Postural control, gait, and dopamine functions in parkinsonian movement disorders

GABAA Receptor Benzodiazepine Binding Sites and Motor Impairments in Parkinson's Disease

Flumazenil is an allosteric modulator of the γ-aminobutyric acid-A receptor (GABAAR) benzodiazepine binding site that could normalize neuronal signaling and improve motor impairments in Parkinson's disease (PD). Little is known about how regional GABAAR availability affects motor symptoms. We investigated the relationship between regional availability of GABAAR benzodiazepine binding sites and motor impairments in PD. Methods: A total of 11 Patients with PD (males; mean age 69.0 ± 4.6 years; Hoehn and Yahr stages 2-3) underwent [11C]flumazenil GABAAR benzodiazepine binding site and [11C]dihydrotetrabenazine vesicular monoamine transporter type-2 (VMAT2) PET imaging and clinical assessment. Stepwise regression analysis was used to predict regional cerebral correlates of the four cardinal UPDRS motor scores using cortical, striatal, thalamic, and cerebellar flumazenil binding estimates. Thalamic GABAAR availability was selectively associated with axial motor scores (R2 = 0.55, F = 11.0, β = -6.4, p = 0.0009). Multi-ligand analysis demonstrated significant axial motor predictor effects by both thalamic GABAAR availability (R2 = 0.47, β = -5.2, F = 7.2, p = 0.028) and striatal VMAT2 binding (R2 = 0.30, β = -3.9, F = 9.1, p = 0.019; total model: R2 = 0.77, F = 11.9, p = 0.0056). Post hoc analysis demonstrated that thalamic [11C]methyl-4-piperidinyl propionate cholinesterase PET and K1 flow delivery findings were not significant confounders. Findings suggest that reduced thalamic GABAAR availability correlates with worsened axial motor impairments in PD, independent of nigrostriatal degeneration. These findings may augur novel non-dopaminergic approaches to treating axial motor impairments in PD.

Suitability of visual cues for freezing of gait in patients with idiopathic Parkinson's disease: a case-control pilot study

BACKGROUND

Freezing of gait (FOG) is one of the most debilitating symptoms in patients with idiopathic Parkinson's disease (IPD). Visual cues can relieve FOG symptoms. However, there is no consensus on patient characteristics that can benefit from visual cues. Therefore, we examined the differences in IPD patient characteristics according to the effectiveness of visual cueing.

METHODS

Through gait experiments, we investigated the number of FOG occurrences, average FOG period per episode, proportion of FOG duration in the total gait cycles, and FOG-free period gait spatiotemporal parameters in ten participants diagnosed with FOG due to IPD. Subsequently, the differences between their clinical characteristics and striatal dopamine active transporter availability from six subregions of the striatum were compared by dividing them into two groups based on the three reduction rates: occurrence numbers, mean durations per episode, and proportion of FOG duration in the total gait cycles improved by visual cueing using laser shoes. The relationships among these three reduction rates and other FOG-related parameters were also investigated using Spearman correlation analyses.

RESULTS

According to the three FOG-related reduction rates, the group assignments were the same, which was also related to the baseline self-reported FOG severity score (New Freezing of Gait Questionnaire): the more severe the FOG, the poorer the response to the visual cueing. By visual cueing, the better response group demonstrated the characteristics of lower new FOG questionnaire total scores, higher dopamine active transporter availability of the anterior and posterior putamen, and shorter mean duration of FOG per episode in the absence of cueing. These results were replicated using Spearman correlation analyses.

CONCLUSIONS

For FOG symptoms following IPD, gait assistance by visual cueing may be more effective when the total NFOGQ score is lower and the DAT of putamen is higher. Through this study, we demonstrated clinical and striatal dopaminergic conditions to select patients who may be more likely to benefit from visual cueing with laser shoes, and these findings lead to the need for early diagnosis of FOG in patients with IPD.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05080413. Registered on September 14, 2021.

Behavioural and neuroplastic effects of a double-blind randomised controlled balance exercise trial in people with Parkinson's disease

Balance dysfunction is a disabling symptom in people with Parkinson's disease (PD). Evidence suggests that exercise can improve balance performance and induce neuroplastic effects. We hypothesised that a 10-week balance intervention (HiBalance) would improve balance, other motor and cognitive symptoms, and alter task-evoked brain activity in people with PD. We performed a double-blind randomised controlled trial (RCT) where 95 participants with PD were randomised to either HiBalance (n = 48) or a control group (n = 47). We found no significant group by time effect on balance performance (b = 0.4 95% CI [-1, 1.9], p = 0.57) or on our secondary outcomes, including the measures of task-evoked brain activity. The findings of this well-powered, double-blind RCT contrast previous studies of the HiBalance programme but are congruent with other double-blind RCTs of physical exercise in PD. The divergent results raise important questions on how to optimise physical exercise interventions for people with PD.Preregistration clinicaltrials.gov: NCT03213873.

Boxing with and without Kicking Techniques for People with Parkinson's Disease: An Explorative Pilot Randomized Controlled Trial

BACKGROUND

People with Parkinson's disease (PD) benefit from boxing exercise. Adding kicking variations to the boxing may provide additional benefit to improve balance. However, the benefits and adherence to such trainings is unknown.

OBJECTIVE

To explore the feasibility, safety, and benefits on balance of boxing training combined with kicking techniques in comparison to boxing without kicking in PD.

METHODS

Participants were randomized to group-based boxing training with kicking techniques (BK) or to group-based boxing alone training (BO). Both groups trained for one hour, once a week, for a period of 10 weeks. Participants were assessed at baseline and ten weeks post-intervention for difference in balance, fear of falling, balance confidence, walking ability, and quality of life.

RESULTS

Twenty-nine people with PD (median age 64 years; median disease duration 5 years) participated. Both interventions were feasible and acceptable for all participants. No adverse events occurred. Most participants (BK 80%; BO 75%) were satisfied with the training. We found no significant between group difference on either the primary (Mini-BEST) or secondary outcomes. The within group comparison showed that balance improved in both groups after the intervention (BK 22.60 (2.7) to 25.33 (2.64) p = 0.02; BO 23.09 (3.44) to 25.80 (2.39); p = 0.01 on the Mini BEST test).

CONCLUSION

Both types of boxing seem to be feasible and safe. Adding kicking techniques to boxing does not improve balance significantly more than boxing alone. Incorporation of kicking may be a valuable addition to the exercise therapy repertoire.

Noninvasive vagus nerve stimulation in Parkinson's disease: current status and future prospects

INTRODUCTION

Parkinson's disease (PD) is a common progressive neurodegenerative disorder with multifactorial etiology. While dopaminergic medication is the standard therapy in PD, it provides limited symptomatic treatment and non-pharmacological interventions are currently being trialed.

AREAS COVERED

Recent pathophysiological theories of Parkinson's suggest that aggregated α-synuclein form in the gut and spread to nuclei in the brainstem via autonomic connections. In this paper, we review the novel hypothesis that noninvasive vagus nerve stimulation (nVNS), targeting efferent and afferent vagal projections, is a promising therapeutic tool to improve gait and cognitive control and ameliorate non-motor symptoms in people with Parkinson's. We conducted an unstructured search of the literature for any studies employing nVNS in PD as well as for studies examining the efficacy of nVNS on improving cognitive function and where nVNS has been applied to co-occurring conditions in PD.

EXPERT OPINION

Evidence of nVNS as a novel therapeutic to improve gait in PD is preliminary, but early signs indicate the possibility that nVNS may be useful to target dopa-resistant gait characteristics in early PD. The evidence for nVNS as a therapeutic tool is, however, limited and further studies are needed in both brain health and disease.

Effects of robot-assisted gait training on postural instability in Parkinson's disease: a systematic review

INTRODUCTION

Postural instability is a cardinal feature of Parkinson's disease, together with rest tremor, rigidity and bradykinesia. It is a highly disabling symptom that becomes increasingly common with disease progression and represents a major source of reduced quality of life in patients with Parkinson's disease. Rehabilitation aims to enable patients with Parkinson's disease to maintain their maximum level of mobility, activity and independence. To date, a wide range of rehabilitation approaches has been employed to treat postural instability in Parkinson's disease, including robotic training. Our main aim was to conduct a systematic review of current literature about the effects of robot-assisted gait training on postural instability in patients with Parkinson's disease.

