Perceived Fatigue in Spinal Muscular Atrophy: A Pilot Study.

BACKGROUND: Fatigue is a common complaint in spinal muscular atrophy (SMA). Fatigability is well described in ambulatory SMA but the relationship to perceived fatigue has not been evaluated. Understanding this relationship has proven challenging for most disorders. OBJECTIVE: To assess the relationship of perceived fatigue to fatigability, function, and quality of life in SMA. METHODS: Thirty-two participants with SMA (21.9% type 2, 78.1% type 3) were recruited. Perceived fatigue and fatigability, function, and quality of life were assessed using standardized questionnaires and assessments. Associations were analyzed using Pearson correlation coefficients (p = 0.05). Also, the effects of age, type, and ambulatory status were determined on perceived fatigue. RESULTS: All SMA participants reported fatigue. Perceived fatigue was not associated with function, quality of life, or fatigability in ambulatory SMA patients. Neither age, type, nor ambulatory status influenced perceived fatigue. CONCLUSIONS: Perceived fatigue can be quantified in SMA. Interestingly, perceived fatigue did not correlate with fatigability or function, suggesting that cognitive, homeostatic, or psychologic factors may be more relevant as co-morbid factors. Clinical trials targeting perceived fatigue in SMA should focus on these patient-reported assessments. A multilevel approach is required to separate the various mechanisms involved in perceived fatigue.

Six-minute walk test is reliable and valid in spinal muscular atrophy.

INTRODUCTION: The Six-Minute Walk Test (6MWT) was adopted as a clinical outcome measure for ambulatory spinal muscular atrophy (SMA). However, a systematic review of measurement properties reported significant variation among chronic pediatric conditions. Our purpose was to assess the reliability/validity of the 6MWT in SMA. METHODS: Thirty participants performed assessments, including the 6MWT, strength, and function. Reproducibility was evaluated by intraclass correlation coefficients. Criterion/convergent validity were determined using Pearson correlation coefficients. RESULTS: Test-retest reliability was excellent. The 6MWT was associated positively with peak oxygen uptake, Hammersmith Functional Motor Scale Expanded (HFMSE), lower extremity manual muscle testing, knee flexion hand-held dynamometry, and inversely with 10-m walk/run. The 6MWT discriminates between disease severity, unlike the HFMSE. CONCLUSIONS: This study documents measurement properties of reproducibility, positive criterion validity, and convergent validity with established clinical assessments and reaffirms the value of the 6MWT as a pivotal outcome measure in SMA clinical trials. Muscle Nerve 54: 836-842, 2016.

Single-Blind, Randomized, Controlled Clinical Trial of Exercise in Ambulatory Spinal Muscular Atrophy: Why are the Results Negative?

BACKGROUND: The benefits of exercise on long-term health and well-being are well established. The possible benefits of exercise in Spinal Muscular Atrophy (SMA) have not been explored in a controlled clinical trial format. OBJECTIVE: To assess the effects of exercise on measures of function, strength, and exercise capacity in ambulatory SMA patients. METHODS: Fourteen participants, ages 10-48 years, were randomized to control and exercise cohorts after a 1 month lead-in period. The exercise group received 6 months of intervention. Thereafter, both groups received the intervention for the remaining 12 months. Participants were monitored for a total of 19 months. Exercise included individualized home-based cycling and strengthening. The primary outcome measure was distance walked during the six-minute walk test (6MWT). Secondary outcomes included strength, function, exercise capacity, quality of life and fatigue. RESULTS: Twelve participants completed the first 7 months of the study, and 9 completed all 19 months. At baseline, the groups were similar on all clinical variables. There were no group changes at any time point in the 6MWT, fatigue, or function. Percent-predicted VO2 max improved 4.9% in all participants in 6 months (p = 0.036) (n = 10). CONCLUSION: Daily exercise is safe in ambulatory SMA and should be encouraged. We did not uncover any deleterious effects on strength, function, or fatigue. Our study documented a reduction in oxidative capacity and a blunted conditioning response to exercise possibly representing an important insight into underlying pathophysiological mechanisms. These findings also may be linked causally to mitochondrial depletion in SMA and warrant further study.

A Randomized, Controlled Clinical Trial of Exercise in Patients with Spinal Muscular Atrophy: Methods and Baseline Characteristics.

BACKGROUND: Spinal Muscular Atrophy (SMA) is a recessively-inherited neuromuscular disease characterized by weakness and muscle atrophy. Although anecdotal benefits from exercise have been noted, and despite promising pre-clinical and pilot reports, the effect of exercise has not been addressed in a controlled trial in SMA. OBJECTIVE: To assess the effects of exercise on measures of function, strength, and exercise capacity in ambulatory SMA patients. METHODS/DESIGN: An evaluator-blinded, randomized, controlled trial of aerobic and strengthening exercise in 14 ambulatory SMA patients aged 8-50 years. Patients will be randomized to either the exercise or control arm after the 1 month lead in period. During the first 6-months, the exercise group will receive the intervention while the other group serves as a control. After those 6 months, both groups will receive the intervention. The last 6-months of the study are designed to mimic real-world conditions where all participants are encouraged to continue on their own. Participants will be monitored throughout this 19 month study and will have in-person visits every three months. The primary outcome measure is the change in the total distance walked over 6-months on the six minute walk test (6MWT). Secondary outcome measures include maximal oxygen uptake (VO2 max), functional and strength assessments, pulmonary function, fatigue, and quality of life. DISCUSSION: The result of this prospective, single blinded, randomized and controlled clinical trial of exercise on an established functional outcome measure will have impact on clinical practice by providing important guidance to clinical management of SMA patients.

Performance of the timed "up & go" test in spinal muscular atrophy.

INTRODUCTION: The timed "up & go" (TUG) test is a quick measure of balance and mobility. TUG scores correlate with clinical, functional, and strength assessment and decline linearly over time. Reliability and validity have not been tested in spinal muscular atrophy (SMA). METHODS: Fifteen ambulatory SMA participants performed TUG testing and strength, functional, and clinical assessments. Intraclass correlation coefficients quantified test-retest reliability. Convergent validity was determined using Pearson correlation coefficients. RESULTS: Test-retest reliability was excellent for all participants. TUG was associated significantly with total leg and knee flexor strength, as well as the Hammersmith Functional Motor Scale Expanded, the 10-meter walk/run, and 6-minute walk tests. TUG findings were not associated with knee extensor strength, pulmonary function, or fatigue. CONCLUSIONS: In SMA, the TUG test is easily administered, reliable, and correlates with established outcome measures. TUG testing is a potentially useful outcome measure for clinical trials and a measure of disability in ambulatory patients with SMA.