Pathological, clinical and genetic heterogeneity in progressive supranuclear palsy

Genotype-Phenotype Correlation in Progressive Supranuclear Palsy Syndromes: Clinical and Radiological Similarities and Specificities

The progressive supranuclear palsy (PSP) syndrome encompasses different entities. PSP disease of sporadic origin is the most frequent presentation, but different genetic mutations can lead either to monogenic variants of PSP disease, or to other conditions with a different pathophysiology that eventually may result in PSP phenotype. PSP syndrome of monogenic origin is poorly understood due to the low prevalence and variable expressivity of some mutations. Through this review, we describe how early age of onset, family history of early dementia, parkinsonism, dystonia, or motor neuron disease among other clinical features, as well as some neuroimaging signatures, may be the important clues to suspect PSP syndrome of monogenic origin. In addition, a diagnostic algorithm is proposed that may be useful to guide the genetic diagnosis once there is clinical suspicion of a monogenic PSP syndrome.

The Progressive Supranuclear Palsy: Past and Present Aspects

Objectives: Recently, new criteria for sensitive and specific clinical diagnosis of progressive supranuclear palsy (PSP) have been addressed while distinct clinical phenotypes of the disorder have been increasingly described in the literature. This study aimed to describe past and present aspects of the disease as well as to highlight the cognitive and behavioral profile of PSP patients in relation to the underlying pathology, genetics and treatment procedures.Methods: A Medline and Scopus search was performed to identify articles published on this topic. Articles published solely in English were considered.Results: The most common clinical characteristics of PSP included early postural instability and falls, vertical supranuclear gaze palsy, parkinsonism with poor response to levodopa and pseudobulbar palsy. Frontal dysfunction and verbal fluency deficits were the most distinct cognitive impairments in PSP while memory, visuospatial and social cognition could also be affected. Apathy and impulsivity were also present in PSP patients and had significant impact on relatives and caregivers.Conclusions: PSP is a neurodegenerative disorder with prominent tau neuropathology. Movement, motivation and communication impairments in patients with PSP may limit participation in everyday living activities. Comprehensive neuropsychological assessments are of significant importance for PSP cognitive evaluation. Pharmacologic and non-pharmacologic approaches could be applied in order to relieve patients and improve quality of life.Clinical Implications: Executive dysfunction is the most notable cognitive impairment and dominates the neuropsychological profile of patients with PSP.

Sensitivity and Specificity of Diagnostic Criteria for Progressive Supranuclear Palsy

BACKGROUND

In 2017, the International Parkinson and Movement Disorder Society put forward new clinical criteria for the diagnosis of PSP, recognizing diverse PSP phenotypes. In this study, we compared the sensitivity and specificity of the new criteria with the National Institutes of Neurological Disease and Society for Progressive Supranuclear Palsy criteria at different times.

METHODS

Patients with clinical parkinsonism, clinical and/or neuropathological diagnosis of PSP, were identified from the Society for Progressive Supranuclear Palsy brain bank. All patients had neuropathologic diagnoses and detailed clinical examination performed by a neurologist at 1 of the 3 Mayo Clinic sites, in Florida, Arizona, and Minnesota. Clinical symptoms and signs were abstracted retrospectively in a blinded fashion and used to determine whether patients met either diagnostic criterion. Patients were divided into early and late disease stage groups using a 3-year cutoff.

RESULTS

A total of 129 patients were included, of whom 66 had PSP pathology (51%). The remainder had other neurodegenerative diseases. The overall sensitivity of the International Parkinson and Movement Disorder Society criteria was 87.9%, compared with 45.5% for the National Institutes of Neurological Disease and Society for Progressive Supranuclear Palsy criteria, whereas the specificity of the International Parkinson and Movement Disorder Society probable PSP criteria was 85.7%, compared with 90.5% for the National Institutes of Neurological Disease and Society for Progressive Supranuclear Palsy. Individual patients were noted to have features of multiple PSP phenotypes.

CONCLUSION

The International Parkinson and Movement Disorder Society criteria recognize several phenotypes of progressive supranuclear palsy and hence have higher sensitivity than the previous criteria. © 2019 International Parkinson and Movement Disorder Society.

Utility of the Movement Disorders Society Criteria for Progressive Supranuclear Palsy in Clinical Practice

Objectives

When the 2017 Movement Disorders Society Criteria for progressive supranuclear palsy is applied, patients may appear to have multiple phenotypes. The maximum allocation extinction rules were developed to provide a consistent method for applying the criteria and reaching a single diagnostic label. In this study, we apply both to a neuropathologic cohort of progressive supranuclear palsy and other parkinsonian conditions.

Methods

An autopsy cohort of 54 patients with progressive supranuclear palsy and 56 patients with other neuropathologic diseases was selected. Clinical data were retrospectively abstracted, and the diagnostic criteria for progressive supranuclear palsy were applied. All possible phenotypes applicable were listed and maximum allocation extinction rules were applied to assess reduction in the number of phenotypes ascribed per patient.

Results

In the progressive supranuclear palsy group, 52 patients met the criteria for multiple phenotypes, with an average of 7 phenotypes per patient. In the nonprogressive supranuclear palsy group, all 56 patients had features of more than one phenotype, up to 3 per patient. After application of maximum allocation extinction rules, the majority of the patients in both groups had a single predominant phenotype. Freezing of gait, supranuclear gaze palsy, and frontal behavioral syndrome were more common in the progressive supranuclear palsy group.

Conclusions

The diagnostic criteria for progressive supranuclear palsy identify many clinical features, thereby leading to assignment of multiple phenotypes per patient. We demonstrate that the maximum allocation extinction rules can effectively lead to a single consensus phenotype, maintaining a uniform diagnostic label for clinical and research applications.

Clinical heterogeneity of frontotemporal dementia and Parkinsonism linked to chromosome 17 caused by MAPT N279K mutation in relation to tau positron emission tomography features

BACKGROUND

While mechanistic links between tau abnormalities and neurodegeneration have been proven in frontotemporal dementia and parkinsonism linked to chromosome 17 caused by MAPT mutations, variability of the tau pathogenesis and its relation to clinical progressions in the same MAPT mutation carriers are yet to be clarified.

