Imposed faster and slower walking speeds influence gait stability differently in Parkinson fallers

Objective To evaluate the effect of imposed faster and slower walking speeds on postural stability in people with Parkinson disease (PD). Design Cross-sectional cohort study. Setting General community. Participants Patients with PD (n=84; 51 with a falls history; 33 without) and age-matched controls (n=82) were invited to participate via neurology clinics and preexisting databases. Of those contacted, 99 did not respond (PD=36; controls=63) and 27 were not interested (PD=18; controls=9). After screening, a further 10 patients were excluded; 5 had deep brain stimulation surgery and 5 could not accommodate to the treadmill. The remaining patients (N=30) completed all assessments and were subdivided into PD fallers (n=10), PD nonfallers (n=10), and age-matched controls (n=10) based on falls history. Interventions Not applicable. Main Outcome Measures Three-dimensional accelerometers assessed head and trunk accelerations and allowed calculation of harmonic ratios and root mean square (RMS) accelerations to assess segment control and movement amplitude. Results Symptom severity, balance confidence, and medical history were established before participants walked on a treadmill at 70%, 100%, and 130% of their preferred speed. Head and trunk control was lower for PD fallers than PD nonfallers and older adults. Significant interactions indicated head and trunk control increased with speed for PD nonfallers and older adults, but did not improve at faster speeds for PD fallers. Vertical head and trunk accelerations increased with walking speed for PD nonfallers and older adults, while the PD fallers demonstrated greater anteroposterior RMS accelerations compared with both other groups. Conclusions The results suggest that improved gait dynamics do not necessarily represent improved walking stability, and this must be respected when rehabilitating gait in patients with PD

A block to pre-prepared movement in gait freezing, relieved by pedunculopontine nucleus stimulation

Gait freezing and postural instability are disabling features of Parkinsonian disorders, treatable with pedunculopontine nucleus stimulation. Both features are considered deficits of proximal and axial musculature, innervated predominantly by reticulospinal pathways and tend to manifest when gait and posture require adjustment. Adjustments to gait and posture are amenable to pre-preparation and rapid triggered release. Experimentally, such accelerated release can be elicited by loud auditory stimuli—a phenomenon known as ‘StartReact’. We observed StartReact in healthy and Parkinsonian controls. However, StartReact was absent in Parkinsonian patients with severe gait freezing and postural instability. Pedunculopontine nucleus stimulation restored StartReact proximally and proximal reaction times to loud stimuli correlated with gait and postural disturbance. These findings suggest a relative block to triggered, pre-prepared movement in gait freezing and postural instability, relieved by pedunculopontine nucleus stimulation

Post-peak fracture behavior during direct shear tests of rock joints

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Plasma biomarkers inclusive of α-synuclein/amyloid-beta40 ratio strongly correlate with Mini-Mental State Examination score in Parkinson's disease and predict cognitive impairment

Plasma biomarkers for Parkinson’s disease (PD) diagnosis that carry predictive value for cognitive impairment are valuable. We explored the relationship of Mini-Mental State Examination (MMSE) score with plasma biomarkers in PD patients and compared results to vascular dementia (VaD) and normal controls. The predictive accuracy of an individual biomarker on cognitive impairment was evaluated using area under the receiver operating characteristic curve (AUROC), and multivariate logistic regression was applied to evaluate predictive accuracy of biomarkers on cognitive impairment; 178 subjects (41 PD, 31 VaD and 106 normal controls) were included. In multiple linear regression analysis of PD patients, α-synuclein, anti-α-synuclein, α-synuclein/Aβ40 and anti-α-synuclein/Aβ40 were highly predictive of MMSE score in both full model and parsimonious model (R2 = 0.838 and 0.835, respectively) compared to non-significant results in VaD group (R2 = 0.149) and in normal controls (R2 = 0.056). Α-synuclein and anti-α-synuclein/Aβ40 were positively associated with MMSE score, and anti-α-synuclein, α-synuclein/Aβ40 were negatively associated with the MMSE score among PD patients (all Ps < 0.005). In the AUROC analysis, anti-α-synuclein (AUROC = 0.788) and anti-α-synuclein/Aβ40 (AUROC = 0.749) were significant individual predictors of cognitive impairment. In multivariate logistic regression, full model of combined biomarkers showed high accuracy in predicting cognitive impairment (AUROC = 0.890; 95%CI 0.796–0.984) for PD versus controls, as was parsimonious model (AUROC = 0.866; 95%CI 0.764–0.968). In conclusion, simple combination of biomarkers inclusive of α-synuclein/Aβ40 strongly correlates with MMSE score in PD patients versus controls and is highly predictive of cognitive impairment

Balance control systems in Parkinson's disease and the impact of pedunculopontine area stimulation

