Laterality, region, and type of motor dysfunction correlate with cognitive impairment in Parkinson's disease

Association between cognitive performance and manual dexterity in patients with Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is a progressive neurological condition resulting from the degeneration of dopaminergic neurons in the substantia nigra. Impaired manual dexterity and cognitive impairment are common symptoms and are often associated with recurrent adverse events in this population.

OBJECTIVE

To verify the association between cognitive performance and manual dexterity in people with PD.

METHODS

This is a cross-sectional observational study, with 29 participants, who underwent cognitive and manual dexterity assessments, and the following tools were used: Trail Making Test, box and block test (BBT), Learning Test of Rey and Nine Hole Peg Test. Descriptive statistics for clinical and demographic data were performed using mean and standard deviation, and data normality was assessed using the Shapiro-Wilk test. Spearman's nonparametric test was used to determine the correlation between variables.

RESULTS

Our findings revealed significant associations between cognitive performance and manual dexterity. The nine-hole peg test positively correlated with TMT-Part A and Part B, establishing a relationship between manual dexterity and cognitive functions such as attention and mental flexibility. On the other hand, BBT showed an inverse relationship with TMT-Part B, indicating that longer time on this task was associated with lower manual dexterity.

CONCLUSION

Fine manual dexterity had a significant correlation with visual search skills and motor speed, while gross motor dexterity had a negative correlation with cognitive skills. No significant results were demonstrated regarding the interaction between manual dexterity and memory.

Transcranial Direct Current Stimulation Over Motor Areas Improves Reaction Time in Parkinson's Disease

Background

Transcranial direct current stimulation (tDCS) has been shown to modulate cortical motor excitability and improve bradykinesia symptoms in Parkinson's disease. It is unclear how targeting different cortical motor areas with tDCS may differentially influence upper limb function for individuals diagnosed with PD.

Objective

This study investigated whether anodal tDCS applied separately to the primary motor cortex and the supplementary motor area would improve upper limb function for individuals with Parkinson's disease. In addition, a startling acoustic stimulus was used to differentiate between the effect of stimulation on motor preparatory and initiation processes associated with upper limb movements.

Methods

Eleven participants with idiopathic Parkinson's disease performed two upper limb simple reaction time tasks, involving elbow extension or a button press before and after either anodal tDCS or sham tDCS was applied over the primary motor cortex or supplementary motor area. A loud, startling stimulus was presented on a selection of trials to involuntarily trigger the prepared action.

Results

Anodal tDCS led to improved premotor reaction time in both tasks, but this was moderated by reaction time in pre-tDCS testing, such that individuals with slower pre-tDCS reaction time showed the greatest reaction time improvements. Startle-trial reaction time was not modified following tDCS, suggesting that the stimulation primarily modulated response initiation processes.

Conclusion

Anodal tDCS improved response initiation speed, but only in slower reacting individuals with PD. However, no differences attributable to tDCS were observed in clinical measures of bradykinesia or kinematic variables, suggesting that reaction time may represent a more sensitive measure of some components of bradykinesia.

Can Levodopa Challenge Testing Predict the Effect of Deep Brain Stimulation? One-Year Outcomes in a Chinese Cohort

Objective: Our study examined whether levodopa challenge test (LCT) results could predict quality of life (QoL) outcomes after surgery to implant subthalamic nucleus deep brain stimulation (STN-DBS) electrodes to treat advanced Parkinson’s disease (PD).

Methods: Forty patients with STN-DBS underwent a follow-up 1 year after implantation surgery to analyze the correlation between preoperative levodopa impact test results and postoperative Unified Parkinson’s Disease Rating Scale (UPDRS) III motor score, postoperative PD Questionnaire-39 (PDQ-39) score, and PDQ-39 improvement.

Results: Improvements in QoL were associated with several preoperative characteristics including preoperative UPDRS-III tremor, UPDRS-III tremor (off-60) (p = 0.049), UPDRS-III tremor (off-120) (p = 0.012), Mini-Mental State Examination (p = 0.012), and PDQ-39 (p = 0.012) before surgery. Multiple linear regression model using preoperative MMSE [odds ratio (OR) = 0.342, 95% confidence interval (CI) = 0.051–2.297], preoperative UPDRS-III tremor (OR = 2.099, 95% CI = 0.585–7.535), UPDRS-III tremor (off-60) [OR = 1.316, 95% CI = 0.804–2.154, UPDRS-III tremor (off-120) OR = 0.913, 95% CI = 0.691–1.207], correctly classified 88.5% of patients.

Conclusion: Levodopa challenge test results cannot predict the effect of DBS. However, the test can be incorporated into a regression prediction model to the quality of life of PD patients after DBS with other preoperative factors.

Executive function network's white matter alterations relate to Parkinson's disease motor phenotype

Parkinson's disease (PD) patients with postural instability and gait disorder phenotype (PIGD) are at high risk of cognitive deficits compared to those with tremor dominant phenotype (TD). Alterations of white matter (WM) integrity can occur in patients with normal cognitive functions (PD-N). However, the alterations of WM integrity related to cognitive functions in PD-N, especially in these two motor phenotypes, remain unclear. Diffusion tensor imaging (DTI) is a non-invasive neuroimaging method to evaluate WM properties and by applying DTI tractography, one can identify WM tracts connecting functional regions. Here, we 1) compared the executive function (EF) in PIGD phenotype with normal cognitive functions (PIGD-N) and TD phenotype with normal cognitive functions (TD-N) phenotypes; 2) used DTI tractography to evaluated differences in WM alterations between these two phenotypes within a task-based functional network; and 3) examined the WM integrity alterations related to EF in a whole brain network for PD-N patients regardless of phenotypes. Thirty-four idiopathic PD-N patients were classified into two groups based on phenotypes: TD-N and PIGD-N, using an algorithm based on UPDRS part III. Neuropsychological tests were used to evaluate patients' EF, including the Trail making test part A and B, the Stroop color naming, the Stroop word naming, the Stroop color-word interference task, as well as the FAS verbal fluency task and the animal category fluency tasks. DTI measures were calculated among WM regions associated with the verbal fluency network defined from previous task fMRI studies and compared between PIGD-N and TD-N groups. In addition, the relationship of DTI measures and verbal fluency scores were evaluated for our full cohort of PD-N patients within the whole brain network. These values were also correlated with the scores of the FAS verbal fluency task. Only the FAS verbal fluency test showed significant group differences, having lower scores in PIGD-N when compared to TD-N phenotype (p < 0.05). Compared to the TD-N, PIGD-N group exhibited significantly higher MD and RD in the tracts connecting the left superior temporal gyrus and left insula, and those connecting the right pars opercularis and right insula. Moreover, compared to TD-N, PIGD-N group had significantly higher RD in the tracts connecting right pars opercularis and right pars triangularis, and the tracts connecting right inferior temporal gyrus and right middle temporal gyrus. For the entire PD-N cohort, FAS verbal fluency scores positively correlated with MD in the superior longitudinal fasciculus (SLF). This study confirmed that PIGD-N phenotype has more deficits in verbal fluency task than TD-N phenotype. Additionally, our findings suggest: (1) PIGD-N shows more microstructural changes related to FAS verbal fluency task when compared to TD-N phenotype; (2) SLF plays an important role in FAS verbal fluency task in PD-N patients regardless of motor phenotypes.

