Bimanual coordination dysfunction in early, untreated Parkinson's disease

Motor cortex activation mediates associations between striatal dopamine depletion and manual dexterity in Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) presents with a progressive decline in manual dexterity, attributed to dysfunction in the basal ganglia-thalamus-cortex loop, influenced by dopaminergic deficits in the striatum. Recent research suggests that the motor cortex may play a pivotal role in mediating the relationship between striatal dopamine depletion and motor function in PD. Understanding this connection is crucial for comprehending the origins of manual dexterity impairments in PD. Therefore, our study aimed to explore how motor cortex activation mediates the association between striatal dopamine depletion and manual dexterity in PD.

MATERIALS AND METHODS

We enrolled 26 mildly affected PD patients in their off-medication phase to undergo [18F]FDOPA PET/CT scans for evaluating striatal dopaminergic function. EEG recordings were conducted during bimanual anti-phase finger tapping tasks to evaluate motor cortex activity, specifically focusing on Event-Related Desynchronization in the beta band. Manual dexterity was assessed using the Purdue Pegboard Test. Regression-based mediation analysis was conducted to examine whether motor cortex activation mediates the association between striatal dopamine depletion and manual dexterity in PD.

RESULTS

Mediation analysis revealed a significant direct effect of putamen dopamine depletion on manual dexterity for the affected hand and assembly tasks (performed with two hands), with motor cortex activity mediating this association. In contrast, while caudate nucleus dopamine depletion showed a significant direct effect on manual dexterity, motor cortex mediation on this association was not observed.

CONCLUSION

Our study confirms the association between striatum dopamine depletion and impaired manual dexterity in PD, with motor cortex activity mediating this relationship.

Investigating the efficacy and importance of mobile-based assessments for Parkinson's disease: uncovering the potential of novel digital tests

This study introduces PDMotion, a mobile application comprising 11 digital tests, including those adapted from the MDS-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III and novel assessments, for remote Parkinson's Disease (PD) motor symptoms evaluation. Employing machine learning techniques on data from 50 PD patients and 29 healthy controls, PDMotion achieves accuracies of 0.878 for PD status prediction and 0.715 for severity assessment. A post-hoc explanation model is employed to assess the importance of features and tasks in diagnosis and severity evaluation. Notably, novel tasks that are not adapted from MDS-UPDRS Part III like the circle drawing, coordination test, and alternative tapping test are found to be highly important, suggesting digital assessments for PD can go beyond digitizing existing tests. The alternative tapping test emerges as the most significant task. Using its features alone achieves prediction accuracies comparable to the full task set, underscoring its potential as an independent screening tool. This study addresses a notable research gap by digitalizing a wide array of tests, including novel ones, and conducting a comparative analysis of their feature and task importance. These insights provide guidance for task selection and future development in PD mobile assessments, a field previously lacking such comparative studies.

Microstructural alterations predict impaired bimanual control in Parkinson’s disease

Bimanual coordination is impaired in Parkinson’s disease affecting patients’ ability to perform activities of daily living and to maintain independence. Conveyance of information between cortical and subcortical areas is essential for bimanual coordination and relies on the integrity of cerebral microstructure. As pathological deposition of alpha-synuclein compromises microstructure in Parkinson’s disease, we investigated the relationship between microstructural integrity and bimanual coordination using diffusion-weighted MRI in 23 patients with Parkinson’s disease (mean age ± standard deviation: 56.0 ± 6.45 years; 8 female) and 26 older adults (mean age ± standard deviation: 58.5 ± 5.52 years). Whole-brain analysis revealed specific microstructural alterations between patients and healthy controls matched for age, sex, handedness, and cognitive status congruent with the literature and known Parkinson’s disease pathology. A general linear model revealed distinct microstructural alterations associated with poor bimanual coordination in Parkinson’s disease, corrected for multiple comparisons using a permutation-based approach. Integrating known functional topography, we conclude that distinct changes in microstructure cause an impediment of structures involved in attention, working memory, executive function, motor planning, motor control, and visual processing contributing to impaired bimanual coordination in Parkinson’s disease.

