What is Spinal Cord Stimulation?
Spinal cord stimulation explained by Denver, Golden, Aurora, Boulder, Broomfield, Jefferson, and Littleton Colorado’s top pain doctors
Spinal cord stimulation is a minimally-invasive pain management application that involves placing a thin, flexible implant within the spinal column of a patient. The implant emits a low-amplitude electrical signal (which is the basis of neural signaling, or the method by which nervous tissue conducts information to and from the brain). The implant targets the spinal nerve in the immediate vicinity of its location, in the epidural space of the spine. This nerve may be either damaged or over-active, which results in protracted pain signaling. This is often the source of chronic pain. The implants are normally accompanied with a remote control that the patient can activate in response to painful sensations. Spinal cord stimulation has been demonstrated as effective in treating intractable chronic pain, and is particularly effective in the treatment of pain associated with nerve damage (i.e. neuropathic pain). Neuropathic pain may also be linked to dysfunction in nerves travelling either to or from the brain. Pain associated with spinal nerves may be associated with inflammation or mechanical damage. Spinal cord stimulation emits impulses associated with normal signals that may over-rule or drown out the signals associated with pain. These pain signals are received from tissues (including muscles, bone, and other nerves) that are sent to spinal nerves, whose task it is to convey these onward into the brain.
Chronic pain is a condition that is experienced by many people at some point in the course of their lives. Up to 30% of people in the U.S. are at risk of one type of chronic pain or another during their lifespan. The Institute of Medicine reports that approximately 116 million people in the U.S. are currently subject to a condition that causes chronic pain. This patient population is also not confined to the U.S. alone. A study across 15 European nations reported that 19% of the subjects interviewed reported at least one incident of pain that was experienced for six months or more. This study found that more than 50% of these respondents were unable to pursue employment due to chronic pain. Approximately one-fifth reported a loss of employment associated with their condition. This study also reported that approximately half of the respondents complaining of chronic pain were not receiving treatment for their particular condition, and that only 2% were receiving treatment from an appropriate pain specialist.
There are many conventional (e.g. pharmacotherapy) and more advanced, minimally-invasive (e.g. nerve blocks) treatment options available that are associated with effective and significant relief from chronic pain. However, some cases are resistant to these therapies and require further variations in pain management. An example of these is spinal cord stimulation. This is a safe, well-tested, and effective treatment for patients with chronic pain that has not responded to any other treatment or therapy.
What is Chronic Pain?
Chronic pain can range from mild to severe and can be debilitating. An untreated condition causing chronic pain is associated with a detrimental impact on a patient’s personal as well as their professional life. Individuals that suffer from chronic pain are more likely to lose days of employment, may show reduced work rates, and are associated with a higher average rate of consultation with physicians. Chronic pain may also be associated with a number of other serious health conditions, including depression and anxiety. Additionally, chronic pain can interfere with normal sleep patterns, making it difficult to fall asleep or stay asleep. Sleep difficulties may be due to the pain, or connected with the side effects of medications (such as analgesics) that are often prescribed to chronic pain patients. Individuals who have chronic pain are more likely to lead sedentary lives that can lead to obesity, which in turn can increase their pain levels. Chronic pain is associated with increased loss of normal function and movement in general, which in time can lead to significantly reduced quality of life and disability.
Symptoms of chronic pain vary widely from patient to patient. For example, while some patients may report a stabbing sensation, others will experience a general ache. Additionally, chronic pain levels can vary over time and are often affected by activity. Other symptoms may also be associated with chronic pain conditions. These may include muscle spasm, cramping, tingling, stiffness, radiating pain, numbness, or weakness as well as an increased reaction to pressure or touch.
Conditions Associated With Chronic Pain
Spinal cord stimulation can be an effective treatment option for individuals suffering from chronic pain. It has been reported that up to 75% of patients experience pain relief as a result of spinal cord stimulation.