OBJECTIVES

The present study aimed to analyze clinical profiles, tau accumulations, and their correlations in 3 kindreds with frontotemporal dementia and parkinsonism linked to chromosome 17 attributed to the MAPT N279K mutation.

METHODS

Four patients with N279K mutant frontotemporal dementia and parkinsonism linked to chromosome 17/MAPT underwent [¹¹ C]PBB3-PET to estimate regional tau loads.

RESULTS

Haplotype assays revealed that these kindreds originated from a single founder. Despite homogeneity of the disease-causing MAPT allele, clinical progression was more rapid in 2 kindreds than in the other. The kindred with slow progression showed mild tau depositions, mostly confined to the midbrain and medial temporal areas. In contrast, kindreds with rapid progression showed profoundly increased [¹¹ C]PBB3 binding in widespread regions from an early disease stage.

CONCLUSIONS

[¹¹ C]PBB3-PET can capture four-repeat tau pathologies characteristic of N279K mutant frontotemporal dementia and parkinsonism linked to chromosome 17/MAPT. Our findings indicate that, in addition to the mutated MAPT allele, genetic and/or epigenetic modifiers of tau pathologies lead to heterogeneous clinicopathological features. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Variation at the TRIM11 locus modifies progressive supranuclear palsy phenotype

Objective

The basis for clinical variation related to underlying progressive supranuclear palsy (PSP) pathology is unknown. We performed a genome‐wide association study (GWAS) to identify genetic determinants of PSP phenotype.

Methods

Two independent pathological and clinically diagnosed PSP cohorts were genotyped and phenotyped to create Richardson syndrome (RS) and non‐RS groups. We carried out separate logistic regression GWASs to compare RS and non‐RS groups and then combined datasets to carry out a whole cohort analysis (RS = 367, non‐RS = 130). We validated our findings in a third cohort by referring to data from 100 deeply phenotyped cases from a recent GWAS. We assessed the expression/coexpression patterns of our identified genes and used our data to carry out gene‐based association testing.

Results

Our lead single nucleotide polymorphism (SNP), rs564309, showed an association signal in both cohorts, reaching genome‐wide significance in our whole cohort analysis (odds ratio = 5.5, 95% confidence interval = 3.2–10.0, p = 1.7 × 10⁻⁹). rs564309 is an intronic variant of the tripartite motif‐containing protein 11 (TRIM11) gene, a component of the ubiquitin proteasome system (UPS). In our third cohort, minor allele frequencies of surrogate SNPs in high linkage disequilibrium with rs564309 replicated our findings. Gene‐based association testing confirmed an association signal at TRIM11. We found that TRIM11 is predominantly expressed neuronally, in the cerebellum and basal ganglia.

Interpretation

Our study suggests that the TRIM11 locus is a genetic modifier of PSP phenotype and potentially adds further evidence for the UPS having a key role in tau pathology, therefore representing a target for disease‐modifying therapies. Ann Neurol 2018;84:485–496

Characterisation of tau in the human and rodent enteric nervous system under physiological conditions and in tauopathy

Tau is normally a highly soluble phosphoprotein found predominantly in neurons. Six different isoforms of tau are expressed in the adult human CNS. Under pathological conditions, phosphorylated tau aggregates are a defining feature of neurodegenerative disorders called tauopathies. Recent findings have suggested a potential role of the gut-brain axis in CNS homeostasis, and therefore we set out to examine the isoform profile and phosphorylation state of tau in the enteric nervous system (ENS) under physiological conditions and in tauopathies. Surgical specimens of human colon from controls, Parkinson's disease (PD) and progressive supranuclear palsy (PSP) patients were analyzed by Western Blot and immunohistochemistry using a panel of anti-tau antibodies. We found that adult human ENS primarily expresses two tau isoforms, localized in the cell bodies and neuronal processes. We did not observe any difference in the enteric tau isoform profile and phosphorylation state between PSP, PD and control subjects. The htau mouse model of tauopathy also expressed two main isoforms of human tau in the ENS, and there were no apparent differences in ENS tau localization or phosphorylation between wild-type and htau mice. Tau in both human and mouse ENS was found to be phosphorylated but poorly susceptible to dephosphorylation with lambda phosphatase. To investigate ENS tau phosphorylation further, primary cultures from rat enteric neurons, which express four isoforms of tau, were pharmacologically manipulated to show that ENS tau phosphorylation state can be regulated, at least in vitro. Our study is the first to characterize tau in the rodent and human ENS. As a whole, our findings provide a basis to unravel the functions of tau in the ENS and to further investigate the possibility of pathological changes in enteric neuropathies and tauopathies.

Microtubule defects in mesenchymal stromal cells distinguish patients with Progressive Supranuclear Palsy

Progressive Supranuclear Palsy (PSP) is a rare neurodegenerative disease whose etiopathogenesis remains elusive. The intraneuronal accumulation of hyperphosphorylated Tau, a pivotal protein in regulating microtubules (MT), leads to include PSP into tauopathies. Pathological hallmarks are well known in neural cells but no word yet if PSP‐linked dysfunctions occur also in other cell types. We focused on bone marrow mesenchymal stromal cells (MSCs) that have recently gained attention for therapeutic interventions due to their anti‐inflammatory, antiapoptotic and trophic properties. Here, we aimed to investigate MSCs biology and to disclose if any disease‐linked defect occurs in this non‐neuronal compartment. First, we found that cells obtained from patients showed altered morphology and growth. Next, Western blotting analysis unravelled the imbalance in α‐tubulin post‐translational modifications and in MT stability. Interestingly, MT mass is significantly decreased in patient cells at baseline and differently changes overtime compared to controls, suggesting their inability to efficiently remodel MT cytoskeleton during ageing in culture. Thus, our results provide the first evidence that defects in MT regulation and stability occur and are detectable in a non‐neuronal compartment in patients with PSP. We suggest that MSCs could be a novel model system for unravelling cellular processes implicated in this neurodegenerative disorder.

