Risk of dementia in Parkinson's disease: a community-based, prospective study

Effects of ceftriaxone on the behavioral and neuronal changes in an MPTP-induced Parkinson's disease rat model

Hyperactivity of the glutamatergic system is involved in excitotoxicity and neurodegeneration in Parkinson's disease (PD) and treatment with drugs modulating glutamatergic activity may have beneficial effects. Ceftriaxone has been reported to increase glutamate uptake by increasing glutamate transporter expression. The aim of this study was to determine the effects of ceftriaxone on working memory, object recognition, and neurodegeneration in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD rat model. MPTP was stereotaxically injected into the substantia nigra pars compacta (SNc) of male Wistar rats. Then, starting the next day (day 1), the rats were injected daily with either ceftriaxone (200 mg/kg/day, i.p.) or saline for 14 days and underwent a T-maze test on days 8-10 and an object recognition test on days 12-14. MPTP-lesioned rats showed impairments of working memory in the T-maze test and of recognition function in the object recognition test. The treatment of ceftriaxone decreased the above MPTP-induced cognitive deficits. Furthermore, this study provides evidence that ceftriaxone inhibits MPTP lesion-induced dopaminergic degeneration in the nigrostriatal system, microglial activation in the SNc, and cell loss in the hippocampal CA1 area. In conclusion, these data support the idea that hyperactivity of the glutamatergic system is involved in the pathophysiology of PD and suggest that ceftriaxone may be a promising pharmacological tool for the development of new treatments for the dementia associated with PD.

Neuroprotective Potential of Peroxisome Proliferator Activated Receptor- α Agonist in Cognitive Impairment in Parkinson's Disease: Behavioral, Biochemical, and PBPK Profile

Parkinson's disease (PD) is a common neurodegenerative disorder affecting 1% of the population by the age of 65 years and 4-5% of the population by the age of 85 years. PD affects functional capabilities of the patient by producing motor symptoms and nonmotor symptoms. Apart from this, it is also associated with a higher risk of cognitive impairment that may lead to memory loss, confusion, and decreased attention span. In this study, we have investigated the effect of fenofibrate, a PPAR-α agonist in cognitive impairment model in PD. Bilateral intranigral administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (100 µg/1 µL/side) produced significant cognitive dysfunctions. Fenofibrate treatment at 10, 30, and 100 mg/kg for twenty-five days was found to be neuroprotective and improved cognitive impairment in MPTP-induced PD model as evident from behavioral, biochemical (MDA, GSH, TNF-α, and IL-6), immunohistochemistry (TH), and DNA fragmentation (TUNEL positive cells) studies. Further, physiologically based pharmacokinetic (PBPK) modeling study was performed using GastroPlus to characterize the kinetics of fenofibric acid in the brain. A good agreement was found between pharmacokinetic parameters obtained from the actual and simulated plasma concentration-time profiles of fenofibric acid. Results of this study suggest that PPAR-α agonist (fenofibrate) is neuroprotective in PD-induced cognitive impairment.

A pilot evaluation of a brief non-verbal executive function assessment in Parkinson's disease

OBJECTIVE

Screening for cognitive impairment in the clinical or community setting is often hampered by the lack of a suitable assessment that is not overburdened with complex administration and scoring methods. We have developed non-verbal cognitive screening instrument: the Weigl Token Test (WTT) from two existing instruments, the Weigl's Colour-Form Sorting Test (WCFST) and the Token Test. The aim of this investigation is to compare the modified WTT with a battery of 'Gold Standard' cognitive assessments, to determine its utility, sensitivity and specificity as a brief cognitive screen in a cohort of Parkinson's disease (PD) patients.

METHODS

A total of 50 PD patients consented to participate in this investigation. All participants were assessed with a battery of cognitive screening instruments including the WCFST, Mini Mental Status Examination, Addenbrooke's Cognitive Examination--Revised and Delis Kaplan Executive Function Systems. The sensitivity and specificity of the WTT to detect cognitive impairment were based upon psychiatric interview, neuropsychological assessment and application of DSM-IV criteria.

RESULTS

The optimal cut-point of the WTT was 116/120, and its sensitivity and specificity to detect cognitive impairment were 88% and 89%, respectively. The diagnostic accuracy of the WTT as calculated by the area under the receiver operating curve was 0.83 (95% CI 0.76-0.95), suggesting that this instrument has acceptable psychometric properties to discriminate between case and non-cases of cognitive impairment.

CONCLUSIONS

The WTT demonstrated excellent concurrent validity with existing 'Gold Standard' assessments of cognitive impairment. We believe that this instrument will prove to be a valuable additional screening assessment in epidemiological, primary care, specialist mental health or clinical investigations.

Influence of hypertension on neurocognitive domains in nondemented Parkinson's disease patients

Objective. Health comorbidities, particularly cardiovascular risk factors, are well known to pose risks for cognitive decline in older adults. To date, little attention has focused on the impact of these comorbidities on Parkinson's disease (PD). This study examined the prevalence and contribution of comorbidities on cognitive status in PD patients, above and beyond the effects of disease severity. Methods. A cross sectional design was used, including neuropsychological data on 341 PD patients without severe cognitive decline. Comorbidity data were collected via medical chart review. Data were analyzed using a series of multiple hierarchical regressions, controlling for PD-related disease variables. Results. Overall sample characteristics are 69% male, disease duration 9.7 years, Unified Parkinson's Disease Rating Scale 26.4, and age 64.7 years. Hypercholesterolemia (41.6%), hypertension (38.1%), and hypotension (30.2%) were the most reported comorbidities. The presence of hypertension significantly contributed to domains of executive function and verbal memory. The cooccurrence of orthostatic hypotension moderated the relationship between hypertension and executive function. Conclusions. This study on a large cohort of PD patients provides evidence for a detrimental influence of health comorbidities, particularly hypertension, on cognitive domains that have traditionally been conceptualized as being frontally and/or temporally mediated.

Cognitive profiling of Parkinson disease patients with mild cognitive impairment and dementia

BACKGROUND

Prevalence of mild cognitive impairment (MCI) and dementia in Parkinson disease (PD) is variable because different classification criteria are applied and there is lack of consensus about neuropsychological tests and cut-off used for cognitive profiling. Given the important therapeutic consequences for patient management, we aimed at identifying suitable diagnostic cognitive tests and respective screening cut-off values for MCI and dementia in PD (PDD).

METHODS

We evaluated 105 PD patients using an extensive neuropsychological battery categorized as PD without cognitive impairment (PD-CNT) (35%), PD-MCI (47%) and PDD (18%) based on established criteria and calculated Receiver Operating Characteristic (ROC) curves.

RESULTS

We found different sensitivity and specificity among neuropsychological tests in detecting PD-MCI and PDD. In particular performance in attention/set shifting, verbal memory and language abilities, discriminated both PD-MCI and PDD from PD-CNT. Abilities involved mainly in semantic retrieval mechanisms discriminated PD-CNT from PD-MCI but also PD-MCI from PDD. Finally deficits in executive and visual-spatial abilities were only affected in PDD.

