Pain is among the most common symptoms for which patients consult physicians, and pain relief is foremost among a doctor’s traditional duties.
Chronic pain results from combined biological, psychological, and social factors, and most often requires a multifactorial approach to management. Patients with chronic pain frequently experience depression, sleep disturbances and fatigue, as well as decreased mental and physical function.
Chronic pain also produces long-term alterations in the nervous system. This alteration, termed “plasticity,” is manifested by changes in the sensitivity of pain receptors in the brain. This plasticity of the central neural system can lead to persistent pain even after medical or surgical correction of the disease or injury that was the original source of pain. It can even result in the spread of pain to other areas of the body.
Spinal cord stimulation has been used for more than 50 years by pain specialists to treat a variety of pain conditions. With advances in technology, effectiveness and favorable cost utility spinal cord stimulation − especially when compared with conventional medical management – this treatment has been shown to provide improved pain relief and overall functional capacity in patients suffering from chronic pain.
Spinal cord stimulation (SCS) is a minimally invasive technique used to treat various types of chronic pain. This therapy aims to reduce pain using a neuromodulation device (also known as a spinal cord stimulator). A spinal cord stimulator is an implanted device that delivers signals to specific nerves and pathways to counteract abnormal nerve activity in specific parts of the body. The exact mechanisms of SCS are complex and not fully understood, but the process can be compared to the way in which a pacemaker corrects an abnormal heartbeat. Similarly, a neuromodulation device can activate specific neural pathways that may help reduce symptoms associated with pain.
Spinal cord stimulation is usually considered for patients with chronic pain that has not been relieved by other conservative or surgical treatment method. In the United States these commonly include:
In Europe, additional conditions treated using neuromodulation include:
*FBSS refers to the circumstance in which a person has had back surgery (usually to treat lower back pain conditions such as lumbar spinal stenosis caused by a degenerative disc disease or a herniated disc) that has not resulted in adequate pain relief.
Limited medical literature suggests that SCS may be beneficial for patients with visceral abdominal and perineal pain as well as for painful diabetic neuropathy. It is important to remember, that patient with these and other chronic pain conditions should be evaluated individually to determine possible benefit from neuromodulation.
Neuromodulation treatment involves placing electrodes next to the precise area of the spinal cord that the physician believes is the source of pain. These electrodes transmit a low-voltage electric current that can stimulate the specific structures in the spine and result in release of various inhibitory neurotransmitters that, in turn, block neural impulses that cause pain.
Newer spinal cord stimulation devices and technologies have resulted in improved outcomes. The field of neuromodulation has developed rapidly since the first implantable spinal cord stimulator device was used to treat pain in 1967.
Implanting a spinal cord stimulator is generally an ambulatory (outpatient) procedure. A pain management physician can implant the neuromodulation device through a minimally invasive surgery. Physicians who have undergone additional, specific training in neuromodulation techniques have reduced complications and adverse events associated with this procedure. For this reason, it is vital that patients carefully choose a board-certified pain specialist with expertise in neuromodulation before proceeding with treatment.
Spinal cord stimulation is a compelling treatment for patients whose chronic pain has not been relieved by various conservative and surgical treatment approaches. While it may not be effective for all types of pain or for every patient, spinal cord stimulation is a safe, drug-free and cost-effective treatment. Patient selection is an important determinant for successful outcome following SCS. Therefore, prior to considering spinal cord stimulation therapy, patients must go through a thorough screening process. This process includes:
Once a patient is determined to be a good candidate for neuromodulation therapy, they are scheduled for a trial of the treatment. This temporary trial tests the effectiveness of pain control and the patient’s tolerability to the device before it is permanently implanted.
During the trial period, which typically lasts three to seven days, temporary percutaneous electrodes (leads) are placed via a needle and connected by an extension cable to an external generator. A trial is considered successful when it results in pain relief of at least 50% accompanied by an improvement in function.
After the trial period, the leads are removed by the physician at the office and the permanent implantation is performed at a later date (typically, two to four weeks later, to make sure there is no evidence of infection).
The spinal cord stimulator trial is usually performed under local anesthesia with monitored anesthesia care (intravenous sedation). Implant of the spinal cord stimulator can be performed under general anesthesia with intraoperative monitoring. The patient is seen in the clinic a few days to a week after the implant in order to monitor for wound integrity and signs of infection and to review the spinal cord stimulator settings and use of the programmer with the patient. The initial spinal cord stimulator settings often require slight adjustments in the first few weeks after implant, and are often stable thereafter.
Once implanted, the neuromodulations leads are designed to last indefinitely. The lithium-ion battery (also known as the internal pulse generator or IPG) that powers the spinal cord stimulator leads has a lifespan of five to seven years for non-rechargeable IPGs and nine years for rechargeable IPGs. In 2019, the FDA approved a low-dose burst stimulator with a non-rechargeable battery that lasts up to 10 years. IPGs are replaced via a minimally invasive surgical procedure when the battery demonstrates evidence of a low charge or at an interval specified by the device manufacturer.
Patient selection is an important determinant of successful SCS. In addition to evaluation of the type of chronic pain and appropriateness for SCS therapy, patients should be screened for comorbidities, contraindications to the technique, and potential technical difficulty. Despite this careful selection process, some patients will not achieve optimal pain relief with spinal cord stimulation. Most often, this is due to factors such as lifestyle (for example, preexisting tobacco or drug use), age or a lengthy delay between the first appearance of pain symptoms and device implantation.
Overall complications of spinal cord stimulation are uncommon when performed by an expert clinician, and are mostly related to hardware. Side effects may include any of the following:
About a week after the implantation, a patient will return the office so that the healthcare team can monitor the healing process and review the settings of the device. Initially, most spinal cord stimulators need slight adjustments in the first few weeks after implantation, but the settings are often stable thereafter.