A comparison of clinical and pathological features of young- and old-onset Parkinson's disease

Haptoglobin phenotype modifies serum iron levels and the effect of smoking on Parkinson disease risk

INTRODUCTION

Haptoglobin is a hemoglobin-binding protein that exists in three functionally different phenotypes, and haptoglobin phenotype 2-1 has previously been associated with Parkinson disease (PD) risk, with mechanisms not elucidated. Some evidence is emerging that low levels of serum iron may increase PD risk. In this study we investigated whether PD patients have lower serum iron and ferritin than controls, and whether this is dependent on haptoglobin phenotype. We also investigated the effect of Hp phenotype as a modifier of the effect of smoking on PD risk.

METHODS

The study population consisted of 128 PD patients and 226 controls. Serum iron, ferritin, and haptoglobin phenotype were determined, and compared between PD cases and controls. Stratified analysis by haptoglobin phenotype was performed to determine effect of haptoglobin phenotype on serum iron parameter differences between PD cases and controls and to investigate its role in the protective effect of smoking on PD risk.

RESULTS

PD cases had lower serum iron than controls (83.28 ug/100 ml vs 94.00 ug/100 ml, p 0.006), and in particular among subjects with phenotype 2-1. The protective effect of smoking on PD risk resulted stronger in subjects with phenotype 1-1 and 2-2, and weakest among subjects with phenotype 2-1. Ferritin levels were higher in PD cases than controls among subjects of White ethnicity.

CONCLUSIONS

Our results report for the first time that the haptoglobin phenotype may be a contributor of iron levels abnormalities in PD patients. The mechanisms for these haptoglobin-phenotype specific effects will have to be further elucidated.

Digitomotography in Parkinson's disease: a cross-sectional and longitudinal study

Motor symptoms in Parkinson’s disease (PD) are usually assessed with semi-quantitative tests such as the Unified PD Rating Scale (UPDRS) which are limited by subjectivity, categorical design, and low sensitivity. Particularly bradykinesia as assessed e.g. with speeded index finger tapping exhibits low validity measures. This exploratory study set out to (i) assess whether force transducer-based objective and quantitative analysis of motor coordination in index finger tapping is able to distinguish between PD patients and controls, and (ii) assess longitudinal changes. Sixteen early-stage and 17 mid-stage PD patients as well as 18 controls were included in the cross-sectional part of the study; thirteen, 16 and 16 individuals of the respective groups agreed in a reassessment 12 months later. Frequency, force, rhythmicity, regularity and laterality of speeded and metronome paced tapping were recorded by digitomotography using a quantitative motor system ("Q-Motor"). Analysis of cross-sectional data revealed most consistent differences between PD patients and controls in variability of tap performance across modalities assessed. Among PD patients, variability of taps and the ability to keep a given rhythm were associated with UPDRS motor and finger tapping scores. After 12 months, laterality parameters were reduced but no other parameters changed significantly. This data suggests that digitomotography provides quantitative and objective measures capable to differentiate PD from non-PD in a small cohort, however, the value of the assessment to track PD progression has to be further evaluated in larger cohorts of patients.

NMR metabonomics of cerebrospinal fluid distinguishes between Parkinson's disease and controls

This study assesses if nuclear magnetic resonance (NMR) metabonomics can discriminate between Parkinson's disease (PD) patients and control subjects, and consequently identify metabolic markers for the disease. One-dimensional (1)H NMR spectroscopy was used for quantitative analysis of metabolites in the cerebrospinal fluid (CSF) from 10 PD patients and 10 control individuals, together with uni- and multivariate statistical analysis to discriminate between the groups and to identify significantly altered metabolite concentrations. In total 60 metabolites were identified and of those 38 were quantified in all CSF samples. An overall lowering of metabolite content was observed in PD patients compared to control subjects (fold change of 0.85±0.30). Multivariate statistics reveal significant changes (ǀw*ǀ>0.2) among nine metabolites (alanine, creatinine, dimethylamine, glucose, lactate, mannose, phenylalanine, 3-hydroxyisobutyric acid and 3-hydroxyisovaleric acid). Three of these (alanine, creatinine and mannose) are identified as significantly changed also by univariate statistics (p<0.00132, Bonferroni corrected). Panels with all or a selected set of these metabolites were successfully used for discriminating between the two groups. In conclusion, NMR metabonomics can readily determine metabolite concentrations in CSF, identify putative biomarkers that distinguish between the PD patients and control subjects, and thus potentially become a tool for diagnostic purposes.

Cerebrospinal fluid Aβ42 levels and APP processing pathway genes in Parkinson's disease

BACKGROUND

Of recent interest is the finding that certain cerebrospinal fluid (CSF) biomarkers traditionally linked to Alzheimer's disease (AD), specifically amyloid beta protein (Aβ), are abnormal in PD CSF. The aim of this exploratory investigation was to determine whether genetic variation within the amyloid precursor protein (APP) processing pathway genes correlates with CSF Aβ42 levels in Parkinson's disease (PD).

METHODS

Parkinson's disease (n = 86) and control (n = 161) DNA were genotyped for 19 regulatory region tagging single-nucleotide polymorphisms (SNPs) within nine genes (APP, ADAM10, BACE1, BACE2, PSEN1, PSEN2, PEN2, NCSTN, and APH1B) involved in the cleavage of APP. The SNP genotypes were tested for their association with CSF biomarkers and PD risk while adjusting for age, sex, and APOE ɛ4 status.

RESULTS

Significant correlation with CSF Aβ42 levels in PD was observed for two SNPs, (APP rs466448 and APH1B rs2068143). Conversely, significant correlation with CSF Aβ42 levels in controls was observed for three SNPs (APP rs214484, rs2040273, and PSEN1 rs362344).

CONCLUSIONS

In addition, results of this exploratory investigation suggest that an APP SNP and an APH1B SNP are marginally associated with PD CSF Aβ42 levels in APOE ɛ4 noncarriers. Further hypotheses generated include that decreased CSF Aβ42 levels are in part driven by genetic variation in APP processing genes. Additional investigation into the relationship between these findings and clinical characteristics of PD, including cognitive impairment, compared with other neurodegenerative diseases, such as AD, are warranted. © 2015 International Parkinson and Movement Disorder Society.