The Characteristics of Cognitive Impairment in ALS Patients Depend on the Lateralization of Motor Damage

(1) Background: Cognitive features of patients with amyotrophic lateral sclerosis (ALS) have never been specifically analyzed according to the lateralization of motor impairment. In the present study we investigated the cognitive performances of ALS patients to describe the relationship between motor and cognitive dysfunction, according to site and side of disease onset. (2) Methods: Six-hundred and nine ALS patients underwent a comprehensive neuropsychological evaluation at diagnosis in Turin ALS Centre Tests included—mini-mental state examination (MMSE), frontal assessment battery (FAB), trail-making test A/B (TMT A-B), digit span forward and backward (digit span FW/digit span BW), letter fluency test (FAS), category fluency test (CAT), Rey auditory verbal learning test (RAVLT), Babcock story recall test (BSRT), Rey-Osterrieth complex figure test (ROCFT), Wisconsin card sorting test (WCST), Raven’s coloured progressive matrices (CPM47). Cognitive performances of patients, grouped by side and site of onset, were statistically compared using z-scores, as appropriate. (3) Results: Bulbar patients and bilateral spinal onset patients (S_bil) were generally characterized by lower cognitive performances in most neuropsychological tests, when compared to patients with lateralized onset (right-side spinal onset, S_ri and left-side spinal onset, S_le). Digit span backward and visual memory task (ROCFT) median z-scores were significantly higher, reflecting a better cognitive performance, in S_ri patients when compared to bulbar/S_bil patients, while verbal memory tasks (RAVLT and BRST) resulted in significantly higher scores in S_le patients. Our results are in keeping with hemispheric functional lateralization of language and visuospatial abilities. (4) Conclusions: In ALS patients, as in other neurodegenerative diseases, we found a direct relationship between lateralized motor and cognitive features.

Pathological Influences on Clinical Heterogeneity in Lewy Body Diseases

PD, PD with dementia, and dementia with Lewy bodies are clinical syndromes characterized by the neuropathological accumulation of alpha-synuclein in the CNS that represent a clinicopathological spectrum known as Lewy body disorders. These clinical entities have marked heterogeneity of motor and nonmotor symptoms with highly variable disease progression. The biological basis for this clinical heterogeneity remains poorly understood. Previous attempts to subtype patients within the spectrum of Lewy body disorders have centered on clinical features, but converging evidence from studies of neuropathology and ante mortem biomarkers, including CSF, neuroimaging, and genetic studies, suggest that Alzheimer's disease beta-amyloid and tau copathology strongly influence clinical heterogeneity and prognosis in Lewy body disorders. Here, we review previous clinical biomarker and autopsy studies of Lewy body disorders and propose that Alzheimer's disease copathology is one of several likely pathological contributors to clinical heterogeneity of Lewy body disorders, and that such pathology can be assessed in vivo. Future work integrating harmonized assessments and genetics in PD, PD with dementia, and dementia with Lewy bodies patients followed to autopsy will be critical to further refine the classification of Lewy body disorders into biologically distinct endophenotypes. This approach will help facilitate clinical trial design for both symptomatic and disease-modifying therapies to target more homogenous subsets of Lewy body disorders patients with similar prognosis and underlying biology. © 2019 International Parkinson and Movement Disorder Society.

Relationship between cognitive performance and mobility in patients with Parkinson's disease: A cross-sectional study

Gait disorders may be associated with cognitive impairment, and slow speed predicts cognitive impairment and dementia. Objective: To investigate the relationships between cognitive function and gait performance in patients with Parkinson’s disease (PD) who attended a hospital neurorehabilitation program. Methods: Descriptive and inferential statistics (Pearson’s correlation) were used for data analysis. The cognitive functions were evaluated through Digit Span, Mental Control, Trail Making Test, Phonemic Verbal Fluency Task, and Addenbrooke’s Cognitive Examination III. The motor function was assessed through 10-meter walk test, Mini BESTest and Timed Up and Go Test. Results: A total of 65 patients were included in this study. Of these, 66.15% were males, mean age was 61.14 (8.39) years, mean educational was 12 (8) years, disease progression time was 5.45 (4.37) years. 64.61% were in stages I and II of the Hoehn and Yahr stage. The correlation analyses showed that balance skills are significantly correlated with the ability to switch attention between two tasks and visuospatial function. The function mobility showed a significant correlation with cognitive tests. Conclusion: Data suggest the importance of the aspects of switch attention and mental flexibility in gait, evidencing the greater difficulty for double tasks.

Motor cognition in patients treated with subthalamic nucleus deep brain stimulation: Limits of compensatory overactivity in Parkinson's disease

Recent fMRI findings revealed that impairment in a serial prediction task in patients suffering from Parkinson's disease (PD) results from hypoactivity of the SMA. Furthermore, hyperactivity of the lateral premotor cortex sustained performance after withdrawal of medication. To further explore these findings, we here examined the impact of deep brain stimulation of the subthalamic nucleus on the activity of the putamen and premotor areas while performing the serial prediction task. To this end, we measured eight male PD patients ON and OFF deep brain stimulation and eight healthy age-matched male controls using [¹⁵O] water positron emission tomography to measure regional cerebral blood flow. As expected, PD patients showed poorer performance than healthy controls while performance did not differ between OFF and ON stimulation. Hypoactivity of the putamen and hyperactivity of the left lateral premotor cortex was found in patients compared to controls. Lateral premotor hyperactivity further increased OFF compared to ON stimulation and was positively related to task performance. These results confirm that the motor loop's dysfunction has impact on cognitive processes (here: prediction of serial stimuli) in PD. Extending prior data regarding the role of the lateral premotor cortex in cognitive compensation, our results indicate that lateral premotor cortex hyperactivity, while beneficial in moderate levels of impairment, might fail to preserve performance in more severe stages of the motor loop's degeneration.