Various conditions can be treated using spinal cord stimulation including, but not limited to:
- Spinal stenosis and inflammation
- Chronic pain resulting from failed spinal surgery
- Degenerative disc syndrome
- Peripheral or central nervous system disorders
Conditions such as spinal stenosis may respond well to treatment by spinal cord stimulation. This disorder involves a narrowing within the spinal canal that results in spinal cord compression, which is associated with pain. The narrowing seen in spinal stenosis can be caused by abnormalities in the spine or posture or by scar tissue that has accumulated in the immediate vicinity of the affected nerves. Patients that suffer from stenosis of the spine complain of pain, numbness, paresthesia, and reduced muscle control. Patients may find it difficult to walk, especially for prolonged periods of time. While there are a number of types of stenosis, cervical and lumbar types are the most common. One of the recommended treatments for spinal stenosis is an anesthetic injection. Anesthetic injections are injected via a needle through the skin’s surface into the affected location in an effort to relieve pain. The medial branch block is a type of injection that often results in a significant reduction of pain, almost immediately, in most chronic pain patients. However, in patients with severe pain, these injections may not produce the desired amount of pain relief. In these patients, spinal cord stimulation can be a favorable next treatment option.
Patients who have undergone unsuccessful spinal surgery may report chronic pain as a symptom. The pain that these patients experience after surgery is thought to be associated with the formation of scars around spinal nerve roots in the epidural space. However, there can be other issues that explain the pain experienced following spinal surgery including joint mobility issues, pressure constantly imposed on a spinal nerve, and intervertebral disc herniation. Symptoms of chronic pain following spinal surgery commonly include a diffuse, dull ache across the lower back region and the lower extremities. Additionally, stabbing, pricking, or sharp pains may be felt in the extremities of some patients. Spinal cord stimulation may be an effective treatment option for patients that have undergone failed spinal surgery, providing that other conservative treatment options have failed to provide pain relief.
Degenerative disc disease is a common condition that is often misunderstood. It is thought to be caused by the breakdown of intervertebral disc tissue between the vertebrae of the spine. Aging can result in degeneration of the intervertebral discs which can result in inflammation and irritation that can lead to pain. Often the joints in the neck and low back are affected. While the pain that is reported in those suffering from degenerative disc disease can be felt throughout the entire spine, it is sometimes localized to a specific area. The pain described by patients that suffer from degenerative disc disease differs but usually includes either a sharp, stabbing type of pain or a generalized, achy pain. In addition, numbness and tingling are commonly reported in degenerative disc disease patients and patients often report that their pain worsens with movement. There are a multitude of treatment options for patients that suffer from degenerative disc disease; however, when these treatments do not provide the desired pain relief effects, spinal cord stimulation may provide positive results.
Various conditions can affect the peripheral and central nervous systems, resulting in chronic pain symptoms. These conditions include complex regional pain syndrome (which occurs when the functioning of the peripheral or central nervous system is affected due to damage or disorder), peripheral neuropathy (which results when peripheral nerves are either damaged or have degenerated), and radiculitis (which occurs when the nerve root is either irritation or inflamed). At times, these conditions can occur with other symptoms including motor deficits, sensory changes, cramping, fasciculations (twitching), decreased muscle tone, and bone degeneration as well as skin, nail, and hair texture changes. When conservative treatment methods have failed, patients diagnosed with peripheral and central nervous system disorders may respond well to spinal cord stimulation.
Patients suffering from various other pain conditions may also benefit from treatment with spinal cord stimulation, when conservative treatment options have failed to provide positive results. These include the following.
Phantom limb pain was once thought to be psychological in nature; however it is now believed that it may originate within the brain and spinal cord following amputation. No treatment has been developed to specifically treat this condition. However, it has been suggested that because the condition may originate within the brain and spinal cord, patients suffering from phantom limb pain may experience positive results with spinal cord stimulation.
