Detecting modular brain states in rest and task

The human brain is a dynamic networked system that continually reconfigures its functional connectivity patterns over time. Thus, developing approaches able to adequately detect fast brain dynamics is critical. Of particular interest are the methods that analyze the modular structure of brain networks, that is, the presence of clusters of regions that are densely interconnected. In this paper, we propose a novel framework to identify fast modular states that dynamically fluctuate over time during rest and task. We started by demonstrating the feasibility and relevance of this framework using simulated data. Compared with other methods, our algorithm was able to identify the simulated networks with high temporal and spatial accuracies. We further applied the proposed framework on MEG data recorded during a finger movement task, identifying modular states linking somatosensory and primary motor regions. The algorithm was also performed on dense-EEG data recorded during a picture naming task, revealing the subsecond transition between several modular states that relate to visual processing, semantic processing, and language. Next, we tested our method on a dataset of resting-state dense-EEG signals recorded from 124 patients with Parkinson's disease. Results disclosed brain modular states that differentiate cognitively intact patients, patients with moderate cognitive deficits, and patients with severe cognitive deficits. Our new approach complements classical methods, offering a new way to track the brain modular states, in healthy subjects and patients, on an adequate task-specific timescale.

Electroencephalography-based machine learning for cognitive profiling in Parkinson's disease: Preliminary results

BACKGROUND

Cognitive symptoms are common in patients with Parkinson's disease. Characterization of a patient's cognitive profile is an essential step toward the identification of predictors of cognitive worsening.

OBJECTIVE

The aim of this study was to investigate the use of the combination of resting-state EEG and data-mining techniques to build characterization models.

METHODS

Dense EEG data from 118 patients with Parkinson's disease, classified into 5 different groups according to the severity of their cognitive impairments, were considered. Spectral power analysis within 7 frequency bands was performed on the EEG signals. The obtained quantitative EEG features of 100 patients were mined using 2 machine-learning algorithms to build and train characterization models, namely, support vector machines and k-nearest neighbors models. The models were then blindly tested on data from 18 patients.

RESULTS

The overall classification accuracies were 84% and 88% for the support vector machines and k-nearest algorithms, respectively. The worst classifications were observed for patients from groups with small sample sizes, corresponding to patients with the severe cognitive deficits. Whereas for the remaining groups for whom an accurate diagnosis was required to plan the future healthcare, the classification was very accurate.

CONCLUSION

These results suggest that EEG features computed from a daily clinical practice exploration modality in-that it is nonexpensive, available anywhere, and requires minimal cooperation from the patient-can be used as a screening method to identify the severity of cognitive impairment in patients with Parkinson's disease. © 2018 International Parkinson and Movement Disorder Society.

Dyspnea: An underestimated symptom in Parkinson's disease

INTRODUCTION

Dyspnea is one of the least well-characterized non-motor symptoms (NMS) associated with Parkinson's disease (PD).

OBJECTIVE

To determine the frequency of dyspnea in a large, single-center cohort of consecutive PD patients with no history of lung or heart disease, and to compare clinical features in dyspneic vs. non-dyspneic patients.

METHODS

Patients with abnormal cardiovascular and pulmonary results in a clinical examination were excluded. A positive response to at least one question ("In the last month, have you suffered from breathlessness?" and "In the last month, have you had trouble breathing normally?") was considered to signify the experience of dyspnea. MDS-UPDRS, global cognitive performance, non-motor symptoms and quality of life were assessed.

RESULTS

In the cohort of 153 non-demented PD patients (mean age ± standard deviation: 63.9 ± 7.4; mean disease duration: 9.2 ± 6.1 years), the mean [95% confidence interval (CI)] frequency of dyspnea was 39.2% (31.5-47). After adjustment for disease severity, PD patients with dyspnea had a significantly higher Movement Disorders Society Unified Parkinson's Disease Rating Scale part I, II and IV scores, a higher HAD anxiety and depression scores and a significantly higher 8-item Parkinson's Disease Questionnaire.

CONCLUSION

Dyspnea is a frequent NMS in PD. Its pathophysiology and prognostic value need more investigation.

Cognitive behavioural therapy for anxiety disorders in Parkinson's disease: Design of a randomised controlled trial to assess clinical effectiveness and changes in cerebral connectivity

BACKGROUND

Anxiety disorders occur in up to 35% of patients with Parkinson's disease (PD) and have a negative effect on motor symptoms and quality of life. To date, no clinical trials specifically targeting anxiety in PD patients have been published.

OBJECTIVE

To describe the rationale and methodology of a randomised controlled trial (RCT) that aims to study the clinical effectiveness, alterations in brain circuitry, and cost-effectiveness of cognitive behavioural therapy (CBT) for anxiety in PD.

METHODS

This study is a prospective, two-centre RCT in which sixty PD patients with anxiety will be randomised to CBT treatment and clinical monitoring (intervention group) or to clinical monitoring only (control group). The CBT module used in this study was specifically developed to address symptoms of anxiety in PD patients. Participants will undergo standardised clinical, cognitive and behavioural assessment at baseline and at 2 follow-up measurements, as well as resting-state fMRI and DTI scanning before and after the intervention. The primary outcome measure is changes in severity of anxiety symptoms. Secondary outcome measures involve long-term changes in anxiety symptoms, changes in functional and structural connectivity between limbic and frontal cortices, and cost-effectiveness of the treatment. The study is registered at the ClinicalTrials.gov database under registration number NCT02648737.