Predicting early cognitive decline in newly-diagnosed Parkinson's patients: A practical model

OBJECTIVE

To create a multivariable model to predict early cognitive decline among de novo patients with Parkinson's disease, using brief, inexpensive assessments that are easily incorporated into clinical flow.

METHODS

Data for 351 drug-naïve patients diagnosed with idiopathic Parkinson's disease were obtained from the Parkinson's Progression Markers Initiative. Baseline demographic, disease history, motor, and non-motor features were considered as candidate predictors. Best subsets selection was used to determine the multivariable baseline symptom profile that most accurately predicted individual cognitive decline within three years.

RESULTS

Eleven per cent of the sample experienced cognitive decline. The final logistic regression model predicting decline included five baseline variables: verbal memory retention, right-sided bradykinesia, years of education, subjective report of cognitive impairment, and REM behavior disorder. Model discrimination was good (optimism-adjusted concordance index = .749). The associated nomogram provides a tool to determine individual patient risk of meaningful cognitive change in the early stages of the disease.

CONCLUSIONS

Through the consideration of easily-implemented or routinely-gathered assessments, we have identified a multidimensional baseline profile and created a convenient, inexpensive tool to predict cognitive decline in the earliest stages of Parkinson's disease. The use of this tool would generate prediction at the individual level, allowing clinicians to tailor medical management for each patient and identify at-risk patients for clinical trials aimed at disease modifying therapies.

Predicting the multi-domain progression of Parkinson's disease: a Bayesian multivariate generalized linear mixed-effect model

BACKGROUND

It is challenging for current statistical models to predict clinical progression of Parkinson's disease (PD) because of the involvement of multi-domains and longitudinal data.

METHODS

Past univariate longitudinal or multivariate analyses from cross-sectional trials have limited power to predict individual outcomes or a single moment. The multivariate generalized linear mixed-effect model (GLMM) under the Bayesian framework was proposed to study multi-domain longitudinal outcomes obtained at baseline, 18-, and 36-month. The outcomes included motor, non-motor, and postural instability scores from the MDS-UPDRS, and demographic and standardized clinical data were utilized as covariates. The dynamic prediction was performed for both internal and external subjects using the samples from the posterior distributions of the parameter estimates and random effects, and also the predictive accuracy was evaluated based on the root of mean square error (RMSE), absolute bias (AB) and the area under the receiver operating characteristic (ROC) curve.

RESULTS

First, our prediction model identified clinical data that were differentially associated with motor, non-motor, and postural stability scores. Second, the predictive accuracy of our model for the training data was assessed, and improved prediction was gained in particularly for non-motor (RMSE and AB: 2.89 and 2.20) compared to univariate analysis (RMSE and AB: 3.04 and 2.35). Third, the individual-level predictions of longitudinal trajectories for the testing data were performed, with ~80% observed values falling within the 95% credible intervals.

CONCLUSIONS

Multivariate general mixed models hold promise to predict clinical progression of individual outcomes in PD.

TRIAL REGISTRATION

The data was obtained from Dr. Xuemei Huang's NIH grant R01 NS060722 , part of NINDS PD Biomarker Program (PDBP). All data was entered within 24 h of collection to the Data Management Repository (DMR), which is publically available ( https://pdbp.ninds.nih.gov/data-management ).

Disrupted Brain Network Hubs in Subtype-Specific Parkinson's Disease

BACKGROUND/AIMS

The topological organization of brain functional networks is impaired in Parkinson's disease (PD). However, the altered patterns of functional network hubs in different subtypes of PD are not completely understood.

METHODS

3T resting-state functional MRI and voxel-based graph-theory analysis were employed to systematically investigate the intrinsic functional connectivity patterns of whole-brain networks. We enrolled 31 patients with PD (12 tremor dominant [TD] and 19 with postural instability/gait difficulty [PIGD]) and 22 matched healthy controls. Whole-brain voxel-wise functional networks were constructed by measuring the temporal correlations of each pair of brain voxels. Functional connectivity strength was calculated to explore the brain network hubs.

RESULTS

We found that both the TD and PIGD subtypes had comprehensive disrupted regions. These mainly involved the basal ganglia, cerebellum, superior temporal gyrus, pre- and postcentral gyri, inferior frontal gyrus, middle temporal gyrus, lingual gyrus, insula, and parahippocampal gyrus. Furthermore, the PIGD subgroup had more disrupted hubs in the cerebellum than the TD subgroup. These disruptions of hub connectivity were not correlated with the HY stage or disease duration.

CONCLUSION

Our results emphasize the subtype-specific PD-related degeneration of brain hubs, providing novel insights into the pathophysiological mechanisms of connectivity dysfunction in different PD subgroups.

Associations between cognitive impairment and motor dysfunction in Parkinson's disease

INTRODUCTION

Numerous studies have been carried out to explore the potential association between neurologic deficits and variable clinical manifestations of Parkinson's disease (PD). The aim of our study was to investigate the association between cognitive performance and motor dysfunction in Chinese patients with PD.

METHODS

Data from 96 patients with PD were obtained from the Parkinson's disease patient cohort database of Huashan Hospital. All participants underwent a comprehensive neuropsychological evaluation to assess cognitive status, that included scoring on the Mini-mental state examination (MMSE), followed by more detailed cognitive assessment on five main cognitive domains (verbal memory, nonverbal memory, visuospatial function, language and attention/executive function). Correlations between cognitive and motor scores were investigated after controlling for age, disease duration, education, and gender.

RESULTS

We report a significant correlation between subdomains of cognitive impairment and motor dysfunction using analyses of the multiple linear regression. Notably, executive function and attention was significantly associated with bradykinesia and rigidity, while visuospatial function was associated with bradykinesia and tremor.

CONCLUSIONS

The association between motor dysfunction and cognitive decline in PD might highlight deficits represented by a shared neurochemical pathway.

Improvement in Language Function Correlates with Gait Improvement in Drug-naïve Parkinson's Disease Patients Taking Dopaminergic Medication

BACKGROUND

Dopaminergic drugs, the gold standard for motor symptoms, are known to affect cognitive function in Parkinson's disease (PD) patients.

OBJECTIVE

We compared the effects of dopaminergic treatment on motor and cognitive function in drug-naïve patients.

METHODS

Dopaminergic medication (levodopa, dopamine agonist, selegiline) was given to 27 drug-naïve PD patients and increased to a dose optimal for improved motor symptoms. Patients were tested prior to, and 4-7 months after, drug initiation. Motor function was assessed using the Unified Parkinson's Disease Rating Scale (UPDRS). Cognitive function was assessed using both the Japanese version of the Montreal Cognitive Assessment (MoCA-J) and the Neurobehavioral Cognitive Status Examination (COGNISTAT-J). Improvements from baseline for both motor and cognitive assessment were compared.

