Validity of the Dementia Rating Scale in assessing cognitive function in Parkinson's disease

Cognitive function in different motor subtypes of Parkinson's disease: A systematic review protocol

Background and Aims

As the fastest-growing neurological disorder globally, a better understanding of Parkinson's disease (PD) is needed to improve patient outcomes and reduce the increasing economic and healthcare burden associated with the disease. Whilst classified as a movement disorder, this disease is highly heterogeneous, encompassing a broad range of both motor and non-motor symptoms (NMS). Cognitive impairment, presenting as either mild cognitive impairment or PD-dementia, is one of the most prevalent and disabling NMS. To better understand heterogeneity in PD, researchers have sought to identify subtypes of individuals who share similar symptom profiles. To date, this research has predominantly focused on motor subtyping, with many studies comparing these motor subtypes on non-motor outcomes, such as cognitive impairment. However, despite evidence of a motor-cognitive relationship in healthy aging, findings regarding the presence of a motor-cognitive relationship in PD are inconsistent. In our proposed systematic review, we will investigate motor subtyping studies that have evaluated the relationship between motor and cognitive function in PD. We aim to examine what is currently known about the relationship between motor and cognitive impairment in PD and evaluate the state of the field with respect to the subtyping methods and quality of cognitive assessment tools used.

Methods

Systematic literature searches will be conducted in PubMed, PsycINFO, CINAHL, Scopus, and Web of Science.

Results

Results will be synthesized using meta-analysis and, where meta-analysis is not feasible, narrative synthesis.

Conclusion

Despite the preponderance of motor subtyping research in PD, our study will be the first to systematically review evidence regarding the association between motor subtypes and cognitive impairment. Understanding the nature of the motor-cognitive relationship in PD may lead to important insights regarding shared underlying disease pathology, which would have significant implications for early diagnosis, prognosis, and treatment of cognitive impairment in PD.

DRD3 Predicts Cognitive Impairment and Anxiety in Parkinson's Disease: Susceptibility and Protective Effects

Background

A possible genetic contribution of dopamine D3 receptor (DRD3) to cognitive impairment in Parkinson's disease (PD) has yet to be investigated.

Objective

To explore the effects of rs6280 (Ser9Gly) genotype on PD patients' cognitive performance and to clarify possible interactions with psychopathology.

Methods

Two hundred and fifty-three consecutive PD patients underwent neurological and neuropsychological evaluations, which included: Unified Parkinson's Disease Rating Scale (UPDRS), Hoehn & Yahr scale (H&Y), Dementia Rating Scale-2 (DRS-2), and Hospital Anxiety and Depression Scale (HADS). rs6280 polymorphism was genotyped for all PD patients and for 270 ethnically matched healthy volunteers (HC). Non-parametric group comparisons and logistic regressions were used for data analyses.

Results

rs6280 genotype did not differ between PD and HC groups. PD patients with rs6280 CC genotype had more impaired cognitive performance (i.e., <1st percentile of demographically adjusted norms) on DRS-2 subscales Initiation/Perseveration and Construction than those with TT genotype. These associations remained statistically significant when other covariates (e.g., demographic features, disease duration, severity of motor symptoms in OFF and ON states, anti-parkinsonian medication, and psychopathology symptoms) were taken into consideration. PD patients with rs6280 TC had less anxiety (i.e., HADS Anxiety≥11) than those with TT (p = 0.012). This association was also independent of other covariates.

Conclusions

Study findings suggest that rs6280 CC genotype predisposes to executive dysfunction and visuoconstructional deficits, whereas the heterozygous genotype protects from anxiety in PD. These effects do not appear to be dependent of one another. rs6280 is not a genotypic susceptibility factor for PD.

Identifying key multi-modal predictors of incipient dementia in Parkinson's disease: a machine learning analysis and Tree SHAP interpretation

Background

Persons with Parkinson's disease (PD) differentially progress to cognitive impairment and dementia. With a 3-year longitudinal sample of initially non-demented PD patients measured on multiple dementia risk factors, we demonstrate that machine learning classifier algorithms can be combined with explainable artificial intelligence methods to identify and interpret leading predictors that discriminate those who later converted to dementia from those who did not.

Method

Participants were 48 well-characterized PD patients (M_{baseline age} = 71.6; SD = 4.8; 44% female). We tested 38 multi-modal predictors from 10 domains (e.g., motor, cognitive) in a computationally competitive context to identify those that best discriminated two unobserved baseline groups, PD No Dementia (PDND), and PD Incipient Dementia (PDID). We used Random Forest (RF) classifier models for the discrimination goal and Tree SHapley Additive exPlanation (Tree SHAP) values for deep interpretation.

Results

An excellent RF model discriminated baseline PDID from PDND (AUC = 0.84; normalized Matthews Correlation Coefficient = 0.76). Tree SHAP showed that ten leading predictors of PDID accounted for 62.5% of the model, as well as their relative importance, direction, and magnitude (risk threshold). These predictors represented the motor (e.g., poorer gait), cognitive (e.g., slower Trail A), molecular (up-regulated metabolite panel), demographic (age), imaging (ventricular volume), and lifestyle (activities of daily living) domains.

Conclusion

Our data-driven protocol integrated RF classifier models and Tree SHAP applications to selectively identify and interpret early dementia risk factors in a well-characterized sample of initially non-demented persons with PD. Results indicate that leading dementia predictors derive from multiple complementary risk domains.

Dementia Risk Prediction in a Longitudinal Geriatric Parkinson's Disease Cohort: Evaluation and Application of the Montreal Parkinson Risk of Dementia Scale

Background

Parkinson's disease (PD) increases risk for dementia and cascading adverse outcomes. The eight-item Montreal Parkinson Risk of Dementia Scale (MoPaRDS) is a rapid, in-office dementia screening tool. We examine predictive validity and other characteristics of the MoPaRDS in a geriatric PD cohort by testing a series of alternative versions and modelling risk score change trajectories.

Methods

Participants were 48 initially non-demented PD patients (Mage = 71.6 years, range = 65-84) from a three-year, three-wave prospective Canadian cohort study. A dementia diagnosis at Wave 3 was used to stratify two baseline groups: PD with Incipient Dementia (PDID) and PD with No Dementia (PDND). We aimed to predict dementia three years prior to diagnosis using baseline data for eight indicators that harmonized with the original report, plus education.

Results

Three MoPaRDS items (age, orthostatic hypotension, mild cognitive impairment [MCI]) discriminated the groups both independently and as a composite three-item scale (area under the curve [AUC] = 0.88). The eight-item MoPaRDS reliably discriminated PDID from PDND (AUC = 0.81). Education did not improve predictive validity (AUC = 0.77). Performance of the eight-item MoPaRDS varied across sex (AUCfemales = 0.91; AUCmales = 0.74), whereas the three-item configuration did not (AUCfemales = 0.88; AUCmales = 0.91). Risk scores of both configurations increased over time.

Conclusions

We report new data on the application of the MoPaRDS as a dementia prediction tool for a geriatric PD cohort. Results support the viability of the full MoPaRDS, and indicate that an empirically determined brief version is a promising complement.

What does the Dementia Rating Scale-2 measure? The relationship of neuropsychological measures to DRS-2 total and subscale scores in non-demented individuals with Parkinson's disease

OBJECTIVE

The Dementia Rating Scale-2 (DRS-2) is recommended for assessing global cognition in Parkinson's disease (PD) by the Movement Disorder Society. However, empirical evidence is limited regarding the degree to which the DRS-2 corresponds to traditional neurocognitive domains (i.e., construct validity) in PD. Thus, this study aims to determine the construct validity of the DRS-2 in a non-demented sample of PD patients.

