Responsiveness of impairments and disabilities in Parkinson's disease

Functional Connectivity Changes of Key Regions for Motor Initiation in Parkinson's Disease

Akinesia, a cardinal symptom of Parkinson's disease, has been linked to abnormal activation in putamen and posterior medial frontal cortex (pMFC). However, little is known whether clinical severity of akinesia is linked to dysfunctional connectivity of these regions. Using a seed-based approach, we here investigated resting-state functional connectivity (RSFC) of putamen, pMFC and primary motor cortex (M1) in 60 patients with Parkinson's disease on regular medication and 72 healthy controls. We found that in patients putamen featured decreases of connectivity for a number of cortical and subcortical areas engaged in sensorimotor and cognitive processing. In contrast, the pMFC showed reduced connectivity with a more focal cortical network involved in higher-level motor-cognition. Finally, M1 featured a selective disruption of connectivity in a network specifically connected with M1. Correlating clinical impairment with connectivity changes revealed a relationship between akinesia and reduced RSFC between pMFC and left intraparietal lobule (IPL). Together, the present study demonstrated RSFC decreases in networks for motor initiation and execution in Parkinson's disease. Moreover, results suggest a relationship between pMFC-IPL decoupling and the manifestation of akinetic symptoms.

Efficacy of Rotigotine at Different Stages of Parkinson's Disease Symptom Severity and Disability: A Post Hoc Analysis According to Baseline Hoehn and Yahr Stage

Background: The efficacy of rotigotine has been demonstrated in studies of patients with early (i.e. not receiving levodopa) and advanced (i.e. not adequately controlled on levodopa; average 2.5 h/day in ‘off’ state) Parkinson’s disease (PD).

Objective: To further investigate the efficacy of rotigotine transdermal patch across different stages of PD symptom severity and functional disability, according to baseline Hoehn and Yahr (HY) staging.

Methods:Post hoc analysis of six placebo-controlled studies of rotigotine in patients with early PD (SP506, SP512, SP513; rotigotine ≤8 mg/24 h) or advanced-PD (CLEOPATRA-PD, PREFER, SP921; rotigotine ≤16 mg/24 h). Data were pooled and analyzed according to baseline HY stage (1, 2, 3 or 4) for change from baseline to end of maintenance in Unified Parkinson’s Disease Rating Scale (UPDRS) II (activities of daily living), UPDRS III (motor) and UPDRS II+III; statistical tests are exploratory.

Results: Data were available for 2057 patients (HY 1 : 262; HY 2 : 1230; HY 3 : 524; HY 4 : 41). Patients at higher HY stages were older, had a longer time since PD diagnosis and higher baseline UPDRS II+III scores vs patients at lower HY stages. Rotigotine improved UPDRS II+III versus placebo for each individual HY stage (p < 0.05 for each HY stage), with treatment differences increasing with increasing HY stages. Similar results were observed for UPDRS II and UPDRS III.

Conclusions: This post hoc analysis suggests that rotigotine may be efficacious across a broad range of progressive stages of PD symptom severity and functional disability (HY stages 1–4).

Use of a self-rating scale of the nature and severity of symptoms in Parkinson's Disease (PRO-PD): Correlation with quality of life and existing scales of disease severity

A self-rating scale was developed to permit patient-reported, remote assessment of Parkinson's disease symptom severity. The goal was to create a continuous outcome measure that does not require a clinical exam, does not fluctuate in response to dopaminergic medications, takes only a few minutes to complete, allows for stratification by symptom(s), and captures both motor and non-motor Parkinson's disease symptoms, major contributors to quality of life. The Patient Reported Outcomes in Parkinson's Disease (PRO-PD) is the cumulative score of 32 slider bars, each evaluating a common Parkinson's disease symptom. The PRO-PD has been used as an outcome measure in three studies. The baseline data from each of these studies were pooled for this analysis. Symptom frequency and severity are described, as well as correlation coefficients with existing measures of Parkinson's disease severity. Data on 1031 participants with Parkinson's disease were available for analysis. Fatigue, impaired handwriting, daytime sleepiness, slowness, tremor, muscle cramps, and forgetfulness were the most frequently reported symptoms. Persons with a relatively long duration of Parkinson's disease tended to report more, and more severe, symptoms. The PRO-PD was most highly correlated with the Parkinson's Disease Questionaire-39 (r  =  0.763, P  <  0.000) and Patient-Reported Outcome Measurement Information System Global quality of life (r  =  -0.7293, P  <  0.000), other patient-reported quality of life measures. The PRO-PDnon-motor subset was highly correlated with the Non-Motor Symptom Score (r  =  0.7533, P  <  0.000). There was a moderate correlation seen with Hoehn & Yahr (r  =  0.5922, P  <  0.000), total Unified Parkinson's disease Rating Scale (r  =  0.4724, P  <  0.000), and the Timed-Up-&-Go (r  =  0.4709, P  <  0.000). The PRO-PD may have utility for patients, providers, and researchers as a patient-centered measure of Parkinson's disease symptom severity. Further PRO-PD validation efforts are warranted.

