Functional magnetic resonance imaging: cerebral function alterations in subthreshold and suprathreshold spinal cord stimulation
Received 26 December 2017
Accepted for publication 2 July 2018
Published 24 October 2018 Volume 2018:11 Pages 2517—2526
Checked for plagiarism Yes
Review by Single anonymous peer review
Peer reviewer comments 2
Editor who approved publication: Dr Erica Wegrzyn
Sander De Groote,1 Mats De Jaeger,1 Peter Van Schuerbeek,2 Stefan Sunaert,3 Ronald Peeters,3 Dirk Loeckx,4 Lisa Goudman,1,5 Patrice Forget,6 Ann De Smedt,7 Maarten Moens1,2,8
1Department of Neurosurgery, Universitair Ziekenhuis Brussel, Brussels, Belgium; 2Department of Radiology, Universitair Ziekenhuis Brussel, Brussels, Belgium; 3Department of Radiology, Universitair Ziekenhuis Leuven, Leuven, Belgium; 4COMETRIX, Leuven, Belgium; 5Pain in Motion International Research Group, Department of Physiotherapy, Human Physiology and Anatomy, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussel, Belgium; 6Department Anesthesiology, Universitair Ziekenhuis Brussel, Brussels, Belgium; 7Department of Neurology, Universitair Ziekenhuis Brussel, Brussels, Belgium; 8Center for Neurosciences (C4N), Vrije Universiteit Brussel (VUB), Brussels, Belgium
Background and purpose: Failed back surgery syndrome (FBSS) is a common and devastating chronic neuropathic pain disorder. Conventional spinal cord stimulation (SCS) applies electrical suprathreshold pulses to the spinal cord at a frequency of 40–60 Hz and relieves pain in FBSS patients. During the last decade, two major changes have emerged in the techniques of stimulating the spinal cord: paresthesia-free or subthreshold stimulation and administration of higher frequency or higher amounts of energy to the spinal cord. Despite the positive clinical results, the mechanism of action remains unclear. A functional MRI (fMRI) study was conducted to investigate the brain alterations during subthreshold and suprathreshold stimulation at different frequencies.
Methods: Ten subjects with FBSS, treated with externalized SCS, received randomly four different stimulation frequencies (4 Hz, 60 Hz, 500 Hz, and 1 kHz) during four consecutive days. At every frequency, the patient underwent sub- and suprathreshold stimulation. Cerebral activity was monitored and assessed using fMRI.
Results: Suprathreshold stimulation is generally accompanied with more activity than subthreshold SCS. Suprathreshold SCS resulted in increased bilateral activation of the frontal cortex, thalamus, pre- and postcentral gyri, basal ganglia, cingulate gyrus, insula, thalamus, and claustrum. We observed deactivation of the bilateral parahippocampus, amygdala, precuneus, posterior cingulate gyrus, postcentral gyrus, and unilateral superior temporal gyrus.
Conclusion: Suprathreshold stimulation resulted in greater activity (both activation and deactivation) of the frontal brain regions; the sensory, limbic, and motor cortices; and the diencephalon in comparison with subthreshold stimulation. Each type of frequency at suprathreshold stimulation was characterized by an individual activation pattern.
Keywords: spinal cord stimulation, fMRI, subthreshold, suprathreshold, frequency
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