Amplitude setting and dopamine response of finger tapping and gait are related in Parkinson's disease

Movement amplitude setting is affected early in Parkinson’s disease (PD), clinically manifesting as bradykinesia. Our objective was to determine if amplitude setting of upper limb bimanual movements and bipedal gait are similarly modulated in PD. 27 PD and 24 control participants were enrolled. Participants performed a bimanual anti-phase finger tapping task wearing gloves with joint angular sensors, and an instrumented gait assessment. Participants performed normal and fast paced assessments to vary motor load. PD participants were evaluated OFF (PD-OFF) and ON (PD-ON) levodopa. PD-OFF participants had smaller tap amplitude, and greater tap amplitude variability than controls in the more affected hands (all p < 0.05). Tap amplitude and stride length (p = 0.030) were correlated in PD-OFF. Tap amplitude was also correlated with motor UPDRS (p < 0.005) and bradykinesia motor (p < 0.05) and ADL (p < 0.005) UPDRS subscores. The relative amount of improvement in tap amplitude and stride length with levodopa was correlated. In PD, upper limb and gait amplitude setting are similarly scaled with motor demand and dopamine supplementation. This suggests these automated motor functions are subserved by common functional networks.

Forensic examination of effects of Parkinsonism on various handwriting characteristics

Parkinsonism is a neurodegenerative syndrome that causes impairment of motor skills in affected persons. Thus, adverse effects may be produced in the handwriting of persons suffering from Parkinsonism. Medication used for the treatment of Parkinsonism is known to subside certain motor defects for specific time intervals, showing slight differences or improvement in certain handwriting characteristics during those intervals on the same day as compared to the ones executed before medication. Certain handwriting characteristics affected due to Parkinsonism may be mistaken as forged features due to poor line quality, which can cause suspicion upon the authenticity of important legal documents. The present research work has been carried out to determine the effects of Parkinsonism and medication used for its treatment on handwriting. Handwriting/signature samples executed before and after the onset of Parkinsonism (both pre- and post-medication) have been randomly collected from 70 participants. These handwritings have been evaluated separately and compared inter-se for various handwriting characteristics with qualitative and statistical approach. The results have demonstrated significant changes in most of the characteristics in both affected writings of majority of participants as compared to their corresponding earlier writings. Thus, forensic document experts should be aware of the detrimental effects of Parkinsonism on handwriting in pre- and post-medication conditions of this ailment.

Effect of External Feedback on Bimanual Coordination Control in Patients with Parkinson's Disease

Bimanual coordination control requires task-specific control of the spatial and temporal characteristics of the coupling of both upper limbs. The present study examined the effects of external feedback (i.e., auditory signal) on bimanual coordination movement during patients with Parkinson’s disease (PD). Twelve PD patients in advanced stages and 12 early stages of untreated PD patients, and 12 age-matched normal adults were instructed to perform bimanual coordination control using preference (1 Hz) and fast (1.75 Hz) speeds with metronome auditory cue. The results demonstrated that the advanced PD patients showed reduced synchronized bimanual coordination control during the anti-phase movement compared with other two groups. Moreover, the decreased movement accuracy was exhibited not only at the preference speed, but also more particularly at the fast speed with anti-phase rather than in-phase movement. This suggests that PD results in impairments in scaling the bimanual movement speed and amplitude of limb, and these deficits were more pronounced as a function of movement control speed. Overall, the current data provide evidence of the pathophysiology of the basal ganglia on the bimanual coordination movement.

Quantifying upper limb motor impairment in people with Parkinson's disease: a physiological profiling approach

BACKGROUND

Upper limb motor impairments, such as slowness of movement and difficulties executing sequential tasks, are common in people with Parkinson's disease (PD).

OBJECTIVE

To evaluate the validity of the upper limb Physiological Profile Assessment (PPA) as a standard clinical assessment battery in people with PD, by determining whether the tests, which encompass muscle strength, dexterity, arm stability, position sense, skin sensation and bimanual coordination can (a) distinguish people with PD from healthy controls, (b) detect differences in upper limb test domains between "off" and "on" anti-Parkinson medication states and (c) correlate with a validated measure of upper limb function.

METHODS

Thirty-four participants with PD and 68 healthy controls completed the upper limb PPA tests within a single session.

RESULTS

People with PD exhibited impaired performance across most test domains. Based on validity, reliability and feasibility, six tests (handgrip strength, finger-press reaction time, 9-hole peg test, bimanual pole test, arm stability, and shirt buttoning) were identified as key tests for the assessment of upper limb function in people with PD.