RESULTS

Mean score of all motor assessments (UPDRS total score of Parts II and III, and sub-scores of tremor, rigidity, bradykinesia, gait, and postural instability) and certain cognitive assessments (MoCA-J total score and subscore of delayed recall) significantly improved with dopaminergic medication. Gait score improvement showed significant positive correlation with improvement in MoCA-J language domain and in language-comprehension subtests of COGNISTAT-J using Spearman's correlation coefficients. Furthermore, multiple regression analysis showed gait score improvement significantly correlated with improvements in the subtests of language-comprehension in COGNISTAT-J.

CONCLUSION

There is correlated improvement in both gait and language function in de novo PD patients in response to dopaminergic drugs. Gait and language dysfunction in these patients may share a common pathophysiology linked to dopamine deficits.

The impact of biological sex and sex hormones on cognition in a rat model of early, pre-motor Parkinson's disease

Parkinson's disease (PD) is well known for motor deficits such as bradykinesia. However, patients often experience additional deficits in working memory, behavioral selection, decision-making and other executive functions. Like other features of PD, the incidence and severity of these cognitive symptoms differ in males and females. However, preclinical models have not been used to systematically investigate the roles that sex or sex hormones may play in these complex signs. To address this, we used a Barnes maze spatial memory paradigm to compare the effects of a bilateral nigrostriatal dopamine lesion model of early PD on cognitive behaviors in adult male and female rats and in adult male rats that were gonadectomized or gonadectomized and supplemented with testosterone or estradiol. We found that dopamine lesions produced deficits in working memory and other executive operations, albeit only in male rats where circulating androgen levels were physiological. In males where androgen levels were depleted, lesions produced no additional Barnes maze deficits and attenuated those previously linked to androgen deprivation. We also found that while most measures of Barnes maze performance were unaffected by dopamine lesions in the females, lesions did induce dramatic shifts from their preferred use of thigmotactic navigation to the use of spatially guided place strategies similar to those normally preferred by males. These and other sex- and sex hormone-specific differences in the effects of nigrostriatal dopamine lesions on executive function highlight the potential of gonadal steroids as protective and/or therapeutic for the cognitive symptoms of PD. However, their complexity also indicates the need for a more thorough understanding of androgen and estrogen effects in guiding the development of hormone therapies that might effectively address these non-motor signs.

Mild cognitive impairment in Parkinson's disease versus Alzheimer's disease

INTRODUCTION

No known studies have compared longitudinal characteristics between individuals with incident mild cognitive impairment due to Parkinson's disease (PD-MCI) versus Alzheimer's Disease (AD-MCI).

METHODS

We used longitudinal data from the National Alzheimer's Coordinating Center's Uniform Data Set to compare 41 PD-MCI and 191 AD-MCI participants according to their demographics, presence of ≥1 APOE e4 allele, and baseline and change over time in clinical characteristics, neuropsychological test scores, and Clinical Dementia Rating sum of boxes (CDR-SB). Multivariable linear regression models with generalized estimating equations were used to account for clustered data and to test for baseline and longitudinal differences in neuropsychological test scores.

RESULTS

PD-MCI and AD-MCI participants differed by many demographic and clinical characteristics. Significantly fewer PD-MCI participants developed dementia over one year. Compared to AD-MCI participants, PD-MCI participants performed better at baseline and over time on a global measure of cognition (Mini Mental State Exam), memory measures (immediate and delayed Logical Memory), and a language measure (Boston Naming Test), and additionally performed better over time on an attention measure (Digit Span Forward), a language measure (Vegetable List), a processing speed measure (Digit Symbol), and an overall measure of memory and functional impairment (CDR-SB).

CONCLUSION

Our study provides further evidence that PD-MCI is clinically distinct from AD-MCI and requires different tools for diagnosis and monitoring clinical progression. More importantly, this study suggests that PD-MCI takes longer to convert into dementia than AD-MCI, findings that require replication by other studies.

Side and type of initial motor symptom influences visuospatial functioning in Parkinson's disease

BACKGROUND/OBJECTIVES

Visuospatial problems are common in Parkinson's disease (PD) and likely stem from dysfunction in dopaminergic pathways and consequent disruption of cortical functioning. Characterizing the motor symptoms at disease onset provides a method of observing how dysfunction in these pathways influences visuospatial cognition. We examined two types of motor characteristics: Body side (left or right) and type of initial symptom (tremor or symptom other than tremor).

METHODS

31 non-demented patients with PD, 16 with left-side onset (LPD) and 15 with right-side onset (RPD), as well as 17 healthy control participants (HC). The PD group was also divided by type of initial motor symptom, 15 having tremor as the initial symptom and 16 having an initial symptom other than tremor. Visuospatial function was assessed with the Clock Drawing Test.

RESULTS

Of the four Clock Drawing scoring methods used, the Rouleau method showed sensitivity to subgroup differences. As predicted, the LPD and non-tremor subgroups, but not the other subgroups, performed more poorly than the HC group.

CONCLUSION

The findings provide further evidence for differences in cognition between these subtypes of PD and highlight the importance of considering disease subtypes when examining cognition.

Neural substrates of motor and non-motor symptoms in Parkinson's disease: a resting FMRI study

Background

Recently, non-motor symptoms of Parkinson’s disease (PD) have been considered crucial factors in determining a patient’s quality of life and have been proposed as the predominant features of the premotor phase. Researchers have investigated the relationship between non-motor symptoms and the motor laterality; however, this relationship remains disputed. This study investigated the neural connectivity correlates of non-motor and motor symptoms of PD with respect to motor laterality.

Methods

Eight-seven patients with PD were recruited and classified into left-more-affected PD (n = 44) and right-more affected PD (n = 37) based on their MDS-UPDRS (Movement Disorder Society-sponsored revision of the Unified Parkinson’s Disease Rating Scale) motor examination scores. The patients underwent MRI scanning, which included resting fMRI. Brain regions were labeled as ipsilateral and contralateral to the more-affected body side. Correlation analysis between the functional connectivity across brain regions and the scores of various symptoms was performed to identify the neural connectivity correlates of each symptom.

Results

The resting functional connectivity centered on the ipsilateral inferior orbito-frontal area was negatively correlated with the severity of non-motor symptoms, and the connectivity of the contralateral inferior parietal area was positively correlated with the severity of motor symptoms (p < 0.001, |r| > 0.3).

Conclusions

These results suggest that the inferior orbito-frontal area may play a crucial role in non-motor dysfunctions, and that the connectivity information may be utilized as a neuroimaging biomarker for the early diagnosis of PD.

