Kathleen E. Norman

Quantitative Assessment of Limb Position Sense Following Stroke

Background. Impairment of position sense of the upper extremity (UE) may impede activities of daily living and limit motor gains after stroke. Most clinical assessments of position sense rely on categorical or ordinal ratings by clinicians that lack sensitivity to change or the ability to discriminate subtle deficits. Objective. Use robotic technology to develop a reliable, quantitative technique with a continuous scale to assess UE position sense following stroke. Methods. Forty-five patients recruited from an inpatient stroke rehabilitation service and 65 age-matched healthy controls performed an arm position matching task. Each UE was fitted in the exoskeleton of a KINARM device. One UE was passively placed in one of 9 positions, and the subject was told to match his or her position with the other UE. Patients were compared with statistical distributions of control data to identify those with deficits in UE position sense. Test—retest sessions using 2 raters established interrater reliability. Results. Two thirds of left hemiparetic and one third of right hemiparetic patients had deficits in limb position sense. Left-affected stroke subjects demonstrated significantly more trial-to-trial variability than right-affected or control subjects. The robotic assessment technique demonstrated good interrater reliability but limited agreement with the clinical thumb localizing test. Conclusions. Robotic technology can provide a reliable quantitative means to assess deficits in limb position sense following stroke.

Effects of visual and auditory cues on gait initiation in people with Parkinson's disease

Objective: To evaluate the effects of auditory and visual cues on gait initiation in people with Parkinsons disease. Subjects: Fourteen subjects with Parkinsons disease were recruited from community support groups, seven of whom reported having experienced freezing when walking. Design and setting: This study was a repeated measures analysis of gait initiation performance during a single visit to a university-based motion laboratory. Following baseline trials, auditory and visual cue conditions were presented in random order. The auditory cues were rhythmic sounds with an interval matching the subjects average step time. The visual cues were high-contrast transverse lines on the floor adjusted for the subjects first step length and overall height. Main measures: Kinematic recordings enabled calculation of the timing and length of steps as well as overall velocity. The timing and magnitude of weight shift and push-off force were obtained from a force platform. Results: The magnitudes of first and second step lengths, of push-off force and of overall gait velocity were significantly greater in the visual cue condition than in the baseline condition, whereas there was no significant effect of auditory cue on these measures. Neither cue had any significant effect on the timing of key events in gait initiation. Conclusions: Transverse line visual cues enable people with Parkinsons disease to begin walking with longer steps, greater push-off force and higher velocity. Auditory cues that others have shown to improve aspects of gait in people with Parkinsons disease do not appear to have any systematic effect on the first two steps of gait initiation.

Assessment of Upper-Limb Sensorimotor Function of Subacute Stroke Patients Using Visually Guided Reaching

Objective. Using robotic technology, we examined the ability of a visually guided reaching task to assess the sensorimotor function of patients with stroke. Methods. Ninety-one healthy participants and 52 with subacute stroke of mild to moderate severity (26 with left- and 26 with right-affected body sides) performed an unassisted reaching task using the KINARM robot. Each participant was assessed using 12 movement parameters that were grouped into 5 attributes of sensorimotor control. Results. A number of movement parameters individually identified a large number of stroke participants as being different from 95% of the controls—most notably initial direction error, which identified 81% of left-affected patients. We also found interlimb differences in performance between the arms of those with stroke compared with controls. For example, whereas only 31% of left-affected participants showed differences in reaction time with their affected arm, 54% showed abnormal interlimb differences in reaction time. Good interrater reliability (r > 0.7) was observed for 9 of the 12 movement parameters. Finally, many stroke patients deemed impaired on the reaching task had been scored 6 or less on the arm portion of the Chedoke-McMaster Stroke Assessment Scale, but some who scored a normal 7 were also deemed impaired in reaching. Conclusions. Robotic technology using a visually guided reaching task can provide reliable information with greater sensitivity about a patient’s sensorimotor impairments following stroke than a standard clinical assessment scale.

