Neuromodulation; A new Frontier
for Neuroradiologists
Bassem A. Georgy, M.D.,
North County Radiology
Assistant Clinical Professor,
University of California, San Diego
Financial Disclosure
• Consultant; DePuy Spine, Arthrocare Inc.,
Dfine
• Advisory Board; Osseon LLC, Spine
Aligns
• Multiple pending Patents
Overview
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History
Gate Theory
Indications
Implantation techniques
SCS and Neuroradiology
What is Neurostimulation?
• Delivery of electrical impulses to the spinal
cord to block pain signals transmission
• Induce Paresthesia
• Patient feels a tingling sensation in the
usual area of pain
• Any kind of neuropathic pain refractory to
other treatments and not candidate for
further surgical procedures
Types of Pain
• Neuropathic Pain
– Radiculopathy
– Herpetic Neuropathy
– Diabetic Neuropathy
• Nociceptive Pain
– Discogenic pain
– Facet and SI pain
• Mixed Pain
– FBSS
– Cancer pain
What is a Spinal Cord Stimulator?
• Electrical lead implanted in the epidural
space
• Lead is tunneled under the skin
• Lead is connected to a charger that is
implanted in a subcutaneous pocket
• Patient control the charger from outside
Types of SCS Procedures
• SCS trial
– Subcutaneous lead implantation and outside
charger
• Percutaneous implantation
– Subcutaneous lead implantation,
subcutaneous pocket for charger
• Surgical implantation
– Laminectomy for lead implantation
Gate Control
Theory
-Proposed by Melzack &
Wall in 1965
-A non-painful stimulus that
acts likes gates can block
the transmission of a
painful stimulus.
The Gate Control Theory
• There is a gate in the spinal cord that controls the flow of
noxious pain signals to the brain.
• The theory suggests that the body can inhibit these pain
signals or "close the gate" by activating certain nonnoxious nerve fibers in the dorsal horn of the spinal cord.
• The neurostimulation system, implanted in the epidural
space, stimulates these pain-inhibiting nerve fibers,
masking the sensation of pain with a tingling sensation
(paresthesia)
• Stimulate the large diameter A fibers not small C fibers
Mechanism of Action
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GABAergic effects
Dorsal Column Stimulation
Increased blood flow
Neurotransmitters metabolites
concentration in the CSF
Indications
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Failed back surgery Syndrome
RSD
Arachnoiditis
Peripheral Neuropathy
Axial pain
Post herpetic Neuralgia
Peripheral Vascular diseases
Angina
Percutaneous Lead Placement
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Local anesthesia
Insert 14G Touhy needle into
the epidural space
Confirm needle location with
fluoroscopy and loss of
resistance
Introduce guidewire
Insert lead
Confirm lead location with
fluoroscopy
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Dual Lead Placement
• Insert second needle
one level
below/contralateral to
first
• Place lead tips at same
level or staggered
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Intraoperative Screening
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Connect lead and
screener
Test by trying different
electrode combinations
and polarities
Goal of matching
stimulation to pain pattern
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CURRENT
STEERING
Lateral
Steering
Longitudinal
Steering
CASE STUDY
• 45 year-old
male with
bilateral leg
and lower
back pain
• (red indicates
pain pattern)
• Implanted with
dual Octrode
leads and an
Eon
rechargeable
IPG
T-8
• Stim-set 1 uses a
bipole and 5.1
mA current to
cover the right
leg pain
• (light blue
indicates
paresthesia)
+
5.1 mA
• Stim-set 1
remains running
• Stim-set 2 uses a
guarded cathode
and 4.6 mA
current to capture
the left calf
• Current needs to
be steered
cephalad to
capture the left
leg pain
+
4.6 mA +
+
5.1 mA
• Stim-set 1 remains
running
• Stim-set 2 steers
current up one
electrode to
capture the entire
left leg at 6.0 mA
• Patient does not
like stimulation in
the left calf
6.0 mA
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-
+
4.6 mA
+
5.1 mA
• Stim-set 1
remains running
• Stim-set 2 focuses
the 6.0 mA current
by using a
guarded cathode
to pull stimulation
out of the left calf
6.0 mA +
+
+
5.1 mA
• Stim-sets 1 and 2
remain running
• Stim-set 3 covers
the lower back
pain
• Now, the current
levels to each stimset need to be
optimized with
Active Balancing™
7.1 mA
+
6.0 mA +
+
+
5.1 mA
Test Stimulation
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Lead secured to skin
Allows for test stimulation
of several days
Success is defined if
more than 50% pain relief
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Goals of the Trial Evaluation
The goals of the trial evaluation period (several days) are to
• evaluate the effect that SCS therapy has on
– pain
– opioid use
– function and activity levels
• determine the patient’s
– electrical energy requirements
– optimal parameter settings
• The goal is at least a 50% reduction in pain without
intolerable side effects
Permanent Percutaneous
Implantation
1. Successful trial
2. Percutaneous lead
placement
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Lead anchored to
supraspinous ligament
Retest the patient
Extension externalized
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Permanent Percutaneous
Implantation
• Employ local anesthetic for
tunneling path
• Create stab wound on
flank
• Tunneling to flank
• Pass extension through
stab wound
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Permanent Percutaneous
Implantation
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Pocket site identified and
created
Extension connected
with lead
Pocket creation for
connector and
excess lead
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Permanent Percutaneous
Implantation
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Neurostimulator/extension
connection
Implant neurostimulator in
pocket
X-rays for system visualization
Incisions closed
Settings optimized with
external programmer
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SCS in the IR: Things You Will Need
Surgical Instruments
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Scalpel
Bovey
Suction
Scissors
Grabbers
Retractors
Suture/Closures
Sutures
• Non absorbable
Tichron (0. 2-0)
Silk
• Absorbable
Dexon (3-0)
Moncril (4-0)
SCS in the IR: Things You Will Need
Programmer
Post Procedural
• Antibiotics
Ancef 1 gm 7-10 days
• Post procedural pain
Resume prior pain meds
• # to call for problems
• Appt. for f/u programming, wound
recheck
Complications
–Infection
–Lead dislodgment
–Loss of functionality
–Lead fracture
–Surgical revision for reduction or loss of pain
relief
–Interference may be caused by MRIs and other
radio frequency devices
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SCS and Interventional Radiology
• Can I do it ?
• Training
– Medtronic, ANS, Advanced Bionics
• Reimbursement
• Privileges
• SCS clinical Service
Peripheral SCS
SCS Service
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Consultation
Trial
Remove lead
Assess trial and check wound
Permanent placement
Check would
Follow up
Office, nurse (PA) , support staff