What Is Spinal Cord Stimulation?
Spinal cord stimulation explained by San Antonio, Austin, Houston, Dallas Texas top pain doctors
Chronic pain that has not responded to other treatment modalities, such as medications, steroid injections, or physical therapy, may respond to spinal cord stimulation. This is a reversible, safe, and functional means of managing different types of chronic pain. Chronic pain is a condition suffered by more people in the United States than cancer, heart disease, and diabetes combined, according to the National Institutes of Health. Chronic pain is the most common reason that people contact their healthcare provider and is the leading cause of short-term disability and long-term disability.
The prevalence of chronic pain conditions in the United States had been estimated as high as 30%. The number estimated by the Institute of Medicine, 116 million people, is only slightly lower than the 19% of individuals in 15 different European countries who report chronic pain experiences. In a study performed in 2006, individuals from the European countries reported suffering from chronic pain for longer than six months. The study surveyed individuals regarding their pain experience and found over half reporting chronic pain were unable to work.
Results from that same study showed that 20% of individuals had lost their job as a result of their pain condition. But, more surprising was that nearly half reported that chronic pain they suffered with for greater than six months was not being managed and only 2% were under the care of a physician who specialized in the management of pain.
Although there is some disagreement about the definition of chronic pain, it is often defined as pain that lasts longer than 12 weeks and continues after the normal healing process for injury has been completed. Chronic pain is often the result of an injury, diseased tissue, or illness. At times there may be no identifiable cause. Chronic pain can reduce an individual’s appetite, create an environment where consistent mood changes become normal, or limit their ability to complete activities of daily living.
Intractable pain, also known as Intractable Pain Disease, is a severe pain that is not currently curable by any traditional medical protocols and which can lead to an early death if not adequately treated. Intractable pain, particularly from neuropathic origins, can respond positively to spinal cord stimulation. Dysfunction in the central or peripheral nervous system can be a result of lesions in any one of these systems and result in chronic neuropathic pain. In fact the treatment with spinal cord stimulation for the management of chronic pain has been successful.
Spinal cord stimulation requires implanting a medical device near the spinal cord, which then delivers electrical impulses to the epidural space. The use of lower levels of impulses is the basis of the electrical signals sent through the body’s neurological system from the peripheral vascular system to the central nervous system. Most spinal cord stimulation devices use a hand-held controller through which patients control the pain-blocking signals as needed. Overriding the pain signal to the brain is the goal of treatment. Pain that starts from the spinal cord nerves is often associated with damage that is caused by inflammatory process to the peripheral nerves or by injury. Using a spinal cord stimulator to correct the impulses can effectively manage pain perception for the patient.
History Of Spinal Cord Stimulation
In 1965, Melzack and Wall proposed the gate control theory of pain in which they believed the dorsal horn of the spinal cord acted as the gate to sensation, which carries electrical impulses to the spinal cord by the peripheral nerves. This proposal began the research that resulted in neurostimulation treatments for chronic pain. Believing that this gate could be closed or interrupted with other electrical impulses to the peripheral system, researchers used spinal cord stimulation to effectively control the perception and sensation of pain. Following the initial research, it was suggested that implanting a stimulation device to deliver electrical impulses to the dorsal column of the spinal cord would disrupt the transport of the signal to the brain. The first epidural spinal cord stimulator was successfully used to treat intractable pain in 1971.
Although well-documented, the effectiveness of neurostimulation is not well understood. Developed on the basis of the gate control theory for pain, the mechanism for action continues to remain a theory without a full explanation. Currently, a small body of literature has explored the theory without any conclusive findings. It is believed that several factors working in combination might explain the benefits in the treatment of intractable pain with spinal cord stimulation.