EVIDENCE ACQUISITION

A systematic search using the following MeSH terms "Parkinson disease," "postural balance," "robotics," "rehabilitation" AND string "robotics [mh]" OR "robot-assisted" OR "electromechanical" AND "rehabilitation [mh]" OR "training" AND "postural balance [mh]" was conducted on PubMed, Cochrane Library and Pedro electronic databases. Full text articles in English published up to December 2020 were included. Data about patient characteristics, robotic devices, treatment procedures and outcome measures were considered. Every included article got checked for quality. Level of evidence was defined for all studies.

EVIDENCE SYNTHESIS

Three authors independently extracted and verified data. In total, 18 articles (2 systematic reviews, 9 randomized controlled trials, 4 uncontrolled studies and 3 case series/case reports) were included. Both end-effector and exoskeleton devices were investigated as to robot-assisted gait training modalities. No clear relationship between treatment parameters and clinical conditions was observed. We found a high level of evidence about the effects of robot-assisted gait training on balance and freezing of gait in patients with Parkinson's disease.

CONCLUSIONS

This systematic review provides to the reader a complete overview of current literature and levels of evidence about the effects of robot-assisted gait training on postural instability issues (static and dynamic balance, freezing of gait, falls, confidence in activities of daily living and gait parameters related to balance skills) in patients with Parkinson's disease.

Task-oriented circuit training combined with aerobic training improves motor performance and balance in people with Parkinson's Disease

Goal-based training such as task practice combined with aerobic training (AT) has been suggested to improve motor performance and neuroplasticity for people with Parkinson's Disease (PwPD); however, its effect on clinical outcomes is unclear. Therefore, the main aim was to investigate the effects of task-oriented circuit training combined with AT (TOCT-AT) on balance and gait in PwPD. The secondary aim was to investigate the effects of TOCT-AT on functional mobility, balance confidence, disease severity, and quality of life. Twenty-six PwPD were randomly assigned to either to the experimental group (n = 14) or the control group (n = 12). The control group received AT, while the experimental group received TOCT-AT three times a week for 8 weeks. The main outcomes were the Berg Balance Scale (BBS), Postural Stability Test (PST), Limits of Stability Test (LOS), Pull Test (PT), Six Minute Walk Test (6MWT), Timed Up and Go Test (TUG), Activities-specific Balance Confidence Scale (ABC), Unified Parkinson's Disease Rating Scale (UPDRS), and eight-item Parkinson's Disease Questionnaire (PDQ-8) were secondary outcomes. After intervention, between-group comparisons showed that the experimental group significantly improved more than the control group in all outcomes (p < 0.05). Additionally, both groups significantly improved in BBS, 6MWT, TUG, ABC, UPDRS-II, UPDRS-III, UPDRS total, and PDQ-8 (p < 0.05), while only the experimental group significantly improved in PST, LOS, and PT (p < 0.001). This study suggest that TOCT-AT could improve balance and gait performance, which could also be positively translated into functional mobility, balance confidence, disease severity, and quality of life in PwPD.

Resting state connectivity within the basal ganglia and gait speed in older adults with cerebral small vessel disease and locomotor risk factors

BACKGROUND AND AIM

The basal ganglia are critical for planned locomotion, but their role in age-related gait slowing is not well known. Spontaneous regional co-activation of brain activity at rest, known as resting state connectivity, is emerging as a biomarker of functional neural specialization of varying human processes, including gait. We hypothesized that greater connectivity amongst regions of the basal ganglia would be associated with faster gait speed in the elderly. We further investigated whether this association was similar in strength to that of other risk factors for gait slowing, specifically white matter hyperintensities (WMH).

METHODS

A cohort of 269 adults (79-90 years, 146 females, 164 White) were assessed for gait speed (m/sec) via stopwatch; brain activation during resting state functional magnetic resonance imaging, WMH, and gray matter volume (GMV) normalized by intracranial volume via 3T neuroimaging; and risk factors of poorer locomotion via clinical exams (body mass index (BMI), muscle strength, vision, musculoskeletal pain, cardiometabolic conditions, depressive symptoms, and cognitive function). To understand whether basal ganglia connectivity shows distinct clusters of connectivity, we conducted a k-means clustering analysis of regional co-activation among the substantia nigra, nucleus accumbens, subthalamic nucleus, putamen, pallidum, and caudate. We conducted two multivariable linear regression models: (1) with gait speed as the dependent variable and connectivity, demographics, WMH, GMV, and locomotor risk factors as independent variables and (2) with basal ganglia connectivity as the dependent variable and demographics, WMH, GMV, and locomotor risk factors as independent variables.

RESULTS

We identified two clusters of basal ganglia connectivity: high and low without a distinct spatial distribution allowing us to compute an average connectivity index of the entire basal ganglia regional connectivity (representing a continuous measure). Lower connectivity was associated with slower gait, independent of other locomotor risk factors, including WMH; the coefficient of this association was similar to those of other locomotor risk factors. Lower connectivity was significantly associated with lower BMI and greater WMH.

CONCLUSIONS

Lower resting state basal ganglia connectivity is associated with slower gait speed. Its contribution appears comparable to WMH and other locomotor risk factors. Future studies should assess whether promoting higher basal ganglia connectivity in older adults may reduce age-related gait slowing.

KSNR Clinical Consensus Statements: Rehabilitation of Patients with Parkinson's Disease

Clinical consensus statements (CCSs) aim to improve care for patients with Parkinson's disease (PD) and reduce the variability of rehabilitation methods in clinical practice. A literature search was conducted to find available evidence on the rehabilitation of patients with PD and to determine the scope of CCSs. The selection of PD rehabilitation domains and key questions was done using the modified Delphi method in 43 expert panels. These panels achieved a consensus on 11 key questions regarding rehabilitation assessment and goal setting, gait and balance, activities of daily living, and swallowing and communication disorders. After the completion of an agreement procedure, 11 key consensus statements were developed by the consensus panel. These statements addressed the needs of rehabilitation as a continuum in patients with PD. They included the appropriate rehabilitation initiation time, assessment items, rehabilitation contents, and complication management. This agreement can be used by physiatrists, rehabilitation therapists, and other practitioners who take care of patients with PD. The consensus panel also highlighted areas where a consensus could not be reached. The development of more focused CCS or clinical practice guidelines that target specific rehabilitation approaches is considered the next needed step.

Dopamine replacement improves motor learning of an upper extremity task in people with Parkinson disease

BACKGROUND

Dopamine replacement medication has positive effects on existing motor skills for people with Parkinson disease (PD), but may have detrimental effects on the learning of motor skills necessary for effective rehabilitation according to the dopamine overdose hypothesis.

OBJECTIVES

This study aimed to determine whether dopamine replacement medication (i.e. levodopa) affects: learning of a novel upper extremity task, decrements in skill following withdrawal of practice, the rate of learning, and the transfer of movement skill to untrained upper extremity tasks compared to training "off" medication, in people with PD.

METHODS

Participants with mild-moderate PD (Hoehn and Yahr stage 2) were randomized to train "on" (n = 12) or "off" (n = 11) levodopa medication. Participants practiced 10 blocks of five trials of a functional motor task with their non-dominant upper extremity over three consecutive days (acquisition period), followed by a single block of five trials two and nine days later. Participants were also assessed "on" levodopa with two transfer tasks (the nine-hole peg test and a functional dexterity task) prior to any practice and nine days after the end of the acquisition period.

RESULTS

Participants who practiced "on" levodopa medication learned the upper extremity task to a greater extent that those who practiced "off" medication, as determined by retained performance two days after practice. Skill decrement and skill transfer were not significantly different between groups. Rate of learning was unable to be modelled in this sample.

CONCLUSIONS

Levodopa medication improved the learning of an upper extremity task in people with mild-moderate PD.

Physiological complexity of gait between regular and non-exercisers with Parkinson's disease

BACKGROUND

Physiological complexity represents overall health of a system and its underlying capacity to adapt to stresses. The primary purpose of this study was to determine if physiological complexity of gait both ON and OFF anti-Parkinson medication differed between regular and non-exercisers with Parkinson's disease.

