Neuropsychological prediction of dementia in Parkinson's disease

Alzheimer's disease: a comprehensive review of epidemiology, risk factors, symptoms diagnosis, management, caregiving, advanced treatments and associated challenges

Background

Alzheimer's disease (AD) is a chronic, progressive neurodegenerative disorder characterized by cognitive decline, memory loss, and impaired reasoning. It is the leading cause of dementia in older adults, marked by the pathological accumulation of amyloid-beta plaques and neurofibrillary tangles. These pathological changes lead to widespread neuronal damage, significantly impacting daily functioning and quality of life.

Objective

This comprehensive review aims to explore various aspects of Alzheimer's disease, including its epidemiology, risk factors, clinical presentation, diagnostic advancements, management strategies, caregiving challenges, and emerging therapeutic interventions.

Methods

A systematic literature review was conducted across multiple electronic databases, including PubMed, MEDLINE, Cochrane Library, and Scopus, from their inception to May 2024. The search strategy incorporated a combination of keywords and Medical Subject Headings (MeSH) terms such as "Alzheimer's disease," "epidemiology," "risk factors," "symptoms," "diagnosis," "management," "caregiving," "treatment," and "novel therapies." Boolean operators (AND, OR) were used to refine the search, ensuring a comprehensive analysis of the existing literature on Alzheimer's disease.

Results

AD is significantly influenced by genetic predispositions, such as the apolipoprotein E (APOE) ε4 allele, along with modifiable environmental factors like diet, physical activity, and cognitive engagement. Diagnostic approaches have evolved with advances in neuroimaging techniques (MRI, PET), and biomarker analysis, allowing for earlier detection and intervention. The National Institute on Aging and the Alzheimer's Association have updated diagnostic criteria to include biomarker data, enhancing early diagnosis.

Conclusion

The management of AD includes pharmacological treatments, such as cholinesterase inhibitors and NMDA receptor antagonists, which provide symptomatic relief but do not slow disease progression. Emerging therapies, including amyloid-beta and tau-targeting treatments, gene therapy, and immunotherapy, offer potential for disease modification. The critical role of caregivers is underscored, as they face considerable emotional, physical, and financial burdens. Support programs, communication strategies, and educational interventions are essential for improving caregiving outcomes. While significant advancements have been made in understanding and managing AD, ongoing research is necessary to identify new therapeutic targets and enhance diagnostic and treatment strategies. A holistic approach, integrating clinical, genetic, and environmental factors, is essential for addressing the multifaceted challenges of Alzheimer's disease and improving outcomes for both patients and caregivers.

Cognition and Activity of Daily Living Function in people with Parkinson's disease

The ability to perform activities of daily living (ADL) function is a multifaceted construct that reflects functionality in different daily life situations. The loss of ADL function due to cognitive impairment is the core feature for the diagnosis of Parkinson's disease dementia (PDD). In contrast to Alzheimer's disease, ADL impairment in PD can be compromised by various factors, including motor and non-motor aspects. This narrative review summarizes the current state of knowledge on the association of cognition and ADL function in people with PD and introduces the concept of "cognitive ADL" impairment for those problems in everyday life that are associated with cognitive deterioration as their primary cause. Assessment of cognitive ADL impairment is challenging because self-ratings, informant-ratings, and performance-based assessments seldomly differentiate between "cognitive" and "motor" aspects of ADL. ADL function in PD is related to multiple cognitive domains, with attention, executive function, and memory being particularly relevant. Cognitive ADL impairment is characterized by behavioral anomalies such as trial-and-error behavior or task step omissions, and is associated with lower engagement in everyday behaviors, as suggested by physical activity levels and prolonged sedentary behavior. First evidence shows that physical and multi-domain interventions may improve ADL function, in general, but the evidence is confounded by motor aspects. Large multicenter randomized controlled trials with cognitive ADL function as primary outcome are needed to investigate which pharmacological and non-pharmacological interventions can effectively prevent or delay deterioration of cognitive ADL function, and ultimately the progression and conversion to PDD.

Nigral Pathology Contributes to Microstructural Integrity of Striatal and Frontal Tracts in Parkinson's Disease

BACKGROUND

Motor and cognitive impairment in Parkinson's disease (PD) is associated with dopaminergic dysfunction that stems from substantia nigra (SN) degeneration and concomitant α-synuclein accumulation. Diffusion magnetic resonance imaging (MRI) can detect microstructural alterations of the SN and its tracts to (sub)cortical regions, but their pathological sensitivity is still poorly understood.

OBJECTIVE

To unravel the pathological substrate(s) underlying microstructural alterations of SN, and its tracts to the dorsal striatum and dorsolateral prefrontal cortex (DLPFC) in PD.

METHODS

Combining post-mortem in situ MRI and histopathology, T1-weighted and diffusion MRI, and neuropathological samples of nine PD, six PD with dementia (PDD), five dementia with Lewy bodies (DLB), and 10 control donors were collected. From diffusion MRI, mean diffusivity (MD) and fractional anisotropy (FA) were derived from the SN, and tracts between the SN and caudate nucleus, putamen, and DLPFC. Phosphorylated-Ser129-α-synuclein and tyrosine hydroxylase immunohistochemistry was included to quantify nigral Lewy pathology and dopaminergic degeneration, respectively.

RESULTS

Compared to controls, PD and PDD/DLB showed increased MD of the SN and SN-DLPFC tract, as well as increased FA of the SN-caudate nucleus tract. Both PD and PDD/DLB showed nigral Lewy pathology and dopaminergic loss compared to controls. Increased MD of the SN and FA of SN-caudate nucleus tract were associated with SN dopaminergic loss. Whereas increased MD of the SN-DLPFC tract was associated with increased SN Lewy neurite load.

CONCLUSIONS

In PD and PDD/DLB, diffusion MRI captures microstructural alterations of the SN and tracts to the dorsal striatum and DLPFC, which differentially associates with SN dopaminergic degeneration and Lewy neurite pathology. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Neuropsychiatric Symptoms and Caregiver Stress in Parkinson's Disease with Cognitive Impairment, Alzheimer's Disease, and Frontotemporal Dementia

BACKGROUND

A better understanding of factors associated with caregiver burden might facilitate the construction of coping strategies to improve their clinical outcomes and the comprehensive care model for dementia.

OBJECTIVE

To investigate the cognitive and neuropsychiatric domains that contribute to caregiver burden in three types of neurodegenerative disorders: Parkinson's disease (PD), Alzheimer's disease (AD), and frontotemporal disease (FTD).

METHODS

Eight hundred and fourteen patients and their caregivers were invited to participate; among them, 235 had PD with cognitive impairment; 429 had AD, and 150 had FTD. The evaluation protocol included the Neuropsychiatric Inventory (NPI), the Mini-Mental State Examination, the Chinese Version Verbal Learning Test, the modified Trail Making Test B, semantic fluency, and a geriatric depression score. Statistical comparisons of the cognitive tests, NPI total scores, and caregiver burden among the three diagnosed types of dementia, matched for a Clinical Dementia Rating (CDR) of 0.5 or 1, were performed, and multivariate linear regression models were used to evaluate the parameter significance.

RESULTS

Caregivers for patients with PD and FTD showed significant burden increments when the CDR scores changes from 0.5 to 1. For CDR = 0.5, the PD group had significantly lower caregiver burdens than the AD group, but the NPI total scores were significantly higher. Factors related to caregiver burden were the presence of delusion among all diagnosis groups, while the impact of NPI total scores related to caregiver burden was the highest in FTD, followed by AD and PD.

CONCLUSIONS

At the mild to moderate stages, our results suggested different degrees of significance in terms of the cognitive test scores or NPI subdomains for predicting caregiver stress among the three types of dementia.