CONCLUSION

Our data point to an independent and different load of each test in defining different PD cognitive statuses. These findings can help selection of appropriate cognitive batteries in longitudinal studies and definition of stage-specific therapeutic targets.

Prevalence of Mild Cognitive Impairment Subtypes in Patients with Parkinson’s Disease – Comparison of two Modes of Classification

Early detection of dementia in Parkinson’s disease is becoming increasingly important. The goal of this study was to establish prevalence of mild cognitive impairment subtypes in Parkinson’s disease using two different modes of mild cognitive impairment classification. Categorizing patients into mild cognitive impairment subtypes according to the minimum mode of mild cognitive impairment classification revealed the following results: three patients (2.5 %) were categorized as cognitively healthy, whereas 117 patients (97.5 %) met the criteria for mild cognitive impairment. When categorizing patients according to the mean mode of mild cognitive impairment classification, 41.7 % of the patients were categorized as cognitively healthy, whereas 58.3 % met the criteria for mild cognitive impairment. Frequency of mild cognitive impairment varies substantially, depending on how impairment is defined.

Subjective cognitive decline predicts future deterioration in cognitively normal patients with Parkinson's disease

Increasing evidence suggests that subjective cognitive decline (SCD) is a potential predictor of future cognitive decline or dementia. We investigated whether SCD in patients with Parkinson's disease (PD) is a predictor of future cognitive decline. Forty-six cognitively normal patients with PD were selected using comprehensive neuropsychological tests, and classified depending on the presence (PD-SCD(+), n = 25) or absence of SCD (PD-SCD(-), n = 21). After a mean follow-up of 2.4 years, we repeated the cognitive assessments with the same subjects. The clinical characteristics and cognitive performance of the 2 groups did not differ at baseline. At the follow-up assessment, 11 patients in the PD-SCD(+) group (44.0%) and 2 in the PD-SCD(-) group (9.5%) were diagnosed with mild cognitive impairment (MCI), and the PD-SCD(+) patients showed more rapid decline in semantic fluency and visuospatial memory tasks than those in the PD-SCD(-) group. A multivariate logistic regression analysis showed that presence of SCD (odds ratio, 8.378; 95% confidential interval, 1.472-47.683, p = 0.017) and higher Unified PD Rating Scale motor score of 20 or more (odds ratio, 4.539; 95% confidential interval, 1.004-20.528; p = 0.049) were risk factors for incident MCI. Present results demonstrate that SCD in cognitively normal patients with PD is an independent risk factor for incident MCI and acts as a predictor for future cognitive decline.

Age and duration of inflammatory environment differentially affect the neuroimmune response and catecholaminergic neurons in the midbrain and brainstem

Neuroinflammation and degeneration of ascending catecholaminergic systems occur early in the neurodegenerative process. Age and the duration of a pro-inflammatory environment induced by continuous intraventricular lipopolysaccharide (LPS) differentially affect the expression profile of pro- and anti-inflammatory genes and proteins as well as the number of activated microglia (express major histocompatibility complex II; MHC II) and the integrity and density of ascending catecholaminergic neural systems originating from the locus coeruleus (LC) and substantia nigra pars compacta (SNpc) in rats. LPS infusion increased gene expression and/or protein levels for both pro- and anti-inflammatory biomarkers. Although LPS infusion stimulated a robust increase in IL-1ß gene and protein expression, this increase was blunted with age. LPS infusion also increased the density of activated microglia cells throughout the midbrain and brainstem. Corresponding to the development of a pro-inflammatory environment, LC and SNpc neurons immunopositive for tyrosine-hydroxylase (the rate-limiting synthetic enzyme for dopamine and norepinephrine) decreased in number, along with a decrease in tyrosine-hydroxylase gene expression in the midbrain and/or brainstem region. Our data support the concept that continuous exposure to a pro-inflammatory environment drives exaggerated changes in the production and release of inflammatory mediators that interact with age to impair functional capacity of the SNpc and LC.

Predictors of cognitive decline in the early stages of Parkinson's disease: a brief cognitive assessment longitudinal study

Our objectives were to perform a longitudinal assessment of mental status in early stage Parkinson's disease (PD) patients, with brief neuropsychological tests, in order to find predictive factors for cognitive decline. Sixty-one, early stage, and nondemented patients were assessed twice, over a 2-year interval, with a global cognitive test (mini-mental state examination (MMSE)) and a frontal function test (frontal assessment battery (FAB)) and motor function scales. Dementia and hallucinations were diagnosed according to the DSM-IV criteria. Cognitive function scores did not decrease significantly, except for FAB lexical fluency score. Four patients presented with dementia at followup. The MMSE score below cut-off, worse gait dysfunction, the nontremor motor subtype, and hallucinations were significantly related to dementia. Rigidity and speech dysfunction were related to dementia and a decrease in FAB scores. We can conclude that decline in the MMSE and FAB scores is small and heterogeneous in the early stages of PD. Scores below cut-off in the MMSE could be helpful to predict dementia. Nontremor motor deficits could be predictive factors for frontal cognitive decline and dementia.

Five-year fracture risk estimation in patients with Parkinson's disease

BACKGROUND

Previous studies have shown that patients with Parkinson's disease (PD) are at increased risk of fractures. However, no specific prediction model for fracture estimation among PD patients is currently available. Therefore, the aim of this study was to develop a simple score for estimating the 5-year osteoporotic and hip fracture risks among patients with PD.

METHODS

The U.K. Clinical Practice Research Datalink (1987-2011) was used to identify incident PD patients. Cox proportional-hazards models were used to calculate the 5-year risks of osteoporotic and hip fracture among PD patients. The regression model was fitted with various risk factors for fracture and the final Cox model was converted into integer risk scores.

RESULTS

We identified 4411 incident PD patients without a history of osteoporotic treatment. The 5-year risks of osteoporotic and hip fracture were plotted in relation to the risk score. Risk scores increased with age, female gender, history of renal disease and history of dementia. The C-statistic, which is a parameter to test the internal validity of the model, was reasonable for the prediction of osteoporotic fracture (0.69) and hip fracture (0.73).

CONCLUSION

In this study, we developed a simple model to estimate 5-year fracture risk among incident PD patients. It may be useful in daily practice after external validation.

New pharmacological options for treating advanced Parkinson's disease

BACKGROUND

Parkinson's disease (PD) affects about 1% of the over 60 population and is characterized by a combination of motor symptoms (rest tremor, bradykinesia, rigidity, postural instability, stooped posture and freezing of gait [FoG]) and non-motor symptoms (including psychiatric and cognitive disorders). Given that the loss of dopamine in the striatum is the main pathochemical hallmark of PD, pharmacological treatment of the disease has focused on restoring dopaminergic neurotransmission and thus improving motor symptoms. However, the currently licensed medications have several major limitations. Firstly, dopaminergic medications modulate all the key steps in dopamine transmission other than the most powerful determinant of extracellular dopamine levels: the activity of the presynaptic dopamine transporter. Secondly, other monoaminergic neurotransmission systems (ie noradrenergic, cholinergic and glutamatergic systems are altered in PD and may be involved in a variety of motor and non-motor symptoms. Thirdly, today's randomized clinical trials are primarily designed to assess the efficacy and safety of treatments for motor fluctuations and dyskinesia. Fourthly, there is a need for disease- modifying treatments (DMTs) that slow disease progression and reduce the occurrence of the very disabling disorders seen in late-stage PD.