Advancements in technology made since the development of the first stimulator in the 1970s has improved the effectiveness in treating and relieving neuropathic pain. Originally, spinal cord stimulators used electrodes that were positioned in the subarachnoid space of a spinal cord. This is the space between the pia mater membranes, also known as the meninges, and the protective arachnoid that surrounds the spinal cord. In the latter part of the 1970s, changes were made to the placement of electrodes making it possible to be located in the epidural space, outside the protective membranes, which reduced risks with spinal cord stimulation, such as leakage of the cerebral spinal fluid, inflammation of the meninges, or infection.
Today the procedure includes the use of two different types of electrodes for stimulation devices: percutaneous and surgical. Safe, reversible, and effective, this treatment for chronic pain will often positively affect the result of neuropathic disturbances. In previous studies, researchers have examined effectiveness and found patients using spinal cord stimulation for pain reported both 70% positive results and continued benefits after a one-year follow-up. Approximately 14,000 stimulation devices are implanted for the treatment of chronic pain worldwide every year.
Types Of Spinal Cord Stimulators
Use of electrodes to stimulate the spinal cord is the basis of treatment using a spinal cord stimulator. The procedure to implant the electrodes also includes the implantation of a stimulation device. Patients and physicians choose between a fully implantable device, and a transcutaneous device for the spinal cord stimulation. Each of these devices has its own advantages and disadvantages for the patient and medical team. Transcutaneous stimulators are implanted just under the skin, or subcutaneously. They are connected to an electrode located near the spinal cord in the epidural space for electrical impulse stimulation. To date, this is the oldest type of stimulator still being used in clinical practice. The transcutaneous device is preferred when patients require higher electrical currents for chronic pain management.
Fully implantable spinal cord stimulators generate electrical impulses using a battery and are programmed using an external device. Batteries are changed every two to five years, depending upon how frequently the patient discharges electrical impulses for pain control. Patients report a preference for the implantable device because the coils to the electrodes are not visible. Also, the transcutaneous stimulator needs repositioning of the transmitter coil to the implanted device in order for it to work appropriately. Some patients find positioning this device difficult, which significantly reduces the effectiveness when the impulse is not delivered to the electrodes.
Currently, there are two different types of electrodes used for either the percutaneous or surgically implanted stimulation device. The percutaneous device uses electrodes that are cylindrical and approximately 1.3 mm in diameter. Four to eight thin platinum rings, generally 3 mm long, are mounted near the end. Electrodes used for the surgical implanted device also have platinum contacts mounted on one side. However, they are paddle-like in shape and not cylindrical. Over time, researchers have experimented with the size of the contacts, but the size of the plate has remained constant at 8 mm in width. The tips for both percutaneous and surgical electrodes are connected to thin flexible wires designed to reduce the risk of tissue damage during placement.
Physicians who recommend spinal cord stimulation also use a trial stimulator device to assess pain control achieved using the electrical impulses and any side effects the patient may experience. The trial period can last up to a couple of weeks during which the patient evaluates their experience with pain relief and side effects. The trial device is also electronically connected to a programmable pulse generator which detects other symptoms the patient may experience such as paresthesia, unwanted sensations, or if they are able to gain significant relief. If the trial stimulator provides relieve, then a more permanent device is implanted.
Local anesthesia is used during the placement of the electrodes within the dorsal epidural space. Proper placement is ensured using X-ray or fluoroscopy, although placement of the surgical electrodes for the fully implantable device is slightly more difficult. The paddle-like electrodes for fully implantable spinal cord stimulators are implanted under general anesthesia using a minimally invasive procedure called a laminectomy. During a laminectomy, two small incisions are made along the right and left area of midline where the electrodes are to be placed. The lamina is removed and the electrodes placed in the epidural space. In this way, the electrodes remain outside the protective membrane of the meninges and will also correspond to the location of pain, verified by the patient through trial screening. The physician also sets the amplitude of the impulses that will be based on the patient’s perception of pain and pain relief.
