American Society of Regional Anesthesia and Pain Medicine August 2016 - 18
Advancement in Spinal Cord Neuromodulation
F
or more than a century, electricity has been used for the
neuromodulation of pain pathways. Spinal cord stimulation
(SCS) has been used for the treatment of a variety of pain
conditions over the past 40 years, with a primary indication for
new or persistent back and leg pain after spine surgery, failed back
surgery syndrome, chronic regional pain syndrome (CRPS), and
chronic radiculopathy, as well as treating many other refractory
neuropathic pain conditions.1
During the past 10-15 years, there have been no true evidencebased advances in spinal neuromodulation technology, only
minor improvements on pulse generator programming, software
enhancements and the addition of magnetic resonance imaging
compatibility. The mechanisms by which SCS relieves pain have
yet to be fully elucidated. The gate control theory published by
Melzack and Wall2 in 1965 is the basic premise for SCS. Recent
studies and animal models showed evidence that SCS stimulates
dorsal horn neurotransmitter pain modulators including serotonin,
norepinephrine, γ-aminobutyric acid, and acetylcholine. The
technology also modulates
hyperexcitable/sensitized
dorsal horn wide-dynamicrange neurons implicated in
neuropathic pain states. Some
more recent studies also showed
SCS to antidromically stimulate
the peripheral release of
vasodilatory neurotransmitters
including calcitonin gene-related
peptide and nitric oxide.2
Maged Guirguis, MD
Department of Pain Management
Research Director
Ochsner Health System
New Orleans, Louisiana
Section Editor: Magdalena Anitescu, MD
"[Clinicians] are now eagerly looking
for better, faster, safer, and less
invasive innovations for their ailing
patients, as is the technologically
savvy patient consumer."
Only in more recent years,
high-frequency (HF; 1-10 kHZ) SCS and dorsal root ganglion
stimulation (DRGS) have emerged as modified techniques, devised
to avoid some of the undesirable effects associated with traditional
SCS. These novel platforms also overcome limitations such as the
inability to derive the correct combination of pulse width, frequency,
and amplitude of the electrical waveform needed to address the
individual's pain or positional/postural effects due to shifts in the
relative distance between the stimulating electrodes and the dorsal
column.
HF STIMULATION
Traditional SCS devices deliver paresthesia-based therapies in
the range of 2-1,200 Hz, most commonly 50-100 Hz. A recently
approved device delivers HF SCS therapy at 10,000 Hz or nearly a
10-fold increase from previous SCS devices (Figure 1). In HF SCS,
leads and pulse generator placement follow similar protocols as in
traditional SCS, with only one exception: Leads are placed using
anatomical landmarks rather than adjustments made based on
the patient's feedback on paresthesia. Dual leads are placed in a
staggered array between T8 and T11 to maximize pain relief. This
18
2
Maunak V. Rana, MD
Advocate Illinois Masonic Medical
Center, Department of Anesthesiology
University of Illinois, Department of
Anesthesiology
Chicago, Illinois
procedure results in greater
patient comfort, as patient
feedback (on pain-paresthesia
overlap) is not required
intraoperatively, allowing for
use of general anesthesia
during implant.3
Recently, Kapural et al4
reported results from a
randomized controlled trial
(RCT) using HF10 therapy. In
this study, known as the SENZA-RCT, HF10 therapy demonstrated
superiority over traditional SCS for the long-term treatment of
both chronic, intractable back and leg pain. Among subjects
randomized to HF10 therapy and traditional SCS, 90 and 81
subjects were implanted with permanent devices, respectively.
During 12-month follow-up, the results demonstrated higher
responder rates for HF10 therapy at all endpoints (p < .001). Back
pain responder rate was approximately 80% throughout the trial
for the HF10 therapy cohort compared with approximately 50% for
the traditional SCS cohort. Similar responder rates were reported
for leg pain (approximately 80% for HF10 therapy and 50-55%
for traditional SCS). The study also showed the impact of HF10
therapy on decreasing opioid usage, increasing functional capacity,
and improving subjects' satisfaction. What was also remarkable in
this study was that two-thirds of HF10 therapy subjects achieved
profound back and leg pain relief (≤2.5 cm on a visual analog
scale) and more than one-third decreased or eliminated opioid
usage at 12 months. In addition, this study's results were very
similar to three published studies reporting on the effects of HF10
therapy.4
American Society of Regional Anesthesia and Pain Medicine
2016
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