The epidemiology of cognitive function in Parkinson's disease

Epidemiology is the study of the distribution of disease in human populations, which is important in evaluating burden of illness, identifying modifiable risk factors, and planning for current and projected needs of the health care system. Parkinson's disease (PD) is the second most common serious neurodegenerative illness and is expected to further increase in prevalence. Cognitive changes are increasingly viewed as an integral non-motor feature in PD, emerging even in the prodromal phase of the disease. The prevalence of PD-MCI ranges from 20% to 40% depending on the population studied. The incidence of PD-dementia increases with duration of disease, with estimates growing from 3% to 30% of individuals followed for 5 years or less to over 80% after 20 years. There are several challenges in estimating the frequency of cognitive change, including only recently standardized diagnostic criteria, variation depending on exact neuropsychological evaluations performed, and differences in population sampling. Clinical features associated with cognitive decline include older age, increased disease duration and severity, early gait dysfunction, dysautonomia, hallucinations and other neuropsychiatric features, the presence of REM behavior disorder, and posterior predominant dysfunction on neuropsychological testing. There is increasing evidence that genetic risk factors, in particular GBA and MAPT mutations, contribute to cognitive change. Possible protective factors include higher cognitive reserve and regular exercise. Important sequelae of cognitive decline in PD include higher caregiver burden, decreased functional status, and increased risk of institutionalization and mortality. Many remaining uncertainties regarding the epidemiology of cognitive change in PD require future research, with improved biomarkers and more sensitive and convenient outcome measures.

Short and Long-Term Cognitive Effects of Subthalamic Deep Brain Stimulation in Parkinson's Disease and Identification of Relevant Factors

BACKGROUND

Subthalamic nucleus deep brain stimulation (STN-DBS) successfully controls the motor symptoms of Parkinson's disease (PD) but has associated cognitive side-effects.

OBJECTIVE

Establish the short- and long-term cognitive effects of STN-DBS in PD.

METHODS

Both the short-term and long-term effects of STN-DBS on cognition were examined through evaluation of the controlled studies that compared patients with STN-DBS to unoperated PD patients, thus controlling for illness progression. We also reviewed the literature to identify the factors that influence cognitive outcome of STN-DBS in PD.

RESULTS

The meta-analysis of the short-term cognitive effects of STN-DBS revealed moderate effect sizes for semantic and phonemic verbal fluency and small effect sizes for psychomotor speed and language, indicating greater decline in the STN-DBS operated than the unoperated patients in these cognitive domains. The longer-term STN-DBS results from controlled studies indicated rates of cognitive decline/dementia up to 32%; which are no different from the rates from the natural progression of PD. Greater executive dysfunction and poorer memory pre-operatively, older age, higher pre-operative doses of levodopa, and greater axial involvement are some of the factors associated with worse cognition after STN-DBS in PD.

CONCLUSION

This evidence can be used to inform patients and their families about the short-term and long-term risks of cognitive decline following STN-DBS surgery and aid the team in selection of suitable candidates for surgery.

Mapping Actuarial Criteria for Parkinson’s Disease-Mild Cognitive Impairment onto Data-Driven Cognitive Phenotypes

Prevalence rates for mild cognitive impairment in Parkinson’s disease (PD-MCI) remain variable, obscuring the diagnosis’ predictive utility of greater dementia risk. A primary factor of this variability is inconsistent operationalization of normative cutoffs for cognitive impairment. We aimed to determine which cutoff was optimal for classifying individuals as PD-MCI by comparing classifications against data-driven PD cognitive phenotypes. Participants with idiopathic PD (n = 494; mean age 64.7 ± 9) completed comprehensive neuropsychological testing. Cluster analyses (K-means, Hierarchical) identified cognitive phenotypes using domain-specific composites. PD-MCI criteria were assessed using separate cutoffs (−1, −1.5, −2 SD) on ≥2 tests in a domain. Cutoffs were compared using PD-MCI prevalence rates, MCI subtype frequencies (single/multi-domain, executive function (EF)/non-EF impairment), and validity against the cluster-derived cognitive phenotypes (using chi-square tests/binary logistic regressions). Cluster analyses resulted in similar three-cluster solutions: Cognitively Average (n = 154), Low EF (n = 227), and Prominent EF/Memory Impairment (n = 113). The −1.5 SD cutoff produced the best model of cluster membership (PD-MCI classification accuracy = 87.9%) and resulted in the best alignment between PD-MCI classification and the empirical cognitive profile containing impairments associated with greater dementia risk. Similar to previous Alzheimer’s work, these findings highlight the utility of comparing empirical and actuarial approaches to establish concurrent validity of cognitive impairment in PD.

Detecting the Cognitive Prodrome of Dementia in Parkinson's Disease

BACKGROUND

More than 75% of Parkinson's disease (PD) patients will develop dementia. Previous studies on the cognitive predictors of dementia in PD had some methodological limitations and the cognitive tests identified as good predictors vary greatly.

OBJECTIVE

This prospective cohort study aims to identify the optimal cognitive predictors of dementia in PD using complementary statistical methods.

METHODS

Eighty PD patients without dementia underwent polysomnographic recording, a neurological examination, and a complete neuropsychological assessment at baseline. They were then followed for a mean of 4.3 years. Baseline group comparisons and survival analyses were used to identify optimal cognitive predictors. Moreover, patients who developed dementia were pair-matched at baseline according to age, sex, and education to healthy controls (2 : 1), and receiver operating characteristic curves were calculated for cognitive tests.

RESULTS

At follow-up, 23 patients (29%) developed dementia. PD patients who developed dementia had poorer baseline performance and a higher proportion of clinically impaired performance on several cognitive tests. Impaired baseline performance on the Block Design subtest was the best independent predictor of dementia (HR = 8). Moreover, the Trail Making Test part B (time) and Verbal Fluency (semantic) had the best psychometric properties (area under the curve >0.90) for identifying PD patients at risk of dementia.

CONCLUSION

The present study identified three cognitive tests as the most accurate to detect individuals with PD at high risk of developing dementia.

Cortical Thickness from MRI to Predict Conversion from Mild Cognitive Impairment to Dementia in Parkinson Disease: A Machine Learning-based Model

Background Group comparison results associating cortical thinning and Parkinson disease (PD) dementia (PDD) are limited in their application to clinical settings. Purpose To investigate whether cortical thickness from MRI can help predict conversion from mild cognitive impairment (MCI) to dementia in PD at an individual level using a machine learning-based model. Materials and Methods In this retrospective study, patients with PD and MCI who underwent MRI from September 2008 to November 2016 were included. Features were selected from clinical and cortical thickness variables in 10 000 randomly generated training sets. Features selected 5000 times or more were used to train random forest and support vector machine models. Each model was trained and tested in 10 000 randomly resampled data sets, and a median of 10 000 areas under the receiver operating characteristic curve (AUCs) was calculated for each. Model performances were validated in an external test set. Results Forty-two patients progressed to PDD (converters) (mean age, 71 years ± 6 [standard deviation]; 22 women), and 75 patients did not progress to PDD (nonconverters) (mean age, 68 years ± 6; 40 women). Four PDD converters (mean age, 74 years ± 10; four men) and 20 nonconverters (mean age, 67 years ± 7; 11 women) were included in the external test set. Models trained with cortical thickness variables (AUC range, 0.75-0.83) showed fair to good performances similar to those trained with clinical variables (AUC range, 0.70-0.81). Model performances improved when models were trained with both variables (AUC range, 0.80-0.88). In pair-wise comparisons, models trained with both variables more frequently showed better performance than others in all model types. The models trained with both variables were successfully validated in the external test set (AUC range, 0.69-0.84). Conclusion Cortical thickness from MRI helped predict conversion from mild cognitive impairment to dementia in Parkinson disease at an individual level, with improved performance when integrated with clinical variables. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Port in this issue.

