What Is a Spinal Cord Stimulator?

A spinal cord stimulator (SCS) is a surgically implanted medical device that delivers low-level electrical pulses to the spinal cord to interrupt pain signals before they reach the brain. SCS devices are classified by the FDA as Class III medical devices — the highest-risk category — and are typically recommended only after other treatments have failed to provide adequate relief.

SCS Device Components

A spinal cord stimulator system consists of three primary components that work together to deliver electrical stimulation to targeted nerves along the spinal cord. Once implanted, these components become a permanent part of the patient's body unless surgically removed.

How Spinal Cord Stimulation Works

Spinal cord stimulation does not cure the underlying condition causing pain. Instead, it works by modifying or masking pain signals as they travel along the spinal cord toward the brain. The device delivers controlled electrical impulses to the dorsal columns of the spinal cord, which interfere with the transmission of pain signals. Depending on the stimulation mode and frequency, the patient may perceive the stimulation as a mild tingling sensation (called paresthesia) in place of pain, or the stimulation may work below the level of perception without any noticeable sensation.

The goal of spinal cord stimulation is not to eliminate pain entirely. A reduction of 50 percent or more in pain intensity is generally considered a successful outcome. The level of relief can vary significantly between patients and may change over time, requiring periodic adjustments to the device's programming and stimulation settings.

Spinal cord stimulators are typically recommended as a last-resort treatment for patients with chronic, intractable pain who have not responded to more conservative approaches, including physical therapy, medications, injections, and prior surgery. Common conditions treated with SCS include failed back surgery syndrome, chronic lower back and leg pain, complex regional pain syndrome (CRPS), and certain types of neuropathic pain.

The Trial and Implantation Process

Unlike most surgical implants, spinal cord stimulators involve a two-stage process: a temporary trial period followed, if successful, by permanent implantation. This trial phase is intended to allow the patient to evaluate the device's effectiveness before committing to a permanent surgical procedure.

Trial Phase

During the trial, a physician uses fluoroscopic (X-ray) guidance to insert temporary leads through a needle into the epidural space near the target area of the spinal cord. The leads are connected to an external pulse generator that the patient wears on a belt or carries externally. The patient typically remains awake or lightly sedated during placement so they can provide feedback on where they feel stimulation. The trial period generally lasts three to seven days, during which the patient evaluates how well the device reduces their pain during normal daily activities.

A trial is considered successful if the patient experiences a reduction in pain of approximately 50 percent or more. If the trial does not provide adequate relief, the temporary leads are removed with no permanent effect on the spine or spinal cord.

Permanent Implantation

If the trial is successful, the patient undergoes a second procedure to implant the permanent system. The surgeon places permanent leads in the epidural space (the trial leads may be replaced with new sterile leads or, in some cases, paddle leads that require a small laminotomy). The implantable pulse generator is then placed in a subcutaneous pocket, typically near the buttocks, lower back, or abdomen, and connected to the leads.

The permanent implantation procedure typically takes one to two hours, is performed under general or local anesthesia with sedation, and is usually done on an outpatient basis. Full recovery generally requires four to six weeks, during which physical activities that involve twisting, bending, or heavy lifting are restricted to prevent lead displacement. Patients are instructed on how to use the external controller before leaving the facility.

Types of Spinal Cord Stimulators

Spinal cord stimulators vary in how they deliver electrical energy, how they are powered, and how stimulation is adjusted. The differences between these systems are significant because they affect device performance, battery life, complication risk, and the patient's daily experience with the implant.

By Power Source

Rechargeable systems use an implanted battery that the patient recharges regularly by holding an external charging device over the skin near the generator. Rechargeable models are typically marketed as longer-lasting — some manufacturers claim 10 or more years of battery life — but they require consistent, ongoing patient compliance with charging routines. The lawsuits against Boston Scientific allege that some rechargeable batteries exhibited instability and performance degradation over time.

Non-rechargeable systems use a fixed-life battery that does not require external charging but must be surgically replaced once depleted, typically every two to five years depending on usage and stimulation settings. Each battery replacement requires a separate surgical procedure.

