Science at the heart of medicine
Percutaneous Spinal Cord
Stimulator Placement: The Do’s,
the Don’ts, and the How
Matthew S. Lazarus, MD, PhD; Edwin Gulko, MD;
Ari J. Spiro, MD; Todd S. Miller, MD; Allan L.
Brook, MD
#951
Disclosures
MSL: None
EG: None
AJS: None
TSM: None
ALB: Medtronic, Carefusion, DFINE
Outline
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Background
Mechanism of Action
Indications
Patient Selection and
Contraindications
• Technique
> Trial Placement
> Permanent Placement
> Lead Placement
> Programming
> Technical Challenges
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Complications
Summary of Our Experience
Conclusions
References
Background
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Spinal cord stimulation (SCS) is a form of neuromodulation that
effectively treats a number of pain conditions.
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Leads are placed in the epidural space, frequently via a percutaneous
approach. The leads are connected subcutaneously to a pulse
generator, which provides electrical stimulation via a program tailored to
each individual patient.
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SCS provides welcomed relief to patients that have failed either surgical
or conventional medical management.
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SCS is reversible and safe.
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Proper patient selection will optimize effectiveness and minimize
complications.
Mechanism of Action
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The physiologic basis of spinal cord stimulation is incompletely understood, and
continues to be an active area of research.
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The framework for SCS developed on the basis of the “gate-control” theory9,12,13.
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Activation of non-nociceptive fibers inhibits central transmission from nociceptive fibers,
preventing painful stimuli from reaching the thalamus.
Direct electrical stimulation of non-nociceptive Ab fibers in the dorsal column should
therefore diminish pain transmission, via a central mechanism.
While the “gate-control” theory is informative, it does not explain why spinal cord
stimulation is primarily effective for treatment of neuropathic pain, but not
nociceptive pain12,13.
Mechanism of Action
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A complex interplay of excitatory and inhibitory neurotransmitters contributes to
the mechanism of SCS pain relief8,11,12,13.
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Following SCS, substance P increases, as well as inhibitory neurotransmitters such as
GABA. Excitatory neurotransmitters (glutamate, aspartate) decrease.
GABA activity appears to be particularly important for the effects of SCS. Pain relief
following SCS can be blocked by a GABA-B receptor antagonist. Intrathecal
administration of the GABA-B receptor agonist Baclofen can enhance SCS efficacy.
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The efficacy of SCS for anginal or ischemic pain is likely through a separate
mechanism, primarily via peripheral effects on the sympathetic nervous system
and release of vasodilatory compounds13.
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Paresthesia induction over the region of pain is critical for SCS success. However,
it is unknown if this is an epiphenomenom, or directly related to the mechanism of
pain suppression13.
Indications
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Indications for SCS are constantly being reviewed, revised, and researched3,5,13.
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SCS neuromodulation has been utilized and studied in chronic pain conditions,
neuropathic pain associated with various diseases, and mixed neuropathicvascular disorders5,10,12,13.
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In 2014, the Neuromodulation Appropriateness Consensus Committee (NACC),
evaluated available data and published “The appropriate use of neurostimulation
of the spinal cord and peripheral nervous system for the treatment of chronic pain
and ischemic diseases”5.
Indications
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Radicular pain in failed back surgery syndrome (FBSS) is relieved by spinal cord
stimulation.
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FBSS (also known as post-laminectomy pain) consists of recurrent/persistent pain
following surgery of the lumbosacral spine.
Prospective Randomized Controlled Multicenter Trial of the Effectiveness of Spinal Cord
Stimulation (PROCESS) by Kumar et al.6, randomized 100 FBSS patients with
predominant leg pain of neuropathic radicular origin between SCS and conventional
medical management (CMM) or CMM alone.
Kumar et al. demonstrated superior pain relief, health related quality of life, and functional
capacity at 6 months, and sustained pain relief at 24 months.
USPSTF recommendation is Grade A for SCS “in the early treatment algorithm in FBSS”.