CONCLUSIONS

The upper limb PPA provides a valid, quick and simple means of quantifying specific upper limb impairments in people with PD. These findings indicate clinical assessments should prioritise tests of muscle strength, unilateral movement and dexterity, bimanual coordination, arm stability and functional tasks in people with PD as these domains are the most commonly and significantly impaired.

Non-invasive Transcranial Electrical Stimulation in Movement Disorders

Dysfunction within large-scale brain networks as the basis for movement disorders is an accepted hypothesis. The treatment options for restoring network function are limited. Non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation are now being studied to modify the network. Transcranial electrical stimulation (tES) is also a portable, cost-effective, and non-invasive way of network modulation. Transcranial direct current stimulation and transcranial alternating current stimulation have been studied in Parkinson’s disease, dystonia, tremor, and ataxia. Transcranial pulsed current stimulation and transcranial random noise stimulation are not yet studied enough. The literature in the use of these techniques is intriguing, yet many unanswered questions remain. In this review, we highlight the studies using these four potential tES techniques and their electrophysiological basis and consider the therapeutic implication in the field of movement disorders. The objectives are to consolidate the current literature, demonstrate that these methods are feasible, and encourage the application of such techniques in the near future.

The effect of transcranial direct current stimulation on upper limb motor performance in Parkinson's disease: a systematic review

BACKGROUND AND PURPOSE

Parkinson's disease (PD) reduces independence and quality of life through deterioration of upper limb motor function. Transcranial direct current stimulation (tDCS) may offer an alternative, adjunctive therapy for PD. However, the efficacy of tDCS for upper limb motor rehabilitation in PD is unknown. In this systematic review, evidence is compiled regarding the effects of tDCS on upper limb motor function in PD.

METHODS

Studies of tDCS applied to PD patients that assessed upper limb motor function, conducted between January 2000 and November 2018, were screened for inclusion via a systematic search of Medline, Cochrane, PsycINFO, EMBASE, CINAHL, and Web of Science.

RESULTS

Ten out of 606 studies were included and their findings synthesized into five categories regarding the effects of tDCS on: (1) Unified Parkinson's Disease Rating Scale motor section (UPDRS III), (2) upper limb motor tasks, (3) manual dexterity, (4) reaction time, and (5) neurophysiology.

CONCLUSIONS

When applied to the primary motor cortex, tDCS may improve UPDRS III and the speed and force of movement. Considerable variation was found in tDCS parameters and further study is needed to clarify the long-term effects of tDCS on both simple and complex motor tasks and to compile relevant neurophysiological evidence.

Eight Weeks of Aerobic Interval Training Improves Psychomotor Function in Patients with Parkinson's Disease-Randomized Controlled Trial

Background: This study examined the generalized effects of cycle ergometer aerobic interval training (AIT) on psychomotor behaviors in individuals with Parkinson’s disease (PD), including bimanual motor control, cognitive function, and neurological motor and non-motor parkinsonian signs. Methods: Twenty mild to moderate PD patients were randomly allocated to the following groups: (1) trained group (PD-TR, n = 10), which besides receiving usual care, underwent an 8-week moderate intensity AIT program; or (2) control group (PD-CO, n = 10) which received usual care, including participation in conventional physical therapy. Both groups were tested before and after the 8-week AIT program period with the following assessments: (1) laboratory analyses of bimanual motor control, (2) psychological evaluation of cognitive function, and (3) an evaluation of neurological parkinsonian signs. Results: The PD-TR group exhibited improved (1) bimanual motor control, reflected by a decreased time (p = 0.013) and increased rate of grip force development (p = 0.013) in the manipulating hand and a decreased time delay between grip force initiation in the manipulating and stabilizing hand (p = 0.020); (2) executive function, reflected by decreased performance time in part II of the Stroop Test (p = 0.007); and (3) neurological parkinsonian signs, reflected by an amelioration of upper-extremity bradykinesia (p = 0.015) and improvement in daily life manual functions (p = 0.004), mood, and intellectual function (p = 0.005). Conclusions: Following an 8-week moderate intensity AIT program, patients with PD exhibited improved psychomotor behaviors, reflected by bimanual motor control, executive function, and neurological parkinsonian signs.