Evaluation of the controlled grip force exertion tasks associated with age, gender, handedness and target force level

INTRODUCTION

Force control of the hand is an essential factor for operating tools and moving objects. Therefore, a method for quantifying hand functionality more accurately and objectively is very important.

METHODS

The present study included 60 healthy participants (30 elderly and 30 young adults) to evaluate the effects of age, gender and target force levels on tracking performance. Tracking performance was quantified by measuring the difference between target force levels and exerted force.

RESULTS

Females exerted 59.6% of the maximum grip strength of males and the elderly group exerted 70.5% of maximum grip strength compared with the young group. The elderly group showed 3.1 times larger tracking error than the young group. There was a significant difference in females between the young and elderly groups, indicating age-related decline in hand function is more pronounced in females. The difference in grip force control ability between the elderly and young groups was significant at the low target force level (5% maximum voluntary contraction).

CONCLUSIONS

The results of this study could be used for hand function evaluation guidelines. In addition, this study could be used as a tool for physiotherapy to improve hand function and prevent its decline in elderly people.

Postural instability in Parkinson Disease: to step or not to step

Postural instability is a key feature of Parkinson Disease that is associated with falls and morbidity. We designed a pull apparatus to quantitatively measure the force needed to pull subjects off-balance. Thirteen Controls and eight individuals with Parkinson Disease (PD) were evaluated. All individuals with PD reported subjective symptoms of postural instability and were symptomatic for approximately 9.4years when tested. No significant differences were found between Controls and PD subjects in the magnitude of force required to pull them off-balance. None of the Controls fell and all took a step into the direction of pull to maintain their balance. 59% of the time PD subjects fell because they did not take a step in the direction of pull to maintain their center of mass (COM) over their feet, thus indicating a deficiency in postural reflexes. If they fell on the first pull, PD subjects did not show a learning effect when pulled multiple times in the same direction. The utility of the Pull Test to detect postural instability is related to the subject's behavioral response, not the force needed to pull them off balance. Our findings may also help explain certain features of the PD gait as an attempt by subjects to avoid postural instability by not placing their COM in gravitationally unstable positions.

Action tremor in Parkinson's disease: frequency and relationship to motor and non-motor signs

BACKGROUND AND PURPOSE

Action tremor may occur in patients with Parkinson's disease and cause misdiagnosis with other movement disorders such as essential tremor and dystonia. Data on the frequency of action tremor in Parkinson's disease and on the relationships with other motor and non-motor signs are limited.

METHODS

A cross-sectional study of 237 patients with Parkinson's disease staging 1-2 on the Hoehn-Yahr scale was conducted. Data on action tremor and other motor and non-motor signs were collected using the Unified Parkinson's Disease Rating Scale part III and the Non-Motor Symptoms Scale.

RESULTS

Action tremor was found in 46% of patients and was associated with both severity of rest tremor (adjusted odds ratio 3.0, P < 0.001) and severity of rigidity (adjusted odds ratio 1.5, P = 0.004). No association was found between action tremor and severity of bradykinesia (adjusted odds ratio 0.97, P = 0.4) or axial symptoms (adjusted odds ratio 0.9, P = 0.3). Moreover, patients who had action tremor reported a significant lower mean number of non-motor symptoms than those who had not (2.1 ± 1.3 vs. 2.4 ± 1.3; P = 0.04).

CONCLUSIONS

Action tremor is a relatively frequent motor sign in patients with Parkinson's disease staging 1-2 on the Hoehn-Yahr scale. Action tremor correlates with rest tremor and rigidity and may be associated with a lower burden of non-motor symptoms. These findings suggest a contribution of non-dopaminergic mechanisms to action tremor pathophysiology.

Potential reliability and validity of a modified version of the Unified Parkinson's Disease Rating Scale that could be administered remotely

BACKGROUND

By permitting remote assessments of patients and research participants, telemedicine has the potential to reshape clinical care and clinical trials for Parkinson disease. While the majority of the motor Unified Parkinson's Disease Rating Scale (UPDRS) items can be conducted visually, rigidity and retropulsion pull testing require hands-on assessment by the rater and are less feasible to perform remotely in patients' homes.