OBJECTIVE

To systematically review a number of putative pharmacological options for treating the main impairments in late-stage PD (ie gait disorders, cognitive disorders and behavioural disorders such as apathy).

METHODS

We searched the PubMed database up until July 2013 with logical combinations of the following search terms: "Parkinson's disease", "gait", "cognition", "apathy", "advanced stage", "modulation", "noradrenergic", "cholinergic", "glutamatergic" and "neurotransmission".

RESULTS

In patients undergoing subthalamic nucleus stimulation, the potentiation of noradrenergic and dopaminergic transmission by methylphenidate improves gait and FoG and may relieve apathy. However, the drug failed to improve cognition in this population. Potentiation of the cholinergic system by acetylcholinesterase inhibitors (which are licensed for use in dementia) may reduce pre-dementia apathy and falls. Modulation of the glutamatergic system by an N-methyl-D-aspartate receptor antagonist did not improve gait and dementia but may have reduced axial rigidity. A number of putative DMTs have been reported.

DISCUSSION

Novel therapeutic strategies should seek to reduce the appearance of the very disabling disorders observed in late-stage PD. Dopamine and/or noradrenaline transporter inhibitors, anticholinesterase inhibitors, Peroxisome-proliferator-activated-receptor-agonists and iron chelators should at least be investigated as putative DMTs by applying a delayed-start clinical trial paradigm to a large population

CONCLUSIONS

There is a need for more randomized clinical trials of treatments for late-stage PD.

Demographic and motor features associated with the occurrence of neuropsychiatric and sleep complications of Parkinson's disease

OBJECTIVE

To determine whether four key neuropsychiatric and sleep related features associated with Parkinson's disease (PD) are associated with the motor handicap and demographic data.

BACKGROUND

The growing number of recognised non-motor features of PD makes routine screening of all these symptoms impractical. Here, we investigated the hypothesis that standard demographic data and the routine assessment of motor signs is associated with the presence of dementia, psychosis, clinically probable rapid eye movement (REM) sleep behavior disorder (cpRBD) and restless legs syndrome (RLS).

METHODS

775 patients with PD underwent standardised assessment of motor features and the presence of dementia, psychosis, cpRBD and RLS. A stepwise feature elimination procedure with fitted logistic regression models was applied to identify which/if any combination of demographic and motor factors is associated with each of the four studied non-motor features. A within-study out-of-sample estimate of the power of the predicted values of the models was calculated using standard evaluation procedures.

RESULTS

Age and Hoehn&Yahr (H&Y) stage were strongly associated with the presence of dementia (p value<0.001 for both factors in the final selected model) while a combination of age, disease duration, H&Y stage, dopamine agonists and catechol-O-methyltransferase (COMT) inhibitors was associated with the presence of psychosis. Disease duration and H&Y stage were the significant indicators of cpRBD, and the lack of significant motor asymmetry was the only significant feature associated with RLS-type symptoms but the evidence of association was weak.

CONCLUSIONS

Demographic and motor features routinely collected in patients with PD can estimate the occurrence of neuropsychiatric and sleep-related features of PD.

Risk of fracture in patients with Parkinson's disease

The aim of the study was to determine fracture risk in incident Parkinson's disease (PD) patients. This study showed that fracture risk assessment may be indicated among patients with PD, in particular when they have recently used selective serotonin re-uptake inhibitors or high-dose antipsychotics, or have a history of fracture, falling, low body mass index (BMI) or renal disease.

INTRODUCTION

PD is a movement disorder associated with falling and detrimental effects on bone. Both are recognized risk factors for fracture. Therefore, the aim was to determine fracture risk in incident PD patients stratified by treatment, severity, duration of disease and related comorbidities.

METHODS

We conducted a retrospective cohort study using the UK General Practice Research Database (1987-2011). Each PD patient was matched by age, sex, calendar time and practice to a control patient without history of PD.

RESULTS

We identified 4,687 incident PD patients. Compared to controls, a statistically significant increased risk was observed for any fracture (adjusted hazard ratio [AHR], 1.89; 95 % confidence interval [CI], 1.67-2.14), osteoporotic fracture (AHR, 1.99; 95 % CI, 1.72-2.30) and hip fracture (AHR 3.08; 95 % CI, 2.43-3.89). Fracture risk further increased with history of fracture, falling, low BMI, renal disease, antidepressant use and use of high-dose antipsychotics.

CONCLUSION

This study showed that incident PD patients have a statistically significant increased risk of fracture. Therefore, fracture risk assessment may be indicated among PD patients, who, besides the general risk factors for fracture, like increasing age and female gender, have recently used selective serotonin re-uptake inhibitors or high-dose antipsychotics or have a history of fracture, falling, low BMI or renal disease.

High-resolution tracking of motor disorders in Parkinson's disease during unconstrained activity

Parkinson's disease (PD) can present with a variety of motor disorders that fluctuate throughout the day, making assessment a challenging task. Paper-based measurement tools can be burdensome to the patient and clinician and lack the temporal resolution needed to accurately and objectively track changes in motor symptom severity throughout the day. Wearable sensor-based systems that continuously monitor PD motor disorders may help to solve this problem, although critical shortcomings persist in identifying multiple disorders at high temporal resolution during unconstrained activity. The purpose of this study was to advance the current state of the art by (1) introducing hybrid sensor technology to concurrently acquire surface electromyographic (sEMG) and accelerometer data during unconstrained activity and (2) analyzing the data using dynamic neural network algorithms to capture the evolving temporal characteristics of the sensor data and improve motor disorder recognition of tremor and dyskinesia. Algorithms were trained (n=11 patients) and tested (n=8 patients; n=4 controls) to recognize tremor and dyskinesia at 1-second resolution based on sensor data features and expert annotation of video recording during 4-hour monitoring periods of unconstrained daily activity. The algorithms were able to make accurate distinctions between tremor, dyskinesia, and normal movement despite the presence of diverse voluntary activity. Motor disorder severity classifications averaged 94.9% sensitivity and 97.1% specificity based on 1 sensor per symptomatic limb. These initial findings indicate that new sensor technology and software algorithms can be effective in enhancing wearable sensor-based system performance for monitoring PD motor disorders during unconstrained activities.

Demography, diagnostics, and medication in dementia with Lewy bodies and Parkinson's disease with dementia: data from the Swedish Dementia Quality Registry (SveDem)

INTRODUCTION

Whether dementia with Lewy bodies (DLB) and Parkinson's disease with dementia (PDD) should be considered as one entity or two distinct conditions is a matter of controversy. The aim of this study was to compare the characteristics of DLB and PDD patients using data from the Swedish Dementia Quality Registry (SveDem).

METHODS

SveDem is a national Web-based quality registry initiated to improve the quality of diagnostic workup, treatment, and care of patients with dementia across Sweden. Patients with newly diagnosed dementia of various types were registered in SveDem during the years 2007-2011. The current cross-sectional report is based on DLB (n = 487) and PDD (n = 297) patients. Demographic characteristics, diagnostic workup, Mini-Mental State Examination (MMSE) score, and medications were compared between DLB and PDD groups.

