Spinal Cord Stimulator – A Compelling Treatment Technique for Chronic Pain

Spinal cord stimulation has been used for more than 50 years treat a variety of chronic pain conditions. Advances in technology and cost effectiveness have made this treatment a viable option to provide improved relief and overall function in people suffering from chronic pain.

What is a spinal cord stimulator?

A spinal cord stimulator is an implanted neuromodulation device used to treat chronic pain in a minimally invasive way. The stimulator delivers signals to specific nerves and pathways to counteract abnormal nerve activity in selected parts of the body.

What kind of pain does a spinal cord stimulator treat?

Spinal cord stimulation is usually considered for patients who have chronic pain that has not been relieved by other conservative or surgical treatment methods.

In the United States, pain conditions treated commonly include:

  • chronic pain from failed back surgery syndrome (FBSS)*
  • complex regional pain syndrome (CRPS)

In Europe, additional conditions treated using neuromodulation include:

  • painful peripheral vascular disease
  • refractory angina

*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 spinal cord stimulation 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.

How does a spinal cord stimulator work?

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. The exact mechanisms of spinal cord stimulation 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.

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.

Is spinal cord stimulation an outpatient procedure?

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.

Who is a good candidate for a spinal cord stimulator?

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 spinal cord stimulation. Therefore, prior to considering spinal cord stimulation therapy, patients must go through a thorough screening process. This process includes:

  • In-depth history and physical examination in order to rule out presence of medical conditions that may increase the risk that the treatment will either fail or result in complications.
  • Routine laboratory evaluation (determined based on the patient’s medical history and the type of anesthesia that will be used during the procedure).
  • Relevant spine imaging studies (for example, X-ray films, CT and MRI scans) to assess the potential for technical difficulties that could arise during the procedure and to identify subset of patients for whom surgery may be a more appropriate treatment.
  • Psychological screening (often required by insurance companies for approval of payment).
  • For patients with pre-existing cardiac comorbidities, a consultation with a cardiologist as well as a compatibility test is often necessary.

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.

What can I expect from a spinal cord stimulator trial?

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).

Is getting spinal cord stimulator surgery painful?

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.

How long does a neurostimulator last?

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.

What is the success rate of a spinal cord stimulator?

A spinal cord stimulator trial is considered successful people experience pain relief of at least 50% and an improvement in nerve function. Success is dependent largely on the condition and overall health of individual patients. In addition to being evaluated for whether their particular chronic pain condition is suited to this therapy, patients should be screened for other factors. These include:

  • comorbidities – other conditions or diseases they may have)
  • contraindications – medications, conditions, lifestyle choices or other factors which may make this treatment unsuccessful or ill-advised
  • potential technical difficulty.

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.

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.

What are the side effects of a spinal cord stimulator?

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:

  • Incidental migration of electrodes with loss of appropriate neuromodulation coverage is the most common issue encountered in clinical practice. It can be detected if patient’s stimulation has changed and can be confirmed by means of an X-ray. The initial step to fix this problem involves reprogramming the electrodes by the clinician. If reprogramming does not work, surgical revision of the lead may be required. Various anchoring devices have been developed in order to minimize the risk migration.
  • In rare cases, lead fracture has also been reported and requires revision of the lead.
  • Infection is a possibility with any surgical procedure. Superficial infections can be treated with antibiotics. However, when deep infection is suspected, all of the surgical hardware may need to be removed. Reimplantation can then be performed at a site in the body that was not affected by infection.
  • Dural puncture resulting in cerebrospinal fluid (CSF) leak is another rare complication and can contribute to a postdural puncture headache (PDPH). Treatment may include an epidural blood patch.
  • Epidural hematoma is a rare surgical emergency that requires timely decompression by a neurosurgeon.
  • Direct spinal cord trauma is extremely rare during SCS placement but can be potentially devastating to the patient.

What can I expect after having a spinal cord stimulator implant?

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.

Authors

Image - Photo of Vladimir N. Kramskiy, MD
Vladimir N. Kramskiy, MD
Assistant Attending Neurologist, Hospital for Special Surgery
Clinical Assistant Professor of Anesthesiology, Weill Cornell Medical College

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