Ashwini K. Rao

Spectrum of gait impairments in presymptomatic and symptomatic Huntington's disease.

The purpose of this study was to quantify gait impairments in presymptomatic and symptomatic Huntingtons disease (HD) subjects, and examine sensitivity of gait measures. Our sample (n = 65) included presymptomatic mutation carriers (PMC) (n = 15), symptomatic HD subjects (SHD) (n = 30) and healthy controls (n = 20). Participants were requested to walk at their preferred speed on a computerized walkway that recorded spatiotemporal variables. We administered the Unified HD Rating Scale (UHDRS) for PMC and SHD. PMC demonstrated decreased gait velocity (P < 0.01), stride length (P < 0.008), and increased time in double support (P < 0.001); and demonstrated higher variability in stride length (P < 0.01) and step time (P < 0.004) compared with controls. These impairments worsened with increasing disease severity for SHD. Gait impairments were correlated with predicted years to onset in PMC (velocity = −0.65; cadence = −0.70, step time = 0.71) and demonstrated high sensitivity and specificity in distinguishing between controls and mutation carriers. In contrast, UHDRS scores did not reveal impairments in gait and balance. Gait bradykinesia and dynamic balance impairments begin in the presymptomatic stage of HD and continue to worsen in the symptomatic stages. Gait measures are sensitive in differentiating between mutation positive and negative individuals even when impairments were not detected by clinical neurological examination.

Reliability of spatiotemporal gait outcome measures in Huntington's disease

Gait impairments are very important in Huntingtons disease (HD), because loss of independence in gait is an important predictor of nursing home placement. Given this importance, it is imperative to test reliable and sensitive outcome measures that can be tested easily in various clinical environments. Here, we examined the test–retest reliability of gait outcome measures using the GAITRite instrumented carpet. We tested 12 subjects with HD and 12 age‐matched controls in two separate sessions. At each session, subjects walked across the GAITRite carpet at a comfortable speed. We used the intraclass correlation coefficient (ICC) and coefficient of variation (CoV) to measure test–retest reliability. Reliability was very high for all outcome measures (velocity, cycle time, stride length, cadence, and base of support), as seen by high ICC scores (0.86 to 0.95) and low CoV scores (0.042–0.102). In addition, the performance across the two subject groups was very different, indicating that the GAITRite is sensitive enough to distinguish between populations. Given that the GAITRite is a relatively inexpensive and portable piece of equipment, it can be used in a wide variety of clinical settings and clinical trials. Our data on high test–retest reliability and sensitivity extends the utility of the GAITRite to the HD population.

Tandem gait performance in essential tremor: clinical correlates and association with midline tremors.

Gait difficulty has been reported in essential tremor (ET) although it has been the subject of a limited number of studies. We broadly assessed these clinical correlates, including the association of gait difficulty with a variety of midline tremors (jaw, voice, neck). Tandem gait (10 steps) was assessed in 122 ET cases. Cranial tremor score (0–3) was the number of locations (neck, jaw, voice) in which tremor was present. Number of tandem mis‐steps positively correlated with age (P < 0.001), age of tremor onset (P = 0.001), and presence of neck (P < 0.001), jaw (P = 0.001), and voice tremors (P = 0.047). Number of tandem mis‐steps increased markedly with cranial tremor score: 0 (0.8 ± 1.2), 1 (1.1 ± 1.6), 2 (2.3 ± 3.0), 3 (3.7 ± 1.6) (P < 0.001). It was not correlated with severity of arm or leg tremors. ET patients with cranial tremors (neck, jaw, voice), those with older age of onset, and those of current older age are more likely to manifest tandem gait difficulty. Tandem gait difficulty was not correlated with severity of limb tremors. Tandem gait difficulty and cranial tremors in ET may both be symptomatic of the same underlying pathophysiology, a disturbance of cerebellar regulation of the midline, which is distinct from its regulation of the limbs.

Contribution of tactile information to accuracy in pointing movements

Abstract. We examined the contribution of tactile cues to accuracy during point-to-point movements. We used a task in which the experimenter guided either the left or right hand of the subject to a spatial location during the reference movement. During the subsequent test movement subjects were asked to point with the right hand to the remembered location without vision. Subjects contacted the target with their fingertip either during the reference movement, both the reference and test movements, or neither movement (i.e., the fingertip was held above the target surface). To differentiate between the contribution of tactile and proximal deep pressure information, the left index finger was anesthetized in a subsequent experiment. When subjects contacted the surface with the fingertip of the reference hand alone, error in movement direction decreased. When subjects made fingertip contact during the reference and test movements, gain error also decreased. Anesthesia of the fingertip degraded accuracy, suggesting that tactile information, independent of information from proximal deep pressure receptors, influenced movement accuracy. Thus, tactile information contributed to accuracy in pointing movements. We suggest that forces at fingertip contact may provide information regarding the orientation of the finger and forearm in space, which is used to replicate final arm posture. In addition, tactile cues at the beginning and end of the movement may be used to scale movement amplitude.