METHOD

Patients with PD (n = 359; mean age = 64.50 ± 8.53, education = 14.97 ± 2.73, disease duration = 8.48 ± 4.87, UPDRS Part III motor scale scores = 25.23 ± 10.17) completed the DRS-2 as part of a comprehensive neuropsychological assessment consisting of attention/working memory, executive function, language, delayed recall, and visuoperceptual-spatial skills.Bootstrapped bias-corrected Spearman rho's correlations andhierarchical linear regressions were performed to examine construct validity of DRS-2 total and subscale scores.

RESULTS

Speeded measures of set-shifting, rapid word generation to letter and semantic cues, and simple visuoperceptual skills largely accounted for variance in DRS-2 total scores. Most DRS-2 subscale scores showed weak relationships with theoretically related neuropsychological measures.

CONCLUSIONS

DRS-2 total scores reflect impairment across a range of cognitive domains (i.e., executive, language, and visuoperception), while DRS-2 subscale scores have limited construct validity. Together, the DRS-2 does not appear to have utility beyond screening for global cognition in PD.

Prospective predictors of care partner burden and depression in Parkinson's disease

OBJECTIVES

Care partners who provide informal care to individuals with Parkinson's disease (PD) report higher levels of burden and depression; however, longitudinal research on these symptoms is scarce. The current study assessed changes in care partner burden and depression, and patient and care partner predictors of these symptoms over time. Such knowledge may provide important information for assessment and treatment of depression and burden in care partners of individuals with PD.

RESEARCH DESIGN AND METHODS

Participants were 88 PD patients without dementia and their self-identified care partner (n = 88). Care partners completed the Geriatric Depression Scale and Zarit Burden Interview. PD participants completed mood questionnaires and a motor exam at baseline and 2 year follow-up. Relationships among care partner burden and depression over time with patient and care partner predictors (i.e., demographic, mood, and disease characteristics) were assessed using correlations and regression analyses.

RESULTS

Care partner burden and depression significantly increased over an approximate 2 year period. Greater baseline disease severity predicted worsening of care partner burden (p = 0.028), while baseline patient depression predicted worsening of care partner depression (p = 0.002).

CONCLUSIONS

Results highlight differential impacts of specific PD symptoms on worsening care partner burden compared to depression; increased PD disease severity predicts increased burden, while patient mood predicts worsening of depression over time. Targeting PD disease severity and mood symptoms may prevent the progression of care partner burden and depression.

Changes in Self- and Informant-Reported Frontal Behaviors in Parkinson's Disease: A Longitudinal Study

OBJECTIVE

Frontal behaviors (i.e., executive dysfunction, disinhibition, apathy) are common in Parkinson's disease (PD). However, it is unclear if patient and informant reports of patient frontal behaviors are in agreement over time.

METHOD

Sixty-two PD patients without dementia and their informants (87% spouses/partners) completed the self- and informant-versions of the Frontal Systems Behavior Scale at baseline and 2-year follow-up. Dyad ratings were compared and predictors of behavior ratings were examined.

RESULTS

Patient and informant reports at baseline and follow-up were in agreement, with significant increases in overall frontal behaviors, executive dysfunction, and apathy. Higher levels of baseline patient depression and caregiver burden predicted decrements in patient-reported executive function; worse patient cognition at baseline predicted worsening apathy as rated by informants.

CONCLUSIONS

PD patients and their informants are concordant in their ratings of worsening frontal behaviors over time. Targeting patient depression, cognition, and caregiver burden may improve decrements in frontal behaviors (executive dysfunction and apathy) in PD.

Which Test Is the Best to Assess Visuo-Cognitive Impairment in Patients with Parkinson's Disease with Mild Cognitive Impairment and Dementia? A Systematic Review and Meta-Analysis

BACKGROUND

Visuo-cognitive impairment is common in patients with Parkinson's disease with mild cognitive impairment (PD-MCI) and constitutes a prognostic factor for the conversion to Parkinson's disease dementia (PDD). However, systematic analyses on which neuropsychological tests are most suitable to assess visuo-cognition in PD-MCI and PDD and to differentiate these cognitive stages are lacking.

OBJECTIVE

To review neuropsychological tests used to assess visuo-cognition including visuo-perceptual and visuo-spatial processing, visuo-constructive copying and drawing on command abilities; and to identify the visuo-cognitive subdomain as well as tests most suitable to discriminate between PD-MCI and PDD.

METHODS

MEDLINE, PsycINFO, Web of Science Core Collection, and CENTRAL were systematically searched for relevant studies assessing visuo-cognitive outcomes in patients with PD-MCI and PDD. Risk of bias was assessed using a customized form based on well-established tools. Random-effect meta-analyses were conducted.

RESULTS

33 studies were included in the systematic review. Data of 19 studies were entered in meta-analyses. Considerable heterogeneity regarding applied tests, test versions, and scoring systems exists. Data indicate that visuo-constructive command tasks are the subdomain best suited to discriminate between PD-MCI and PDD. Furthermore, they indicate that the Rey-Osterrieth-Complex-Figure Test (ROCF), Corsi Block-Tapping Test, Judgment of Line Orientation (JLO), and Clock Drawing Test (CDT) are tests able to differentiate between the two stages.

CONCLUSION

We provide suggestions for suitable visuo-cognitive tests (Corsi Block-Tapping Test, or JLO, ROCF, CDT) to improve diagnostic accuracy. Methodological challenges (e.g., heterogeneity of definitions, tests) are discussed and suggestions for future research are provided.

REGISTRATION

https://www.crd.york.ac.uk/prospero/, ID: CRD42018088244.

Central Pain in Parkinson's Disease: Behavioral and Cognitive Characteristics

Introduction

Pain is a major nonmotor symptom of Parkinson's disease (PD), and central parkinsonian pain is the core feature of the putative Park pain subtype of PD. This study aimed to explore the cognitive and behavioral profile of PD patients with central parkinsonian pain. Material and Methods. A structured interview was used to identify and characterize pain in a cohort of 260 consecutive PD patients. The Ford classification of pain was applied. The Dementia Rating Scale-2 (DRS-2) and the Impulse Control Disorders in Parkinson's Disease Short Form (QUIP-S) were administered, and patients' smoking habits were recorded. The Unified Parkinson's Disease Rating Scale (UPDRS) was used to assess motor and nonmotor symptoms in off and on conditions.

Results

One hundred and eighty-eight patients (68%) reported pain; and in 41 (22%) of them, the pain was classified as central parkinsonian pain. PD patients with central parkinsonian pain had better cognitive performance in DRS-2 Initiation/Perseveration and Conceptualization subscales but reported more other compulsive behaviors (e.g., hobbyism, punding, and walkabout) and had more current smoking habits than those without pain or with non-central parkinsonian pain. Multiple logistic regression analyses revealed that the DRS-2 Conceptualization subscale, other compulsive behaviors, and smoking habits remained statistically associated with central parkinsonian pain even when other significant covariates were considered. Only patients with pain, regardless of type, had a gambling disorder. Discussion. The study results provide further evidence that pain revealed that patients with central parkinsonian pain are more likely to present compulsive or addictive behaviors, despite having more preserved cognitive performance. Patients with central parkinsonian pain appear to have a distinct phenotype of PD.

Spatial-Temporal Parameters of Gait Associated With Alzheimer Disease: A Longitudinal Analysis

Alzheimer's disease (AD) is one of the biggest social and medical concerns in the aging world. A dual task of walking and talking is a particularly practical means to assess AD considering the cognitive and behavioral changes that characterize the disease. The purpose of the study was to assess the effect of the dual task of walking and talking on people with early stage AD under differing cognitive load levels of talking. Participants (9 women and 5 men, mean age (years) = 78.03, standard deviation [SD] = 12.06) with mild or moderate AD (mean Dementia Rating Scale 2 score = 88.14, SD = 7.07) completed 12 monthly walking sessions under no, low, or high cognitive load. They also completed the low and high cognitive load tasks while seated. Linear mixed-effects modeling revealed that values in the Functional Ambulation Profile, stride length, and velocity decreased as tasks became more complex and double support time increased at the same rate. The walking and seated conditions comparison indicated that participants' performance on both low and high cognitive tasks was poor when they were walking rather than seated. The results show that people with early stage AD exhibited gait impairments that increased over time and when completing tasks with greater cognitive load.