Paradoxical effect of dopamine medication on cognition in Parkinson's disease: relationship to side of motor onset

Parkinson's disease (PD) is characterized by asymmetric motor symptom onset attributed to greater degeneration of dopamine neurons contralateral to the affected side. However, whether motor asymmetries predict cognitive profiles in PD, and to what extent dopamine influences cognition remains controversial. This study evaluated cognitive variability in PD by measuring differential response to dopamine replacement therapy (DRT) based on hemispheric asymmetries. The influence of DRT on cognition was evaluated in mild PD patients (n = 36) with left or right motor onset symptoms. All subjects were evaluated on neuropsychological measures on and off DRT and compared to controls (n = 42). PD patients were impaired in executive, memory and motor domains irrespective of side of motor onset, although patients with left hemisphere deficit displayed greater cognitive impairment. Patients with right hemisphere deficit responded to DRT with significant improvement in sensorimotor deficits, and with corresponding improvement in attention and verbal memory functions. Conversely, patients with greater left hemisphere dopamine deficiency did not improve in attentional functions and declined in verbal memory recall following DRT. These findings support the presence of extensive mild cognitive deficits in early PD not fully explained by dopamine depletion alone. The paradoxical effects of levodopa on verbal memory were predicted by extent of fine motor impairment and sensorimotor response to levodopa, which reflects extent of dopamine depletion. The findings are discussed with respect to factors influencing variable cognitive profiles in early PD, including hemispheric asymmetries and differential response to levodopa based on dopamine levels predicting amelioration or overdosing.

Relationship between Cognitive Performance and Motor Dysfunction in Patients with Parkinson's Disease: A Pilot Cross-Sectional Study

The aim of this pilot cross-sectional study was to extensively investigate the relationships between cognitive performance and motor dysfunction involving balance and gait ability in patients with Parkinson's disease. Twenty subjects with Parkinson's disease underwent a cognitive (outcomes: Frontal Assessment Battery-Italian version, Montreal overall Cognitive Assessment, Trail Making Test, Semantic Verbal Fluency Test, and Memory with Interference Test) and motor (outcomes: Berg Balance Scale, 10-Meter Walking Test, 6-Minute Walking Test, Timed Up and Go Test performed also under dual task condition, and Unified Parkinson's Disease Rating Scale) assessment. Our correlation analyses showed that balance skills are significantly correlated with executive functions, cognitive impairment, and ability to switch attention between two tasks. Furthermore, functional mobility showed a significant correlation with cognitive impairment, verbal fluency, and ability to switch attention between two tasks. In addition, the functional mobility evaluated under the dual task condition showed a significant correlation with cognitive impairment and ability to switch attention between two tasks. These findings might help early identification of cognitive deficits or motor dysfunctions in patients with Parkinson's disease who may benefit from rehabilitative strategies. Future prospective larger-scale studies are needed to strengthen our results.

Heterogeneity among patients with Parkinson's disease: cluster analysis and genetic association

The clinical heterogeneity of Parkinson's disease (PD) reveals the presence of several PD subtypes. The objectives of this study were to identify PD subtypes using cluster analysis (CA) and to determine the association between the subtypes and the polymorphisms in LRRK2 (G2385R and R1628P) and GBA (L444P) genes. A k-means CA of demographics, disease progression, motor and non-motor symptoms was performed from 1,510 Chinese PD patients from the Chinese National Consortium on Neurodegenerative Diseases. Pearson correlation analysis was performed to eliminate uninformative characteristics. Blood samples from 852 patients were obtained for genetic analysis of LRRK2 and GBA. Genotypic associations between various subtypes and genetic variants were examined using chi-square test. We identified four different subtypes: subtype 1 was non-tremor dominant (NTD, n=469; 31.1%); subtype 2 had a rapid disease progression with late onset (RDP-LO, n=67; 4.4%); subtype 3 had benign pure motor characteristics (BPM, n=778; 51.5%) without non-motor disturbances; and subtype 4 was tremor dominant with slow disease progression (TD-SP, n=196; 13.0%). Subtypes 1, 2, and 4 had similar mean age of onset. No associations were identified between polymorphisms in LRRK2 (R1628P) and GBA (L444P) genes and the four subtypes (P>0.05).

Postural Instability and Cognitive Dysfunction in Early Parkinson's Disease

Background:

Postural instability is one of the most disabling features of Parkinson's disease, usually occurring in late and advanced stages. The aim of this study was to investigate the postural performance of early-stage de novo Parkinson's disease patients with no clinical postural instability using computerized dynamic posturography. We sought to understand the relationship between postural sway and disease severity and the relationship between postural instability quantitatively measured by computerized dynamic posturography and cognitive impairment in early-stage Parkinson's disease patients.

Method:

Thirty-one subjects with Parkinson's disease and 20 healthy controls were assessed by the computerized dynamic posturography protocol using the sensory organization test and the motor control test. A neuropsychological assessment was also administered.

Results:

The mean equilibrium score for sensory organization test and the vestibular input ratio were significantly correlated with Hoehn-Yahr stage. No associations between motor latency for any motor control test condition and Hoehn-Yahr stage were found. The equilibrium score for sensory organization test correlated with the mini-mental status examination scores. There was a significant correlation between motor latency for large backward translation and mini-mental status examination scores. There were significant correlations between visual perception/construction/ memory of the neuropsychological battery test and the equilibrium score for sensory organization test and between verbal word learning test, controlled word association test and motor latency for large backward translation.

Conclusion:

These findings showed the postural instability present in early-stage (Hoehn-Yahr stage 2-2.5) Parkinson's disease. We also found a close relationship between postural instability and cognitive function in Parkinson's disease patients.

Enhanced efficacy of human brain-derived neural stem cells by transplantation of cell aggregates in a rat model of Parkinson's disease

Objective

Neural tissue transplantation has been a promising strategy for the treatment of Parkinson's disease (PD). However, transplantation has the disadvantages of low-cell survival and/or development of dyskinesia. Transplantation of cell aggregates has the potential to overcome these problems, because the cells can extend their axons into the host brain and establish synaptic connections with host neurons. In this present study, aggregates of human brain-derived neural stem cells (HB-NSC) were transplanted into a PD animal model and compared to previous report on transplantation of single-cell suspensions.

Methods

Rats received an injection of 6-OHDA into the right medial forebrain bundle to generate the PD model and followed by injections of PBS only, or HB-NSC aggregates in PBS into the ipsilateral striatum. Behavioral tests, multitracer (2-deoxy-2-[¹⁸F]-fluoro-D-glucose ([¹⁸F]-FDG) and [¹⁸F]-N-(3-fluoropropyl)-2-carbomethoxy-3-(4-iodophenyl)nortropane ([¹⁸F]-FP-CIT) microPET scans, as well as immunohistochemical (IHC) and immunofluorescent (IF) staining were conducted to evaluate the results.