Complex regional pain syndrome (CRPS) is a neuropathic condition characterized
by intractable pain, autonomic dysfunction, edema, vasomotor changes, and
movement disorder.
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Neuromodulation Therapy Access Coalition published Grade A recommendation
supporting the use of SCS for CRPS10.
Indications
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SCS has been used to control neuropathic pain associated with various diseases
such as painful diabetic peripheral neuropathy (PDPN), HIV neuropathy, postherpetic neuralgia, chronic visceral pain, post- amputation pain, and chest wall
pain syndromes, amongst others.
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NACC5 recommendations for SCS use in the control of neuropathic pain
associated with various diseases is mixed:
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SCS should be used earlier in the treatment algorithm for PDPN if conventional
pharmacological treatment is insufficient for pain relief.
SCS is appropriate therapy for HIV neuropathy.
With limited outcomes data available, SCS is recommended on a case-by-case basis for
treatment of various visceral pain syndromes and spinal cord injury.
Neuromodulation may be utilized for post-amputation pain, however given that the
etiology for pain may vary, results are unpredictable.
Caution is advised when using conventional SCS for treatment of chest wall pain.
SCS for axial low back pain, which has seen a resurgent interest, is supported by
the NACC; USPSTF grade is I (Insufficient data)5.
Indications
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SCS has also been used to control mixed neuropathic-vascular conditions,
including ischemic pain syndromes, Raynaud’s syndrome, and chronic refractory
angina resistant to therapy (CART).
The NACC recommends early intervention in patients with Raynaud’s syndrome
and other painful ischemic disorders.
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However, due to lack of randomized controlled trials (RCTs) and well-designed clinical
studies, the recommendation is Grade C.
The SCS-EPOS study2 showed SCS provides significantly better limb survival rate for
patients with nonreconstructable critical leg ischemia, compared with conservative
treatment.
SCS is considered to act by a combination of electroanalgesia at the spinal cord
and anti-anginal mechanisms, which result in improved quality of life for patients
with CART.
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Based on recent studies, SCS has an A level recommendation for use in CART.
However, SCS is not a widely accepted treatment option in the cardiology community.
Patient selection and Contraindications
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Success of SCS is highly dependent on patient compliance and cooperation.
Patients with the cognitive ability and willingness to both manage their SCS
equipment and follow-up reliably are the most likely to have a successful course.
Patient’s with identifiable physiologic causes of pain, who have failed conservative
medical management, are the most appropriate candidates3,5,12,13.
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Pain with a large psychiatric/somatization component is less likely to be relieved by SCS.
Pain related to cancer can be addressed on a case-by-case basis. Stable patients with pain
related to tumor resection may be good candidates. Patients with diffuse metastatic
disease are less likely to benefit from SCS.
Relative contraindications include ongoing psychiatric or substance abuse
disorders, ongoing litigation (or other potential source of secondary gain), or
cognitive limitations3,13.
Additional relative contraindications include pregnancy, pacemaker/AICD
placement, or anticoagulation/anti-platelet therapy3,5,13.
Absolute contraindications are similar to those for surgery in general3,13.
Technique- Trial Period
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A unique part of SCS treatment is the use of a trial period, prior to permanent
implantation3,12.
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This improves patient selection.
The trial period requires the patient to play an active role—they must monitor their
symptoms and be able to effectively communicate with the physician.
Conscious sedation is preferred when possible3,4,.
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Conscious sedation allows communication throughout the procedure. The patient should
communicate the region and intensity of paresthesia. This will optimize lead coverage
and provide for an accurate trial result.
If general anesthesia is required, lead coverage can be evaluated with intraoperative
somatosensory evoked potentials4.
Technique- Trial Period
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Temporary leads are placed (technique for lead placement will be discussed
subsequently), and sutured externally to the skin.
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Following initial lead placement, bedside programming tailors the appropriate stimulation
parameters to induce paresthesia in the affected region. The lead position can be
adjusted intraoperatively, as needed.