METHODS

Twenty participants with idiopathic Parkinson's disease were enrolled in this cross-sectional study (regular exercisers n = 10, non-exercisers n = 10). Two data collection sessions were completed during a single visit, first after a 12-hour overnight withdrawal from anti-Parkinson medications (OFF), and again one-hour after taking anti-Parkinson medications (ON). During each session participants completed a 2-minute walking task at their preferred pace while wearing wireless inertial measurement units on each lower extremity segment (thigh, shank, foot). Multivariate multiscale entropy was calculated from the tri-axial accelerometer signals and converted to a complexity index for analysis.

FINDINGS

Regular exercisers demonstrated significantly higher complexity indices ON and OFF anti-Parkinson medications compared to non-exercisers (ON F = 3.84 P = 0.02; OFF F = 3.61, P < 0.03). Regular exercisers did not significantly differ in complexity between OFF and ON states (most affected leg F = 0.15 P = 0.71; least affected leg F = 0.30 P = 0.60), but non-exercisers demonstrated significantly decreased complexity in the least affected leg OFF anti-Parkinson medications (F = 5.17 P < 0.04).

INTERPRETATION

Enhanced gait complexity in the regular exercisers may indicate that ongoing exercise is a key ingredient contributing to health in persons with Parkinson's disease. Exercising on a regular basis with Parkinson's disease may augment one's ability to adapt to barriers encountered during gait regardless of medication state.

Memory, Subjective Memory and Motor Functioning in Non-Demented Elders With and Without Parkinson's Disease

Parkinson's Disease (PD) is a progressive neurological condition characterized by motor and non-motor symptoms impacting life quality. The main aim of the current study was to investigate the effect of PD on objective (i.e., working memory and semantic memory) and subjective memory (i.e., self-reported seriousness of forgetting, mnemonic usage and actual memory efficiency) controlling for the effect of depressive symptomatology. The relationship of working memory performance to gait and mobility indices was also examined, as well as the factors predicting subjective memory were explored. Fifty-four community-dwelling adults (mean age = 72.3 years, SD = 8.8) were recruited in Sardinia, an Italian island located in the Mediterranean Sea. Specifically, 27 non-demented adults with mild, early-stage PD were matched for years of education, age, and gender with a sample of healthy individuals. Participants completed a test battery assessing objective memory, subjective memory, and depressive symptoms, and an instrumental analysis of gait and functional mobility was performed. Participants with PD had poorer objective memory across all indices measured and displayed a restricted set of gait and posture impairments. Working memory performance was selectively related to gait and posture measures. Moreover, participants with PD had lower trust in their memory efficiency relative to the past than the control healthy group. Finally, 22% of the variance in seriousness of the consequences of forgetting was predicted by education and general cognitive efficiency. Overall, the present findings confirm the presence of changes in both objective and subjective memory in PD, independent from depressive symptoms.

Maximum Step Length Test Performance in People With Parkinson Disease: A Cross-sectional Study

BACKGROUND AND PURPOSE

The Maximum Step Length Test (MSLT), a measure of one's capacity to produce a large step, has been studied in older adults, but not in people with Parkinson disease (PD). We characterized performance and construct validity of the MSLT in PD.

METHODS

Forty participants (mean age: 65.12 ± 8.20 years; 45% female) with idiopathic PD completed the MSLT while "OFF" and "ON" anti-PD medication. Construct validity was investigated by examining relationships between MSLT and measures of motor performance. The following measures were collected: Mini-Balance Evaluation Systems Test (Mini-BESTest), Activities-specific Balance Confidence (ABC) scale, gait velocity, 6-minute walk test (6MWT), Movement Disorder Society-Unified Parkinson Disease Rating Scale subsection III (MDS-UPDRS III), and Timed Up and Go (TUG) test. A repeated-measures analysis of variance tested for main effects of medication and stepping direction and the interaction between the 2. Pearson or Spearman correlations were used to assess the relationships between MSLT and motor performance measures (α = 0.05).

RESULTS

Regardless of medication status, participants stepped further in the forward direction compared with the backward and lateral directions (P < 0.001). Participants increased MSLT performance when ON-medication compared with OFF-medication (P = 0.004). Regardless of medication status, MSLT was moderately to strongly related to Mini-BESTest, TUG, and 6MWT.

DISCUSSION AND CONCLUSIONS

People with PD stepped furthest in the forward direction when performing the MSLT. Increased MSLT performance was observed in the ON-medication state compared with OFF-medication; however, the small increase may not be clinically meaningful. Given the relationships between the MSLT and the Mini-BESTest, 6MWT, and TUG, MSLT performance appears to be associated with balance and gait hypokinesia in people with PD.Video Abstract available for more insights from the authors (see Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A186).

The reliability of gait variability measures for individuals with Parkinson's disease and healthy older adults - The effect of gait speed

BACKGROUND

Step-to-step variability is a marker of reduced motor control and a frequently studied outcome measure in neurodegenerative disorders such as Parkinson's disease (PD) as compared to healthy older adults (HOA). To challenge motor control of gait, walking should be tested at different gait speeds. Good reliability is essential, and gait variability estimates show good reproducibility when sampled at normal gait speed. The aim was therefore to investigate if gait variability could be reliably sampled at slow and fast speeds for individuals with PD and HOA by evaluating test-retest reliability.

METHODS

29 (14 males) subjects with idiopathic PD, Hoehn &Yahr 2 (n = 18) and 3, ≥ 60 years, and 25 age matched HOAwere included. Spatiotemporal gait data was collected (GAITRite) during slow, normal, and fast walking on two occasions.

RESULTS

Measurement error was lowest for gait variability estimates based on 40 steps in both groups. This was true across all speeds in HOA, but only for normal and fast gait speeds in the PD cohort. Due to increased homogeneity in the variability estimates intraclass correlation coefficients (ICC) were low for HOA, except for step width variability. In the PD cohort ICCs were good to excellent for temporal- and step width gait variability across speeds.

CONCLUSION

HOA demonstrated reliable gait variability estimates across all speeds, whereas Individuals with PD were reliable at normal and fast gait speeds only Estimates should be based on at least 40 steps. Step width variability was overall the most reliable variable across groups and speed conditions.

Peripheral neuropathy is associated with more frequent falls in Parkinson's disease

INTRODUCTION

Peripheral neuropathy is a common condition in the elderly that can affect balance and gait. Postural imbalance and gait difficulties in Parkinson's disease (PD), therefore, may stem not only from the primary neurodegenerative process but also from age-related medical comorbidities. Elucidation of the effects of peripheral neuropathy on these difficulties in PD is important to provide more targeted and effective therapy. The purpose of this study was to investigate the association between lower-limb peripheral neuropathy and falls and gait performance in PD while accounting for disease-specific factors.

METHODS

From a total of 140 individuals with PD, 14 male participants met the criteria for peripheral neuropathy and were matched 1:1 for Hoehn & Yahr stage and duration of disease with 14 male participants without peripheral neuropathy. All participants underwent fall (retrospectively) and gait assessment, a clinical evaluation, and [¹¹C]dihydrotetrabenazine and [¹¹C]methylpiperidin-4-yl propionate PET imaging to assess dopaminergic and cholinergic denervation, respectively.

RESULTS

The presence of peripheral neuropathy was significantly associated with more falls (50% vs. 14%, p = 0.043), as well as a shorter stride length (p = 0.011) and greater stride length variability (p = 0.004), which resulted in slower gait speed (p = 0.016) during level walking. There was no significant difference in nigrostriatal dopaminergic denervation, cortical and thalamic cholinergic denervation, and MDS-UPDRS motor examination scores between groups.

CONCLUSION

Lower-limb peripheral neuropathy is significantly associated with more falls and gait difficulties in PD. Thus, treating such neuropathy may reduce falls and/or improve gait performance in PD.

The effects of anxiety and external attentional focus on postural control in patients with Parkinson's disease

Background

Although anxiety is a common non-motor outcome of Parkinson's disease (PD) affecting 40% of patients, little attention has been paid so far to its effects on balance impairment and postural control. Improvement of postural control through focusing on the environment (i.e. external focus) has been reported, but the role of anxiety, as a confounding variable, remains unclear.

Objectives

This study aimed to investigate the influence of anxiety and attentional focus instruction on the standing postural control of PD patients.