A randomized controlled trial of the effects of weights on amplitude and frequency of postural hand tremor in people with Parkinson's disease:

Objective: To evaluate the effects of weights on postural hand tremor related to self-feeding in subjects with Parkinsons disease (PD). Design: In a repeated-measures design, postural hand tremor was recorded three times in each of three weight conditions in a single session for each subject. The order of all recording conditions was randomized. Setting: Intervention was applied and measurement was conducted in a university-based motor performance laboratory. Subjects: Fourteen men and two women diagnosed with PD and having hand tremor participated (mean age 67.1 years, mean duration of PD 4.6 years). All were community-dwelling. Intervention: The control condition consisted of holding a built-up spoon (108 g). There were two experimental conditions: holding a weighted spoon (248 g); and holding the built-up spoon while wearing a weighted wrist cuff (470 g). Main outcome measures: Three measures of tremor amplitude and two measures of tremor frequency were calculated from recordings of displacement of the spoon obtained from laser displacement sensors. Results: Repeated-measures analyses of variance revealed no signi”cant differences across conditions in any measure of tremor amplitude or in either measure of tremor frequency. Correlational and Mann–Whitney U-test analyses revealed that none of age, disease duration or medication intake had any signi”cant relationship with tremor amplitude in the control condition or with whether amplitude was altered by weights. Conclusions: The ”ndings suggest that there is no support for the clinical recommendation of using weighted utensils or weighted wrist cuffs to alleviate postural hand tremor in PD.

The effect of inertial loading on wrist postural tremor in essential tremor

OBJECTIVES Determine the effect of inertial loading on the strength of motor unit entrainment and the synergistic/competitive interaction between central and mechanical reflex tremor components in subjects with essential tremor (ET). METHODS Twenty-three subjects with ET and 22 controls held their hand in an outstretched position while supporting sub-maximal loads (no-load, 5%, 15% and 25% 1-repetition maximum). Hand postural tremor and wrist extensor neuromuscular activity were recorded. RESULTS Inertial loading resulted in a reduction in postural tremor in all ET subjects. The largest reduction in tremor amplitude occurred between 5% and 15% loads, which was associated with spectral separation of the mechanical reflex and central tremor components in a large number of ET subjects. Despite an increase in overall neuromuscular activity with inertial loading, EMG tremor spectral power did not increase with loading. CONCLUSIONS The effect of inertial loading on postural tremor amplitude appears to be mediated in large part by its effect on the interaction between mechanical reflex and central tremor components. Also, ET is associated with a constant absolute level of motor unit entrainment. SIGNIFICANCE The amplitude of postural tremor is dependent on both central and peripheral factors, with proportionally greater motor unit entrainment occurring at low contraction intensities.

Impaired corrective responses to postural perturbations of the arm in individuals with subacute stroke.

BackgroundStroke is known to alter muscle stretch responses following a perturbation, but little is known about the behavioural consequences of these altered feedback responses. Characterizing impairments in people with stroke in their interactions with the external environment may lead to better long term outcomes. This information can inform therapists about rehabilitation targets and help subjects with stroke avoid injury when moving in the world.MethodsIn this study, we developed a postural perturbation task to quantity upper limb function of subjects with subacute stroke (n = 38) and non-disabled controls (n = 74) to make rapid corrective responses with the arm. Subjects were instructed to maintain their hand at a target before and after a mechanical load was applied to the limb. Visual feedback of the hand was removed for half of the trials at perturbation onset. A number of parameters quantified subject performance, and impairment in performance was defined as outside the 95th percentile performance of control subjects.ResultsIndividual subjects with stroke showed increased postural instability (44%), delayed motor responses (79%), delayed returns towards the spatial target (79%), and greater endpoint errors (74%). Several subjects also showed impairments in the temporal coordination of the elbow and shoulder joints when responding to the perturbation (47%). Interestingly, impairments in task parameters were often found for both arms of individual subjects with stroke (up to 58% for return time). Visual feedback did not improve performance on task parameters except for decreasing endpoint error for all subjects. Significant correlations between task performance and clinical measures were dependent on the arm assessed.ConclusionsThis study used a simple postural perturbation task to highlight that subjects with stroke commonly have difficulties responding to mechanical disturbances that may have important implications for their ability to perform daily activities.