Obsessive compulsive personality disorder in Progressive Supranuclear Palsy, Multiple System Atrophy and Essential Tremor

INTRODUCTION

aim of the study was to evaluate the presence of the Obsessive Compulsive Personality Disorder (OCPeD) in Multiple System Atrophy (MSA), Progressive Supranuclear Palsy (PSP) and Essential Tremor (ET) and in a group of healthy subjects.

METHODS

patients affected by MSA, PSP and ET diagnosed according to currently accepted diagnostic criteria and a group of healthy controls were enrolled in the study. Patients with cognitive impairment were excluded from the study. The Structured Clinical Interview for Personality Disorders-II (SCID-II) has been performed to evaluate the presence of personality disorders (PeDs). The diagnosis of OCPeD was confirmed by a psychiatric interview.

RESULTS

fifteen MSA patients (8 men and 7 women; aged 62.9 ± 7.6 years), 14 PSP patients (8 men and 6 women; aged 69.8 ± 4.4 years), 16 ET patients (10 men and 6 women; aged 70.4 ± 6.4 years) and 20 healthy subjects (10 men and 10 women; aged 65.5 ± 6.0 years) were enrolled. OCPeD was recorded in 5 (35.7%) PSP patients, 2 (13.3%) MSA patients, 2 (12.5%) ET patient and 2 (10%) controls.

CONCLUSION

a low frequency of OCPeD, close to those recorded in healthy subjects, was recorded in both MSA and ET patients. Conversely an higher frequency of OCPeD, similar to PD was found among PSP patients, supporting the possibility of an impairment of common basal ganglia network possibly involving the orbito-frontal circuits.

Diagnostic potential of automated subcortical volume segmentation in atypical parkinsonism

OBJECTIVE

To determine whether automated and observer-independent volumetric MRI analysis is able to discriminate among patients with Parkinson disease (PD), multiple system atrophy (MSA), and progressive supranuclear palsy (PSP) in early to moderately advanced stages of disease.

METHODS

T1-weighted volumetric MRI from patients with clinically probable PD (n = 40), MSA (n = 40), and PSP (n = 30) and a mean disease duration of 2.8 ± 1.7 y were examined using automated volume measures of 22 subcortical regions. The clinical follow-up period was 2.5 ± 1.2 years. The data were split into a training (n = 72) and a test set (n = 38). The training set was used to build a C4.5 decision tree model in order to classify patients as MSA, PSP, or PD. The classification algorithm was examined by the test set using the final clinical diagnosis at last follow-up as diagnostic gold standard.

RESULTS

The midbrain and putaminal volume as well as the cerebellar gray matter compartment were identified as the most significant brain regions to construct a prediction model. The diagnostic accuracy for PD vs MSA or PSP was 97.4%. In contrast, diagnostic accuracy based on validated clinical consensus criteria at the time of MRI acquisition was 62.9%.

CONCLUSIONS

Volume segmentation of subcortical brain areas differentiates PD from MSA and PSP and improves diagnostic accuracy in patients presenting with early to moderately advanced stage parkinsonism.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that automated MRI analysis accurately discriminates among early-stage PD, MSA, and PSP.

The phenotypic spectrum of progressive supranuclear palsy: a retrospective multicenter study of 100 definite cases

The phenotypic variability of progressive supranuclear palsy (PSP) may account for its frequent misdiagnosis, in particular in early stages of the disease. However, large multicenter studies to define the frequency and natural history of PSP phenotypes are missing. In a cohort of 100 autopsy-confirmed patients we studied the phenotypic spectrum of PSP by retrospective chart review. Patients were derived from five brain banks with expertise in neurodegenerative disorders with referrals from multiple academic hospitals. The clinical characteristics of the 100 cases showed remarkable heterogeneity. Most strikingly, only 24% of cases presented as Richardson's Syndrome (RS), and more than half of the cases either showed overlapping features of several predescribed phenotypes, or features not fitting proposed classification criteria for PSP phenotypes. Classification of patients according to predominant clinical features in the first 2 years of the disease course allowed a more comprehensive description of the phenotypic spectrum. These predominance types differed significantly with regard to survival time and frequency of cognitive deficits. In summary, the phenotypic spectrum of PSP may be broader and more variable than previously described in single-center studies. Thus, too strict clinical criteria defining distinct phenotypes may not reflect this variability. A more pragmatic clinical approach using predominance types could potentially be more helpful in the early recognition of and for making prognostic predictions for these patients. Given the limitations arising from the retrospective nature of this analysis, a systematic validation in a prospective cohort study is imperative.

Clinical outcomes of two main variants of progressive supranuclear palsy and multiple system atrophy: a prospective natural history study

Progressive supranuclear palsy (PSP) and parkinsonian subtype of multiple system atrophy (MSA-P) are, after Parkinson's disease (PD), the most common forms of neurodegenerative parkinsonism. Clinical heterogeneity of PSP includes two main variants, Richardson syndrome (PSP-RS) and PSP-parkinsonism (PSP-P). Clinical differentiation between them may be impossible at least during the first 2 years of the disease. Little is known about the differences in natural course of PSP-RS and PSP-P and, therefore, in this study we prospectively followed the clinical outcomes of consecutive, pathologically unconfirmed patients with the clinical diagnoses of PSP-RS (51 patients), PSP-P (21 patients) and MSA-P (49 patients). Estimated mean survival time was 11.2 years for PSP-P, 6.8 years for PSP-RS, and 7.9 years for MSA-P, where a 5-year survival probabilities were 90, 66 and 78 %, respectively. More disabling course of PSP-RS compared to PSP-P was also highlighted through the higher number of milestones reached in the first 3 years of the disease, as well as in the trend to reach all clinical milestones earlier. We found that PSP-P variant had a more favorable course with longer survival, not only when compared to PSP-RS, but also when compared to another form of atypical parkinsonism, MSA-P.