Evaluation of selective positron emission tomography template method for spatial normalization of amyloid imaging with 11C-Pittsburgh Compound B

OBJECTIVE

Spatial normalization of C-Pittsburgh Compound B (PiB) images is challenging for an automatic quantitative analysis without magnetic resonance imaging (MRI) because of different distribution patterns between amyloid positive and negative images. To overcome this issue, we evaluated a selective positron emission tomography template (SPT) method.

MATERIALS AND METHODS

Three sets of single positron emission tomography templates were created: PiB negative template, PiB positive template, and mixed template. Sixty-one patients with dementia were enrolled as the validation cohort. Magnetic resonance imaging-aided normalization method was used as a reference. The SPT method was based on visual classification (positive, negative, and equivocal). The optimal templates for each visual group were determined by correlation values and average percent errors (APEs) with MRI-aided normalization. The results of the SPT and the single template methods were compared with those of MRI-aided normalization in terms of correlation values, APEs, and concordance rates.

RESULTS

The SPT (PiB negative template for the negative and equivocal groups and PiB positive template for the positive group) showed higher correlations and concordance rate and lower APEs with MRI-aided normalization than did the single template.

CONCLUSIONS

Use of the SPT provides accurate normalization of amyloid images without MRI.

Impact of regional striatal dopaminergic function on kinematic parameters of Parkinson's disease

Among the cardinal parkinsonian motor deficits, the severity of bradykinesia correlates with striatal dopamine loss. However, the impact of regional striatal dopamine loss on specific components of bradykinesia remains unknown. Using gyroscopes, we measured the amplitude, speed, and frequency of finger tapping in 24 untreated patients with Parkinson's disease (PD) and 28 healthy controls. Using positron emission tomography (PET) studies and [(18)F]-N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane (FP-CIT) in PD patients, we investigated the relationship between the mean values, variability and decrements of various kinematic parameters of finger tapping on one side (e.g. the mean, variability and decrement) and contralateral striatal FP-CIT binding. Compared with controls, PD patients had reduced amplitudes and speeds of tapping and showed greater decrement in those parameters. PD patients also exhibited greater irregularity in amplitude, speed, and frequency. Putaminal FP-CIT uptake levels correlated with the mean speed and amplitude, and caudate uptake levels correlated with mean amplitude. The variability of amplitude and speed correlated only with the caudate uptake levels. Neither caudate nor putaminal uptake correlated with frequency-related parameters or decrement in amplitude or speed. Reduced amplitude and speed of repetitive movement may be related to striatal dopaminergic deficit. Dopaminergic action in the caudate nucleus is required to maintain consistency of amplitude and speed. Although decrement of amplitude and speed is known to be specific for PD, we found that it did not mirror the degree of striatal dopamine depletion.

Time- and frequency-domain parameters of heart rate variability and sympathetic skin response in Parkinson's disease

The autonomic nervous system (ANS) is regularly affected in Parkinson's disease (PD). Information on autonomic dysfunction can be derived from e.g. altered heart rate variability (HRV) and sympathetic skin response (SSR). Such parameters can be quantified easily and measured repeatedly which might be helpful for evaluating disease progression and therapeutic outcome. In this 2-center study, HRV and SSR of 45 PD patients and 26 controls were recorded. HRV was measured during supine metronomic breathing and analyzed in time- and frequency-domains. SSR was evoked by repetitive auditory stimulation. Various ANS parameters were compared (1) between patients and healthy controls, (2) to clinical scales (Unified Parkinson's disease rating scale, Mini-Mental State Examination, Becks Depression Inventory), and (3) to disease duration. Root mean square of successive differences (RMSSD) and low frequency/high frequency (LF/HF) ratio differed significantly between PD and controls. Both, HRV and SSR parameters showed low or no association with clinical scores. Time-domain parameters tended to be affected already at early PD stages but did not consistently change with longer disease duration. In contrast, frequency-domain parameters were not altered in early PD phases but tended to be lower (LF, LF/HF ratio), respectively higher (HF) with increasing disease duration. This report confirms previous results of altered ANS parameters in PD. In addition, it suggests that (1) these ANS parameters are not relevantly associated with motor, behavioral, and cognitive changes in PD, (2) time-domain parameters are useful for the assessment of early PD, and (3) frequency-domain parameters are more closely associated with disease duration.

α-Synucleinopathy phenotypes

α-Synucleinopathies are neurodegenerative diseases characterised by the abnormal accumulation of α-synuclein aggregates in neurons, nerve fibres or glial cells. While small amounts of these α-synuclein pathologies can occur in some neurologically normal individuals who do not have associated neurodegeneration, the absence of neurodegeneration in such individuals precludes them from having a degenerative α-synucleinopathy, and it has yet to be established whether such individuals have a form of preclinical disease. There are three main types of α-synucleinopathy, Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA), with other rare disorders also having α-synuclein pathologies, such as various neuroaxonal dystrophies. Multiple clinical phenotypes exist for each of the three main α-synucleinopathies, with these phenotypes differing in the dynamic distribution of their underlying neuropathologies. Identifying the factors involved in causing different α-synuclein phenotypes may ultimately lead to more targeted therapeutics as well as more accurate clinical prognosis.

Psychiatric diseases predated the occurrence of Parkinson disease: a retrospective cohort study

PURPOSE

The influence of mental illness early in life on the subsequent risk of Parkinson disease (PD) and its clinical picture remain obscure. This study investigated the effects of psychiatric diseases on a subsequent PD diagnosis.

METHODS

We used the Longitudinal Health Insurance Database 2000 of Taiwan to identify 73,597 patients who visited ambulatory care centers or were hospitalized with a first-time diagnosis of anxiety, affective disorders, or schizophrenia between 2001 and 2003 as the study cohort. We also randomly selected 220,791 enrollees matched with the study cohort for comparison. Each patient was individually tracked for 6 years to identify a subsequent PD diagnosis. Stratified Cox proportional hazard regressions were performed for the analysis.