By Stimulation Mode

Traditional (tonic) stimulation delivers low-frequency electrical pulses that typically produce a noticeable tingling sensation (paresthesia) in the area of pain. This is the oldest form of SCS and the basis on which the earliest devices were approved. Effectiveness depends heavily on precise lead positioning and the patient's ability to tolerate the tingling sensation.

High-frequency stimulation delivers electrical pulses at frequencies above 1,000 Hz (some systems go up to 10,000 Hz), which are designed to reduce pain without producing paresthesia. These systems have been marketed as providing more consistent relief without the sensation of tingling, but they rely on different programming parameters and power consumption profiles than traditional systems.

Burst stimulation delivers groups of electrical pulses in rapid "bursts" rather than continuous streams, intended to more closely mimic natural nerve firing patterns. Like high-frequency stimulation, burst mode generally does not produce paresthesia.

Closed-loop (adaptive) stimulation uses sensors on the leads to measure the electrical activity of the spinal cord in real time and automatically adjusts stimulation intensity based on the patient's body position, activity level, or physiological changes. This is the newest category of SCS technology and is featured in some of the most recent device generations.

Many current-generation spinal cord stimulators offer multiple stimulation modes in a single device, allowing physicians to switch between tonic, burst, high-frequency, and adaptive settings. The lawsuits filed against Abbott and Boston Scientific allege that these multi-waveform capabilities represent significant functional changes from the original devices that received FDA approval, and that these changes were introduced without adequate independent clinical testing.

Abbott and Boston Scientific SCS Product Lines

Abbott and Boston Scientific hold a combined majority share of the spinal cord stimulator market, with an estimated 50,000 SCS devices implanted annually in the United States. Both companies have introduced multiple generations of devices since their original products received FDA Premarket Approval (PMA).

Abbott SCS Devices

Abbott's entire spinal cord stimulator product line traces back to the Genesis SCS, which received its original FDA approval in 2001 under PMA P010032. Since then, Abbott has introduced successive device generations through PMA supplements, including the Abbott Eterna and other models incorporating features not present in the original Genesis design: multi-waveform stimulation (simultaneous tonic, burst, and sub-perception modes), posture-adaptive programming, expanded electrode arrays, Bluetooth-enabled controllers, and redesigned battery architecture and lead systems.

According to the pending federal lawsuits, neither Abbott nor the FDA required independent clinical studies demonstrating the safety and effectiveness of the original Genesis device. The original PMA was granted based on published literature related to similar spinal cord stimulator systems manufactured by other companies. Subsequent device generations, the lawsuits allege, were approved through PMA supplements that treated these substantial modifications as minor changes.

Boston Scientific SCS Devices

Boston Scientific's SCS line originates from the Precision spinal cord stimulator, which received FDA approval in 2004 under PMA P030017. The company has since introduced updated models, including the Precision Montage MRI and the WaveWriter Alpha system, through successive PMA supplements. These newer devices incorporate updated stimulation technology, modified lead configurations, and changes to battery systems and internal components.

As with Abbott, the lawsuits allege that Boston Scientific's original PMA was granted without company-submitted clinical studies and that subsequent device generations introduced through supplements fundamentally altered how the devices function. Plaintiffs contend that these design changes contributed to lead instability, device malfunction, and neurological complications that were not adequately disclosed to physicians or patients.

Known Complications and Failure Rates

Spinal cord stimulators carry well-documented risks. Published medical literature estimates that between 30 and 40 percent of SCS patients experience one or more complications following implantation. These complications are generally divided into two categories: hardware-related failures and biological complications.

Hardware-Related Complications

Hardware failures are more commonly reported than biological complications, and they are the primary focus of the pending lawsuits against Abbott and Boston Scientific.

Biological Complications

Biological complications occur less frequently than hardware failures but can be serious. They include infection at the implant or incision sites, which may require device removal and prolonged antibiotic treatment. Epidural hematoma (bleeding in the epidural space) is a rare but potentially dangerous complication that can cause spinal cord compression. Dural puncture during lead placement can cause severe headaches. Pain at the generator implant site is also commonly reported and, in some cases, has required surgical relocation of the device.

In rarer instances, patients have reported neurological injuries associated with lead placement or stimulation, including new or worsening numbness, weakness, or autonomic dysfunction — problems with involuntary body functions such as blood pressure, heart rate, or bladder control.

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