METHODS

In a secondary data analysis of the Comparison of the Agonist pramipexole vs. Levodopa on Motor complications in Parkinson's Disease (CALM-PD) study, a randomized clinical trial, we assessed the cross-sectional (baseline and 2 years) and longitudinal (change from baseline to 2 years) reliability of a modified motor UPDRS (removing rigidity and retropulsion items) compared to the standard motor UPDRS (all items) using intraclass correlation coefficients (ICC), stratified by treatment group. Internal consistency of the modified UPDRS (mUPDRS) was measured using Cronbach's alpha, and concurrent validity was assessed using Pearson's correlation coefficient (r) between the standard motor UPDRS and mUPDRS.

RESULTS

The mUPDRS versus standard motor UPDRS is cross-sectionally (ICC ≥ 0.92) and longitudinally (ICC ≥ 0.92) reliable for both treatment groups. High internal consistencies were also observed (α ≥ 0.96). The mUPDRS had high concurrent validity with the standard UPDRS at both time points and longitudinally (r ≥ 0.93, p < 0.0001).

CONCLUSIONS

A modified version of the motor UPDRS without rigidity and retropulsion pull testing is reliable and valid and may lay the foundation for its use in remote assessments of patients and research participants.

Use of sensitive devices to assess the effect of medication on attentional demands of precision and power grips in individuals with Parkinson disease

Deficits in fine motor control are a common early symptom in people with Parkinson disease (PD) and may serve as an ideal marker for the response to therapeutic interventions and progression of the disease. The long-term goal of this research is to develop sensitive clinical markers that can be used to accurately assess disease progression and the response to therapeutic interventions. The purpose of this preliminary study was to examine the effects of medication on the attentional demands of precision (Pre) and power (Pow) grips in individuals with PD. In order to assess force control during precision and power grip, we used an instrumented twist-cap device. Performance on the motor task was quantified using peak force levels (PF) and the time to reach peak force (TTP). To assess attentional demands of the motor task, participants performed an auditory analog of the Stroop test while performing the motor task. Dual-task cost (DTC) for all outcome variables was calculated. Dual-task cost for response latency (RL DTC) for both grips were greater (P < 0.005) when participants were on medications('ONMeds'). Mean [95%CI]: Pre = 25.7[14.7-36.7], Pow = 37.08[26.5-47.7]) compared with off medications('OFFMeds') (Pre = 12.6[1.5-23.6], Pow = 10.98[0.4-21.6]), suggesting that force control during both grip tasks may remain attentionally demanding even on medications.

Plasma selenium is positively related to performance in neurological tasks assessing coordination and motor speed

Parkinson's disease (PD) is a degenerative process affecting the striato nigral system (SN). Its etiology, although obscure, may involve oxidative damage. Selenium, an antioxidant, was shown to protect the SN in animal models. In the current study, we investigate the association between plasma selenium concentrations and the presence of "soft" neurological signs related to the SN. Plasma selenium concentration was assessed in participants of age ≥65 years in the InCHIANTI study, a population-based cohort study in Tuscany, Italy. PD was defined based on standard criteria. "Soft" neurological signs were ascertained by physical examination. A total of 1,012 participants were included. No association was found between the presence of PD and plasma selenium. There was, however, a strong association between plasma selenium and timed performance-based assessments. Lower levels of selenium were significantly associated withdecreased performance in neurological tests of coordination among older adults. Prospective studies are needed to further investigate the effects of selenium on SN dysfunction.

Assessment of fine motor control in individuals with Parkinson's disease using force tracking with a secondary cognitive task

BACKGROUND AND PURPOSE

Motor symptoms of Parkinson's disease (PD) are typically assessed using clinical scales such as the Unified Parkinson's Disease Rating Scale, but clinical scales are insensitive to subtle changes early in the disease process. The goal of this project was to use current sensing technology to develop a quantitative assessment tool to document fine motor deficits in PD based on the ability to control grip force output. The assessment was designed to challenge deficits commonly encountered as a result of PD, including dual-task performance of a motor task and a cognitive task simultaneously.

METHODS

Two force sensors were used to measure the isometric pinch grip force between the thumb and index finger in 30 individuals with PD and 30 control participants of similar age without disability. Participants performed a target force tracking task with each of two different target waveforms (sinusoidal or pseudorandom) under each of three different cognitive load conditions (none, subtract 1, and subtract 3). Dependent variables calculated from the force sensor data included root mean square error, tremor integral, and lag.

RESULTS

In general, individuals with PD showed significantly less accuracy in generating the target forces as shown by larger root mean square error compared with controls (P < 0.001). They also showed greater amounts of tremor and lag compared with controls (P = 0.001 and <0.001, respectively). Deficits were more pronounced during the cognitive multitasking component of the test.

DISCUSSION AND CONCLUSIONS

These results will serve as a preliminary work for the development of a clinical biomarker for PD that may help to identify subtle deficits in fine motor control early in the disease process and facilitate tracking of disease progression with time.

