According to the 2018 consensus report on the diagnosis and management of spinal muscular atrophy published by the SMA Care Group, physical therapy is an important part of the care of patients with SMA.1 Indeed, regular sessions of physical therapy may influence the trajectory of disease progression. In children with type II and type III SMA, regular physical therapy blunted the progression in most treated patients.2 While some form of physical therapy is recommended for most children with SMA and is associated with possible benefit, there is a general lack of evidence-based guidelines suggesting which physical therapy regimen is most advantageous, or the optimal duration and frequency of such treatments. Consequently, physical therapists are often left to formulate highly individualized treatment plans for their patients with SMA. Fortunately, there are some broad treatment principles to guide this effort.
Initial and periodic evaluation is necessary for understanding the child’s current performance status, constructing a targeted treatment plan, and tracking treatment success, failure, or disease progression. Determining muscle weakness is the most important assessment regardless of the patient’s ability to walk or sit. In non-ambulatory patients, postural control assessments are also quite important. For children who are unable to sit, the CHOP INTEND evaluation system is generally the most helpful. In non-ambulatory sitters, HFMSE is probably best, and in ambulatory patients some sort of timed test of function (e.g. 6-minute walk test) is considered the most useful.1,3
Cure SMA provides practical resources for PT and OT treatment in children with SMA. Physical therapists that treat children with SMA generally focus on strength, stretch, sit, walk, posture, and balance. The importance of strength building exercises cannot be understated since the consequences of muscle weakness can have a number of negative consequences. Children with muscle weakness find it difficult to move. Thus, without external prompting, they tend not to move. Muscles that do not get used tend to get weaker. Muscle weakness and inactivity can interfere with breathing, limit proper posture, and cause muscle tightness and painful joint contractures. Therefore, one reasonable approach is to determine which muscles are weak and to target those muscles and muscle groups with strengthening exercise. However, there are some specific caveats to consider. According to consensus statements, muscles with antigravity strength can be strengthened through resistance exercises.1 On the other hand, muscles with less than antigravity strength should not be subjected to eccentric exercises. Importantly, resistance exercises should not be used on neck muscles.
Flexibility and stretch are important issues for children with SMA. Muscle weakness makes it difficult to move in and out of positions, which means children tend to stay in certain positions for extended periods. This can cause cramping and further limit flexibility. When SMA affects opposing muscles differently, patients may have moderate to severe imbalance. Physical therapists should prioritize muscles that require flexibility exercises. Two reasonable goals are to maintain functional range of motion in all major muscle groups, and attempt to gain a symmetrical flexibility in various anatomical planes.
Stretching may be accomplished by using bracing, standers, and active-assisted stretching. If the goal is to maintain length, hold the stretch at the end range for at least 60 seconds. However, if the goal is to improve length, standers or bracing should be used for at least 60 min. per session. Ideally, patients would use braces or standers 5 to 7 times a week, but at a minimum, these should devices should be used at least three days a week.
Physical therapy interventions intended to promote sitting, walking, posture, and balance obviously must be scaled to the capabilities of the child. Non-sitters may be able to tolerate seating systems with postural supports. Likewise, non-sitters can participate safely in aquatic therapy if their head and neck are properly supported and they are under constant supervision.1 Non-ambulatory sitters may be able to participate in aquatic therapy, concentric and eccentric exercise, aerobic and general conditioning exercises with and without resistance.1 Ambulatory patients (i.e. walkers) may employ the same exercises as sitters, with the addition of balance and gait exercises.
1. Mercuri E, Finkel RS, Muntoni F, et al. Diagnosis and Management of Spinal Muscular Atrophy: Part 1: Recommendations for Diagnosis, Rehabilitation, Orthopedic and Nutritional Care. Neuromuscul Disord. 2018;28(2):103-115. doi:10.1016/j.nmd.2017.11.005
2. Mercuri E, Finkel R, Montes J, et al. Patterns of Disease Progression in Type 2 and 3 Sma: Implications for Clinical Trials. Neuromuscular Disorders. 2016;26(2):126-131. doi:10.1016/j.nmd.2015.10.006
3. Finkel RS, Sejersen T, Mercuri E, et al. 218th Enmc International Workshop:: Revisiting the Consensus on Standards of Care in Sma Naarden, the Netherlands, 19–21 February 2016. Neuromuscular Disorders. 2017;27(6):596-605.