Mild cognitive impairment in Parkinson's disease

Prediction of Cognitive Heterogeneity in Parkinson's Disease: A 4-Year Longitudinal Study Using Clinical, Neuroimaging, Biological and Electrophysiological Biomarkers

OBJECTIVE

Cognitive impairment in Parkinson's disease (PD) can show a very heterogeneous trajectory among patients. Here, we explored the mechanisms involved in the expression and prediction of different cognitive phenotypes over 4 years.

METHODS

In 2 independent cohorts (total n = 475), we performed a cluster analysis to identify trajectories of cognitive progression. Baseline and longitudinal level II neuropsychological assessments were conducted, and baseline structural magnetic resonance imaging, resting electroencephalogram and neurofilament light chain plasma quantification were carried out. Linear mixed-effects models were used to study longitudinal changes. Risk of mild cognitive impairment and dementia were estimated using multivariable hazard regression. Spectral power density from the electroencephalogram at baseline and source localization were computed.

RESULTS

Two cognitive trajectories were identified. Cluster 1 presented stability (PD-Stable) over time, whereas cluster 2 showed progressive cognitive decline (PD-Progressors). The PD-Progressors group showed an increased risk for evolving to PD mild cognitive impairment (HR 2.09; 95% CI 1.11-3.95) and a marked risk for dementia (HR 4.87; 95% CI 1.34-17.76), associated with progressive worsening in posterior-cortical-dependent cognitive processes. Both clusters showed equivalent clinical and sociodemographic characteristics, structural magnetic resonance imaging, and neurofilament light chain levels at baseline. Conversely, the PD-Progressors group showed a fronto-temporo-occipital and parietal slow-wave power density increase, that was in turn related to worsening at 2 and 4 years of follow-up in different cognitive measures.

INTERPRETATION

In the absence of differences in baseline cognitive function and typical markers of neurodegeneration, the further development of an aggressive cognitive decline in PD is associated with increased slow-wave power density and with a different profile of worsening in several posterior-cortical-dependent tasks. ANN NEUROL 2024;96:981-993.

Cognitive phenotyping of GBA1-Parkinson's disease: A study on deep brain stimulation outcomes

BACKGROUND

Heterozygous variants in the glucocerebrosidase (GBA1) gene are the most common genetic risk factor for Parkinson's Disease (PD). GBA1-PD patients exhibit earlier disease onset, severe motor impairment, and heightened cognitive decline. Deep Brain Stimulation (DBS) offers motor improvement for PD patients, but its cognitive effects, particularly in GBA1-PD, are debated.

METHODS

This study involved 96 PD patients who underwent subthalamic nucleus DBS at Hospital de la Santa Creu i Sant Pau between 2004 and 2023. Clinical and neuropsychological assessments were conducted pre- and post-surgery, focusing on Mattis Dementia Rating Scale (MDRS) and Frontal Systems Behavior Scale (FrSBe). Patients were categorized into GBA1-PD and non-GBA1-PD groups, with non-GBA1-PD further divided into cognitive fast-progressors and slow-progressors.

RESULTS

GBA1 variants were present in 13.5 % of patients. GBA1-PD patients showed greater cognitive decline over time, particularly in attention, conceptualization, and memory, compared to non-GBA1-PD. Non-GBA1-PD fast-progressors exhibited significant cognitive deterioration in initiation and conceptualization within the first year post-DBS. Motor outcomes improved similarly across all groups, but slow-progressors showed a greater reduction in Levodopa Equivalent Daily Dose (LEDD).

CONCLUSIONS

GBA1-PD patients experience more rapid cognitive decline, particularly in posterior-cortical and fronto-striatal functions. Additionally, a subset of non-GBA1-PD patients shows significant early cognitive decline post-DBS, especially in executive functions. Baseline MDRS scores do not predict cognitive outcomes, highlighting the need for further research to refine prognostic tools. Despite cognitive challenges, GBA1-PD patients benefit from DBS in terms of motor outcomes, underscoring the importance of individualized assessments for DBS suitability, regardless of genetic status.

Synaptic protein CSF levels relate to memory scores in individuals without dementia

INTRODUCTION

We investigated how cerebrospinal fluid levels of synaptic proteins associate with memory function in normal cognition (CN) and mild cognitive impairment (MCI), and investigated the effect of amyloid positivity on these associations.

METHODS

We included 242 CN (105(43%) abnormal amyloid), and 278 MCI individuals (183(66%) abnormal amyloid) from EMIF-AD MBD and ADNI. For 181 (EMIF-AD MBD) and 36 (ADNI) proteins with a synaptic annotation in SynGO, associations with word learning recall were analysed with linear models.

RESULTS

Subsets of synaptic proteins showed lower levels with worse recall in preclinical AD (EMIF-AD MBD: 7, ADNI: 5 proteins, none overlapping), prodromal AD (EMIF-AD MBD only, 27 proteins) and non-AD MCI (EMIF-AD MBD: 1, ADNI: 7 proteins). The majority of these associations were specific to these groups.

DISCUSSION

Synaptic disturbance-related memory impairment occurred very early in AD, indicating it may be relevant to develop therapies targeting the synapse early in the disease.