The impact of distinct cognitive dual-tasks on gait in Parkinson's disease and the associations with the clinical features of Parkinson's disease

AIMS

To investigate the impact of distinct cognitive dual-task abilities in patients with Parkinson's disease (PD) and compare the impact of these dual-tasks in association with the severity of PD and its clinical features.

MATERIALS AND METHODS

Modified Hoehn and Yahr Scale, UPDRS, and Standardized Mini-Mental State Examination (SMMSE) were evaluated in all PD patients. The subtype of PD and the presence of freezing of gait (FOG) were also evaluated. The Timed Up and Go (TUG) test was applied under single- and dual-task conditions including the digit span-forwards, digit span-backwards, delayed recall memory, counting down the days, counting backwards from 20, and animal fluency tests.

RESULTS

Most of the cognitive dual-tasks resulted in deterioration in gait performance in our PD subjects. Remarkably, the completion time of TUG duration under single- and dual-task of counting down days was higher in the FOG (+) PD subjects (p = 0.008, p = 0.050, respectively). Besides, the TUG duration under the dual-task of counting down days was found to be positively correlated with the UPDRS-motor scores and FOG scores.

CONCLUSION

We think that the concurrent execution of the dual-task of counting down days, which requires complex attentional skills, may disturb gait via a mechanism of overloading of the attentional reserves proceeding gait which is already defective in PD subjects. The neural correlate of this domain and its significance in performing dual-tasks in PD should be investigated in future large-scale studies. The results of these studies may provide substantial perspectives regarding the pathophysiology of gait disturbance in PD.

Cognitive and motor correlates of grey and white matter pathology in Parkinson's disease

INTRODUCTION

Previous studies have found associations between grey matter atrophy and white matter hyperintensities (WMH) of vascular origin with cognitive and motor deficits in Parkinson's disease (PD). Here we investigate these relationships in a sample of PD patients and age-matched healthy controls.

METHODS

Data included 50 PD patients and 45 age-matched controls with T1-weighted and FLAIR scans at baseline, 18-months, and 36-months follow-up. Deformation-based morphometry was used to measure grey matter atrophy. SNIPE (Scoring by Nonlocal Image Patch Estimator) was used to measure Alzheimer's disease-like textural patterns in the hippocampi. WMHs were segmented using T1-weighted and FLAIR images. The relationship between MRI features and clinical scores was assessed using mixed-effects models. The motor subscore of the Unified Parkinson's Disease Rating Scale (UPDRSIII), number of steps in a walking trial, and Dementia Rating Scale (DRS) were used respectively as measures of motor function, gait, and cognition.

RESULTS

Substantia nigra atrophy was significantly associated with motor deficits, with a greater impact in PDs (p < 0.05). Hippocampal SNIPE scores were associated with cognitve decline in both PD and controls (p < 0.01). WMH burden was significantly associated with cognitive decline and increased motor deficits in the PD group, and gait deficits in both PD and controls (p < 0.03).

CONCLUSION

While substantia nigra atrophy and WMH burden were significantly associated with additional motor deficits, WMH burden and hippocampal atrophy were associated with cognitive deficits in PD patients. These results suggest an additive contribution of both grey and white matter damage to the motor and cognitive deficits in PD.

Deleterious Impact of Expressive Suppression on Test Performance Persists at One-Year Follow-Up in Community-Dwelling Older Adults

OBJECTIVES

Expressive suppression (ES) is an emotion-regulation strategy that is associated with poorer performance on subsequently administered tests of executive functioning (EF). It is not known, however, how far into the future ES interferes with EF. This study examined whether (a) ES negatively affects performance on EF tests repeated 1 year after the initial administration (presumably through interference with learning, leading to a reduced practice effect), and (b) whether such an effect, if seen, is unique to EF or whether it also affects lower-order cognitive processes needed for EF test performance.

METHODS

Sixty-six non-demented community-dwelling older adults were randomly assigned to either an ES group or control group. Executive and non-executive tests were administered before and immediately following the exposure to an emotionally evocative video, and then again at 1-year follow-up. Groups were compared at 1-year follow-up on tests of EF and lower-order processes, to examine whether the previously demonstrated impact of ES on EF is evident only immediately following the experimental manipulation (Franchow &amp; Suchy, 2017), or also at 1-year follow-up.

RESULTS

The results showed that participants who engaged in ES continued to exhibit poorer performance on EF tests 1 year later. This effect was not present for performance on tests of lower-order processes.

CONCLUSIONS

These results suggest that the use of ES before an EF task can interfere with the ability to benefit from exposure to that task, thereby negatively affecting future performance. (JINS, 2019, 25, 29-38).

Detecting Mild Cognitive Deficits in Parkinson's Disease: Comparison of Neuropsychological Tests

BACKGROUND

Numerous neuropsychological tests and test versions are used in Parkinson's disease research, but their relative capacity to detect mild cognitive deficits and their comparability across studies are unknown. The objective of this study was to identify neuropsychological tests that consistently detect cognitive decline in PD across studies.

METHODS

Data from 30 normed neuropsychological tests across 20 international studies in up to 2908 nondemented PD patients were analyzed. A subset of 17 tests was administered to up to 1247 healthy controls. A 2-step meta-analytic approach using standardized scores compared performance in PD with normative data.

RESULTS

Pooled estimates of the differences between PD and site-specific healthy controls identified significant cognitive deficits in PD patients on 14 test scores across 5 commonly assessed cognitive domains (attention or working memory, executive, language, memory, and visuospatial abilities), but healthy control performance was statistically above average on 7 of these tests. Analyses based on published norms only, as opposed to direct assessment of healthy controls, showed high between-study variability that could not be accounted for and led to inconclusive results.

CONCLUSIONS

Normed neuropsychological tests across multiple cognitive domains consistently detect cognitive deficits in PD when compared with site-specific healthy control performance, but relative PD performance was significantly affected by the inclusion and type of healthy controls versus the use of published norms only. Additional research is needed to identify a cognitive battery that can be administered in multisite international studies and that is sensitive to cognitive decline, responsive to therapeutic interventions, and superior to individual cognitive tests. © 2018 International Parkinson and Movement Disorder Society.

Exaggerated reaction to novelty as a predictor of incipient cognitive decline among community-dwelling older adults

OBJECTIVE

The ability to detect covert markers of incipient cognitive decline among older adults before cognitive decline becomes overtly evident on traditional cognitive tests represents an important topic of research. Exaggerated reactions to novelty, reflected in novelty-induced increases in action planning latencies ("novelty effect"; NE) and low openness to experience (openness), have been previously associated with incipient cognitive decline among older adults who appeared cognitively normal at baseline. The purposes of the present study were to extend prior research on the utility of these markers by examining whether (a) NE and openness each predict cognitive change uniquely, and (b) whether these indices predict cognitive change above and beyond measures of memory, executive functions, processing speed/efficiency, premorbid IQ, and depressive symptoms.

METHOD

Sixty-one cognitively normal community-dwelling older adults were administered a battery of tests assessing the relevant constructs at baseline and one-year follow up. Changes in cognitive status were assessed using the Demetia Rating Scale, 2nd Edition, NE was assessed using the Push-Turn-Taptap task (an electronic motor sequence learning task), and openness using the NEO Personality Inventory-Revised. The Test of Premorbid Functioning, and subtests from Repeatable Battery for the Assessment of Neuropsychological Status, Delis-Kaplan Executive Function System, and Wechsler Adult Intelligence Scale, 4th Edition, were used for additional assessment of baseline cognition. Depressive symptoms were assessed using the Geriatric Depression Scale.

RESULTS

Results confirmed our hypothesis that both NE and openness contribute to prediction of cognitive change beyond baseline cognition and depressive symptoms, but none of the covariates (i.e., depression, executive functions, processing efficiency, or memory) themselves contributed to the model. NE and openness each contributed unique variance and were independent of each other.