Differentiation of progressive supranuclear palsy: clinical, imaging and laboratory tools

Progressive supranuclear palsy (PSP) is the most common atypical parkinsonian syndrome comprising two main clinical subtypes: Richardson's syndrome (RS), characterized by prominent postural instability, supranuclear vertical gaze palsy and frontal dysfunction; and PSP-parkinsonism (PSP-P) which is characterized by an asymmetric onset, tremor and moderate initial therapeutic response to levodopa. The early clinical features of PSP-P are often difficult to discern from idiopathic Parkinson's disease (PD), and other atypical parkinsonian disorders, including multiple system atrophy (MSA) and corticobasal syndrome (CBS). In addition, rare PSP subtypes may be overlooked or misdiagnosed if there are atypical features present. The differentiation between atypical parkinsonian disorders and PD is important because the prognoses are different, and there are different responses to therapy. Structural and functional imaging, although currently of limited diagnostic value for individual use in early disease, may contribute valuable information in the differential diagnosis of PSP. A growing body of evidence shows the importance of CSF biomarkers in distinguishing between atypical parkinsonian disorders particularly early in their course when disease-modifying therapies are becoming available. However, specific diagnostic CSF biomarkers have yet to be identified. In the absence of reliable disease-specific markers, we provide an update of the recent literature on the assessment of clinical symptoms, pathology, neuroimaging and biofluid markers that might help to distinguish between these overlapping conditions early in the course of the disease.

Saccade abnormalities in autopsy-confirmed frontotemporal lobar degeneration and Alzheimer disease

BACKGROUND

Deficits in the generation and control of saccades have been described in clinically defined frontotemporal dementia (FTD) and Alzheimer disease (AD).

OBJECTIVE

To determine the saccade abnormalities associated with autopsy-defined cases of frontotemporal lobar degeneration (FTLD) and of AD, because clinical FTD syndromes can correspond to a number of different underlying neuropathologic FTD and non-FTD diagnoses.

DESIGN

An infrared eye tracker was used to record visually guided saccades to 10° targets and antisaccades in subjects with autopsy-confirmed FTD and subjects with autopsy-confirmed AD, a mean (SE) of 35.6 (10.0) months prior to death, and age-matched normal controls. Twelve subjects with FTD had an FTLD-TAR DNA-binding protein 43 pathology, 15 had an FTLD-tau pathology, and 1 subject showed an FTLD-fused in sarcoma protein pathology. Receiver operating curve statistics were used to determine the diagnostic value of the oculomotor variables. Neuroanatomical correlates of oculomotor abnormalities were investigated using voxel-based morphometry.

SETTING

Memory and Aging Center, Department of Neurology, University of California, San Francisco.

PARTICIPANTS

A total of 28 subjects with autopsy-confirmed FTD, 10 subjects with autopsy-confirmed AD, and 27 age-matched normal controls.

RESULTS

All subjects with FTD or AD were impaired relative to normal controls on the antisaccade task. However, only FTLD-tau and AD cases displayed reflexive visually guided saccade abnormalities. The AD cases displayed prominent increases in horizontal saccade latency that differentiated them from the FTD cases. Impairments in velocity and gain were most severe in individuals with progressive supranuclear palsy but were also present in other tauopathies. By using vertical and horizontal saccade velocity and gain as our measures, we were able to differentiate patients with progressive supranuclear palsy from other patients. Vertical saccade velocity was strongly correlated with dorsal midbrain volume.

CONCLUSION

Decreased visually guided saccade velocity and gain are suggestive of underlying tau pathology in FTD, with vertical saccade abnormalities most diagnostic of progressive supranuclear palsy.

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.

Hypokinesia without decrement distinguishes progressive supranuclear palsy from Parkinson's disease

Repetitive finger tapping is commonly used to assess bradykinesia in Parkinson's disease. The Queen Square Brain Bank diagnostic criterion of Parkinson's disease defines bradykinesia as 'slowness of initiation with progressive reduction in speed and amplitude of repetitive action'. Although progressive supranuclear palsy is considered an atypical parkinsonian syndrome, it is not known whether patients with progressive supranuclear palsy have criteria-defined bradykinesia. This study objectively assessed repetitive finger tap performance and handwriting in patients with Parkinson's disease (n = 15), progressive supranuclear palsy (n = 9) and healthy age- and gender-matched controls (n = 16). The motion of the hand and digits was recorded in 3D during 15-s repetitive index finger-to-thumb tapping trials. The main finding was hypokinesia without decrement in patients with progressive supranuclear palsy, which differed from the finger tap pattern in Parkinson's disease. Average finger separation amplitude in progressive supranuclear palsy was less than half of that in controls and Parkinson's disease (P < 0.001 in both cases). Change in tap amplitude over consecutive taps was computed by linear regression. The average amplitude slope in progressive supranuclear palsy was nearly zero (0.01°/cycle) indicating a lack of decrement, which differed from the negative slope in patients with Parkinson's disease OFF levodopa (-0.20°/cycle, P = 0.002). 'Hypokinesia', defined as <50% of control group's mean amplitude, combined with 'absence of decrement', defined as mean positive amplitude slope, were identified in 87% of finger tap trials in the progressive supranuclear palsy group and only 12% in the Parkinson's disease OFF levodopa group. In progressive supranuclear palsy, the mean amplitude was not correlated with disease duration or other clinimetric scores. In Parkinson's disease, finger tap pattern was compatible with criteria-defined bradykinesia, characterized by slowness with progressive reduction in amplitude and speed and increased variability in speed throughout the tap trial. In Parkinson's disease, smaller amplitude, slower speed and greater speed variability were all associated with a more severe Unified Parkinson's Disease Rating Scale motor score. Analyses of handwriting showed that micrographia, defined as smaller than 50% of the control group's mean script size, was present in 75% of patients with progressive supranuclear palsy and 15% of patients with Parkinson's disease (P = 0.022). Most scripts performed by patients with progressive supranuclear palsy did not exhibit decrements in script size. In conclusion, patients with progressive supranuclear palsy have a specific finger tap pattern of 'hypokinesia without decrement' and they do not have criteria-defined limb bradykinesia. Similarly, 'micrographia' and 'lack of decrement in script size' are also more common in progressive supranuclear palsy than in Parkinson's disease.

In vivo evaluation of white matter pathology in patients of progressive supranuclear palsy using TBSS

INTRODUCTION

The purpose of this research is to study white matter (WM) changes in patients of progressive supranuclear palsy (PSP) using automated analysis of diffusion tensor imaging (DTI) indices.