Does the Montreal Cognitive Assessment (MoCA) identify cognitive impairment profiles in Parkinson's disease? An exploratory study

An important proportion of patients with Parkinson's Disease (PD) present signs of cognitive impairment, although this is heterogeneous. In an attempt to classify this, the dual syndrome hypothesis distinguishes between two profiles: one defined by attentional and executive problems with damage in anterior cerebral regions, and another with mnesic and visuospatial alterations, with damage in posterior cerebral regions. The Montreal Cognitive Assessment (MoCA) is one of the recommended screening tools, and one of the most used, to assess cognitive impairment in PD. However, its ability to specifically identify these two profiles of cognitive impairment has not been studied. The aim of this study was, therefore, to analyze the capacity of the MoCA to detect cognitive impairment, and also to identify anterior and posterior profiles defined by the dual syndrome hypothesis. For this purpose, 59 patients with idiopathic PD were studied with the MoCA and a neuropsychological battery of tests covering all cognitive domains. Results of logistic regression analysis with ROC (Receiver Operating Characteristic) curves showed that MoCA detected cognitive impairment and identified patients with a profile of anterior/attentional and executive deficit, with acceptable sensibility and specificity. However, it did not identify patients with a posterior/mnesic-visuospatial impairment. We discuss the reasons for the lack of sensitivity of MoCA in this profile, and other possible implications of these results with regards the usefulness of this tool to assess cognitive impairment in PD.

Cognitive disorders in advanced Parkinson's disease: challenges in the diagnosis of delirium

Parkinson's disease (PD) is a neurodegenerative condition that is frequently associated with cognitive disorders. These can arise directly from the primary disease, or be triggered by external factors in susceptible individuals due to PD or other predisposing factors. The cognitive disorders encompass PD-associated cognitive impairment (PD-CI), delirium, PD treatment-associated cognitive side effects, cognitive non-motor fluctuations, and PD-associated psychosis. Accurate diagnosis of delirium is crucial because it often stems from an underlying disease that may be severe and require specific treatment. However, overlapping molecular mechanisms are thought to be involved in both delirium and PD, leading to similar clinical symptoms. Additionally, there is a bidirectional interaction between delirium and PD-CI, resulting in frequent concurrent processes that further complicate diagnosis. No reliable biomarker is currently available for delirium, and the diagnosis is primarily based on clinical criteria. However, the screening tools validated for diagnosing delirium in the general population have not been specifically validated for PD. Our review addresses the current challenges in the diagnosis of these cognitive disorders and highlights existing gaps within this field.

Parkinson disease psychosis: from phenomenology to neurobiological mechanisms

Parkinson disease (PD) psychosis (PDP) is a spectrum of illusions, hallucinations and delusions that are associated with PD throughout its disease course. Psychotic phenomena can manifest from the earliest stages of PD and might follow a continuum from minor hallucinations to structured hallucinations and delusions. Initially, PDP was considered to be a complication associated with dopaminergic drug use. However, subsequent research has provided evidence that PDP arises from the progression of brain alterations caused by PD itself, coupled with the use of dopaminergic drugs. The combined dysfunction of attentional control systems, sensory processing, limbic structures, the default mode network and thalamocortical connections provides a conceptual framework to explain how new incoming stimuli are incorrectly categorized, and how aberrant hierarchical predictive processing can produce false percepts that intrude into the stream of consciousness. The past decade has seen the publication of new data on the phenomenology and neurobiological basis of PDP from the initial stages of the disease, as well as the neurotransmitter systems involved in PDP initiation and progression. In this Review, we discuss the latest clinical, neuroimaging and neurochemical evidence that could aid early identification of psychotic phenomena in PD and inform the discovery of new therapeutic targets and strategies.

Functional alterations in resting-state networks for Theory of Mind in Parkinson's disease

In Parkinson's disease (PD), impairment of Theory of Mind (ToM) has recently attracted an increasing number of neuroscientific investigations. If and how functional connectivity of the ToM network is altered in PD is still an open question. First, we explored whether ToM network connectivity shows potential PD-specific functional alterations when compared to healthy controls (HC). Second, we tested the role of the duration of PD in the evolution of functional alterations in the ToM network. Between-group connectivity alterations were computed adopting resting-state functional magnetic resonance imaging (rs-fMRI) data of four groups: PD patients with short disease duration (PD-1, n = 72); PD patients with long disease duration (PD-2, n = 22); healthy controls for PD-1 (HC-1, n = 69); healthy controls for PD-2 (HC-2, n = 22). We explored connectivity differences in the ToM network within and between its three subnetworks: Affective, Cognitive and Core. PD-1 presented a global pattern of decreased functional connectivity within the ToM network, compared to HC-1. The alterations mainly involved the Cognitive and Affective ToM subnetworks and their reciprocal connections. PD-2-those with longer disease duration-showed an increased connectivity spanning the entire ToM network, albeit less consistently in the Core ToM network, compared to both the PD-1 and the HC-2 groups. Functional connectivity within the ToM network is altered in PD. The alterations follow a graded pattern, with decreased connectivity at short disease duration, which broadens to a generalized increase with longer disease duration. The alterations involve both the Cognitive and Affective subnetworks of ToM.

