M. Mancini

ISway: a sensitive, valid and reliable measure of postural control

BackgroundClinicians need a practical, objective test of postural control that is sensitive to mild neurological disease, shows experimental and clinical validity, and has good test-retest reliability. We developed an instrumented test of postural sway (ISway) using a body-worn accelerometer to offer an objective and practical measure of postural control.MethodsWe conducted two separate studies with two groups of subjects. Study I: sensitivity and experimental concurrent validity. Thirteen subjects with early, untreated Parkinson’s disease (PD) and 12 age-matched control subjects (CTR) were tested in the laboratory, to compare sway from force-plate COP and inertial sensors. Study II: test-retest reliability and clinical concurrent validity. A different set of 17 early-to-moderate, treated PD (tested ON medication), and 17 age-matched CTR subjects were tested in the clinic to compare clinical balance tests with sway from inertial sensors. For reliability, the sensor was removed, subjects rested for 30 min, and the protocol was repeated. Thirteen sway measures (7 time-domain, 5 frequency-domain measures, and JERK) were computed from the 2D time series acceleration (ACC) data to determine the best metrics for a clinical balance test.ResultsBoth center of pressure (COP) and ACC measures differentiated sway between CTR and untreated PD. JERK and time-domain measures showed the best test-retest reliability (JERK ICC was 0.86 in PD and 0.87 in CTR; time-domain measures ICC ranged from 0.55 to 0.84 in PD and from 0.60 to 0.89 in CTR). JERK, all but one time-domain measure, and one frequency measure were significantly correlated with the clinical postural stability score (r ranged from 0.50 to 0.63, 0.01 < p < 0.05).ConclusionsBased on these results, we recommend a subset of the most sensitive, reliable, and valid ISway measures to characterize posture control in PD: 1) JERK, 2) RMS amplitude and mean velocity from the time-domain measures, and 3) centroidal frequency as the best frequency measure, as valid and reliable measures of balance control from ISway.

Trunk accelerometry reveals postural instability in untreated Parkinson's disease

While several studies have shown that subjects with advanced Parkinsons disease (PD) exhibit abnormalities in sway parameters during quiet standing, abnormalities of postural sway associated with untreated PD have not been reported. Although not clinically apparent, we hypothesized that spontaneous sway in quiet stance is abnormal in people with untreated PD. We examined 13 subjects, recently diagnosed with PD, who were not yet taking any anti-parkinsonian medications and 12 healthy, age-matched control subjects. Postural sway was measured with a linear accelerometer on the posterior trunk (L5 level) and compared with traditional force plate measures of sway. Subjects stood for 2xa0min under two conditions: eyes open (EO) and eyes closed (EC). One of the most discriminative measures of postural changes in subjects with untreated PD was the increased JERK of lower trunk in the EO condition, measured with the accelerometer. Root mean square and the frequency dispersion of postural sway in the EO condition also discriminated sway in untreated PD subjects compared to control subjects. We conclude that accelerometer-based sway metrics could be used as objective measures of postural instability in untreated PD. Accelerometer-based analysis of spontaneous sway may provide a powerful tool for early clinical trials and for monitoring the effects of treatment of balance disorders in subjects with PD.

Biofeedback for training balance and mobility tasks in older populations : a systematic review

ContextAn effective application of biofeedback for interventions in older adults with balance and mobility disorders may be compromised due to co-morbidity.ObjectiveTo evaluate the feasibility and the effectiveness of biofeedback-based training of balance and/or mobility in older adults.Data SourcesPubMed (1950-2009), EMBASE (1988-2009), Web of Science (1945-2009), the Cochrane Controlled Trials Register (1960-2009), CINAHL (1982-2009) and PsycINFO (1840-2009). The search strategy was composed of terms referring to biofeedback, balance or mobility, and older adults. Additional studies were identified by scanning reference lists.Study SelectionFor evaluating effectiveness, 2 reviewers independently screened papers and included controlled studies in older adults (i.e. mean age equal to or greater than 60 years) if they applied biofeedback during repeated practice sessions, and if they used at least one objective outcome measure of a balance or mobility task.Data ExtractionRating of study quality, with use of the Physiotherapy Evidence Database rating scale (PEDro scale), was performed independently by the 2 reviewers. Indications for (non)effectiveness were identified if 2 or more similar studies reported a (non)significant effect for the same type of outcome. Effect sizes were calculated.Results and ConclusionsAlthough most available studies did not systematically evaluate feasibility aspects, reports of high participation rates, low drop-out rates, absence of adverse events and positive training experiences suggest that biofeedback methods can be applied in older adults. Effectiveness was evaluated based on 21 studies, mostly of moderate quality. An indication for effectiveness of visual feedback-based training of balance in (frail) older adults was identified for postural sway, weight-shifting and reaction time in standing, and for the Berg Balance Scale. Indications for added effectiveness of applying biofeedback during training of balance, gait, or sit-to-stand transfers in older patients post-stroke were identified for training-specific aspects. The same applies for auditory feedback-based training of gait in older patients with lower-limb surgery.ImplicationsFurther appropriate studies are needed in different populations of older adults to be able to make definitive statements regarding the (long-term) added effectiveness, particularly on measures of functioning.

