Spinal Cord Stimulation - What it is and why it matters
How much does a spinal cord stimulator cost in the uk? Well, a bit early to answer that question but perhaps in 2023 we will start to see some practical clinical solutons for this exciting technology.
We should shortly see the emergence of new spinal cord stimulation products that can assist rehabilitation, as the first examples are approaching commercialisation. Although not a cure for spinal cord injury, these devices have been shown to assist in the recovery of function in situations where this seemed lost for ever.
Spinal cord stimulation (SCS) has a rich history that dates back to the 1960s, when it was first introduced as a potential treatment for chronic pain management. Pioneered by Dr. Norman Shealy (1967) this innovative method was initially developed to alleviate intractable pain by delivering mild electrical pulse trains to the spinal cord via implantation of electrodes.
Over the years, the field of SCS has witnessed significant advancements in both technology and research, broadening its potential applications to include functional recovery following spinal cord injury (SCI).
This article looks briefly at the state of the art.
The introduction of transcutaneous spinal cord stimulation (tSCS) in the early 2000s marked a major turning point, as this non-invasive method reduced or potentially eliminated the need for surgical implantation. With the ongoing development of technologies and a deeper understanding of the spinal cord's complex neurophysiology, SCS and tSCS continue to evolve, offering promising avenues for improving the quality of life and independence for individuals affected by spinal cord injury.
Who can benefit from SCS
According to the Spinal Injuries Association (SIA), the annual incidence of spinal cord injury (SCI) in the UK is approximately 40 cases per million people. With a population of around 67 million, this translates to roughly 2,680 new cases of SCI each year. The numbers living with an SCI is estimated to be some 40,000 to 50,000 individuals.
While it's difficult to provide an exact number of people who might benefit from SCS, it is reasonable to assume that a significant proportion of the affected population could potentially experience improvements in their quality of life and functional recovery. Further research and development in SCS, as well as patient-specific evaluations, will be crucial in determining the precise impact of this therapy on the spinal cord injury population in the UK.
As with any medical intervention there will be indications and contraindications to use of these devices - in other words some people will be most suitable and likely to benefit and others with not be able to take advantage of this for safety considerations
The body electric
Spinal cord injury affects the spinal cord’s ability to carry “messages” between the brain and the body that control sensory, motor and other functions. Our understanding of the complex structures of the brain and spinal cord is of course incomplete and is founded on a series of discoveries that started in the 19th and 20th centuries. I won’t recount all of this history except to say that we have known for many years that a form of electrical energy was present within the brain and nerve structures of the body. In the early 20th century scientists debated whether the brain/nerve processes were electrical or chemical - the so-called “Soup or Sparks” debate. In fact, there are both factors at work and both can provide leverage for therapeutic interventions
What matters for this discussion is that, with almost all injuries, the cord is damaged but not completely severed. Whilst injuries are generally classfied as “Complete” or “Incomplete” injuries, even complete injuries may have some intact pathways. However, clumsily we are applying it, SCS seems to “work”.
What is an SCS?
An SCS is a medical device that deliberately sends electricity to the spinal cord. Many of our clients use Functional Electrical Stimulation (FES) in FES Cycling or other applications that target either a peripheral nerve or a muscle. SCS is rather different in intent.
These FES bikes and other FES techniques are so-called neuromodulation devices that in various applications are designed to interface with the brain or with peripheral nerves and muscles. SCS consists of electrodes to deliver the electrical current, a battery pack to provide the current and of course the stimulator electronics to modulate the electricity
Some designs may be used externally on the skin (transcutaneously) or as implants within the body. With implanted devices, the electrodes are placed between the spinal cord and the vertebrae, while the battery pack is placed under the skin.
In the USA the regulatory agency, FDA, first approved an SCS device for use in 1989 to relieve chronic pain from nerve damage. Pain therapy presently accounts for about 70% of all neuromodulation treatments and there is a high level of evidence supporting their use for neuropathic pain.
Research
Research had demonstrated that animals with completely severed spinal cords could walk proficiently on a treadmill with partial body weight support. This relied on the presence of so-called central pattern generators.