Treatment for cognitive and neuropsychiatric non-motor symptoms in Parkinson's disease: current evidence and future perspectives

INTRODUCTION

Non-motor symptoms (NMS) affect patients with Parkinson's disease (PD) from the prodromal to the advanced stages. NMS phenotypes greatly vary and have a huge impact on patients' and caregivers' quality of life (QoL). The management of cognitive and neuropsychiatric NMS remains an unmet need.

AREAS COVERED

The authors, herein, review the dopaminergic and non-dopaminergic pathogenesis, clinical features, assessment, and pharmacological and non-pharmacological treatments of cognitive and neuropsychiatric NMS in PD. They discuss the current evidence and report the findings of an overview of ongoing trials on pharmacological and selected non-pharmacological strategies.

EXPERT OPINION

The treatment of cognitive and neuropsychiatric NMS in PD is poorly explored, and therapeutic options are unsatisfactory. Pharmacological treatment of cognitive NMS is based on symptomatic active principles used in Alzheimer's disease. Dopamine agonists, selective serotonin, and serotonin-norepinephrine reuptake inhibitors have some evidence on PD-related depression. Clozapine, quetiapine, and pimavanserin may be considered for psychosis in PD. Evidence on the treatment of other neuropsychiatric NMS is limited or lacking. Addressing pathophysiological and clinical issues, which hamper solid evidence on the treatment of cognitive and neuropsychiatric NMS, may reduce the impact on QoL for PD patients and their caregivers.

Early identification of subjective cognitive functional decline among patients with Parkinson's disease: a longitudinal pilot study

Practical methods for early identification of Parkinson's disease (PD) mild cognitive impairment (PD-MCI) through changes in real-life daily functioning are scarce. The aim of the study was to examine whether the cognitive functional (CF) feature, comprising of seven self-reported Movement Disorder Society's (MDS) Unified Parkinson's Disease Rating Scale (UPDRS) items, predicts PD patients' cognitive functional status after a year. We conducted a 1-year follow-up of 34 PD patients (50-78 year; 70.6% men) suspected of MCI using the following measures: the MDS-UPDRS, UPDRS-CF feature, Beck Depression Inventory (BDI), Montreal Cognitive Assessment (MoCA), Trail Making Test (TMT), Parkinson's Disease Cognitive Functional Rating Scale (PD-CFRS), and Daily Living Questionnaire (DLQ). The first and second UPDRS-CF feature scores, and additional measures at the 1-year follow-up significantly correlated. Hierarchical regression revealed that the initial MoCA, TMT, and BDI scores predicted the second UPDRS-CF, and the first UPDRS-CF predicted 31% of the second PD-CFRS score variance. Depression moderated the relationship between the first UPDRS-CF score and the DLQ Part A. These results suggest practical, self-reported, daily functional markers for identifying gradual decline in PD patients. They consider the patients' heterogeneity, underlying cognitive pathology, and implications on daily functioning, health, and well-being.

Effects of mind-body exercises on cognitive impairment in people with Parkinson's disease: A mini-review

Parkinson's disease (PD) is an important health problem caused by the degeneration of brain neurons. Bradykinesia and lower balance ability seriously affect the quality of life of people with PD. Non-motor symptoms, such as cognitive impairment, accompany the course of the disease but still lack sufficient attention. In general, drugs combined with cognitive training are the most common ways to improve cognitive impairment in people with PD. However, long-term use of psychiatric drugs may lead to side effects such as brain death and movement disorders. Recently, mindfulness has been used by researchers in the treatment of cognitive impairment, because healthy older adults who engage in mind-body exercises for a long time have higher cognitive levels than normal aging populations. Mind-body exercise, as a therapy that combines concentration, breath control, and physical activity, is beneficial for improving practitioners' brain and mental health. Mind-body exercises such as Tai Chi, yoga, dance, and Pilates can improve cognitive performance in older adults with or without cognitive impairment. Therefore, mind-body exercise may be a feasible strategy for the treatment of cognitive impairment in people with PD. This study summarizes the latest evidence that mind-body exercises including Tai Chi, Qigong, yoga, and dance improve cognitive impairment associated with PD. We also explored the limitations of current mind-body exercise research, aiming to provide new ideas for improving mind-body exercise as a strategy to alleviate cognitive impairment in people with PD.

Capturing Subjective Mild Cognitive Decline in Parkinson’s Disease

This study aimed to capture subjective daily functional cognitive decline among patients with Parkinson’s disease. Participants (40–79 y; 78 with Parkinson’s disease and 41 healthy matched controls) completed the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS), Parkinson’s Disease Cognitive Functional Rating Scale (CFRS), Daily Living Questionnaire (DLQ), and Time Organisation and Participation Scale (TOPS) questionnaires. Patients with Parkinson’s disease were divided into groups with or without suspected mild cognitive decline according to their scores on the Cognitive Functional (CF) feature, which is based on certain items of the MDS-UPDRS. Significant between-group differences were found in the DLQ and TOPS scores. Significant correlations were found among the questionnaire results, with specific DLQ and TOPS items accounting for 35% of the variance in the CF feature, which correlated with daily cognitive functional states. This study’s results are relevant for detecting subtle deficits in Parkinson’s disease patients suspected of mild cognitive decline, which can affect health and quality of life and relates to risk for later dementia.