During the procedure to implant the spinal cord device, a pulse generator is also placed. Advancements in technology have made available rechargeable implantable devices. Patients can now choose the type of device that is right for them and their lifestyle. Rechargeable devices require approximately two hours of patient time every two weeks. The pulse-generating device is inserted under the skin in the posterior gluteal region or in the lower abdominal region. This positioning gives the patient easy access to recharge the batteries or to make adjustments to the settings for pain management using a remote control. The stimulator typically connects to a hand-held device with wires so the patient is able to activate the electrical impulses designed to block their pain as needed.
Physical Conditions Related To Spinal Cord Stimulation
Patients who would like to be considered for the implantation of a spinal cord stimulator can expect to undergo a complete assessment by their physician. Prior to recommending a spinal cord stimulator, the physician must assess the previous course of pain and prior treatments recommended and attempted. This assessment is necessary to rule out the potential use of other more conservative treatment modalities prior to attempting the use of a spinal cord stimulator. The assessments will include a history of the previous symptoms, family history, past treatments that have been attempted, the results from those treatments, and other relevant information the physician may need to make an appropriate recommendation.
In some cases, physicians may use questionnaires to fully understand the pain condition, but clinical judgment is used for diagnosis. It is imperative that symptoms are reported accurately, as well as other symptoms or medical conditions that are seemingly unrelated to the chronic pain condition. All the information is used in order to determine the most appropriate treatment and the exact placement of electrodes during the procedure, should the physician determine a spinal cord stimulation device is appropriate
Chronic pain can be debilitating and have a detrimental impact when left untreated. Patients can experience reduced function at work and at home, an increased likelihood of missed work, a higher rate of physician visits, and lower productivity when they experience chronic pain. Other conditions linked to chronic pain include depression, anxiety, problems falling asleep and staying asleep, and emotional distress. In some cases these conditions can be a side effect of the pain medication used to treat chronic pain. Increasing difficulty to achieve a good night’s rest can also impact the perception of pain. Individuals who suffer from chronic pain have an increased potential to choose a more sedentary lifestyle without physical activity. These choices can increase the risk of weight gain, which in turn exacerbates their pain condition and increases their potential to experience other medical conditions associated with increased weight.
Symptoms of chronic pain vary depending upon the physical cause of the condition. Some patients describe sharp pain, while other patients find their pain perception to be more generalized. Patients should expect their perception of chronic pain to fluctuate and sometimes will depend upon the environment in which they find themselves. Fluctuations in pain can occur with recurring symptoms and exacerbations of the sensation of pain.
Specific clusters of symptoms will usually depend upon the underlying cause. However, some of the more common complaints include:
- Sensitivity to touch or pressure
- Radiating pain
- Muscle spasm
- Tingling, numbness, or weakness
Spinal stenosis is a condition in which the spinal canal is restricted, sometimes resulting in compression of the spinal cord. Stenosis can occur anywhere in the spinal canal, but most frequently is found in the cervical and lumbar areas. Chronic pain conditions that are a product of stenosis or an inflammatory response can achieve good results using spinal cord stimulation. Stenosis of the spinal canal can result in compression or narrowing of the spinal column. The narrowing can be the result of either spinal abnormalities, scar tissue around the spinal cord, or a result of chronic poor posture. Patients have reported symptoms including numbness, paresthesia, loss of motor control, and chronic pain with this condition. Patients may experience numbness or weakness in the lower extremities, or difficulty walking related to the pain.
Conservative treatments include anesthetic injections to the appropriate location or to the epidural space or cervical joint spaces. Medial branch blocks are an example of this type of injection. Patients often experience immediate and significant pain relief from these injections. However, in the case of severe spinal stenosis and chronic pain, these injections may fail to produce results. Patients who do not experience pain relief can be good candidates for spinal cord stimulation.