METHODS

This was a prospective study comprising of 24 patients of PSP and 26 matched healthy controls. Fractional anisotropy, mean diffusivity (MD), axial diffusivity, and radial diffusivity (RD) changes were studied in the WM of the PSP patients using an automated analysis technique, tract-based spatial statistics (TBSS). Two subtypes of PSP, i.e., classic Richardson's syndrome (PSP-RS) and parkinsonian type (PSP-P), were also compared among themselves to identify relative severity of WM changes as well as identify spatial distribution of the differences. Clinicoradiological correlation was done to determine the strength of correlation between WM abnormalities identified using TBSS and clinical scores.

RESULTS

There were areas of significant abnormality seen in the frontoparietal cerebral WM, thalamus, midbrain tectum, superior cerebellar peduncle, and cerebellar WM. The abnormalities were more spatially widespread on MD and RD maps. Compared to PSP-P, the patients of PSP-RS had more spatial abnormalities localized to the frontal WM. There was no correlation between the observed WM changes and clinical rating scales.

CONCLUSIONS

The TBSS analysis showed widespread WM abnormalities in PSP patients including areas which have been shown to be involved in previous pathological studies. PSP-RS showed more severe white matter abnormality compared to the PSP-P subtype.

How does the genetic assassin select its neuronal target?

Through many different routes of analysis, including human familial studies and animal models, we are identifying an increasing number of genes that are causative for human neurodegenerative disease and are now in a position for many such disorders to dissect the molecular pathology that gives rise to neuronal death. Yet a paradox remains: The majority of the genes identified cause neurodegeneration in specific neuronal subtypes, but the genes themselves are ubiquitously expressed. Furthermore, the different mutations in the same gene may cause quite different types of neurodegeneration. Something in our understanding of neurodegenerative disease is clearly missing, and we refer to this as the phenomenon of "neuronal targeting." Here we discuss possible explanations for neuronal targeting, why specific neuronal subtypes are vulnerable to specific mutations in ubiquitously expressed genes.

The in vivo distribution of brain tissue loss in Richardson's syndrome and PSP-parkinsonism: a VBM-DARTEL study

In this study, we wished to test, using magnetic resonance imaging and voxel-based morphometry (VBM), whether specific cortical and subcortical patterns of brain grey (GM) and white matter (WM) tissue loss can be detected in patients with Richardson's syndrome (PSP-RS) and progressive supranuclear palsy-parkinsonism (PSP-P), and possibly account for their clinical heterogeneity. Twenty patients with PSP, classified as PSP-RS (10 patients) or PSP-P (10 patients), and 24 healthy controls were studied. The Statistical Parametric Mapping (SPM5) and the Diffeomorphic Anatomical Registration using Exponentiated Lie algebra method were used to perform a VBM analysis. Compared with controls, both patient groups showed GM loss in the central midbrain, cerebellar lobes, caudate nuclei, frontotemporal cortices and right hippocampus. WM loss was detected in both conditions in the midbrain, left superior cerebellar peduncle, internal capsulae, and left premotor and bilateral prefrontal regions. Compared with PSP-P, patients with PSP-RS showed additional regions of GM loss in the midbrain, left cerebellar lobe and dentate nuclei. PSP-RS was also associated with a more severe WM loss in the midbrain, internal capsulae, and orbitofrontal, prefrontal and precentral/premotor regions, bilaterally. Patients with PSP-P showed a more pronounced GM loss only in the frontal cortex, bilaterally. This study shows that, albeit the overall pattern of brain atrophy associated with PSP appears remarkably consistent across the spectrum of clinical features recorded in life, major anatomical differences between these two conditions do exist. Such a different topographical distribution of tissue damage may account for the clinical differences between PSP-RS and PSP-P.

Progressive supranuclear palsy: clinicopathological concepts and diagnostic challenges

Progressive supranuclear palsy (PSP) is a clinical syndrome comprising supranuclear palsy, postural instability, and mild dementia. Neuropathologically, PSP is defined by the accumulation of neurofibrillary tangles. Since the first description of PSP in 1963, several distinct clinical syndromes have been described that are associated with PSP; this discovery challenges the traditional clinicopathological definition and complicates diagnosis in the absence of a reliable, disease-specific biomarker. We review the emerging nosology in this field and contrast the clinical and pathological characteristics of the different disease subgroups. These new insights emphasise that the pathological events and processes that lead to the accumulation of phosphorylated tau protein in the brain are best considered as dynamic processes that can develop at different rates, leading to different clinical phenomena. Moreover, for patients for whom the diagnosis is unclear, clinicians must continue to describe accurately the clinical picture of each individual, rather than label them with inaccurate diagnostic categories, such as atypical parkinsonism or PSP mimics. In this way, the development of the clinical features can be informative in assigning less common nosological categories that give clues to the underlying pathology and an understanding of the expected clinical course.

Voluntary, spontaneous and reflex blinking in patients with clinically probable progressive supranuclear palsy

Patients with progressive supranuclear palsy (PSP) often have blinking abnormalities. In this study we examined the kinematic features of voluntary, spontaneous and reflex blinking in 11 patients with PSP and healthy control subjects. Patients were asked to blink voluntarily as fast as possible; spontaneous blinking was recorded during two 60 s rest periods; reflex blinking was evoked by electrical stimulation of the supraorbital nerve. Eyelid movements were recorded with the SMART analyzer motion system. During voluntary blinking the closing and opening phases lasted longer in patients than in healthy subjects. Furthermore, the peak velocity of the closing phase of voluntary blinking was lower in patients than healthy subjects. During spontaneous blinking the blink rate was markedly lower in patients than in control subjects. Patient's recordings also showed kinematic abnormalities of spontaneous (reduced peak velocity of both closing and opening phases) and reflex (reduced peak velocity and increased duration of the opening phase) blinking. Recordings during reflex blinking disclosed an enhanced excitability of the interneuronal pool mediating the closing and opening blink phases. Finally, the pause, a neurophysiological marker of the switching processes between the closing and opening phases, was prolonged in all the three types of blinking. The abnormal kinematic variables correlated with patients' clinical and kinematic features. Abnormal voluntary, spontaneous and reflex blinking in patients with PSP reflects the widespread cortical, subcortical and brainstem degeneration related to this disease.

