Spinal cord stimulation does not change peripheral skin blood flow in patients with neuropathic pain

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

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 Sudoscan^TM 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.

Objective Measures to Characterize the Physiological Effects of Spinal Cord Stimulation in Neuropathic Pain: A Literature Review

OBJECTIVE

The physiological mechanisms behind the therapeutic effects of spinal cord stimulation (SCS) are only partially understood. Our aim was to perform a literature review of studies that used objective measures to characterize mechanisms of action of SCS in neuropathic pain patients.

MATERIALS AND METHODS

We searched the PubMed data base to identify clinical studies that used objective measures to assess the effects of SCS in neuropathic pain. We extracted the study factors (e.g., type of measure, diagnoses, painful area[s], and SCS parameters) and outcomes from the included studies.

RESULTS

We included 67 studies. Of these, 24 studies used neurophysiological measures, 14 studies used functional neuroimaging techniques, three studies used a combination of neurophysiological and functional neuroimaging techniques, 14 studies used quantitative sensory testing, and 12 studies used proteomic, vascular, and/or pedometric measures. Our findings suggest that SCS largely inhibits somatosensory processing and/or spinal nociceptive activity. Our findings also suggest that SCS modulates activity across specific regions of the central nervous system that play a prominent role in the sensory and emotional functions of pain.

CONCLUSIONS

SCS appears to modulate pain via spinal and/or supraspinal mechanisms of action (e.g., pain gating, descending pain inhibition). However, to better understand the mechanisms of action of SCS, we believe that it is necessary to carry out systematic, controlled, and well-powered studies using objective patient measures. To optimize the clinical effectiveness of SCS for neuropathic pain, we also believe that it is necessary to develop and implement patient-specific approaches.

The use of sensory electrical stimulation for pressure ulcer prevention

Pressure ulcer prevention is critically important for many people with reduced mobility. The authors investigated whether sensory (sub-motor-threshold) electrical stimulation (ES) may provide a convenient preventive intervention. A double-blinded, repeated measures study design was used to test the hypothesis that repeated use of sensory surface ES improves tissue health status in individuals with motor paralysis. Six adult males with complete spinal cord injury (SCI) were randomly assigned to treatment or control groups. The treatment group received the ES intervention, whereas the control group received a control sham intervention. Repeated tissue health assessments included transcutaneous oxygen tension (T(c)PO(2)), interface pressure mapping, and gluteal computed tomography (CT) studies. An initial increase in T(c)PO(2) following use of subthreshold ES was observed but was not sustained at follow-up. No statistically significant changes before and after treatment were found in regional T(c)PO(2), gluteal muscle area or pressure distribution. Thus subthreshold ES does not appear to have any sustained effects on tissue health status indicative of reduced pressure ulcer risk for individuals with SCI. This implies that a contractile muscle response is critically important and further that subthreshold ES is unlikely to prevent pressure ulcers. Further studies are needed to find solutions for preventing pressure ulcers in high-risk populations.

Effect and safety of spinal cord stimulation for treatment of chronic pain caused by diabetic neuropathy

AIM

Spinal cord stimulation (SCS) has been shown effective as a therapy for different chronic painful conditions, but the effectiveness of this treatment for pain as a result of peripheral diabetic neuropathy is not well established. The primary objectives of this study were to evaluate the effect and safety of SCS for treatment of pain and the effects on microcirculatory blood flow in the affected areas in patients with refractory peripheral diabetic neuropathy.

METHOD

The study was designed as a prospective, open-label study. Data were collected during screening, at implant and at regular intervals, after initiation of therapy. Eleven diabetic patients with chronic pain in their lower limbs and no response to conventional treatment were studied. The SCS electrode was implanted in the thoracic epidural space. Neuropathic pain relief was assessed by Visual Analogue Scale (VAS) and microcirculatory skin perfusion was measured with Laser Doppler flowmetry.

RESULTS

Nine subjects had significant pain relief with the percutaneous electrical stimulator. Average pain score for all nine patients was 77 at baseline and 34 at 6 months after implantation. At the end of the study, eight of nine patients continued to experience significant pain relief and have been able to significantly reduce their pain medication. For six of them, the stimulator was the sole treatment for their neuropathic pain. No significant changes in microcirculatory perfusion were recorded.

CONCLUSION

Spinal cord stimulation offers an effective and safe therapy for chronic diabetic neuropathic pain.