Results

The stepping test showed significant improvement of contralateral forelimb control in the HB-NSC group from 6-10 weeks compared to the control group (p<0.05). [¹⁸F]-FP-CIT microPET at 10 weeks posttransplantation demonstrated a significant increase in uptake in the HB-NSC group compared to pretransplantation (p<0.05). In IHC and IF staining, tyrosine hydroxylase and human β2 microglobulin (a human cell marker) positive cells were visualized at the transplant site.

Conclusion

These results suggest that the HB-NSC aggregates can survive in the striatum and exert therapeutic effects in a PD model by secreting dopamine.

Executive dysfunction in Parkinson's disease: a review

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

Grooved Pegboard Predicates More of Cognitive Than Motor Involvement in Parkinson’s Disease

The Grooved Pegboard Test (GPT) was conceived as a test of manual dexterity, upper-limb motor speed, and hand–eye coordination. The aim of our study was to test the componential structure of the GPT on an archetypal model of motor impairment, Parkinson’s disease (PD). A total of 45 PD patients (33 males, 12 females; age M = 67, range = 49-81; PD duration M = 10, range = 6-20 years; H/Y stage 2, range = 2-3) and 20 age- and education-matched controls (14 males, 6 females; age M = 66, range = 48-80) were included. All participants were investigated using the GPT, Short Falls Efficacy Scale–International, Frontal Assessment Battery (FAB), Montreal Cognitive Assessment (MoCA), and Non-Motor Symptom Scale. Patients were followed for 6 months, using fall diaries and monthly phone calls to define PD fallers (falls ≥ 1; n = 27) and PD nonfallers (falls = 0; n = 18). Using structural equation modeling, the GPT predicted performance on the MoCA ( p < .001), but not on the FAB ( p = .29). In conclusion, analysis of the structure of the GPT provided evidence about important cognitive features, in addition to the motor component of this test in PD.

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

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

Unilateral deep brain stimulation surgery in Parkinson's disease improves ipsilateral symptoms regardless of laterality

PURPOSE

Researchers have consistently observed in right-handed individuals across normal and disease states that the 'dominant' left hemisphere has greater ipsilateral control of the left side than the right hemisphere has over the right. We sought to determine whether this ipsilateral influence of the dominant hemisphere reported in Parkinson's disease extends to treatments such as deep brain stimulation (DBS) and whether it affects outcome. We hypothesised that among Parkinson right-handers, unilateral left DBS would provide greater ipsilateral motor improvement compared with the ipsilateral motor improvement experienced on the right side.

SCOPE

A total of 73 Parkinson patients who underwent unilateral DBS of the subthalamic nucleus (STN) or globus palidus internus (GPi) participated. Left and right 'composite scores', were computed by separately adding all items on the left and right side from the motor section of the Unified Parkinson Disease Rating Scale. The change in the pre- and 4-month post-implantation score was the primary outcome measure. The mean motor scores improved by 4.96 ± 11.79 points (p < 0.001) post-surgery on the ipsilateral side of the DBS implantation. Regression analyses revealed that the side (left vs. right) and target (STN vs. GPi) did not significantly contribute in the effect of ipsilateral motor improvement (p = 0.3557).

CONCLUSION

While DBS on the 'dominant' left side failed to exert a greater ipsilateral influence compared with DBS on the non-dominant right side, significant ipsilateral motor improvements were observed after unilateral stimulation regardless of site of implantation and laterality.

Altered perceptual sensitivity to kinematic invariants in Parkinson's disease

Ample evidence exists for coupling between action and perception in neurologically healthy individuals, yet the precise nature of the internal representations shared between these domains remains unclear. One experimentally derived view is that the invariant properties and constraints characterizing movement generation are also manifested during motion perception. One prominent motor invariant is the "two-third power law," describing the strong relation between the kinematics of motion and the geometrical features of the path followed by the hand during planar drawing movements. The two-thirds power law not only characterizes various movement generation tasks but also seems to constrain visual perception of motion. The present study aimed to assess whether motor invariants, such as the two thirds power law also constrain motion perception in patients with Parkinson's disease (PD). Patients with PD and age-matched controls were asked to observe the movement of a light spot rotating on an elliptical path and to modify its velocity until it appeared to move most uniformly. As in previous reports controls tended to choose those movements close to obeying the two-thirds power law as most uniform. Patients with PD displayed a more variable behavior, choosing on average, movements closer but not equal to a constant velocity. Our results thus demonstrate impairments in how the two-thirds power law constrains motion perception in patients with PD, where this relationship between velocity and curvature appears to be preserved but scaled down. Recent hypotheses on the role of the basal ganglia in motor timing may explain these irregularities. Alternatively, these impairments in perception of movement may reflect similar deficits in motor production.

Clinical heterogeneity in patients with early-stage Parkinson's disease: a cluster analysis

The aim of this study was to investigate the clinical heterogeneity of Parkinson's disease (PD) among a cohort of Chinese patients in early stages. Clinical data on demographics, motor variables, motor phenotypes, disease progression, global cognitive function, depression, apathy, sleep quality, constipation, fatigue, and L-dopa complications were collected from 138 Chinese PD subjects in early stages (Hoehn and Yahr stages 1-3). The PD subject subtypes were classified using k-means cluster analysis according to the clinical data from five- to three-cluster consecutively. Kappa statistical analysis was performed to evaluate the consistency among different subtype solutions. The cluster analysis indicated four main subtypes: the non-tremor dominant subtype (NTD, n=28, 20.3%), rapid disease progression subtype (RDP, n=7, 5.1%), young-onset subtype (YO, n=50, 36.2%), and tremor dominant subtype (TD, n=53, 38.4%). Overall, 78.3% (108/138) of subjects were always classified between the same three groups (52 always in TD, 7 in RDP, and 49 in NTD), and 98.6% (136/138) between five- and four-cluster solutions. However, subjects classified as NTD in the four-cluster analysis were dispersed into different subtypes in the three-cluster analysis, with low concordance between four- and three-cluster solutions (kappa value=-0.139, P=0.001). This study defines clinical heterogeneity of PD patients in early stages using a data-driven approach. The subtypes generated by the four-cluster solution appear to exhibit ideal internal cohesion and external isolation.

