Background: Despite the good clinical results elicited by spinal cord stimulation (SCS), the
physiological basis of action of SCS is widely unknown. Inhibition of somatosensory evoked
potential (SEP) amplitudes by SCS has been described, but it is unclear whether this displays
dose dependency. Moreover, it is unknown whether the pain-relieving effect elicited by SCS
correlates with the inhibition of SEPs. Finally, this study aimed to answer the question whether
there is a difference in the effect on SEPs between SCS and transcutaneous electrical nerve
stimulation (TENS), thus between central nervous system stimulation and peripheral nervous
system stimulation.
Methods: Ten patients (4 men and 6 women, age range 40-77 years) with neuropathic lower
limb pain were included in the study. All patients had implanted SCS systems with percutaneous
type electrodes. Cortical SEPs under SCS and TENS were measured without stimulation, under
stimulation at perception threshold (PT), and at maximal threshold (MT) in a crossover design.
Results: Cortical SEP amplitudes were significantly inhibited by SCS. Stimulation at PT and at
MT both led to a statistically significant inhibition of the SEP amplitude. The difference between
amplitude reduction at PT and MT showed a tendency towards significance. The degree of SEP
amplitude inhibition did not correlate with pain relief. Inhibition of SEP amplitudes by TENS was
weaker than that elicited by SCS. The average percentage of amplitude reduction at MT was
twice as high under SCS as it was under TENS. No effects on SEP latencies were seen.
Conclusions: SCS exerts a significantly stronger inhibition of SEP amplitudes than TENS. The
data hint at a dose dependency of SCS-induced SEP amplitude inhibition. No correlation between
SEP amplitude inhibition and pain relief was found.
Key words: spinal cord stimulation, SCS, transcutaneous electrical nerve stimulation, TENS,
neuropathic pain, somatosensory evoked potentials, SEP
The Short-Term Effects of Difference Frequency of Transcutaneous Electrical Nerve Stimulation on Pain Relief using c-fos Expression in Spinal Cord with Knee Osteoarthritis Rats