CONCLUSIONS

Openness and NE have the potential to provide evidence-based methods for estimating risk of future cognitive change in persons with currently normal standardized test scores.

Spanish version of the Mattis Dementia Rating Scale-2 for early detection of Alzheimer's disease and mild cognitive impairment

OBJECTIVE

We aimed to analyse the clinical utility of the Mattis Dementia Rating Scale (MDRS-2) for early detection of Alzheimer's disease (AD) and amnestic mild cognitive impairment (MCI) in a sample of Spanish older adults.

METHODS

A total of 125 participants (age = 75.12 ± 6.83, years of education =7.08 ± 3.57) were classified in three diagnostic groups: 45 patients with mild AD, 37 with amnestic MCI-single and multiple domain and 43 cognitively healthy controls (HCs). Reliability, criterion validity and diagnostic accuracy of the MDRS-2 (total and subscales) were analysed. The MDRS-2 scores, adjusted by socio-demographic characteristics, were calculated through hierarchical multiple regression analysis.

RESULTS

The global scale had adequate reliability (α = 0.736) and good criterion validity (r = 0.760, p < .001) with the Mini-Mental State Examination. The optimal cut-off point between AD patients and HCs was 124 (sensitivity [Se] = 97% and specificity [Sp] = 95%), whereas 131 (Se = 89%, Sp = 81%) was the optimal cut-off point between MCI and HCs. An optimal cut-off point of 123 had good Se (0.97), but poor Sp (0.56) to differentiate AD and MCI groups. The Memory and Initiation/Perseveration subscales had the highest discriminative capacity between the groups.

CONCLUSIONS

The MDRS-2 is a reliable and valid instrument for the assessment of cognitive impairment in Spanish older adults. In particular, optimal capacity emerged for the detection of early AD and MCI. Copyright © 2017 John Wiley & Sons, Ltd.

Parametric model measurement: reframing traditional measurement ideas in neuropsychological practice and research

OBJECTIVE

Neuropsychology is an applied measurement field with its psychometric work primarily built upon classical test theory (CTT). We describe a series of psychometric models to supplement the use of CTT in neuropsychological research and test development.

METHOD

We introduce increasingly complex psychometric models as measurement algebras, which include model parameters that represent abilities and item properties. Within this framework of parametric model measurement (PMM), neuropsychological assessment involves the estimation of model parameters with ability parameter values assuming the role of test 'scores'. Moreover, the traditional notion of measurement error is replaced by the notion of parameter estimation error, and the definition of reliability becomes linked to notions of item and test information. The more complex PMM approaches incorporate into the assessment of neuropsychological performance formal parametric models of behavior validated in the experimental psychology literature, along with item parameters. These PMM approaches endorse the use of experimental manipulations of model parameters to assess a test's construct representation. Strengths and weaknesses of these models are evaluated by their implications for measurement error conditional upon ability level, sensitivity to sample characteristics, computational challenges to parameter estimation, and construct validity.

CONCLUSION

A family of parametric psychometric models can be used to assess latent processes of interest to neuropsychologists. By modeling latent abilities at the item level, psychometric studies in neuropsychology can investigate construct validity and measurement precision within a single framework and contribute to a unification of statistical methods within the framework of generalized latent variable modeling.

Expressive Suppression Depletes Executive Functioning in Older Adulthood

OBJECTIVES

Accurate detection of executive dysfunction in neuropsychological assessments is complicated by the fact that executive functioning (EF) is vulnerable to temporary disruption (i.e., lapses), with more frequent lapses in older adulthood. Effortful regulation of affect (i.e., expressive suppression) is a well-known source of executive lapses in younger adults, but the generalizability of this depleting effect to older adults is unknown. The purpose of this study was to (1) determine whether EF is subject to depletion via expressive suppression and (2) to examine whether this effect is unique to EF, or whether it also applies to lower-order component processes in older adults.

METHODS

Ninety-seven non-demented, community-dwelling older adults were randomly assigned to either an expressive suppression group or control group. We compared performance of the groups on a battery of tests measuring EF and component processes both before and after exposure to emotionally evocative stimuli.

RESULTS

Consistent with the hypothesized depletion effect, suppressing participants showed an attenuated practice effect on post-manipulation EF relative to controls, while performance on lower-order component processes was unaffected by suppression.

CONCLUSIONS

These results suggest that depletion contributes to executive lapses in older adulthood. (JINS, 2017, 23, 341-351).

Default mode network differences between rigidity- and tremor-predominant Parkinson's disease

BACKGROUND

Parkinson's disease (PD) traditionally is characterized by tremor, rigidity, and bradykinesia, although cognitive impairment also is a common symptom. The clinical presentation of PD is heterogeneous and associated with different risk factors for developing cognitive impairment. PD patients with primary akinetic/rigidity (PDAR) are more likely to develop cognitive deficits compared to those with tremor-predominant symptoms (PDT). Because cognitive impairment in PD appears to be related to changes in the default mode network (DMN), this study tested the hypothesis that DMN integrity is different between PDAR and PDT subtypes.

METHOD

Resting state fMRI (rs-fMRI) and whole brain volumetric data were obtained from 17 PDAR, 15 PDT and 24 healthy controls (HCs) using a 3T scanner. PD patients were matched closely to HCs for demographic and cognitive variables, and showed no symptoms of dementia. Voxel-based morphometry (VBM) was used to examine brain gray matter (GM) volume changes between groups. Independent component analysis (ICA) interrogated differences in the DMN among PDAR, PDT, and HC.

RESULTS

There was decreased activity in the left inferior parietal cortex (IPC) and the left posterior cingulate cortex (PCC) within the DMN between PDAR and both HC and PDT subjects, even after controlling for multiple comparisons, but not between PDT and HC. GM volume differences between groups were detected at a lower threshold (p < 0.001, uncorrected). Resting state activity in IPC and PCC were correlated with some measures of cognitive performance in PD but not in HC.

CONCLUSION

This is the first study to demonstrate DMN differences between cognitively comparable PDAR and PDT subtypes. The DMN differences between PD and HC appear to be driven by the PDAR subtype. Further studies are warranted to understand the underlying neural mechanisms and their relevance to clinical and cognitive outcomes in PDAR and PDT subtypes.

Global cognitive scores do not predict outcome after subthalamic nucleus deep brain stimulation

BACKGROUND

Presence of dementia is a contraindication for DBS treatment of Parkinson's disease. Recent evidence suggests that borderline cognitive function, as measured with a common screening measure, the Mattis Dementia Rating Scale, has a negative impact on quality of life (QoL) after DBS of the STN.

METHODS

We attempted to replicate and extend this finding in a larger group of patients with a wider range of preoperative global cognitive performance.

RESULTS

Our data indicate that performance on the screening measure is not associated with QoL or medical outcomes, even with scores well below the cutoff for identifying dementia.

CONCLUSIONS

This cognitive screening measure lacks sufficient sensitivity to warrant its use in predicting which patients will show QoL benefit from DBS.

Screening Mild and Major Neurocognitive Disorders in Parkinson's Disease

Introduction. Among the nonmotor features of Parkinson's disease (PD), cognitive impairment is one of the most troublesome problems. New diagnostic criteria for mild and major neurocognitive disorder (NCD) in PD were established by Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-5). The aim of our study was to establish the diagnostic accuracy of widely used screening tests for NCD in PD. Methods. Within the scope of our study we evaluated the sensitivity and specificity of different neuropsychological tests (Addenbrooke's Cognitive Examination (ACE), Mattis Dementia Rating Scale (MDRS), Mini Mental State Examination (MMSE), and Montreal Cognitive Assessment (MoCA)) in 370 PD patients without depression. Results. MoCA and ACE feature the finest diagnostic accuracy for detecting mild cognitive disorder in PD (DSM-5) at the cut-off scores of 23.5 and 83.5 points, respectively. The diagnostic accuracy of these tests was 0.859 (95% CI: 0.818–0.894, MoCA) and 0.820 (95% CI: 0.774–0.859, ACE). In the detection of major NCD (DSM-5), MoCA and MDRS tests exhibited the best diagnostic accuracy at the cut-off scores of 20.5 and 132.5 points, respectively. The diagnostic accuracy of these tests was 0.863 (95% CI: 0.823–0.897, MoCA) and 0.830 (95% CI: 0.785–0.869, MDRS). Conclusion. Our study demonstrated that the MoCA may be the most suitable test for detecting mild and major NCD in PD.