CONCLUSION

This study is the first that evaluates both the clinical effectiveness, cost-effectiveness, as well as the biological impact of CBT for anxiety in PD patients that, if proven effective, will hopefully contribute to a better and evidence-based approach for these non-motor symptoms.

Ventilatory Dysfunction in Parkinson's Disease

In contrast to some other neurodegenerative diseases, little is known about ventilatory dysfunction in Parkinson’s disease (PD). To assess the spectrum of ventilation disorders in PD, we searched for and reviewed studies of dyspnea, lung volumes, respiratory muscle function, sleep breathing disorders and the response to hypoxemia in PD. Among the studies, we identified some limitations: (i) small study populations (mainly composed of patients with advanced PD), (ii) the absence of long-term follow-up and (iii) the absence of functional evaluations under “off-drug” conditions. Although there are many reports of abnormal spirometry data in PD (mainly related to impairment of the inspiratory muscles), little is known about hypoventilation in PD. We conclude that ventilatory dysfunction in PD has been poorly studied and little is known about its frequency and clinical relevance. Hence, there is a need to characterize the different phenotypes of ventilation disorders in PD, study their relationships with disease progression and assess their prognostic value.

Expanding the phenotype of SCA19/22: Parkinsonism, cognitive impairment and epilepsy

INTRODUCTION

Spinocerebellar ataxia types 19 and 22 (SCA19/22) are rare conditions in which relatively isolated cerebellar involvement is frequently associated with cognitive impairment. Here, we report on new clinical features and provide details of the cognitive profile in two SCA19/22 families.

METHODS

Two families displaying an autosomal-dominant form of cerebellar ataxia underwent clinical examinations and genetic testing.

RESULTS

In addition to the classical clinical features of SCA, a wide spectrum of cognitive disorders (including visuospatial impairments) was observed. Eight patients had mild Parkinsonism, and five had epilepsy. Genetic testing showed that the KCND3 mutation (c.679_681delTTC, p.F227del) was present in both families.

CONCLUSIONS

Our findings broaden the phenotypic spectrum of SCA19/22, and suggest that KCND3 should be included in the list of candidate genes for epilepsy, Parkinsonism and cognitive impairment.

Neurobiological correlates of emotional processing in Parkinson's disease: A systematic review of experimental studies

Deficits in emotional processing in patients with Parkinson's disease (PD) have received increasing interest over the past decades. In this systematic review, we present the results of 18 behavioral studies that have examined the neurobiological base of emotional processing in PD. Multiple aspects of emotional processing have been studied, using a variety of research methods. Deficits in PD are mainly related to autonomic and perceptive processing of intense emotional stimuli, which is accompanied by structural and functional neurobiological abnormalities in predominantly ventral regions of affective neurocircuitry. These structures are more strongly dependent on dopaminergic neurotransmission than the dorsal structures of affective neurocircuitry, which are more related to the cognitive and regulatory aspects of emotion and appear to remain largely intact in PD patients. Considering the importance of active dopaminergic neurotransmission, PD can serve as a prolific model for studying the neurobiological correlates of normal human emotional behavior as well as psychiatric disorders such as anxiety, depression, and apathy. Moreover, the fact that PD patients are able to cognitively regulate or modulate their emotional responses despite reduced dopamine supplies, can have important implications for the treatment of affective disorders not only in PD patients but in the general population likewise.

Functional connectivity disruptions correlate with cognitive phenotypes in Parkinson's disease

Cognitive deficits in Parkinson's disease are thought to be related to altered functional brain connectivity. To date, cognitive-related changes in Parkinson's disease have never been explored with dense-EEG with the aim of establishing a relationship between the degree of cognitive impairment, on the one hand, and alterations in the functional connectivity of brain networks, on the other hand.

This study was aimed at identifying altered brain networks associated with cognitive phenotypes in Parkinson's disease using dense-EEG data recorded during rest with eyes closed. Three groups of Parkinson's disease patients (N = 124) with different cognitive phenotypes coming from a data-driven cluster analysis, were studied: G1) cognitively intact patients (63), G2) patients with mild cognitive deficits (46) and G3) patients with severe cognitive deficits (15). Functional brain networks were identified using a dense-EEG source connectivity method. Pairwise functional connectivity was computed for 68 brain regions in different EEG frequency bands. Network statistics were assessed at both global (network topology) and local (inter-regional connections) level.

Results revealed progressive disruptions in functional connectivity between the three patient groups, typically in the alpha band. Differences between G1 and G2 (p < 0.001, corrected using permutation test) were mainly frontotemporal alterations. A statistically significant correlation (ρ = 0.49, p < 0.001) was also obtained between a proposed network-based index and the patients' cognitive score. Global properties of network topology in patients were relatively intact.