Quantitative gait analysis in essential tremor reveals impairments that are maintained into advanced age

BACKGROUND Essential tremor (ET) patients seem to have impaired gait and balance, yet surprisingly few studies have utilized quantitative analysis to study these impairments. With one exception, these prior studies examined gait on a treadmill, which does not approximate functional environmental conditions (level ground). Moreover, these studies tested middle-aged subjects so it remains unclear whether ET patients maintain a pattern of deficits that is in excess of that seen in controls, even into advanced ages. METHODS 104 ET subjects (86.0±4.6, range=75-97 years) and 40 similarly aged controls (84.1±4.2, range=74-94 years) underwent gait testing using the GAITRite mat under standard walk and tandem walk conditions on level ground. RESULTS In standard walk, ET patients demonstrated deficits related to gait speed (lower velocity and cadence, p=0.0001), dynamic imbalance (increased double support percent, p=0.01), and gait asymmetry (increased step time difference, p=0.003). During tandem walk, ET patients had lower velocity (p=0.002) and cadence (p=0.003), and more mis-steps (p<0.008) compared with controls. For all variables, ET patients performed more poorly than controls even into advanced ages, as demonstrated in linear regression models. CONCLUSIONS ET patients demonstrated decrement in gait speed, dynamic balance and gait symmetry during standard walk and clear balance impairment during tandem walk. This constellation of impairments is consistent with a cerebellar deficit. ET patients maintained this pattern of deficits, in excess of that seen in controls, into advanced age, reinforcing the importance of gait and balance impairment in this disorder.

Systematic review of the effects of exercise on activities of daily living in people with Alzheimer's disease.

OBJECTIVE. Alzheimers disease (AD) results in a loss of independence in activities of daily living (ADLs), which in turn affects the quality of life of affected people and places a burden on caretakers. Limited research has examined the influence of physical training (aerobic, balance, and strength training) on ADL performance of people with AD. METHOD. Six randomized controlled trials (total of 446 participants) fit the inclusion criteria. For each study, we calculated effect sizes for primary and secondary outcomes. RESULTS. Average effect size (95% confidence interval) for exercise on the primary outcome (ADL performance) was 0.80 (p < .001). Exercise had a moderate impact on the secondary outcome of physical function (effect size = 0.53, p = .004). CONCLUSION. Occupational therapy intervention that includes aerobic and strengthening exercises may help improve independence in ADLs and improve physical performance in people with AD. Additional research is needed to identify specific components of intervention and optimal dosage to develop clinical guidelines.

Clinical measurement of mobility and balance impairments in Huntington's disease: validity and responsiveness.

BACKGROUND Mobility and balance in Huntingtons disease (HD) are currently assessed in the clinic with three items from the unified Huntingtons disease rating scale (UHDRS): walk, tandem and pull tests. These tests may not be optimal because they are scored on an ordinal scale and do not test anticipatory balance. We tested the validity and responsiveness of three clinical tests of mobility and balance. METHODS Three clinical tests (FRT, timed up and go (TUG), Berg balance scale (BBS)) were validated with seven quantitative gait measures and two indicators of functional limitation (HD-ADL and total functional capacity) in 30 subjects with HD. These tests were also assessed for responsiveness to disease severity. RESULTS FRT and BBS were correlated with five quantitative gait measures, and TUG with eight (all p<0.05). All tests were correlated with indicators of functional limitation (p<0.05) and were responsive to disease severity. CONCLUSIONS FRT, TUG and BBS are valid, responsive and easy to administer clinical tests that should be routinely included with the UHDRS in therapeutic trials for subjects with HD.

Weakness and Fatigue in Diverse Neuromuscular Diseases

Weakness and fatigue are captured by the 6-minute walk test, but the relationship between these symptoms is uncertain. Comparison across neuromuscular diseases has not been examined. A cohort study of 114 patients with spinal muscular atrophy, Duchenne/Becker muscular dystrophy, myasthenia gravis, and energy failure syndromes were included. Percent-predicted distance on the 6-minute walk test was computed from normative values to determine weakness. Fatigue was determined by the decrement in distance from the first to sixth minute. Weakness was seen across all groups (61.9%) but significant fatigue was seen only in spinal muscular atrophy (21.0%). Other groups showed little fatigue. Correlation between weakness and fatigue was significant only in spinal muscular atrophy (R = –0.71; P < .001). Longitudinally, distance walked declined only in Duchenne/Becker muscular dystrophy. In spinal muscular atrophy, weakness did not change, but fatigue increased significantly. These findings suggest independent mechanisms underlying weakness and fatigue in diverse neuromuscular conditions.

Fatigue leads to gait changes in spinal muscular atrophy.

Introduction: Impaired mobility and fatigue are common in ambulatory spinal muscular atrophy (SMA) patients. The 6‐minute walk test (6MWT) is a reliable measure of fatigue in SMA patients. To further evaluate fatigue, we used quantitative gait analysis during the 6MWT. Methods: Nine subjects with SMA and 9 age‐ and gender‐matched, healthy controls were evaluated. Gait parameters of speed and dynamic balance were correlated with 6MWT distance. Performance during the first and last 25 meters of the 6MWT was compared. Results: Speed‐related gait parameters and support base correlated with 6MWT distance. Walking performance was worse for SMA patients. The deterioration in stride length during the 6MWT was greater in SMA patients than in controls. Conclusions: Gait analysis detects fatigue, and the decrement in stride length may reflect selective muscle involvement in SMA. Further understanding of the mechanisms underlying fatigue may suggest additional targets for future therapeutic interventions. Muscle Nerve, 2010

Enabling functional independence in Parkinson's disease: Update on occupational therapy intervention

Motor impairment and functional limitations are known sequelae of Parkinsons disease. Occupational therapy (OT) is recognized as an important adjunct to pharmacological management. This critical review provides an update on the effectiveness of OT. Eight studies were included in the review, three on occupational therapy task‐related training, two on functional training with external cues and three on OT as part of interdisciplinary treatment. Due to lack of level I studies, it is difficult to determine conclusively the effect of OT. However, there is evidence to suggest that treatment produces improvements in motor and quality of life for the duration of therapy. Implications for future studies and practice are discussed.