Methods

Thirty-four patients with PD (17 with high anxiety (HA-PD) and 17 with low anxiety (LA-PD)), as well as 17 gender- and age-matched healthy control subjects (HC) participated in the study. Postural control was evaluated using a combination of two levels of postural difficulty (standing on a rigid force plate surface with open eyes (RO) and standing on a foam surface with open eyes (FO)), as well as three attentional focus instructions (internal, external and no focus).

Results

Only the HA-PD group demonstrated significant postural control impairment as compared to the control, as indicated by significantly greater postural sway measures. Moreover, external focus significantly reduced postural sway in all participants especially during the FO condition.

Conclusion

The results of the current study provide evidence that anxiety influences balance control and postural stability in patients with PD, particularly those with high levels of anxiety. The results also confirmed that external focus is a potential strategy that significantly improves the postural control of these patients. Further investigation of clinical applicability is warranted towards developing effective therapeutic and rehabilitative treatment plans.

A 9-Week Nordic and Free Walking Improve Postural Balance in Parkinson's Disease

Aerobic training has a neuroprotective effect in people with Parkinson's disease. Recent evidence indicates that Nordic walking seems a promising alternative due to positive outcomes in functional mobility. However, the effects of Nordic walking compared to free walking on static and functional balance parameters are still unknown. The aim of this study was to evaluate the effects of nine weeks of Nordic and free walking training on static and functional balance. The sample size was 33 individuals with eight dropouts, leaving 25 individuals in the final sample (Nordic Walking, n=14, Free Walking, n=11). The participants underwent two evaluations in the present randomized clinical trial, pre- and post-training, to determine average velocity and root-mean-square values from center of pressure with eyes open and eyes closed. The functional balance showed approximately 5% improvement for the two groups ( p =0.04). The results indicate that nine weeks of Nordic and free walking training were enough to induce improvements in the proprioceptive system and functional balance.

"Pushing the Limits": Rethinking Motor and Cognitive Resources After a Highly Challenging Balance Training Program for Parkinson Disease

BACKGROUND

There is growing evidence for the positive effects of exercise training programs on balance control in Parkinson disease (PD). To be effective, balance training needs to be specific, progressive, and highly challenging. Little evidence exists, however, for how people with PD-related balance impairments perceive highly challenging and progressive balance training programs with dual-task components.

OBJECTIVE

The purpose of this study was to explore and describe perceptions of a highly challenging balance training program among people with mild to moderate PD.

DESIGN

This study was qualitative in nature. In-depth interviews were conducted with 13 individuals with mild to moderate PD who had participated in a highly challenging balance training program. Interview transcripts were analyzed using qualitative content analysis, with an inductive approach.

RESULTS

The analysis revealed 3 subthemes concerning participants' perceptions of highly challenging and progressive balance training: (1) movement to counter the disease, (2) dual-task training in contrast to everyday strategies, and (3) the struggle to maintain positive effects. The first subtheme reflects how physical activity was used as a short-term and long-term strategy for counteracting PD symptoms and their progression. The second subtheme incorporates the described experiences of being maximally challenged in a secure and supportive group environment, circumstances that stood in contrast to participants' everyday lives. The third subtheme describes participants' long-term struggle to maintain program effects on cognitive and physical function in the face of disease progression. Interpretation of the underlying patterns of these subthemes resulted in one overarching theme: training at the limits of balance capacity causes a rethinking motor and cognitive resources.

LIMITATIONS

The findings of this study cannot be considered to reflect the beliefs of those with weaker or negative beliefs concerning physical activity or be transferred to those at more severe stages of the disease.

CONCLUSIONS

Findings from this study suggest that being pushed to the limits of balance capacity provoked people with mild to moderate PD to rethink their individual motor and cognitive resources, a process that was further enabled by the PD-specific group setting.

Relationship between the plasma levels of neurodegenerative proteins and motor subtypes of Parkinson's disease

The aim of our study is to examine the plasma levels of the four kinds of neurodegenerative proteins in plasma: α-syn, T-tau, P-tau_181, and Aβ-42 in Parkinson's disease (PD) and to evaluate the relationship between their plasma levels and PD motor subtypes. 84 patients with PD were enrolled in our study, and finally, 73 of them were classified into the tremor-dominant subtype (TD) and the postural instability gait difficulty subtype (PIGD). Their motor performance was evaluated by a series of clinical assessments: Freezing of Gait Questionnaire (FOGQ), Timed Up and Go (TUGs), Tinetti balance, and Tinetti gait. Plasma levels of these proteins were measured by enzyme-linked immunosorbent assay (ELISA). The plasma level of α-syn was significantly higher in PD patients when compared to controls (p = 0.004), and significantly higher in the PIGD group when compared to the TD group (p = 0.03). While the plasma level of Aβ-42 was significantly lower in PD patients than in controls (p = 0.002), and significantly lower in the PIGD group than in the TD group (p = 0.05). In PD patients, the plasma level of α-syn (r = -0.355, p < 0.001) was significantly related to the severity of Tenitti Gait score, even after performing multiple linear regression (p = 0.002). While the plasma level of Aβ-42 (r = -0.261, p < 0.05) was significantly associated with the severity of PIGD score and remained correlate when performed multiple linear regression (p = 0.005). The patients with PIGD subtype are characterized with a lower level of plasma Aβ-42 and a higher plasma level of α-syn, which may be used as biomarkers for diagnosis and progression of the subtypes of PD.

Pre- and unplanned walking turns in Parkinson's disease - Effects of dopaminergic medication

Although dopaminergic medication improves functional mobility in individuals with Parkinson's disease (PD), its effects on walking turns are uncertain. Our goals was to determine whether dopaminergic medication improves preplanned and unplanned walking turns in individuals with PD, compared to healthy controls. Nineteen older adults with mild-to-moderate PD and 17 healthy controls performed one of the following three tasks, presented randomly: walking straight, or walking and turning 180° to the right or left. The walking direction was visually cued before starting to walk (preplanned) or after (unplanned, i.e., 0.6m before reaching the turning point). Subjects with PD were assessed off dopaminergic medication (OFF) and on dopaminergic medication (ON) medication. Turning strategy (step and spin turns), turning performance (turning distance and body rotation) and walking pattern were analyzed for three turning steps. Irrespective of medication state and turning condition, step and spin turns followed a nearly 50:50 distribution. After intake of dopaminergic medication, subjects with PD increased their turning distance but not the amount of body rotation or their walking pattern. Compared to controls, turning impairments in subjects with PD remained while ON medication and problems regulating step width were the most prominent features of their walking pattern. Specifically, subjects with PD turned with narrower cross-over steps, i.e. when the external foot crossed over the line of progression of the internal leg. We conclude that turning impairments remained even after dopaminergic medication and problems modulating step width appears to be a critical feature for turning in PD.

Investigation of Proposed Activity of Clarithromycin at GABAA Receptors Using [(11)C]Flumazenil PET

Clarithromycin is a potential treatment for hypersomnia acting through proposed negative allosteric modulation of GABAA receptors. We were interested whether this therapeutic benefit might extend to Parkinson's disease (PD) patients because GABAergic neurotransmission is implicated in postural control. Prior to initiating clinical studies in PD patients, we wished to better understand clarithromycin's mechanism of action. In this work we investigated whether the proposed activity of clarithromycin at the GABAA receptor is associated with the benzodiazepine binding site using in vivo [(11)C]flumazenil positron emission tomography (PET) in primates and ex vivo [(3)H]flumazenil autoradiography in rat brain. While the studies demonstrate that clarithromycin does not change the K d of FMZ, nor does it competitively displace FMZ, there is preliminary evidence from the primate PET imaging studies that clarithromycin delays dissociation and washout of flumazenil from the primate brain in a dose-dependent fashion. These findings would be consistent with the proposed GABAA allosteric modulator function of clarithromycin. While the results are only preliminary, further investigation of the interaction of clarithromycin with GABA receptors and/or GABAergic medications is warranted, and therapeutic applications of clarithromycin alone or in combination with flumazenil, to treat hyper-GABAergic status in PD at minimally effective doses, should also be pursued.