Diabetic neuropathy develops when the nerves, usually in the hands and feet, are damaged due to high glucose levels. Symptoms of diabetic neuropathy include numbness and pain in the extremities, reduced sensitivity to temperature changes, tingling and burning, sharp and stabbing pain, difficulty and pain with walking, muscular weakness, touch sensitivity, and foot problems (commonly ulcers and infections). In an effort to slow the disease process, patients are advised to maintain their glucose levels within a normal range. Currently, no cure for diabetic neuropathy exists; therefore, treatment revolves around pain management. There have been reported benefits in some patients following spinal cord stimulation treatment. Therefore, it may be an advisable treatment option for diabetic patients that suffer from neuropathy.
Central pain syndrome is associated with degeneration or damage of the brain or spinal cord. Symptoms of central pain syndrome may be different in each patient; however, a burning sensation is often reported. It is also associated with touch sensitivity, as well as movement, emotional, and temperature changes. In addition, they may report a sensation of pressure, pins and needles, aches, bouts of pain, and even excruciating pain that is unrelenting. Some patients have stated that they feel pain radiating from their head to their feet. Since this condition has been associated with spinal tissue, patients may experience some pain relief resulting from spinal cord stimulation treatment.
Post-herpetic neuralgia is thought to be a consequence of infection with the virus (herpes zoster) that is responsible for shingles and chickenpox. This condition can affect various area of the body; however, the symptoms usually occur in the tissues originally infected. Symptoms of post-herpetic neuralgia include chronic or acute pain as well as considerable touch sensitivity. Patients with severe pain may benefit from spinal cord stimulation.
Chronic hip and leg pain may be caused by a number of factors. These include arthritis (damage to the hip joint caused by an autoimmune condition), accidental injury, excessive athletic activity, and osteoporosis. The latter can increase the risk of a hip fracture, which is characterized by severe damage to one of the bones that make up the hip joint. These fractures are also associated with adolescents and younger children, a link that is primarily influenced by accidental injury during everyday activity, genetic factors, and (possibly) increased bodyweight. Fractures are associated with chronic pain, as are the surgical interventions to correct them. These are known as arthroplasties, and are associated with pain that can last for several years, both due to inflammation caused by the procedure and by the prosthetics implanted to replace or augment damaged bone tissue. Hip and leg pain may also be a result of failed back surgery syndrome, if spinal nerves associated with these regions are damaged. These forms of chronic pain may be treated by conventional means (e.g. drug therapy) but is resistant to these options in some cases. Spinal cord stimulation has shown some potential in the management of intransigent hip and leg pain.
While many of the conditions discussed involve damage or degeneration to the spinal cord or brain, some reports have shown that spinal cord stimulation may be an effective treatment option for pain that is associated with many cancer types. Further research needs to be conducted into how spinal cord stimulation may be implemented for cancer patients as this may prove to be an additional treatment option to offer to this patient population.
Spinal Cord Stimulation Development
The method of spinal cord stimulation for chronic pain management of was developed on the basis of the theory of gate control. In 1965, the gate control theory of pain was developed. This theory postulated that a certain portion of the spinal cord responded similar to a gate in the course of processing pain signals. The stimuli were carried to the spinal cord by nerves in all areas of the body by way of this gate, and it was thought that these signals could be disrupted with electrical impulses. The first successful spinal cord stimulation procedure was performed in 1971 for a patient with a history of unrelenting pain.
While spinal cord stimulation development was based on the application of this theory, the way it which it exerts its’ analgesic properties is not completely understood at this point. There has been a limited amount of research that has investigated this, but no concrete conclusions on this subject have yet been drawn. The strongest probable explanation (to date) is that there are many factors, working together, that are responsible for the pain-relieving effects of spinal cord stimulation. Since being introduced in the 1960s and early 1970s, the technique has made great strides. The advancements in spinal cord stimulation technology have resulted in improved effectiveness for reducing neuropathic pain. When spinal cord stimulation was first introduced, the electrodes were implanted in the subarachnoid space. This is the area between the pia mater and arachnoid meninges, which are tissues that protect the spinal cord. Subsequent advancements in placement techniques allowed the electrodes to be implanted in the epidural space, which is outside of the meninges. The advancement in electrode placement led to a significant reduction in some of the risks that are involved with spinal cord simulation, including inflammation of the meninges and cerebrospinal fluid leakage.
