Revolutionising Pain Management: The Promise of Electrical Stimulation for Neuropathic Pain in Spinal Cord Injuries"
Introduction
Neuropathic pain is a common ailment among our clients, and it arises from a variety of sources. In this article, we focus on neuropathic pain as seen following spinal cord injuries. This type of pain is typically the result of a lesion or disease affecting the somatosensory nervous system. Somatosensory refers to the sensory activity originating from the receptors in the muscles, joints, skin, and connective tissues. This system conveys information from the body's periphery to the central nervous system, where it is interpreted.
This condition may manifest as dysesthesia—abnormal sensations—or as allodynia, where pain is triggered by stimuli that ordinarily wouldn't cause pain, such as the lightest touch to the skin. This pain type often results from changes in nerve function at the injury site and in surrounding areas, leading to the abnormal transmission of pain signals to the brain. Nerve damage or dysfunction causes incorrect signals to the brain that are perceived as pain, even without a "conventional" pain source. Despite its somewhat non-specific or vague cause, it can be very debilitating and remains both poorly understood and difficult to treat. When such pain is severe, it can result in reduced quality of life and can seem intractable to treatment.
A significant problem
The authors Davis L, and Martin J. (1947) described neuropathic pain in the context of a spinal cord injury.
The hot, burning pain would be replaced at times by severe crushing pressure, by vise-like, pinching sensations, by streams of fire running down the legs into the feet and out the toes, or by a pain produced by the pressure of a knife being buried in the tissue, twisted around rapidly and finally withdrawn all at the same time.
Anyone who experiences pain such as this might well think of this as their most fundamental problem. The prevalence of neuropathic pain after spinal cord injury has been studied, and the observed rates vary across different studies:
One study reported that 69.1% of patients with spinal cord injury experienced neuropathic pain [Kim HY, et al 2020.]
Another study indicated a prevalence rate of 53% for neuropathic pain post-spinal cord injury.
[Burke, D. et al. 2017 ].Additional research found that the prevalence of neuropathic pain in spinal cord injury patients ranged from 11% to 94%, highlighting the variability in reported rates [Celik, E. et al. 2012].
A systematic review and meta-analysis reported a pooled prevalence of chronic pain, including neuropathic pain, among spinal cord injury patients as 69% [Hunt. C. et al. 2021].
These variations in prevalence rates can be attributed to differences in study designs, definitions of neuropathic pain, and the populations studied. The fact remains that irrespective of the study, neuropathic pain represents a significant problem for many persons following a spinal cord injury.
Understanding Neuropathic Pain in Spinal Cord Injury
As noted above, neuropathic pain is frequently seen yet poorly understood. Symptoms can develop either at or below the level of injury. As their names suggest, the primary difference between at-level and below-level pain lies in their location relative to the site of the spinal cord injury. At-level pain occurs at or near the injury site, and below-level pain occurs further down the body.
At-level pain is defined as appearing within a region spanning one dermatome rostral and three dermatomes caudal to the neurological level of injury.
In layman's terms, At-level pain is a type of pain that occurs in the area around where the spinal cord injury has happened. Imagine the spinal cord as a map with different levels, each corresponding to a specific area of the skin called a dermatome. Each dermatome is like a zone on the skin that a specific part of the spinal cord is responsible for in terms of sensation. When someone has a spinal cord injury, the "neurological level of injury" is the specific spot on the spinal cord below which sensation and movement are affected. At-level pain happens close to this spot. Specifically, it can be felt in the dermatome just above (rostral to) the injury and can extend down to include the three dermatomes just below (caudal to) the injury level. So, if you think of the injury level as a specific line on the spinal cord map, At-level pain would be the pain that occurs in the zone right above this line and the three zones right below it. It's like having a pain that wraps around the body in a band-like fashion, starting from the injury level and extending a little bit above and below it.
As At-level pain is in regions where partial sensory function is likely to be retained, we are more likely to see allodynia and pain that seems spontaneous and ongoing. Descriptors for At-level pain include sensations such as "hot-burning," "tingling," "pricking," "pins and needles," "sharp," "shooting," "squeezing," "painful cold," and "electric shock-like."
Below-level pain, experienced below three dermatomes caudal to the neurological injury site, is a complex condition often faced by patients with incomplete spinal cord injuries. This type of pain not only has neuropathic origins, stemming from spinal cord damage, but it may also encompass an allodynic component, making it particularly challenging. Despite occurring in regions indirectly affected, below-level pain emerges due to the broader impact on the spinal cord's functionality, highlighting the intricate relationship between injury locale and pain perception. Similar to At-level pain, Below-level pain can present with sensory deficits, allodynia, or hyperalgesia.