RESULTS

No gender differences were observed between the two study groups (P = 0.706). PDD patients were significantly younger than DLB patients at the time of diagnosis (74.8 versus 76.8 years, respectively; P < 0.001). A significantly higher prevalence of patients with MMSE score ≤24 were found in the PDD group (75.2% versus 67.6%; P = 0.030). The mean number of performed diagnostic modalities was significantly higher in the DLB group (4.9 ± 1.7) than in the PDD group (4.1 ± 1.6; P < 0.001). DLB patients were more likely than PDD patients to be treated with cholinesterase inhibitors (odds ratio = 2.5, 95% confidence interval = 1.8-3.5), whereas the use of memantine, antidepressants, and antipsychotics did not differ between the groups.

CONCLUSION

This study demonstrates several differences in the dementia work-up between DLB and PDD. The onset of dementia was significantly earlier in PDD, while treatment with cholinesterase inhibitors was more common in DLB patients. Severe cognitive impairment (MMSE score ≤24) was more frequent in the PDD group, whereas more diagnostic tests were used to confirm a DLB diagnosis. Some similarities also were found, such as gender distribution and use of memantine, antidepressants, and antipsychotics drugs. Further follow-up cost-effectiveness studies are needed to provide more evidence for workup and treatment guidelines of DLB and PDD.

Prevalence of Parkinson disease and Parkinson disease dementia in community nursing homes

OBJECTIVE

To estimate the prevalence of Parkinson disease (PD) and Parkinson disease dementia (PDD) in community nursing homes. To estimate how many residents who meet criteria for PDD have been diagnosed with PDD and prescribed a Federal Drug Administration (FDA)-approved treatment for PDD.

SETTING

Three private Saint Louis metropolitan area nursing homes.

PARTICIPANTS

Fifty-five residents with a chart diagnosis of PD from a total of 714 residents were identified. Sixteen subjects or families did not give consent and two were excluded from the study because advanced stage of the illness impaired evaluation. Thirty-seven subjects with an established diagnosis of PD participated in the study.

DESIGN AND MEASUREMENTS

A chart review was used to identify the study sample: residents with an established diagnosis of PD. Consent was obtained from the nursing home administration, families or guardians, and the residents themselves (where applicable). Study data were obtained from review of residents' medical charts, family/caregiver interview, resident interview, resident cognitive testing (Mini-Mental State Examination, clock drawing test), and resident depression assessment (15-item Geriatric Depression Scale). Diagnosis of PDD was defined using existing literature and described below. Data were analyzed using SPSS version 15.

RESULT

Of the 714 nursing home residents, 55 (7.7%) met criteria for PD. Of these, 37 participated in the study and 18 (48.6%) met criteria for PDD. None were diagnosed with PDD in the charts and 11.1% (2 of 18) were on FDA-approved treatment.

CONCLUSION

In this sample of nursing home residents, the prevalence of PD was 7.7% and the overall prevalence of PDD was 3.7%. PDD remains an unrecognized entity in the nursing home setting. Close to half (48.65%) of nursing home residents with PD may have PDD at any given time and they remain undiagnosed and largely undertreated.

Differential effects of duration and age on the consequences of neuroinflammation in the hippocampus

The current study investigated the hypothesis that the duration of the proinflammatory environment plays a critical role in the brain's response that results in negative consequences on cognition, biochemistry, and pathology. Lipopolysaccharide or artificial cerebrospinal fluid was slowly (250 ηg/h) infused into the fourth ventricle of young (3-month-old), adult (9-month-old), or aged (23-month-old) male F-344 rats for 21 or 56 days. The rats were then tested in the water pool task and endogenous hippocampal levels of pro- and anti-inflammatory proteins and genes and indicators of glutamatergic function were determined. The duration of the lipopolysaccharide infusion, compared with the age of the rat, had the greatest effect on (1) spatial working memory; (2) the density and distribution of activated microglia within the hippocampus; and (3) the cytokine protein and gene expression profiles within the hippocampus. The duration- and age-dependent consequences of neuroinflammation might explain why human adults respond positively to anti-inflammatory therapies and aged humans do not.

Cerebral white matter hyperintensity in Parkinson's disease: a major risk factor for mild cognitive impairment

BACKGROUND

Mild cognitive impairment (MCI) and dementia contribute to a poor quality of life among patients with PD. The influence of cerebral ischemia as a risk factor for MCI in PD has not been adequately investigated. To address this issue, we examined the influence of the volume and distribution of white matter hyperintensity (WMH) as a risk factor for MCI in early PD.

METHODS

Prospective study of patients with early idiopathic PD. All patients had baseline MRI-FLAIR, clinical assessment and detailed neuropsychological evaluation. Data on demographics, vascular risk factors, cognitive performance and WMH volumes were analyzed.

RESULTS

91 patients; mean age 64.9 years, mean education of 10.5 years. 24 patients fulfilled the Movement Disorder Society criteria for MCI and were classified as PD-MCI while the rest were classified as PD with no cognitive impairment (PD-NCI). Patients with PD-MCI and PD-NCI did not differ in Hoehn & Yahr staging. PD-MCI patients had a higher prevalence of diabetes mellitus, hypertension and hyperlipidemia. PD-MCI patients had significantly greater volume of periventricular (6.04 ml vs. 2.66 ml, p = 0.001) and deep subcortical WMH (2.16 vs.1.44, p = 0.002). Regional WMH was significantly greater among PD-MCI in the frontal, parietal and occipital regions. Logistic regression analyses demonstrated WMH to be associated with PD-MCI independent of age, education, and vascular risk factors. Increasing WMH volume was associated with lower performance on executive function, memory and language.

CONCLUSIONS

WMH is an important risk factor for PD-MCI independent of vascular risk factors. PD patients with WMH should be regularly screened for MCI.

Cognitive profiles of patients with mild cognitive impairment or dementia in Alzheimer's or Parkinson's disease

Background

Alzheimer's disease (AD) and Parkinson's disease (PD) are associated with severe cognitive decline, but it is still unclear to what extent they become functionally more similar over time.

Methods

We compared amnestic mild cognitively impaired (aMCI; n = 29) patients to mild cognitively impaired (MCI) PD patients (n = 25), and patients with AD (n = 34) to patients with PD dementia (PDD; n = 15) with respect to cognitive functioning and mood.

Results

aMCI patients were impaired in episodic memory, while MCI PD patients showed deficits in visuoconstruction and attention. AD and PDD patients showed comparable deficits on tests for language, attention and visuoconstruction. However, unlike PDD patients but similar to aMCI patients, AD patients showed a characteristic memory impairment, especially commission errors on recognition tasks, whereas PDD patients scored higher on the depressive mood questionnaire.

Conclusions

In advanced stages of both diseases, the pattern of functional deficits associated with parietal and temporal lobe functions (attention, visuoconstruction and language) is similar. However, specific differences, already present in the early stage (recognition errors in AD, associated with mediobasal temporal lobe functioning, and depressed mood in PDD, associated with non-motor basal ganglia loops), are also observed in the late stage.