Caring for patients with cognitive dysfunction, fluctuations and dementia caused by Parkinson's disease

Cognitive dysfunction is one of the most prevalent non-motor symptoms in patients with Parkinson's disease (PD). While it tends to worsen in the later stages of disease, it can occur at any time, with 15-20% of patients exhibiting cognitive deficits at diagnosis (Aarsland et al., 2010; Goldman and Sieg, 2020). The characteristic features of cognitive dysfunction include impairment in executive function, visuospatial abilities, and attention, which vary in severity from subtle impairment to overt dementia (Martinez-Horta and Kulisevsky, 2019). To complicate matters, cognitive dysfunction is prone to fluctuate in PD patients, impacting diagnosis and the ability to assess progression and decision-making capacity. The diagnosis of cognitive impairment or dementia has a huge impact on patient independence, quality of life, life expectancy and caregiver burden (Corallo et al., 2017; Lawson et al., 2016; Leroi et al., 2012). It is therefore essential that physicians caring for patients with PD provide education, screening and treatment for this aspect of the disease. In this chapter, we provide a practical guide for the assessment and management of various degrees of cognitive dysfunction in patients with PD by approaching the disease at different stages. We address risk factors for cognitive dysfunction, prevention strategies prior to making the diagnosis, available tools for screening. Lastly, we review aspects of care, management and considerations, including decision-making capacity, that occur after the patient has been diagnosed with cognitive dysfunction or dementia.

Rotenone impairs learning and memory in mice through microglia-mediated blood brain barrier disruption and neuronal apoptosis

Rotenone is a neurotoxic pesticide widely used in agriculture. Dopaminergic neuron has long been considered as the target of rotenone. We recently reported that rotenone exposure also resulted in hippocampal and cortical neurodegeneration and cognitive dysfunction in mice. However, the mechanisms remain unknown. Here, we elucidated whether blood brain barrier (BBB) disruption and subsequent neuronal apoptosis mediated by microglial activation were involved in rotenone-elicited cognitive impairments. Results showed that rotenone dose-dependently elevated evens blue extravasation, fibrinogen accumulation and reduced expressions of tight junction proteins in the hippocampus and cortex of mice. Interestingly, microglial depletion and inactivation by PLX3397 and minocycline, respectively, markedly attenuated rotenone-elicited increase of BBB permeability, indicating a critical role of microglia. Furthermore, microglial depletion and inactivation were shown to abrogate rotenone-induced activation of matrix metalloproteinases 2 and 9 (MMP-2/-9), two important factors to regulate tight junction degradation and BBB permeability, in mice. Moreover, SB-3CT, a widely used MMP-2/-9 inhibitor, increased BBB integrity and simultaneously elevated expressions of tight junction proteins in rotenone-intoxicated mice. Finally, we found that SB-3CT significantly mitigated rotenone-induced neuronal apoptosis and synaptic loss as well as learning and memory impairments in mice. Altogether, this study revealed that rotenone elicited cognitive impairments in mice through microglia-mediated BBB disruption and neuronal apoptosis via MMP-2/-9, providing a novel aspect for the pathogenesis of pesticide-induced neurotoxicity and Parkinson's disease (PD)-related dementia.

Distinct Bile Acid Signature in Parkinson's Disease With Mild Cognitive Impairment

BACKGROUNDS

Bile acid (BA) plays a crucial role in various neurodegenerative diseases, including Parkinson's disease (PD). However, no clinical evidence supports BA's potential role in patients with PD with mild cognitive impairment (PD-MCI).

OBJECTIVES

This study aimed at investigating the differential BA profile between patients with PD-MCI and those with normal cognitive function (PD-NC).

METHODS

Ultra-high performance liquid chromatography-MS/MS was applied for BA quantitation. After between-group differences of the BA profile were addressed, orthogonal projections to latent structures-discriminant analysis (OPLS-DA) and the area under the receiver-operating-characteristic curve (AUC-ROC) were implemented for further verification.

RESULTS

Lower levels of chenodeoxycholic acid (CDCA), cholic acid (CA), and ursodeoxycholic acid (UDCA) were significantly associated with PD-MCI (p < 0.01 for both; VIP ≈ 2.67, 1.66, and 1.26, respectively). AUC-ROC were 78.1, 74.2, and 74.5% for CDCA, CA, and UDCA, respectively.

CONCLUSION

CA, CDCA, and UDCA might be distinct BA signatures for patients with PD-MCI.

Apathy Reflects Extra-Striatal Dopaminergic Degeneration in de novo Parkinson's Disease

BACKGROUND

Apathy represents a core neuropsychiatric symptom in Parkinson's disease (PD). As there is currently no established effective treatment for apathy in PD, further investigating the biological origin of this symptom is needed to design novel therapeutic strategies. Among the multiple neurotransmitter alterations that have been associated with apathy, the involvement of extra-striatal dopaminergic degeneration remains to be fully explored.

OBJECTIVE

To investigate whether apathy in PD reflects increased dopaminergic degeneration extending beyond striatal regions.