These findings indicate that functional connectivity decreases with the worsening of cognitive performance and loss of frontotemporal connectivity may be a promising neuromarker of cognitive impairment in Parkinson's disease.

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We test the use of dense-EEG to identify altered brain networks associated with cognitive phenotypes in Parkinson's disease.

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The functional connectivity decreases with the worsening of cognitive performance

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The loss of frontotemporal connectivity may be a promising neuromarker of cognitive impairment in Parkinson's disease.

Impact of Mood and Behavioral Disorders on Quality of Life in Parkinson's disease

BACKGROUND

Mood symptoms negatively affect quality of life of Parkinson's disease (PD); however little is known about the impact of behavioral disorders such as impulse control disorders, and non-motor fluctuations on quality of life.

OBJECTIVE

To assess the impact of mood and behavioral disorders on quality of life in PD.

METHODS

136 (84% male) PD were included (mean age: 61 ± 8y; mean duration of disease: 8.8 ± 5.4y). Mood symptoms, behavioral disorders and non-motor fluctuations were detected and quantified using the recently validated "Ardouin Scale of Behavior in Parkinson's Disease". Motor symptoms were assessed using UPDRS and quality of life with the "39-item Parkinson's Disease Questionnaire".

RESULTS

Both motor and non-motor factors significantly affected the quality of life of PD patients. Multivariate regression of the relationship between items of the quality of life questionnaire and the Ardouin Scale showed that alteration of patients' quality of life was strongly correlated with the presence of mood symptoms (such as depression, anxiety ...) and with non-motor fluctuations (especially in the OFF period). A significant correlation was also found between the number of symptoms and their severity, and the quality of life deterioration. Some behavioral disorders (compulsive buying / eating behavior) also negatively affected patient's quality of life to a lesser extent. Alternatively, excess in motivation and hobbyism behaviors had a positive impact on mobility and emotional well-being dimensions respectively of quality of life.

CONCLUSIONS

This study shows the main impact of mood symptoms and non-motor fluctuations on worsening quality of life in PD.

Cognitive phenotypes in parkinson's disease differ in terms of brain-network organization and connectivity

Cognitive deficits are common in Parkinson's disease and we suspect that dysfunctions of connected brain regions can be the source of these deficits. The aim of the present study was to investigate changes in whole-brain intrinsic functional connectivity according to differences in cognitive profiles in Parkinson's disease. 119 participants were enrolled and divided into four groups according to their cognitive phenotypes (determined by a cluster analysis): (i) 31 cognitively intact patients (G1), (ii) 31 patients with only slight mental slowing (G2), (iii) 43 patients with mild to moderate deficits mainly in executive functions (G3), (iv) 14 patients with severe deficits in all cognitive domains (G4-5). Rs-fMRI whole-brain connectivity was examined by two complementary approaches: graph theory for studying network functional organization and network-based statistics (NBS) for exploring functional connectivity amongst brain regions. After adjustment for age, duration of formal education and center of acquisition, there were significant group differences for all functional organization indexes: functional organization decreased (G1 > G2 > G3 > G4-5) as cognitive impairment worsened. Between-group differences in functional connectivity (NBS corrected, P < 0.01) mainly concerned the ventral prefrontal, parietal, temporal and occipital cortices as well as the basal ganglia. In Parkinson's disease, brain network organization is progressively disrupted as cognitive impairment worsens, with an increasing number of altered connections between brain regions. We observed reduced connectivity in highly associative areas, even in patients with only slight mental slowing. The association of slowed mental processing with loss of connectivity between highly associative areas could be an early marker of cognitive impairment in Parkinson's disease and may contribute to the detection of prodromal forms of Parkinson's disease dementia. Hum Brain Mapp 38:1604-1621, 2017. © 2016 Wiley Periodicals, Inc.

Hallucinations and conscious access to visual inputs in Parkinson's disease

The pathophysiology of visual hallucinations in Parkinson’s disease has yet to be characterized. Although stimulus-driven (“bottom-up”) processes are known to be impaired, the role of “top-down” processes remains to be determined. Distinguishing between conscious and non-conscious detections (i.e. access to consciousness) may be a valuable way of monitoring top-down processes. Conscious access to visual inputs was investigated to identify the neural substrates underlying susceptibility to hallucinations in Parkinson’s disease. Seventeen healthy controls, 18 Parkinson’s disease patients with minor visual hallucinations and 16 without were enrolled in the study. During functional magnetic resonance imaging, the participants performed a visual detection task. The detection threshold was significantly higher in each patient group than in healthy controls while the two groups of patients did not differ significantly. Compared with hallucination-free patients, patients with minor hallucinations displayed hyperactivation of prefrontal and right occipital cortices, and hypoactivation of the left cingulate, temporal and occipital cortices. During conscious access to visual inputs, the functional network in patients with visual hallucinations differed from that seen in patients without visual hallucinations. This suggests that the supremacy of top-down processes in visual information processing may enhance susceptibility to hallucinations in Parkinson’s disease.

Are Upper-Body Axial Symptoms a Feature of Early Parkinson's Disease?