As previously stated, the procedure is believed to be a safe, effective treatment option for chronic pain, especially for cases associated with neuropathy. Studies that have examined the efficacy of spinal cord stimulation have found that over 70% of patients who underwent the procedure reported ongoing pain relief benefits in a one year follow up period. The use of spinal cord stimulation for chronic pain patients is increasing around the world. Estimates suggest that approximately 14,000 implantations take place each year around the world.
Spinal Cord Stimulation Device Types
The spinal cord stimulation procedure involves placing electrodes that are developed to be safely and effectively implanted into the relevant space of the spinal cord, as well as the placement of a control device. The main types of devices available for implantation include fully-implantable and transcutaneous. The transcutaneous device is the oldest device that is still being used and is the preferred device when high stimulation currents are desired. Transcutaneous devices are implanted subcutaneously, just under the surface of the skin, and are then linked to an electrode in the epidural space. On the other hand, fully-implantable stimulators are mostly battery-powered, and are operated using an external device. Replacement of these batteries every two to five years is necessary for these devices to functionally optimally.
Patients tend to have a preference for the fully-implantable type over the transcutaneous variety. They report that the fully implantable device is more discreet as it is not easily detected. Additionally, there are patient reports that indicate difficulty positioning a transmitting module correctly on the subcutaneous device, which is necessary for proper operation of the device.
Types Of Electrodes For Spinal Cord Stimulation
The electrode types generally incorporated in spinal cord stimulation procedures include the surgical plate electrode and the percutaneous electrode. Percutaneous types are approximately one millimeter across, and usually have four to eight platinum rings that are approximately three millimeters long. These platinum rings are placed at the end of the cylindrically shaped electrode. Surgical plate electrodes often have a similar number of platinum contacts that are mounted to the paddle-like shape electrode. The surgical plate is usually approximately 8mm wide; however, the size of the contacts has changed as the procedure has progressed. The electrode tips are linked to wires that are approximately 1.3 millimeters across and made of a medical grade material. This type of electrode design offers minimal tissue damage during their placement.
Trial Stimulator Devices
Physicians that recommend spinal cord stimulation often place a trial stimulator, in order to determine if the patients’ pain levels will be affected by the treatment. The device is implanted for several days to two or three weeks during the trial period in order to determine if the device will provide pain relief for the patient. During the trial period the device is also linked up to a pulse generator that is programmable. This assesses the occurrence of unwanted effects, such as sensory or motor abnormalities. Additionally, this pulse generator helps to determine if the patient achieves an appreciable level of pain relief. Furthermore, the trial period helps to make sure the patient does not exhibit adverse effects associated with the procedure. If the trial period produces positive results, the physician and patient may opt for a semi-permanent device to be implanted.
Spinal Cord Stimulation Procedure
If the trial period goes well and a spinal cord stimulator device is to be implanted, surgery will be required. However, the surgery involves relatively minimal invasion and may be performed in an out-patient setting. Spinal cord stimulation procedures using percutaneous electrodes are less difficult to perform than procedures that use surgical plate electrodes. A local anesthetic is administered prior to the implantation of percutaneous electrodes. The electrodes are extended into the epidural space near the nerve in question. Imaging techniques, such as fluoroscopy or X-ray imaging, is used to ensure accurate and safe placement of the implants. Spinal cord stimulation procedures using surgical plate-type electrodes may be more complicated. These are usually implanted with the patient under general anesthesia. A laminectomy, which is a procedure in which part of a vertebra is removed to give greater visibility or access prior to other surgeries, is often required to insert the electrodes into the appropriate space.