Pharmacological treatment in Parkinson's disease: Effects on gait

Gait impairments are a hallmark of Parkinson's disease (PD), both as early symptom and an important cause of disability later in the disease course. Although levodopa has been shown to improve gait speed and step length, the effect of dopamine replacement therapy on other aspects of gait is less well understood. In fact, falls are not reduced and some aspects of postural instability during gait are unresponsive to dopaminergic treatment. Moreover, many medications other than dopaminergic agents, can benefit or impair gait in people with PD. We review the effects of pharmacological interventions used in PD on gait, discriminating, whenever possible, among effects on four components of everyday mobility: straight walking, gait initiation, turning, gait adaptability. Additionally, we summarize the effects on freezing of gait. There is substantial evidence for improvement of spatial characteristics of simple, straight-ahead gait with levodopa and levodopa-enhancing drugs. Recent work suggests that drugs aiming to enhance the acetylcholine system might improve gait stability measures. There is a lack of well-designed studies to evaluate effects on more complex, but highly relevant walking abilities such as turning and making flexible adjustments to gait. Finally, paucity in the literature exists on detrimental effects of drugs used in PD that are known to worsen gait and postural stability in the elderly population.

Manganese-Induced Parkinsonism and Parkinson's Disease: Shared and Distinguishable Features

Manganese (Mn) is an essential trace element necessary for physiological processes that support development, growth and neuronal function. Secondary to elevated exposure or decreased excretion, Mn accumulates in the basal ganglia region of the brain and may cause a parkinsonian-like syndrome, referred to as manganism. The present review discusses the advances made in understanding the essentiality and neurotoxicity of Mn. We review occupational Mn-induced parkinsonism and the dynamic modes of Mn transport in biological systems, as well as the detection and pharmacokinetic modeling of Mn trafficking. In addition, we review some of the shared similarities, pathologic and clinical distinctions between Mn-induced parkinsonism and Parkinson’s disease. Where possible, we review the influence of Mn toxicity on dopamine, gamma aminobutyric acid (GABA), and glutamate neurotransmitter levels and function. We conclude with a survey of the preventive and treatment strategies for manganism and idiopathic Parkinson’s disease (PD).

Lower limb progressive resistance training improves leg strength but not gait speed or balance in Parkinson's disease: a systematic review and meta-analysis

The use of progressive resistance training (PRT) to improve gait and balance in people with Parkinson’s disease (PD) is an emerging area of interest. However, the main effects of PRT on lower limb functions such as gait, balance, and leg strength in people with PD remain unclear. Therefore, the aim of the meta-analysis is to evaluate the evidence surrounding the use of PRT to improve gait and balance in people with PD. Five electronic databases, from inception to December 2014, were searched to identify the relevant studies. Data extraction was performed by two independent reviewers and methodological quality was assessed using the PEDro scale. Standardized mean differences (SMD) and 95% confidence intervals (CIs) of fixed and random effects models were used to calculate the effect sizes between experimental and control groups and I² statistics were used to determine levels of heterogeneity. In total, seven studies were identified consisting of 172 participants (experimental n = 84; control n = 88). The pooled results showed a moderate but significant effect of PRT on leg strength (SMD 1.42, 95% CI 0.464–2.376); however, no significant effects were observed for gait speed (SMD 0.418, 95% CI −0.219 to 1.055). No significant effects were observed for balance measures included in this review. In conclusion, our results showed no discernable effect of PRT on gait and balance measures, although this is likely due to the lack of studies available. It may be suggested that PRT be performed in conjunction with balance or task-specific functional training to elicit greater lower limb functional benefits in people with PD.

The Effects of Highly Challenging Balance Training in Elderly With Parkinson's Disease: A Randomized Controlled Trial

Background. Highly challenging exercises have been suggested to induce neuroplasticity in individuals with Parkinson’s disease (PD); however, its effect on clinical outcomes remains largely unknown. Objective. To evaluate the short-term effects of the HiBalance program, a highly challenging balance-training regimen that incorporates both dual-tasking and PD-specific balance components, compared with usual care in elderly with mild to moderate PD. Methods. Participants with PD (n = 100) were randomized, either to the 10-week HiBalance program (n = 51) or to the control group (n = 49). Participants were evaluated before and after the intervention. The main outcomes were balance performance (Mini-BESTest), gait velocity (during normal and dual-task gait), and concerns about falling (Falls Efficacy Scale–International). Performance of a cognitive task while walking, physical activity level (average steps per day), and activities of daily living were secondary outcomes. Results. A total of 91 participants completed the study. After the intervention, the between group comparison showed significantly improved balance and gait performance in the training group. Moreover, although no significant between group difference was observed regarding gait performance during dual-tasking; the participants in the training group improved their performance of the cognitive task while walking, as compared with the control group. Regarding physical activity levels and activities of daily living, in comparison to the control group, favorable results were found for the training group. No group differences were found for concerns about falling. Conclusions. The HiBalance program significantly benefited balance and gait abilities when compared with usual care and showed promising transfer effects to everyday living. Long-term follow-up assessments will further explore these effects.

Greater Loss of White Matter Integrity in Postural Instability and Gait Difficulty Subtype of Parkinson's Disease

Background: Patients with the postural instability and gait difficulty (PIGD) subtype of Parkinson disease (PD) are at a higher risk of dysfunction and are less responsive to dopamine replacement therapy. The PIGD subtype was found to largely associate with white matter lesions, but details of the diffusion changes within these lesions have not been fully investigated. Voxel-based analysis for diffusion tensor imaging data is one of the preferred measures to compare diffusion changes in each voxel in any part of the brain. Methods: PD patients with the PIGD (n=12) and non-PIGD subtypes (n=12) were recruited to compare diffusion differences in fractional anisotropy, axial diffusivity, and radial diffusivity with voxel-based analysis. Results: Significantly reduced fractional anisotropy in bilateral superior longitudinal fasciculus, bilateral anterior corona radiata, and the left genu of the corpus callosum were shown in the PIGD subtype compared with the non-PIGD subtype. Increased radial diffusivity in the left superior longitudinal fasciculus was found in the PIGD subtype with no statistical differences in axial diffusivity found. Conclusions: Our study confirms previous findings that white matter abnormalities were greater in the PIGD subtype than in the non-PIGD subtype. Additionally, our findings suggested: (1) compared with the non-PIGD subtype, loss of white matter integrity was greater in the PIGD subtype; (2) bilateral superior longitudinal fasciculus may play a critical role in microstructural white matter abnormalities in the PIGD subtype; and (3) reduced white matter integrity in the PIGD subtype could be mainly attributed to demyelination rather than axonal loss.

Dual regulating effects of gastrodin on extracellular dopamine concentration in rats models of Tourette's syndrome

PURPOSE

Evaluate the dual regulating effects of gastrodin on striatal extracellular dopamine (DA) concentration in Tourette's syndrome (TS) rat models, and explore the underlying pharmacological mechanisms.

MATERIALS AND METHODS

Seventy Wistar rats were randomly divided into control group and TS model group. The former was intraperitoneally injected with saline (0.9%), while in the later, the rats were injected with Apomorphine (Apo) and 3,3'-iminodipropionitrile (IDPN) respectively to manipulate two kinds of TS rat models. Both Apo and IDPN induced rats were further assigned to three conditions, and the related rats were treated respectively by oral gavage with saline, gastrodin and Haloperidol (Hal). Data of stereotypy of the rats were collected. After 8 weeks, the extracellular content of DA and HVA in striatum were examined by intracerebral microdialysis and follow-up high-performance liquid chromatography (HPLC), and the expression of dopamine transporter (DAT) was probed by Western blot.

RESULTS

Gastrodin improved the stereotyped behaviors in TS rats. Furthermore, it down-regulated the elevated striatal extracellular DA concentration in Apo-induced rats and up-regulated the decreased DA content in the rats exposed to IDPN. Meanwhile, a dramatic down-regulation was detected in DAT protein expression in Apo + GAS group, while an opposite profile was showed in the IDPN + GAS group.

CONCLUSIONS

The dual regulating effects of gastrodin on extracellular DA level have been established, and the related mechanisms would be the dual regulating effects of gastrodin on the expression of DAT, a glycoprotein in the regulation of the extracellular DA concentration.