BACKGROUND

Axial disorders are considered to appear late in the course of Parkinson's disease (PD). The associated impact on quality of life (QoL) and survival and the lack of an effective treatment mean that understanding and treating axial disorders is a key challenge. However, upper-body axial disorders (namely dysarthria, swallowing and breathing disorders) have never been prospectively assessed in early-stage PD patients.

OBJECTIVES

To characterize upper-body axial symptoms and QoL in consecutive patients with early-stage PD.

METHODS

We prospectively enrolled 66 consecutive patients with early-stage PD (less than 3 years of disease progression) and assessed dysarthria, dysphagia and respiratory function (relative to 36 controls) using both objective and patient-reported outcomes.

RESULTS

The mean disease duration was 1.26 years and the mean UPDRS motor score was 19.4 out of 108. 74% of the patients presented slight dysarthria (primarily dysprosodia). Men appeared to be more severely affected (i.e. dysphonia). This dysfunction was strongly correlated with low swallowing speed (despite the absence of complaints about dysphagia), respiratory insufficiency and poor QoL. Videofluorography showed that oral-phase swallowing disorders affected 60% of the 31 tested patients and that pharyngeal-phase disorders affected 21%. 24% of the patients reported occasional dyspnea, which was correlated with anxiety in women but not in men. Marked diaphragmatic dysfunction was suspected in 42% of the patients (predominantly in men).

CONCLUSION

Upper body axial symptoms were frequent in men with early-stage PD, whereas women presented worst non-motor impairments. New assessment methods are required because currently available tools do not reliably detect these upper-body axial disorders.

Freezing/festination during motor tasks in early-stage Parkinson's disease: A prospective study

BACKGROUND

Parkinsonian patients have a tendency to speed up during repetitive motor tasks (festination) and to experience sudden motor blocks (freezing). In this article, we prospectively studied the appearance and progression of these phenomena in 30 early-stage PD patients.

METHODS

A total of 30 controls and early-stage PD patients were assessed in the "off-drug" condition at baseline and 2 years later. Freezing of gait was evaluated using a standardized gait trajectory with the usual triggers. Patients also performed diadochokinetic tasks with 3 different effectors (repetitive, antiphase movements for the hands and feet, and repetitive syllable production for the orofacial effector) at frequencies ranging from 1 to 7 Hz (in random order). The primary endpoint was the occurrence of freezing and festination.

RESULTS

At baseline, freezing was observed in 6.5% of the trials in PD patients (43% of the patients) and 2.3% of the trials in controls, and festination was observed in 5.7% of the trials in patients (53% of the patients) and 0.8% of the trials in controls. These proportions were slightly higher in patients 2 years later. None of the patients presented freezing of gait at baseline, but 2 displayed this condition 2 years later. These phenomena occurred more frequently for the limb effectors than for the orofacial effector. Freezing and festination were associated with the akinetic-rigid subtype, although tremor-dominant patients displayed greater rhythm variability outside episodes.

CONCLUSION

Freezing and festination of the upper and lower limbs are observed soon after the diagnosis of PD and may be early biomarkers for disease progression. © 2016 International Parkinson and Movement Disorder Society.

Effects of Stimulus-Driven and Goal-Directed Attention on Prepulse Inhibition of Brain Oscillations

OBJECTIVE

Prepulse inhibition (PPI) is an operational measure of sensory gating. PPI of cortical response to a startling pulse is known to be modulated by attention. With a time-frequency analysis, we sought to determine whether goal-directed and stimulus-driven attention differentially modulate inhibition of cortical oscillations elicited by a startling pulse.

METHODS

An electroencephalogram (EEG) was recorded in 26 healthy controls performing an active acoustic PPI paradigm. Startling stimuli were presented alone or either 400 or 1000 ms after one of three types of visual prepulse: to-be-attended (goal-directed attention), unexpected (stimulus-driven attention) or to-be-ignored (non-focused attention). We calculated the percentage PPI for the auditory event-related spectral perturbation (ERSP) of theta (4-7 Hz), alpha (8-12 Hz), beta1 (13-20 Hz) and beta2 (20-30 Hz) oscillations and changes in inter-trial coherence (ITC), a measure of phase synchronization of electroencephalographic activity.

RESULTS

At 400 ms: (i) PPI of the ERSP of alpha, theta and beta1 oscillation was greater after an unexpected and a to-be-attended prepulse than after a to-be-ignored prepulse; and (ii) PPI of beta2 oscillations was greater after a to-be-attended than a to-be-ignored prepulse. At 1000 ms: (i) PPI of alpha oscillations was greater after an unexpected and a to-be-attended prepulse than after a to-be-ignored prepulse; and (ii) PPI of beta1 oscillations was greater after a to-be-attended than a to-be-ignored prepulse. The ITC values did not vary according to the type of prepulse.

CONCLUSIONS

In an active PPI paradigm, stimulus-driven and goal-directed attention each have differential effects on the modulation of cortical oscillations.