Impaired balance is a major contributor to falls and diminished quality of life in Parkinson’s disease, yet the pathophysiology is poorly understood. Here, we assessed if patients with Parkinson’s disease and severe clinical balance impairment have deficits in the intermittent and continuous control systems proposed to maintain upright stance, and furthermore, whether such deficits are potentially reversible, with the experimental therapy of pedunculopontine nucleus deep brain stimulation. Two subject groups were assessed: (i) 13 patients with Parkinson’s disease and severe clinical balance impairment, implanted with pedunculopontine nucleus deep brain stimulators; and (ii) 13 healthy control subjects. Patients were assessed in the OFF medication state and blinded to two conditions; off and on pedunculopontine nucleus stimulation. Postural sway data (deviations in centre of pressure) were collected during quiet stance using posturography. Intermittent control of sway was assessed by calculating the frequency of intermittent switching behaviour (discontinuities), derived using a wavelet-based transformation of the sway time series. Continuous control of sway was assessed with a proportional–integral–derivative (PID) controller model using ballistic reaction time as a measure of feedback delay. Clinical balance impairment was assessed using the ‘pull test’ to rate postural reflexes and by rating attempts to arise from sitting to standing. Patients with Parkinson’s disease demonstrated reduced intermittent switching of postural sway compared with healthy controls. Patients also had abnormal feedback gains in postural sway according to the PID model. Pedunculopontine nucleus stimulation improved intermittent switching of postural sway, feedback gains in the PID model and clinical balance impairment. Clinical balance impairment correlated with intermittent switching of postural sway (rho = − 0.705, P < 0.001) and feedback gains in the PID model (rho = 0.619, P = 0.011). These results suggest that dysfunctional intermittent and continuous control systems may contribute to the pathophysiology of clinical balance impairment in Parkinson’s disease. Clinical balance impairment and their related control system deficits are potentially reversible, as demonstrated by their improvement with pedunculopontine nucleus deep brain stimulation

Subthalamic stimulation affects homophone meaning generation in Parkinson's disease

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) in individuals with Parkinson's disease (PD) has often been associated with reduced verbal fluency performance. This study aimed to directly assess semantic switching as a function of STN stimulation in PD participants with the Homophone Meaning Generation Test (HMGT). Seventeen participants with PD who had received STN DBS completed the HMGT in on and off stimulation conditions. Twenty-one non-neurologically impaired participants acted as controls. PD participants (in both on and off stimulation conditions) generated significantly fewer meanings than control participants and consistent with the previous reports of verbal fluency impairment, PD participants produced fewer definitions in the on stimulation condition. PD participants (in both on and off stimulation conditions) also had greater difficulty generating definitions for nonhomographic homophones compared with homographic homographs. The results of this study indicate that STN stimulation exacerbates impairment in semantic switching

A good-quality breakfast is associated with better mental health in adolescence

Objective: Breakfast consumption has been associated with better mental health in adulthood, but the relationship between breakfast and mental health in adolescence is less well known. The aims of the present study were to evaluate breakfast quality in a cohort of adolescents and to investigate associations with mental health. Design: Cross-sectional population-based study. Breakfast quality was assessed by intake of core food groups at breakfast, as determined from 3 d food diaries. Mental health was assessed using the Child Behaviour Checklist (CBCL), with higher scores representing poorer behaviour. Setting: The Western Australian Pregnancy Cohort (Raine) Study, Perth, WesternAustralia. Subjects: Eight hundred and thirty-six males and females aged between 13 and 15 years. Results: Mean mental health score as assessed by the CBCL was 45.24 (SD 11.29). A high-quality breakfast consisting of at least three food groups was consumed by 11% of adolescents, while 7% of adolescents did not consume any items from core food groups on average over the 3 d period. The two most common core food groups consumed at breakfast in this population were dairy products followed by breads and cereals. For every additional food group eaten at breakfast, the associated total mental health score decreased by 1.66 (95% CI-22.74, -0.59) after adjustment for potential confounding factors, representing an improvement in mental health score. Conclusion: These findings support the concept that breakfast quality is an important component in the complex interaction between lifestyle factors and mental health in early adolescence.KeywordsAdolescent/adolescenceBreakfastMental healthChild Behaviour Checklis

A neurophysiological study of semantic processing in Parkinson’s disease

Objectives: Cognitive-linguistic impairments in Parkinson's disease (PD) have been well documented; however, few studies have explored the neurophysiological underpinnings of semantic deficits in PD. This study investigated semantic function in PD using event-related potentials. Methods: Eighteen people with PD and 18 healthy controls performed a semantic judgement task on written word pairs that were either congruent or incongruent. Results: The mean amplitude of the N400 for new incongruent word pairs was similar for both groups, however the onset latency was delayed in the PD group. Further analysis of the data revealed that both groups demonstrated attenuation of the N400 for repeated incongruent trials, as well as attenuation of the P600 component for repeated congruent trials. Conclusions: The presence of N400 congruity and N400 repetition effects in the PD group suggests that semantic processing is generally intact, but with a slower time course as evidenced by the delayed N400. Additional research will be required to determine whether N400 and P600 repetition effects are sensitive to further cognitive decline in PD