The theory behind this research was that the movement of the legs by the treadmill activates sensory afferents in the limbs that in turn, switch on these spinal central pattern generators. The result of this training was rhythmic stepping, timed to the movement of the treadmill.
Research then explored several noninvasive forms of stimulus energy, such as electrical, magnetic, and vibration and found that they may augment the effects of treadmill training.
One approach was tSCS.
This approach has been shown since 1982 to enhance the excitability of spinal neural circuits which has the potential to improve voluntary performance in persons with incomplete injuries.
In recent years, studies have highlighted the potential benefits of tSCS in improving motor function and reducing spasticity in individuals with spinal cord injuries. One noteworthy study, conducted by Angeli et al, demonstrated that tSCS could facilitate voluntary movement and weight-bearing standing in patients with motor-complete spinal cord injuries. This breakthrough research indicated that tSCS, when combined with targeted physical rehabilitation, could improve motor function and foster neural plasticity in individuals with severe spinal cord injuries.
More recent studies have continued to explore the potential applications of tSCS, with promising results in areas such as locomotor recovery, balance control, and bladder function. Despite these encouraging findings, it is crucial to note that more extensive research is needed to fully understand the optimal parameters, long-term effects, and widespread applicability of tSCS in the spinal cord injury population.
Research suggests that this change in excitability enables the brain to utilise functionally silent descending pathways to produce and enhance voluntary movements. In other words it facilitates neuroplasticity. It is now thought that the priming of the nervous system offered via tSCS could augment existing physical rehabilitation interventions.
tSCS, both in single sessions and repeated applications, is associated with improved standing postural control, gait kinematics, and upper extremity function. tSCS has also been demonstrated to have an impact on autonomic nervous system and non-voluntary functions (such as blood pressure regulation and bladder function). A recent review by Martin (2021) looks at the topic in detail for lower limb and upper limb applications.
According to a recent article, in Medium, a number of products are in final clinical trials. For example, Onward is developing two SCS technology platforms, ARCEX and ARCIM.
ARCEX is an external platform consisting of a stimulator and wireless programmer, and it received FDA BDD (BDD Stands for Breakthrough device designation) to improve hand and arm function. Onward plans to submit for marketing approval in the U.S. and Europe with the goal of launching ARCEX in the second half of 2023.
ARCIM is an implantable platform, consisting of a pulse generator and lead placed near the spinal cord. ARCIM is controlled by wearable components and a smartwatch. It has enabled paralyzed people to stand and walk again as well as to normalize blood pressure and provide trunk stability. Stable blood pressure is necessary to keep people from fainting, and trunk stability is necessary to support balance and a variety of activities. Onward expects to begin pivotal trials to support FDA filing for ARCIM within two years. Other potential symptoms that ARCIM may support include reduced spasticity, improved sexual function, and bladder and bowel control.
Conclusion
It can be frustrating for persons who need this technology to understand that we always seem to hear that “more research is needed”. Safety of course is always important - no one wants to risk making matters worse. Generally speaking tSCS is likely to emerge as a generally safe technology with relatively few absolute contraindications. We do need to understand how the specific patterns of electrical stimulation can impact upon effectiveness and which individuals are most likely to benefit from this therapy.
We think the best results will be found when this technique is applied as an adjunct to training methods such as FES Cycling or locomotor training.
References
Shealy, C. Norman, Mortimer, J. Thomas, and Ronald B. Reswick. "Electrical inhibition of pain by stimulation of the dorsal columns: preliminary clinical report." Anesthesia & Analgesia 46.4 (1967): 489-491.
Angeli, Claudia A., Victor R. Edgerton, Yury P. Gerasimenko, and Susan J. Harkema. "Altering spinal cord excitability enables voluntary movements after chronic complete paralysis in humans." Brain 137.5 (2014): 1394-1409.
Martin, R (2021) “Utility and Feasibility of Transcutaneous Spinal Cord Stimulation for Patients With Incomplete SCI in Therapeutic Settings: A Review of Topic “, Frontiers in Rehabilitation Sciences, Volume 2, DOI=10.3389/fresc.2021.724003 , ISSN=2673-6861