Differential diagnosis tool for parkinsonian syndrome using multiple structural brain measures

Clinical differentiation of parkinsonian syndromes such as the Parkinson variant of multiple system atrophy (MSA-P) and cerebellar subtype (MSA-C) from Parkinson's disease is difficult in the early stage of the disease. To identify the correlative pattern of brain changes for differentiating parkinsonian syndromes, we applied discriminant analysis techniques by magnetic resonance imaging (MRI). T1-weighted volume data and diffusion tensor images were obtained by MRI in eighteen patients with MSA-C, 12 patients with MSA-P, 21 patients with Parkinson's disease, and 21 healthy controls. They were evaluated using voxel-based morphometry and tract-based spatial statistics, respectively. Discriminant functions derived by step wise methods resulted in correct classification rates of 0.89. When differentiating these diseases with the use of three independent variables together, the correct classification rate was the same as that obtained with step wise methods. These findings support the view that each parkinsonian syndrome has structural deviations in multiple brain areas and that a combination of structural brain measures can help to distinguish parkinsonian syndromes.

Diagnostic and screening power of neuropsychological testing in detecting mild cognitive impairment in Parkinson's disease

Prevalence of mild cognitive impairment (MCI) in Parkinson's disease (PD) is variable likely due to methodological differences in classification criteria and lack of consensus about neuropsychological tests used for cognitive profiling. The main objective of our study was to identify the most suitable neuropsychological tests and determine their screening and diagnostic cutoff scores for PD-MCI. A series of 104 consecutive PD patients performed an extensive neuropsychological evaluation. Individual test values were converted into Z-scores using relative published normative data. According to published criteria, PD patients were categorized as PD-CNT (PD without cognitive impairment), PD-MCI (patients performing -1.5 SDs below the mean score in at least one cognitive domain), and PDD. We used receiver operating characteristic (ROC) curves and K-means clustering analyses to calculate the best discriminating power of each neuropsychological tests in detecting PD-MCI. PD patients were categorized as follows: 55 PD-CNT (53 %), 34 PD-MCI (33 %), and 15 PDD (14 %). PD-MCI had lower education, longer disease duration and greater frequency of hallucinations than PD-CNT. We found that only the Trail Making test, Rey-Osterrieth Complex Figure Test (ROCF) copy, Frontal Assessment Battery (FAB), Digit Span Backward, and Rey's word auditory verbal learning test (RVLT) immediate recall reached significant screening and diagnostic validity in predicting PD-MCI (AUC 0.705-0.795) with cutoff scores calculated by ROC analyses lying within normal range for normative data. Specific neuropsychological tests covering verbal memory, attention/set-shifting, and visual-spatial deficits are the best predictors of MCI in PD if valid cutoff scores are used. These results have consequences for cognitive diagnosis and potentially in establishing the rate of PD cognitive decline.

Neocortex and allocortex respond differentially to cellular stress in vitro and aging in vivo

In Parkinson’s and Alzheimer’s diseases, the allocortex accumulates aggregated proteins such as synuclein and tau well before neocortex. We present a new high-throughput model of this topographic difference by microdissecting neocortex and allocortex from the postnatal rat and treating them in parallel fashion with toxins. Allocortical cultures were more vulnerable to low concentrations of the proteasome inhibitors MG132 and PSI but not the oxidative poison H₂O₂. The proteasome appeared to be more impaired in allocortex because MG132 raised ubiquitin-conjugated proteins and lowered proteasome activity in allocortex more than neocortex. Allocortex cultures were more vulnerable to MG132 despite greater MG132-induced rises in heat shock protein 70, heme oxygenase 1, and catalase. Proteasome subunits PA700 and PA28 were also higher in allocortex cultures, suggesting compensatory adaptations to greater proteasome impairment. Glutathione and ceruloplasmin were not robustly MG132-responsive and were basally higher in neocortical cultures. Notably, neocortex cultures became as vulnerable to MG132 as allocortex when glutathione synthesis or autophagic defenses were inhibited. Conversely, the glutathione precursor N-acetyl cysteine rendered allocortex resilient to MG132. Glutathione and ceruloplasmin levels were then examined in vivo as a function of age because aging is a natural model of proteasome inhibition and oxidative stress. Allocortical glutathione levels rose linearly with age but were similar to neocortex in whole tissue lysates. In contrast, ceruloplasmin levels were strikingly higher in neocortex at all ages and rose linearly until middle age. PA28 levels rose with age and were higher in allocortex in vivo, also paralleling in vitro data. These neo- and allocortical differences have implications for the many studies that treat the telencephalic mantle as a single unit. Our observations suggest that the topographic progression of protein aggregations through the cerebrum may reflect differential responses to low level protein-misfolding stress but also reveal impressive compensatory adaptations in allocortex.

Diffusion tensor imaging reveals white matter changes associated with cognitive status in patients with Parkinson's disease

Objective : Cognitive deficit and white matter alteration relationships in Parkinson's disease (PD) were investigated. Methods : Comparison of 64 patients with PD (M:F, 34:30; 64.4 ± 10.4 years) classified as cognitively normal (PD-CogNL, n = 24), mild cognitive impairment (PD-MCI, n = 30), and dementia (PD-D, n = 10) with 21 healthy participants (M:F, 10:11; 60.1 ± 13.6 years) was conducted using white matter fractional anisotropy (FA), region-of-interest analysis, and diffusion tensor imaging. Results : The PD-D and PD-MCI exhibited higher Unified Parkinson's Disease Rating Scale motor scores (P < .001; P < .01) and Hoehn-Yahr stages (P < .001; P < .05) and FA reductions in left frontal/right temporal white matter and bilateral anterior cingulated bundles. Largest FA reductions occurred in PD-D left anterior cingulated bundle and corpus callosum splenium. Disease durations of PD-D = 6.8 ± 6.86, PD-MCI = 5.1 ± 2.9, and PD-CogNL = 4.7 ± 3.4 years, suggesting progressive deterioration. Conclusions : Cerebral white matter deterioration may underlie progressive cognitive impairment in PD.

The cerebellum in Parkinson's disease

Parkinson’s disease is a chronic progressive neurodegenerative disorder characterized by resting tremor, slowness of movements, rigidity, gait disturbance and postural instability. Most investigations on Parkinson’s disease focused on the basal ganglia, whereas the cerebellum has often been overlooked. However, increasing evidence suggests that the cerebellum may have certain roles in the pathophysiology of Parkinson’s disease. Anatomical studies identified reciprocal connections between the basal ganglia and cerebellum. There are Parkinson’s disease–related pathological changes in the cerebellum. Functional or morphological modulations in the cerebellum were detected related to akinesia/rigidity, tremor, gait disturbance, dyskinesia and some non-motor symptoms. It is likely that the major roles of the cerebellum in Parkinson’s disease include pathological and compensatory effects. Pathological changes in the cerebellum might be induced by dopaminergic degeneration, abnormal drives from the basal ganglia and dopaminergic treatment, and may account for some clinical symptoms in Parkinson’s disease. The compensatory effect may help maintain better motor and non-motor functions. The cerebellum is also a potential target for some parkinsonian symptoms. Our knowledge about the roles of the cerebellum in Parkinson’s disease remains limited, and further attention to the cerebellum is warranted.