The Feasibility and Positive Effects of Wuqinxi Exercise on the Cognitive and Motor Functions of Patients with Parkinson's Disease: A Pilot Study

Introduction

Parkinson's disease (PD) is a chronic degenerative disease of the central nervous system common in middle-aged and elderly people, which has a serious impact on patients' cognitive and motor functions. Exercise can improve the nonmotor symptoms of PD patients, but the optimal type of exercise for the cognitive function of patients is unclear. Therefore, the purpose of this study is the impact of 12 weeks of Wuqinxi exercise on the cognitive and motor function in PD patients.

Methods

Thirty PD patients participated in the study and were randomly assigned to two groups: Wuqinxi group (n = 15) or stretching group (n = 15). All the participants performed a 12-week exercise program twice a week, 90 min/session. The assessments were conducted before and after exercise intervention, included cognitive function (frontal assessment battery (FAB); Stroop test I and II), motor functions (Unified Parkinson's Disease Rating Scale Part III (UPDRS-III); timed up and go (TUG)).

Results

We found the FAB and Stroop I scores were significantly higher in the Wuqinxi group than in the stretching group. Participants in the Wuqinxi group significantly improved their UPDRS-III (17.73 ± 9.88) and TUG (10.50 ± 1.79) score after 12 weeks of training intervention.

Conclusion

The results show that the use of Wuqinxi for rehabilitation therapy for cognition is feasible, widely accepted, and effective in patients with Parkinson's disease. This study provides preliminary evidence for further large-scale and controlled studies.

Predicting Neurocognitive Change after Bilateral Deep Brain Stimulation of Subthalamic Nucleus for Parkinson's Disease

OBJECTIVE

Deep brain stimulation (DBS) of the bilateral subthalamic nucleus (STN) is a standard surgical treatment option in patients with advanced Parkinson's disease. Adverse effects on cognitive function have been reported, impacting the quality of life of patients and caregivers. We aimed to investigate a quantitative predictive preexisting cognitive factor for predicting postoperative cognitive changes.

METHODS

Thirty-five patients underwent STN-DBS. A battery of neuropsychological tests were used to examine executive function, processing speed, and visuospatial function both preoperatively and 1 year postoperatively. A multiple logistic regression analysis was performed to investigate the relationships between preoperative factors and cognitive outcomes. The predictive value of the preoperative factors for global cognitive decline during long-term follow-up were evaluated.

RESULTS

The patients exhibited significant changes in processing speed and visuospatial function after surgery. Using reliable change index values, lower preoperative scores on the Similarities and Object Assembly subtests of the Wechsler Adult Intelligence Scale III were associated with decreases in visuospatial function at 1 year after DBS. The odds ratios were 10.2 for Similarities and 9.53 for Object Assembly. The proportion of Mini Mental State Examination-maintained patients with low scores on the Similarities subtest was significantly lower than that of patients with high scores at 3 and 5 years. No factors were found to be related to decreases in processing speed.

CONCLUSIONS

Preoperative evaluation of the Similarities and Object Assembly subtests may be useful to identify patients who are at a greater risk of experiencing decreases in visuospatial functioning after STN-DBS. Furthermore, a low score on the Similarities subtest may predict future global cognitive deterioration.

Elevated caudate connectivity in cognitively normal Parkinson's disease patients

Mild cognitive impairment (MCI) is common in Parkinson’s disease patients. However, its underlying mechanism is not well understood, which has hindered new treatment discoveries specific to MCI. The aim of this study was to investigate functional connectivity changes of the caudate nucleus in cognitively impaired Parkinson’s patients. We recruited 18 Parkinson’s disease patients—10 PDNC [normal cognition Parkinson’s disease; Montreal Cognitive Assessment (MoCA) ≥ 26], 8 PDLC (low cognition Parkinson’s disease; MoCA < 26) —and 10 age-matched healthy controls. All subjects were scanned with resting-state functional magnetic resonance imaging (MRI) and perfusion MRI. We analyzed these data for graph theory metrics and Alzheimer’s disease-like pattern score, respectively. A strong positive correlation was found between the functional connectivity of the right caudate nucleus and MoCA scores in Parkinson’s patient groups, but not in healthy control subjects. Interestingly, PDNC’s functional connectivity of the right caudate was significantly higher than both PDLC and healthy controls, while PDLC and healthy controls were not significantly different from each other. We found that Alzheimer’s disease-like metabolic/perfusion pattern score correlated with MoCA scores in healthy controls, but not in Parkinson’s disease. Increased caudate connectivity may be related to a compensatory mechanism found in cognitively normal patients with Parkinson’s disease. Our findings support and complement the dual syndrome hypothesis.

Clinical Characterization of Parkinson's Disease Patients With Cognitive Impairment

Background: Cognitive impairment is one of the most frequent and disabling non-motor symptoms in Parkinson disease (PD) and encompasses a continuum from mild cognitive impairment (PD-MCI) to dementia (PDD). The risk factors associated with them are not completely elucidated. Objective: To characterize the presence and clinical presentation of PD-MCI and PDD in patients with idiopathic PD, examining motor and non-motor features and determining factors associated with cognitive impairment. Methods: Multicenter, cross-sectional study in 298 PD patients who underwent clinical [Hoehn and Yahr (HY) staging and Clinical Impression of Severity Index for Parkinson Disease], neurological [Scales for Outcomes in Parkinson's Disease (SCOPA)-Motor], neuropsychological (Mini Mental State Examination, SCOPA-Cognition, Frontal Assessment Battery and Clinical Dementia Rating Scale), neuropsychiatric [SCOPA-Psychiatric complications, SCOPA-Psychosocial (SCOPA-PS), and Hospital Anxiety and Depression Scale (HADS)], and health-related quality of life [Parkinson Disease Questionnaire for quality of life (PDQ-8)] assessment. Movement Disorders Society criteria were applied to classify patients as normal cognition (NC), PD-MCI, and PDD. The association between variables was explored using multivariate binary and multinomial logistic regression models. Results: Seventy-two patients (24.2%) were classified as NC, 82 (27.5%) as PD-MCI, and 144 (48.3%) as PDD. These last two groups reported more psychosocial problems related with the disease (mean SCOPA-PS, 16.27 and 10.39, respectively), compared with NC (7.28) and lower quality-of-life outcomes (PDQ-8 48.98 and 28.42, respectively) compared to NC (19.05). The logistic regression analysis showed that both cognitive impaired groups had a more severe stage of PD measured by HY [odds ratio (OR) for MCI-PD, 2.45; 95% confidence interval (CI), 1.22-4.90; OR for PDD 2.64; 95% CI, 1.17-5.98]. Specifically, age (OR, 1.30; 95% CI, 1.16-1.47), years of education (OR, 0.91; 95% CI, 0.83-0.99), disease duration (OR, 1.19; 95% CI, 1.07-1.32), HADS-D (OR, 1.20; 95% CI, 1.06-1.35), and hallucinations (OR, 2.98; 95% CI, 1.16-7.69) were related to PDD. Conclusions: Cognitive impairment in PD is associated with more severe disease stage, resulting in a global, neuropsychiatric, psychosocial, and quality-of-life deterioration. This study provides a better understanding of the great impact that cognitive impairment has within the natural history of PD and its relationship with the rest of motor and non-motor symptoms in the disease.

