Electrical Nerve Block for Control of Pain and Spasticity in Spinal Cord Injury
1Kilgore K, 2Bhadra N, 2Vrabec T, 2Bhadra N
1MetroHealth Medical Center, Cleveland, OH, USA; 2Case Western Reserve University, Cleveland, OH, United states
Objective: Pain and spasticity remain a significant problem in spinal cord injury (SCI). Although pharmacological treatment approaches, such as implantable drug pumps using baclofen or morphine can be successful, there are many undesirable side-effects of this approach [McIntyre et al., 2014; Mehta et al., 2016]. We are pursuing alternative treatment methods based on the emerging field of bioelectronics. In particular, we have developed multiple approaches of achieving an electrical nerve conduction block that could be used to modulate spasticity and block both acute and chronic pain [Kilgore and Bhadra, 2013].
Design/Methods: We are developing a novel means of treating pain and spasticity by blocking peripheral nerve transmission using electrodes placed on the skin surface that will deliver transcutaneous Direct Current nerve Block (tDCB). Our proposed method is based on a fundamentally different principle than existing electrical stimulation-based approaches to pain alleviation, such as transcutaneous electrical nerve stimulation (TENS) or spinal cord stimulation (SCS). Existing stimulation methods produce pain-relieving effects through indirect means. Our proposed tDCB method produces a direct block of nerve conduction at the site of delivery. It is analogous to a local anesthetic, except that it is produced electrically and has the unique features of nearly instantaneous block effectiveness and complete reversibility in real time.
Our approach is based on our work in electrical nerve conduction block, which can be accomplished through kilohertz frequency alternating current [Kilgore and Bhadra, 2013] and through charge-balanced direct current [Vrabec et al., 2017]. These approaches produce a transient depolarization of the nerve membrane, which blocks nerve conduction.
Results: Preliminary data has been obtained in an acute rodent model. Surface electrodes were placed in different geometric orientations over the common peroneal nerve. Direct current (tDCB) was delivered through these electrodes while the sciatic nerve was stimulated proximally and the ankle dorsiflexion measured distally. We have been able to achieve a 98% block of ankle dorsiflexion using tDCB in this configuration. Trancutaneous direct current application has the advantage of not causing any deleterious effects on the nerve since the electrode is not directly on the nerve. One concern with this approach is the potential for skin irritation, and we are currently evaluating the parameters over which tDCB can be applied safely.
Conclusion: People who have sustained a SCI and have pain and spasticity could benefit from a direct approach to nerve signal reduction with a non-invasive method. tDCB also allows partial block, which could be very beneficial for function. Long term cost of care could be reduced as the only consumable will be the disposable skin electrodes. We propose that the use of electrical nerve block could provide a useful alternative to pharmacological treatment of these disorders.
Support: This work is supported by NIH NINDS R01-NS-0895330 and the Case-Coulter Translational Research Partnership Program.
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