Failed Back Surgery
Chronic back pain as the result of back surgery is referred to as failed back surgery. Pain may be experienced as a result of scar tissue developing around the nerves in the epidural space. After back surgery for the relief of chronic pain, patients may also experience disc herniation, post-operative pressure on the spinal nerve, or altered joint mobility, all of which can result in chronic pain. Individuals who have a history of emotional distress, such as difficulty falling asleep or staying asleep, depression, or anxiety, will have an increased risk for developing chronic pain following back surgery. Symptoms can include diffuse, dull, or aching pain across the back or lower limbs. Some patients experience pricking pain in the limbs or a sharp, stabbing pain. When other treatment protocols have been unable to provide relief, patients who have experienced a failed back surgery can be good candidates for spinal cord stimulation treatments.
Degenerative Disc Syndrome
This commonly misunderstood condition results in chronic pain that is believed to be the result of wear and tear on the intervertebral discs. With age the spinal discs will stiffen and wear down, causing them to become inflamed and irritated. Pain is typically experienced in the back and neck region from this inflammatory process. In some cases the pain is localized to the intervertebral disc affected by degeneration, but in other cases the pain is experienced down the length of the spine. Patients may complain of symptoms that worsen with movement and include numbness, tingling sensations, sharp, stabbing pain in the area of the disc degeneration, or a widespread, generalized pain. Individuals who do not respond to more conservative treatment options that are available for degenerative disc syndrome may be considered good candidates for spinal cord stimulation.
There are several different types of neuropathies that may make patients a candidate for the use of a spinal cord stimulator to relieve pain. These conditions include damage or degeneration to the peripheral nervous system (peripheral neuropathy), pain in the upper and lower limbs as a result of injury, a condition that causes dysfunction in the peripheral or central nervous system (complex regional pain syndrome), or pain radiating along a sensory nerve inflamed at the nerve root (radiculitis). These syndromes can include symptoms such as changes to hair, nails and skin, loss of muscle tone, sensory difficulties, cramping, symptoms of motor insufficiency, and bone degeneration. If individuals have not responded to other treatment modalities, they may be appropriate candidates for spinal cord stimulation with good results to achieve pain control.
Other Neuropathic Conditions
Other conditions that can respond positively to spinal cord stimulation include the following.
Phantom Limb Pain: Following an amputation of a limb, patients may experience a neuropathic condition called phantom limb pain. At one time this was believed to be purely psychological but it is now recognized as a condition that originates in the spinal cord and brain. At this time, there are no specific treatments from which patients receive a positive result for phantom limb pain, but some suggest that spinal cord stimulation will achieve significant reduction in chronic pain because the sensation originates in the peripheral nerves and central nervous system.
Central Pain Syndrome: After damage or degeneration of the central nervous system, patients may experience a neuropathic condition resulting in chronic pain. Symptoms will depend upon the location of the injury that was suffered. The most common symptom is burning pain, but some patients also report sensitivity to touch, temperature changes, movement changes, or sensitivity to emotional changes. Some individuals report the sensation of pins and needles, pressure, aching pain, bursts of pain, or unremitting excruciating pain. In some instances the individual will experience pain from head to toe. The origination of the pain is in the central nervous system and spinal cord, which suggests that these individuals would also benefit from the use of a spinal cord stimulation device.
Diabetic Neuropathy: Individuals who suffer from diabetes may experience neuropathic pain when the nerve fibers are injured through exposure to blood sugar levels that are higher than normal. Nerves within the legs and feet are most at risk for this injury. Symptoms include pain and numbness in the legs, sharp and jabbing pain that can be worse at night, extreme sensitivity to touch, muscle weakness, tingling or burning sensations, pain with walking, decreased ability to feel changes in temperature, and significant problems with deformity, ulcers, infection, and bone or joint pain in the feet.
In order to control and potentially prevent this condition, diabetics should maintain blood sugar levels as close to normal as possible. Currently, there is no known cure for diabetic neuropathy and treatments are focused on pain management. Individuals who suffer from diabetic neuropathy have reported good pain control using a spinal cord stimulator as pain originates from the peripheral nervous system.