Subthalamic stimulation improves levodopa responsive symptoms in a case of progressive supranuclear palsy

A case is described of a patient with levodopa responsive parkinsonism, dyskinesia, and off periods who underwent bilateral deep brain stimulation of the subthalamic nuclei (DBS-STN) with good result. As the disease progressed, the patient fit diagnostic criteria for progressive supranuclear palsy parkinsonism (PSP-P). Benefit of DBS for the parkinsonian phenomena is still apparent 4 years later. That DBS-STN provided targeted symptom relief in this unusual patient suggests that the parkinsonism of PSP-P and that of Parkinson's disease (PD) may share a common pathophysiologic mechanism. The presence of dystonic features in this illness raises the possibility that the globus pallidus might also have been an effective target.

Clinical outcomes of progressive supranuclear palsy and multiple system atrophy

Prognostic predictors have not been defined for progressive supranuclear palsy (PSP) and multiple system atrophy (MSA). Subtypes of both disorders have been proposed on the basis of early clinical features. We performed a retrospective chart review to investigate the natural history of pathologically confirmed cases of PSP and MSA. Survival data and several clinically relevant milestones, namely: frequent falling, cognitive disability, unintelligible speech, severe dysphagia, dependence on wheelchair for mobility, the use of urinary catheters and placement in residential care were determined. On the basis of early symptoms, we subdivided cases with PSP into 'Richardson's syndrome' (RS) and 'PSP-parkinsonism' (PSP-P). Cases of MSA were subdivided according to the presence or absence of early autonomic failure. Sixty-nine (62.7%) of the 110 PSP cases were classified as RS and 29 (26.4%) as PSP-P. Of the 83 cases of MSA, 42 (53.2%) had autonomic failure within 2 years of disease onset. Patients with PSP had an older age of onset (P < 0.001), but similar disease duration to those with MSA. Patients with PSP reached their first clinical milestone earlier than patients with MSA (P < 0.001). Regular falls (P < 0.001), unintelligible speech (P = 0.04) and cognitive impairment (P = 0.03) also occurred earlier in PSP than in MSA. In PSP an RS phenotype, male gender, older age of onset and a short interval from disease onset to reaching the first clinical milestone were all independent predictors of shorter disease duration to death. Patients with RS also reached clinical milestones after a shorter interval from disease onset, compared to patients with PSP-P. In MSA early autonomic failure, female gender, older age of onset, a short interval from disease onset to reaching the first clinical milestone and not being admitted to residential care were independent factors predicting shorter disease duration until death. The time to the first clinical milestone is a useful prognostic predictor for survival. We confirm that RS had a less favourable course than PSP-P, and that early autonomic failure in MSA is associated with shorter survival.

Subcortical neurofibrillary tangles and argyrophilic grains in a case of familial frontotemporal dementia with parkinsonism

A case of familial frontotemporal dementia with parkinsonism (FTDP) similar to progressive supranuclear palsy (PSP) was reported. A 58-year-old man developed personality change followed by parkinsonism and dementia. Three family members showed similar symptoms. Cerebral atrophy was marked on the anterior frontotemporal lobes. The substantia nigra, hippocampus, peri-aqueductal gray matter and pontine nucleus were affected with globose neurofibrillary tangles (NFT) and glial tangles. Argyrophilic grains were distributed in the CA1-CA2. NFT, glial tangles and argyrophilic grains expressed four-repeat microtubule-associated protein tau (MAPT). MAPT gene had no mutation. Familial occurrence of FTDP with PSP-like tauopathy is rare.

Pure akinesia with gait freezing: a third clinical phenotype of progressive supranuclear palsy

The clinical syndrome of pure akinesia has most often been associated with progressive supranuclear palsy (PSP) and is characterized by difficulty initiating gait and "freezing" during walking, writing and speaking. Similar syndromes have been described under the rubrics of primary progressive freezing gait and primary gait ignition failure. We investigated the specificity of the clinical syndrome of pure akinesia with gait freezing (PAGF) for PSP-tau pathology. Among 749 patients archived at the QSBB, only 7 fulfilled proposed diagnostic criteria of: gradual onset of freezing of gait or speech; absent limb rigidity and tremor; no sustained response to levodopa; and no dementia or ophthalmoplegia in the first 5 years of disease. In these cases detailed pathological examination was performed. PSP was the pathological diagnosis in six patients, and Parkinson's disease (PD) in the seventh. As defined, this syndrome had a positive predictive value of 86% for PSP-tau pathology. In the cases with PSP there were no additional features of coexistent vascular or PD and the median PSP-tau score was 3, reflecting relative mild tau load. The clinical syndrome of PAGF appears to have a high specificity for PSP-tau pathology. This relatively uncommon presentation of PSP-tau pathology has less severe tau accumulation than in the more common, "classic" PSP clinical phenotype: Richardson's disease.

Glycolitic enzymes are targets of oxidation in aged human frontal cortex and oxidative damage of these proteins is increased in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder pathologically characterized by neuronal loss and gliosis mainly in specific subcortical nuclei, but also in the cerebral cortex. In addition to neuron loss, hyperphosphorylated tau deposition is found in neurons, astrocytes and coiled bodies. Limited studies have shown that certain oxidative products are increased in the PSP brain. The present study examines oxidative damage in the frontal cortex in 7 PSP compared with 8 age-matched controls. Western blotting of the frontal cortex showed increased 4-hydroxy-2-nonenal (HNE)-immunoreactive bands between 40 and 50 kDa in PSP cases. Bi-dimensional gel electrophoresis and Western blotting, together with mass spectometry, were used to identify HNE-modified proteins. Oxidized phosphoglycerate kinase 1 (PGK-1) and fructose bisphosphate aldolase A (aldolase A) were identified in all cases and 4 of 7 PSP cases, respectively. In contrast, PGK-1 and aldolase A were oxidized in 3 of 8 controls. Immunohistochemistry revealed the localization of aldolase A in neurons and astrocytes, and PGK-1 mainly in astrocytes. These findings show that PGK-1 and aldolase A are targets of oxidation in the frontal cortex in the aged human cerebral cortex and that oxidative damage of these proteins is markedly increased in the frontal cortex in PSP.

