• J Montes, M P McDermott, W B Martens, S Dunaway, A M Glanzman, S Riley, J Quigley, M J Montgomery, D Sproule, R Tawil, W K Chung, B T Darras, D C De Vivo, P Kaufmann, R S Finkel, and Muscle Study Group and the Pediatric Neuromuscular Clinical Research Network.
• SMA Clinical Research Center, Department of Neurology, Columbia University, 180 Ft. Washington Ave., 5th Floor, New York, NY 10032, USA. jm598@columbia.edu
• Neurology. 2010 Mar 9; 74 (10): 833-8.

BackgroundIn spinal muscular atrophy (SMA), weakness, decreased endurance, and fatigue limit mobility. Scales have been developed to measure function across the wide spectrum of disease severity. However, these scales typically are observer dependent, and scores are based on sums across Likert-scaled items. The Six-Minute Walk Test (6MWT) is an objective, easily administered, and standardized evaluation of functional exercise capacity that has been proven reliable in other neurologic disorders and in children.MethodsTo study the performance of the 6MWT in SMA, 18 ambulatory participants were evaluated in a cross-sectional study. Clinical measures were 6MWT, 10-m walk/run, Hammersmith Functional Motor Scale-Expanded (HFMSE), forced vital capacity, and handheld dynamometry. Associations between the 6MWT total distance and other outcomes were analyzed using Spearman correlation coefficients. A paired t test was used to compare the mean distance walked in the first and sixth minutes.ResultsThe 6MWT was associated with the HFMSE score (r = 0.83, p < 0.0001), 10-m walk/run (r = -0.87, p < 0.0001), and knee flexor strength (r = 0.62, p = 0.01). Gait velocity decreased during successive minutes in nearly all participants. The average first minute distance (57.5 m) was significantly more than the sixth minute distance (48 m) (p = 0.0003).ConclusionThe Six-Minute Walk Test (6MWT) can be safely performed in ambulatory patients with spinal muscular atrophy (SMA), correlates with established outcome measures, and is sensitive to fatigue-related changes. The 6MWT is a promising candidate outcome measure for clinical trials in ambulatory subjects with SMA.

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