Kinematic analysis of bimanual movements during food handling by head-fixed rats

Bimanual coordination, in which both hands work together to achieve a goal, is crucial for the basic needs of life, such as gathering and feeding. Such coordinated motor skill is highly developed in primates, where it has been most extensively studied. Rodents also exhibit remarkable dexterity and coordination of forelimbs during food handling and consumption. However, rodents have been less commonly used in the study of bimanual coordination because of limited quantitative measuring techniques. In this article we describe a high-resolution tracking system that enables kinematic analysis of rat forelimb movement. The system is used to quantify forelimb movements bilaterally in head-fixed rats during food handling and consumption. Forelimb movements occurring naturally during feeding were encoded as continuous three-dimensional trajectories. The trajectories were then automatically segmented and analyzed, using a novel algorithm, according to the laterality of movement speed or the asymmetry of movement direction across the forelimbs. Bilateral forelimb movements were frequently observed during spontaneous food handling. Both symmetry and asymmetry in movement direction were frequently observed, with symmetric bilateral movements quantitatively more common. The proposed method overcomes a limitation in the precise quantification of bimanual coordination in rodents. This enables the use of powerful rodent-based research tools such as optogenetics and chemogenetics in the further investigation of neural mechanisms of bimanual coordination. NEW & NOTEWORTHY We describe a new method for quantifying and classifying three-dimensional, bilateral forelimb trajectories in head-fixed rats. The method overcomes limits on quantifying bimanual coordination in rats. When applied to kinematic analysis of food handling behavior, continuous forelimb trajectories were automatically segmented and classified. Bilateral forelimb movements were observed more frequently than unilateral movements during spontaneous food handling. Both symmetry and asymmetry in movement direction were frequently observed. However, symmetric bilateral forelimb movements were more common.

Subthalamic Neurons Encode Both Single- and Multi-Limb Movements in Parkinson's Disease Patients

The subthalamic nucleus (STN) is the main target for neurosurgical treatment of motor signs of Parkinson’s disease (PD). Despite the therapeutic effect on both upper and lower extremities, its role in motor control and coordination and its changes in Parkinson’s disease are not fully clear. We intraoperatively recorded single unit activity in ten patients with PD who performed repetitive feet or hand movements while undergoing implantation of a deep brain stimulator. We found both distinct and overlapping representations of upper and lower extremity movement kinematics in subthalamic units and observed evidence for re-routing to a multi-limb representation that participates in limb coordination. The well-known subthalamic somatotopy showed a large overlap of feet and hand representations in the PD patients. This overlap and excessive amounts of kinematics or coordination units may reflect pathophysiology or compensatory mechanisms. Our findings thus explain, at the single neuron level, the important subthalamic role in motor control and coordination and indicate the effect of PD on the neuronal representation of movement.

"Test D'évaluation Des Membres Supérieurs Des Personnes Âgées" (TEMPA) to assess upper limb activity in Parkinson's disease

STUDY DESIGN

Cross-sectional and observational study.

PURPOSE OF THE STUDY

Assess upper limb (UL) activity limitations using the "Test d'Evaluation des Membres Supérieurs Des Personnes Agées" (TEMPA) in individuals with Parkinson's disease (PD) and verify its clinimetrics properties.

METHODS

The following were evaluated: internal consistency, interrater and test-retest reliability; concurrent validity; convergent validity; know group's validity; minimal detectable change, floor and ceiling effects, and the relationship between UL activity limitations and the presence of freezing of gait.

RESULTS

Excellent reliability and interrater agreement (intraclass correlation coefficient = 0.99 and κ = 0.92) and test-retest reliability (intraclass correlation coefficient = 0.97) were found, as well internal consistency (α = 0.99). A moderate negative correlation was found between TEMPA and section II of the Unified Parkinson's Disease Rating Scale (ρ = -0.58; P = .001), and moderate/low between the test and the Nine Hole Peg Test values of the right UL and moderate for left UL (ρ = 0.56 and ρ = 0.41; P = .001) (ρ = 0.52 and ρ = 0.51; P = .001 and P = .002), respectively. No significant relationship was found with freezing episodes (P = .057).

DISCUSSION

TEMPA is useful for assessing UL activity limitations in PD, have adequate clinimetrics properties and is capable of detecting the influence of motor symptoms during the carrying out of daily living tasks. No differences were found between freezers and no freezers.

LEVEL OF EVIDENCE

N/A.

Does response inhibition have pre- and postdiagnostic utility in Parkinson's disease?