METHODS

In the de novo PD cohort of the Parkinson's Progression Markers Initiative (PPMI), we performed whole-brain I123-Ioflupane Single Photon Emission Computed Tomography (DAT-SPECT) analyses to characterize cross-sectional and longitudinal differences in DAT uptake associated with the presence of apathy. We also assessed the relationship between apathy and cognition in this sample, as apathy has been suggested to herald cognitive decline.

RESULTS

Apathetic PD patients (N = 70) had similar sociodemographic, clinical, and biomarker profiles compared to the non-apathetic group (N = 333) at baseline. However, apathy was associated with an increased risk of developing cognitive impairment after a four-year follow-up period (p = 0.006). Compared to non-apathetic patients, apathetic patients showed a widespread reduction of extra-striatal DAT uptake at baseline as well as an increased longitudinal loss of DAT uptake (corrected p < 0.05).

CONCLUSIONS

Isolated apathy in PD is associated with extra-striatal dopaminergic degeneration. As this abnormal dopamine depletion was in turn related to cognitive performance, this might explain, at least partially, the increased risk of apathetic PD patients to develop cognitive impairment or dementia.

Identifying comorbidities and lifestyle factors contributing to the cognitive profile of early Parkinson's disease

BACKGROUND

Identifying modifiable risk factors for cognitive impairment in the early stages of Parkinson's disease (PD) and estimating their impact on cognitive status may help prevent dementia (PDD) and the design of cognitive trials.

METHODS

Using a standard approach for the assessment of global cognition in PD and controlling for the effects of age, education and disease duration, we explored the associations between cognitive status, comorbidities, metabolic variables and lifestyle variables in 533 PD participants from the COPPADIS study.

RESULTS

Among the overall sample, 21% of participants were classified as PD-MCI (n = 114) and 4% as PDD (n = 26). The prevalence of hypertension, diabetes and dyslipidemia was significantly higher in cognitively impaired patients while no between-group differences were found for smoking, alcohol intake or use of supplementary vitamins. Better cognitive scores were significantly associated with regular physical exercise (p < 0.05) and cognitive stimulation (< 0.01). Cognitive performance was negatively associated with interleukin 2 (Il2) (p < 0.05), Il6 (p < 0.05), iron (p < 0.05), and homocysteine (p < 0.005) levels, and positively associated with vitamin B12 levels (p < 0.005).

CONCLUSIONS

We extend previous findings regarding the positive and negative influence of various comorbidities and lifestyle factors on cognitive status in early PD patients, and reinforce the need to identify and treat potentially modifiable variables with the intention of exploring the possible improvement of the global cognitive status of patients with PD.

Application of the Chinese Version of the Montreal Cognitive Assessment-Basic for Assessing Mild Cognitive Impairment in Parkinson's Disease

Mild cognitive impairment (MCI) is a common and pivotal non-motor symptom in Parkinson’s disease (PD). It is necessary to use the appropriate tools to characterize the cognitive profiles and identify the subjects at risk of MCI in clinical practice. A cohort of 207 non-demented patients with PD and 52 age- and gender-matched cognitively normal controls (NCs) underwent the Chinese Version of Montreal Cognitive Assessment-Basic (MoCA-BC) evaluation. Patients with PD also received detailed motor and non-motor evaluation by serial scales. Cognitive profiles were investigated in patients with PD-MCI, relative to patients with normal cognition (PD-NC) and cognitively NCs. In addition, differences in demography, major motor and non-motor symptoms were compared between patients with PD-MCI and PD-NC. There were 70 patients with PD-MCI, occupying 33.8% of the total patients. Patients with PD-MCI had impairment in multiple cognitive domains, especially in executive function, memory and visuospatial function on MoCA-BC, relative to cognitively NCs or PD-NC. Compared with PD-NC patients, PD-MCI patients were older (p = 0.002) and had a later onset age (p = 0.007) and higher score of the Unified Parkinson’s Disease Rating Scale (UPDRS) part III (p = 0.001). The positive rate of clinical possible rapid eye movement sleep behavior disorder (cpRBD) in the PD-MCI group was significantly increased relative to the PD-NC group (p = 0.003). Multivariate logistic analysis showed that older age (OR = 1.06; p = 0.012), higher score of UPDRS-III (OR = 1.03; p = 0.018) and the presence of cpRBD (OR = 2.10; p = 0.037) were independently associated factors of MCI in patients with PD. In conclusion, executive function, memory and visuospatial function are the main impaired cognitive profiles in PD-MCI via MoCA-BC. Aging, motor severity and RBD may be independently related factors of MCI in PD.