Targeting the dopamine system in the treatment of attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable condition that affects a significant number of children and adults worldwide. During the past 30 years, the diagnosis and treatment of ADHD has relied on clinical assessment and empirical experience with stimulant medications. More recently, advances in family genetic studies, molecular genetic studies, preclinical research, radiographic imaging techniques and neuropsychological evaluation have significantly enhanced our understanding of the neurobiology of ADHD. This review highlights the current central role of dopamine in the pathophysiology and treatment of ADHD and implications for future advances in diagnosis and treatment.

Effects of dopamine replacement therapy on lower extremity kinetics and kinematics during a rapid force production task in persons with Parkinson disease

Postural instability appears to be a dopamine resistance motor deficit in persons with Parkinson disease (PD); however, little is known about the effects of dopamine replacement on the relative biomechanical contributions of individual lower extremity joints during postural control tasks. To gain insight, we examined persons with PD using both clinical and laboratory measures. For a clinical measure of motor severity we utilized the Unified Parkinson Disease Rating Scale motor subsection during both OFF and ON medication conditions. For the laboratory measure we utilized data gathered during a rapid lower extremity force production task. Kinematic and kinetic variables at the hip, knee, and ankle were gathered during a counter movement jump during both OFF and ON medication conditions. Sixteen persons with PD with a median Hoehn and Yahr severity of 2.5 completed the study. Medication resulted in significant improvements of angular displacement for the hip, knee, and ankle. Furthermore, significant improvements were revealed only at the hip for peak net moments and average angular velocity compared to the OFF medication condition. These results suggest that dopamine replacement medication result in decreased clinical motor disease severity and have a greater influence on kinetics and kinematics proximally. This proximally focused improvement may be due to active recruitment of muscle force and reductions in passive restraint during lower extremity rapid force production.

Diabetes is associated with postural instability and gait difficulty in Parkinson disease

BACKGROUND

Comorbid diabetes may be associated with more severe motor impairment in Parkinson disease. In normal elderly individuals, diabetes is associated with parkinsonian features, including gait difficulty and rigidity, though not tremor. Whether diabetes contributes to increased motor dysfunction in Parkinson disease by exacerbating nigrostriatal dopaminergic denervation or through intensification of extranigral pathology is unknown.

METHODS

We performed a case-control study (n = 39) involving 13 Parkinson disease subjects (age 66.4yrs ± 5.5; duration of disease 6.9yrs ± 4.4) with diabetes and 26 age, gender, and duration-of-disease-matched Parkinson disease controls without diabetes. All subjects underwent [(11)C]dihydrotetrabenazine vesicular monoamine transporter type-2 positron emission tomography imaging to assess striatal dihydrotetrabenazine distribution volume ratio and Unified Parkinson disease rating scale motor examination to determine rigidity, bradykinesia, tremor, and postural instability and gait difficulty subscores. Magnetic resonance imaging scans were analyzed to assess leukoaraiosis burden.

RESULTS

After controlling for nigrostriatal dopaminergic denervation, Parkinson disease subjects with diabetes displayed greater postural instability and gait difficulty subscores (t = 3.81, p = 0.0005). There were no differences in bradykinesia, rigidity, or tremor subscores between cases and controls. The association between diabetes and postural instability and gait difficulty persisted after controlling for comorbid hypertension and body mass index. Leukoaraiosis, distal vibratory sense, and levodopa dose equivalents did not differ significantly between cases and controls.

CONCLUSIONS

Diabetes may contribute to postural instability and gait difficulty in Parkinson disease through mechanisms other than nigrostriatal dopaminergic denervation.

β-Amyloid and postural instability and gait difficulty in Parkinson's disease at risk for dementia

Although motor impairments in Parkinson's disease (PD) are attributed to nigrostriatal dopaminergic denervation, postural instability and gait difficulty (PIGD) features are less responsive to dopaminergic medications. PIGD features are a risk factor also for the development of dementia in PD (PDD). These observations suggest that nondopaminergic mechanisms may contribute to axial motor impairments. The aim was to perform a correlative PET study to examine the relationship between neocortical β-amyloid deposition ([(11)C]-Pittsburgh Compound B), nigrostriatal dopaminergic denervation ([(11)C]-dihydrotetrabenazine), and PIGD feature severity in PD patients at risk for dementia. This was a cross-sectional study of 44 PD patients (11 female and 33 male; 69.5 ± 6.6 years of age; 7.0 ± 4.8 years motor disease duration; mean H & Y stage: 2.7 ± 0.5) who underwent PET, motor feature severity assessment using the Movement Disorder Society revised UPDRS, and the Dementia Rating Scale (DRS). Linear regression (R(2)(adj) = 0.147; F(4,39) = 2.85; P = 0.036) showed that increased PIGD feature severity was associated with increased neocortical [(11)C]-Pittsburgh Compound B binding (β = 0.346; t(39) = 2.13; P = 0.039) while controlling for striatal [(11)C]-dihydrotetrabenazine binding, age, and DRS total score. Increased neocortical β-amyloid deposition, even at low-range levels, is associated with higher PIGD feature severity in PD patients at risk for dementia. This finding may explain why the PIGD motor phenotype is a risk factor for the development of PDD.

A novel conceptual framework for balance training in Parkinson's disease-study protocol for a randomised controlled trial

Background

There is increasing scientific knowledge about the interaction between physiological (musculoskeletal, neuromuscular, cognitive and sensory) systems and their influence on balance and walking impairments in Parkinson’s disease. We have developed a new conceptual framework for balance training, emphasising specific components of balance control related to Parkinson’s disease symptoms by using highly challenging, progressive and varying training conditions. The primary aim of this proposed randomised controlled trial will be to investigate the short-term and long-term effects of a 10-week balance training regime in elderly with Parkinson’s disease.

Methods/Design

Eighty participants with mild to moderate idiopathic Parkinson’s disease will be recruited and randomly allocated to an intervention group receiving balance training or a control group whose participants will continue to receive their usual care. The intervention will consist of a 10-week group training regime (1-hour training, three times per week), which will be led by two physiotherapists to ensure training progression and safety. The conceptual framework will be applied by addressing specific balance components (sensory integration, anticipatory postural adjustments, motor agility, stability limits) through varying training conditions and structured progression. Assessment will be conducted through a multi-dimensional battery of outcomes, prior to and immediately after the 10-week intervention, and at 9 and 15 months’ follow-up after entering the study. Primary outcome measures will be balance performance (assessed using the Mini Balance Evaluation Systems Test), change in gait velocity (m/s) between single and dual task walking, and fear of falling (evaluated using the Fall Efficacy Scale International).

Discussion

This study has the potential to provide new insight and knowledge of the effects of specific, varied and challenging balance training on a wide health spectrum in elderly with PD. If found to be effective, this pragmatic approach with translation of theory into practice, can be implemented in existing outpatient care.

Trial registration

NCT01417598

Contribution of brain imaging to the understanding of gait disorders in Alzheimer's disease: a systematic review

Although gait disorders are common in Alzheimer's disease (AD), determining which brain structures and related lesions are specifically involved is a goal yet to be reached. Our objective was to systematically review all published data that examined associations between gait disorders and brain imaging in AD. Of 486 selected studies, 4 observational studies met the selection criteria. The number of participants ranged from 2 to 61 community dwellers (29%-100% female) with prodromal or dementia-stage AD. Quantitative gait disorders (ie, slower gait velocity explained by shorter stride length) were associated with white matter lesions, mainly in the medial frontal lobes and basal ganglia. The nigrostriatal dopamine system was unaffected. Qualitative gait disorders (ie, higher stride length variability) correlated with lower hippocampal volume and function. Gait disorders in AD could be explained by a high burden of age-related subcortical hyperintensities on the frontal-subcortical circuits (nonspecific) together with hippocampal atrophy and hypometabolism (specific).