Axial Signs and Magnetic Resonance Imaging Correlates in Parkinson's Disease

Background:

Age-related brain changes may contribute to axial features in Parkinson's disease (PD).

Objectives:

To determine if ventricular volume and white matter high signal changes (WMC) are related to motor signs in PD and controls independent of age.

Methods:

Patients were rated with the Unified Parkinson's Disease Rating Scale (subscore A: tremor, rigidity, bradykinesia, and facial expression; subscore B: speech and axial impairment). Steps and time taken to walk 9.144 meters were measured. Total ventricular volume (TVV) and intracranial volume (ICV) were measured on T1-weighted MRI using manual tracing software. WMC were rated on axial T2-weighted, dual-echo or FLAIR MR images using a visual scale.

Results:

TVV (cm3) (PD: 36.48 ± 15.93; controls: 32.16 ± 14.20, p = 0.21) and WMC did not differ between groups (PD: 3.7 ± 4.2; controls: 3.2 ± 3.1, p = 0.55). Age correlated positively with ICV-corrected TVV and WMC in PD (cTVV: r = 0.48, p = 0.003; WMC: r=0.42, p=0.01) and controls (cTVV: r = 0.31, p = 0.04; WMC: r=0.44, p=0.003). Subscore B (r = 0.42, p = 0.01) but not subscore A (r = 0.25, p = 0.14) correlated with cTVV in PD. Steps and walking time correlated with cTVV and WMC in PD; cadence correlated with cTVV and steps with WMC in controls. Age-adjustment eliminated correlations.

Conclusion:

Subscore B, but not subscore A correlated positively with ventricular volume in PD, though this association was accounted for by age. Age-related brain change super-imposed on PD may contribute to axial features.

Clinical Trials in Parkinson's Disease Dementia and Dementia with Lewy Bodies

Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB) are pathological overlapping and important causes of dementia for which clinical trials are in their infancy. Cholinesterase inhibitors may be of benefit in DLB and PDD, as suggested by placebo-controlled clinical trials of rivastigmine and donepezil. The anti-psychotic agent clozapine has been of benefit in PD and PDD, but other agents, such as quetiapine, require adequate assessment. Barriers to trials include pathological overlap that can lead to inaccuracies in clinical diagnosis, unavailability of a consensus definition for PDD, unanswered questions regarding natural history and the paucity of validated outcome measures. Motor impairment must be considered in patients with PDD and DLB; conversely, cognitive impairment should be assessed in trials targeting motor impairment in advanced PD. Potential targets for treatment include onset of dementia, cognitive impairment, behavioral impairment, functional decline, falls, nursing home placement, mortality, quality of life and economic impact. Biomarkers including neuroimaging and cerebrospinal fluid markers are not currently established. At present PDD and DLB are distinct entities by definition. Future studies, including clinical trials and biomarker studies, will help to further define the clinical and therapeutic implications of this distinction.

Conversion between mini-mental state examination, montreal cognitive assessment, and dementia rating scale-2 scores in Parkinson's disease

Cognitive impairment is one of the earliest, most common, and most disabling non-motor symptoms in Parkinson's disease (PD). Thus, routine screening of global cognitive abilities is important for the optimal management of PD patients. Few global cognitive screening instruments have been developed for or validated in PD patients. The Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Dementia Rating Scale-2 (DRS-2) have been used extensively for cognitive screening in both clinical and research settings. Determining how to convert the scores between instruments would facilitate the longitudinal assessment of cognition in clinical settings and the comparison and synthesis of cognitive data in multicenter and longitudinal cohort studies. The primary aim of this study was to apply a simple and reliable algorithm for the conversion of MoCA to MMSE scores in PD patients. A secondary aim was to apply this algorithm for the conversion of DRS-2 to both MMSE and MoCA scores. The cognitive performance of a convenience sample of 360 patients with idiopathic PD was assessed by at least two of these cognitive screening instruments. We then developed conversion scores between the MMSE, MoCA, and DRS-2 using equipercentile equating and log-linear smoothing. The conversion score tables reported here enable direct and easy comparison of three routinely used cognitive screening assessments in PD patients.

History of smoking and olfaction in Parkinson's disease

OBJECTIVE

Olfactory dysfunction is the most common pre-motor symptom in Parkinson's disease (PD), and smoking is known to be associated with lower risk of PD. This study tested the hypothesis that smoking is associated with better olfaction in PD.

METHODS

Smoking history was obtained from 76 PD subjects (22 with a history of smoking [smokers], 54 who never smoked [nonsmokers]), and 70 controls (17 smokers, 53 nonsmokers). Olfaction was assessed using the 40-item University of Pennsylvania Smell Identification Test (UPSIT). The olfactory scores between groups and subgroups were compared using analysis of covariance with adjustment for age, gender, and monoamine oxidase B (MAO-B) inhibitor usage.

RESULTS

Overall the olfactory score was lower in PD compared with controls (olfactory scores: 21.5 vs. 33.5, P < 0.0001). Among controls, there was no significant difference in olfaction between smokers and nonsmokers (olfactory scores, 33.2 vs. 34.2; P = 0.95). Among PD subjects, however, smokers scored significantly better regarding olfaction compared with nonsmokers (olfactory scores: 24.4 vs. 19.9, P = 0.02).

CONCLUSIONS

These data suggest that a history of smoking is associated with better olfaction among PD patients. The finding may be related to why smoking may be protective against PD. Further studies are needed to confirm this finding and investigate the underlying mechanisms.

Striatal shape in Parkinson's disease

Parkinson's disease (PD) is marked pathologically by nigrostriatal dopaminergic terminal loss. Histopathological and in vivo labeling studies demonstrate that this loss occurs most extensively in the caudal putamen and caudate head. Previous structural studies have suggested reduced striatal volume and atrophy of the caudate head in PD subjects. The spatial distribution of atrophy in the putamen, however, has not been characterized. We aimed to delineate the specific locations of atrophy in both of these striatal structures. T1- and T2-weighted brain MR (3T) images were obtained from 40 PD and 40 control subjects having no dementia and similar age and gender distributions. Shape analysis was performed using doubly segmented regions of interest. Compared to controls, PD subjects had lower putamen (p = 0.0003) and caudate (p = 0.0003) volumes. Surface contraction magnitudes were greatest on the caudal putamen (p ≤ 0.005) and head and dorsal body of the caudate (p ≤ 0.005). This spatial distribution of striatal atrophy is consistent with the known pattern of dopamine depletion in PD and may reflect global consequences of known cellular remodeling phenomena.