RESULTS

The incidence rate of PD per 1000 person-years was 4.91 (95% confidence interval [CI], 4.71-5.12) and 1.63 (95% CI, 1.56-1.70) for the psychiatric and comparison groups, respectively. Patients with psychiatric illnesses were more vulnerable to developing PD than nonpsychiatric individuals, exhibiting a 2.38-fold increased risk (95% CI, 2.23-2.53) after other covariates were considered. Furthermore, patients with schizophrenia exhibited the highest risk for developing PD.

CONCLUSIONS

We suggest effective monitoring of patients with psychiatric disturbances for potential long-term neurodegenerative diseases.

Mutations in VPS26A are not a frequent cause of Parkinson's disease

VPS35 mutations have been identified as a cause of autosomal dominantly inherited Parkinson's disease (PD). VPS35 interacts with VPS26A in the retromer complex that links mitochondrial and lysosomal pathways, which have both been shown to be dysfunctional in PD. Thus, mutations in VPS26A may be associated with PD. To test this hypothesis, we screened 245 idiopathic PD patients and 185 control subjects for mutations in the retromer subunit VPS26A. We found 2 novel missense variants in patients and 2 known missense variants in control subjects. The missense variants were unlikely to be disease causing, suggesting that VPS26A mutations are not a frequent cause of PD.

Fronto-striatal gray matter contributions to discrimination learning in Parkinson's disease

Discrimination learning deficits in Parkinson's disease (PD) have been well-established. Using both behavioral patient studies and computational approaches, these deficits have typically been attributed to dopamine imbalance across the basal ganglia. However, this explanation of impaired learning in PD does not account for the possible contribution of other pathological changes that occur in the disease process, importantly including gray matter loss. To address this gap in the literature, the current study explored the relationship between fronto-striatal gray matter atrophy and learning in PD. We employed a discrimination learning task and computational modeling in order to assess learning rates in non-demented PD patients. Behaviorally, we confirmed that learning rates were reduced in patients relative to controls. Furthermore, voxel-based morphometry imaging analysis demonstrated that this learning impairment was directly related to gray matter loss in discrete fronto-striatal regions (specifically, the ventromedial prefrontal cortex, inferior frontal gyrus and nucleus accumbens). These findings suggest that dopaminergic imbalance may not be the sole determinant of discrimination learning deficits in PD, and highlight the importance of factoring in the broader pathological changes when constructing models of learning in PD.

The heterogeneity of cognitive symptoms in Parkinson's disease: a meta-analysis

Several studies have reported heterogeneity in cognitive symptoms associated with specific characteristics of patients with Parkinson's disease (PD). Indeed, researchers have characterised subtypes of patients suffering from PD according to various criteria. Those most frequently used are the type of predominant motor symptoms (tremors or non-tremor symptoms), age at onset and presence of depression. Some characteristics, like the predominant motor subtypes, as well as the presence of depression, are more widely used to categorise cognitive differences between patients. The goal of this study was to analyse the impact of the type of predominant motor symptoms and depression on cognition in PD. A meta-analysis of 27 studies (from 1989 to 2012) was carried out to calculate the average effect size of these factors on the most often used cognitive test during those past years to evaluate cognitive skills, the Mini-Mental State Examination. The studies analysed showed significant mean weighted effect sizes on cognition for the type of motor symptoms (d=0.42; 95% CI 0.30 to 0.54) and for depression (d=0.52; 95% CI 0.38 to 0.66). These results suggested that PD participants with non-tremor predominant motor symptoms or with depression had more or more severe cognitive impairments. Identification of different subtypes in PD is important for a better understanding of the cognitive symptoms associated with this disease. Better knowing the impact of different features of PD subgroups could help to design more appropriate treatments for patients with PD.

An update on the management of young-onset Parkinson's disease

In the text that follows, we review the main clinical features, genetic characteristics, and treatment options for Parkinson's disease (PD), considering the age at onset. The clinical variability between patients with PD points at the existence of subtypes of the disease. Identification of subtypes is important, since a focus on homogenous group may lead to tailored treatment strategies. One of the factors that determine variability of clinical features of PD is age of onset. Young-onset Parkinson's disease (YOPD) is defined as parkinsonism starting between the ages of 21 and 40. YOPD has a slower disease progression and a greater incidence and earlier appearance of levodopa-induced motor complications; namely, motor fluctuations and dyskinesias. Moreover, YOPD patients face a lifetime of a progressive disease with gradual worsening of quality of life and their expectations are different from those of their older counterparts. Knowing this, treatment plans and management of symptoms must be paid careful attention to in order to maintain an acceptable quality of life in YOPD patients.

Detection of copy number changes in genes associated with Parkinson's disease in Iranian patients

Parkinson's disease (PD) is the second most common neurodegenerative disorder, after Alzheimer's disease. Genomic rearrangements are common mutations reported in PD patients. In this study, we investigated the prevalence of genomic rearrangements in a total of 232 Iranian PD patients, out of which 102 were sporadic early-onset (age-at-onset ≤ 45 years) and 51 had a family history. We used multiplex ligation-dependent probe amplification (MLPA) method to detect exon dosage changes. Two new improved probe kits, SALSA P051 and P052, were used and altogether α-synuclein, parkin, UCHL1, PINK1, DJ-1, LRRK2, GCH1, ATP13A2, CAV1, CAV2, LPA and TNFRSF9 genes were analyzed. Exon or whole-gene rearrangements were identified in 14 (13.7%) sporadic early-onset PD patients in parkin, α-synuclein and PINK1. Of familial PD patients 46 cases from 18 families (35.3%) showed exon or whole-gene rearrangements in parkin, α-synuclein, PINK1, DJ-1, and ATP13A2 genes. All changes were verified by quantitative PCR (qPCR). Novel mutations and unusual clinical features are reported in this study. Mutations in parkin were the predominant genetic cause in both early-onset and familial PD groups. Also the mutations observed in family PD group are more in number and diversity than the sporadic early-onset PD group.