The leads are activated initially at the time of placement, and then throughout the trial
period.
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In our institution, the trial period lasts approximately 5 days. The range in other
institutions is 3 days to 3 weeks13.
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The patients are seen in the office at the conclusion of the trial.
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The course of the trial is discussed, generally a reduction of pain by 50% or greater is
considered successful.
Reduction in the pain medication is closely monitored and advised, especially after the
permanent implant.
The temporary leads are removed, regardless of the decision whether to proceed, to
prevent infection.
Technique- Permanent placement
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Permanent placement includes both the placement of epidural stimulator leads, as
well as a pulse generator underneath the skin.
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The patient is premedicated with Ancef (clindamycin is an alternative if there is an
allergy).
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Similar to the trial placement, conscious sedation is preferred, as it allows
communication with the patient during the procedure.
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Two leads are inserted into the epidural space parasagitally, along the midline,
and positioned at the level appropriate for the indication.
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Interactive intraoperative testing is performed to optimize lead position.
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Leads are anchored to the fascia, and then tunneled subcutaneously to the
eventual pulse generator site.
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A subcutaneous pocket is created to hold the pulse generator. This is usually
contralateral to the patient’s dominant hand, which makes it easier for the patient
to reach the site with the external programmer. This is determined by patient
preference.
Technique- Lead Placement
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Vertebral level for placement is largely determined by the indication3,13.
Level13
Headache/neckache
C1-C2, or occipital
Upper extremity
C5-T1
Refractory angina
C6-T1, left of midline
Lower back
T8-T10
Lower extremity
T9-L1
SCS can be provided with either cylinder shaped or paddle-type electrodes.
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Indication
Cylinder shaped type have the substantial advantage of being placed percutaneously, often
under conscious sedation. This allows for intraoperative confirmation of proper position.
Paddle-type are placed surgically. These have a lower risk of migration, but require
laminotomy for placement. Use of paddle-type may be necessary if the epidural space has
been compromised or the patient had prior laminectomy/posterior fusion3,5.
One or two leads are used for the trial period. Two leads are generally used for
permanent placement, which gives increased coverage, and may reduce the need for
manual repositioning.
Technique- Lead Placement
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The epidural space is
accessed via a paramedian
approach, with a curved or
straight introducer needle,
using loss of resistance
technique (16 G Touhy
needle).
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In the image to the right, one
lead has already been placed.
Technique- Lead Placement
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The lead is advanced through
the introducer needle.
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Stylet is used inside the lead
to stiffen the lead and help
with guidance.
Technique- Lead Placement
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The lead is advanced to the appropriate level, depending on the indication.
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The lead should be maintained in the dorsal epidural space.
Technique- Lead Placement (Repositioning)
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In the example to the right, the
lead has coursed anteriorly,
and needs to be repositioned
into the dorsal epidural space.
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The lead should be advanced
under fluoroscopic control to
monitor for incorrect course or
positioning. The leads can be
repositioned during the
procedure.
Technique- Lead Placement
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After leads are positioned,
different stimulation protocols
are tested.
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The leads can be manually
adjusted at this time to
optimize coverage.
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If placement is for trial, the
leads will then be sutured to
the skin and covered with
sterile dressing.
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If placement is for permanent
use, the leads are anchored to
the fascia, and tunneled to the
pocket for the pulse generator.
Technique- Programming
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The leads must be positioned and programmed to induce paresthesia over the
region of pain. It is helpful to have a company representative present to optimize
the stimulation program.
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The pulse width, pulse frequency, and pulse amplitude can be adjusted13.
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Pulse frequency is generally applied in the 10-40 Hz range.
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Pulse width is usually in the 60-450 msec range. With increasing pulse width, the region
of paresthesia will generally extend caudally.
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Pulse amplitude is generally in the 3-10 mA range. The usage range can be determined
during initial programming. The lower end of the usage range is the “perception
threshold,” which is the lowest amplitude to induce paresthesia. The upper end is the
“discomfort threshold,” above which the patient will experience discomfort and/or motor
neuron activation11. The discomfort threshold is usually approximately 1.4 times the
perception threshold13.