Medication improves balance and complex gait performance in Parkinson disease

Gait and balance impairments in people with Parkinson disease (PD) may lead to falls and serious injuries. Therefore, it is critical to improve our understanding of the nature of these impairments, including how they respond to prescribed anti-Parkinson medication. This is particularly important for complex balance and gait tasks that may be associated with falls. We evaluated motor function, functional balance, and gait performance during various gait tasks in 22 people with PD OFF and ON medication (PD OFF, PD ON) and 20 healthy older adults. Although MDS-UPDRS-III score, Berg Balance Scale, Mini-Balance Evaluations Systems test, and Timed-Up-and-Go improved in PD with medication, impairments persisted in all measures on medication, compared to controls. Dual task Timed-Up-and-Go did not improve with medication, and PD ON required more time than controls. Gait velocity and stride length improved similarly with medication in PD across forward, fast, backward, dual task forward, and dual task backward gait tasks. Cadence did not change with medication, nor did it differ between PD ON and controls. Velocity and stride length were reduced in PD ON compared to controls. Velocity reductions in PD ON during fast gait were cadence-mediated, while velocity reductions in backward gait were stride length-mediated. Our results suggest functional balance improves with medication in PD and gait performance improves with medication, regardless of task complexity. Remaining impairments on medication highlight the need to examine additional therapeutic options for individuals with PD to reduce the risk of falls.

Improved Dynamic Postural Task Performance without Improvements in Postural Responses: The Blessing and the Curse of Dopamine Replacement

Introduction. Dopamine-replacement medications may improve mobility while not improving responses to postural challenges and could therefore increase fall risk. The purpose of this study was to measure reactive postural responses and gait-related mobility of patients with PD during ON and OFF medication conditions. Methods. Reactive postural responses to the Pull Test and performance of the Functional Gait Assessment (FGA) were recorded from 15 persons with PD during ON and OFF medication conditions. Results. Persons with PD demonstrated no significant difference in the reactive postural responses between medication conditions but demonstrated significantly better performance on the FGA when ON medications compared to OFF. Discussion/Conclusion. Dopamine-replacement medications alone may improve gait-related mobility without improvements in reactive postural responses and therefore could result in iatrogenic increases in fall risk. Rehabilitation providers should be aware of the side effects and limitations of medication treatment and implement interventions to improve postural responses.

Postural sway in patients with mild to moderate Parkinson's disease

Clinical assessment of postural instability in persons with Parkinson's disease (PD) is done with the retropulsive pull test, but since this test does not assess the underlying causes of postural instability, there is a need for additional assessment tools. The aim of this study was to identify postural sway parameters for use in a multifactorial approach to quantify postural instability. Nineteen adults diagnosed with idiopathic PD, 14 healthy age-matched controls (EH), and 10 healthy young adults (YH) completed the study. Postural parameters were extracted during quiet standing in eyes open (EO) and eyes closed (EC) conditions. Removing visual feedback affected the groups in a similar way. Significant differences between the PD and the two control groups were found in sway path length, area, and ranges in the anterior-posterior (AP) and medial-lateral (ML) directions and the Hurst exponents. PD significantly increased AP sway path length compared with YH and ML sway path length compared with EH. The Hurst exponents in PD were significantly different than in EH. The results suggest that the ML direction is a successful discriminator between PD and age-matched controls and that the interaction between ML and AP directions should be considered in the method used to quantify postural instability.

Ningdong granule: a complementary and alternative therapy in the treatment of attention deficit/hyperactivity disorder

BACKGROUND

Attention deficit/hyperactivity disorder (ADHD) is a common neurobehavioral and neuropsychiatric disorder in school-age children, and recent studies provide evidence implicating the metabolic abnormalities of dopamine (DA) for its pathophysiology. Methylphenidate, a kind of psychostimulant, is widely used in the treatment of ADHD, but some patients do not respond to it or cannot bear its side effects. As a traditional Chinese medicine preparation, Ningdong granule (NDG) has been used in the treatment of ADHD for several years in China. However, a systematical pharmacological study on its safety and mechanism still remains obscure.

OBJECTIVE

This paper aims to evaluate the efficiency, safety, and possible mechanism of NDG on ADHD children compared to methylphenidate.

METHODS

Seventy-two ADHD children were recruited to perform an 8-week, randomized, methylphenidate-controlled, doubled-blinded trial. The subjects were equally assigned to two groups receiving either NDG 5 mg/kg/day or methylphenidate 1 mg/kg/day for 8 weeks. The efficiency was assessed by the Teacher and Parent ADHD Rating Scales every 2 weeks for a total of 8 weeks. The side effects were recorded during the study. Blood, urine, and stool routine samples, liver and renal function test, and DA and homovanillic acid (HVA) concentration in sera were tested at the beginning and end of the trial.

RESULTS

NDG ameliorated ADHD symptoms after an 8-week medication with fewer side effects compared to methylphenidate (P < 0.05). The result also showed NDG to be safe and tolerable for ADHD children as monitored by the blood, urine, and stool analysis and liver and renal function for 8 weeks (P < 0.05). Moreover, the level of HVA in sera increased in NDG-treated group (P < 0.05), while the content of DA had no significant change during the study. An analysis of Pearson correlation coefficients also showed that the increased content of HVA in sera was associated with the improved scores of Teacher and Parent ADHD Rating Scales.

CONCLUSIONS

Compared to methylphenidate, NDG is effective and safe for ADHD children in the short term, increases the HVA concentration in sera to regulate DA metabolism, and promises to be an alternative medication, safely and effectively.

Leucoaraiosis, nigrostriatal denervation and motor symptoms in Parkinson's disease

Leucoaraiosis is associated with motor symptoms in otherwise normal older adults. Comorbid leucoaraiosis is predicted to contribute also to motor features in Parkinson's disease but previous studies of white matter changes in Parkinson's disease show variable results. No prior studies have compared directly the effects of both leucoaraiosis and the degree of nigrostriatal dopaminergic denervation on motor features. We investigated the effect of leucoaraiosis severity on motor impairment independent of the degree of nigrostriatal dopaminergic denervation in Parkinson's disease. Seventy-three subjects with Parkinson's disease (Hoehn and Yahr stages 1-3) underwent brain magnetic resonance and [(11)C]dihydrotetrabenazine vesicular monoamine transporter type 2 positron emission tomography imaging. Automated assessment of supratentorial fluid-attenuated inversion recovery magnetic resonance hyperintense white matter voxels was performed using cerebellar white matter as the intensity reference. White matter signal hyperintensity burden was log-transformed and normalized for brain volume. Unified Parkinson's Disease Rating Scale total and subscore ratings were assessed to determine motor impairment. Subjects receiving dopaminergic medications were examined in the clinically defined 'OFF' state. Multivariate regression analysis with measures of white matter signal hyperintensity burden and nigrostriatal denervation as independent variables demonstrated a significant overall model for total motor Unified Parkinson's Disease Rating Scale scores (F  = 11.4, P < 0.0001) with significant regression effects for both white matter signal hyperintensity burden (t  = 2.0, β = 0.22, P = 0.045) and striatal monoaminergic binding (t = -3.5, β = -0.38, P = 0.0008). Axial motor impairment demonstrated a robust association with white matter signal hyperintensity burden (t  = 4.0, β = 0.43, P  =0.0001) compared with striatal monoaminergic binding (t = -2.1, β = 0.22, P = 0.043). White matter signal hyperintensity burden regression effects for bradykinesia had borderline significance. No significant white matter signal hyperintensity burden effects were found for rigidity or tremor subscores. White matter signal hyperintensity burden was significantly higher in the subgroup with postural instability and gait difficulties compared with the tremor-predominant subgroup despite no significant differences in age or duration of disease. These findings indicate that increased white matter signal hyperintensity burden is associated with worse motor performance independent of the degree of nigrostriatal dopaminergic denervation in Parkinson's disease. Comorbid white matter disease is a greater determinant of axial motor impairment than nigrostriatal dopaminergic denervation.

Imaging cognitive and behavioral symptoms in Parkinson's disease

Non-motor symptoms are a major and often unrecognized cause of morbidity of Parkinson's disease. In the past few years, imaging technology, such as functional MRI and PET, have provided a large bulk of information about the phenomena. Here, we provide an overview of those imaging studies that may help us understand the neuronal correlates associated with non-motor symptoms in Parkinson's disease, with a particular focus on cognitive and neuropsychiatric deficits.

Recurrent falls and mortality in Parkinson's disease: a prospective two-year follow-up study

OBJECTIVES

To evaluate the risk factors for recurrent falling and mortality in Parkinson's disease (PD) in a prospective study design.

