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Finger muscle control in children with dystonia
Scott J Young1, Johan van Doornik, Terence D Sanger
1Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089-1111, USA.
Insights
Children with childhood dystonia exhibit abnormal muscle activation, including overflow to non-task muscles and poor single-muscle control during hand movements. These motor deficits are measurable via electromyography and correlate with dystonia severity.
Area of Science:
- Neurology
- Movement Disorders
- Pediatric Neurology
Background:
- Childhood dystonia is characterized by involuntary muscle contractions during voluntary movements.
- Limited research exists on the specific muscle activity patterns in pediatric dystonia, particularly affecting the hands.
Purpose of the Study:
- To investigate the electromyographic (EMG) activity of intrinsic hand muscles in children with dystonia.
- To quantify motor control deficits, including muscle overflow and single-muscle tracking ability, during a hand task.
Main Methods:
- Surface electromyography (sEMG) was used to measure activity in four intrinsic hand muscles.
- Participants performed an isometric tracking task involving a single hand muscle.
Main Results:
- Children with dystonia showed increased tracking errors and muscle overflow compared to controls.
- Both tracking error and overflow correlated with the Barry-Albright Dystonia Scale.
- Visual feedback reduced muscle overflow, suggesting a role for awareness.
Conclusions:
- Childhood hand dystonia involves deficits in individual muscle control and abnormal muscle overflow.
- These motor impairments are quantifiable using EMG during isometric tasks.
- Findings suggest potential therapeutic targets for managing dystonic symptoms in children.
Background:
Childhood dystonia is a disorder that involves inappropriate muscle activation during attempts at voluntary movement. Few studies have investigated the muscle activity associated with dystonia in children, and none have done so in the hands.
Methods:
In this study, we measured surface electromyographic activity in four intrinsic hand muscles while participants attempted to perform an isometric tracking task using one of the muscles.
Results:
Children with dystonia had greater tracking error with the task-related muscle and greater overflow to non-task muscles. Both tracking error and overflow correlated with the Barry-Albright Dystonia scale of the respective upper limb. Overflow also decreased when participants received visual feedback of non-task muscle activity.
Discussion:
We conclude that two of the motor deficits in childhood dystonia--motor overflow and difficulties in actively controlling muscles--can be seen in the surface electromyographic activity of individual muscles during an isometric task. As expected from results in adults, overflow is an important feature of childhood dystonia. However, overflow may be at least partially dependent on an individual's level of awareness of their muscle activity. Most importantly, poor single-muscle tracking shows that children with dystonia have deficits of individual muscle control in addition to overflow or co-contraction. These results provide the first quantitative measures of the muscle activity associated with hand dystonia in children, and they suggest possible directions for control of dystonic symptoms.
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