Quantitative description of upper extremity function and activity of people with spinal muscular atrophy.
BACKGROUND
Therapeutic management of the upper extremity (UE) function of people with spinal muscular atrophy (SMA) requires sensitive and objective assessment. Therefore, we aimed to measure physiologic UE function of SMA patients with different functional abilities and evaluate the relation between these physiologic measures and functional UE scales.


METHODS
12 male and 5 female SMA patients (mean age 42 years; range 6-62 years) participated in this explorative study. Concerning the physiologic level, the maximal muscle torque, the maximal and normalized surface electromyography (sEMG) amplitudes, and the maximal passive and active joint angles were measured. Concerning the activity level, the Performance of the Upper Limb (PUL) scale was used, and hand function was examined using the Nine-Hole Peg Test and the Timed Test of In-Hand Manipulation (TIHM).


RESULTS
Outcome measures that significantly related to the functional ability were: the PUL score (all dimensions); the finger to palm task of the Timed TIHM; biceps, triceps, and forearm extensor strength; and the active range of motion of shoulder abduction, shoulder flexion, and wrist extension. In addition, the following physiologic variables were related to the activity level (PUL score): hand function (the Nine-Hole Peg Test; Rs = - 0.61), the Timed TIHM (Rs = - 0.53), the maximal muscle torque (Rs = 0.74), the maximal sEMG amplitude (Rs = 0.79), and the maximal active joint angle (Rs = 0.88).


CONCLUSIONS
Muscle functions in SMA patients are already affected before activity limitations are noticeable. Consequently, monitoring the maximal muscle strength and the normalized muscle activity during task performance could play a role in the early detection of UE limitations. The mechanism behind the loss of arm activities due to SMA is primarily caused by decreasing muscle capacity, which influences the ability to move an arm actively. In clinical practices, these dimensions should be considered separately when monitoring disease progression in order to better evaluate the need for interventions.
['Janssen|Mariska M H P|MMHP|0000-0003-2715-6235', 'Peeters|Laura H C|LHC|', 'de Groot|Imelda J M|IJM|']
D000293:Adolescent D000328:Adult D002648:Child D004576:Electromyography D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D053580:Muscle Strength D018482:Muscle, Skeletal D009134:Muscular Atrophy, Spinal D016059:Range of Motion, Articular D034941:Upper Extremity D055815:Young Adult
Spinal muscular atrophy Muscle torque Surface electromyography Upper limb Range of motion 3D motion analysis