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Changes in movement characteristics of the spastic upper extremity after botulinum toxin injection
Edward A Hurvitz1, Gerry E Conti, Susan H Brown
1Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor, MI, USA. ehurvitz@umich.edu
Objective:
To examine the longitudinal effects of botulinum toxin injection on movement characteristics of the spastic upper extremity in children by using motor control testing (MCT) techniques and standard clinical measures.
Design:
Open-label clinical trial.
Setting:
Motor control laboratory at an academic medical center.
Participants:
A convenience sample of 9 subjects (5 boys, 4 girls; age range, 7-16 y) with cerebral injury (stroke or cerebral palsy) and asymmetric upper-extremity function because of spasticity. Eight subjects had right-sided involvement.
Interventions:
Botulinum toxin injection to the involved upper extremity, involving elbow, wrist, and finger flexors, depending on clinical presentation.
Main Outcome Measures:
Clinical measures included range of motion (ROM), the Ashworth Scale, FIM trade mark instrument, Pediatric Evaluation of Disability Inventory, portions of the Bruininks-Oseretsky Test of Motor Proficiency, and the Purdue pegboard. MCT consisted of visually guided reaching, bilateral finger-to-nose movements, hand tapping, and isometric pinch force tasks. Kinematic assessments were made before and at 2, 4, 6, 12, 18, and 24 weeks after botulinum toxin injection.
Results:
All subjects had increased ROM and decreased Ashworth values throughout the testing period. In motor control tasks, improvement typically occurred earlier in the least complex movements, such as hand tapping, with 6 of 9 subjects showing a maximum, although transient, unilateral tapping speed by 6 weeks. A similar time course was observed for pinch force tasks. Improvement in more complex, forward-reaching tasks occurred much later (week 12 or later) or did not occur at all. As with the hand tasks, improved reach performance declined toward the end of the testing period. All subject showed minimal or no improvement in bilateral finger-to-nose movements. Neither maximum changes in ROM or Ashworth values correlated with improvements in functional elbow extension during sit and reach tasks, with 3 subjects with normal active ROM showing late onset or no change in reach.
Conclusions:
Although botulinum toxin reduced tone and increased ROM of the spastic upper extremity, the time course and degree of motor improvement appears to depend on the complexity of the task. Future research should focus on the value of adjunct therapy, such as task-specific training, in addition to botulinum toxin treatments to facilitate functional improvement of the spastic upper extremity.