Anna Maria Turcato

Comparison of Reliability, Validity, and Responsiveness of the Mini-BESTest and Berg Balance Scale in Patients With Balance Disorders

Background Recently, a new tool for assessing dynamic balance impairments has been presented: the 14-item Mini-BESTest. Objective The aim of this study was to compare the psychometric performance of the Mini-BESTest and the Berg Balance Scale (BBS). Design A prospective, single-group, observational design was used in the study. Methods Ninety-three participants (mean age=66.2 years, SD=13.2; 53 women, 40 men) with balance deficits were recruited. Interrater (3 raters) and test-retest (1–3 days) reliability were calculated using intraclass correlation coefficients (ICCs). Responsiveness and minimal important change were assessed (after 10 sessions of physical therapy) using both distribution-based and anchor-based methods (external criterion: the 15-point Global Rating of Change [GRC] scale). Results At baseline, neither floor effects nor ceiling effects were found in either the Mini-BESTest or the BBS. After treatment, the maximum score was found in 12 participants (12.9%) with BBS and in 2 participants (2.1%) with Mini-BESTest. Test-retest reliability for total scores was significantly higher for the Mini-BESTest (ICC=.96) than for the BBS (ICC=.92), whereas interrater reliability was similar (ICC=.98 versus .97, respectively). The standard error of measurement (SEM) was 1.26 and the minimum detectable change at the 95% confidence level (MDC95) was 3.5 points for Mini-BESTest, whereas the SEM was 2.18 and the MDC95 was 6.2 points for the BBS. In receiver operating characteristic curves, the area under the curve was 0.92 for the Mini-BESTest and 0.91 for the BBS. The best minimal important change (MIC) was 4 points for the Mini-BESTest and 7 points for the BBS. After treatment, 38 participants evaluated with the Mini-BESTest and only 23 participants evaluated with the BBS (out of the 40 participants who had a GRC score of ≥3.5) showed a score change equal to or greater than the MIC values. Limitations The consecutive sampling method drawn from a single rehabilitation facility and the intrinsic weakness of the GRC for calculating MIC values were limitations of the study. Conclusions The 2 scales behave similarly, but the Mini-BESTest appears to have a lower ceiling effect, slightly higher reliability levels, and greater accuracy in classifying individual patients who show significant improvement in balance function.

Test-retest reliability of an insole plantar pressure system to assess gait along linear and curved trajectories

BackgroundPrevious studies have assessed reliability of insole technology for evaluating foot pressure distribution during linear walking. Since in natural motion straight walking is intermingled with turns, we determined the test-retest reliability of insole assessment for curved as well as linear trajectories, and estimated the minimum number of steps required to obtain excellent reliability for each output variable.MethodsSixteen young healthy participants were recruited. Each performed, two days apart, two sessions of three walking conditions: linear (LIN) and curved, clockwise (CW) and counter-clockwise (CCW). The Pedar-X system was used to collect pressure distribution. Foot print was analyzed both as a whole and as subdivided into eight regions: medial and lateral heel, medial and lateral arch, I metatarsal head, II-V metatarsal heads, hallux, lateral toes. Reliability was assessed by using intraclass correlation coefficient (ICC) for clinically relevant variables from analysis of 50 steps per trajectory: Peak Force (PF); Peak Pressure (PP); Contact Area (CA); Stance Duration (S).ResultsWhen considering whole-foot, all variables showed an ICC >0.80, therefore highly reliable. This was true for both LIN and curved trajectories. There was no difference in ICC of the four variables between left and right foot. When collapsing foot and trajectories, S had a lower ICC than PP and CA, and PP lower than CA. Mean percent error between the values of first and second session was <5%. When separately considering the eight foot regions, ICCs of PF, PP and CA for all regions and trajectories were generally >0.90, indicating excellent reliability. In curved trajectories, S showed smaller ICCs. Since the least ICC value for S was 0.60 in LIN trajectory, we estimated that to achieve an ICC ≥0.90 more than 200 steps should be collected.ConclusionsHigh reliability of insole dynamic variables (PF, PP, CA) is obtained with 50 steps using the Pedar-X system. On the contrary, high reliability of temporal variable (S) requires a larger step number. The negligible differences in ICC between LIN and curved trajectory allow use of this device for gait assessment along mixed trajectories in both clinical and research setting.

Afferent control of walking: Are there distinct deficits associated to loss of fibres of different diameter?