Hypometabolism in Posterior and Temporal Areas of the Brain is Associated with Cognitive Decline in Parkinson's Disease

BACKGROUND

Brain metabolic profiles of patients with Parkinson's disease (PD) and cognitive impairment or dementia are now available. It would be useful if data on brain metabolism were also predictive of the risk of a pejorative cognitive evolution - especially in the multidisciplinary management of advanced PD patients.

OBJECTIVE

The primary objective was to determine whether a specific brain metabolic pattern is associated with cognitive decline in PD.

METHODS

Sixteen advanced PD patients were screened for the absence of cognitive impairment (according to the Mattis dementia rating scale, MDRS) and underwent [18F]-fluorodeoxyglucose positron emission tomography brain imaging in the "off drug" state. The MDRS was scored again about two years later, categorizing patients as having significant cognitive decline (decliners) or not (stables). The two groups were then compared in terms of their brain metabolism at inclusion.

RESULTS

There were six decliners and ten stables. Significant hypometabolism in the two precunei (Brodmann area (BA) 31), the left middle temporal gyrus (BA21) and the left fusiform gyrus (BA37) was found in the decliner group compared withthe stables.

CONCLUSION

In advanced PD, a particular metabolic pattern may be associated with the onset of significant cognitive decline.

Specific Attentional Disorders and Freezing of Gait in Parkinson's Disease

BACKGROUND

Due to its high prevalence in dual-task paradigms, freezing of gait in Parkinson's disease is thought to be associated with dysexecutive syndrome and attentional disorders. However, the role of specific attentional disorders in patients with freezing of gait is still unclear.

OBJECTIVE

Here, we sought to specifically determine which basic attentional modalities are impaired in patients with freezing of gait.

METHODS

Seventy-eight parkinsonian patients performed a computer-controlled reaction-time paradigm designed to measure the different attentional subcomponents, controlled for visuospatial processing and motor participation.

RESULTS

The freezer (n = 42) and non-freezer (n = 36) groups were matched for age, educational level, MMSE and Mattis Dementia Rating Scale. There were no intergroup differences in simple reaction times, whereas choice reaction times were higher in the freezer group than in the non-freezer group for divided attention (p = 0.023).

CONCLUSIONS

At equivalent levels of overall cognitive efficiency, freezer patients showed a greater slowdown than non-freezer patients with a specific impairment in divided attention.

French consensus procedure for assessing cognitive function in Parkinson's disease

INTRODUCTION

One of the objectives of the French expert centers for Parkinson's disease (NS-Park) network was to determine a consensus procedure for assessing cognitive function in patients with Parkinson's. This article presents this procedure and briefly describes the selected tests.

METHODS

A group of 13 experts used the Delphi method for consensus building to define the overall structure and components of the assessment procedure. For inclusion in the battery, tests had to be validated in the French language, require little motor participation, have normative data and be recognized by the international community. Experimental tasks and tests requiring specific devices were excluded.

RESULTS

Two possibilities were identified, depending on whether an abbreviated or comprehensive assessment of cognitive function was necessary. For an abbreviated assessment, the experts recommended the Montreal Cognitive Assessment (MoCA) as a screening test for cognitive impairment or dementia. For a comprehensive neuropsychological assessment, the experts recommended assessing global efficiency plus the five main cognitive domains (attention and working memory, executive function, episodic memory, visuospatial function and language) that may be impaired in Parkinson's disease, using two tests for each domain.

DISCUSSION AND CONCLUSION

A common procedure for assessing cognitive function is now available across the French network dedicated to Parkinson's disease, and is recommended for both research and clinical practice. It will also help to promote standardization of the neuropsychological assessment of Parkinson's disease.

A 15-day course of donepezil modulates spectral EEG dynamics related to target auditory stimuli in young, healthy adult volunteers

OBJECTIVE

To identify possible electroencephalographic (EEG) markers of donepezil's effect on cortical activity in young, healthy adult volunteers at the group level.

METHODS

Thirty subjects were administered a daily dose of either 5mg donepezil or placebo for 15days in a double-blind, randomized, cross-over trial. The electroencephalogram during an auditory oddball paradigm was recorded from 58 scalp electrodes. Current source density (CSD) transformations were applied to EEG epochs. The event-related potential (ERP), inter-trial coherence (ITC: the phase consistency of the EEG spectrum) and event-related spectral perturbation (ERSP: the EEG power spectrum relative to the baseline) were calculated for the target (oddball) stimuli.

RESULTS

The donepezil and placebo conditions differed in terms of the changes in delta/theta/alpha/beta ITC and ERSP in various regions of the scalp (especially the frontal electrodes) but not in terms of latency and amplitude of the P300-ERP component.

CONCLUSION

Our results suggest that ITC and ERSP analyses can provide EEG markers of donepezil's effects in young, healthy, adult volunteers at a group level.

SIGNIFICANCE

Novel EEG markers could be useful to assess the therapeutic potential of drug candidates in Alzheimer's disease in healthy volunteers prior to the initiation of Phase II/III clinical studies in patients.