Reduced Gray Matter Volume and Risk of Falls in Parkinson's Disease with Dementia Patients: A Voxel-Based Morphometry Study

Purpose: Risk of falls is a common sequela affecting patients with Parkinson’s disease (PD). Although motor impairment and dementia are correlated with falls, associations of brain structure and cognition deficits with falls remain unclear. Material and Methods: Thirty-five PD patients with dementia (PDD), and 37 age- and sex-matched healthy subjects were recruited for this study. All participants received structural magnetic resonance imaging (MRI) scans, and disease severity and cognitive evaluations. Additionally, patient fall history was recorded. Regional structural differences between PDD with and without fall groups were performed using voxel-based morphometry processing. Stepwise logistic regression analysis was used to predict the fall risk in PDD patients. Results: The results revealed that 48% of PDD patients experienced falls. Significantly lower gray matter volume (GMV) in the left calcarine and right inferior frontal gyrus in PDD patients with fall compared to PDD patients without fall were noted. The PDD patients with fall exhibited worse UPDRS-II scores compared to PDD patients without fall and were negatively correlated with lower GMV in the left calcarine (p/r = 0.004/−0.492). Furthermore, lower GMV in the left calcarine and right inferior frontal gyrus correlated with poor attention and executive functional test scores. Multiple logistic regression analysis showed that the left calcarine was the only variable (p = 0.004, 95% CI = 0.00–0.00) negatively associated with the fall event. Conclusions: PDD patients exhibiting impaired motor function, lower GMV in the left calcarine and right inferior frontal gyrus, and notable cognitive deficits may have increased risk of falls.

Factor analysis-derived cognitive profile predicting early dementia conversion in PD

OBJECTIVES

To investigate which baseline neuropsychological profile predicts the risk of developing dementia in early-stage Parkinson disease (PD).

METHODS

We retrospectively reviewed detailed medical records of 350 drug-naive patients with early-stage PD (follow-up >3 years) who underwent a detailed neuropsychological test at initial assessment. Factor analysis was conducted to determine cognitive profiles that yielded 4 cognitive function factors: factor 1, visual memory/visuospatial; factor 2, verbal memory; factor 3, frontal/executive; and factor 4, attention/working memory/language. Subsequently, we assessed the effect of these cognitive function factors on the risk for dementia conversion. We also constructed a nomogram to calculate the risk for developing dementia over a 5-year follow-up period based on these cognitive profiles.

RESULTS

Cox regression analysis demonstrated that a higher composite score of factor 1 (hazard ratio [HR] 0.558, 95% confidence interval [CI] 0.427-0.730), factor 2 (HR 0.768, 95% CI 0.596-0.991), and factor 3 (HR 0.425, 95% CI 0.305-0.593) was associated with a lower risk for dementia conversion, while factor 3 had the most predictive power. The nomogram had a fair ability (Heagerty integrated area under the curve 0.763) to estimate the risk for dementia conversion within 5 years. The composite scores of factor 3 contributed more to the occurrence of dementia in PD than those of the other cognitive function factors.

CONCLUSIONS

These findings suggest that these factor analysis-derived cognitive profiles can be used to predict dementia conversion in early-stage PD. In addition, frontal/executive dysfunction contributes most to the occurrence of dementia in PD.

Progression of Cognitive Decline in Parkinson's Disease

Background:

Cognitive dysfunction is one of the most prevalent non-motor symptoms in Parkinson’s disease (PD), often experienced as more debilitating for patients and caregivers than motor problems. Therefore, a deeper understanding of the course of cognitive decline and the identification of valid progression markers for Parkinson’s disease dementia (PDD) is essential.

Objective:

This systematic review summarizes the current state of knowledge on cognitive decline over time by reporting effect sizes of cognitive changes in neuropsychological tests.

METHODS:

1368 studies were identified by a PubMed database search and 25 studies by additionally scanning previous literature. After screening all records, including 69 full-text article reviews, 12 longitudinal studies on the progression of cognitive decline in PD met our criteria (e.g., sample size ≥50 patients).

Results:

Only a few studies monitored cognitive decline over a longer period (>4 years). Most studies focused on the evaluation of change in global cognitive state by use of the Mini-Mental State Examination, whereas the use of neuropsychological tests was highly heterogenic among studies. Only one study evaluated patients’ cognitive performance in all specified domains (executive function, attention & working memory, memory, language, and visual-spatial function) allowing for diagnosis of cognitive impairment according to consensus guidelines. Medium to strong effect sizes could only be observed in studies with follow-up intervals of four years or longer.

Conclusions:

The results emphasize the need for the assessment of larger PD cohorts over longer periods of follow-up with a comprehensive neuropsychological battery.

Cognitive Load Affects Speech Motor Performance Differently in Older and Younger Adults

Purpose The aim of this study was to determine the impact of cognitive load imposed by a speech production task on the speech motor performance of healthy older and younger adults. Response inhibition, selective attention, and working memory were the primary cognitive processes of interest. Method Twelve healthy older and 12 healthy younger adults produced multiple repetitions of 4 sentences containing an embedded Stroop task in 2 cognitive load conditions: congruent and incongruent. The incongruent condition, which required participants to suppress orthographic information to say the font colors in which color words were written, represented an increase in cognitive load relative to the congruent condition in which word text and font color matched. Kinematic measures of articulatory coordination variability and movement duration as well as a behavioral measure of sentence production accuracy were compared between groups and conditions and across 3 sentence segments (pre-, during-, and post-Stroop). Results Increased cognitive load in the incongruent condition was associated with increased articulatory coordination variability and movement duration, compared to the congruent Stroop condition, for both age groups. Overall, the effect of increased cognitive load was greater for older adults than younger adults and was greatest in the portion of the sentence in which cognitive load was manipulated (during-Stroop), followed by the pre-Stroop segment. Sentence production accuracy was reduced for older adults in the incongruent condition. Conclusions Increased cognitive load involving response inhibition, selective attention, and working memory processes within a speech production task disrupted both the stability and timing with which speech was produced by both age groups. Older adults' speech motor performance may have been more affected due to age-related changes in cognitive and motoric functions that result in altered motor cognition.

Mind the gaps: What we don't know about cognitive impairment in essential tremor

INTRODUCTION

Although the hallmark feature of essential tremor (ET) is tremor, there is growing appreciation that cognitive impairment also occurs, including increased prevalence of mild cognitive impairment (MCI) and increased prevalence and incidence of dementia. With emerging knowledge of ET-cognitive impairment, come fundamental questions regarding its course, bases, predictors and clinical outcomes. Studies in the general population and in Parkinson's disease (PD), a related movement disorder, offer a starting point from which to begin filling these clinically important knowledge gaps.

METHODS

A PubMed search (June 2018) identified articles for this review.

RESULTS

Much of our knowledge of cognitive impairment in ET is of the static condition (e.g., prevalence of cognitive impairment in ET), with nearly no information on its bases, predictors and dynamics (i.e., course, and clinical outcomes). In PD, where such data have been published, rates of cognitive decline and conversion to MCI/dementia are higher than in the general population. Predictors of cognitive change in PD and the general population have also been identified, yet they only partially overlap one another.

CONCLUSION

The predictors and dynamics of cognitive impairment have been investigated fairly extensively in the general population, to a somewhat lesser extent in PD, and are emerging only now in ET. We suggest that longitudinal studies specific to ET are needed, and we outline variables to be considered in these investigations. Increased knowledge of ET-cognitive impairment will facilitate meaningful counseling of patients and their families.