OBJECTIVES To compare the gait pattern in patients affected by different types of neuropathy. METHODS We recruited healthy subjects (HS, n=38), patients with Charcot-Marie-Tooth disease type 1A (CMT1A) (n=10) and patients with diabetic neuropathy (DNP) (n=12). Neuropathy impairment score and neuropathy score were assessed. Body sway during quiet stance, and spatio-temporal gait parameters were recorded. RESULTS Most patients had reduced or absent tendon-tap reflexes. Strength of foot dorsiflexor muscles (p<0.05) and conduction velocity (CV) of leg nerves (p<0.0001) were more impaired in CMT1A than DNP, whereas joint-position sense was more affected (p<0.05) in DNP. Body sway while standing was larger in DNP compared to CMT1A and HS (p<0.01 and p<0.0001 respectively). During gait, the distribution of foot sole contact pressure was abnormal in CMT1A (p<0.05) but not in DNP. Velocity and step length were decreased, and foot yaw angle at foot flat increased, in DNP with respect to CMT1A and HS (both variables, p<0.001). Gait velocity and step length were decreased (p<0.005) also in CMT1A, but to a smaller extent than in DNP, so that the difference between patient groups was significant (p<0.0005). Duration of the double support was protracted in DNP compared to CMT1A and HS (p<0.0005). For DNP only, velocity of gait and duration of single support were correlated (p<0.05) both to sway path and lower limb muscle strength. CONCLUSIONS Changes in both body sway and stance phase of gait were larger in DNP than CMT1A, indicating more impaired static and dynamic control of balance when neuropathy affects the small in addition to the large afferent fibres. Diminished somatosensory input from the smaller fibres rather than muscle weakness or foot deformity plays a critical role in the modulation of the support phase of gait. SIGNIFICANCE The analysis of balance and gait in patients with neuropathy can offer a tool for understanding the nature and functional impact of the neuropathy and should be included in their functional evaluation.

The generation of centripetal force when walking in a circle: insight from the distribution of ground reaction forces recorded by plantar insoles.

BackgroundTurning involves complex reorientation of the body and is accompanied by asymmetric motion of the lower limbs. We investigated the distribution of the forces under the two feet, and its relation to the trajectory features and body medio-lateral displacement during curved walking.MethodsTwenty-six healthy young participants walked under three different randomized conditions: in a straight line (LIN), in a circular clockwise path and in a circular counter-clockwise path. Both feet were instrumented with Pedar-X insoles. An accelerometer was fixed to the trunk to measure the medio-lateral inclination of the body. We analyzed walking speed, stance duration as a percent of gait cycle (%GC), the vertical component of the ground reaction force (vGRF) of both feet during the entire stance, and trunk inclination.ResultsGait speed was faster during LIN than curved walking, but not affected by the direction of the curved trajectory. Trunk inclination was negligible during LIN, while the trunk was inclined toward the center of the path during curved trajectories. Stance duration of LIN foot and foot inside the curved trajectory (Foot-In) was longer than for foot outside the trajectory (Foot-Out). vGRF at heel strike was larger in LIN than in curved walking. At mid-stance, vGRF for both Foot-In and Foot-Out was higher than for LIN foot. At toe off, vGRF for both Foot-In and Foot-Out was lower than for LIN foot; in addition, Foot-In had lower vGRF than Foot-Out. During curved walking, a greater loading of the lateral heel occurred for Foot-Out than Foot-In and LIN foot. On the contrary, a smaller lateral loading of the heel was found for Foot-In than LIN foot. At the metatarsal heads, an opposite behaviour was seen, since lateral loading decreased for Foot-Out and increased for Foot-In.ConclusionsThe lower gait speed during curved walking is shaped by the control of trunk inclination and the production of asymmetric loading of heel and metatarsal heads, hence by the different contribution of the feet in producing the body inclination towards the centre of the trajectory.

A Personalized Multi-Channel FES Controller Based on Muscle Synergies to Support Gait Rehabilitation after Stroke

It has been largely suggested in neuroscience literature that to generate a vast variety of movements, the Central Nervous System (CNS) recruits a reduced set of coordinated patterns of muscle activities, defined as muscle synergies. Recent neurophysiological studies have recommended the analysis of muscle synergies to finely assess the patients impairment, to design personalized interventions based on the specific nature of the impairment, and to evaluate the treatment outcomes. In this scope, the aim of this study was to design a personalized multi-channel functional electrical stimulation (FES) controller for gait training, integrating three novel aspects: (1) the FES strategy was based on healthy muscle synergies in order to mimic the neural solutions adopted by the CNS to generate locomotion; (2) the FES strategy was personalized according to an initial locomotion assessment of the patient and was designed to specifically activate the impaired biomechanical functions; (3) the FES strategy was mapped accurately on the altered gait kinematics providing a maximal synchronization between patients volitional gait and stimulation patterns. The novel intervention was tested on two chronic stroke patients. They underwent a 4-week intervention consisting of 30-min sessions of FES-supported treadmill walking three times per week. The two patients were characterized by a mild gait disability (walking speed > 0.8 m/s) at baseline. However, before treatment both patients presented only three independent muscle synergies during locomotion, resembling two different gait abnormalities. After treatment, the number of extracted synergies became four and they increased their resemblance with the physiological muscle synergies, which indicated a general improvement in muscle coordination. The originally merged synergies seemed to regain their distinct role in locomotion control. The treatment benefits were more evident for one patient, who achieved a clinically important change in dynamic balance (Mini-Best Test increased from 17 to 22) coupled with a very positive perceived treatment effect (GRC = 4). The treatment had started the neuro-motor relearning process also on the second subject, but twelve sessions were not enough to achieve clinically relevant improvements. This attempt to apply the novel theories of neuroscience research in stroke rehabilitation has provided promising results, and deserves to be further investigated in a larger clinical study.

