Electrochemical Skin Conductance Alterations during Spinal Cord Stimulation: An Experimental Study

Abstract

Despite the well-known clinical effects of spinal cord stimulation (SCS), the mechanisms of action have not yet been fully unraveled. The primary aim of this study was to measure whether electrochemical skin conductance, as a measure of peripheral sympathetic autonomic function, is altered by SCS. A second aim was to compare skin conductance levels of patients with failed back surgery syndrome (FBSS) with age- and sex-matched healthy controls. Twenty-three patients with FBSS treated with SCS participated in this study. Sudomotor function was measured with the SudoscanTM instrument on the hands and feet during SCS on and off states. Difference scores in skin conductance between patients and age- and sex-matched healthy controls were calculated. Normal sudomotor function at the painful lower limb was revealed for 61% of the patients when SCS was activated. Skin conductance levels were not altered between on and off states of SCS. Differences in scores between patients and healthy controls were significantly different from zero. This study showed that SCS does not influencing the sympathetic nervous system in patients with FBSS, as measured by skin conductance levels. Moreover, it suggested that there is no normalization of the functioning of the sympathetic nervous system, despite the effectiveness of SCS to reduce pain intensity.

The Role of Autonomic Nervous System in Pain Chronicity

“…Spinal cord stimulation (SCS) can provide pain relief and improvement of other symptoms in visceral and somatic pain by neuromodulation of various targets within the spinal cord. For example, SCS for refractory abdominal pain can improve chronic nausea and vomiting [100]. For neuropathic visceral abdominal pain, clinicians target the upper-mid thoracic level where splanchnic nerves emerge from the spinal cord.…”

From pain intensity to a holistic composite measure for spinal cord stimulation outcomes

“…Therefore, we believe that complementary to the self-reporting of the patients, more objective measurements are needed to acquire insight into the complete representation of a patient and the influence of pain on this individual patient. Several more objective values have been explored to measure the effect of neuromodulation with negative results for volatile organic compounds [54], and skin conductance [55]. Based on neurophysiological measures, SCS largely inhibits non-nociceptive somatosensory processing (decrease in somatosensory evoked potential amplitudes) [56].…”