Parkinson's disease (Pd) is the second most prevalent degenerative neurological condition worldwide. Improving and sustaining quality of life is an important goal for Parkinson's patients. Key areas of focus to achieve this goal include earlier diagnosis and individualized treatment. In this review the authors discuss impulse control in Pd and examine how measures of impulse control from a response inhibition task may provide clinically useful information (a) within an objective test battery to aid earlier diagnosis of Pd and (b) in postdiagnostic Pd, to better identify individuals at risk of developing impulse control disorders with dopaminergic medication.

Distal motor deficit contributions to postural instability and gait disorder in Parkinson's disease

Clinical subtypes in Parkinson's disease (PD) are often based on the presence of clustered motor symptoms. In contrast to the tremor dominant (TD) subtype, the postural instability and gait disorder (PIGD) subtype is characterized by predominantly axial motor involvement and increased cognitive impairment. It is, however, unclear if subtypes represent distinct underlying neuropathological mechanisms or reflect more severe disease progression. We aimed to clarify the validity of PD subtypes by investigating behavioral outcomes at multiple levels. Therefore, spatiotemporal kinematics of gait, upper and lower limb repetitive movements in combination with a balance and cognitive assessment were recorded in 73 patients with PD. We classified patients as PIGD (n=43), TD (n=22) or indeterminate (n=8) while 'off' medication and recruited 20 age-matched controls. Surprisingly, differences between PIGD and TD were more prominent during repetitive distal motor tasks than during gait. Gait impairment in PIGD was only shown by reduced step length and gait speed. However, motor scaling and coordination of distal movements were more affected in PIGD than in TD patients. PIGD patients also had impaired postural control compared to TD patients as shown by lower mini-BESTest scores. There were no cognitive differences between patient subgroups. Distal movement was not significantly different in TD patients from controls, except for greater movement asymmetry. The results indicate a widespread impairment within PIGD with more pronounced distal than axial motor deficits. This suggests involvement of different neurotransmitter systems in the neuropathology of PD subtypes, which are at least partially independent of disease progression.

Inter-limb coupling during diadochokinesis in Parkinson's and Huntington's disease

Patients with neurodegenerative diseases often exhibit deficits in bimanual coordination. One characteristic of bimanual movements is inter-limb coupling. It is the property of motor performance harmonization between hands during a bimanual task. The objective of this study was to identify whether spatial and temporal inter-limb coupling occurred in Parkinson's disease (PD) and Huntington's disease (HD) patients. Twenty-three PD patients and 15 healthy controls were tested. Data from 12 choreic HD patients were also taken from a databank. Participants were asked to perform a unimanual and bimanual rapid repetitive diadochokinesis task. The difference between hands in mean amplitude and mean duration of cycles was computed in the unimanual and bimanual tasks for each group. Results show that healthy controls exhibited temporal and spatial inter-limb coupling during the bimanual diadochokinesis task. Conversely, PD and HD patients exhibited temporal inter-limb coupling; but failed to exhibit spatial inter-limb coupling during the bimanual diadochokinesis task. Furthermore, HD patients exhibited reduced levels of structural coupling compared to controls and PD patients. These results suggest that alterations in basal ganglia-thalamo-cortical networks due to PD and HD do not affect temporal inter-limb coupling. However, common pathophysiological changes related to PD and HD may cause altered spatial inter-limb coupling during a rapid repetitive bimanual diadochokinesis task.

Insights from the supplementary motor area syndrome in balancing movement initiation and inhibition

The supplementary motor area (SMA) syndrome is a characteristic neurosurgical syndrome that can occur after unilateral resection of the SMA. Clinical symptoms may vary from none to a global akinesia, predominantly on the contralateral side, with preserved muscle strength and mutism. A remarkable feature is that these symptoms completely resolve within weeks to months, leaving only a disturbance in alternating bimanual movements. In this review we give an overview of the old and new insights from the SMA syndrome and extrapolate these findings to seemingly unrelated diseases and symptoms such as Parkinson's disease (PD) and tics. Furthermore, we integrate findings from lesion, stimulation and functional imaging studies to provide insight in the motor function of the SMA.