Effects of balance and gait rehabilitation in cerebellar disease of vascular or degenerative origin.

PURPOSE To investigate whether the response to rehabilitation differs between patients with abnormalities of balance and gait due to vascular or to degenerative cerebellar disease. METHODS We reviewed the outcome of 27 cerebellar patients. Fourteen patients with vascular and 13 with degenerative cerebellar disease underwent a 3-week inpatient physical therapy program for 5 days/week, 90 min/day, focused on balance and gait. Body sway area during quiet stance with eyes open and eyes closed, and gait velocity, stride length, cadence and step width were recorded. The Berg Balance Scale (BBS) and Functional Independence Measure (FIM) were administered. All tests were performed before and after treatment. RESULTS Before treatment, both groups showed comparable values in all sway and gait variables and in BBS. FIM score was higher in degenerative than vascular patients. After treatment, a significant reduction of body sway area was observed under both visual conditions in both groups. Gait velocity, stride length and step width improved more in the vascular than in the degenerative patient group. BBS improved in both groups. FIM improved to a larger extent in the vascular patients. CONCLUSION Short-term treatment may not be sufficient to produce definite improvement in locomotion in degenerative as much as occurs in vascular patients, even if clinical and functional signs of balance improve in both groups.

Curved Walking Rehabilitation with a Rotating Treadmill in Patients with Parkinson’s Disease: A Proof of Concept

Training subjects to step-in-place eyes open on a rotating platform while maintaining a fixed body orientation in space [podokinetic stimulation (PKS)] produces a posteffect consisting in inadvertent turning around while stepping-in-place eyes closed [podokinetic after-rotation (PKAR)]. Since the rationale for rehabilitation of curved walking in Parkinson’s disease is not fully known, we tested the hypothesis that repeated PKS favors the production of curved walking in these patients, who are uneasy with turning, even when straight walking is little affected. Fifteen patients participated in 10 training sessions distributed in 3 weeks. Both counterclockwise and clockwise PKS were randomly administered in each session. PKS velocity and duration were gradually increased over sessions. The velocity and duration of the following PKAR were assessed. All patients showed PKAR, which increased progressively in peak velocity and duration. In addition, before and at the end of the treatment, all patients walked overground along linear and circular trajectories. Post-training, the velocity of walking bouts increased, more so for the circular than the linear trajectory. Cadence was not affected. This study has shown that parkinsonian patients learn to produce turning while stepping when faced with appropriate training and that this capacity translates into improved overground curved walking.

Abnormal gait pattern emerges during curved trajectories in high-functioning Parkinsonian patients walking in line at normal speed

Background Several patients with Parkinson´s disease (PD) can walk normally along straight trajectories, and impairment in their stride length and cadence may not be easily discernible. Do obvious abnormalities occur in these high-functioning patients when more challenging trajectories are travelled, such as circular paths, which normally implicate a graded modulation in the duration of the interlimb gait cycle phases? Methods We compared a cohort of well-treated mildly to moderately affected PD patients to a group of age-matched healthy subjects (HS), by deliberately including HS spontaneously walking at the same speed of the patients with PD. All participants performed, in random order: linear and circular walking (clockwise and counter-clockwise) at self-selected speed. By means of pressure-sensitive insoles, we recorded walking speed, cadence, duration of single support, double support, swing phase, and stride time. Stride length-cadence relationships were built for linear and curved walking. Stride-to-stride variability of temporal gait parameters was also estimated. Results Walking speed, cadence or stride length were not different between PD and HS during linear walking. Speed, cadence and stride length diminished during curved walking in both groups, stride length more in PD than HS. In PD compared to HS, the stride length-cadence relationship was altered during curved walking. Duration of the double-support phase was also increased during curved walking, as was variability of the single support, swing phase and double support phase. Conclusion The spatio-temporal gait pattern and variability are significantly modified in well-treated, high-functioning patients with PD walking along circular trajectories, even when they exhibit no changes in speed in straight-line walking. The increased variability of the gait phases during curved walking is an identifying characteristic of PD. We discuss our findings in term of interplay between control of balance and of locomotor progression: the former is challenged by curved trajectories even in high-functioning patients, while the latter may not be critically affected.

An Overview of the Physiology and Pathophysiology of Postural Control

This chapter gives an overview of the role played by the postural control system in the production of postural tone, stability and orientation. Sensory inputs are integrated at the level of the central nervous system, and postural responses, that are generated by the spinal and supraspinal centers, can be selected according to prior experience, the degree of postural stabilization, and the environment. Since human upright stance is an unstable condition, several diseases affecting the peripheral and central nervous system can lead to different degrees of balance impairment. In order to create a link between physiology of postural control and disease, a brief description of the main pathophysiological mechanisms underlying abnormalities of the postural control system in common diseases of the nervous system is also given.