Modification of spasticity by transcutaneous spinal cord stimulation in individuals with incomplete spinal cord injury

Authors:Hofstoetter US1, McKay WB2, Tansey KE2,3,4, Mayr W1, Kern H5,6, Minassian K1

Source: J Spinal Cord Med. 2014 Mar;37(2):202-11. doi: 10.1179/2045772313Y.0000000149. Epub 2013 Nov 26.

Keywords: functional electrical stimulation, long-term denervation, lower motor neuron lesion, computed tomography, human muscle biopsy, conus and cauda equina spinal cord injury

Abstract:

Context/objective: To examine the effects of transcutaneous spinal cord stimulation (tSCS) on lower-limb spasticity.
Design: Interventional pilot study to produce preliminary data.
Setting: Department of Physical Medicine and Rehabilitation, Wilhelminenspital, Vienna, Austria.
Participants: Three subjects with chronic motor-incomplete spinal cord injury (SCI) who could walk ≥10 m.
Interventions: Two interconnected stimulating skin electrodes (Ø 5 cm) were placed paraspinally at the T11/T12 vertebral levels, and two rectangular electrodes (8 × 13 cm) on the abdomen for the reference. Biphasic 2 ms-width pulses were delivered at 50 Hz for 30 minutes at intensities producing paraesthesias but no motor responses in the lower limbs.
Outcome measures: The Wartenberg pendulum test and neurological recordings of surface-electromyography (EMG) were used to assess effects on exaggerated reflex excitability. Non-functional co-activation during volitional movement was evaluated. The timed 10-m walk test provided measures of clinical function.
Results: The index of spasticity derived from the pendulum test changed from 0.8 ± 0.4 pre- to 0.9 ± 0.3 post-stimulation, with an improvement in the subject with the lowest pre-stimulation index. Exaggerated reflex responsiveness was decreased after tSCS across all subjects, with the most profound effect on passive lower-limb movement (pre- to post-tSCS EMG ratio: 0.2 ± 0.1), as was non-functional co-activation during voluntary movement. Gait speed values increased in two subjects by 39%.

Conclusion: These preliminary results suggest that tSCS, similar to epidurally delivered stimulation, may be used for spasticity control, without negatively impacting residual motor control in incomplete SCI. Further study in a larger population is warranted.

DOI: http://dx.doi.org/10.1179/2045772313Y.0000000149

Affiliations:

1 Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria
2 Hulse Spinal Cord Injury Lab, Crawford Research Institute, Shepherd Center, Atlanta, GA, USA
3 Departments of Neurology and Physiology, Emory University School of Medicine, Atlanta, GA, USA
4 Spinal Cord Injury Clinic, Atlanta Veterans Administration Medical Center, Atlanta, GA, USA
5 Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria
6 Department of Physical Medicine and Rehabilitation, Wilhelminenspital Wien, Vienna, Austria