Drug-induced dyskinesia in Parkinson's disease. Should success in clinical management be a function of improvement of motor repertoire rather than amplitude of dyskinesia?

BACKGROUND

Dyskinesia, a major complication in the treatment of Parkinson's disease (PD), can require prolonged monitoring and complex medical management.

DISCUSSION

The current paper proposes a new way to view the management of dyskinesia in an integrated fashion. We suggest that dyskinesia be considered as a factor in a signal-to-noise ratio (SNR) equation where the signal is the voluntary movement and the noise is PD symptomatology, including dyskinesia. The goal of clinicians should be to ensure a high SNR in order to maintain or enhance the motor repertoire of patients. To understand why such an approach would be beneficial, we first review mechanisms of dyskinesia, as well as their impact on the quality of life of patients and on the health-care system. Theoretical and practical bases for the SNR approach are then discussed.

SUMMARY

Clinicians should not only consider the level of motor symptomatology when assessing the efficacy of their treatment strategy, but also breadth of the motor repertoire available to patients.

Persons with Parkinson's disease exhibit decreased neuromuscular complexity during gait

OBJECTIVE

Individual muscle activation patterns may be controlled by motor modules constructed by the central nervous system to simplify motor control. This study compared modular control of gait between persons with Parkinson's disease (PD) and neurologically-healthy older adults (HOA) and investigated relationships between modular organization and gait parameters in persons with PD.

METHODS

Fifteen persons with idiopathic PD and fourteen HOA participated. Electromyographic recordings were made from eight leg muscles bilaterally while participants walked at their preferred walking speed for 10 min on an instrumented treadmill. Non-negative matrix factorization techniques decomposed the electromyographic signals, identifying the number and nature of modules accounting for 95% of variability in muscle activations during treadmill walking.

RESULTS

Generally, fewer modules were required to reconstruct muscle activation patterns during treadmill walking in PD compared to HOA (p < .05). Control of knee flexor and ankle plantar flexor musculature was simplified in PD. Activation timing was altered in PD while muscle weightings were unaffected. Simplified neuromuscular control was related to decreased walking speed in PD.

CONCLUSION

Neuromuscular control of gait is simplified in PD and may contribute to gait deficits in this population.

SIGNIFICANCE

Future studies of locomotor rehabilitation in PD should consider neuromuscular complexity to maximize intervention effectiveness.

Cerebral pathological and compensatory mechanisms in the premotor phase of leucine-rich repeat kinase 2 parkinsonism

Compensatory cerebral mechanisms can delay motor symptom onset in Parkinson's disease. We aim to characterize these compensatory mechanisms and early disease-related changes by quantifying movement-related cerebral function in subjects at significantly increased risk of developing Parkinson's disease, namely carriers of a leucine-rich repeat kinase 2-G2019S mutation associated with dominantly inherited parkinsonism. Functional magnetic resonance imaging was used to examine cerebral activity evoked during internal selection of motor representations, a core motor deficit in clinically overt Parkinson's disease. Thirty-nine healthy first-degree relatives of Ashkenazi Jewish patients with Parkinson's disease, who carry the leucine-rich repeat kinase 2-G2019S mutation, participated in this study. Twenty-one carriers of the leucine-rich repeat kinase 2-G2019S mutation and 18 non-carriers of this mutation were engaged in a motor imagery task (laterality judgements of left or right hands) known to be sensitive to motor control parameters. Behavioural performance of both groups was matched. Mutation carriers and non-carriers were equally sensitive to the extent and biomechanical constraints of the imagined movements in relation to the current posture of the participants' hands. Cerebral activity differed between groups, such that leucine-rich repeat kinase 2-G2019S carriers had reduced imagery-related activity in the right caudate nucleus and increased activity in the right dorsal premotor cortex. More severe striatal impairment was associated with stronger effective connectivity between the right dorsal premotor cortex and the right extrastriate body area. These findings suggest that altered movement-related activity in the caudate nuclei of leucine-rich repeat kinase 2-G2019S carriers might remain behaviourally latent by virtue of cortical compensatory mechanisms involving long-range connectivity between the dorsal premotor cortex and posterior sensory regions. These functional cerebral changes open the possibility to use a prospective study to test their relevance as early markers of Parkinson's disease.

Autonomous identification of freezing of gait in Parkinson's disease from lower-body segmental accelerometry

Background

We have previously published a technique for objective assessment of freezing of gait (FOG) in Parkinson's disease (PD) from a single shank-mounted accelerometer. Here we extend this approach to evaluate the optimal configuration of sensor placement and signal processing parameters using seven sensors attached to the lumbar back, thighs, shanks and feet.

Methods

Multi-segmental acceleration data was obtained from 25 PD patients performing 134 timed up and go tasks, and clinical assessment of FOG was performed by two experienced raters from video. Four metrics were used to compare objective and clinical measures; the intraclass correlation coefficient (ICC) for number of FOG episodes and the percent time frozen per trial; and the sensitivity and specificity of FOG detection.

Results

The seven-sensor configuration was the most robust, scoring highly on all measures of performance (ICC number of FOG 0.75; ICC percent time frozen 0.80; sensitivity 84.3%; specificity 78.4%). A simpler single-shank sensor approach provided similar ICC values and exhibited a high sensitivity to FOG events, but specificity was lower at 66.7%. Recordings from the lumbar sensor offered only moderate agreement with the clinical raters in terms of absolute number and duration of FOG events (likely due to musculoskeletal attenuation of lower-limb 'trembling' during FOG), but demonstrated a high sensitivity (86.2%) and specificity (82.4%) when considered as a binary test for the presence/absence of FOG within a single trial.

Conclusions

The seven-sensor approach was the most accurate method for quantifying FOG, and is best suited to demanding research applications. A single shank sensor provided measures comparable to the seven-sensor approach but is relatively straightforward in execution, facilitating clinical use. A single lumbar sensor may provide a simple means of objective FOG detection given the ubiquitous nature of accelerometers in mobile telephones and other belt-worn devices.