L’apathie : définitions, diagnostic, épidémiologie et retentissement

L’apathie est un trouble invalidant, présent dans de nombreuses pathologies neurologiques et psychiatriques. Il s’agit d’un trouble de la motivation caractérisé par des manifestations comportementales, cognitives et émotionnelles telles qu’une perte d’intérêt et une moindre participation aux activités de la vie quotidienne, un manque d’initiative, peu de persévérance dans les activités entamées, une indifférence et un émoussement affectif. Il ne s’agit pas uniquement d’un symptôme de la dépression ou d’un signe d’entrée dans la démence mais l’apathie existe en tant que syndrome à part entière. Elle a été longtemps sous-diagnostiquée en raison d’une absence de consensus au sujet de sa définition. Néanmoins, des critères de diagnostic ont récemment été publiés et leur validité a été éprouvée et démontrée dans plusieurs maladies neuropsychiatriques . De plus, un certain nombre d’échelles sont aujourd’hui reconnues pour leur validité dans le dépistage ou l’évaluation du syndrome apathique . D’un point de vue physiopathologique, les mécanismes à l’origine du syndrome apathique restent encore à élucider mais il est généralement admis que les comportements motivés mettent en œuvre le système limbique. Le circuit striato-frontal ventral (reliant le striatum ventral aux régions ventro-médianes du cortex préfrontal) semble particulièrement impliqué. Le rôle des voies dopaminergiques est également démontré même si d’autres neuro-modulateurs semblent également impliqués. L’apathie accroît fortement le fardeau des aidants et compte tenu de son impact sur le niveau fonctionnel et la qualité de vie des patients, elle mérite une attention particulière, notamment un dépistage systématique et une prise en charge précoce.

Cognitive disorders in Parkinson's disease: Confirmation of a spectrum of severity

INTRODUCTION

Clinical presentation and progression of cognitive disorders in Parkinson's disease (PD) is heterogeneous. Our objective was to confirm prospectively a previous exploratory cluster analysis based on retrospective data that identified five cognitive phenotypes in PD.

METHODS

A model-based confirmatory cluster analysis was conducted on the results of neuropsychological tests administered in 156 PD patients from two European movement disorder centers (Lille, n = 81; Maastricht, n = 75). The number of clusters was determined on the basis of statistical criteria as well as clinical plausibility. A factorial discriminant analysis assessed the quality of the clusters' separation.

RESULTS

A five-cluster model was statistically superior and clinically the most relevant. These clusters can be described as follows: 1) cognitively intact patients with high level of performance in all cognitive domains (25.64%), 2) cognitively intact patients slightly slower than those in cluster 1 (26.92%), 3) patients with deficits in executive functions (37.18%), 4) patients with severe deficits in all cognitive domains, particularly executive functions (3.20%), 5) patients with severe deficits in all cognitive domains, particularly working memory and recall in verbal episodic memory (7.05%). The groups differed in terms of age, apathy and frequency of hallucinations that were all higher in the clusters with cognitive deficits, and the duration of formal education was lower in those groups.

CONCLUSION

We confirm our previous exploratory analysis. Cognitive disorders in PD patients are heterogeneous and can be separated in five clusters ranging from patients with performance in the normal range to patients with severe disorders in all cognitive domains.

Diagnosing dementia in multiple system atrophy by applying Movement Disorder Society diagnostic criteria for Parkinson's disease dementia

INTRODUCTION

Dementia is an exclusion criterion in current consensus diagnostic criteria, while growing evidence suggests the occurrence of cognitive dysfunction and even dementia in multiple system atrophy (MSA) patients. The main goal of this study was to determine if Movement Disorder Society (MDS) Parkinson's disease dementia (PDD) LEVEL-1 criteria are useful in screening for dementia in MSA patients compared to full cognitive testing (LEVEL-2 criteria).

METHODS

In this retrospective study, MDS diagnostic criteria for PDD were applied in 111 MSA patients from three centres. LEVEL-1 evaluation (short screening test) was compared to LEVEL-2 examination (extensive neuropsychological gold standard assessment). Sensitivity, specificity, positive and negative predictive values were calculated for LEVEL-1 compared to LEVEL-2. Two Mini Mental State Examination (MMSE) cut-off scores were evaluated (<26 according to MDS procedures for the diagnosis of PDD and <27 which has proven more sensitive in a recent study proposing a short procedure for PDD screening).

RESULTS

According to these criteria, 11.7% of MSA patients were demented on LEVEL-2 examination. LEVEL-1 examination showed strong specificity (96.9%) and negative predictive value (94.1%), while sensitivity (53.8%) and positive predictive (70%) value were moderate compared to LEVEL-2 evaluation. Sensitivity increased to 84.6% when using a MMSE threshold <27 for LEVEL-1. Executive dysfunction was the main prevalent finding (52% of all patients), while impairment of memory (15%), language (14%) and visuospatial functions was less frequent (13%).

CONCLUSION

Our findings suggest that the MDS PDD short screening test may be useful for the diagnosis of MSA dementia.

Impaired Early Attentional Processes in Parkinson's Disease: A High-Resolution Event-Related Potentials Study

Introduction

The selection of task-relevant information requires both the focalization of attention on the task and resistance to interference from irrelevant stimuli. A previous study using the P3 component of the event-related potentials suggested that a reduced ability to resist interference could be responsible for attention disorders at early stages of Parkinson’s disease (PD), with a possible role of the dorsolateral prefrontal cortex (DLPFC).

