We have used epidural spinal cord stimulation (SCS) for pain control for the past
15 years. An analysis of our series of 235 patients has clarified the value of specific
prognostic parameters in the prediction of successful SCS.
Patients were followed up for periods ranging from 6 months to 15 years with a mean
follow-up of 66 months. The mean age of the 150 men and 85 women in the study was
51.4 years. Indications for SCS included failed back syndrome (114 patients), peripheral
vascular disease (39 patients), peripheral neuropathy (30 patients), multiple sclerosis
(13 patients), reflex sympathetic dystrophy (13 patients), and other etiologies of
chronic intractable pain (26 patients).
One hundred and eighty-nine patients received permanent devices; 111 (59%) of these
patients continue to receive satisfactory pain relief. Pain attributable to failed
back syndrome, reflex sympathetic dystrophy, peripheral vascular disease of lower
limbs, multiple sclerosis, and peripheral neuropathy responded favorably to spinal
cord stimulation. In contrast, paraplegic pain, cauda equina syndrome, stump pain,
phantom limb pain, and primary bone and joint disease pain did not respond as well.
Cases of cauda equina injury had promising initial pain relief, but gradually declined
after a few years. After long-term follow-up, 47 of the 111 successfully implanted
patients were gainfully employed, compared with 22 patients before implantation. The
successful patients reported improvements in daily living as well as a decrease in
analgesic usage. Multipolar stimulation systems were significantly more reliable (p
< 0.001) than unipolar systems. Complications included hardware malfunction, electrode
displacement, infection, and tolerance.
Aside from etiologies of pain syndromes as a prognostic factor, we have identified
other parameters of success. In patients who have undergone previous surgical procedures,
the shorter the duration of time to implantation, the greater the rate of success
(p < 0.001). The diagnosis of failed back syndrome must be considered a confounding
factor in our analysis. Those patients whose pain did not follow a surgical procedure
had better responses to SCS than patients who had multiple surgical procedures prior
to their first implant. The advent of multipolar systems has significantly improved
clinical reliability over unipolar systems. Age, sex, and laterality of pain did not
prove to be of significance.