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

Abstract

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 mswidth 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 poststimulation, 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.

A paradigm of galvanic vestibular stimulation diminishes the soleus muscle H-reflex in healthy volunteers

“…15,16 It has been shown that the remaining altered spinal cord circuits below the injury can be activated and modified by transcutaneous spinal cord stimulation. 17 We suppose that in patients in whom the vestibulospinal pathways remained preserved, the altered spinal cord circuits below the injury could be conditioned by activation of the vestibulospinal pathways. To confirm this assumption, additional experimental work must be done.…”

“…15,16 It has been shown that the remaining altered spinal cord circuits below the injury can be activated and modified by transcutaneous spinal cord stimulation. 17 We …”

Effects of sustained electrical stimulation on spasticity assessed by the pendulum test

“…The active electrode consisted of two self-adhesive electrodes (ø 5 cm, V.Trodes, Mettler Electronics Corp., USA) connected together over the intervertebral space T11-T12. Analogously, the indifferent electrode consisted on two electrodes (7.5 × 13 cm, ValuTrode, Axelgaard Manufacturing Co., Ltd., USA) placed symmetrically over the umbilicus [5]. The stimulation protocol consisted in biphasic currentcontrolled stimulation continuously applied for 30 min.…”

“…Alternative treatments have been proposed applying electrical stimulation via epidural [4] and transcutaneous electrodes [5,6]. These studies suggest that an electrical field induced over the spinal cord is able to selectively depolarize the posterior root fibers in the lumbosacral region, leading to the activation of inhibition mechanisms as the Ia inhibitory interneurons and the increase of descending inhibitory activity.…”

“…These studies suggest that an electrical field induced over the spinal cord is able to selectively depolarize the posterior root fibers in the lumbosacral region, leading to the activation of inhibition mechanisms as the Ia inhibitory interneurons and the increase of descending inhibitory activity. This approach has the advantages of not affecting the residual motor control and being reversible [5].…”