Post-Herpetic Neuralgia: This is another form of neuropathic pain, which is believed to be a complication of the herpes virus and causes symptoms that are related to the area of the body where the original outbreak began. Post-herpetic neuralgia can affect different areas of the body and is often a complication from the virus that causes shingles or chicken pox, causing chronic neuropathic pain. In some instances, the pain has been reported to spread to other parts of the body where the original outbreak had not occurred. Symptoms include acute or chronic pain and extreme sensitivity to touch. The use of a spinal cord stimulator has had positive results in the management of post-herpetic neuralgic pain in 70% of the individuals who use them, making this device a potential treatment modality. Spinal cord stimulators have also been shown to have potential in the treatment of pain associated with different types of cancers.
Benefits Of Spinal Cord Stimulation
Patients who suffer from chronic pain can receive numerous benefits using spinal cord stimulators with relatively few side effects. The usefulness is based on several different factors, such as the physician’s level of expertise and training. Patients are encouraged to consider practitioners who have expertise in pain management, as well as the appropriate training to properly implant spinal cord stimulator devices. Determining the effectiveness of the chosen intervention will rely on specific pain episodes and history of prior treatment modalities used.
For this reason, patient’s report of the symptoms, underlying cause, and past treatments of their chronic pain will have an effect on the degree of effectiveness in using a spinal cord stimulator device. The goal of therapy is to provide chronic pain relief. The spinal cord stimulator does not treat the underlying cause, but instead addresses the symptoms of chronic pain, allowing the individual to have a better quality of life. Favorable results for the relief of chronic pain that have not responded to other traditional forms of treatment can be expected in specific conditions. Patients often report immediate relief following the implantation of the device and will experience drastic improvements in their quality of life. Patients experience an increased control over their symptoms and are often able to return to activities of daily living, potentially even work, which they may have been unable to perform since the onset of symptoms.
A major benefit to patients is not only the reduced level of pain, but also the improvement in deficiency and reduction in disability. The outcome of these changes in emotional and psychological benefit from the reduction in pain can often result in the reduction of depression or anxiety. Patients, who have taken a leave of absence from work as a result of chronic pain, can potentially return following successful implantation procedure. This return to usual activities will also result in improvements in associated mental and emotional distress. Following a successful treatment, patients often report fewer issues with anxiety and depression. Scientists know that both anxiety and depression reduce the effectiveness of the immune system. Thus, reduction in chronic pain can affect overall health.
Implanting a spinal cord stimulator requires surgical intervention. The procedure is minimally invasive and can be done on an outpatient basis for the placement of a percutaneous device. A trial test to ensure benefits from the device helps individuals to evaluate the effectiveness of the stimulator and allows both patient and physician to move forward with treatment with greater confidence. Testing procedures also reduce the potential of negative side effects with a permanent implantation. These devices do not keep patients from participating in any recreational activities or exercising, including swimming. The leads for the device are located under the surface of the skin and protected from the environment. The stimulator devices are also easily removed when they are no longer effective or the pain condition has resolved.
Studies evaluating the cost effectiveness of spinal cord stimulators have determined the cost savings for individuals over the course of several years. The procedure is an alternative to other traditional methods for treating chronic pain. In one study, researchers evaluated a population of individuals who experience chronic back pain following a failed back surgery. Results showed the spinal cord stimulator offered almost $10,000 in savings in an average annual cost over five years. When compared to the control group, 15% of those who use the spinal cord stimulators return to work while no one in the control group was able to return to their jobs.
Spinal cord stimulation is regarded as safe with few contradictions for the procedure. It is not recommended for individuals who might be pregnant or become pregnant as thus far, the safety of the procedure has not been clinically tested on women who are pregnant. Some individuals have experienced long-term pain relief from their chronic neuropathic pain, while others have not. Spinal cord stimulator implantation of percutaneous devices can be done on an outpatient basis; most patients who do not receive results and long-term relief, or experience adverse effects, are able to have the device removed quickly.