Either type of electrode is, as discussed above, placed alongside spinal nerves associated with a chronic pain condition. The electrode placement location is verified by pain relief reported by the patient using a trial screening. The pain specialist or physician performing the implantation also sets the strength of the impulse during the trial screening in order to establish the patient’s comfort level. In addition to placing electrodes, a pulse generator is also placed during the spinal cord stimulation implantation procedure. Recent developments have led to the introduction of rechargeable pulse generators, which require approximately two hours per week for charging. It should be noted that charging of the pulse generator does not interfere with treatment. A pulse generator is inserted below the surface of the skin in the region of the hip or buttock. This allows patients to easily reach their device in case they need to recharge it, or make adjustments to the programming with the remote control attached. This is usually linked to the device via leads. The hand held remote allows the patient to activate the pain-blocking signals on an as-needed basis.
The electrodes are placed beneath the skin; therefore once the spinal cord stimulator has been implanted patients can participate in regular recreational activities without any issues arising. Additionally, if the device appears to be defective or damaged, it can easily be removed.
Determining Appropriate Spinal Cord Stimulation Candidates
Spinal cord stimulation can provide relief from various conditions; however it is important that only ideal candidates be selected for this treatment. Before recommending spinal cord stimulation a full work up of the patient’s condition needs to be completed, including a detailed history and examination. The detailed history should include a thorough history of the patient’s symptoms, previous treatments including medication and other conservative treatment options tried, family history, past medical history, and any other relevant information. Additionally, questionnaires relating to the patient’s pain levels should be administered and completed as accurately as possible. A diagnosis is then made using this detailed history in addition to an assessment. All of this information is then used to determine if the patient is a suitable candidate for spinal cord stimulation. If they are, the information obtained will also help to determine the proper placement of electrodes during the device implantation procedure.
Spinal Cord Stimulation Benefits
This innovative procedure is an effective treatment option, providing relief for patients subject to chronic pain conditions with few risks or adverse events. Various factors can affect the efficacy of this procedure. A major factor is the physician’s competence, experience, and skill in performing these procedures. Prior to seeking care, patients should fully assess their physician (or pain specialist) options to ensure that they receive adequate care from a qualified practitioner. Patients should seek out a physician that specializes in pain treatments that has appropriate training in implanting and configuring the devices involved. Another factor in the efficacy of this technique is the patient’s episodic pain. The duration and frequency of pain, as well as the disease or disorder associated with chronic pain, need to be determined prior to treatment as this can have a significant impact on the efficacy of spinal cord stimulation.
The procedure is not intended to ameliorate the cause of a patient’s pain. The goal of device implantation is to provide significant chronic pain relief in the medium- or long-term. Pain relief is achieved in many cases where conservative treatment options have failed. Once pain relief is achieved, patients may experience a dramatic improvement in their life quality. The pain relief that patients experience allows them to resume activities that they once enjoyed, which helps to improve their overall health. Therefore, a major benefit of successful implantation is an increase in normal function and movement, as well as reduced mental health issues. Furthermore, patients are often capable of resuming professional or occupational life following a successful spinal cord stimulation procedure.
Contraindications For Spinal Cord Stimulation
This pain management technique is viewed as a relatively safe treatment and as a result there are only a few contraindications to treatment with this device. This procedure is not indicated for pregnant patients, or for patients for whom this is a possibility, because the risks of having this treatment in this patient population have not been assessed. Additionally, the safety and efficacy of the procedure is yet to be studied in patients under the age of 18. It should therefore not be used in the pediatric population. The long-term effects of the procedure have also not been fully studied. A number of patients have had beneficial effects over an extended time-frame, but this figure may not be significant. Since the procedure is relatively safe and minimally invasive, patients who are concerned about the long-term effects or who have adverse reactions from treatment can request that the device be taken out at any time.
Risks Of Spinal Cord Stimulation
There is a low incidence of risks that are associated with this technique. Complications or serious adverse events are also rare. Although the implantation process is minimally invasive, it is a medical intervention nonetheless, and carries risks associated with similar procedures. These include infection in the skin and other tissues through which electrodes and devices are implanted. Another risk is that scars may form around implants, although this is rare. Scar tissue development is associated with inflammation and irritation of nerve tissue, if it is in close enough proximity.