Time-course of decline in different cognitive domains in Parkinson's disease: a retrospective study

Cognitive impairment and dementia are common non-motor symptoms in Parkinson's disease (PD). To elucidate the potentially typical progression of cognitive decline in PD and its variation, we retrospectively surveyed neuropsychological data obtained at the Parkinson-Klinik Ortenau, Germany in the years 1996-2015. Many of the patients in the surveyed period were repeatedly admitted to our clinic and we were thus able to compile neuropsychological re-test data for 252 patients obtained at varying time intervals. Neuropsychological testing was conducted with the NAI (Nürnberger Alters-Inventar). This battery provides sub-tests that examine cognitive processing speed, executive function, working memory, and verbal/visual memory functions. The re-test time span varied across patients from below 1 year up to about 12 years. Most patients were seen twice, but some patients were tested up to eight times. The steepest rates of cognitive decline were observed for the NAI sub-tests Trail-Making, Maze Test, and Stroop-Word Reading/Color Naming. Intermediate rates of decline were found for Digit Span, Word List-Immediate Recall, and Picture Test. Stroop Test-Interference, Word List-Delayed Recognition, and Figure Test exhibited the slowest decline rates. We did not observe a significant effect of age at diagnosis or gender on the rate of decline. In sum, this study retrospectively evaluated cognitive decline in a sample of patients with PD. Our data suggest a broad cognitive decline that particularly affects the cognitive capacities for processing speed, executive functions, and immediate memory functions.

Identification of the Raman Salivary Fingerprint of Parkinson's Disease Through the Spectroscopic- Computational Combinatory Approach

Despite the wide range of proposed biomarkers for Parkinson's disease (PD), there are no specific molecules or signals able to early and uniquely identify the pathology onset, progression and stratification. Saliva is a complex biofluid, containing a wide range of biological molecules shared with blood and cerebrospinal fluid. By means of an optimized Raman spectroscopy procedure, the salivary Raman signature of PD can be characterized and used to create a classification model. Raman analysis was applied to collect the global signal from the saliva of 23 PD patients and related pathological and healthy controls. The acquired spectra were computed using machine and deep learning approaches. The Raman database was used to create a classification model able to discriminate each spectrum to the correct belonging group, with accuracy, specificity, and sensitivity of more than 97% for the single spectra attribution. Similarly, each patient was correctly assigned with discriminatory power of more than 90%. Moreover, the extracted data were significantly correlated with clinical data used nowadays for the PD diagnosis and monitoring. The preliminary data reported highlight the potentialities of the proposed methodology that, once validated in larger cohorts and with multi-centered studies, could represent an innovative minimally invasive and accurate procedure to determine the PD onset, progression and to monitor therapies and rehabilitation efficacy.

Cortical Serotonergic and Catecholaminergic Denervation in MPTP-Treated Parkinsonian Monkeys

Decreased cortical serotonergic and catecholaminergic innervation of the frontal cortex has been reported at early stages of Parkinson's disease (PD). However, the limited availability of animal models that exhibit these pathological features has hampered our understanding of the functional significance of these changes during the course of the disease. In the present study, we assessed longitudinal changes in cortical serotonin and catecholamine innervation in motor-symptomatic and asymptomatic monkeys chronically treated with low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Densitometry and unbiased stereological techniques were used to quantify changes in serotonin and tyrosine hydroxylase (TH) immunoreactivity in frontal cortices of 3 control monkeys and 3 groups of MPTP-treated monkeys (motor-asymptomatic [N = 2], mild parkinsonian [N = 3], and moderate parkinsonian [N = 3]). Our findings revealed a significant decrease (P < 0.001) in serotonin innervation of motor (Areas 4 and 6), dorsolateral prefrontal (Areas 9 and 46), and limbic (Areas 24 and 25) cortical areas in motor-asymptomatic MPTP-treated monkeys. Both groups of symptomatic MPTP-treated animals displayed further serotonin denervation in these cortical regions (P < 0.0001). A significant loss of serotonin-positive dorsal raphe neurons was found in the moderate parkinsonian group. On the other hand, the intensity of cortical TH immunostaining was not significantly affected in motor asymptomatic MPTP-treated monkeys, but underwent a significant reduction in the moderate symptomatic group (P < 0.05). Our results indicate that chronic intoxication with MPTP induces early pathology in the corticopetal serotonergic system, which may contribute to early non-motor symptoms in PD.

Characteristics of Parkinson's Disease in Patients with and without Cognitive Impairment

Background:

Characterizing patients with Parkinson’s disease (PD) and cognitive impairment is important toward understanding their natural history.

Objective:

Understand clinical, treatment, and cost characteristics of patients with PD pre- and post-cognitive impairment (memory loss/mild cognitive impairment/dementia or dementia treatment) recognition.

Methods:

2,711 patients with PD newly diagnosed with cognitive impairment (index) were identified using administrative claims data. They were matched (1:1) on age and gender to patients with PD and no cognitive impairment (controls). These two cohorts were compared on patient characteristics, healthcare resource utilization, and total median costs for 3 years pre- and post-index using Chi-square tests, t-tests, and Wilcoxon rank-sum tests. Logistic regression was used to identify factors predicting cognitive impairment.

Results:

Comorbidity indices for patients with cognitive impairment increased during the 6-year study period, especially after the index. Enrollment in Medicare Advantage Prescription Drug plans vs. commercial (OR = 1.60), dual Medicare/Medicaid eligibility (OR = 1.36), cerebrovascular disease (OR = 1.24), and PD medication use (OR = 1.46) were associated with a new cognitive impairment diagnosis (all p < 0.05). A greater proportion of patients with cognitive impairment had hospitalizations and emergency department visits and higher median total healthcare costs than controls for each year pre- and post-index.