Neuropathic pain following spinal cord injury (SCI) is a complex condition that involves a myriad of molecular and cellular changes. The mechanisms underlying this type of pain are multifaceted, involving both peripheral and central nervous system alterations, and details are beyond the scope of this article. We can say that neuropathic pain is often difficult to treat because of the many influential factors.
Challenges in Managing Neuropathic Pain
Diagnosing neuropathic pain in patients with spinal cord injuries poses significant challenges due to several factors, such as overlapping symptoms with other pain types and the subjective nature of individual pain experiences. Neuropathic pain's symptoms often resemble those of nociceptive pain, which results from damage to non-neural tissue, complicating the distinction between these pain types based solely on patient reports. The diagnostic process is further complicated by patients potentially experiencing a combination of pain types, including neuropathic, nociceptive, and visceral pain. Additionally, neuropathic pain can manifest both spontaneous pain and evoked pain, like allodynia and hyperalgesia, symptoms that are also common in other pain syndromes.
Pain is a highly subjective experience, with individuals describing their discomfort and its severity in varied terms. Many may struggle to articulate the nature of their pain.
The absence of validated diagnostic criteria specifically tailored for neuropathic pain in spinal cord injuries leads to diagnostic inconsistencies. To ensure accuracy, existing screening tools have limitations and must be complemented by a detailed pain history and somatosensory testing.
Pharmacological treatment
The conventional approach to treating neuropathic pain largely relies on pharmacological methods. While these strategies may alleviate certain types of chronic pain, they often fall short of providing sufficient relief for neuropathic pain, especially following a spinal cord injury. In cases where medications prove effective, their relief is typically only partial, leaving patients facing considerable discomfort.
The scarcity of high-quality evidence supporting many pharmacological treatments for neuropathic pain complicates the creation of clear, evidence-based guidelines. Existing evidence usually emerges from studies characterised by high dropout rates and numerous adverse events, potentially overestimating the treatments' efficacy. It's common for patients to resort to using multiple medications in an attempt to manage their pain, raising concerns about potential drug-drug interactions and unstable dosing.
Commonly prescribed medications for neuropathic pain, such as anticonvulsants, antidepressants, and opioids, are associated with a wide array of side effects, including drowsiness, confusion, gastrointestinal disturbances, and cognitive dysfunction. These adverse effects can be so pronounced that they often lead to a high rate of treatment discontinuation, undermining the long-term effectiveness of these therapeutic options.
Electrical stimulation as a treatment option
Electrical stimulation can be applied to peripheral nerves if pain is identified in a particular area. These approaches offer a non-invasive or minimally invasive and safe approach to pain management, with very few reported side effects. It is an effective alternative or supplement to invasive procedures and pharmaceutical treatments.
It is ideally tailored for personal use, enabling patients to shape their therapy to meet their specific needs and manage it independently at home. This autonomy in managing one’s treatment empowers patients and enhances care accessibility.
Its noninvasive nature, absence of harmful effects, and convenience of self-administration contribute to its widespread acceptance and satisfaction among users. This acceptance plays a pivotal role in the successful long-term management of chronic pain conditions.
However, electrical stimulation is not "one thing"; it is a quite broad range of techniques. As with pharmacological interventions, getting robust evidence and firm clinical guidelines is challenging. However, we think of electrical stimulation as a practical tool that needs to be fine-tuned to the individual needs of patients.
The Stimulette Edition 5 - 2 channel stimulator
The Schuhfried Edition 5 stimulator we work with supports several techniques for different types of pain, whether acute, chronic, nociceptive, or neuropathic. We find that some exploration is needed to find an effective approach in an individual case. Some people are sensitive to stimulation, and it is beneficial to have a product such as the Edition 5 that supports a range of options.
Some waveforms are particularly favoured in some countries yet virtually unknown elsewhere. There is a lack of formal research on how the various waveform options compare regarding effectiveness and how the parameters should be chosen. The good news is that such experimentation involves little risk if carefully approached. In all cases, the manufacturer's documentation should express a list of indications and contraindications, which should always be adhered to.
With the Edition 5 product, we typically start with one of the three TENS (Transcutaneous Electrical Nerve Stimulation) waveforms, described as TENS-LFT, TENS-HFT, and TENS-BuT.
Stim2Go stimulator
These waveforms are generally well tolerated, even by those sensitive to stimulation. The manufacturer contrasts the low-frequency character of TENS-LFT with the high frequency of the other waveforms as they are believed to get results by different means. The low-frequency character of TENS-LFT generates the secretion of the body’s pain-reducing hormones. The analgesic effect only increases slowly, and a treatment duration of 30 minutes is recommended. Due to the low frequency, the A-delta fibres are stimulated, and the opioid mechanism is activated. The TENS-HFT creates a faster pain dulling effectbut is most suited to acute pain.