Functional specialization within the supplementary motor area: a fNIRS study of bimanual coordination

Bimanual movements can be performed by flexing and extending the target effectors (e.g., hand muscles) in unison, or by flexing units on one side in unison with extension of the same units on the opposite side. The former movement patterns are generally referred to as in-phase or parallel, whereas the latter patterns are often termed anti-phase movements. It is well known that anti-phase patterns are unstable and tend to spontaneously transition to in-phase movements at higher repetition rates, but the mechanisms and brain regions involved are not fully understood. In the current study, we utilized functional near-infrared spectroscopy (fNIRS) to evaluate whether anterior/posterior subdivisions of the supplementary motor complex (SMA) have distinct functional roles in maintaining in-phase and anti-phase movement patterns. Twelve healthy adult participants completed a bimanual coordination task comprised of anti-phase and in-phase trials as 24-channel fNIRS data was recorded from dorsal-medial motor areas. We examined the relative concentrations of oxygenated and deoxygenated hemoglobin in the channels that were located over the anterior SMA (e.g., pre-SMA) and the SMA proper. Our most interesting results indicated that oxygenated hemoglobin responses were greater in the anterior SMA during performance of anti-phase compared to in-phase movements. In the SMA proper, oxygenated hemoglobin responses did not differ between the two movement patterns. These data suggest that the anterior SMA is critical to programming and maintaining the less stable anti-phase movement patterns, and support the conceptual framework of an anterior-directed gradient of progressively more complex functionality in the SMA.

The neural correlates of upper limb motor blocks in Parkinson's disease and their relation to freezing of gait

Due to basal ganglia dysfunction, bimanual motor performance in Parkinson patients reportedly relies on compensatory brain activation in premotor-parietal-cerebellar circuitries. A subgroup of Parkinson's disease (PD) patients with freezing of gait (FOG) may exhibit greater bimanual impairments up to the point that motor blocks occur. This study investigated the neural mechanisms of upper limb motor blocks and explored their relation with FOG. Brain activation was measured using functional magnetic resonance imaging during bilateral finger movements in 16 PD with FOG, 16 without FOG (PD + FOG and PD - FOG), and 16 controls. During successful movement, PD + FOG showed decreased activation in right dorsolateral prefrontal cortex (PFC), left dorsal premotor cortex (PMd), as well as left M1 and bilaterally increased activation in dorsal putamen, pallidum, as well as subthalamic nucleus compared with PD - FOG and controls. On the contrary, upper limb motor blocks were associated with increased activation in right M1, PMd, supplementary motor area, and left PFC compared with successful movement, whereas bilateral pallidum and putamen activity was decreased. Complex striatofrontal activation changes may be involved in the difficulties of PD + FOG to perform bimanual movements, or sequential movements in general. These novel results suggest that, whatever the exact underlying cause, PD + FOG seem to have reached a saturation point of normal neural compensation and respond belatedly to actual movement breakdown.

Auditory instructional cues benefit unimanual and bimanual drawing in Parkinson's disease patients

The present study investigated performance of unimanual and bimanual anti-phase and in-phase upper limb line drawing using three different types of cues. Fifteen Parkinson's disease (PD) patients, 15 elderly, and 15 young adults drew lines away from and towards their body on a tabletop every 1000 ms for 30 s under three different cueing conditions: (1) verbal ('up', 'down'); (2) auditory (high tone, low tone); (3) visual (target line switched from top to bottom). PD patients had larger and more variable amplitudes which may be related to the finding that they also produced more curvilinear movements than young and elderly adults. Consistent with previous research, when compared to the elderly and young adult group PD patients produced a mean relative phase which deviated more from the instructed coordination modes and they showed larger variability of relative phase in bimanual coordination, especially in anti-phase conditions. For all groups, auditory and verbal cues resulted in lower coefficient of variance of cycle time, lower variability of amplitude and lower variability of relative phase than visual cues. The benefit of auditory cues may be related to the timing nature of the task or factors related to the auditory cues (e.g., reduced attentional demands, more kinesthetic focus).

Predictors of future falls in Parkinson disease

Background: Falls are a major health and injury problem for people with Parkinson disease (PD). Despite the severe consequences of falls, a major unresolved issue is the identification of factors that predict the risk of falls in individual patients with PD. The primary aim of this study was to prospectively determine an optimal combination of functional and disease-specific tests to predict falls in individuals with PD.

Methods: A total of 101 people with early-stage PD undertook a battery of neurologic and functional tests in their optimally medicated state. The tests included Tinetti, Berg, Timed Up and Go, Functional Reach, and the Physiological Profile Assessment of Falls Risk; the latter assessment includes physiologic tests of visual function, proprioception, strength, cutaneous sensitivity, reaction time, and postural sway. Falls were recorded prospectively over 6 months.