Cognitive Estimation in Non-demented Parkinson's Disease

Objective

The Cognitive Estimation Test (CET) is widely used in clinical and research settings to assess the ability to produce reasonable estimates to items that individuals would not know that the exact answer (e.g., "How fast do race horses run?"). We examined the performance of non-demented Parkinson's disease (PD) patients on the CET, because previous studies reported heterogeneous results about possible cognitive estimation impairments in PD. We also examined whether PD patients improve their performance if given the chance to reconsider their initial CET responses.

Methods

Thirty non-demented idiopathic PD patients and 30 healthy controls matched in age, gender and years of education performed the two parallel forms of Italian CET. The estimation scores for initial and final responses as well as the number of times individuals changed their answers were examined. Additional neuropsychological tests, evaluating intellectual, frontal executive, speed of processing, naming and arithmetical abilities, were also administered.

Results

The PD group were not significantly poorer than healthy controls at estimating the answers to items on either CET versions. Moreover, PD patients did not significantly differ in their initial and final responses or number of response changes. Performance on the CET was significantly related to performance on a global measure of executive function, processing speed and arithmetic. However, PD patients were impaired compared to controls on the component involving mainly, but not exclusively, length-related estimations.

Conclusions

Non-demented PD patients have mild impairments in cognitive estimation ability, which may depend on the estimations they are required to provide.

Effects of physical exercise programs on cognitive function in Parkinson's disease patients: A systematic review of randomized controlled trials of the last 10 years

Background

Given the relative importance of cognitive impairment, there was considerable interest in identifying the cognitive profile of PD patients, in order to ensure specific and appropriate therapeutic interventions.

Purpose

To determine the effects of physical exercise programs on cognitive function in PD patients, compared with the control group.

Data sources

Medline, Cochrane, Scopus, PEDro and Web of Science (last searched in September 2016).

Study selection

Randomized clinical trials examining the effects of physical exercise programs and cognitive function in PD patients. Nine studies fulfilled the selection criteria and were included in this review.

Data extraction

Characteristics of the publication, characteristics of the participants, test used for cognitive screening, cognitive domain assessed, tools used to assess cognitive function, characteristics of the experimental intervention, characteristics of the control group, mean results and standard deviation of function cognitive. The PEDro score was used to evaluate methodological quality.

Data synthesis

Most eligible studies showed good methodological quality based on the PEDro scale. Studies have shown that adapted tango for PD patients, cognitive training combined with motor training, and treadmill training promote the preservation or improvement of cognitive function in PD patients.

Limitations

The diversity of cognitive tests used to assess cognitive function and the high heterogeneity identified between the physical exercise programs.

Conclusions

Physical exercise programs promote positive and significant effects on global cognitive function, processing speed, sustained attention and mental flexibility in PD patients, at a mild to moderate stage for patients with a 6-year clinical diagnosis of PD. However, treadmill training performed 3 times a week for about 60 minutes and for a period of 24 weeks produced larger improvements in cognition.

Cognitive flexibility in neurological disorders: Cognitive components and event-related potentials

Performance deficits on the Wisconsin Card Sorting Test (WCST) in patients with prefrontal cortex (PFC) lesions are traditionally interpreted as evidence for a role of the PFC in cognitive flexibility. However, WCST deficits do not occur exclusively after PFC lesions, but also in various neurological and psychiatric disorders. We propose a multi-component approach that can accommodate this pattern of omnipresent WCST deficits: the WCST is not a pure test of cognitive flexibility, but relies on the effective functioning of multiple dissociable cognitive components. Our review of recent efforts to decompose WCST performance deficits supports this view by revealing that WCST deficits in different neurological disorders can be attributed to alterations in different components. Frontoparietal changes underlying impaired set shifting seem to give rise to WCST deficits in patients with amyotrophic lateral sclerosis, whereas the WCST deficits associated with primary dystonia and Parkinson's disease are rather related to frontostriatal changes underlying deficient rule inference. Clinical implications of these findings and of a multi-component view of WCST performance are discussed.

Diagnostic Accuracy and Confidence in the Clinical Detection of Cognitive Impairment in Early-Stage Parkinson Disease

BACKGROUND/AIMS

Mild cognitive impairment (MCI) is present in up to 34% of patients with early-stage Parkinson disease (PD); however, it is difficult to detect subtle impairment without objective cognitive testing.

METHODS

Data were obtained from the Parkinson Progression Marker Initiative. All 341 participants were administered the Montreal Cognitive Assessment (MoCA) and a brief neuropsychological battery. Participants were classified as PD-MCI if MoCA was <26 or if they scored ≥1 standard deviation below the normative mean in 2 or more domains, based upon established criteria. The sensitivity/specificity for the clinical detection of PD-MCI was determined.

RESULTS

Overall accuracy for clinical detection of PD-MCI was 67.4%. Although clinical determination was highly specific (96.3%; 95% confidence interval [CI]: 0.92-0.98), sensitivity was poor (32.0%; 95% CI: 0.25-0.40).

CONCLUSION

Identifying MCI in early-stage PD based on clinical interview alone appears to be insufficient. The inclusion of objective cognitive tests allowing for normative sample comparisons is needed to increase the detection of cognitive impairment in this population.

The Prague Stroop Test: Normative standards in older Czech adults and discriminative validity for mild cognitive impairment in Parkinson's disease

OBJECTIVE

The aim of this study was to provide normative data for older and very old Czech adults on the Prague Stroop Test (PST) and to test its discriminative validity in individuals with Parkinson's disease mild cognitive impairment (PD-MCI).

METHOD

The construction of the PST was modeled after the Victoria Stroop Test. We examined 539 participants aged 60-96 that met strict inclusion criteria. After, we compared the PST scores for a group of 45 PD-MCI patients with a healthy adult sample (HAS) of 45 age- and education-matched individuals.

RESULTS

I. In the non-clinical sample, robust age- and education-related influences were observed on all PST scores. No gender effect was noted. II. For clinical cases, interference condition (PST-C) was able to discriminate between PD-MCI and HAS (all scores ps < .01). Area under the curve (AUC) was 77% when a screening cut-off of ≤ 27 s was used, showing sensitivity of 82% and specificity of 53%. A more conservative diagnostic cut-off of ≤ 33 s showed sensitivity of 60% and specificity of 80%.

DISCUSSION

The present study provides PST normative data for basic, interference, and error scores stratified by age (60-96 years). PST appears to be a helpful tool for the diagnostics of PD-MCI especially in research settings at Level II (Litvan et al., 2012) and for PD-MCI attention/working memory and executive function subtyping.

How Much Does WAIS-IV Perceptual Reasoning Decline Across the 20 to 90-Year Lifespan When Processing Speed is Controlled?

The most prominent pattern of cognitive change over the lifespan centers on the difference between patterns of maintained abilities on tests of crystallized knowledge and patterns of steady decline on tests of problem solving and processing speed. Whereas the maintained-vulnerable dichotomy is well established in the literature, questions remain about cognitive decline in problem solving when processing speed is controlled. This relationship has been examined in cross-sectional studies that typically used non-clinical tests with non-representative samples of adults. This study extended these findings to the most popular clinical test, the Wechsler Adult Intelligence Scale -4th ed. (WAIS-IV), using its carefully stratified sample as the source of data (ages 20-90 for Indexes, ages 16-90 for Perceptual Reasoning subtests). Multivariate Analysis of Covariance (MANCOVA) revealed that 70-80% of the variance in declining reasoning ability was shared with the speed factor. This was true (a) on the index and subtest level and (b) regardless of the type of problem-solving task employed. Such robust findings have important clinical and research implications for neuropsychologists, who most frequently use the Wechsler scales as part of their assessment battery.

