“Failed Back” Syndrome
A 55-year old male with persisting back and leg pain following back
Persistent or worse pain after a patient has back surgery is due to either a new or
recurrent ruptured disc, neural foramen narrowing from removal of the disc, or most
often scar tissue around the nerve (epidural fibrosis). If the patient has had a fusion, a
pedicle screw could produce nerve root injury or irritation.
Many patients have a brief recurrence of pain after surgery, but it will go away within
several weeks. If the pain persists, the surgeon will do further testing to see if there is
anything that can be helped with further surgery. If the testing shows no new ruptured
disc or other correctible lesion, or if it shows scar tissue around the nerve, other options
are available. Often physical therapy, injections, blocks, or medications (i.e., Gabapentin,
Lyrica, Elavil, Pamelor) will be tried and are often successful. If not, spinal cord
stimulation is an available option.
Spinal cord stimulation has been available for more than 25 years. Recent technological
advancements have made it more effective and reduced problems associated with
Spinal cord stimulation involves placing a series of electrodes into the epidural space,
usually over the dorsal region of the thoracic cord.
Figures 1a and b: Schematic demonstrating stimulating electrodes over the dura, connected to a subcutaneous power source in figure a.
These electrodes provide a small electrical current that modifies the sensory signal ascending the spinal cord from a message of “pain” to a message of “tingling”. The electrode is connected to a pacemaker-like device implanted subcutaneously that delivers
the signals. The strength and other parameters of the signal can be adjusted through the patient’s skin by using a hand held programmer.
Many of the systems now available have rechargeable batteries that can be recharged through the skin, avoiding the need to change the battery by a brief surgical procedure.
Spinal cord (dorsal column) stimulators are placed in two stages. The first stage is done with the patient awake. The patient is brought into the operating and the back is infiltrated with local anesthetic above the old surgerical site and the electrodes are directed into the epidural space through a needle and manipulated into the correct location under fluoroscopic guidance. The electrodes are then turned on, and the patient asked to describe where he feels the stimulation. The electrodes are moved until the patient feels stimulation over all of the areas that are usually painful. The electrodes are then secured and the patient returns home for a trial utilizing an external power source. During the trial it is important that the patient resume his normal activity, as pain is often related to activity. Also, patients should not make significant changes in their medication. If the patient gets greater than 50% relief of his pain, the second stage involves implanting the pacemaker/generator/battery. This is done under general anesthesia, but also as an outpatient. The battery/generator is placed under the skin, usually in the buttocks. Insurance companies require a patient to have experienced his pain for at least 6 months, and to have completed a program of medication, blocks, and physical therapy. All insurance companies require a neuropsychological evaluation before approving the procedures.
Risks of implantation of a stimulator include an 5% risk of infection, 10% risk of leads moving or breaking, and a 1% risk of the generator failing. The battery in the rechargeable systems is predicted to last for 9 years, although they have not been available long enough to verify that length of function. Studies have shown that over 80% of patients successfully implanted with a spinal cord stimulator are still using their system 5 years later, and we have many patients with over 10 years of use.
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