Prefrontal dopamine signaling and cognitive symptoms of Parkinson's disease

Cognitive dysfunction is a common symptom of Parkinson's disease (PD) that causes significant morbidity and mortality. The severity of these symptoms ranges from minor executive symptoms to frank dementia involving multiple domains. In the present review, we will concentrate on the aspects of cognitive impairment associated with prefrontal dopaminergic dysfunction, seen in non-demented patients with PD. These symptoms include executive dysfunction and disorders of thought, such as hallucinations and psychosis. Such symptoms may go on to predict dementia related to PD, which involves amnestic dysfunction and is typically seen later in the disease. Cognitive symptoms are associated with dysfunction in cholinergic circuits, in addition to the abnormalities in the prefrontal dopaminergic system. These circuits can be carefully studied and evaluated in PD, and could be leveraged to treat difficult clinical problems related to cognitive symptoms of PD.

Cognitive profile of the earliest stage of dementia in Parkinson's disease

Recently, a strong interest has emerged in recognizing Parkinson's disease dementia (PDD) at a very early stage. However, the specific profile of the earliest stages of PDD is still unclear and a matter of considerable controversy. The objective of this study was to find out early neuropsychological markers for progression of dementia in this population. Fifty-eight patients with PDD were divided into 2 subgroups on the basis of the Mini-Mental State Examination: very mild and mild. The comparison with 26 normal controls shows that very mild PDD had deficits on attention/executive functions, naming, visuospatial/constructional abilities and retrieval of the episodic memory. Patients with mild PDD showed additional deficits on coding of episodic memory. Moreover, we found that in this early stage of PDD, the progression of dementia is mainly related to deterioration of attention/executive functions as well as retrieval and coding of episodic memory.

Cognitive impairment in patients with Parkinson's disease: diagnosis, biomarkers, and treatment

Dementia is one of the most common and important aspects of Parkinson's disease and has consequences for patients and caregivers, and has health-related costs. Mild cognitive impairment is also common and frequently progresses to dementia. The underlying mechanisms of dementia associated with Parkinson's disease are only partly known and no mechanism-based treatments are available. Both dysmetabolism of α-synuclein and amyloid-protein and cholinergic deficits contribute to cognitive impairment in Parkinson's disease, and preliminary findings show that imaging and neurophysiological and peripheral biomarkers could be useful in diagnosis and prognosis. Rivastigmine is the only licensed treatment for dementia in Parkinson's disease, but emerging evidence suggests that memantine might also be useful. Whether these or other treatments can delay the progression from mild cognitive impairment to dementia in Parkinson's disease is a key research question.

Serum epidermal growth factor predicts cognitive functions in early, drug-naive Parkinson's disease patients

Epidermal growth factor (EGF) has been proposed as a candidate biomarker for cognitive impairment in Parkinson's disease (PD). We aimed to assess the relationship between serum EGF and cognitive functions in early, drug-naive PD patients and evaluate the predictive value of EGF on cognitive functions in a 2-year follow-up study. Serum EGF was measured in 65 early, drug-naive PD patients, that underwent a comprehensive neuropsychological battery. Motor symptoms were assessed by means of the Unified Parkinson's Disease Rating Scale, Part III (UPDRS-III). Neuropsychological evaluation was repeated after 2 years. Spearman's rank correlation was used to assess the relationship between serum EGF levels and neuropsychological variables. Linear regression analysis was used to evaluate the relationship between EGF and neuropsychological scores as well as other variables (age, gender, UPDRS-III, levodopa equivalent dose, and type of treatment at follow-up) potentially affecting cognitive performance. Variation over time in cognitive scores was analyzed using repeated-measures ANOVA. At baseline, EGF was the only significant variable associated with performance on semantic fluency (R (2) = 0.131; p = 0.005). EGF levels (p = 0.025), together with UPDRS-III (p = 0.009) and age (p = 0.011), were associated with performance on frontal assessment battery (R (2) = 0.260). At 2-year follow-up, EGF was the only significant variable to predict performance on semantic fluency (R (2) = 0.147; p = 0.025) and color naming task of Stroop color-word test (R (2) = 0.121; p = 0.044). Serum EGF levels are related to frontal and temporal cognitive functions in early, drug-naive PD patients and predict performance on frontal and posterior cognitive functions at 2-year follow-up. EGF is proposed as a potential serum biomarker for early cognitive impairment in PD.

Disease progress and response to treatment as predictors of survival, disability, cognitive impairment and depression in Parkinson's disease

AIM

To describe the time to clinical events (death, disability, cognitive impairment and depression) in Parkinson's disease using the time course of disease status and treatment as explanatory variables.

METHODS

Disease status based on the Unified Parkinson's Disease Rating Scale (UPDRS) and the time to clinical outcome events were obtained from 800 patients who initially had early Parkinson's disease. Parametric hazard models were used to describe the time to the events of interest.

RESULTS

Time course of disease status (severity) was an important predictor of clinical outcome events. There was an increased hazard ratio for death 1.4 (95% CI 1.31, 149), disability 2.75 (95% CI 2.30, 3.28), cognitive impairment 4.35 (95% CI 1.94, 9.74), and depressive state 1.43 (95% CI 1.26, 1.63) with each 10 unit increase of UPDRS. Age at study entry increased the hazard with hazard ratios of 49.1 (95% CI 8.7, 278) for death, 4.76 (95% CI 1.10, 20.6) for disability and 90.0 (95% CI 63.3-128) for cognitive impairment at age 60 years. Selegiline treatment had independent effects as a predictor of death at 8 year follow-up with a hazard ratio of 2.54 (95% CI 1.51, 4.25) but had beneficial effects on disability with a hazard ratio of 0.363 (95% CI 0.132, 0.533) and depression with a hazard ratio of 0.372 (95% CI 0.12, 0.552).

CONCLUSIONS

Our findings show that the time course of disease status based on UPDRS is a much better predictor of future clinical events than any baseline disease characteristic. Continued selegiline treatment appears to increase the hazard of death.

Nonmotor symptoms in Parkinson's disease in 2012: relevant clinical aspects

Nonmotor symptoms (NMSs) of Parkinson's disease (PD) are common, but they are often underrecognized in clinical practice, because of the lack of spontaneous complaints by the patients, and partly because of the absence of systematic questioning by the consulting physician. However, valid specific instruments for identification and assessment of these symptoms are available in 2012. The administration of the self-completed screening tool, NMSQuest, associated with questioning during the consultation, improves the diagnosis of NMSs. NMSs play a large role in degradation of quality of life. More relevant NMSs are described in this review, mood disorders, impulse control disorders, cognitive deficits, hallucinations, pain, sleep disorders, and dysautonomia.

Cognitive impairments in Parkinson's disease

OBJECTIVE

Dementia and cognitive impairment (CI) are common in Parkinson's disease (PD) and have important clinical consequences. We explored the prognostic factors for CI in patients with PD.