Results: Forty-eight percent of participants reported a fall and 24% more than 1 fall. In the multivariate model, a combination of the Unified Parkinson's Disease Rating Scale (UPDRS) total score, total freezing of gait score, occurrence of symptomatic postural orthostasis, Tinetti total score, and extent of postural sway in the anterior-posterior direction produced the best sensitivity (78%) and specificity (84%) for predicting falls. From the UPDRS items, only the rapid alternating task category was an independent predictor of falls. Reduced peripheral sensation and knee extension strength in fallers contributed to increased postural instability.

Conclusions: Falls are a significant problem in optimally medicated early-stage PD. A combination of both disease-specific and balance- and mobility-related measures can accurately predict falls in individuals with PD.

Neural correlates of bimanual anti-phase and in-phase movements in Parkinson's disease

Patients with Parkinson's disease have great difficulty in performing bimanual movements; this problem is more obvious when they perform bimanual anti-phase movements. The underlying mechanism of this problem remains unclear. In the current study, we used functional magnetic resonance imaging to study the bimanual coordination associated changes of brain activity and inter-regional interactions in Parkinson's disease. Subjects were asked to perform right-handed, bimanual in-phase and bimanual anti-phase movements. After practice, normal subjects performed all tasks correctly. Patients with Parkinson's disease performed in-phase movements correctly. However, some patients still made infrequent errors during anti-phase movements; they tended to revert to in-phase movement. Functional magnetic resonance imaging results showed that the supplementary motor area was more activated during anti-phase movement than in-phase movement in controls, but not in patients. In performing anti-phase movements, patients with Parkinson's disease showed less activity in the basal ganglia and supplementary motor area, and had more activation in the primary motor cortex, premotor cortex, inferior frontal gyrus, precuneus and cerebellum compared with normal subjects. The basal ganglia and dorsolateral prefrontal cortex were less connected with the supplementary motor area, whereas the primary motor cortex, parietal cortex, precuneus and cerebellum were more strongly connected with the supplementary motor area in patients with Parkinson's disease than in controls. Our findings suggest that dysfunction of the supplementary motor area and basal ganglia, abnormal interactions of brain networks and disrupted attentional networks are probably important reasons contributing to the difficulty of the patients in performing bimanual anti-phase movements. The patients require more brain activity and stronger connectivity in some brain regions to compensate for dysfunction of the supplementary motor area and basal ganglia in order to perform bimanual movements correctly.

Diagnosing premotor Parkinson's disease using a two-step approach combining olfactory testing and DAT SPECT imaging

Extranigral neuropathological changes may precede the degeneration of nigrostriatal dopaminergic neurones in Parkinson's disease (PD). Therefore, non-motor disturbances are an interesting target for the development of tests aimed at identifying individuals with premotor PD. An impaired sense of smell occurs with high prevalence in the clinical motor stages of PD patients and has also been reported in first-degree relatives of PD patients. In a prospective study in 361 asymptomatic first-degree relatives of PD patients, we studied the value of a two-step approach, combining olfactory testing and dopamine transporter (DAT) SPECT imaging, in detecting patients in the premotor phase of PD. Unexplained hyposmia alone was associated with a 12.5% risk of developing PD within a five year period. Cox regression analysis revealed that odour discrimination performance was most strongly correlated with the risk of future PD. Furthermore, all relatives that later developed PD had both hyposmia and abnormally reduced striatal DAT binding at baseline. The results of our studies provide the proof-of-principle that a two-step approach of olfactory testing and DAT SPECT imaging may serve to diagnose PD in its premotor phase. Yet, the low positive predictive value of hyposmia indicates that a wider application of this approach for screening purposes would require too many DAT SPECT scans in healthy individuals. Therefore, future studies in larger populations are necessary to further characterize premotor PD and identify additional genetic and/or clinical susceptibility markers to be used in conjunction with olfactory testing as additional screening steps toward diagnosing PD in its earliest stages.