Different PD-MCI criteria and risk of dementia in Parkinson's disease: 4-year longitudinal study

The Movement Disorder Society Task Force (MDS-TF) has proposed diagnostic criteria for mild cognitive impairment in Parkinson's disease (PD-MCI). We hypothesized that the risk of dementia (PDD) varies across the different cutoff schemes allowed. A longitudinal study followed 121 non-demented PD patients for up to 4.5 years. In Part One, unique groups of patients were identified as PD-MCI at baseline using the MDS-TF requirement of two impaired cognitive test scores, with both scores classified as impaired at either (i) 2 s.d., (ii) 1.5 s.d. or (iii) 1 s.d. below normative data; relative risk (RR) of PDD was assessed at each criterion. In Part Two, the whole sample was reassessed and (i) RR of PDD determined when two impairments at 1.5 s.d. existed within a single cognitive domain, followed by (ii) RR of PDD in the unique group whose two impairments at 1.5 s.d. did not exist within a single domain (i.e., only across two domains). Twenty-one percent of patients converted to PDD. Part One showed that the 1.5 s.d. criterion at baseline is optimal to maximize progression to PDD over 4 years. Part Two, however, showed that the 1.5 s.d. cutoff produced a high RR of PDD only when two impairments were identified within a single cognitive domain (7.2, 95% confidence interval (CI)=3.4-16.6, P<0.0001; 51% converted). The RR when the 1.5 s.d. impairments occurred only across two different domains, was nonsignificant (1.7, CI=0.5-7.4, P=0.13; 11% converted) and similar to using a 1 s.d. criterion (1.9, CI=0.3-4.3, P=0.13; 8% converted). If the intent of a PD-MCI diagnosis is to detect increased risk of PDD in the next 4 years, optimal criteria should identify at least two impairments at 1.5 s.d. within a single cognitive domain.

Mild cognitive impairment in Parkinson's disease and its progression onto dementia: a 16-year outcome evaluation of the Denbighshire cohort

OBJECTIVE

Mild cognitive impairment in Parkinson's disease (PD-MCI) has been suggested to be a predictor for the development of PD dementia (PDD). This study explored the incidence and possible neuropsychological domain differences between PD patients with PD-MCI and without cognitive impairment (normal cognitive function with PD), on the basis of the Movement Disorders Task Force Guidelines for PD-MCI.

METHODS

At baseline (T1), 4 years (T2) and 6 years (T3), 166 patients with PD were administered global neuropsychological assessments. At 16 years, case note and neuropsychological assessment review was employed to calculate the number of patients who had progressed to PDD.

RESULTS

At baseline, 68 patients were classified as normal cognitive function with PD, 18 with PD-MCI and 80 with PDD. At T2, 12 of the PD-MCI cohort at T1 had progressed to PDD, and there were 15 incident cases of PD-MCI. At T3, nine PD-MCI cases at T2 had progressed to PDD. There were 10 incident cases of PD-MCI at T3. The incidence of progression from PD-MCI to PDD was 98.0 per 1000 person-years, with an annual conversion rate to PDD of 11%. Neuropsychological predictors for conversion from PD-MCI to PDD were semantic language, praxis (figure drawing/copying) and visuospatial deficits. At 16 years, 91% of the PD-MCI cohort had progressed to PDD.

CONCLUSIONS

Mild cognitive impairment in Parkinson's disease is an important predictor for the progression to PDD. This investigation also confirmed that if PD patients live long enough, they will develop cognitive impairment or dementia. Early detection of cognitive impairment in these individuals is possible with existing standardised global cognitive assessments, which include semantic language assessment.

DEVELOPMENT OF CLINICAL DEMENTIA RATING SCALE CUTOFF SCORES FOR PATIENTS WITH PARKINSON'S DISEASE

BACKGROUND

The purpose of this study was to explore validity of the Clinical Dementia Rating Scale in measuring cognitive impairment among individuals with Parkinson's disease. The scale was created for use in patients with Alzheimer's disease and, to date, there have been no published studies examining if this tool is appropriate for patients with Parkinson's disease.

METHODS

The data were obtained from the National Alzheimer's Coordinating Center database and included 490 subjects diagnosed with Parkinson's disease, further categorized as having Parkinson's disease dementia (n= 151), mild cognitive impairment (n= 186), or normal cognition (n = 153) by a treating physician. Sensitivity, specificity, positive predictive value and negative predictive values were calculated for the Clinical Dementia Rating Scale Global Score as well as the Sum of Boxes Score using existing cutoff scores. Finally, new cutoff scores were calculated using sensitivity and specificity values derived using Receiver Operating Characteristic curves.

RESULTS

Sensitivity and specificity of the published Global Score cutoff scores for patients with dementia were .34 and .10, respectively. The newly calculated cutoff scores for patients with dementia yielded a sensitivity of .79 and a specificity of .96. The area under the curve was 0.92 (95% CI = 0.90-0.95).

CONCLUSION

The CDR is a useful tool in identifying dementia in patients with Parkinson's disease when the cutoff scores are adjusted.

Clinical phenotype of drug-naïve Parkinson's disease based on nonmotor symptoms

BACKGROUND

Nonmotor symptoms in Parkinson's disease (PD) are heterogeneous and can result in a variety of symptoms at various disease stages. The objective of the present study was to identify clinically meaningful nonmotor symptoms and to assess the relationship between changes in nonmotor symptoms and cognition and motor symptoms.

METHODS

A total of 159 patients who had drug-naïve PD participated in this study. Nonmotor symptoms (Nonmotor Symptoms Scale), PD status (Unified Parkinson's Disease Rating Scale), depression (Geriatric Depression Scale or Montgomery-Asberg Depression Scale) and health-related quality of life (39-item Parkinson's Disease Questionnaire) were assessed. An exploratory factor analysis was performed to establish a nonmotor symptom factor, which was analyzed to evaluate whether the results were associated with the clinical severity measures.

RESULTS

Exploratory factor analysis revealed one factor comprised of sleep/fatigue, attention/memory and mood/cognition. The modified Hoehn and Yahr Stage, Unified Parkinson's Disease Rating Scale Part III, Montgomery-Asberg Depression Scale and the 39-item Parkinson's Disease Questionnaire Summary Index were independently associated with the sleep/fatigue, attention/memory and mood/cognition domains. The presence of these domains was associated with advanced Parkinson's disease or depressed mood.

CONCLUSIONS

This study shows that motor impairment and depressed mood in PD are related to sleep/fatigue, attention/memory and mood/cognition. Sleep/fatigue, attention/memory and mood/cognition also had a major impact on health-related quality of life. It is appropriate to identify patients with severe motor symptoms and depressed mood in order to signify the need to consider more detailed care and further assessment.

Exercise improves cognition in Parkinson's disease: The PRET-PD randomized, clinical trial

BACKGROUND

This article reports on the findings of the effect of two structured exercise interventions on secondary cognitive outcomes that were gathered as part of the Progressive Resistance Exercise Training in Parkinson's disease (PD) randomized, controlled trial.

METHODS

This study was a prospective, parallel-group, single-center trial. Fifty-one nondemented patients with mild-to-moderate PD were randomly assigned either to modified Fitness Counts (mFC) or to Progressive Resistance Exercise Training (PRET) and were followed for 24 months. Cognitive outcomes were the Digit Span, Stroop, and Brief Test of Attention (BTA).

RESULTS

Eighteen patients in mFC and 20 patients in PRET completed the trial. At 12 and at 24 months, no differences between groups were observed. At 12 months, relative to baseline, mFC improved on the Digit Span (estimated change: 0.3; interquartile range: 0, 0.7; P = 0.04) and Stroop (0.3; 0, 0.6; P = 0.04), and PRET improved only on the Digit Span (0.7; 0.3, 1; P < 0.01). At 24 months, relative to baseline, mFC improved on the Digit Span (0.7; 0.3, 1.7; P < 0.01) and Stroop (0.3; 0.1, 0.5; P = 0.03), whereas PRET improved on the Digit Span (0.5; 0.2, 0.8; P < 0.01), Stroop (0.2; -0.1, 0.6; P = 0.048), and BTA (0.3; 0, 0.8; P = 0.048). No neurological or cognitive adverse events were observed.

