156 Neuroimaging Biomarkers of Chronic Neuropathic Pain and its Modulation: Resting State fMRI Signals during Spinal Cord Stimulation.

Neurosurgery. 2012 Aug;71(2):E562

Authors: Oluigbo C, Abduljalil A, Yang X, Kalnin A, Knopp MV, Rezai AR

Abstract
INTRODUCTION: : Chronic pain affects 70 million American and its cost to the US economy is over $150 billion per annum. A critical first step in the design of innovative treatments for chronic pain is the development of new methods to evaluate pain and the cerebral 'signature' for its perception and modulation, and in so doing, be able to monitor the effect of new therapies on pain in an objective fashion.
METHODS: : Subjects with fully implanted thoracic epidural spinal cord stimulator (SCS) for the treatment of chronic refractory neuropathic leg pain underwent resting state functional MRI scans with the SCS in the OFF and ON states. Pain quantification was based on the Visual-Analog Scale (VAS). Images were acquired using a 3 Tesla MRI system. Prior to the study, a detailed safety assessment of the devices to be used in the MRI field in this study was performed. The amplitude of low frequency fluctuation (ALFF) and fractional ALFF (fALFF) were calculated using the Fourier transform of the temporal data. Seed-based correlation analysis was used to assess the functional connectivity.
RESULTS: : We demonstrated that spinal cord stimulation was associated with significant changes in ALFF in patients undergoing resting state fMRI. The changes were more prominent in the region of the medial orbitofrontal cortex, anterior insula, nucleus accumbens and amygdala (Figures 1a, 1b). Seed-based analysis of similarity coefficients in ALFF for the medial orbitofrontal cortex, anterior insula, nucleus accumbens and amygdale showed quantifiable changes in these regions with the SCS in the OFF state compared to the ON states at stimulation parameters associated with optimal pain reduction, paresthesia perception and discomfort (Figure 2a-d).
CONCLUSION: : Resting state fMRI in patients receiving spinal cord stimulation for neuropathic leg pain showed robust, consistent and quantifiable changes in the ALFF in the medial orbitofrontal cortex, anterior insula, nucleus accumbens and amygdala. Large-amplitude, spatially correlated fluctuations in resting state fMRI signals may be a neuroimaging surrogate for higher order pain perception and its modulation.

PMID: 22811145 [PubMed - in process]