The effect of contraction intensity on force fluctuations and motor unit entrainment in individuals with essential tremor

OBJECTIVES Quantify the effect of increasing contraction intensity on the amplitude of force fluctuations and neuromuscular and force tremor spectral power. METHODS Twenty-one subjects with essential tremor (ET) and 22 healthy controls applied isometric wrist extension contractions. Various sub-maximal contraction intensities were evaluated (5%-, 10%-, 20%- and 30%-MVC). Force fluctuations and wrist extensor neuromuscular activity were recorded using a load cell and electromyography (EMG). RESULTS Higher contraction intensities were associated with larger amplitude force fluctuations and greater neuromuscular activation. However, spectral power associated with tremor peaks remained relatively constant (EMG) or decreased (force) with increasing contraction intensity. CONCLUSIONS Motor unit entrainment associated with centrally generated oscillatory inputs does not increase with greater levels of muscle activation. SIGNIFICANCE Rather than influencing a constant proportion of active motor units, abnormal oscillatory drive influences a relative constant number of total motor units. When combined with the findings from our previous study on postural tremor, the present results provide preliminary evidence that abnormal stretch reflex activity may contribute to this motor unit entrainment.

The effect of inertial loading on wrist kinetic tremor and rhythmic muscle activity in individuals with essential tremor

OBJECTIVES Determine the effect of concentric and eccentric movement and contraction intensity on the strength of rhythmic muscle activity in individuals with essential tremor (ET). METHODS 21 ET subjects and 22 healthy controls produced wrist flexion-extension movements while supporting sub-maximal loads (no-load, 5%, 15% and 25% 1-repetition maximum). Kinetic tremor and wrist extensor neuromuscular activity were recorded using an angular displacement sensor and electromyography (EMG). RESULTS Rhythmic muscle activity was twice as big during movement compared to previous results involving postural or isometric tasks. ET subjects with greater rhythmic muscle activity had (1) larger overall kinetic tremor amplitude, (2) greater tremor spectral power during eccentric compared to concentric movement and (3) a reduction in overall kinetic tremor amplitude and the percentage of EMG spectral power accounted for by the tremor spectral peak in the presence of inertial loading. CONCLUSIONS Greater than normal kinetic tremor amplitude appears to be limited to ET subjects with higher levels of rhythmic muscle activity. Furthermore, rhythmic muscle activity is much greater during movement compared to during postural or closed-kinetic tasks. SIGNIFICANCE The strength of rhythmic muscle activity in ET is influenced by the type of contraction (i.e., static vs. dynamic) being performed. Clinicians and researchers should include measures of simple kinetic tremor as part of their assessments.

Photovoice and Persons With Physical Disabilities: A Scoping Review of the Literature:

Photovoice is a group analysis method often affiliated with participatory action research (PAR). It has become increasingly popular in qualitative research with people with physical disabilities. This article details the results of a study that sought to understand the scope of the literature related to how photovoice is conducted with people with physical disabilities. We performed a scoping review related to use of photovoice in physical disabilities research. We identified 20 articles that featured diverse participants with physical disabilities and demonstrated a range of approaches to data collection, analysis, and dissemination. Nearly all of the articles identified used photovoice to study physical accessibility/navigation of space. Although a majority of selected articles purported to use PAR approaches, many articles demonstrated research that may not be as participatory as presumed. Based on the findings, we provide suggestions for photovoice studies that will ensure full and meaningful participation of members involved.

Measures of Fine Motor Skills in People with Tremor Disorders: Appraisal and Interpretation

People with Parkinson’s disease, essential tremor, or other movement disorders involving tremor have changes in fine motor skills that are among the hallmarks of these diseases. Numerous measurement tools have been created and other methods devised to measure such changes in fine motor skills. Measurement tools may focus on specific features – e.g., motor skills or dexterity, slowness in movement execution associated with parkinsonian bradykinesia, or magnitude of tremor. Less obviously, some tools may be better suited than others for specific goals such as detecting subtle dysfunction early in disease, revealing aspects of brain function affected by disease, or tracking changes expected from treatment or disease progression. The purpose of this review is to describe and appraise selected measurement tools of fine motor skills appropriate for people with tremor disorders. In this context, we consider the tools’ content – i.e., what movement features they focus on. In addition, we consider how measurement tools of fine motor skills relate to measures of a person’s disease state or a person’s function. These considerations affect how one should select and interpret the results of these tools in laboratory and clinical contexts.