Motor patterns in Parkinson's disease: a data-driven approach

To identify patterns of motor disturbances in Parkinson's disease (PD) and evaluate their relation with other PD domains. A cohort of 399 PD patients was randomly divided into two samples. Factors within the motor section of the SPES/SCOPA were identified by exploratory factor analysis on data from the first sample and next tested by confirmatory factor analysis in the second sample. Relations with other PD domains were evaluated by regression analyses. A four factor model was found to be valid. This included a tremor, a bradykinetic-rigid, and two axial factors. One axial factor ("rise", "gait", "postural instability") was associated with age and cognition, while the other axial factor ("freezing", "speech", "swallowing") was related to dopaminergic medication and complications of therapy. Both other factors showed no relevant associations with demographic and clinical characteristics. The identification of motor factors and their relation with other domains of the disease may help to elucidate the mechanisms responsible for these associations and provide an objective base for further research on subtypes in PD.

Effects of dopamine D1 and D2 receptor antagonists on laryngeal neurophysiology in the rat

Hypophonia is an early symptom in Parkinson's disease (PD) that involves an increase in laryngeal muscle activity, interfering with voice production. Our aim was to use an animal model to better understand the role of different dopamine receptor subtypes in the control of laryngeal neurophysiology. First, we evaluated the combined effects of SCH23390-a D(1) receptor antagonist with a D(2) receptor antagonist (eticlopride) on laryngeal neurophysiology, and then tested the separate effects of selective receptor antagonists. Thyroarytenoid (TA) and gastrocnemius (GN) muscle activity was measured at rest and while stimulating the internal branch of superior laryngeal nerve to elicit the laryngeal adductor response (LAR) in alpha-chloralose-anesthetized rats. Paired stimuli at different interstimulus intervals between 250 and 5,000 ms measured central conditioning of the LAR. Changes in resting muscle activity, response latency, amplitude, and LAR conditioning after each drug were compared with the saline control. SCH23390 alone increased the resting TA muscle activity (P < 0.05). With the combined SCH23390 + eticlopride or SCH23390 alone, response latency decreased (P < 0.01), amplitude increased (P < 0.01), and the test LAR was reduced at 2,000-ms ISI (P < 0.01). No LAR changes occurred when eticlopride was administered alone at a low dose and only a tendency to suppress responses was found at a high dose. No changes in GN muscle activity occurred in any of the groups. The results suggest that a loss of stimulation of D(1) receptors plays a significant role in laryngeal pathophysiology in PD.

Functional balance performance in patients with Parkinson's disease after long-term treatment with subthalamic nucleus high-frequency stimulation

The aim was to investigate if functional balance performance in patients with Parkinson's disease (PD) was affected by long-term (3 years) treatment with bilateral subthalamic nucleus (STN) high-frequency stimulation. Thirty-five patients were consecutively included, and 28 patients completed the study (mean age 62 years, SD 6.5). The Berg Balance Scale (BBS) was assessed preoperatively and 1 and 3 years postoperatively (with and without anti-PD medication and with the STN stimulation turned OFF or ON). Although the balance performance of patients with PD decreased over time, the functional balance performance was still positively affected by STN stimulation alone 3 years after surgery.

Surgery for Parkinson's disease improves disability but not impairment components of the UPDRS-II

The Unified Parkinson's Disease Rating Scale (UPDRS) activities of daily living (ADL) items have been described as reflecting both disability (true ADL items) and impairment (rather than ADLs). As a result of combining these scores, UPDRS part II scores may not accurately reflect the impact of surgery on ADLs [Hariz G.M., Lindberg M., Hariz M.I., Bergenheim A.T. Does the ADL part of the unified Parkinson's disease rating scale measure ADL? An evaluation in patients after pallidotomy and thalamic deep brain stimulation. Mov Disord 2003;18:373-81.]. The goal of the present study was to assess the metric properties of the ADL section of the UPDRS in terms of its ability to measure surgical change. We tested the effects of unilateral pallidotomy (N=14) and bilateral subthalamic nucleus (STN) DBS (N=11) on both disability and impairment components of the UPDRS-II at uniform follow-up assessment periods of 6 months and 1 year, with a subset of pallidotomy patients (N=9) re-assessed at 2 years. Across the follow-up periods in both patient groups, items identified as best reflecting disability showed significant improvement from pre-surgical levels, whereas items representing impairment showed no overall change. Consistent with this, change in total ADL scores was tempered by the inclusion of the impairment items. Because the measurement of a patient's functional status is important in determining the effectiveness of an intervention, analysis of appropriate items from the UPDRS ADL section is imperative.