Advanced Parkinson's disease effect on goal-directed and habitual processes involved in visuomotor associative learning

The present behavioral study re-addresses the question of habit learning in Parkinson's disease (PD). Patients were early onset, non-demented, dopa-responsive, candidates for surgical treatment, similar to those we found earlier as suffering greater dopamine depletion in the putamen than in the caudate nucleus. The task was the same conditional associative learning task as that used previously in monkeys and healthy humans to unveil the striatum involvement in habit learning. Sixteen patients and 20 age- and education-matched healthy control subjects learned sets of 3 visuo-motor associations between complex patterns and joystick displacements during two testing sessions separated by a few hours. We distinguished errors preceding vs. following the first correct response to compare patients' performance during the earliest phase of learning dominated by goal-directed actions with that observed later on, when responses start to become habitual. The disease significantly retarded both learning phases, especially in patients under 60 years of age. However, only the late phase deficit was disease severity-dependent and persisted on the second testing session. These findings provide the first corroboration in Parkinson patients of two ideas well-established in the animal literature. The first is the idea that associating visual stimuli to motor acts is a form of habit learning that engages the striatum. It is confirmed here by the global impairment in visuo-motor learning induced by PD. The second idea is that goal-directed behaviors are predominantly caudate-dependent whereas habitual responses are primarily putamen-dependent. At the advanced PD stages tested here, dopamine depletion is greater in the putamen than in the caudate nucleus. Accordingly, the late phase of learning corresponding to the emergence of habitual responses was more vulnerable to the disease than the early phase dominated by goal-directed actions.

Movement related dynamics of subthalmo-cortical alpha connectivity in Parkinson's disease

Functional neurosurgical techniques provide a unique opportunity to explore patterns of interaction between the cerebral cortex and basal ganglia in patients with Parkinson's disease (PD). Previous work using simultaneous magnetoencephalographic (MEG) and local field potential (LFP) recordings from the region of the subthalamic nucleus (STNr) has characterised resting patterns of connectivity in the alpha and beta frequency bands and their modulation by dopaminergic medication. Recently we have also characterised the effect of movement on patterns of gamma band coherence between the STNr and cortical sites. Here we specifically investigate how the prominent coherence between the STNr and temporal cortex in the alpha band is modulated by movement both on and off dopaminergic medication in patients following the insertion of Deep Brain Stimulation (DBS) electrodes. We show that movement is associated with a suppression of local alpha power in the temporal cortex and STNr that begins about 2 s prior to a self-paced movement and is independent of dopaminergic status. In contrast, the peak reduction in coherence between these sites occurs after movement onset and is more marked in the on than in the off dopaminergic medication state. The difference in alpha band coherence on and off medication was found to correlate with the drug related improvement in clinical parameters. Overall, the movement-related behaviour of activities in the alpha band in patients with PD serves to highlight the role of dopamine in modulating large-scale, interregional synchronisation.

Serum and cerebrospinal fluid levels of transthyretin in Lewy body disorders with and without dementia

Parkinson's disease (PD) without (non-demented, PDND) and with dementia (PDD), and dementia with Lewy bodies (DLB) are subsumed under the umbrella term Lewy body disorders (LBD). The main component of the underlying pathologic substrate, i.e. Lewy bodies and Lewy neurites, is misfolded alpha-synuclein (Asyn), and--in particular in demented LBD patients--co-occurring misfolded amyloid-beta (Abeta). Lowered blood and cerebrospinal fluid (CSF) levels of transthyretin (TTR)--a clearance protein mainly produced in the liver and, autonomously, in the choroid plexus--are associated with Abeta accumulation in Alzheimer's disease. In addition, a recent study suggests that TTR is involved in Asyn clearance. We measured TTR protein levels in serum and cerebrospinal fluid of 131 LBD patients (77 PDND, 26 PDD, and 28 DLB) and 72 controls, and compared TTR levels with demographic and clinical data as well as neurodegenerative markers in the CSF. Five single nucleotide polymorphisms of the TTR gene which are considered to influence the ability of the protein to carry its ligands were also analyzed. CSF TTR levels were significantly higher in LBD patients compared to controls. Post-hoc analysis demonstrated that this effect was driven by PDND patients. In addition, CSF TTR levels correlated negatively with CSF Abeta(1-42), total tau and phospho-tau levels. Serum TTR levels did not significantly differ among the studied groups. There were no relevant associations between TTR levels and genetic, demographic and clinical data, respectively. These results suggest an involvement of the clearance protein TTR in LBD pathophysiology, and should motivate to elucidate TTR-related mechanisms in LBD in more detail.

Toxicity of MPTP on neurotransmission in three mouse models of Parkinson's disease

Parkinson's disease (PD) is recognized as the second most common neurodegenerative disorder after Alzheimer's disease. PD is mainly characterized by a selective degeneration of the dopaminergic neurons in the substantia nigra. Also, it is observed imbalances in some nondopaminergic systems, including the serotonergic system. Serotonergic dysfunction appears to play a role in some parkinsonian symptoms, including motor function, L-dopa-induced dyskinesia, mood, psychosis, and constipation. The fact that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes a parkinsonian syndrome was discovered in 1982 and has been used extensively and successfully in various mammalian species, including monkeys and mice, to produce an experimental model of PD. Three common dosing regimens of the MPTP-induced mice model of PD were compared on dopaminergic neurotransmission and serotonin levels in various brain regions. Results showed that tyrosine hydroxylase activity and dopaminergic transporter density were reduced in striatum and substantia nigra of mice and that this reduction was dependent on the cumulative dose of MPTP injected. Furthermore, for the three protocols, a decrease of dopamine (DA) level was observed in striatum, associated with a significant diminution of DA concentration in frontal cortex only for the chronic treatment. Moreover, a decrease of serotonin level was observed in midbrain and hippocampus of acute and sub-acute intoxicated-mice. In all, the results suggested that dosing regimen should be carefully pre-considered. Furthermore, the acute and sub-acute MPTP protocols represent good models of early, subclinical stages of PD, ideal in the development of neuroprotective strategies.