CONCLUSIONS

This study provides class IV level of evidence that 24 months of PRET or mFC may improve attention and working memory in nondemented patients with mild-to-moderate Parkinson's disease.

Neuroimaging correlates of cognitive impairment and dementia in Parkinson's disease

There has been a gradual shift in the definition of Parkinson's disease, from a movement disorder to a neurodegenerative condition affecting multiple cognitive domains. Mild cognitive impairment (PD-MCI) is a frequent comorbidity in PD that is associated with progression to dementia (PDD) and debilitating consequences for patients and caregivers. At present, the pathophysiology underpinning cognitive impairment in PD is not established, although emerging evidence has suggested that multi-modal imaging biomarkers could be useful in the early diagnosis of PD-MCI and PDD, thereby identifying at-risk patients to enable treatment at the earliest stage possible. Structural MRI studies have revealed prominent grey matter atrophy and disruptions of white matter tracts in PDD, although findings in non-demented PD have been more variable. There is a need for further longitudinal studies to clarify the spatial and temporal progression of morphological changes in PD, as well as to assess their underlying involvement in the evolution of cognitive deficits. In this review, we discuss the aetiology and neuropsychological profiles of PD-MCI and PDD, summarize the putative imaging substrates in light of evidence from multi-modal neuroimaging studies, highlight limitations in the present literature, and suggest recommendations for future research.

Rational pharmacological approaches for cognitive dysfunction and depression in Parkinson's disease

Parkinson’s disease (PD) is not a single entity but rather a heterogeneous neurodegenerative disorder. The present study aims to conduct a critical systematic review of the literature to describe the main pharmacological strategies to treat cognitive dysfunction and major depressive disorder in PD patients. We performed a search of articles cited in PubMed from 2004 to 2014 using the following MeSH terms (Medical subject headings) “Parkinson disease”; “Delirium,” “Dementia,” “Amnestic,” “Cognitive disorders,” and “Parkinson disease”; “depression,” “major depressive disorder,” “drug therapy.” We found a total of 71 studies related to pharmacological treatment in cognitive dysfunction and 279 studies for pharmacological treatment in major depressive disorder. After fulfillment of all the inclusion and exclusion criteria, 13 articles remained for cognitive dysfunction and 11 for major depressive disorder, which are presented and discussed in this study. Further research into non-motor symptoms of PD may provide insights into mechanisms of neurodegeneration, and provide better quality of life by using rational drugs.

Cognitive deficits in Parkinson's disease: a cognitive neuroscience perspective

Progress in characterization of the nature, neural basis, and treatment of cognitive deficits in Parkinson's disease is reviewed from the perspective of cognitive neuroscience. An initial emphasis on fronto-striatal executive deficits is surveyed along with the discoveries of disruption as well as remediation of certain impairments by dopaminergic mediation and their association with theories of reinforcement learning. Subsequent focus on large cohorts has revealed considerable heterogeneity in the cognitive impairments as well as a suggestion of at least two distinct syndromes, with the dopamine-dependent fronto-striatal deficits being somewhat independent of other signs commonly associated with Parkinson's disease dementia. The utility is proposed of a new, integrated cognitive neuroscience approach based on combining genetic and neuroimaging methodologies with neuropsychological and, ultimately, psychopharmacological approaches.

Dementia and cognitive impairment in patients with Parkinson's disease from India: a 7-year prospective study

Depression and cognitive impairment are frequent manifestations in Parkinson's disease (PD). Although a few longitudinal studies have reported on depression and dementia in PD, there is a yet a lack of such studies in India. This 7-year longitudinal study is a hospital-based prospective case (n = 250)-control (n = 280) study. In all, 36.8% had PD with no cognitive impairment (PD-Normal), 27.2% of the patients with PD were affected by dementia (PDD), and 36% of the remaining patients with PD had mild cognitive impairment (PD-MCI) at baseline. After 7 years of evaluation, 32 new patients, 12 patients from the PD-MCI group and 9 patients from the PD-Normal group, were diagnosed with dementia. The 7-year prevalence rate for dementia was estimated to be 49.28%. In the Indian population, an early onset of dementia is noted among patients with PD, with the age of onset being less than 55 years. Patients with early-onset PDD showed depression symptoms that differed significantly from the controls of the same age-group. There was a major difference in verbal fluency, word list recall, constructional praxis and recall, word list recognition, abridged Boston Naming Test, word list memory with repetition, and Mini-Mental State Examination between PD-MCI and PDD groups. Hallucinations before baseline (odds ratio [OR] = 4.427, 95% confidence interval [CI] = 2.122-9.373), akinetic/tremor dominancy (OR = 0.380, 95%CI = 0.149-0.953), and asymmetrical disease onset (OR = 0.3285, 95%CI = 0.1576-0.685) can be considered as risk factors for patients with dementia. Patients with early-onset PD might be more prone to complex depression and dementia. As the disease progresses, akinetic-dominant PD, early hallucinations, and asymmetrical disease onset are the potential risk factors for the development of dementia in patients with PD.

Neural substrates of cognitive subtypes in Parkinson's disease: a 3-year longitudinal study

BACKGROUND

The neuropsychological features and neuropathological progression patterns associated with rapidly evolving cognitive decline or dementia in Parkinson's disease (PD) remain to be elucidated.

METHODS

Fifty-three PD patients without dementia were recruited to participate in a 3-year longitudinal cohort study. The patients were grouped according to the Clinical Dementia Rating (CDR). Group-wise comparisons were made with regard to demographic characteristics, motor symptoms, neuropsychological performances and 18F-fluorodeoxyglucose positron emission tomography.

RESULTS

Patients who had memory-plus cognitive impairment (patients whose CDR was 0 at baseline and 0.5 in memory and other domains at follow-up, and those whose baseline CDR was 0.5 in memory and other domains) exhibited higher age at onset, visuoperceptual impairment, non-tremor-dominant motor disturbance, rapid symptomatic progression and posterior neocortical hypometabolism. In patients who were cognitively unimpaired and those who had memory-dominant cognitive impairment (patients whose CDR was 0 at baseline and 0.5 only in memory domain at follow-up, and those whose baseline CDR was 0.5 only in memory domain), the posterior neocortex was relatively unaffected until a later stage of the disease.

CONCLUSIONS

These results suggest that visuoperceptual impairment and the early involvement of the posterior neocortex may be risk factors for rapid symptomatic progression and dementia in PD.

Executive dysfunction in Parkinson's disease: a review

Executive dysfunction can be present from the early stages of Parkinson's disease (PD). It is characterized by deficits in internal control of attention, set shifting, planning, inhibitory control, dual task performance, and on a range of decision-making and social cognition tasks. Treatment with dopaminergic medication has variable effects on executive deficits, improving some, leaving some unchanged, and worsening others. In this review, we start by defining the specific nature of executive dysfunction in PD and describe suitable neuropsychological tests. We then discuss how executive deficits relate to pathology in specific territories of the basal ganglia, consider the impact of dopaminergic treatment on executive function (EF) in this context, and review the changes in EFs with disease progression. In later sections, we summarize correlates of executive dysfunction in PD with motor performance (e.g., postural instability, freezing of gait) and a variety of psychiatric (e.g., depression, apathy) and other clinical symptoms, and finally discuss the implications of these for the patients' daily life.

