First results of a comparison study between SCS responders and non-responders with fMRI

Research output: Chapter in Book/Report/Conference proceedingConference paper

Abstract

Introduction: After the introduction of the gate-control theory in 1965, the neurosurgeons were
convinced they could control neuropathic back pain by placing a spinal cord stimulator (SCS) at the
spinothalamic tract. Today, it is clear that the brain is playing a key role in the therapeutic effects of
SCS and can make the difference between responders and non-responders to the therapy. This fMRI
study focusses on the differences in brain activity related to SCS between responders and non-
responders.
Subjects and methods: All selected patients suffered from pain in the lower back and left leg for at
least three years. Seven patients were responders and four non-responders. 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. 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. Due to our small number of patients we only
performed a fixed-effects analysis using SPM5.
Results: The results are summarized in figures 1-4. Thresholding corresponding to
p(uncorrected)In the responders group we found reactions in regions involved in sensory (S1/S2), affective (ACC)
and cognitive (frontal) processing of pain and the thalamus. In the non-responders group, a different
and much more complex pattern of brain activity was found with no reaction at the thalamus and a
different pattern of cingulate activity (fig.5).
Discussion/Conclusion: Where the gate-control theory states that pain can be controlled by switching
a relay at the spine by SCS, our results suggest that the therapeutic effects result from an inhibition of
thalamic activity. The thalamus act as a gate to cerebral pain processing and has connections to all
other pain processing regions like the ACC which act as a regulator for pain related behavior (1). These
results are in line with a PET study (2) on a more general group of chronic pain patients.
References:
(1) Saadé NE. (2008); Progress in Neurobiology; 86:22-47
(2) Nagamachi S. (2006); Anals of Nuclear Medicine; 20:303-310
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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