reduced phonemic fluency has also been noted in PD, and very few studies have actually compared phonemic fluency in PSP and PD. Although anecdotal reports suggest that phonemic fluency output in PSP may have specific characteristics, with more low-frequency words and perseverative errors, no study to date has formally explored this. Further investigation into phonemic fluency output and its cognitive and neuroanatomical correlates is now critical for improving our understanding of the verbal fluency in PSP. In this study, we compared phonemic fluency characteristics (including quantity, frequency and error rates) in patients with PSP, PD and focal frontal or subcortical lesions, and age- and education-matched healthy controls. We then compared these characteristics with performance on extensive neuropsychological testing. We found that PSP patients generated significantly fewer words than patients with PD and patients with right frontal focal lesions, and healthy controls. Phonemic fluency was also significantly reduced in patients with left frontal and subcortical focal lesions. However, there were no significant group differences in word frequency or error rates. Phonemic fluency was best predicted by performance on the Vocabulary and Hayling neuropsychological tests. We argue that these findings provide important evidence that reduced phonemic fluency is a hallmark of PSP and argue that the specificity of this impairment betrays an underlying impairment in energization, reflecting dysfunction of left frontal and subcortical networks.

In vivo binding of a tau imaging probe, [11 C]PBB3, in patients with progressive supranuclear palsy

Background

[¹¹C]pyridinyl‐butadienyl‐benzothiazole 3 is a PET imaging agent designed for capturing pathological tau aggregates in diverse neurodegenerative disorders, and would be of clinical utility for neuropathological investigations of PSP.

Objectives

To explore the usefulness of [¹¹C]pyridinyl‐butadienyl‐benzothiazole 3/PET in assessing characteristic distributions of tau pathologies and their association with clinical symptoms in the brains of living PSP patients.

Methods

We assessed 13 PSP patients and 13 age‐matched healthy control subjects. Individuals negative for amyloid β PET with [¹¹C]Pittsburgh compound B underwent clinical scoring, MR scans, and [¹¹C]pyridinyl‐butadienyl‐benzothiazole 3/PET.

Results

There were significant differences in binding potential for [¹¹C]pyridinyl‐butadienyl‐benzothiazole 3 between PSP patients and healthy control subjects (P = 0.02). PSP patients exhibited greater radioligand retention than healthy control subjects in multiple brain regions, including frontoparietal white matter, parietal gray matter, globus pallidus, STN, red nucleus, and cerebellar dentate nucleus. [¹¹C]pyridinyl‐butadienyl‐benzothiazole 3 deposition in frontoparietal white matter, but not gray matter, was correlated with general severity of parkinsonian and PSP symptoms, whereas both gray matter and white matter [¹¹C]pyridinyl‐butadienyl‐benzothiazole 3 accumulations in the frontoparietal cortices were associated with nonverbal cognitive impairments. Autoradiographic and fluorescence labeling with pyridinyl‐butadienyl‐benzothiazole 3 was observed in gray matter and white matter of PSP motor cortex tissues.

Conclusions

Our findings support the in vivo detectability of tau fibrils characteristic of PSP by [¹¹C]pyridinyl‐butadienyl‐benzothiazole 3/PET, and imply distinct and synergistic contributions of gray matter and white matte tau pathologies to clinical symptoms. [¹¹C]pyridinyl‐butadienyl‐benzothiazole 3/PET potentially provides a neuroimaging‐based index for the evolution of PSP tau pathologies promoting the deterioration of motor and cognitive functions. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Atrophy in midbrain & cerebral/cerebellar pedunculi is characteristic for progressive supranuclear palsy - A double-validation whole-brain meta-analysis

OBJECTIVE

Progressive supranuclear palsy (PSP) is an atypical parkinsonian syndrome characterized by vertical gaze palsy and postural instability. Midbrain atrophy is suggested as a hallmark, but it has not been validated systematically in whole-brain imaging.

METHODS

We conducted whole-brain meta-analyses identifying disease-related atrophy in structural MRI. Eighteen studies were identified (N = 315 PSP, 393 controls) and separated into gray or white matter analyses (15/12). All patients were diagnosed according to the National Institute of Neurological Disorders and Stroke and the Society for PSP (NINDS-SPSP criteria, Litvan et al. (1996a)), which are now considered as PSP-Richardson syndrome (Höglinger et al., 2017). With overlay analyses, we double-validated two meta-analytical algorithms: anatomical likelihood estimation and seed-based D mapping. Additionally, we conducted region-of-interest effect size meta-analyses on radiological biomarkers and subtraction analyses differentiating PSP from Parkinson's disease.