Predictors of dementia in Parkinson's disease; findings from a 5-year prospective study using the SCOPA-COG

OBJECTIVE

Aim of this study was to identify risk factors for the development of dementia in patients with Parkinson's disease (PD).

METHODS

A broad range of motor and non-motor features was assessed at baseline and the following five years in 406 PD patients. Cross-sectional analyses of baseline data and longitudinal analyses of follow-up data were performed to identify risk factors for dementia.

RESULTS

Thirty-two percent of patients (n = 129) had dementia at baseline, while 26% of patients (n = 68) without dementia at baseline developed dementia during follow-up. Univariate survival analysis showed that higher age, fewer years of education, longer disease duration, higher age-at-onset, higher levodopa dose, higher Hoehn & Yahr stage, presence of dyskinesias, excessive daytime sleepiness (EDS), presence of hallucinations, and more severe autonomic and depressive symptoms were associated with an increased risk of dementia. Higher baseline Postural-Instability-and-Gait-Difficulty scores were also associated with an increased risk of dementia, whereas no effect of tremor severity was found. These findings largely corresponded with the variables that were associated with the presence of dementia at baseline. In a stepwise regression model, higher age at baseline, fewer years of education, higher daily levodopa dose and excessive daytime sleepiness (EDS) emerged as independent risk factors of future dementia.

CONCLUSIONS

In this large prospective cohort study, we identified a combination of potentially interacting risk factors for dementia in PD that are associated with higher age and more advanced disease.

The spectrum of cognitive impairment in Lewy body diseases

Cognitive impairment represents an important and often defining component of the clinical syndromes of Lewy body disorders: Parkinson's disease and dementia with Lewy bodies. The spectrum of cognitive deficits in these Lewy body diseases encompasses a broad range of clinical features, severity of impairment, and timing of presentation. It is now recognized that cognitive dysfunction occurs not only in more advanced Parkinson's disease but also in early, untreated patients and even in those patients with pre-motor syndromes, such as rapid eye movement behavior disorder and hyposmia. In recent years, the concept of mild cognitive impairment as a transitional or pre-dementia state in Parkinson's disease has emerged. This has led to much research regarding the diagnosis, prognosis, and underlying neurobiology of mild cognitive impairment in Parkinson's disease, but has also raised questions regarding the usefulness of this concept and its application in clinical and research settings. In addition, the conundrum of whether Parkinson's disease dementia and dementia with Lewy bodies represent the same or different entities remains unresolved. Although these disorders overlap in many aspects of their presentations and pathophysiology, they differ in other elements, such as timing of cognitive, behavioral, and motor symptoms; medication responses; and neuropathological contributions. This article examines the spectrum and evolution of cognitive impairment in Lewy body disorders and debates these controversial issues in the field using point-counterpoint approaches.

Exploratory analysis of neuropsychological and neuroanatomical correlates of progressive mild cognitive impairment in Parkinson's disease

BACKGROUND

Parkinson's disease with mild cognitive impairment (PD-MCI) is a heterogeneous entity in terms of cognitive profiles and conversion to dementia. However, the risk factors for ongoing cognitive decline in patients with PD-MCI are not clearly defined.

METHODS

51 patients with PD-MCI were prospectively followed-up for a minimum of 2 years. Subjects were classified as MCI converters (n=15) or MCI non-converters (n=36) based on whether they were subsequently diagnosed with PD dementia. We explored cognitive profiles and neuroanatomical characteristics of PD-MCI converters using voxel based morphometry (VBM) of grey matter (GM) density and region of interest based volumetric analysis of the substantia innominata (SI).

RESULTS

PD-MCI converters showed more severe cognitive deficits in frontal executive functions, immediate verbal memory and visual recognition memory compared with PD-MCI non-converters. VBM analysis revealed that PD-MCI converters had significantly lower GM density in the left prefrontal areas, left insular cortex and bilateral caudate nucleus compared with that in PD-MCI non-converters. The mean normalised SI volume was significantly smaller in both PD-MCI converters (1.19±0.35, p<0.001) and PD-MCI non-converters (1.52±0.27, p<0.001) compared with that in controls (1.87±0.19). PD-MCI converters had a significantly smaller normalised SI volume than PD-MCI non-converters (p<0.001).

CONCLUSIONS

Our data show that atrophy in the frontostriatal areas and cholinergic structures, as well as frontal lobe associated cognitive performance, may act as predictors of dementia in PD-MCI patients, suggesting distinctive patterns of cognitive profiles and a neuroanatomical basis for progressive PD-MCI.

Executive dysfunction in Parkinson's disease and timing deficits

Patients with Parkinson’s disease (PD) have deficits in perceptual timing, or the perception and estimation of time. PD patients can also have cognitive symptoms, including deficits in executive functions such as working memory, planning, and visuospatial attention. Here, we discuss how PD-related cognitive symptoms contribute to timing deficits. Timing is influenced by signaling of the neurotransmitter dopamine in the striatum. Timing also involves the frontal cortex, which is dysfunctional in PD. Frontal cortex impairments in PD may influence memory subsystems as well as decision processes during timing tasks. These data suggest that timing may be a type of executive function. As such, timing can be used to study the neural circuitry of cognitive symptoms of PD as they can be studied in animal models. Performance of timing tasks also maybe a useful clinical biomarker of frontal as well as striatal dysfunction in PD.

Parkinson's disease disrupts both automatic and controlled processing of action verbs

The problem of how word meaning is processed in the brain has been a topic of intense investigation in cognitive neuroscience. While considerable correlational evidence exists for the involvement of sensory-motor systems in conceptual processing, it is still unclear whether they play a causal role. We investigated this issue by comparing the performance of patients with Parkinson's disease (PD) with that of age-matched controls when processing action and abstract verbs. To examine the effects of task demands, we used tasks in which semantic demands were either implicit (lexical decision and priming) or explicit (semantic similarity judgment). In both tasks, PD patients' performance was selectively impaired for action verbs (relative to controls), indicating that the motor system plays a more central role in the processing of action verbs than in the processing of abstract verbs. These results argue for a causal role of sensory-motor systems in semantic processing.

Volumetric correlates of cognitive functioning in nondemented patients with Parkinson's disease

A challenge in Parkinson's disease (PD) is to identify biomarkers of early cognitive change because functioning in some domains may be more prognostic of dementia. Few studies have investigated whether structural magnetic resonance imaging (MRI) correlates in a regionally specific manner with functioning in different cognitive domains. The aim of this study was to identify neuroanatomical correlates of executive functioning, memory, and visual cognition in PD without dementia. 3T MRI was conducted in 51 PD patients and 39 control participants. Brain volumes were measured in structures comprising the frontostriatal cognitive-control system, the medial temporal memory system, the ventral object-based system, and the dorsal spatial-based system. Measures of executive functioning (Stroop Test; Letter Fluency), memory (California Verbal Learning Test), visuospatial cognition (Judgment of Line Orientation), and visuoconstruction (Pentagon Copy) were correlated with volumes comprising each system. Poorer executive functioning largely correlated with decreased frontostriatal volumes. Poorer memory correlated with decreased volumes in all medial temporal regions, but also with frontostriatal volumes. Poorer visuospatial cognition correlated with decreased volumes in the object-based system, whereas poorer visuoconstruction correlated with decreased frontal and object-based system volumes. These relationships were nonsignificant in the control group. This is the first study to demonstrate that subtle changes in multiple cognitive domains in PD without dementia correlate with regional volumes in specific systems implicated in the development of cognitive impairment. The findings suggest that structural MRI holds promise as a marker of early changes in different brain systems, some of which may predict future cognitive deterioration.