“Failed back surgery syndrome” (FBSS) is defined as persistent or recurrent pain, primarily involving the lower back and/or legs, despite having undergone spinal surgery. By some estimates, up to 40 percent of spinal surgeries result in FBSS. For people with continued, disabling, radiating pain following surgery for a herniated disc, the American Pain Society recommends discussing the option of spinal cord stimulation therapy with a doctor.
This novel approach involves applying electrodes that emit pulses of electricity directly into spinal nerves. The exact way in which this reduces pain is not entirely understood, but one theory is that the electrical pulses “hijack” the nerves and override the pain signals that otherwise would be traveling along the nerve pathway, thus interfering with the transmission of pain signals to the brain. When the electrical pulses are switched on, the patient feels numbness or tingling in the affected areas, which is presumably preferable to the sensation of pain.
Candidates for spinal cord stimulation therapy generally undergo a trial period of about five to seven days, during which electrodes are temporarily inserted into the spine. Local rather than general anesthesia is used so that the patient can remain awake to provide feedback to the surgeon regarding the optimal placement of the electrodes. The electrodes are then attached, via wires called “leads,” to an external pulse-generating device that’s worn outside the body. If the system proves to work well and alleviate pain during the trial period, a permanent implantable pulse generator (IPG) can then be installed, typically in the buttocks or lower abdominal region. This is usually performed under sedation or general anesthesia.
The IPG is then controlled remotely with a wireless external control unit, which the patient can use to turn the IPG on or off, or to adjust the device’s intensity or other settings. The device is not intended to be used constantly. Commonly, it is used for one or two hours at a time, three or four times a day. Like a cellphone, it needs to be turned off during takeoffs and landingswhen traveling by air. Likewise, it should be turned off before walking through antitheft systems in retail stores, because these security systems are known to trigger unpleasant surprise jolts when the IPG is left on.
In clinical studies, spinal cord stimulation is beneficial between 50 and 70 percent of the time. However, roughly one-quarter of patients experience complications, such as gradual displacement (“migration”) of the electrodes and infection at the site of implantation. Some IPG units need to have their batteries replaced eventually, usually after a few years. In very rare cases, complications include internal bleeding, nerve damage, paralysis and death.