Visual exploration in Parkinson's disease and Parkinson's disease dementia

Parkinson's disease, typically thought of as a movement disorder, is increasingly recognized as causing cognitive impairment and dementia. Eye movement abnormalities are also described, including impairment of rapid eye movements (saccades) and the fixations interspersed between them. Such movements are under the influence of cortical and subcortical networks commonly targeted by the neurodegeneration seen in Parkinson's disease and, as such, may provide a marker for cognitive decline. This study examined the error rates and visual exploration strategies of subjects with Parkinson's disease, with and without cognitive impairment, whilst performing a battery of visuo-cognitive tasks. Error rates were significantly higher in those Parkinson's disease groups with either mild cognitive impairment (P = 0.001) or dementia (P < 0.001), than in cognitively normal subjects with Parkinson's disease. When compared with cognitively normal subjects with Parkinson's disease, exploration strategy, as measured by a number of eye tracking variables, was least efficient in the dementia group but was also affected in those subjects with Parkinson's disease with mild cognitive impairment. When compared with control subjects and cognitively normal subjects with Parkinson's disease, saccade amplitudes were significantly reduced in the groups with mild cognitive impairment or dementia. Fixation duration was longer in all Parkinson's disease groups compared with healthy control subjects but was longest for cognitively impaired Parkinson's disease groups. The strongest predictor of average fixation duration was disease severity. Analysing only data from the most complex task, with the highest error rates, both cognitive impairment and disease severity contributed to a predictive model for fixation duration [F(2,76) = 12.52, P ≤ 0.001], but medication dose did not (r = 0.18, n = 78, P = 0.098, not significant). This study highlights the potential use of exploration strategy measures as a marker of cognitive decline in Parkinson's disease and reveals the efficiency by which fixations and saccades are deployed in the build-up to a cognitive response, rather than merely focusing on the outcome itself. The prolongation of fixation duration, present to a small but significant degree even in cognitively normal subjects with Parkinson's disease, suggests a disease-specific impact on the networks directing visual exploration, although the study also highlights the multi-factorial nature of changes in exploration and the significant impact of cognitive decline on efficiency of visual search.

Screening for DSM-IV-TR cognitive disorder NOS in Parkinson's disease using the Mattis Dementia Rating Scale

OBJECTIVE

This study explores the utility of the Mattis Dementia Rating Scale (MDRS) as a screening tool for the Diagnostic and Statistical Manual for Mental Disorders 4th edition (DSM-IV-TR) diagnosis cognitive disorder not otherwise specified (NOS) in Parkinson's disease (PD).

METHODS

A total of 125 individuals with PD were diagnosed using DSM-IV-TR criteria for cognitive disorder NOS and dementia. Receiver operating characteristics (ROC) tested the discriminant validity of the MDRS, with the clinician's diagnosis serving as the gold standard.

RESULTS

The MDRS ROC curve to discriminate subjects with cognitive disorder NOS from non-demented subjects had an area under the curve of 0.59 (standard error = 0.08, 95% CI: 0.43-0.74).

CONCLUSIONS

The MDRS is not effective for identifying PD patients with cognitive disorder NOS without dementia.

Predictors of discrepancies in Parkinson's disease patient and caregiver ratings of apathy, disinhibition, and executive dysfunction before and after diagnosis

Parkinson’s disease (PD) patient and caregiver reports of patient functioning are often used interchangeably in clinical and research settings; however, the consistency of these reports is largely unknown. This study aimed to investigate the consistency and predictors of discrepancy between self- and caregiver reports of patient apathy, disinhibition, and executive dysfunction. Fifty-one pairs of nondemented PD patients and their caregivers completed the frontal systems behavior scale (FrSBe). Patients were administered a neuropsychological battery, and mood and burden were assessed in a subset of caregivers. Patients and caregivers significantly differed in their ratings of all retrospective prediagnosis behaviors and current levels of disinhibition. Current levodopa equivalent dosages predicted patient-caregiver rating differences in prediagnosis and current apathy and current executive dysfunction, while patient motor function, cognition, and mood failed to predict any disparities in ratings. Caregiver burden and depression were associated with apathy rating discrepancies, while burden was associated with discrepancies in ratings of disinhibition. These results suggest that consistency of patient and caregiver behavioral ratings may vary depending on the behavior assessed; and underscore the importance of considering the reporter when using subjective measures, as discrepancies in behavioral reports may be influenced by specific patient and/or caregiver symptoms or factors.

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.

Neurocognitive speed and inconsistency in Parkinson's disease with and without incipient dementia: an 18-month prospective cohort study

We examined two-wave longitudinal changes in two indicators of neurocognitive speed (i.e., mean rate, intraindividual variability) using one simple and three complex reaction time tasks. Participants included idiopathic Parkinson's disease (PD) patients, with and without incipient dementia, and normal controls. At baseline, there were 45 patients (26 men, 19 women) with idiopathic PD who ranged from 65 to 84 years (M = 71.3; SD = 4.5) and 47 matched controls (27 men, 20 women) who ranged from 65 to 84 years (M = 71.4; SD = 4.9). The 18-month longitudinal sample comprised of 74 returning participants (43 controls; 31 PD patients) who had no cognitive impairment or dementia at both waves. Ten of the 31 PD patients returning for Time 3 had dementia or cognitive impairment. These constituted the PD with incipient dementia (PDID) group. Repeated measures analyses of variance showed that the PD and PDID groups were slower over time on the reaction time tasks, whereas the controls improved their performance over time on all tasks. Inconsistency distinguished the two clinical groups (i.e., the PDID group but not the PD group became more inconsistent over time). Changes in neurocognitive speed and inconsistency may be valid clinical markers of PDID.

Influence of socio-demographic characteristics on DRS-2 performance in Spanish-speaking older adults

The present study compared the performance of English- and Spanish-speaking healthy controls (HCs) on the Spanish translation of the Dementia Rating Scale-Second edition (ST-DRS-2) and examined the classification accuracy of the ST-DRS-2 and Mini-Mental State Examination (MMSE) with an age- and education-matched clinical sample. In contrast to previous findings with English-speakers, a stronger relationship was observed between ST-DRS-2 Total scores and education than with age, and despite being matched on both of these variables, English-speaking HCs significantly out-performed their Spanish-speaking counterparts on the ST-DRS-2. The greatest between-group difference was found on the Memory subscale, wherein the majority of errors committed by Spanish-speaking HCs were significantly related to level of acculturation. ST-DRS-2 Total and Memory subscale scores produced greater classification accuracy than the MMSE; however, ST-DRS-2 Total scores yielded the greatest corresponding rates of sensitivity and specificity. Normative data are provided and recommended to improve the ST-DRS-2's diagnostic accuracy with Spanish-speakers.

Sensitivity and specificity of Addenbrooke's Cognitive Examination, Mattis Dementia Rating Scale, Frontal Assessment Battery and Mini Mental State Examination for diagnosing dementia in Parkinson's disease

INTRODUCTION

Among the non-motor features of Parkinson's disease (PD), cognitive impairment is one of the most troublesome problems. Highly sensitive and specific screening instruments for detecting dementia in PD (PDD) are required in the clinical practice.

METHODS

In our study we evaluated the sensitivity and specificity of different neuropsychological tests (Addenbrooke's Cognitive Examination, ACE; Frontal Assessment Battery, FAB and Mattis Dementia Rating Scale, MDRS) in 73 Parkinson's disease patients without depression. By receiver operating characteristic curve analysis, these screening instruments were tested against the recently established clinical diagnostic criteria of PDD.

RESULTS

Best cut-off score for ACE to identify PDD was 80 points (sensitivity = 74.0%, specificity = 78.1%). For FAB the most optimal cut-off value was 12 points (sensitivity = 66.3%, specificity = 72.2%); whereas for MDRS it was 125 points (sensitivity = 89.8%, specificity = 98.3%). Among the examined test batteries, MDRS had the best clinicometric profile for detecting PDD.

CONCLUSION

Although the types of applied screening instruments might differ from movement disorder clinic to clinic within a country, determination of the most specific and sensitive test for the given population remains to be an important task. Our results demonstrated that the specificity and sensitivity of MDRS was better than those of ACE, FAB and MMSE in Hungary. However, further studies with larger sample size and more uniform criteria for participation are required to determine the most suitable screening instrument for cognitive impairment.

Cognitive assessment instruments in Parkinson's disease patients undergoing deep brain stimulation

Deep Brain Stimulation (DBS) is a widely used surgical technique in individuals with Parkinson's disease (PD) that can lead to significant reductions in motor symptoms.

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.