MATERIALS AND METHODS

One hundred and twenty-five PD patients were included in the study. Baseline medical data were collected, and patients were clinically tested for mobility and balance. Falls were prospectively recorded for 2 years. Mortality was documented 4 years after the baseline.

RESULTS

Seventy-nine patients reported altogether 3125 falls during the follow-up, and 59 patients were classified as recurrent fallers. Altogether 126 fall injuries including six fractures were reported. Eighteen patients had died by the time of the hospital chart review. History of falling (OR 3.02, 95% CI 1.23-7.44) and the Unified Parkinson's Disease Rating Scale activities of daily living score (OR 1.13, 95% CI 1.04-1.22) were independent risk factors for recurrent falling in PD, whereas slow walking speed (OR 16.28, 95% CI 1.85-142.97) was an independent risk factor for mortality in PD.

CONCLUSIONS

History of falling and disease severity indicate increased risk of recurrent falls in PD, while patients with slow walking speed may have an increased risk of mortality. Recurrent falling was not associated with increased risk of mortality in PD in this study.

Multisensory determinants of orientation perception in Parkinson's disease

Perception of the relative orientation of the self and objects in the environment requires integration of visual and vestibular sensory information, and an internal representation of the body's orientation. Parkinson's disease (PD) patients are more visually dependent than controls, implicating the basal ganglia in using visual orientation cues. We examined the relative roles of visual and non-visual cues to orientation in PD using two different measures: the subjective visual vertical (SVV) and the perceptual upright (PU). We tested twelve PD patients (nine both on- and off-medication), and thirteen age-matched controls. Visual, vestibular and body cues were manipulated using a polarized visual room presented in various orientations while observers were upright or lying right-side-down. Relative to age-matched controls, patients with PD showed more influence of visual cues for the SVV but were more influenced by the direction of gravity for the PU. Increased SVV visual dependence corresponded with equal decreases of the contributions of body sense and gravity. Increased PU gravitational dependence corresponded mainly with a decreased contribution of body sense. Curiously however, both of these effects were significant only when patients were medicated. Increased SVV visual dependence was highest for PD patients with left-side initial motor symptoms. PD patients when on and off medication were more variable than controls when making judgments. Our results suggest that (i) PD patients are not more visually dependent in general, rather increased visual dependence is task specific and varies with initial onset side, (ii) PD patients may rely more on vestibular information for some perceptual tasks which is reflected in relying less on the internal representation of the body, and (iii) these effects are only present when PD patients are taking dopaminergic medication.

History of falls in Parkinson disease is associated with reduced cholinergic activity

OBJECTIVE

To investigate the relationships between history of falls and cholinergic vs dopaminergic denervation in patients with Parkinson disease (PD).

BACKGROUND

There is a need to explore nondopaminergic mechanisms of gait control as the majority of motor impairments associated with falls in PD are resistant to dopaminergic treatment. Alterations in cholinergic neurotransmission in PD may be implicated because of evidence that gait control depends on cholinergic system-mediated higher-level cortical and subcortical processing, including pedunculopontine nucleus (PPN) function.

METHODS

In this cross-sectional study, 44 patients with PD (Hoehn & Yahr stages I-III) without dementia and 15 control subjects underwent a clinical assessment and [(11)C]methyl-4-piperidinyl propionate (PMP) acetylcholinesterase (AChE) and [(11)C]dihydrotetrabenazine (DTBZ) vesicular monoamine transporter type 2 (VMAT2) brain PET imaging.

RESULTS

Seventeen patients (38.6%) reported a history of falls and 27 patients had no falls. Analysis of covariance of the cortical AChE hydrolysis rates demonstrated reduced cortical AChE in the PD fallers group (-12.3%) followed by the PD nonfallers (-6.6%) compared to control subjects (F = 7.22, p = 0.0004). Thalamic AChE activity was lower only in the PD fallers group (-11.8%; F = 4.36, p = 0.008). There was no significant difference in nigrostriatal dopaminergic activity between PD fallers and nonfallers.

CONCLUSIONS

Unlike nigrostriatal dopaminergic denervation, cholinergic hypofunction is associated with fall status in Parkinson disease (PD). Thalamic AChE activity in part represents cholinergic output of the pedunculopontine nucleus (PPN), a key node for gait control. Our results are consistent with other data indicating that PPN degeneration is a major factor leading to impaired postural control and gait dysfunction in PD.

Is heart rate variability related to gait impairment in patients with Parkinson's disease? A pilot study

BACKGROUND AND PURPOSE

Impairments in gait and autonomic function are common in patients with Parkinson's disease (PD). These are likely independent symptoms, based on different etiologic mechanisms. However, a few recent reports have observed an association between motor function, in particular gait impairment, and autonomic function in PD. In those studies, the Unified Parkinson's Disease Rating Scale (UPDRS) was used to evaluate gait and motor function. The present study was performed to further examine this putative relationship using quantitative measures of autonomic function and gait in order to shed light on the underlying pathophysiology of these symptoms.

METHODS

Nine healthy young, 15 healthy elderly and 18 PD patients were studied. Heart rate variability (HRV) measures were collected during rest. Gait speed, swing time and swing time variability were measured during a 1-min walk at comfortable speed. The motor portion of the UPDRS was also evaluated in all subjects.

RESULTS

HRV values were highest in the young adults, intermediate in the healthy elderly controls, and lowest in the PD patients. Gait measures tended to deteriorate with age and were significantly worse in the PD patients, compared to the elderly controls. HRV was not correlated with any measure of gait performance (p>0.129) nor with the UPDRS-motor score (p>0.147).

DISCUSSION AND CONCLUSIONS

The present findings support the idea that gait and autonomic function impairments co-exist in PD, but their etiology is based on distinct pathophysiological pathways, with minimal overlap.

Perceived imbalance and risk of Parkinson's disease

We prospectively examined associations between perceived imbalance and Parkinson's disease (PD) risk in the Health Professional Follow-up Study (HPFS), and Nurses' Health Study (NHS). We included 39,087 men and 82,299 women free of PD at baseline (1990) in the current analyses. We documented 449 incident PD cases during 12 years follow-up. Subjects who reported difficulty with balance before 1990 (baseline) were 1.8 more times likely to develop PD, relative to those who reported no balance difficulty (pooled multivariate RR = 1.8; 95% CI: 1.3, 2.5; P < 0.0001). When we further examined associations between perceived imbalance at baseline and PD onset during different time periods, we found a significant elevation of PD risk only during the first 4 years of follow-up. This result suggests that the imbalance may in some cases be an early sign of PD, and may represent the onset of motor symptoms although they have not been clinically recognized.

Striatal dopamine denervation and sensory integration for balance in middle-aged and older adults

The dopaminergic system of the basal ganglia has been implicated in the integration of sensory information important for balance based on studies in patients with Parkinson's disease. Striatal dopaminergic activity decreases with normal aging.

OBJECTIVE

To investigate the relationship between regional striatal dopaminergic denervation and sensory information integration important for balance in middle-aged and older adults.

METHODS

Community-dwelling subjects (N=35; age 41-83) with no clinical diagnoses of conditions affecting balance underwent dynamic posturography testing (Sensory Organization Test/SOT) and C-11-beta-CFT dopamine transporter positron emission tomography.

RESULTS

Reduced ventral striatal dopamine was significantly correlated with increased anterior-posterior sway in three SOT conditions. Specifically, during quiet standing (SOT Conditions #1, 2) and when repeatedly to sway-referenced visual environments (SOT Condition #3, Trial #3), pre-synaptic dopaminergic denervation in the anteroventral striatum explained over 20-25% of the variability in sway magnitude above and beyond that explained by age (p<or=0.01). Striatal dopaminergic denervation did not impact balance in sway-referenced floor conditions.

CONCLUSIONS

The SOT Condition #3 findings suggest that, in normal aging, the central ability to inhibit balance destabilizing vision-related postural control processes depends at least partially on striatal dopaminergic pathways. In contrast, striatal dopaminergic denervation does not appear to impair the ability to disengage destabilizing proprioceptive inputs and to trigger the vestibular control system during challenging sensory perturbations (SOT Conditions #4-6). Finally, quiet standing results (SOT Conditions #1, 2) justify the need to further investigate the impact of striatal dopaminergic denervation on the ability to tune muscle tone in healthy adults.