Does continuous passive motion of the ankle applied with a pneumatic robot alter spinal cord excitability?

• Main Author: Noble, Steven A.
• Other Authors: Zehr, E. Paul
• Format: Others
• Language: English; en
• Published: 2017
• Subjects: spasticity; spinal cord injury; stretching; stroke; continuous passive motion; cerebral palsy
• Online Access: https://dspace.library.uvic.ca//handle/1828/8640

Background: Spasticity of the ankle can occur in multiple sclerosis and stroke, and can significantly reduce quality of life by impeding walking and other activities of daily living. Robot driven continuous passive motion (CPM) of the ankle may be a beneficial rehabilitation strategy for lower limb spasticity management, but, objective measures of decreased spasticity and improved locomotion remains uncertain. Additionally, the acute and chronic effects of CPM on spinal cord excitability are unknown. Objectives: To evaluate: 1) the acute changes in spinal cord excitability induced by 30 min of CPM at the ankle joint, in neurologically intact individuals and in those with lower limb spasticity; and, 2) chronic training-induced effects of 6 weeks of bilateral CPM training on reflex excitability and locomotion in those with lower limb spasticity. Methods: Spinal cord excitability was assessed using Hoffmann (H-) reflex recruitment curves, collected immediately before and following 30 min of CPM of the right (neurologically intact) or more affected (clinical) ankle. A multiple baseline repeated measures study design was used to assess changes following 18 bilateral CPM training sessions. Spasticity and locomotion were assessed using the Modified Ashworth Scale, the 10 m Walk test, and the Timed Up and Go test. Results: Twenty-one neurologically intact (6 female, 15 male, mean age 24.5 ± 1.7y) and 9 participants with spasticity (3 female, 6 male, mean age 58.9 ± 9.7y) due to various neurological conditions including stroke (n=4), MS (n=3), spinal cord injury (n=1), and cerebral palsy (n=1). In the neurologically intact group, CPM produced a bi-directional modulation of H-reflex creating ‘facilitation’ (n=12) (31.4 ± 20.9% increase in H-reflex amplitude) and ‘suppression’ (n=9) (32.9 ± 21.0% decrease in H-reflex amplitude) groups. In the clinical participants, acute CPM before training significantly increased H-reflex recruitment curve variables H@Thres and H@50; but there was no significant effect of acute CPM post-training. Baseline reflex excitability following training was reduced on the MA side for H@Thres, H@50 and H@100 by 96.5 ± 7.7%, 90.9 ± 9.2%, and 62.9 ± 21.1%, respectively. On the less affected side there was a significant decrease in H@Thres and H@50 by 83.4 ± 29.0% and 76.0 ± 28.3%. Time to complete the 10 m Walk Test was not different (5.2 ± 7.9% change, p = 0.06), and time to complete the Timed Up and Go was decreased (9.5 ± 12.3% change, p = 0.05). Spasticity of the ankle plantar flexor muscles, assessed by the Modified Ashworth Scale, was reduced in 4 participants with spasticity. Conclusion: Acute and chronic CPM of the ankle can significantly alter spinal cord excitability. CPM training may be a useful strategy to decrease spasticity of the ankle plantar flexors. === Graduate === 2018-09-15