Other risks that are associated with the procedure include:
- Loss of blood at the implantation site
- Allergic reactions to the implants
- Cerebrospinal fluid leakage (associated with headache)
- Loss of sensory or motion control
- Complications associated with battery leakage or failure
- Rib or chest discomfort
- Electrode migration (movement) away from the appropriate location
- Breakdown of skin near the implantation site
If the device or implants fail to align properly with the spinal nerve or nerves in question, it may have a reduced or non-existent effect on pain signaling. In rare cases, the device may emit signals that magnify pain signals, rather than dampen them as intended. These failures are associated with chronic pain and possible paralysis.
It is important that individuals who have had a device implanted avoid undergoing diathermy procedures when the device is in place. These procedures include therapeutic ultrasound, microwave, or shortwave diathermy. Undergoing these types of procedures can result in serious damage to tissue, or possibly fatal, as the impulses from diathermy can resonate through the spinal cord stimulation device. Additionally, other techniques or equipment incorporating electromagnetic impulses, including defibrillation, radiofrequency ablation, magnetic resonance imaging (MRI), and electrocautery, should be avoided. Use of any of these on patients with active devices is associated with a high risk of death or injury.
Cost Effectiveness Of Spinal Cord Stimulation
The cost effectiveness of this technique has previously been investigated in an effort to determine if it was an appropriate treatment option compared to other treatment options for chronic pain. A previous study looked at the procedure in patients that were suffering from chronic pain resulting from unsuccessful spinal surgery. The results showed that spinal cord stimulation resulted in significant reductions in subsequent healthcare costs, compared to those of a control group. Additionally, it should be noted that 15% of the patients who underwent spinal cord stimulation resumed their employment, compared to none of the patients in the control group. The results show that this technique is a cost effective treatment solution for chronic pain patients compared to other treatment options.
Chronic pain takes the form of a common condition in today’s society, affecting 30% of people in the U.S. throughout their lifetime. Chronic pain can be unrelenting, leading to disability and a decreased quality of life. There are various treatment options available for chronic pain patients. While these first line treatments are effective for many individuals, there are many patients that do not have an appreciable response to traditional pain relief options. Spinal cord stimulation can be an effective treatment option for many chronic pain conditions when traditional conservative treatment methods have failed. Many studies indicate that spinal cord stimulation is an effective treatment option, especially for individuals suffering from neuropathic pain.
The process involved is minimally invasive and involves implanting electrodes and an impulse-emitting device in the appropriate areas of the spine, in order to release electrical impulses that “drown out” pain signals. It is believed that these impulses interfere with these signals as sent by certain spinal nerves. Therefore, this technique helps to control chronic pain associated with damaged or dysfunctional nerves. Often the device is connected to a hand-held remote so that the patient can maintain control over the impulses.
This technique is an alternative when first line treatment options have failed. Although it is invasive compared to some traditional pain relief options, such as oral medication or nerve blocks, it has demonstrably provided a more effective and longer lasting effect for chronic pain patients. While surgery is required, it is generally safe and carries minimal risks and can be performed (by a competent physician or pain specialist) as an out-patient procedure.
Previous research has shown that this is an effective treatment option, with approximately half of all individuals undergoing a trial procedure reporting significant pain relief. However, it should be noted that treatment with spinal cord stimulation may not provide pain relief for all patients suffering from chronic pain. As previously mentioned, treatment via device implantation is intended to provide relief from chronic pain; it is not intended to treat the underlying cause of the pain. It is therefore vital that patients undergo a full work up with their physician prior to undergoing spinal cord stimulation to ensure that this treatment is right for them and their condition.
Although the mechanisms behind the positive pain relief effect of this technique is not completely understood, there is evidence that has shown its success in cases of a variety of conditions associated with chronic pain. There is also some research that has shown that it may be an effective treatment option for Parkinson’s patients and for pain experienced by some cancer patients. The advancements that have been made in spinal cord stimulation since its introduction in the 1960s have been significant and it is believed that future advancements to the device and the implantation procedure will continue to emerge, making treatment with this technology even more attractive for the management of chronic pain.
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