Step initiation in Parkinson's disease: Influence of initial stance conditions

In this study, we investigated how the size of preparatory postural adjustments prior to step initiation, and step length and velocity depend on initial stance width in patients with Parkinsons disease (PD) both in the ON and OFF levodopa states and in healthy elderly subjects. Twenty-one subjects with idiopathic PD and 24 age-matched healthy control subjects took two steps starting with feet on a two-plate force-platform, from either narrow or wide stance width. We measured how the magnitude of anticipatory postural adjustments (APA) and step characteristics scaled with stance width. Results showed that preparation for step initiation from wide stance was associated with a larger lateral and backward center of pressure (CoP) displacement than from narrow stance. Velocity and length of the first step were also sensitive to initial stance conditions, probably in relation with the differences in the corresponding APA. On the contrary, the duration of APA was not significantly affected by initial stance width, but it was longer in PD compared to healthy subjects, and speeded up by levodopa. Although subjects with PD did scale up the size of their APA with stance width, they had much more difficulty initiating a step from a wide stance than from a narrow stance, as shown by the greater differences from control subjects in the magnitude of the APA. Our results support the hypothesis that PD subjects maintain a narrow stance as a compensation for their inability to sufficiently increase the size of their lateral APA to allow fast step initiation in wide stance.

Postural sway as a marker of progression in Parkinson's disease: A pilot longitudinal study

Objective measures of postural control that are sensitive to Parkinsons disease (PD) progression would improve patient care and accelerate clinical trials. Although measures of postural sway during quiet stance in untreated PD have been shown to differ from age-matched control subjects, it is not known if sway measures change with disease progression in early PD. In this pilot study, we asked whether accelerometer-based metrics of sway could provide a practical tool for monitoring progression of postural dyscontrol in people with untreated or newly treated PD. We examined 13 subjects with PD and 12 healthy, age-matched control subjects. The PD subjects had been recently diagnosed and had not started any antiparkinsonian medications at the baseline session. All subjects were tested 3-6 months and 12 months after the baseline session. Subjects were asked to stand quietly for two minutes while wearing an inertial sensor on their posterior trunk that measured trunk linear acceleration. Our results suggested that objective sway measures deteriorated over one year despite minimal changes in UPDRS motor scores. Medio-lateral (ML) sway measures were more sensitive than antero-posterior sway measures in detecting progression. The ML JERK was larger in the PD group than the control group across all three testing sessions. The ML sway dispersion and ML sway velocity were also significantly higher in PD compared to control subjects by the 12-month evaluation. It is feasible to measure progression of PD prior to onset of treatment using accelerometer-based measures of quiet standing.

ANTICIPATORY POSTURAL ADJUSTMENTS PRIOR TO STEP INITIATION ARE HYPOMETRIC IN UNTREATED PARKINSON'S DISEASE: AN ACCELEROMETER-BASED APPROACH

Background and purpose:u2002 Anticipatory postural adjustments (APAs), prior to step initiation, are bradykinetic in advanced Parkinson’s disease (PD) and may be one of the factors associated with ‘start hesitation’. However, little is known about APAs in the early stage of PD. In this study, we determined whether body‐worn accelerometers could be used to characterize step initiation deficits in subjects with early‐to‐moderate, untreated PD.

Impaired trunk stability in individuals at high risk for Parkinson's disease

Background The search for disease-modifying treatments for Parkinsons disease advances, however necessary markers for early detection of the disease are still lacking. There is compelling evidence that changes of postural stability occur at very early clinical stages of Parkinsons disease, making it tempting to speculate that changes in sway performance may even occur at a prodromal stage, and may have the potential to serve as a prodromal marker for the disease. Methodology/Principal Findings Balance performance was tested in 20 individuals with an increased risk of Parkinsons disease, 12 Parkinsons disease patients and 14 controls using a cross-sectional approach. All individuals were 50 years or older. Investigated groups were similar with respect to age, gender, and height. An accelerometer at the centre of mass at the lower spine quantified sway during quiet semitandem stance with eyes open and closed, as well as with and without foam. With increasing task difficulty, individuals with an increased risk of Parkinsons disease showed an increased variability of trunk acceleration and a decrease of smoothness of sway, compared to both other groups. These differences reached significance in the most challenging condition, i.e. the eyes closed with foam condition. Conclusions/Significance Individuals with an increased risk of Parkinsons disease have subtle signs of a balance deficit under most challenging conditions. This preliminary finding should motivate further studies on sway performance in individuals with an increased risk of Parkinsons disease, to evaluate the potential of this symptom to serve as a biological marker for prodromal Parkinsons disease.