Relation of Parkinson's disease subtypes to visual activities of daily living

Visual perceptual problems are common in Parkinson's disease (PD) and often affect activities of daily living (ADLs). PD patients with non-tremor symptoms at disease onset (i.e., rigidity, bradykinesia, gait disturbance or postural instability) have more diffuse neurobiological abnormalities and report worse non-motor symptoms and functional changes than patients whose initial symptom is tremor, but the relation of motor symptom subtype to perceptual deficits remains unstudied. We assessed visual ADLs with the Visual Activities Questionnaire in 25 non-demented patients with PD, 13 with tremor as the initial symptom and 12 with an initial symptom other than tremor, as well as in 23 healthy control participants (NC). As expected, the non-tremor patients, but not the tremor patients, reported more impairment in visual ADLs than the NC group, including in light/dark adaptation, acuity/spatial vision, depth perception, peripheral vision and visual processing speed. Non-tremor patients were significantly worse than tremor patients overall and on light/dark adaptation and depth perception. Environmental enhancements especially targeted to patients with the non-tremor PD subtype may help to ameliorate their functional disability.

Hippocampal and ventricular changes in Parkinson's disease mild cognitive impairment

We analyzed T1-weighted brain magnetic resonance imaging data of 100 cognitively normal elderly controls (NC), 127 cognitively normal Parkinson's disease (PD; PDCN) and 31 PD-associated mild cognitive impairment (PDMCI) subjects from the Norwegian ParkWest study. Using automated segmentation methods, followed by the radial distance technique and multiple linear regression we studied the effect of clinical diagnosis on hippocampal and ventricular radial distance while adjusting for age, education, and scanning site. PDCN subjects had significantly smaller bilateral hippocampal radial distance relative to NC. Nonamnestic PDMCI subjects showed smaller right hippocampal radial distance relative to NC. PDMCI subjects showed significant enlargement of all portions of the lateral ventricles relative to NC and significantly larger bilateral temporal and occipital and left frontal lateral ventricular expansion relative to PDCN subjects. Nonamnestic PDMCI subjects showed significant ventricular enlargement spanning all parts of the lateral ventricle while those with amnestic PDMCI showed changes localized to the left occipital horn. Hippocampal atrophy and lateral ventricular enlargement show promise as structural biomarkers for PD.

The relation between cognition and motor dysfunction in drug-naive newly diagnosed patients with Parkinson's disease

Recent studies have reported cognitive decline to be common in the early phase of Parkinson's disease. Imaging data connect working memory and executive functioning to the dopamine system. It has also been suggested that bradykinesia is the clinical manifestation most closely related to the nigrostriatal lesion. Exploring the relationship between motor dysfunction and cognition can help us find shared or overlapping systems serving different functions. This relationship has been sparsely investigated in population-based studies of untreated Parkinson's disease. The aim of the present study was to investigate the association between motor signs and cognitive performance in the early stages of Parkinson's disease before the intake of dopaminergic medication. Patients were identified in a population-based study of incident cases with idiopathic parkinsonism. Patients with the postural instability and gait disturbances phenotype were compared with patients with the tremor-dominant phenotype on demographics and cognitive measures. Associations between cognitive and motor scores were investigated, with age, education, and sex controlled for. Bradykinesia was associated with working memory and mental flexibility, whereas axial signs were associated with episodic memory and visuospatial functioning. No significant differences in the neuropsychological variables were found between the postural instability and gait disturbances phenotype and the tremor phenotype. Our results indicate a shared system for slow movement and inflexible thinking that may be controlled by a dopaminergic network different from dopaminergic networks involved in tremor and/or rigidity. The association between axial signs and memory and visuospatial function may point to overlapping systems or pathologies related to these abilities.

Relationship between the type and side of motor symptoms with the prevalence of non-motor symptoms in Parkinson's disease

INTRODUCTION

the relationship between laterality and asymmetry of Parkinson's disease and non-motor dysfunction has been studied mainly from the perspective of cognitive functions, and the few studies that have included other symptoms have mixed reports. The relationship between non-motor symptoms and the type of onset of the disease has not been studied in detail.

OBJECTIVE

to analyse the association between the side and type of motor onset and the prevalence of non-motor symptoms.

PATIENTS AND METHODS

we included 232 patients diagnosed with Parkinson's disease. Type of onset and the side initially affected were documented. The presence of non-motor symptoms was determined by applying the non-motor symptom questionnaire (NMSQuest).

RESULTS

when analysing the side of onset and presence of each non-motor symptom explored, statistically significant differences were found in the frequency of hallucinations (P=0.04) and sleep behaviour disorder (P<0.01) in subjects with right side onset. The motor type of onset differences were not statistically significant.

CONCLUSIONS

subjects with right side onset seem to have a higher risk of having hallucinations and sleep behaviour disorders. These symptoms should be intentionally sought in order to provide treatment and improve the patient's quality of life.

Tests of dorsolateral frontal function correlate with objective tests of postural stability in early to moderate stage Parkinson's disease

A substantial number of individuals with Parkinson's disease who display impaired postural stability experience accelerated cognitive decline and an increased prevalence of dementia. To date, studies suggest that this relationship, believed to be due to involvement of nondopaminergic circuitry, occurs later in the disease process. Research has yet to adequately investigate this cognitive-posturomotor relationship especially when examining earlier disease states. To gain greater understanding of the relationship between postural stability and cognitive function/dysfunction we evaluated a more stringent, objective measure of postural stability (center of pressure displacement), and also more specific measures of cognition in twenty-two patients with early to moderate stage Parkinson's disease. The magnitude of the center of pressure displacement in this cohort was negatively correlated with performance on tests known to activate dorsolateral frontal regions. Additionally, the postural stability item of the UPDRS exhibited poor correlation with the more objective measure of center of pressure displacement and all specific measures of cognition. These results may serve as rationale for a more thorough evaluation of postural stability and cognition especially in individuals with mild Parkinson's disease. Greater understanding of the relationship between motor and cognitive processes in Parkinson's disease will be critical for understanding the disease process and its potential therapeutic possibilities.

Motor laterality asymmetry and nonmotor symptoms in Parkinson's disease

BACKGROUND

In patients with Parkinson's disease (PD), asymmetric motor signs provide an interesting model to evaluate whether asymmetric nigrostriatal degeneration can affect neuropsychological function and other nonmotor symptoms (NMS). This study was designed to evaluate the predominant laterality of motor symptoms and its relationship with cognition and other NMS in idiopathic PD.

METHODS

Nationwide, longitudinal, and multicenter study (ELEP Registry) using outpatients with PD. Left PD (LPD) and right PD (RPD) was defined based on the motor signs on the SCOPA-motor scale. To include the clinical spectrum of asymmetric PD patients, we considered two groups of patients with mild-moderate and extreme asymmetry. Predominant LPD or RPD with mild-moderate versus extreme asymmetry were compared using the following scales: cognition, psychosis (Parkinson Psychosis Rating Scale), anxiety/depression, sleep (and autonomic dysfunction at baseline and 1 year later. Nonparametric tests were used for comparison.