Challenges in diagnosis of young onset Parkinson's disease

Young onset Parkinson's disease patients, typically aged 21 to between 40 and 55, have symptomatology similar to regular onset patients. Despite this, we suspect that physicians take longer to diagnose young onset patients since Parkinson's disease is ruled out due to the younger age. The history prior to diagnosis of 14 young onset patients (within 21 to 45 years of age) was compared with an equivalent number of regular onset patients matched by gender, tremor presence, and Hoehn and Yahr stage. Indeed, a longer period of time was taken to diagnose younger patients with an average of additional 15 months (p<0.001). This trend of older patients being diagnosed sooner was present in the regular onset group analyzed in isolation, but not so for the younger group. The lack of age-dependent variation in time required for diagnosis suggests that Parkinson's disease is not considered at all in the diagnosis for an extended period, accounting for the large difference in prevalence of young onset group to the regular onset group. We also observed a significantly higher number of neurologist visits (p=0.002) and clinical investigations (p<0.001) prior to diagnosis of young-onset patients. Due to the impact of delayed diagnoses on young onset patients and clinical resources, we propose that Parkinson's disease be more actively considered in differential diagnoses of younger patients presenting associated symptoms.

A comparison of LEDD and motor scores following STN-DBS treatment in patient with young onset vs. late onset Parkinson's disease

INTRODUCTION

We compared the role of subthalamic nucleus deep brain stimulation (STN-DBS) in the management of medically refractory idiopathic Parkinson's disease in patients with relatively young onset (<40 years of age) Parkinson's disease (YOPD) and patients with relatively late onset Parkinson's disease (≥ 56 years of age, rLOPD).

METHODS

A total of 33 patients with YOPD (18 patients, median age 32.5 years, range, 20-40 years) and rLOPD (15 patients, median age 58.0 years, range, 56.0-67.0 years) underwent STN-DBS between May 2000 and May 2008. We divided the patients into YOPD and rLOPD as the age of disease onset. The median follow-up period was 43 months (range, 12-95 months). We assessed Hoehn and Yahr stages, activities of daily living, and Unified Parkinson's Disease Rating Scale (UPDRS) motor scales (III) for all patients preoperatively and at six months postoperatively. We measured levodopa equivalent doses (LEDD) and stimulation parameters preoperatively, six months postoperatively, and 12 months postoperatively.

RESULTS

There were no significant differences in UPDRS motor scales between two groups at preoperative and six-month postoperative drug off/stim on, but UPDRS III was lower in rLOPD at six-month postoperative drug on/stim on state. A significant difference was noted in the improvement of UPDRS III between two groups for preoperative drug off and drug on conditions, but no difference was seen between two groups in a comparison of drug off/stim on vs. drug on/stim on conditions. Stimulation parameters and postoperative LEDD were not different between the two groups. Preoperative dyskinesia was more common in YOPD patients and, psychotic problems were more common in rLOPD patients.

CONCLUSIONS

Patients with YOPD and rLOPD exhibited comparable UPDRS motor scores and LEDD six months postoperatively. Levodopa could be prescribed at optimum doses following STN-DBS in patients with YOPD as abnormal movements are better controlled following STN-DBS implantation. Stimulation parameters were not different between the two groups. Our results suggest the age of onset does not influence response to STN-DBS Parkinson's disease patients.

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.

Assessing the utility of Freezing of Gait Questionnaires in Parkinson's Disease

There are currently two validated questionnaires, the Freezing of Gait Questionnaire and the New Freezing of Gait Questionnaire, that are intended to assess the degree of freezing of gait in patients with Parkinson's disease. However, to date no study has attempted to determine whether ratings on these questionnaires accurately reflect the severity (frequency and duration) of actual freezing episodes experienced by patients. We studied twenty-four patients with Parkinson's disease who self-reported significant freezing while in their practically-defined 'off' state. Prior to clinical assessment they completed both freezing of gait questionnaires before being video-recorded while performing a series of timed up-and-go tasks, which incorporated turning, rotating and passing through narrow gaps. The rating of video recordings by two independent observers identified a total of 530 freezing events. The frequency and duration of freezing episodes for each patient were calculated and correlated with questionnaire ratings. Scores on either questionnaire did not correlate with either the frequency or duration of freezing episodes experienced by patients during objective assessment. These results suggest the need to re-evaluate the utility of questionnaires in the assessment of freezing of gait. Furthermore, these results highlight the need for accurate objective methods of identifying freezing events when assessing future clinical interventions aimed at reducing this potentially disabling symptom of Parkinson's disease.

Pedunculopontine nucleus deep brain stimulation in Parkinson's disease

Postural instability and gait difficulty (PIGD) are commonly observed in advanced Parkinson's disease. The neuronal mechanism of PIGD is not fully understood. Dysfunction of the pedunculopontine nucleus (PPN) might be a possible cause of these symptoms. The autopsy studies of subjects with PIGD revealed a neurodegenerative process involving mainly PPN cholinergic neurons. The PPN participates in the locomotion processes by initiation, modulation and execution of stereotyped patterns of movement. The standard neurosurgical treatment of PD is subthalamic deep brain stimulation (STN DBS). Clinical results revealed low efficiency of STN DBS on PIGD. Preliminary results of simultaneous PPN and STN DBS are very promising. Only a few reports have been published until now; a significant improvement of PIGD was observed in both ON and OFF L-dopa states.

The relation between cognition and motor dysfunction in drug-naive newly diagnosed patients with Parkinson's disease

Recent studies have reported cognitive decline to be common in the early phase of Parkinson's disease. Imaging data connect working memory and executive functioning to the dopamine system. It has also been suggested that bradykinesia is the clinical manifestation most closely related to the nigrostriatal lesion. Exploring the relationship between motor dysfunction and cognition can help us find shared or overlapping systems serving different functions. This relationship has been sparsely investigated in population-based studies of untreated Parkinson's disease. The aim of the present study was to investigate the association between motor signs and cognitive performance in the early stages of Parkinson's disease before the intake of dopaminergic medication. Patients were identified in a population-based study of incident cases with idiopathic parkinsonism. Patients with the postural instability and gait disturbances phenotype were compared with patients with the tremor-dominant phenotype on demographics and cognitive measures. Associations between cognitive and motor scores were investigated, with age, education, and sex controlled for. Bradykinesia was associated with working memory and mental flexibility, whereas axial signs were associated with episodic memory and visuospatial functioning. No significant differences in the neuropsychological variables were found between the postural instability and gait disturbances phenotype and the tremor phenotype. Our results indicate a shared system for slow movement and inflexible thinking that may be controlled by a dopaminergic network different from dopaminergic networks involved in tremor and/or rigidity. The association between axial signs and memory and visuospatial function may point to overlapping systems or pathologies related to these abilities.