Exploring outcome measures for exercise intervention in people with Parkinson's disease.

Background. It is widely believed that exercise improves mobility in people with Parkinsons disease (PD). However, it is difficult to determine whether a specific type of exercise is the most effective. The purpose of this study was to determine which outcome measures were sensitive to exercise intervention and to explore the effects of two different exercise programs for improving mobility in patients with PD. Methods. Participants were randomized into either the Agility Boot Camp (ABC) or treadmill training; 4x/week for 4 weeks. Outcome measures were grouped by the International Classification of Function/Disability (ICF). To determine the responsiveness to exercise, we calculated the standardized response means. t-tests were used to compare the relative benefits of each exercise program. Results. Four of five variables at the structure/function level changed after exercise: turn duration (P = 0.03), stride velocity (P = 0.001), peak arm speed (P = 0.001), and horizontal trunk ROM during gait (P = 0.02). Most measures improved similarly for both interventions. The only variable that detected a difference between groups was postural sway in ABC group (F = 4.95; P = 0.03). Conclusion. Outcome measures at ICF body structure/function level were most effective at detecting change after exercise and revealing differences in improvement between interventions.

The age-related changes of trunk responses to Achilles tendon vibration

The contribution of different sensory modalities to balance control is modified by age. Postural responses to Achilles tendon vibration were investigated in order to understand the influence of age on proprioceptive input from lower legs in human stance. Postural responses to bilateral vibrations of Achilles tendon with 10s duration were recorded at three frequencies (40, 60 and 80 Hz) in 9 healthy young (range, 24-27 years) and in 9 healthy older adults (59-70 years). Subjects were instructed to keep standing on firm surface with eyes closed. They performed three trials in each of three vibration frequencies. Postural responses were characterized by displacement of the centre of foot pressure (CoP) and by kinematics of body segments in the anterior-posterior direction. Bilateral vibrations of Achilles tendon induced backward body lean increasing with frequency of vibration and with age. The leg angle response to vibration was found similar in both groups of subjects. Slight trunk tilts from vertical position were induced by vibration in young subjects while in older subjects the trunk tilted backward together with the whole body. This observation was supported also by the minimal change of hip angle in older subjects contrary to increased hip activity in young subjects. The findings showed that the trunk and hip angle responses to proprioceptive stimulation might be a good indicator of age-related destabilization in balance control.

Improvement of balance after audio-biofeedback

Progressive supranuclear palsy (PSP) is a neurodegenerative disease with no sufficient treatment options to date. The most devastating symptom is the loss of balance with consecutive falls. Based on the observation that postural control improved in patients with vestibular dysfunction after audio-biofeedback training, we tested the effects of this training in PSP patients. Eight PSP patients were included into an uncontrolled 6-week intervention trial. The focus of the training was the improvement of posture and dynamic balance by using audio-biofeedback. The device was well accepted. No adverse events occurred. A significant improvement in the Berg Balance Scale was observed (T2 vs. T1, p=0.016), which remained significant at the 4-week follow-up (T3 vs. T1, p=0.008). Significant improvement of the Parkinson’s disease questionnaire was demonstrated. No significant changes were found in the Timed Up-and-Go Test, the Five Chair Rise Test, and in specific clinical scales. To our knowledge, the present study is the first to demonstrate that audio-biofeedback training with PSP patients is associated with improvements of balance and psychosocial aspects.ZusammenfassungProgressive supranukleäre Blickparese (PSP) ist eine neurodegenerative Erkrankung, für die es zurzeit noch keine geeigneten Behandlungsmethoden gibt. Der Verlust der Gleichgewichtsfähigkeit und die daraus resultierenden Stürze sind die Hauptsymptome. Ausgehend von einer Studie, die eine Verbesserung der Gleichgewichtsfähigkeit nach einem Audiobiofeedback- (ABF-)Training bei Patienten mit beidseitigem Vestibularisausfall zeigte, überprüften wir, ob dieser Effekt auch bei PSP-Patienten nachweisbar ist. Acht PSP-Patienten wurden in eine nichtkontrollierte 6-wöchige Interventionsstudie eingeschlossen. Ziel des Trainings war die Verbesserung der Haltung und des dynamischen Gleichgewichts mithilfe von ABF. Das Gerät wurde gut akzeptiert. Die Berg-Balance-Skala zeigte eine Verbesserung (T2 vs. T1, p=0,016), die auch beim Follow-up nachweisbar war (T3 vs. T1, p=0,008). Auch im Parkinson’s Disease Questionnaire ließen sich Verbesserungen finden. Der Timed Up-and-Go Test, der Five Chair Rise Test und spezifische klinische Einschätzungen ergaben keine signifikanten Veränderungen. Unseres Wissens ist dies die erste Studie mit PSP-Patienten, die durch ein ABF-Training Verbesserungen des Gleichgewichts und psychosozialer Aspekte zeigt.