Conclusion:

In patients with PD newly diagnosed with cognitive impairment, comorbidity burden, hospitalizations, emergency department visits, and total costs peaked 1-year pre- and post-identification. These data coupled with recommendations for annual screening for cognitive impairment in PD support the early diagnosis and management of cognitive impairment in order to optimize care for patients and their caregivers.

Deficits in or preservation of basic number processing in Parkinson's disease? A registered report

Neurodegenerative diseases such as Parkinson's disease (PD) have a huge impact on patients, caregivers, and the health-care system. To date, the diagnosis of mild cognitive impairments in PD has been established based on domain-general functions such as executive functions, attention, or working memory. However, specific numerical deficits observed in clinical practice have not yet been systematically investigated. PD-immanent deterioration of domain-general functions and domain-specific numerical areas suggests the mechanisms of both primary and secondary dyscalculia. The current study will systematically investigate basic number processing performance in PD patients for the first time, targeting domain-specific cognitive representations of numerosity and the influence of domain-general factors. The overall sample consists of patients with a diagnosis of PD, according to consensus guidelines, and healthy controls. PD patients will be stratified into patients with normal cognition or mild cognitive impairment (level I-PD-MCI based on cognitive screening). Basic number processing will be assessed using transcoding, number line estimation, and (non)symbolic number magnitude comparison tasks. Discriminant analysis will be employed to assess whether basic number processing tasks can differentiate between a healthy control group and both PD groups. All participants will be subjected to a comprehensive numerical and a neuropsychological test battery, as well as sociodemographic and clinical measures. Study results will give the first broad insight into the extent of basic numerical deficits in different PD patient groups and will help us to understand the underlying mechanisms of the numerical deficits faced by PD patients in daily life.

Neural signatures of predictive language processing in Parkinson's disease with and without mild cognitive impairment

Cognitive deficits are common in Parkinson's disease (PD), with some PD patients meeting criteria for mild cognitive impairment (MCI). An unaddressed question is whether linguistic prediction is preserved in PD. This ability is nowadays deemed crucial for achieving fast and efficient comprehension, and it may be negatively impacted by cognitive deterioration in PD. To fill this gap of knowledge, we used event-related potentials (ERPs) to evaluate mechanisms of linguistic prediction in a sample of PD patients (on dopamine compensation) with and without MCI. To this end, participants read sentence contexts that were predictive or not about a sentence-final word. The final word appeared after one sec, matching or mismatching the prediction. The introduction of the interval allowed to capture neural responses both before and after sentence-final words, reflecting semantic anticipation and semantic processing. PD patients with normal cognition (N = 58) showed ERP responses comparable to those of matched controls. Specifically, in predictive contexts, a slow negative potential developed prior to sentence-final words, reflecting semantic anticipation. Later, expected words elicited reduced N400 responses (compared to unexpected words), indicating facilitated semantic processing. PD patients with MCI (N = 20) showed, in addition, a prolongation of the N400 congruency effect (compared to matched PD patients without MCI), indicating that further cognitive decline impacts semantic processing. Finally, lower verbal fluency scores correlated with prolonged N400 congruency effects and with reduced pre-word differences in all PD patients (N = 78). This relevantly points to a role of deficits in temporal-dependent mechanisms in PD, besides prototypical frontal dysfunction, in altered semantic anticipation and semantic processing during sentence comprehension.

How Human Single-Neuron Recordings Can Help Us Understand Cognition: Insights from Memory Studies

Understanding human cognition is a key goal of contemporary neuroscience. Due to the complexity of the human brain, animal studies and noninvasive techniques, however valuable, are incapable of providing us with a full understanding of human cognition. In the light of existing cognitive theories, we describe findings obtained thanks to human single-neuron recordings, including the discovery of concept cells and novelty-dependent cells, or activity patterns behind working memory, such as persistent activity. We propose future directions for studies using human single-neuron recordings and we discuss possible opportunities of investigating pathological brain.

Cognitive impairment and its neuroimaging correlates in spinocerebellar ataxia 2

INTRODUCTION

Cognitive impairment (CI) is reported but is poorly explored in spinocerebellar ataxia 2 (SCA2). This study was undertaken to evaluate and classify cognitive impairment in patients with SCA2 and to identify their grey matter (GM) correlates.

METHODS

We evaluated the neurocognitive profile of 35 SCA2 and 30 age-, gender- and education-matched healthy controls using tests for attention, executive functions, learning and memory, language and fluency, and visuomotor constructive ability. Patients were classified into SCA2 with and without CI based on normative data from population and healthy controls. Furthermore, patients with CI were sub-classified based on the number of impaired domains into multi-domain CI (≥3 domains; MDCI) and limited domain CI (≤2 domains; LDCI). The underlying GM changes were identified using voxel based morphometry.

RESULTS

The mean age at onset, duration of disease, and ataxia score was 28.7 ± 8.51 years, 66.7 ± 44.1 months, and 16.1 ± 4.9 points, respectively. CI was present in 71.4% of SCA2 subjects (MDCI: 42.7%; LDCI: 28.5%). Patients with CI had significant atrophy of the posterior cerebellum, sensorimotor cortex, and superior frontal gyrus (FWE p-value <0.05). Patients with MDCI had significant GM atrophy of the angular gyrus compared to LDCI (FWE p-value <0.05).

