Brain activity modulation by spinal cord stimulation in intractable neuropathic pain

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Abstract

Introduction: After four decades of successful use of spinal cord stimulation (SCS) as treatment
tool in neuropathic pain, it is clear that the mechanisms of SCS are much more complicated than
stated in the gate-control theory. In this fMRI study we investigated the brain activity modulation
related to SCS in failed back surgery syndrome patients with intractable neuropathic pain.
Subjects and methods: All selected patients suffered from pain in the lower back and legs for at
least three years. Seven patients had left sided, five right sided and two bilateral pain. The fMRI-
experiment was performed 1 week after implantation of a spinal cord trial stimulator (Medtronic,
USA). The stimulation parameters were optimized for each patient. Patients were not allowed to use
pain medication or SCS on the day of the fMRI-experiment.
During the fMRI measurement, 30s blocks with and without stimulation were alternated while the
patient had to rate his/her pain continuously on a VAS-score in order to focus attention on the pain.
We performed the experiment twice: once before and once after 1h of continuous stimulation. All
scans were done on a 1.5T Philips MRI-scanner with an EPI (TR/TE=3000/35ms; 30 slices;
thickness/gap=3/1mm; dynamic time=3s) sequence. Processing was done in SPM5 and included a
1-sample T-test for each experiment. Like other authors (1,2), we performed a left-right flip of the
data of the right stimulated patients.
Results: The results of the 1-sample T-test for the first and second fMRI are summarized in fig.1.
Thresholding corresponding to p(uncorrected)p(uncorrected)thalamic region (Fig.2). The second fMRI showed a decreased activity in all regions commonly
associated with neuropathic pain processing (3).
Discussion/Conclusion: Although the stimulator is placed at the level of the spinothalamic tract, it
is the thalamus which plays the key role in the pain controlling effects of SCS. It is known (3) that
the thalamus is the main gate to cerebral pain processing and has connections to all other pain
processing regions in the brain. The anterior cingulate, insular and frontal brain regions modulate
pain-related behavior.
References:
(1) Stancak A. (2008); European Journal of Pain; 12:137-148
(2) Rache D. (2005); Schmerz; 19:497-505
(3) Saadé NE. (2008); Progress in Neurobiology; 86:22-47
Original languageEnglish
Title of host publicationESMRMB
Publication statusPublished - 2009
EventUnknown -
Duration: 1 Jan 2009 → …

Conference

ConferenceUnknown
Period1/01/09 → …

Keywords

  • fMRI
  • Externalised SCS

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