RESULTS

Whole brain meta-analyses revealed consistent gray matter atrophy in bilateral thalamus, anterior insulae, midbrain, and left caudate nucleus. White matter alterations were consistently detected in bilateral superior/middle cerebellar pedunculi, cerebral pedunculi, and midbrain atrophy. Region-of-interest meta-analyses demonstrated that midbrain metrics generally perform very well in distinguishing PSP from other parkinsonian syndromes with strong effect sizes. Subtraction analyses identified the midbrain as differentiating between PSP and Parkinson's disease.

CONCLUSIONS

Our meta-analyses identify gray matter atrophy of the midbrain and white matter atrophy of the cerebral/cerebellar pedunculi and midbrain as characteristic for PSP. Results support the incorporation of structural MRI data, and particularly these structures, into the revised PSP diagnostic criteria.

Voxel-based meta-analysis of gray and white matter volume abnormalities in spinocerebellar ataxia type 2

OBJECTIVE

To identify the consistent findings from the whole-brain voxel-based morphometry (VBM) studies on spinocerebellar ataxia type 2 (SCA2).

METHODS

The whole-brain VBM studies comparing SCA2 patients and healthy controls (HCs) were systematically searched in PubMed, Embase databases from January 2000 to June 2017. The coordinates with significant differences in gray matter (GM) and white matter (WM) between SCA2 patients and HCs were extracted separately from each cluster. A meta-analysis was performed using anisotropic effect size-based signed differential mapping (AES-SDM) software.

RESULTS

A total of five studies with 65 SCA2 patients and 124 HCs were included in the GM meta-analysis. Four of the five studies with 50 SCA2 patients and 109 HCs were included in the WM meta-analysis. Significant and consistent GM volume reductions were detected in bilateral cerebellar hemispheres, cerebellar vermis, the right fusiform gyrus, the right parahippocampal gyrus, and the right lingual gyrus. The WM volume reductions were observed in bilateral cerebellar hemispheres, cerebellar vermis, middle cerebellar peduncles, pons, and bilateral cortico-spinal projections. The findings of the study remained largely unchanged in jackknife sensitivity analysis.

CONCLUSIONS

The consistent findings from our meta-analysis showed that GM volume reductions in SCA2 patients were not limited in cerebellum while significant WM volume reductions widely existed in cerebellum and pyramidal system. The findings provide morphological basis for further studies on SCA2.

Repeatability of Brain Volume Measurements Made with the Atlas-based Method from T1-weighted Images Acquired Using a 0.4 Tesla Low Field MR Scanner

PURPOSE

An understanding of the repeatability of measured results is important for both the atlas-based and voxel-based morphometry (VBM) methods of magnetic resonance (MR) brain volumetry. However, many recent studies that have investigated the repeatability of brain volume measurements have been performed using static magnetic fields of 1-4 tesla, and no study has used a low-strength static magnetic field. The aim of this study was to investigate the repeatability of measured volumes using the atlas-based method and a low-strength static magnetic field (0.4 tesla).

MATERIALS AND METHODS

Ten healthy volunteers participated in this study. Using a 0.4 tesla magnetic resonance imaging (MRI) scanner and a quadrature head coil, three-dimensional T1-weighted images (3D-T1WIs) were obtained from each subject, twice on the same day. VBM8 software was used to construct segmented normalized images [gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) images]. The regions-of-interest (ROIs) of GM, WM, CSF, hippocampus (HC), orbital gyrus (OG), and cerebellum posterior lobe (CPL) were generated using WFU PickAtlas. The percentage change was defined as[100 × (measured volume with first segmented image - mean volume in each subject)/(mean volume in each subject)]The average percentage change was calculated as the percentage change in the 6 ROIs of the 10 subjects.

RESULTS

The mean of the average percentage changes for each ROI was as follows: GM, 0.556%; WM, 0.324%; CSF, 0.573%; HC, 0.645%; OG, 1.74%; and CPL, 0.471%. The average percentage change was higher for the orbital gyrus than for the other ROIs.

CONCLUSION

We consider that repeatability of the atlas-based method is similar between 0.4 and 1.5 tesla MR scanners. To our knowledge, this is the first report to show that the level of repeatability with a 0.4 tesla MR scanner is adequate for the estimation of brain volume change by the atlas-based method.

The utility of neuroimaging in the differential diagnosis of parkinsonian syndromes

The differential diagnosis of parkinsonian syndromes can be challenging, particularly in early disease stages. However, prognosis and therapeutic regimes are not alike in Parkinson disease and atypical parkinsonism, and thus a correct diagnosis at the earliest possible stage is desirable. Over the past two decades, magnetic resonance imaging and radiotracer-based imaging techniques have proven to be helpful tools to enhance the accuracy of clinical diagnosis in these disorders. Here, we review recent advances in neuroimaging for the differential diagnosis of parkinsonian syndromes.