Available online 12 January 2013
Publication year: 2013
Source:World Neurosurgery
Objective Spinal cord stimulation via epidurally implanted electrodes is a widely used treatment for medically intractable neuropathic pain of different origins. As tonic electrical stimulation evokes paresthesias covering the painful area this method has never been proven scientifically to be superior to placebo. Recently burst stimulation was developed, delivering closely spaced high frequency stimuli to the spinal cord, which does not generate paresthesias. Methods A randomized placebo controlled trail comparing three stimulation paradigms (burst, tonic, and placebo) was performed on 15 consecutive pain patients. In contrast to tonic stimulation, burst stimulation was able to provide pain relief without the need for paresthesias, permitting a double blinded placebo controlled approach. Primary outcome measures were Visual Analogue Scale (VAS) pain scores for back pain, limb pain and general pain. Secondary outcome measures consisted of the Pain Vigilance and Awareness Questionnaire (PVAQ), measuring attention to pain and pain changes, and VAS of the worst, least and momentary pain. In a subgroup of 5 patients a source localized EEG was performed in 4 conditions: baseline, tonic, burst and placebo stimulation. Burst stimulation was able to improve back, limb, and general pain by 51, 53 and 55%, and tonic stimulation by 30, 52 and 31% Pain now, least and worst pain were respectively improved by 50, 73 and 36% by burst stimulation and 26,46 and 13% by tonic stimulation. In comparison to placebo burst was significantly better for all measurements, corrected for multiple comparisons. The largest changes differences were however obtained in the PVAQ: burst improved the attention to pain and pain changes, whereas tonic and placebo worsened these measurements. The EEG analysis demonstrates burst stimulation activates the dorsal anterior cingulate and right dorsolateral prefrontal cortex more than tonic stimulation. Conclusions The differences between tonic and burst stimulation are likely due to a more selective modulation of the medial pain pathways by burst stimulation as shown by the dorsal anterior cingulate cortex activation.
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