CONCLUSION

Patients with CI had significant GM involvement of the posterior cerebellum and frontal lobe, suggestive of impairment in the cerebello-fronto-cortical circuitry.

Serum neurofilament light chain levels reflect cortical neurodegeneration in de novo Parkinson's disease

INTRODUCTION

Cognitive impairment and dementia are highly prevalent non-motor complications in Parkinson's disease (PD) with deleterious consequences for patients and caregivers. With no treatment currently available, finding and validating minimally-invasive biomarkers of neurodegeneration in this population represents an urgent need for clinical trials targeting its prevention or delay. Recently, serum neurofilament light chain (NfL) levels have been identified as a promising biomarker of neural loss, but whether they reflect cortical neurodegeneration in early PD stages has not been addressed.

METHODS

From the Parkinson's Progression Markers Initiative (PPMI), we selected 133 de novo PD patients and 56 healthy controls (HC) with available structural neuroimaging and serum NfL data. We then studied whether NfL levels were abnormal in the PD group with respect to HC, and whether they correlated with cognitive indicators and cortical macro (cortical thinning) and microstructural (increased intracortical mean diffusivity) degeneration.

RESULTS

Serum NfL levels were significantly increased in the PD group (p = 0.010), and were also related to worse cognitive performance and a cortical macro and microstructural compromise (p < 0.05 corrected). These associations were observed both cross-sectionally and longitudinally within a one-year follow-up period. Topographically, NfL levels reflected posterior-cortical deterioration rather than frontal damage. Importantly, NfL levels were not associated with striatal SPECT-DAT uptake or β-amyloid burden.

DISCUSSION

Our results show that serum NfL levels reflect cortical neurodegeneration from the very early stages of PD. Moreover, its brain structural correlates and its lack of relationship with dopaminergic depletion or amyloidosis suggests that NfL could track the underlying pathological process leading to PD dementia.

Relationship between serum homocysteine level and cognitive impairment in patients with Parkinson‘s disease

OBJECTIVE To investigate the correlation between serum homocysteine (Hcy) and cognitive impairment (CI) in patients with Parkinson’s disease (PD).

METHODS Eighty-one PD patients were prospectively recruited in this study from Feb 2015 to Jan 2018 in Gansu Provincial Hospital. Of the subjects, 41 were diagnosed with cognitive impairment (PD-CI) vs. the 40 others without PD (PDN). The clinical characteristic and demographic features were recorded for the two groups. The serum Hcy, folate and vitamin B12 (VitB12) were examined by high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA).

RESULTS The serum Hcy, folate, VitB12 concentration were 21.7±6.2 (μmol/L), 9.2±3.7 (ng/mL), 354.1±123.5 (pg/mL) for PD-CI group and 14.1±5.7 (μmol/L), 12.4±4.5 (ng/mL), 378.7±128.2 (pg/mL) for PDN group respectively. The serum level of Hcy in PD-CI group was significantly higher than that of PDN group (p<0.05), serum folate was significantly lower than PDN group (p<0.05). The diagnostic sensitivity, specificity and AUC were 77.5% (95%CI:61.6%-89.2%), 78.1% (95%CI:62.4%-89.4%), 0.82 (95%CI:0.73-0.91) for serum Hcy and 72.5% (95%CI:56.1%-85.4%), 63.4% (95%CI:46.9%-77.9%), 0.71(95%CI:0060-0.83) for serum folate respectively as serological markers for cognitive impairment diagnosis in patients with PD.

Conclusion Serum Hcy and folate were different between PD-CI and PDN patients, which may play an important role in cognitive impairment development in patients with PD and can be used as promising serological diagnostic marker.

Early detection of cognitive impairment in Parkinson's disease with the use of the Wisconsin Card Sorting Test: correlations with Montreal Cognitive Assessment and smell identification test

Cognitive function is often impaired in early Parkinson's disease (PD). The Wisconsin Card Sorting Test (WCST) is a neuropsychological test of "set-shifting" ability. To see whether WCST is useful for detecting early changes of cognitive function in PD, we examined the correlations of WCST with the Montreal Cognitive Assessment (MoCA) and the Odor Stick Identification Test (OSIT). Subjects were 48 PD patients (age 66 ± 10 years; Hoehn & Yahr stage 2.3 ± 0.8; mean duration 3.1 ± 2.5 years). WCST sub-scores for categories achieved (CA), perseverative errors of Nelson type (PEN), and difficulties of maintaining set (DMS) were evaluated. MoCA-J (Japanese version) and OSIT-J (Japanese version) were done in that order, followed by the WCST. In PD patients, CA was 2.2 ± 2.0, PEN was 7.0 ± 6.4, and DMS was 2.3 ± 2.0, and all were worse than those of age-matched normal subjects. MoCA-J scores significantly correlated with PEN. OSIT-J scores were also significantly correlated with CA and DMS. As MoCA-J and OSIT-J show high sensitivity and specificity for detecting mild cognitive impairment in PD, WCST may also be a useful supplementary diagnostic tool for early and mild cognitive impairment in PD patients.