Sleep disorders in neurodegenerative diseases

The aim of this review is to provide data on sleep disturbances in three categories of neurodegenerative disorders: synucleinopathies, tauopathies, and other diseases (this heterogeneous group includes also spinocerebellar degeneration and amyotrophic lateral sclerosis). Analysing and knowing sleep disorders in neurodegenerative diseases may offer important insights into the pathomechanism of some of these diseases and calls attention to the still insufficiently known 'sleep neurology'. The identification of sleep disorders in some neurodegenerative conditions may make their diagnosis easier and earlier; for example, rapid eye movements sleep behaviour disorder may precede any other clinical manifestation of synucleinopathies by more than 10 years.

Age-specific progression of nigrostriatal dysfunction in Parkinson's disease

OBJECTIVE

To investigate in vivo the impact of age on nigrostriatal dopamine dysfunction in Parkinson's disease (PD).

METHODS

PD patients (n = 78) and healthy control subjects (n = 35) underwent longitudinal positron emission tomography assessments using 3 presynaptic dopamine markers: (1) [¹¹C](±)dihydrotetrabenazine (DTBZ), to estimate the density of the vesicular monoamine transporter type 2; (2) [¹¹C]d-threo-methylphenidate, to estimate the density of the plasma membrane dopamine transporter; and (3) 6-[¹⁸F]-fluoro-L-dopa, to estimate the activity of the enzyme dopa-decarboxylase.

RESULTS

The study comprised 438 PD scans and 241 control scans (679 scans in total). At symptom onset, the loss of putamen DTBZ binding was substantially greater in younger compared to older PD patients (p = 0.015). Remarkably, however, the rate of progression of DTBZ binding loss was significantly slower in younger patients (p < 0.05). The estimated presymptomatic phase of the disease spanned more than 2 decades in younger patients, compared to 1 decade in older patients.

INTERPRETATION

Our results suggest that, compared to older patients, younger PD patients progress more slowly and are able to endure more damage to the dopaminergic system before the first motor symptoms appear. These observations suggest that younger PD patients have more efficient compensatory mechanisms.

The motor phenotype of Parkinson's disease in relation to age at onset

BACKGROUND

Parkinson's disease (PD) is heterogeneous and age at onset may define variation in clinical phenotype. Most previous studies have used various age cut-offs and have been based on clinical case series.

METHODS

We have studied the association between clinical features and age of onset in 358 community-based and regional patients with PD.

RESULTS

Tremor at presentation is twice as common in those with onset over 64 years as compared to those with onset under 45 (early onset PD - EOPD) and becomes more common with increasing age at onset (p values for trend ≤ 0.004). Dystonia affects 60% of those with EOPD, shows a curvilinear relationship with age at onset (cubic versus linear p=0.01) with highest risk in patients whose disease began before 48 years. In this study age at onset was a strong predictor of the development of dyskinesias, with younger age associated with a higher risk of dyskinesias. Following multivariable analysis, allowing for possibly confounding factors (disease duration, L-DOPA dosage, L-DOPA treatment duration) younger age at onset, (less than 55 years) predicted the development of L-DOPA induced dyskinesia (odds ratio <45 years 2.1, 95% CI 1.0, 4.8; odds ratio < 55 years 3.8, 95% CI 1.8, 8.0). Only 2/70 (2.9%) EOPD patients carried pathogenic parkin or PINK1 mutations and the clinical differences between early and late onset disease were not explained by the presence of mutations in these genes.

DISCUSSION

This study highlights the clinical differences between early and late onset PD, which have important implications for diagnosis and management.

Treatment of Parkinson's disease: nanostructured sol-gel silica-dopamine reservoirs for controlled drug release in the central nervous system

Introduction

We have evaluated the use of silica–dopamine reservoirs synthesized by the sol–gel approach with the aim of using them in the treatment of Parkinson’s disease, specifically as a device for the controlled release of dopamine in the striatum. Theoretical calculations illustrate that dopamine is expected to assume a planar structure and exhibit weak interactions with the silica surface.

Methods

Several samples were prepared by varying the wt% of dopamine added during the hydrolysis of tetraethyl orthosilicate. The silica–dopamine reservoirs were characterized by N₂ adsorption, scanning and transmission electron microscopy, and Fourier transform infrared spectroscopy. The in vitro release profiles were determined using ultraviolet visible absorbance spectroscopy. The textural analyses showed a maximum value for the surface area of 620 m²/g nanostructured silica materials. The stability of dopamine in the silica network was confirmed by infrared and ¹³C-nuclear magnetic resonance spectroscopy. The reservoirs were evaluated by means of apomorphine-induced rotation behavior in hemiparkisonian rats.

Results

The in vitro dopamine delivery profiles indicate two regimes of release, a fast and sustained dopamine delivery was observed up to 24 hours, and after this time the rate of delivery became constant. Histologic analysis of formalin-fixed brains performed 24–32 weeks after reservoir implantation revealed that silica–dopamine implants had a reddish-brown color, suggesting the presence of oxidized dopamine, likely caused by the fixation procedure, while implants without dopamine were always translucent.

Conclusion

The major finding of the study was that intrastriatal silica–dopamine implants reversed the rotational asymmetry induced by apomorphine, a dopamine agonist, in hemiparkinsonian rats. No dyskinesias or other motor abnormalities were observed in animals implanted with silica or silica–dopamine.