Voxel-based morphometry in autopsy proven PSP and CBD

The aim of this study was to compare the patterns of grey and white matter atrophy on MRI in autopsy confirmed progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD), and to determine whether the patterns vary depending on the clinical syndrome. Voxel-based morphometry was used to compare patterns of atrophy in 13 PSP and 11 CBD subjects and 24 controls. PSP and CBD subjects were also subdivided into those with a dominant dementia or extrapyramidal syndrome. PSP subjects showed brainstem atrophy with involvement of the cortex and underlying white matter. Frontoparietal grey and subcortical grey matter atrophy occurred in CBD. When subdivided, PSP subjects with an extrapyramidal syndrome had more brainstem atrophy and less cortical atrophy than CBD subjects with an extrapyramidal syndrome. PSP subjects with a dementia syndrome had more subcortical white matter atrophy than CBD subjects with a dementia syndrome. These results show regional differences between PSP and CBD that are useful in predicting the underlying pathology, and help to shed light on the in vivo distribution of regional atrophy in PSP and CBD.

Individual and regional variations of phospho-tau species in progressive supranuclear palsy

The purpose of this study was to learn about possible variations in phospho-tau profiles in terms of case-to-case differences, regional modifications and diversification of tau phosphorylation sites in five PSP cases with moderate to severe frontosubcortical dysfunction. Gel electrophoresis of sarkosyl-insoluble fractions and Western blotting with five anti-tau phospho-specific antibodies directed to phosphorylation sites Thr181, Ser202, Ser214, Ser396 and Ser422 were used to study four brain regions including frontal cortex, area 8, subcortical white matter of the frontal lobe, caudate/putamen: striatum, and basis pontis: pons. Although two bands of 66 and 62 kDa were observed in almost every region in each case, the intensity of the bands depends on the anti-tau phospho-specific antibody. More importantly, bands of 72, 50/55 and 37 kDa were commonly found in PSP brains, whereas other bands of about 60, 42, 33 and 29 kDa were irregularly observed. The pattern of bands differed slightly from one case to another and from one region to another. Moreover, the phospho-tau profile differed depending on the anti-tau phospho-specific antibody used. These data suggest that several species of tau are variably phosphorylated at a given time in a given region (and probably in a given cell), and that tau aggregates are composed of several phosphorylated truncated or cleaved tau molecules, in addition to phosphorylated complete tau isoforms.

Characteristics of two distinct clinical phenotypes in pathologically proven progressive supranuclear palsy: Richardson's syndrome and PSP-parkinsonism

The clinical diagnosis of progressive supranuclear palsy (PSP) relies on the identification of characteristic signs and symptoms. A proportion of pathologically diagnosed cases do not develop these classic features, prove difficult to diagnose during life and are considered as atypical PSP. The aim of this study was to examine the apparent clinical dichotomy between typical and atypical PSP, and to compare the biochemical and genetic characteristics of these groups. In 103 consecutive cases of pathologically confirmed PSP, we have identified two clinical phenotypes by factor analysis which we have named Richardson's syndrome (RS) and PSP-parkinsonism (PSP-P). Cases of RS syndrome made up 54% of all cases, and were characterized by the early onset of postural instability and falls, supranuclear vertical gaze palsy and cognitive dysfunction. A second group of 33 (32%) were characterized by asymmetric onset, tremor, a moderate initial therapeutic response to levodopa and were frequently confused with Parkinson's disease (PSP-P). Fourteen cases (14%) could not be separated according to these criteria. In RS, two-thirds of cases were men, whereas the sex distribution in PSP-P was even. Disease duration in RS was significantly shorter (5.9 versus 9.1 years, P < 0.001) and age at death earlier (72.1 versus 75.5 years, P = 0.01) than in PSP-P. The isoform composition of insoluble tangle-tau isolated from the basal pons also differed significantly. In RS, the mean four-repeat:three-repeat tau ratio was 2.84 and in PSP-P it was 1.63 (P < 0.003). The effect of the H1,H1 PSP susceptibility genotype appeared stronger in RS than in PSP-P (odds ratio 13.2 versus 4.5). The difference in genotype frequencies between the clinical subgroups was not significant. There were no differences in apolipoprotein E genotypes. The classic clinical description of PSP, which includes supranuclear gaze palsy, early falls and dementia, does not adequately describe one-third of cases in this series of pathologically confirmed cases. We propose that PSP-P represents a second discrete clinical phenotype that needs to be clinically distinguished from classical PSP (RS). The different tau isoform deposition in the basal pons suggests that this may ultimately prove to be a discrete nosological entity.

Treatment of progressive supranuclear palsy and corticobasal degeneration

Success in treating patients with progressive supranuclear palsy and corticobasal degeneration remains exceedingly low. This finding probably relates to the widespread distribution of the pathological changes that account for the varied and complex spectrum of clinical manifestations. Dopaminergic drugs are regularly used for the parkinsonian features; however, these rarely result in more than modest benefit, and when better or sustained responses are obtained, as sometimes occurs in progressive supranuclear palsy, the clinical features are atypical and diagnosis is often delayed or not made in life. A variety of other treatments have been used in both disorders, sometimes directed at other specific features such as dystonia or myoclonus, and these treatments will be reviewed. Greater success in treating these disorders will require advances in our understanding of their cause(s) or the pathogenetic mechanisms underlying the neurodegenerative processes. The similarities in the molecular pathology of these four-repeat tauopathies suggests that important advances in the management of one will have a definite impact on the treatment of the other.