RESULTS

One hundred forty-nine PD patients (74 RPD and 75 LPD) with mild-moderate asymmetry and 90 (47 RPD and 43 LPD) with extreme asymmetry and a mean age of 64.5 (10.4) years were included. Extreme RPD had higher Parkinson Psychosis Rating Scale scores over time (P = 0.005) compared with LPD, but no significant differences were observed between LPD and RPD in terms of other NMS.

CONCLUSIONS

These findings suggest that damage to left-hemisphere plays a disproportionately greater role in PD-related psychosis over time. In contrast, motor laterality does not consistently affect other NMS, suggesting that NMS are related to a more widespread brain disorder.

Mild cognitive impairment in Parkinson's disease: subtypes and motor characteristics

The aims of this project were to determine the risk factors for and clinical characteristics of mild cognitive impairment (MCI) in Parkinson's disease (PD). We performed a retrospective record review of 72 non-demented PD patients (age: 57.79 +/- 10.57, duration of PD: 7.32 +/- 4.97) who completed a standardized neurological assessment, including a full neuropsychological battery, as part of their diagnostic work-up. Of these participants, 47.2% were cognitively normal and 52.8% met criteria for MCI. The majority of MCI patients had single domain MCI (23/38), the affected domains being memory (n = 9), executive function (n = 6), visuospatial skills (n = 6), and language (n = 2). The MCI group had longer duration of disease and higher postural instability and gait disorder subscale scores than the cognitively normal group. This report provides further support for use of the concept of MCI in PD research. There may be certain disease characteristics that could alert practitioners to the emergence of cognitive changes in patients. Future studies should focus on additional risk factors for MCI subtypes and their possible progression to frank dementia.

Cognitive function in early Parkinson's disease: a population-based study

BACKGROUND AND PURPOSE

The study aims to describe the frequency, pattern and determinants of cognitive function in patients with newly diagnosed Parkinson's disease (PD); to compare patients with impaired cognition to patients with intact cognition; and to compare to matched healthy controls.

METHODS

Patients were identified in a longitudinal population based study of idiopathic non-drug induced parkinsonism. Eighty-eight newly diagnosed patients with PD and no dementia were included during a four year period. The patients and 30 age- and sex-matched healthy control subjects underwent a comprehensive neuropsychological assessment.

RESULTS

Patients performed significantly worse than healthy controls in a majority of neuropsychological tests. Test results in attention, psychomotor function, episodic memory (free recall), executive function and category fluency were significantly lower in the patient group. Comparison with normative data revealed that 30% of the patients had deficits in > or =1 cognitive domain (episodic memory, executive function and verbal function). Seventy per cent of the patients had normal performance. Unified Parkinson's Disease Rating Scale (UPDRS) III sub scores; speech, facial expression, rigidity and bradykinesia were significantly higher, and disease duration shorter amongst the cognitively impaired than amongst the cognitively intact patients. Tremor showed no difference. Education level was an independent predictor of dysfunction in patients with > or =2 cognitive domains affected.

CONCLUSION

Cognitive dysfunction is common in untreated patients in early PD, affecting attention, psychomotor function, episodic memory, executive function and category fluency. Education level was an independent predictor of severe cognitive dysfunction.

The association between motor subtypes and psychopathology in Parkinson's disease

BACKGROUND

In Parkinson's disease (PD) it has been suggested that various motor subtypes are also characterized by a different prevalence and severity of specific non-motor symptoms such as cognitive deterioration, depression, apathy and hallucinations. The aim of this study was to investigate the association between motor subtypes and psychopathology in PD.

METHODS

An exploratory and confirmatory cluster analysis of motor and psychopathological symptoms was performed with a randomized sample of 173 patients each, stemming from two research databases: one from Stavanger University Hospital and one from Maastricht University Hospital. These databases contained data of standardized assessments of patients with the Unified Parkinson's Disease Rating Scale, the Montgomery-Asberg Depression Rating Scale, and the Mini-Mental State Examination.

RESULTS

PD patients can be accurately and reliably classified into four different subtypes: rapid disease progression subtype, young-onset subtype, non-tremor-dominant subtype with psychopathology and a tremor-dominant subtype. Cognitive deterioration, depressive and apathetic symptoms, and hallucinations all cluster within the non-tremor-dominant motor subtype, that is characterized by hypokinesia, rigidity, postural instability and gait disorder.

CONCLUSIONS

This study shows that non-tremor-dominant PD is associated with cognitive deterioration, depression, apathy, and hallucinations, which has implications for future research into the pathophysiology of psychopathology in PD.

Does laterality of motor impairment tell us something about cognition in Parkinson disease?

This cross-sectional study investigates the relationship between severity of right- and left-sided motor symptoms and deficits in global cognitive function as well as individual cognitive domains in 117 Parkinson disease patients. Items of the Unified Parkinson Disease Rating Scale Part III were divided into right- and left-sided total scores. Composite scores in verbal fluency, verbal memory, executive function, and visuoperceptual skills were obtained from a full neuropsychological battery. We observed a significant association between right-sided motor impairment and verbal memory, visuoperceptual skills, and verbal fluency, but not executive function. The relationship between right symptoms and verbal fluency was fully mediated by cognitive status, while the relationship between right symptoms and verbal memory as well as visuoperceptual skills was not. Left-sided motor symptoms were not significantly related to any composite cognitive domain. When patients were divided into groups based on the side of predominant symptoms, no group differences were found in performance on the specific cognitive domains. This suggests that the degree of right-sided symptoms is more correlated to specific cognitive domains than is group classification of laterality.

Motor asymmetry and substantia nigra volume are related to spatial delayed response performance in Parkinson disease

Studies suggest motor deficit asymmetry may help predict the pattern of cognitive impairment in individuals with Parkinson disease (PD). We tested this hypothesis using a highly validated and sensitive spatial memory task, spatial delayed response (SDR), and clinical and neuroimaging measures of PD asymmetry. We predicted SDR performance would be more impaired by PD-related changes in the right side of the brain than in the left. PD (n=35) and control (n=28) participants performed the SDR task. PD participants either had worse motor deficits on the right (RPD) or left (LPD) side of the body. Some participants also had magnetic resonance imaging for measurement of their substantia nigra (SN) volumes. The LPD group performed worse on the SDR task than the RPD and control groups. Right SN volume accounted for a unique and significant portion of the variance in SDR error, with smaller volume predicting poorer performance. In conclusion, left motor dysfunction and smaller right SN volume are associated with poorer spatial memory.