The genetics of Parkinson disease

Parkinson disease (PD) is the second most common neurodegenerative disorder. In most instances, PD is thought to result from a complex interaction between multiple genetic and environmental factors, though rare monogenic forms of the disease do exist. Mutations in 6 genes (SNCA, LRRK2, PRKN, DJ1, PINK1, and ATP13A2) have conclusively been shown to cause familial parkinsonism. In addition, common variation in 3 genes (MAPT, LRRK2, and SNCA) and loss-of-function mutations in GBA have been well-validated as susceptibility factors for PD. The function of these genes and their contribution to PD pathogenesis remain to be fully elucidated. The prevalence, incidence, clinical manifestations, and genetic components of PD are discussed in this review.

Vulnerability of mesostriatal dopaminergic neurons in Parkinson's disease

The term vulnerability was first associated with the midbrain dopaminergic neurons 85 years ago, before they were identified as monoaminergic neurons, when Foix and Nicolesco (1925) reported the loss of neuromelanin containing neurons in the midbrain of patients with post-encephalitic Parkinson's disease (PD). A few years later, Hassler (1938) showed that degeneration is more intense in the ventral tier of the substantia nigra compacta than in its dorsal tier and the ventral tegmental area (VTA), outlining the concept of differential vulnerability of midbrain dopaminergic (DA-) neurons. Nowadays, we know that other neuronal groups degenerate in PD, but the massive loss of nigral DA-cells is its pathological hallmark, having a pivotal position in the pathophysiology of the disease as it is responsible for the motor symptoms. Data from humans as well as cellular and animal models indicate that DA-cell degeneration is a complex process, probably precipitated by the convergence of different risk factors, mediated by oxidative stress, and involving pathogenic factors arising within the DA-neuron (intrinsic factors), and from its environment and distant interconnected brain regions (extrinsic factors). In light of current data, intrinsic factors seem to be preferentially involved in the first steps of the degenerative process, and extrinsic factors in its progression. A controversial issue is the relative weight of the impairment of common cell functions, such as energy metabolism and proteostasis, and specific dopaminergic functions, such as pacemaking activity and DA handling, in the pathogenesis of DA-cell degeneration. Here we will review the current knowledge about the relevance of these factors at the beginning and during the progression of PD, and in the differential vulnerability of midbrain DA-cells.

Treatment of young-onset Parkinson's disease: role of dopamine receptor agonists

For mostly arbitrary reasons, the term "juvenile parkinsonism" is restricted to patients aged 20 years or younger, and "young-onset PD" (YOPD) is onset between ages 21 and 40 years. Previous studies suggest that YOPD has a slower disease progression and a greater incidence and earlier appearance of L-dopa-induced dyskinesias and motor fluctuations. Therefore, our therapeutic strategies have to respect the fact that YOPD patients face many years of gradual progression of disease and disability, a greater probability for developing various adverse effects of treatment, and worsening of quality of life. As an individually tailored treatment should be our primary goal, we must bear in mind that the needs and expectations of YOPD patients are different from those of their older counterparts. The therapeutic strategy for YOPD patients should include a relatively low threshold for initiation of treatment, and initiating treatment with a dopamine receptor agonist while maintaining an individually adjusted, moderately high threshold for switching to or adding L-dopa in cases where treatment response is suboptimal or if problematic adverse effects develop. It has been shown that some dopamine receptor agonists may also have antidepressive efficacy, thus potentially managing an additional problem associated with PD.

Dissecting the role of the mitochondrial chaperone mortalin in Parkinson's disease: functional impact of disease-related variants on mitochondrial homeostasis

The mitochondrial chaperone mortalin has been linked to neurodegeneration in Parkinson's disease (PD) based on reduced protein levels in affected brain regions of PD patients and its interaction with the PD-associated protein DJ-1. Recently, two amino acid exchanges in the ATPase domain (R126W) and the substrate-binding domain (P509S) of mortalin were identified in Spanish PD patients. Here, we identified a separate and novel variant (A476T) in the substrate-binding domain of mortalin in German PD patients. To define a potential role as a susceptibility factor in PD, we characterized the functions of all three variants in different cellular models. In vitro import assays revealed normal targeting of all mortalin variants. In neuronal and non-neuronal human cell lines, the disease-associated variants caused a mitochondrial phenotype of increased reactive oxygen species and reduced mitochondrial membrane potential, which were exacerbated upon proteolytic stress. These functional impairments correspond with characteristic alterations of the mitochondrial network in cells overexpressing mutant mortalin compared with wild-type (wt), which were confirmed in fibroblasts from a carrier of the A476T variant. In line with a loss of function hypothesis, knockdown of mortalin in human cells caused impaired mitochondrial function that was rescued by wt mortalin, but not by the variants. Our genetic and functional studies of novel disease-associated variants in the mortalin gene define a loss of mortalin function, which causes impaired mitochondrial function and dynamics. Our results support the role of this mitochondrial chaperone in neurodegeneration and underscore the concept of impaired mitochondrial protein quality control in PD.

Altered regulation of CD200 receptor in monocyte-derived macrophages from individuals with Parkinson's disease

Microglia are the representative myeloid cells in the brain, and their over-activation plays an important role in the pathogenesis of Parkinson's disease (PD). Microglia activation is believed to be regulated by the CD200-CD200R signaling. As the peripheral counterpart of microglia, monocyte-derived macrophages (MDMs) share the same progenitor and antigen markers, and they have similar biological behaviors and mirror microglial function in the brain. Here, we studied CD200R expression and its regulation in MDMs from 32 PD cases, 27 age-matched old controls, and 28 young controls. We found that the basal CD200R expression is similar in MDMs from young control, old control and PD patients. However, the induction of CD200R expression in MDMs under various conditions is impaired in the old groups, especially in PD patients. There was a selective decrease in CD200R expression induced by co-culture with dying PC12 cells in MDMs from PD cases, as compared with MDMs from the age-matched controls. We also found that the inducible CD200R expression correlated inversely with the onset age of PD and to tumor necrosis factor-alpha (TNF-alpha) released from MDMs. These results suggest an intrinsic abnormality in the CD200-CD200R signaling in MDMs during aging and, especially, in PD. We speculate that in the PD brain,microglia might undergo abnormalities similar to MDMs.