Electrical nerve stimulation could reduce spasticity in spinal cord injury

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Win Min Oo (Department of Physical Medicine and Rehabilitation, Mandalay University of Medicine, Myanmar) and others report in the Archives of Physical Medicine and Rehabilitation that transcutaneous electrical nerve stimulation (TENS) plus standardised physical therapy reduces clinical spasticity in patients with subacute spinal cord injury (sustained less than six months ago) compared with standardised physical therapy alone.

 

Oo et al write that 65–78% of spinal cord injury patients develop spasticity and 40–60% of these patients report it as a clinical impairment. The authors add: “Spasticity not only leads to incapaciting complications such as muscle contracture, pain, difficulty in functional activities but also increases the economic and caregiver burden. Suboptimal treatment of severe spasticity contributes to significant obstacles in the rehabilitation process. Therefore, the spasticity should be treated effectively and judiciously.”


Oo et al comment that, in a previous study: “Vibration of the Achilles tendon during a complete block of the common peroneal nerve, which innervated the antagonistic dorsiflexor muscles, resulted in the decreased inhibition of soleus monosynaptic reflex. Therefore, it was suggested the stimulation of Ia afferent fibres in the common peroneal nerve with TENS could increase the inhibition of this reflex and decrease the plantar flexor spasticity.”


Therefore, the authors compared the immediate and short-term effectiveness of TENS and standardised physical therapy with standardised physical therapy alone for the reduction of spasticity in patients with subacute spinal cord injury (sustained less than six months ago). In the prospective study, patients with subacute spinal cord injury and clinically verified spasticity were randomised to receive TENS and standardised physical therapy (8 patients) or standardised physical therapy alone (control group; 8 patients). Oo et al state that the TENS procedure involved two electrodes from each channel being applied to each common peroneal nerve (L4–S2) in “such a way that the first anode electrode was placed posterior to the head of the fibula and the second cathode electrode was applied over the deep peroneal nerve 2cm lateral to the tibial bone and 2cm below the head of the fibula.”

After the first session, the composite spasticity score was significantly reduced in the TENS group compared with the baseline levels in that group (mean difference 1.75; p=0.002) but no such significant difference was found in the control group (p=0.095 for the comparison). Furthermore, there was a significant difference in the composite spasticity score, in favour of the TENS group, between groups (p=0.006 for the comparison). Oo et al report: “After the final session, the composite spasticity score significantly improved in the experimental group [p<0.001 for the comparison] but was not significantly improved in the control group [p=0.051 for the comparison]. The between-group difference of composite spasticity score was also significant [2.13; p=0.001].”  


According to the authors, the mechanism of spasticity reduction is hypothesised to be mediated by modulating excessive α-motor neuron activity through dynorphin release and by inducing synaptic reorganisation through increased afferent sensory inputs.


They conclude: “Combination of TENS with standardised physical therapy was beneficial in synergistic reduction of clinical spasticity of both immediate and short-term basis in subacute phase of spinal cord injury rehabilitation. However, further replication of this study with larger sample size is required for final evidence.”

Oo told Spinal News International: “More data are still needed, especially for the generalisation to other spasticity models by conducting the replication study”

 

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