Technique- Technical Challenges
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Varying anatomy of the spinal canal along the spinal column presents unique
challenges7.
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Aberrant stimulation should be recognized intraoperatively3.
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Cervical spinal cord is thickest at C3 and C7, with low volume of epidural space. This
increases the risk of neurologic injury.
Thoracic spine kyphosis leads to varying anterior posterior position of the spinal cord, with
resultant variations in available epidural space.
Scoliosis and degenerative disease can further complicate lead placement.
Stimulation must occur within the dorsal column, and induce paresthesia in a caudal
ipsilateral location.
Abdominal or chest wall sensations indicates lead placement in the anterior epidural space.
Activation at unexpectedly low amplitude can indicate either intradural placement or lateral
placement preferentially activating the nerve root.
Monitoring for procedure-related complications during post-operative observation
and follow-up is appropriate3.
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In the immediate post-operative period, severe back pain, incontinence, or weakness raises
alarm for epidural bleed. Headache/neck stiffness points to CSF leak or meningitis.
In the delayed period, neurologic deficit is concerning for epidural abscess, cord
compression, or new pathology. Patient should also be monitored for infection.
Complications
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The complications of SCS were recently described in detail by the NACC4. Most
complications are minor and reversible; outcomes with long term morbidity or
mortality have occurred, but are rare.
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MRI compatibility needs to be determined on a case-by-case basis (use of MRI
with spinal cord stimulators has been addressed by NACC4). In some cases,
myelography may be necessary to evaluate complications.
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Complications of SCS fall into four broad categories4:
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1. Patient-related complications
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Appropriate patient selection should limit unsuccessful procedures due to cognitive or
physical limitations.
Complications- cont’d
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2. Device-related complications
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3. Technique-related complications
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Risk of lead migration or breakage is reduced with newer designs. Modern electrode
designs also have a high likelihood of reestablishing pain control through reprogramming
(rather than manual reposition).
Less common device-related complications include unexpected battery failure or
impaired communication between control device and pulse generator.
NACC has issued guidelines for proper training and technique, which can limit
occurrence of lead migration/breakage, aberrant stimulation, and device-related pain.
4. Biologic complications
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Infection is reported to occur in 3-10% of cases. Most common are superficial skin
infections and infections at the site of pulse generator implantation. Antibiotic prophylaxis
is routine.
Neurologic injury is rare, but the risk necessitates post-operative observation.
Additional complications include (but are not limited to) hematoma, seroma, and CSF
leak.
Summary of our experience
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In retrospective review of 177 cases of spinal cord stimulator procedures, over
seven years, we found:
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Trial procedures accounted for 98 cases, and there were 50 cases of permanent
placement.
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Majority of patients were female, 62%.
Average patient age was 61 ±15 years.
Radiculopathy† and back pain were the most common indications, each accounting for
70 cases.
Over this time period there were 12 revisions and 5 removals.
Five cases were determined to be technically unsuccessful, due primarily to either
inability to advance needle/wire or thecal sac entry (demonstrated by return of CSF).
Leads were placed percutaneously in our fluoroscopy suite, under conscious
sedation.
† Cases
involving both back pain and radicular
pain were counted as radiculopathy indication
Conclusions
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Spinal cord stimulation is an effective, reversible, and safe option for
patients with neuropathic pain who have failed surgical or conservative
medical management.
Proper patient selection improves efficacy and minimizes complications.
Use of a trial period further improves patient selection.
In the majority of cases, leads can be placed percutaneously, under
conscious sedation.
> Leads are positioned under fluoroscopy.
> Percutaneous approach limits surgical risk/morbidity and avoids general
anesthesia.
> Conscious sedation allows optimal intraoperative lead placement.
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Major complications, such as neurologic injury, are rare. The small risk,
however, necessitates monitoring in the immediate and delayed postoperative periods.
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