The implantation of spinal cord stimulators is a beneficial treatment for individuals who suffer from chronic pain conditions. This procedure is regarded as generally safe and there are few reported risks associated with the implantation of the device. Serious complications are rare. Spinal cord stimulation may not provide pain relief in all cases, but the literature has demonstrated that approximately half of all patients who use a trial stimulation device report significant pain relief.
Intended only for the relief of distressing symptoms of neuropathic chronic pain, a spinal stimulator is not able to address the underlying cause of the condition created by injury, illness, or diseased tissue. Patients who would like consideration for implantation should undergo a full assessment with a physician expert in pain management.
The procedure is minimally invasive, although a fully implantable device requires surgical intervention and includes risks similar to other surgical procedures. All surgical procedures carry a risk of infection at the site of incision and a risk from the anesthesia. Although rare, the implantation of a device also carries the risk of scar tissue at the location of the insertion of the wire, a risk of infection, and risk of cerebrospinal fluid leak. Scar tissue can cause pain and inflammation when located in close proximity to the nerves.
Other risks associated with the implantation of a spinal cord stimulator include:
- Allergic reaction to the implanted device
- Bleeding at the incision site
- Cerebrospinal fluid leak
- Unpleasant stimulation of the chest or ribs
- Migration of the electrode
- Complications from battery failure or leakage
- Skin breakdown over the electrode site
- Pain at the site of incision
Spinal cord stimulator devices can fail if enough area controlled by the defective nerves is not covered by the electrodes from the device. In some cases failure will be the result of electrical signals that produce other than pain blocking impulses, causing a lack of sensation or nerve damage.
Individuals using a stimulator should not use diathermy procedures, such as therapeutic ultrasound diathermy, shortwave diathermy, or microwave diathermy. While implanted, these procedures can cause significant tissue damage and can even result in death. The energy from the diathermy procedure may be transferred through the stimulator and delivered directly to the spinal cord of the patient. Other electromagnetic interferences should also be avoided because of the risk of serious injury or death. These devices can include magnetic resonance imagery, radiofrequency ablation, electrocautery, or defibrillation. The use of an implanted device in patients under the age of 18 has not yet been evaluated for safety and effectiveness.
Chronic pain conditions create serious public health concerns and are often characterized as persistent and unremitting pain continuing after the usual time for healing. It is also associated with other physical and psychological issues, as well as an individual’s ability to function on a daily basis. Individuals often report missed work, an increase in sedentary lifestyle, an increase in depression and anxiety, and lost productivity associated with chronic pain.
An accurate diagnosis by a physician is the first step in achieving chronic pain relief. There is evidence in the literature that stimulation to the spinal cord will provide relief to those who suffer from unremitting chronic pain and is particularly effective in the case of neuropathic pain. Spinal cord stimulation involves the implantation of a medical device near the spine to deliver pain-blocking, low-level electrical impulses. These impulses are used to block pain signals from the peripheral nerves under the gate control theory of pain. In this way stimulators control pain signals from peripheral nerves that are damaged or inflamed. Patients are given remote control devices in order to program the implanted device and activate the stimulation whenever it is necessary.
Spinal cord stimulation is more invasive than other conservative and traditional medical procedures but it has also been shown to be more effective in reducing a patient’s chronic pain than medical procedures such as nerve-blocking injections. Spinal cord stimulator insertion is considered safe and can be done on an outpatient basis. Good candidates for the device will expect to undergo a trial period, during which they will have a temporary device for the stimulation inserted and another which will monitor their response to the intervention. If no unwanted side effects are reported, and the patient experiences good pain relief, physicians will implant a permanent device.
There is new literature that suggests spinal cord stimulation is effective for a wide range of pain conditions that previously failed to respond to other conservative medical protocols. Research is also underway in the treatment of individuals who suffer from Parkinson’s disease using spinal cord stimulation. These devices may change the future of treating chronic pain as further studies continue to provide evidence of positive results using spinal cord stimulators for the relief of chronic pain.
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