Impact of anxiety on quality of life in Parkinson's disease

In Parkinson's disease (PD), both the patient and the health care provider look for ways to preserve the patient's quality of life. Many studies focus on the impact of depression and motor disability on poor life quality but neglect to examine the role of anxiety. We investigated the impact of anxiety and depression on health-related quality of life in PD, using the Parkinson's Disease Quality of Life measure (PDQ-39). Symptoms of anxiety, more than depression, cognitive status, or motor stage, significantly affected quality of life in 38 nondemented patients with mild-to-moderate motor disability. Stepwise regression analyses revealed that anxiety explained 29% of the variance in the PDQ-39 sum score, and depression explained 10% of the variance beyond that accounted for by anxiety. The findings suggest that primary management of anxiety as well as depression may be important to optimizing the quality of life of PD patients.

Visual symptoms in Parkinson's disease and Parkinson's disease dementia

Visual symptoms are common in PD and PD dementia and include difficulty reading, double vision, illusions, feelings of presence and passage, and complex visual hallucinations. Despite the established prognostic implications of complex visual hallucinations, the interaction between cognitive decline, visual impairment, and other visual symptoms remains poorly understood. Our aim was to characterize the spectrum of visual symptomatology in PD and examine clinical predictors for their occurrence. Sixty-four subjects with PD, 26 with PD dementia, and 32 age-matched controls were assessed for visual symptoms, cognitive impairment, and ocular pathology. Complex visual hallucinations were common in PD (17%) and PD dementia (89%). Dementia subjects reported illusions (65%) and presence (62%) more frequently than PD or control subjects, but the frequency of passage hallucinations in PD and PD dementia groups was equivalent (48% versus 69%, respectively; P = 0.102). Visual acuity and contrast sensitivity was impaired in parkinsonian subjects, with disease severity and age emerging as the key predictors. Regression analysis identified a variety of factors independently predictive of complex visual hallucinations (e.g., dementia, visual acuity, and depression), illusions (e.g., excessive daytime somnolence and disease severity), and presence (e.g., rapid eye movement sleep behavior disorder and excessive daytime somnolence). Our results demonstrate that different "hallucinatory" experiences in PD do not necessarily share common disease predictors and may, therefore, be driven by different pathophysiological mechanisms. If confirmed, such a finding will have important implications for future studies of visual symptoms and cognitive decline in PD and PD dementia.

Validity of the Mattis Dementia Rating Scale to detect mild cognitive impairment in Parkinson's disease and REM sleep behavior disorder

BACKGROUND/AIMS

Mild cognitive impairment (MCI) is frequent in Parkinson's disease (PD) and idiopathic REM sleep behavior disorder (iRBD). However, only a few studies have evaluated the validity of brief cognitive measures to detect MCI in PD or iRBD using standard diagnostic criteria for MCI. Our aim was to evaluate the validity of the Mini-Mental State Examination (MMSE) and the Mattis Dementia Rating Scale (DRS-2) to detect MCI in PD and iRBD.

METHODS

Forty PD patients and 34 iRBD patients were studied. Receiver operating characteristic curves were created for both tests to assess their effectiveness in identifying MCI in PD and iRBD.

RESULTS

In PD, a normality cutoff of 138 on the DRS-2 yielded the best balance between sensitivity (72%) and specificity (86%) with a correct classification of 80%. In iRBD, the optimal normality cutoff was 141 on the DRS-2, with a sensitivity of 90%, a specificity of 71% and a correct classification of 82%. No cutoff for the MMSE was found to have acceptable sensitivity or specificity.

CONCLUSION

The DRS-2 has satisfactory validity to detect MCI in PD or iRBD. The MMSE proved to be invalid as a screening test for MCI in both populations.

Cognitive impairment in nondemented Parkinson's disease

A substantial percentage of patients with newly diagnosed Parkinson's disease without dementia are reported to be affected by cognitive impairment (CI). In practice, however, CI is underrecognized, as the signs may not be apparent in early-stage disease and many routine assessment tools lack the sensitivity to detect subtle cognitive dysfunction. Patients with PD and mild CI (MCI) may have a higher risk of developing dementia than cognitively intact PD patients; however, it is not currently known which patients with CI are at increased risk of developing dementia. This review summarizes current knowledge about CI in nondemented PD; it discusses the structural and functional changes associated with CI and addresses areas of unmet needs. We focus on questions that should be addressed in future studies to achieve consensus on its characteristics and definition, pathophysiology, epidemiology, diagnosis and assessment, and treatment and management.

AAV2-GAD gene therapy for advanced Parkinson's disease: a double-blind, sham-surgery controlled, randomised trial

BACKGROUND

Gene transfer of glutamic acid decarboxylase (GAD) and other methods that modulate production of GABA in the subthalamic nucleus improve basal ganglia function in parkinsonism in animal models. We aimed to assess the effect of bilateral delivery of AAV2-GAD in the subthalamic nucleus compared with sham surgery in patients with advanced Parkinson's disease.

METHODS

Patients aged 30-75 years who had progressive levodopa-responsive Parkinson's disease and an overnight off-medication unified Parkinson's disease rating scale (UPDRS) motor score of 25 or more were enrolled into this double-blind, phase 2, randomised controlled trial, which took place at seven centres in the USA between Nov 17, 2008, and May 11, 2010. Infusion failure or catheter tip location beyond a predefined target zone led to exclusion of patients before unmasking for the efficacy analysis. The primary outcome measure was the 6-month change from baseline in double-blind assessment of off-medication UPDRS motor scores. This trial is registered with ClinicalTrials.gov, NCT00643890.

FINDINGS

Of 66 patients assessed for eligibility, 23 were randomly assigned to sham surgery and 22 to AAV2-GAD infusions; of those, 21 and 16, respectively, were analysed. At the 6-month endpoint, UPDRS score for the AAV2-GAD group decreased by 8·1 points (SD 1·7, 23·1%; p<0·0001) and by 4·7 points in the sham group (1·5, 12·7%; p=0·003). The AAV2-GAD group showed a significantly greater improvement from baseline in UPDRS scores compared with the sham group over the 6-month course of the study (RMANOVA, p=0·04). One serious adverse event occurred within 6 months of surgery; this case of bowel obstruction occurred in the AAV2-GAD group, was not attributed to treatment or the surgical procedure, and fully resolved. Other adverse events were mild or moderate, likely related to surgery and resolved; the most common were headache (seven patients in the AAV2-GAD group vs two in the sham group) and nausea (six vs two).

INTERPRETATION

The efficacy and safety of bilateral infusion of AAV2-GAD in the subthalamic nucleus supports its further development for Parkinson's disease and shows the promise for gene therapy for neurological disorders.

FUNDING

Neurologix.

Lateral ventricle volume is poor predictor of post unilateral DBS motor change for Parkinson's disease

BACKGROUND

Deep Brain Stimulation (DBS) surgery can effectively treat many debilitating motor symptoms of Parkinson's disease (PD), but axial symptom improvement is variable. Predictors for post-DBS axial symptom performance have yet to be identified. Pre-surgery ventricle volume may be one predictor, for increasing ventricular size has been associated with worsening gait disturbance. In PD, ventricle size may also increase with the advancement of motor symptoms.

OBJECTIVE

To examine the hypotheses that 1) lateral ventricular volumes would predict motor and axial motor symptom change from pre to four months post unilateral DBS, and 2) PD patients have larger ventricle volumes contralateral to side of symptom onset.

METHODS

Idiopathic PD patients (n = 37) completed pre-surgery volumetric brain scans and UPDRS motor testing (off-medication), unilateral DBS (Globus Pallidus interna, n = 11; subthalamic nucleus, n = 26), and 4-month follow-up motor assessments (on-stimulation). Ventricle volumes were normalized using total intracranial volume.

RESULTS

Total ventricular volume as well as measurements of contralateral/ipsilateral volumes to side of symptom onset or DBS lead placement did not predict outcome motor measures or correlate to axial motor change. Patients improving at least 2 standard errors of measurement (n = 6) did not have smaller ventricles relative to those without significant change. Post-operative hemorrhage (n = 1) had ventricle volumes similar to the group average. There was no asymmetry in ventricular volume by side of onset or side of lead placement.