Methods

Our objective was to better determine the origin of this impairment, by studying an earlier ERP component, the N2, and its subcomponents, as they reflect early inhibition processes and as they are known to have sources in the anterior cingulate cortex (ACC), which is involved together with the DLPFC in inhibition processes. Fifteen early-stage PD patients and 15 healthy controls (HCs) performed a three-stimulus visual oddball paradigm, consisting in detecting target inputs amongst standard stimuli, while resisting interference from distracter ones. A 128-channel electroencephalogram was recorded during this task and the generators of the N2 subcomponents were identified using standardized weighted low-resolution electromagnetic tomography (swLORETA).

Results

PD patients displayed fewer N2 generators than HCs in both the DLPFC and the ACC, for all types of stimuli. In contrast to controls, PD patients did not show any differences between their generators for different N2 subcomponents.

Conclusion

Our data suggest that impaired inhibition in PD results from dysfunction of the DLPFC and the ACC during the early stages of attentional processes.

Impaired corticostriatal connectivity in impulse control disorders in Parkinson disease

OBJECTIVES

To compare the striatum's resting-state functional connectivity in patients with Parkinson disease (PD) with and without impulse control disorders (ICDs).

METHODS

Twenty patients with PD and ICDs, 19 patients with PD but no ICDs, and 19 healthy controls underwent fMRI in the resting state. The ventral striatum, dorsal caudate, and anterior and posterior putamen were segmented semiautomatically. For each region of interest, a seed-based connectivity analysis was performed on preprocessed fMRI data mapped on the ipsilateral cortical surface. An additional cortical thickness analysis was used to assess and compare gray matter atrophy in the 3 study subgroups.

RESULTS

The presence of an ICD in patients with PD was associated with functional disconnection between the left anterior putamen and both the left inferior temporal gyrus and the left anterior cingulate gyrus, as well as a trend toward a functional disconnection between several motor and associative striatal regions and limbic, associative, and motor cortical regions. Patients without ICDs did not differ from healthy controls in corticostriatal connectivity. The cortical thickness analysis did not reveal any significant differences among the 3 study subgroups.

CONCLUSIONS

In PD, ICDs are associated with altered connectivity between an associative striatal area (the left anterior putamen) and associative and limbic cortical regions (the left inferior temporal gyrus and the left anterior cingulate gyrus).

Polymorphism of the dopamine transporter type 1 gene modifies the treatment response in Parkinson's disease

After more than 50 years of treating Parkinson's disease with l-DOPA, there are still no guidelines on setting the optimal dose for a given patient. The dopamine transporter type 1, now known as solute carrier family 6 (neurotransmitter transporter), member 3 (SLC6A3) is the most powerful determinant of dopamine neurotransmission and might therefore influence the treatment response. We recently demonstrated that methylphenidate (a dopamine transporter inhibitor) is effective in patients with Parkinson's disease with motor and gait disorders. The objective of the present study was to determine whether genetic variants of the dopamine transporter type 1-encoding gene (SLC6A3) are associated with differences in the response to treatment of motor symptoms and gait disorders with l-DOPA and methylphenidate (with respect to the demographic, the disease and the treatment parameters and the other genes involved in the dopaminergic neurotransmission). This analysis was part of a multicentre, parallel-group, double-blind, placebo-controlled, randomized clinical trial of methylphenidate in Parkinson's disease (Protocol ID:2008-005801-20; ClinicalTrials.gov:NCT00914095). We scored the motor Unified Parkinson's Disease Rating Scale and the Stand-Walk-Sit Test before and after a standardized acute l-DOPA challenge before randomization and then after 3 months of methylphenidate treatment. Patients were screened for variants of genes involved in dopamine metabolism: rs28363170 and rs3836790 polymorphisms in the SLC6A3 gene, rs921451 and rs3837091 in the DDC gene (encoding the aromatic L-amino acid decarboxylase involved in the synthesis of dopamine from l-DOPA), rs1799836 in the MAOB gene (coding for monoamine oxidase B) and rs4680 in the COMT gene (coding for catechol-O-methyltransferase). Investigators and patients were blinded to the genotyping data throughout the study. Eighty-one subjects were genotyped and 61 were analysed for their acute motor response to l-DOPA. The SLC6A3 variants were significantly associated with greater efficacy of l-DOPA for motor symptoms. The SLC6A3 variants were also associated with greater efficacy of methylphenidate for motor symptoms and gait disorders in the ON l-DOPA condition. The difference between motor Unified Parkinson's Disease Rating Scale scores for patients with different SLC6A3 genotypes was statistically significant in a multivariate analysis that took account of other disease-related, treatment-related and pharmacogenetic parameters. Our preliminary results suggest that variants of SLC6A3 are genetic modifiers of the treatment response to l-DOPA and methylphenidate in Parkinson's disease. Further studies are required to assess the possible value of these genotypes for (i) guiding l-DOPA dose adaptations over the long term; and (ii) establishing the risk/benefit balance associated with methylphenidate treatment for gait disorders.