METHODS

A total of 102 patients with PD in Xuan wu hospital and Qian dongnan People's Hospital from 2005 to 2010 were included in this study. All patients underwent clinical and neurological assessments. Relevant demographic and performance parameters were analysed to determine variables that may be independently associated with the progression of CI.

RESULTS

In the 6-month follow-up group, CI progressed in three out of 58 cases (5%): two cases progressed from mild CI (MiCI) to moderate CI (MoCI), and one case from MoCI to dementia. In the six-month-to-two-year follow-up group, seven out of 46 cases (15%) worsened: one case developed MiCI, three cases progressed from MiCI to MoCI and three other cases from MoCI to dementia. In the two-to-five-year group, 20 out of 44 cases (45%) worsened with one case developing MiCI, 14 cases progressing from MiCi to MoCI and five cases from MoCI to dementia. Compared with other patients, those with worsening of CI symptoms were significantly older in the two-to-five-year group. Progression of CI was also associated with age at onset and initial staging of PD.

CONCLUSIONS

Advanced age, late onset of disease and severity of PD are the predictive factors for the progression of CI in PD. The highest probability of progression of CI is in patients with initial severe impairments of visuospatial function.

Basal ganglia circuits changes in Parkinson's disease patients

Functional changes in basal ganglia circuitry are responsible for the major clinical features of Parkinson's disease (PD). Current models of basal ganglia circuitry can only partially explain the cardinal symptoms in PD. We used functional MRI to investigate the causal connectivity of basal ganglia networks from the substantia nigra pars compacta (SNc) in PD in the movement and resting state. In controls, SNc activity predicted increased activity in the supplementary motor area, the default mode network, and dorsolateral prefrontal cortex, but, in patients, activity predicted decreases in the same structures. The SNc had decreased connectivity with the striatum, globus pallidus, subthalamic nucleus, thalamus, supplementary motor area, dorsolateral prefrontal cortex, insula, default mode network, temporal lobe, cerebellum, and pons in patients compared to controls. Levodopa administration partially normalized the pattern of connectivity. Our findings show how the dopaminergic system exerts influences on widespread brain networks, including motor and cognitive networks. The pattern of basal ganglia network connectivity is abnormal in PD secondary to dopamine depletion, and is more deviant in more severe disease. Use of functional MRI with network analysis appears to be a useful method to demonstrate basal ganglia pathways in vivo in human subjects.

Emerging roles of microglial activation and non-motor symptoms in Parkinson's disease

Recent data has indicated that the traditional view of Parkinson's disease (PD) as an isolated disorder of the nigrostriatal dopaminergic system alone is an oversimplification of its complex symptomatology. Aside from classical motor deficits, various non-motor symptoms including autonomic dysfunction, sensory and cognitive impairments as well as neuropsychiatric alterations and sleep disturbances are common in PD. Some of these non-motor symptoms can even antedate the motor problems. Many of them are associated with extranigral neuropathological changes, such as extensive α-synuclein pathology and also neuroinflammatory responses in specific brain regions, i.e. microglial activation, which has been implicated in several aspects of PD pathogenesis and progression. However, microglia do not represent a uniform population, but comprise a diverse group of cells with brain region-specific phenotypes that can exert beneficial or detrimental effects, depending on the local phenotype and context. Understanding how microglia can be neuroprotective in one brain region, while promoting neurotoxicity in another, will improve our understanding of the role of microglia in neurodegeneration in general, and of their role in PD pathology in particular. Since neuroinflammatory responses are in principle modifiable, such approaches could help to identify new targets or adjunctive therapies for the full spectrum of PD-related symptoms.

Risk of dementia in an elderly population of Parkinson's disease patients: a 15-year population-based study

BACKGROUND

The incidence of dementia in Parkinson's disease (PD) is not fully known, and previous studies have provided a wide range of rates owing to variations in diagnostic criteria and methodologies used. We estimated the risk of dementia in newly diagnosed cases of PD in a population-based cohort of subjects aged >65 years.

METHODS

We performed repetitive systematic screening of PD diagnosis, cognitive performances, and clinical dementia during 15 years (at year 0, 3, 5, 8, 10, and 15) in 3726 elderly subjects living at home in southwestern France (PAQUID). Two sets of diagnostic criteria for dementia in PD were considered: Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised criteria and Movement Disorders Society criteria.

RESULTS

Forty-four incident cases of PD occurred in the cohort; of these, 18 (41%) developed dementia during a mean follow-up of 6.8 ± 3.6 years. Incidence rate of dementia associated with PD was 74 per 1000 patient-years. The cumulative risk of dementia was approximately 25% and 50% after 5 and 10 years of follow-up, respectively. The relative risk for developing dementia in incident PD subjects compared with non-PD subjects was 2.47 (1.55-3.95). Equivalent estimations were obtained with Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised criteria or Movement Disorders Society criteria.

CONCLUSION

PD represents a high-risk stage for dementia in the general population.

Clinical heterogeneity in Parkinson's disease revisited: a latent profile analysis

OBJECTIVE

The heterogeneity of Parkinson's disease (PD) is increasingly recognized, and several attempts have been made to subclassify subjects on clinical or cognitive features. We explored the utility of latent profile analysis (LPA) as a means of classifying patients with PD on clinical features and test validity of these subclasses against neuropsychological data.

METHODS

LPA utilizing clinical variables while controlling for age was applied to a cohort of 71 outpatients with PD. The resultant subgroups were validated via comparison to 30 control subjects on neuropsychological tests of executive, memory, and visuospatial functions.

RESULTS

The LPA resulted in a three-class solution identifying a 'younger onset, mild motor impairment group', a 'moderate motor impairment group', and an 'old onset, fast progression group'. The groups were distinguishable on cognitive variables with the 'younger onset mild motor impairment subgroup' displaying deficits pertaining verbal acquisition, visuospatial construction, and set maintenance. The 'moderate motor impairment group' exhibited widespread cognitive impairment, and the 'old onset, fast disease progression group' had extensive cognitive impairment but outperformed the former group on verbal acquisition and visuospatial function.

CONCLUSION

LPA holds promise in PD research as it uncovered three PD subtypes distinguished by motor symptoms and disease progression and validated by cognitive variables.

Cognitive performance of GBA mutation carriers with early-onset PD: the CORE-PD study

OBJECTIVE

To assess the cognitive phenotype of glucocerebrosidase (GBA) mutation carriers with early-onset Parkinson disease (PD).

METHODS

We administered a neuropsychological battery and the University of Pennsylvania Smell Identification Test (UPSIT) to participants in the CORE-PD study who were tested for mutations in PARKIN, LRRK2, and GBA. Participants included 33 GBA mutation carriers and 60 noncarriers of any genetic mutation. Primary analyses were performed on 26 GBA heterozygous mutation carriers without additional mutations and 39 age- and PD duration-matched noncarriers. Five cognitive domains, psychomotor speed, attention, memory, visuospatial function, and executive function, were created from transformed z scores of individual neuropsychological tests. Clinical diagnoses (normal, mild cognitive impairment [MCI], dementia) were assigned blind to genotype based on neuropsychological performance and functional impairment as assessed by the Clinical Dementia Rating (CDR) score. The association between GBA mutation status and neuropsychological performance, CDR, and clinical diagnoses was assessed.