CONCLUSION

Ventricular volume was a poor predictor of acute motor change following DBS. Asymmetrical ventricles may not be a consistent imaging marker for PD motor dysfunction.

Association between cognition and function in patients with Parkinson disease with and without dementia

Patients with Parkinson's disease (PD) often have cognitive deficits from the time of diagnosis. Except in patients with dementia, the impact of cognitive symptoms on daily function is not well documented. This study had two objectives: (1) to determine the functional significance of cognitive deficits in nondemented patients with PD and (2) to assess the sensitivity of two measures of global cognitive abilities to identify individuals with impaired ADL function. One hundred eleven subjects with PD and a range of cognitive abilities were included. Of these, 20 were diagnosed with PDD. All subjects were assessed with the Mattis Dementia Rating Scale to two (DRS-2) and the Mini-Mental State Examination (MMSE). ADL function was reported by an informant using the Alzheimer's Disease Cooperative Study Activities of Daily Living Inventory (ADCS-ADL). The ability of the DRS-2 and MMSE to capture the impact of cognitive impairment on ADL function was assessed in the entire cohort and in subsets of nondemented individuals. After adjustment for covariates, cognition as measured by the DRS-2 was strongly related to ADL function in the entire cohort (partial correlation coefficient = 0.55, P < 0.001). The association remained strong when only nondemented subjects were included (r = 0.42, P < 0.001). The DRS-2 was significantly more accurate than the MMSE, particularly for detecting milder degrees of ADL impairment (ROC area = 0.87 vs. 0.75, P = 0.0008). Cognition is associated with impairment in ADL function, even in nondemented patients with PD. However, sensitive cognitive assessment measures may be needed to identify these functionally relevant impairments.

CSF amyloid {beta} 1-42 predicts cognitive decline in Parkinson disease

OBJECTIVE

Cognitive decline associated with Parkinson disease (PD) is common and highly disabling. Biomarkers that help identify patients at risk for cognitive decline would be useful additions to the clinical management of the disease.

METHODS

A total of 45 patients with PD were enrolled in this prospective cohort study and had at least 1 yearly longitudinal follow-up evaluation. CSF was collected at baseline and cognition was assessed at baseline and follow-up visits using the Mattis Dementia Rating Scale (DRS-2). CSF was tested for amyloid β 1-42 (Aβ(1-42)), p-tau(181p), and total tau levels using the Luminex xMAP platform. Mixed linear models were used to test for associations between baseline CSF biomarker levels and change in cognition over time.

RESULTS

Lower baseline CSF Aβ(1-42) was associated with more rapid cognitive decline. Subjects with CSF Aβ(1-42) levels ≤192 pg/mL declined an average of 5.85 (95% confidence interval 2.11-9.58, p = 0.002) points per year more rapidly on the DRS-2 than subjects above that cutoff, after adjustment for age, disease duration, and baseline cognitive status. CSF total tau and p-tau(181p) levels were not significantly associated with cognitive decline.

CONCLUSIONS

Reduced CSF Aβ(1-42) was an independent predictor of cognitive decline in patients with PD. This observation is consistent with previous research showing that Alzheimer disease pathology contributes to cognitive impairment in PD. This biomarker may provide clinically useful prognostic information, particularly if combined with other risk factors for cognitive impairment in PD.

Executive functions deficit in Parkinson's disease with amnestic mild cognitive impairment

Recent studies suggest that onset of dementia in Parkinson's disease (PD) is preceded by a phase known as mild cognitive impairment (MCI). Different clinical subtypes of MCI in PD were found. The objective of this study was to investigate whether patients with PD diagnosed with amnestic MCI (aPD-MCI) have also subtle deficits in other cognitive domains and especially in attention/executive functions and, therefore to clarify whether all subcomponents of executive control are equally affected in aPD-MCI. We investigated 23 patients with aPD-MCI (modified Petersen's criteria) and 25 normal controls. Relative to controls, the aPD-MCI group showed significant deficits with reference to tasks that encompass various aspects of attention/executive functions, including Trail Making Test, Stroop test, Modified Card Sorting Test, and digit span backward, as well as phonemic and semantic verbal fluency. This suggests that executive dysfunction is consistently presented in PD with MCI, even in ''amnestic'' PD-MCI due to cortical-subcortical dysfunction.

Selective effects of aging on brain white matter microstructure: a diffusion tensor imaging tractography study

We examined age-related changes in the cerebral white matter. Structural magnetic resonance images (MRIs) and diffusion tensor images (DTIs) were acquired from 69 healthy subjects aged 22-84 years. Quantitative DTI tractography was performed for nine different white matter tracts to determine tract volume, fractional anisotropy (FA), mean diffusivity (MD), axial, and radial diffusivities. We used automated and manual segmentation to determine volumes of gray matter (GM), white mater (WM), cerebrospinal fluid (CSF), and intracranial space. The results showed significant effects of aging on WM, GM, CSF volumes, and selective effects of aging on structural integrity of different white matter tracts. WM of the prefrontal region was the most vulnerable to aging, while temporal lobe connections, cingulum, and parieto-occipital commissural connections showed relative preservation with age. This study was cross-sectional, and therefore, additional longitudinal studies are needed to confirm our findings.

Relationship between mild cognitive impairment and falls in older people with and without Parkinson's disease: 1-Year Prospective Cohort Study

We conducted a 12-month longitudinal cohort study of 102 older people without dementia (52 Parkinson's Disease [PD]; 50 age- and sex-matched controls) to determine (1) if mild cognitive impairment predicts falls in older people with or without PD and (2) how baseline falls, a history of freezing and Hoehn and Yahr stage affected the association between cognitive impairment and multiple falls in PD patients. Cognitive impairment was defined as the sum of impairments on the caregiver-rated Clinical Dementia Rating Scale (CCDRSum>0). Overall the mean age (SD) was 71.5 (4.7) years, 42% were women, 26% had fallen and 14% had cognitive impairment at baseline. Thirty-one percent (15/52) of PD patients vs 12% (6/50) of controls fell more than once during 12-month follow-up, p=0.04. When combined in a 2-predictor model for the entire cohort, the adjusted odds ratios [aOR] for falling were significantly increased for cognitive impairment at baseline (aOR: 4.8, 95% CI: 1.3-18.2) and prior falls (aOR: 7.4, 95% CI: 2.4-22.3). The overall accuracy of the model was 82%, with low sensitivity of 19% but high specificity of 99%. In the PD subgroup, the overall accuracy of the same prediction model was 79%, with much better sensitivity of 73% but a lower specificity of 81%. We conclude that mild cognitive impairment might contribute to falls risk beyond conventional risk factors in older people with and without PD.

Computational Models Inform Clinical Science and Assessment: An Application to Category Learning in Striatal-Damaged Patients

In this article we develop a new model of classification that is intermediate between the static, single strategy decision-bound models and the dynamic trial by trial multiple systems model, dCOVIS. The new model, referred to as the sCOVIS model, assumes hypothesis-testing and procedural-based subsystems are active on each trial, but that the parameters that govern behavior of the system are fixed (static) within a block of trials. To determine the clinical utility of the model, it was applied to nonlinear information-integration classification data from patients with Parkinson's (PD) and Huntington's disease (HD). In one application, the models suggest that the locus of HD patients' nonlinear information-integration deficits is in their increased reliance on hypothesis-testing strategies, whereas the locus of PD patients' deficit is in the application of sub-optimal procedural-based strategies. In a second application, the weight associated with the hypothesis-testing subsystem is shown to account for a significant amount of the variance in longitudinal cognitive decline in non-demented PD patients above and beyond that predicted by accuracy alone. Together, the accuracy rate and this model index account for 72% of the total variance associated with cognitive decline in this sample of PD patients. Interestingly, the Wisconsin Card Sort task added no additional predictive power above and beyond that predicted by nonlinear accuracy alone.