International validation of a behavioral scale in Parkinson's disease without dementia

The "Ardouin Scale of Behavior in Parkinson's Disease" is a new instrument specifically designed for assessing mood and behavior with a view to quantifying changes related to Parkinson's disease, to dopaminergic medication, and to non-motor fluctuations. This study was aimed at analyzing the psychometric attributes of this scale in patients with Parkinson's disease without dementia. In addition to this scale, the following measures were applied: the Unified Parkinson's Disease Rating Scale, the Montgomery and Asberg Depression Rating Scale, the Lille Apathy Rating Scale, the Bech and Rafaelsen Mania Scale, the Positive and Negative Syndrome Scale, the MacElroy Criteria, the Patrick Carnes criteria, the Hospital Anxiety and Depression Scale, and the Mini-International Neuropsychiatric Interview. Patients (n=260) were recruited at 13 centers across four countries (France, Spain, United Kingdom, and United States). Cronbach's alpha coefficient for domains ranged from 0.69 to 0.78. Regarding test-retest reliability, the kappa coefficient for items was higher than 0.4. For inter-rater reliability, the kappa values were 0.29 to 0.81. Furthermore, most of the items from the Ardouin Scale of Behavior in Parkinson's Disease correlated with the corresponding items of the other scales, depressed mood with the Montgomery and Asberg Depression Rating Scale (ρ=0.82); anxiety with the Hospital Anxiety and Depression Scale-anxiety (ρ=0.56); apathy with the Lille Apathy Rating Scale (ρ=0.60). The Ardouin Scale of Behavior in Parkinson's disease is an acceptable, reproducible, valid, and precise assessment for evaluating changes in behavior in patients with Parkinson's disease without dementia.

Anxiety has specific syndromal profiles in Parkinson disease: a data-driven approach

BACKGROUND

Anxiety symptoms are common in Parkinson disease (PD). Recent evidence suggests that anxiety syndromes as encountered in clinical practice may not correspond to the DSM-IV classification of anxiety disorders.

OBJECTIVE

To examine the syndromal pattern of the anxiety spectrum in a large series of patients with PD, as determined with a data-driven approach using latent class analysis (LCA).

METHODS

342 patients with PD were recruited from referrals to movement disorders or psychiatry clinics at six tertiary centers. Participants were assessed with a structured psychiatric interview and specific scales rating the severity of anxiety, depression, cognition and parkinsonism. The main outcome measure was classes of patients with a specific syndromal profile of anxiety symptoms based on LCA.

RESULTS

LCA identified four classes that were interpreted as "no anxiety or depression", "episodic anxiety without depression", "persistent anxiety with depression", and "both persistent and episodic anxiety with depression". Symptoms of persistent anxiety were almost invariably associated with symptoms of depression. There were significant differences between classes in terms of history of depression and anxiety, use of psychoactive medication, and on the Mentation and Complications sections of the Unified Parkinson Disease Rating Scale.

CONCLUSIONS

Patients with PD show different syndromic profiles of anxiety that do not align with the symptom profiles represented by DSM-IV anxiety disorders and major depression. Accordingly, DSM-IV criteria for anxiety disorders may not be clinically useful in PD. The different classes identified here provide empirically validated phenotypes for future research.

Targeting chelatable iron as a therapeutic modality in Parkinson's disease

AIMS

The pathophysiological role of iron in Parkinson's disease (PD) was assessed by a chelation strategy aimed at reducing oxidative damage associated with regional iron deposition without affecting circulating metals. Translational cell and animal models provided concept proofs and a delayed-start (DS) treatment paradigm, the basis for preliminary clinical assessments.

RESULTS

For translational studies, we assessed the effect of oxidative insults in mice systemically prechelated with deferiprone (DFP) by following motor functions, striatal dopamine (HPLC and MRI-PET), and brain iron deposition (relaxation-R2*-MRI) aided by spectroscopic measurements of neuronal labile iron (with fluorescence-sensitive iron sensors) and oxidative damage by markers of protein, lipid, and DNA modification. DFP significantly reduced labile iron and biological damage in oxidation-stressed cells and animals, improving motor functions while raising striatal dopamine. For a pilot, double-blind, placebo-controlled randomized clinical trial, early-stage Parkinson's patients on stabilized dopamine regimens enrolled in a 12-month single-center study with DFP (30 mg/kg/day). Based on a 6-month DS paradigm, early-start patients (n=19) compared to DS patients (n=18) (37/40 completed) responded significantly earlier and sustainably to treatment in both substantia nigra iron deposits (R2* MRI) and Unified Parkinson's Disease Rating Scale motor indicators of disease progression (p<0.03 and p<0.04, respectively). Apart from three rapidly resolved neutropenia cases, safety was maintained throughout the trial.

INNOVATION

A moderate iron chelation regimen that avoids changes in systemic iron levels may constitute a novel therapeutic modality for PD.

CONCLUSIONS

The therapeutic features of a chelation modality established in translational models and in pilot clinical trials warrant comprehensive evaluation of symptomatic and/or disease-modifying potential of chelation in PD.