Deficiency of the Mre11 DNA repair complex in Alzheimer's disease brains

The hallmarks of Alzheimer's disease (AD) brains are deposition of Abeta plaques, appearance of neurofibrillary tangles, and extensive loss of neuronal cells. While Abeta plaques and neurofibrillary tangles play a significant role in the pathogenic dysfunction of neurons, factors that accelerate the neurodegenerating process remain to be defined. One set of factors examined in this study is the Mre11 protein complex, composed of Rad50, Mre11 and Nbs1. This protein complex plays an essential role in cellular responses to DNA damage, such as initiating cell cycle checkpoints and repairing damaged DNA. A defect in any component of this protein complex is detrimental to cells. Recently, several groups have observed abnormal cell cycle regulation and/or accumulated DNA damage in AD neurons. These pathological alterations could conceivably be caused or exacerbated by any compromise in the Mre11 complex. In this study, we compared the levels of the Mre11 complex proteins in brain samples from AD and age-matched non-dementia controls. We show for the first time that the Mre11 complex proteins are present in neurons of the adult human cortex and cerebellum. These proteins were found substantially reduced in the neurons of AD cortex. Our finding suggests that the loss of the Mre11 complex may be associated with the pathogenesis of AD.

Caribbean parkinsonism and other atypical Parkinsonian disorders

Atypical parkinsonism (AP) is a term applied to disorders characterized by parkinsonism that evolves rapidly, with poor or transient response to levodopa, or has other associated features such as early falls and postural instability, early autonomic failure, supranuclear gaze palsy, pyramidal or cerebellar signs, alien hand syndrome or severe ideomotor apraxia. The most common AP are multiple system atrophy, progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). Other APs include Caribbean parkinsonism (CP) and parkinsonism-dementia complex of Guam (PDC). In this review we provide an update in etiology, neuropathology, diagnosis and treatment of atypical parkinsonian disorders associated with protein tau deposit, also known as tauopathies.

Differential involvement and heterogeneous phosphorylation of tau isoforms in progressive supranuclear palsy

We found previously that aggregated insoluble tau protein in progressive supranuclear palsy (PSP) brains exhibits a heterogeneous pattern that is not segregated by the type of clinical presentation. Here we have investigated tau isoform composition from 20 PSP cases and found marked variation between different brains. Cases were classified into three groups, each comprising essentially of (1) 1N4R; (2) 1N4R and 1N3R; or (3) 1N4R, 1N3R and 0N4R tau isoforms. There was also an absence of a simple relationship between isoform composition and the pattern of insoluble tau before dephosphorylation. We conclude that there is distinct molecular heterogeneity in the involvement of tau isoforms in the tau pathology in PSP.

Progressive supranuclear palsy

Progressive supranuclear palsy, also known as Steele-Richardson-Olszewski syndrome, is an uncommon neurodegenerative parkinsonian disorder that starts in middle and late life, and is frequently misdiagnosed as Parkinson's disease. This review will cover the epidemiology, clinical picture, differential diagnosis and management of patients with progressive supranuclear palsy.

Anatamopathological spectrum of tauopathies

The presence of tau-positive intraneuronal filamentous inclusions with or without additional inclusions in glial cells has been recognised as a major neuropathological feature in a significant group of neurodegenerative diseases, which are described as tauopathies. In one category of such diseases, the neuronal inclusions occur in association with extracellular deposition of a second aggregated protein (secondary tauopathies), whereas in another, the filamentous inclusions composed of tau are the sole neuropathological abnormality (primary tauopathies). Genetic studies of tauopathies in general, and in frontotemporal dementia with parkinsonism linked to chromosome 17 in particular, have significantly contributed to our knowledge about the pathogenesis not only of rare hereditary conditions but also of other more common diseases such as Alzheimer's disease and progressive supranuclear palsy.

Parkinson's syndrome associated with neurofibrillary degeneration and tau pathologic findings

Several distinct clinical syndromes presenting with parkinsonism have been associated with subcortical neurofibrillary degeneration and the abnormal accumulation of hyperphosphorylated tau protein in the brain. Mutations of tau have been linked with a small number of autosomal dominantly inherited families who present with frontolimbic cognitive deficits, behavioural disorders, and Parkinson's syndrome. Some of the sporadic disorders (progressive supranuclear palsy [PSP] and corticobasal degeneration) have been referred to by molecular pathologists as primary tauopathies, implicating abnormalities of tau in their pathogenesis. We have identified a sporadic parkinsonian syndrome characterised by bradykinesia, a variable response to levodopa, and a mean duration of disease of 9 years, which resembles bodig (Parkinson's-dementia of Guam), and histologically has close similarities with both PSP and postencephalitic parkinsonism. Further characterisation of these cases frequently confused with Parkinson's disease may broaden the clinical spectrum of parkinsonian disorders linked with neurofibrillary tangle formation.

Brain banking for neurodegenerative diseases

PURPOSE OF REVIEW

Brain banking remains a necessity for the study of neurodegenerative diseases. While the characterization of pathology observed at autopsy confirms clinical diagnosis, the structure and contents of pathological hallmarks are the starting point from which disease pathogenesis may be elucidated. Traditional neuropathology has served to define, characterize, and diagnose neurodegenerative diseases, accompanied by clinical presentation. The pathological substrates are then studied for their role in how they cause dysfunction in disease, or how their accumulation is presumably damaging.

RECENT FINDINGS

New genetic findings have revolutionized these studies and have prompted a reexamination of traditional pathological definitions of disease. Many familial genetic mutations have been found, encoding proteins such as synuclein, parkin, tau, and others, creating genetic ways to define neurodegenerative diseases. Many of these proteins are components of aggregates, thus the ability to label these proteins has revealed new pathological characteristics that must be standardized. More complicating is that many proteins genetically linked to clinically distinct diseases are involved in overlapping neuropathology of what now appears to be a spectrum of diseases: 'synucleinopathies', 'tauopathies', and so on. Moreover, as genetic discoveries fuel molecular experiments on brain tissue, banking methods must now accommodate these techniques. Lastly, DNA screening involves ethical issues beyond those which were previously considered with postmortem tissue banking.

SUMMARY

As more proteins are linked to disease, more is revealed about the underlying causative mechanisms, exposing points for interventions. To achieve this end, characterization for neurodegenerative disease in the post genomic era must include genotype, phenotype and clinical characterization, and postmortem brain banking data which includes these.