RESULTS

Demographics, UPSIT, and Unified Parkinson's Disease Rating Scale-III performance did not differ between GBA carriers and noncarriers. GBA mutation carriers performed more poorly than noncarriers on the Mini-Mental State Examination (p = 0.035), and on the memory (p = 0.017) and visuospatial (p = 0.028) domains. The most prominent differences were observed in nonverbal memory performance (p < 0.001). Carriers were more likely to receive scores of 0.5 or higher on the CDR (p < 0.001), and a clinical diagnosis of either MCI or dementia (p = 0.004).

CONCLUSION

GBA mutation status may be an independent risk factor for cognitive impairment in patients with PD.

Non-motor symptoms of Parkinson's disease in China: a review of the literature

Parkinson's disease (PD) is generally considered as a neurodegenerative disorder commonly characterized by bradykinesia, resting tremor, rigidity and postural instability. However, increasing evidence demonstrates that serial non-motor symptoms (NMSs), including sensory symptoms, dysautonomia, neurobehavioral disorders and sleep disturbances frequently occur prior to motor signs and invariably emerge with the disease progression. Compared with motor symptoms, the NMSs are frequently under-recognized and poorly managed in clinical practice. A growing number of clinical studies on NMSs of PD have been carried out in China over the past decade. They revealed that there were not only common features, but also some differences on NMSs between Chinese patients and those in the West. Meanwhile, pharmacological and non-pharmacological strategies are available for the treatment of some NMSs associated with PD in China contained in Chinese guidelines for the treatment of PD. Large cohort studies across the country are warranted in the future to explore the epidemiological and biological features of specific NMSs in Chinese PD patients.

Cognitive deficits in a mouse model of pre-manifest Parkinson's disease

Early cognitive deficits are increasingly recognized in patients with Parkinson's disease (PD), and represent an unmet need for the treatment of PD. These early deficits have been difficult to model in mice, and their mechanisms are poorly understood. α-Synuclein is linked to both familial and sporadic forms of PD, and is believed to accumulate in brains of patients with PD before cell loss. Mice expressing human wild-type α-synuclein under the Thy1 promoter (Thy1-aSyn mice) exhibit broad overexpression of α-synuclein throughout the brain and dynamic alterations in dopamine release several months before striatal dopamine loss. We now show that these mice exhibit deficits in cholinergic systems involved in cognition, and cognitive deficits in domains affected in early PD. Together with an increase in extracellular dopamine and a decrease in cortical acetylcholine at 4-6 months of age, Thy1-aSyn mice made fewer spontaneous alternations in the Y-maze and showed deficits in tests of novel object recognition (NOR), object-place recognition, and operant reversal learning, as compared with age-matched wild-type littermates. These data indicate that cognitive impairments that resemble early PD manifestations are reproduced by α-synuclein overexpression in a murine genetic model of PD. With high power to detect drug effects, these anomalies provide a novel platform for testing improved treatments for these pervasive cognitive deficits.

Genetic influences on cognitive decline in Parkinson's disease

The role of genetic factors in cognitive decline associated with Parkinson's disease (PD) is unclear. We examined whether variations in apolipoprotein E (APOE), microtubule-associated protein tau (MAPT), or catechol-O-methytransferase (COMT) genotypes are associated with cognitive decline in PD. We performed a prospective cohort study of 212 patients with a clinical diagnosis of PD. The primary outcome was change in Mattis Dementia Rating Scale version 2 score. Linear mixed-effects models and survival analysis were used to test for associations between genotypes and change in cognitive function over time. The ε4 allele of APOE was associated with more rapid decline (loss of 2.9; 95% confidence interval [CI]: 1.7-4.1) of more points per year; P < 0.001) in total score and an increased risk of a ≥ 10 point drop during the follow-up period (hazard ratio, 2.8; 95% CI: 1.4-5.4; P = 0.003). MAPT haplotype and COMT genotype were associated with measures of memory and attention, respectively, over the entire follow-up period, but not with the overall rate of cognitive decline. These results confirm and extend previously described genetic associations with cognitive decline in PD and imply that individual genes may exert effects on specific cognitive domains or at different disease stages. Carrying at least one APOE ε4 allele is associated with more rapid cognitive decline in PD, supporting the idea of a component of shared etiology between PD dementia and Alzheimer's disease. Clinically, these results suggest that genotyping can provide information about the risk of future cognitive decline for PD patients.

Prefrontal dopaminergic receptor abnormalities and executive functions in Parkinson's disease

The main pattern of cognitive impairments seen in early to moderate stages of Parkinson's disease (PD) includes deficits of executive functions. These nonmotor complications have a significant impact on the quality of life and day-to-day activities of PD patients and are not effectively managed by current therapies, a problem which is almost certainly due to the fact that the disease extends beyond the nigrostriatal system. To investigate the role of extrastriatal dopamine in executive function in PD, PD patients and a control group were studied with positron-emission-tomography using a high-affinity dopamine D2/D3 receptor tracer, [(11) C]FLB-457. All participants were scanned twice while performing an executive task and a control task. Patients were off medication for at least 12 h. The imaging analysis revealed that parkinsonian patients had lower [(11) C]FLB-457 binding than control group independently of task conditions across different brain regions. Cognitive assessment measures were positively correlated with [(11) C]FLB-457 binding in the bilateral dorsolateral prefrontal cortex and anterior cingulate cortex only in control group, but not in PD patients. Within the control group, during the executive task (as compared to control task), there was evidence of reduced [(11) C]FLB-457 binding (indicative of increased dopamine release) in the right orbitofrontal cortex. In contrast, PD patients did not show any reduction in binding during the executive task (as compared with control task). These findings suggest that PD patients present significant abnormalities in extrastriatal dopamine associated with executive processing. These observations provide important insights on the pathophysiology of cognitive dysfunction in PD.

Link between non-motor symptoms and cognitive dysfunctions in de novo, drug-naive PD patients

Little is known about the relationship between cognitive dysfunctions and the non-motor complex in subjects with newly diagnosed untreated Parkinson's disease (PD). The aim of this study was to explore the association between non-motor symptoms (NMS) and cognitive dysfunctions in an incident cohort of de novo, drug-naive, PD patients. Sixty-six non-demented, early, untreated PD patients completed a semi-structured interview on NMS and a battery of neuropsychological tests that assess verbal memory, visuospatial abilities, and attention/executive functions. Scores were age- and education-corrected. Patients who failed at least two tests for each cognitive domain were diagnosed as having mild cognitive impairment (MCI). All but three (95.4%) PD patients complained of at least one NMS. A total of 37.8% was diagnosed with MCI. There was a relationship between sleep-NMS and cognitive dysfunctions. Specifically, both REM behavioral sleep disorders (RBD) and insomnia were associated with lower scores on several cognitive tests. Moreover, RBD was closely related to MCI. NMS and MCI are very common even in the early phase of PD, before patients are treated. Given the correlation between sleep disturbances and cognitive impairment, it is possible that sleep symptoms in PD patients might be considered as an early marker of dementia.