Biased wrist and finger coordination in Parkinsonian patients during performance of graphical tasks

Handwriting impairments in Parkinson's disease (PD) have been associated with micrographia, i.e. diminished letter size. However, dyscoordination of the wrist and fingers may also contribute to handwriting deterioration in PD. To investigate this hypothesis, right-handed PD patients and controls were tested in performance of three types of cyclic wrist and finger movements: drawing of two lines and a circle. The line drawing was performed with either simultaneous flexion and extension of the wrist and fingers (equivalent pattern resulting in a right-tilted line) or with wrist flexion/extension accompanied with finger extension/flexion (nonequivalent pattern resulting in a left-tilted line). Circle drawing required a specific phase difference between wrist and finger motions. Movements were performed with an inkless pen on a digitizer-tablet at two frequency levels. Consistent deformations of the circle into right-tilted ovals and lower variability in equivalent compared with nonequivalent lines revealed preference to produce right-tilted shapes. This preference became more apparent with increased movement speed and it was amplified in PD patients. Analysis revealed that the circle deformation emerged mainly due to reduction in relative phase, while wrist and finger amplitudes remained unchanged. The results suggest that PD causes deficit characterized by strong tendency to produce certain coordination patterns between wrist and finger motions. This deficit may significantly contribute to handwriting impairments in PD by reducing the dexterity in the production of the variety of shapes of the cursive letters. Furthermore, the deficiency revealed in wrist and finger coordination may represent a more general deficit affecting control of various multi-joint movements in PD.

Upper limb movement interruptions are correlated to freezing of gait in Parkinson's disease

Freezing of gait (FOG) in patients with Parkinson's disease (PD) is a common problem of unknown origin, which possibly reflects a general motor control deficit. We investigated the relationship between the frequency of freezing episodes during gait and during a bimanual task in control and subjects with PD with and without FOG. Group differences in spatiotemporal characteristics were also examined as well as the effects of visual cueing. Twenty patients with PD in the off-phase of the medication cycle and five age-matched controls performed a repetitive drawing task in an anti-phase pattern on a digitizer tablet. The task was offered at two different speeds (comfortable and maximal) and two different amplitudes (small and large) with and without visual cueing. The results showed that freezing episodes in the upper limbs occurred in only 10.4% of patient trials and that their occurrence was correlated with FOG scores (Spearman's rho = 0.64). Overall, few spatiotemporal differences were found between freezers, non-freezers and controls, except for an overshooting of the target amplitude in controls. Effects of visual cueing were largely similar in all groups, except for the variability of relative phase, which decreased in non-freezers and controls, and was unaffected in freezers. Despite the fact that general motor differences between subgroups were small, freezing episodes were manifest during a bimanual repetitive upper limb task and were correlated to FOG. Further study into upper limb movement breakdown is warranted to understand the parallel deficits that lead up to FOG.

Impairment of complex upper limb motor function in de novo Parkinson's disease

The aim of the present study was to evaluate complex upper limb motor function in newly diagnosed, untreated Parkinson's disease (PD) patients. Four different unimanual upper limb motor tasks were applied to 13 newly diagnosed, untreated PD patients and 13 age- and sex-matched controls. In a handwriting task, PD patients had significantly reduced sentence length and writing velocity, and decreasing letter height in the course of writing. Furthermore, PD patients performed an aiming task slower with than without target, and showed increased transposition in a pointing task. The results of this study extend previous observations of impaired complex upper limb movements to newly diagnosed, untreated PD patients.

Validity of the Trunk Impairment Scale as a Measure of Trunk Performance in People With Parkinson’s Disease

OBJECTIVE

To evaluate construct validity of the Trunk Impairment Scale (TIS) as a measure of trunk performance in Parkinson's disease (PD).

DESIGN

A cross-sectional study of PD patients and healthy subjects.

SETTING

University rehabilitation research unit.

PARTICIPANTS

Twenty-six PD patients (Hoehn and Yahr stages 2-4) and 26 healthy subjects.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The TIS and its subscales; static and dynamic sitting balance and trunk coordination.

RESULTS

Compared with healthy controls, PD patients showed significantly lower scores on the total TIS, static sitting balance, and coordination subscale. Healthy subjects scored significantly better on the total TIS and coordination subscale compared with patients in the early stage of PD. Patients with PD in the early stage scored significantly higher for the total TIS as well as static and dynamic sitting balance in comparison with PD patients in a later stage. Forward stepwise multiple linear regression analysis showed that trunk impairment in PD patients was significantly related to a combination of older age and a higher score on part III of the Unified Parkinson's Disease Rating Scale, which assesses motor impairments.

CONCLUSIONS

Early detection of trunk deficits and the significant relation with PD severity advocates further evaluation and use of the TIS in PD.