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Upper extremity strength and function in children with spinal muscular atrophy type II
1Department of Physical Medicine and Rehabilitation, Children's National Medical Center, Washington, DC 20010-2970.
Insights
Children with spinal muscular atrophy type II have significantly reduced upper extremity strength, approximately 35-40% of normal. This muscle weakness, though stable over time, impacts their functional independence in daily activities.
Area of Science:
- Pediatric Neurology
- Rehabilitation Medicine
- Neuromuscular Disorders
Background:
- Spinal muscular atrophy (SMA) type II is a severe genetic disorder characterized by progressive muscle weakness.
- Understanding the functional capacity and strength deficits in children with SMA type II is crucial for developing targeted interventions.
- Limited data exist on the precise upper extremity strength and functional abilities in this specific pediatric population.
Purpose of the Study:
- To quantify upper extremity strength and functional abilities in children diagnosed with spinal muscular atrophy type II.
- To assess the stability of muscle strength over time in this cohort.
- To investigate the correlation between measurable muscle force and functional independence in activities of daily living (ADL).
Main Methods:
- Manual muscle testing, sphygmomanometry, and pinchometer assessments were employed to evaluate upper extremity strength.
- Functional abilities were documented using self-report forms.
- Repeated-measures analysis of covariance and Fisher exact test were utilized for statistical analysis.
Main Results:
- Children with SMA type II exhibited overall upper extremity strength between 35% and 40% of normal values.
- No significant changes in proximal or distal muscle strength were observed over the study period.
- A significant association (p = .02) was found between the ability to produce measurable pinch or gross grasp force and independence in mobility, hand function, and ADL.
Conclusions:
- Children with SMA type II present with notably weak but stable upper extremity muscle force.
- The capacity to generate even minimal force in grasp is linked to greater independence in functional tasks.
- These findings underscore the importance of strength assessment for predicting functional outcomes in pediatric SMA type II.
Abstract:
Upper extremity strength and function in a sample of ten children with spinal atrophy type II was determined using manual muscle testing, a sphygmomanometer, and a pinchometer. Functional abilities were recorded on self-report forms. Overall strength in this sample was determined to be 35% to 40% of normal. Repeated-measures analysis of covariance revealed no change with time in proximal or distal strength. Six children were capable of at least 1/2 pound of force in pinch or gross grasp vs four children with zero force in one of these measures. Ability to produce a measurable force in pinch or gross grasp was found to be associated with independence in mobility, hand function, and ADL by Fisher exact test (p = .02). These data document the weak, but stable, muscle force present in these children and relate the strength of function.