TENS-BuT consists of pulses delivered in a “burst”. The suggestion is that burst mode TENS effectively stimulates both the pain gate and the opioid mechanisms simultaneously. Treatment duration is typically 10 to 30 minutes.
We are also soon to be working with Stim2Go from Pajunk. This novel stimulator supports a variety of TENS protocols and a form of Spinal Cord Stimulation.
Spinal Cord Stimulation (SCS) is a treatment designed to manage chronic pain when the underlying cause cannot be removed. It is particularly beneficial for patients with severe chronic pain that significantly limits their daily lives and who have not found relief from more conservative therapies, such as medications, TENS, physiotherapy, and injections. SCS delivers small electrical fields to the spinal cord, which mask pain areas by altering the messages sent to the brain, potentially reducing pain significantly. This treatment is effective in five to seven out of ten cases and is used for conditions such as neuropathic pain and complex regional pain syndrome. There are indeed different kinds of spinal cord stimulators, which can be categorised based on the type of electrical stimulation they provide:
Lower Frequency Spinal Cord Stimulation: This type uses frequencies that produce a tingling sensation in the painful area, known as paresthesia. It is the "traditional" form of SCS, and the patient feels the stimulation.
High-Frequency. Spinal Cord Stimulation: Unlike lower-frequency stimulation, high-frequency SCS usually does not produce a tingling sensation.
Additionally, advancements in SCS technology have led to the development of more specialised forms of stimulation:
Dorsal Root Ganglion Therapy: This targeted approach is especially effective in treating pain in specific areas such as the groin and foot. It applies therapy to the dorsal root ganglion, a cluster of nerves near the spinal cord at the base of each branching spinal nerve.
These different types of SCS offer various options for patients, allowing for a more tailored approach to managing chronic pain based on individual needs and responses to stimulation.
Burst Spinal Cord Stimulation: Delivers closely spaced, high-frequency current and effectively relieves pain without the associated tingling sensation. It benefits individuals who have built up a tolerance to the pain-relieving effects of traditional spinal cord stimulation.
The success rates of spinal cord stimulation (SCS) for chronic pain management vary depending on the type of stimulation and the criteria used to define "success." According to the sources provided:
Traditional low-frequency SCS therapy has a success rate where about 50% to 60% of patients achieve at least a 50% reduction in pain.
High-frequency SCS therapy (HF10 therapy) has shown more promising results, with studies indicating that more than 80% of patients experience significant pain relief.
Conclusion
This article emphasises the diverse and innovative approaches to managing chronic and neuropathic pain, mainly focusing on electrical stimulation techniques, including the Schuhfried Edition 5 stimulator and the upcoming Stim2Go from Pajunk.
The narrative details how these technologies, primarily through the employment of TENS waveforms and spinal cord stimulation (SCS), offer promising avenues for pain relief where traditional therapies may not succeed. We underscore the importance of customising pain management strategies to individual patient needs, highlighting the evolution of SCS into various forms, such as lower-frequency stimulation, high-frequency stimulation, dorsal root ganglion therapy, and the novel burst stimulation technology. This tailoring of pain relief methods to specific cases is particularly crucial in the treatment of neuropathic pain in spinal cord injury, where the underlying cause of pain cannot be removed.
Effective management of such conditions requires an understanding of the technical aspects of each approach and a compassionate consideration of how chronic pain affects patients' daily lives, advocating for a meticulous and patient-centred approach in clinical settings.
Given the promising outcomes of Spinal Cord Stimulation (SCS) and Transcutaneous Electrical Nerve Stimulation (TENS) in managing chronic and neuropathic pain where traditional therapies fail, it is critical for healthcare providers not only to consider but actively incorporate electrical stimulation techniques into their pain management strategies. The continued evolution of these technologies, evidenced by the advent of high-frequency, burst, and dorsal root ganglion therapy, underscores the potential for personalized and effective pain relief solutions.
It is equally important to advocate for ongoing research in electrical stimulation. This research should aim to refine existing technologies and explore new protocols that could offer relief to a broader patient population. Furthermore, patient education is paramount. Patients should be aware of electrical stimulation as a viable option, understanding the potential benefits and limitations. By fostering an environment where healthcare providers are well-informed advocates of electrical stimulation techniques and patients are educated on their options, the field can move closer to its goal of providing comprehensive, personalized care for those suffering from chronic pain.
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