Transcript Radiofrequncy Ablation in Chronic Pain Management Joel Chang MD

Radiofrequncy Ablation in
Chronic Pain
Management
Joel Chang MD
CASE
 67
y/o M
 Lumbago, facet arthropathy, lumbar
spondylolithesis, post-laminectomy
 Attempted Tx: TENS, PT/ aqua,
lidoderm, oxycontin, epidural
 2 Lumbar MBBs of L3-S1 with about
1 hour relief each time
 Presented for pulsed radiofrequency
ablation of L3-S1 of right MBs
Overview
RFA is indicated for pain with constant and
limited distribution
 Interrupts nociceptive pathways in the
treatment of chronic pain
 Useful for nociceptive pain and some
neuropathic pain
 Diagnosis confirmed with diagnostic blocks
first
 Tendency for recurrence 1-2 years but can
be repeated
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Non-indications
 Centralized
pain
 Pathology in the spinal cord
 Serious Psychopathology
Diagnosis
 Diagnostic
blocks are usually done
before RFA
 Done only if blocks are expected to
provide information (ex: herniated
disc)
 Diagnostic block utility include
trigeminal neuralgia, and lumbar and
cervical facet joint pain
Diagnostic Injections
Studies showed that single diagnostic
lumbar z joint blocks are false positive
38% of the time. Blocks are usually
repeated as a result
 The International Association for the
Study of Pain specifies that diagnosis
requires radiographically guided blocks
provide complete relief and are validated
by a appropriate control test that exclude
false-positive responses

RFA Sites
 Medial
Branch of Posterior Ramus:
innervates the facet joints
 Dorsal Root Ganglion (herniated
discs or regional pain syndromes)
 Intradiscal RF
 Sympathetic chain
 Splanchnic nerve
 Gasserian ganglion for trigeminal
neuralgia
RF Machine
Includes temperature display, impedance
monitor, stimulator, and lesion generator.
 Impedance Monitor: Useful for detecting
entry into various mediums ( a large
increase for example might suggest
movement from fluid to tissue)
 Electrical Stimulation: Sensory stimulation
confirms proximity to the target. Motor
stimulation confirms a safe distance to
motor fibers in case a heat lesion is made
 Lesioning Module: continuous vs pulsed RF
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RF Machine (cont)
When the electrode is placed on the
patient’s body, a circuit is complete
 An electric field is established around the
electrode tip. This field oscillates with
alternating RF current causing movement
of ions in the tissue
 This causes friction in tissue surrounding
the catheter tip which produces heat (not
the catheter itself)
 Monitoring the catheter tip temp therefore
adequately measures tissue temp.
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RF Machine (cont)
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RF current is low energy, high frequency
(100,000-500,000 hz)
RF lesions do not selectively destroy only
nociceptive afferents
Temperature determines the size of the lesion
Cells become damaged at temps 42 to 45
degrees celsius. With temps of 60-100 degrees
celsius there is near instantaneous induction of
protein coagulation, leading to cell death
Electrical stimulation at 50 hz should produce
sensory stimulation at less than 1 V if electrode is
placed correctly.
Stimulation at 2 hz should evoke contraction of
ipsilateral paraspinal muscles below 2.5 V but
without limb contracture.
RF tidbits
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RFA near bone or scar tissue may have a very
irregular ablation pattern from differences in
impedance and conductivity leading to
complications. Pulsed RFA is more ideal in these
situations and less likely to lead to complications
Patients with pacemakers: cardiology
consultation is needed to convert the pacemaker
to a fixed rate for the procedure
Patients with spinal cord stimulators:
adjustments are also needed with the settings
(monopolar needs to be changed to bipolar and
off)
Technique
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RF electrodes produce little lesion distal to their
tip and coagulate transversely
Therefore if electrodes are placed perpendicularly
to the nerve the may fail to coagulate the nerve
or will coagulate the nerve minimally
The most reliable coagulation is done if the
electrodes are placed parallel to the nerve.
Of note that some of the early studies were
believed to be done under poor technique,
producing poor outcomes
Needless to say, outcome results depend on user
experience with RFA
Technique (cont)
The use of preliminary electrical
stimulation of the medial branch nerve to
verify electrode placement is debatable.
 Some argue its an unnecessary use of
time and that adjusting the electrode
position to minimize the threshold for
evoked activity does not improve outcome
 Radiological confirmation of electrode
placement is essential
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Pulsed-RFA
RFA: 80 degrees C for 90 seconds
 Pulsed-RFA: 42 degrees for 120 seconds
 Current is applied in bursts of 20 ms with
a silent time of 480ms
 Lower temp in pulsed-RFA results in less
tissue destruction
 Unclear Mechanism of pulsed RFA:
- modulates pain processing mechanisms
-selectively disrupts small nerve fibers
- Pulsed RFA associated with increased
cFos
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Pulsed- RFA
Studies show that PRF for lumbar
facet joints tend do have a shorter
benefit of pain relief (4 months
compared to 12 months for RF)
 Standard RF also denervates the
multifidus muscle which eliminates
the muscular component of lumbar
facet syndrome
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Results
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Success for Lumbar RFA ranges from 60-90%
21% had complete pain relief and 65% reported
mild to mod pain relief
Other studies showed that 60 percent of patients
enjoy at least 80% relief at 12 months and 80
percent enjoy at least 60 percent relief.
92% achieved good relief for Trigeminal Neuralgia
Reports show that there is some loss of effect
over 1-2 years
Can be repeated
Cervical RFA
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Symptoms that indicate a patient might benefit from
cervical RFA include: neck pain, headache, shoulder pain,
scapula and upper arm pain
Cervical MBB have a false positive rate of 1 in 3 (lower than
Lumbar but still requires diagnostic blocks)
A high failure rate noted for C2-C3 Z joints 2/2 nerves
larger size and more variable course. This facet is
innervated by the medial branch of the C3 dorsal ramus
with a inconsistent contribution from the greater occipital
nerve.
Cervical anatomical variability necessitates multiple RF
lesions per target nerve
When pain reoccurs procedures can be repeated
Side effects are well tolerated and serious complications
have not been reported
Other Applications
 RFA
MB of thoracic Z joint pain, but
evidence not as reassuring
 Also evidence for sacroiliac joint also
not strong
Repeat RFAs
Study of effectiveness of repeat
radiofrequency neurotomy for lumber
facet pain (Schofferman, Kine, Spine Vol 29)
showed that the frequency of success and
durations of relief remained consistent
after each subsequent radiofrequency
ablation.
 Mean duration of 10.5 months and
successful more than 85% of the time
 This 10.5 months however, is shorter than
reported 1st time RFA relief
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To Keep In Mind
 RFA
significantly improves the pain
and quality of life in patients
 However, it does not cure the (facet)
pain.
References
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Lord, S, Bogduk, N. Radiofrequency procedures in
chronic pain. Best Practice and Research Clinical
Anesthesiology Vol. 16, No. 4, 597- 617.
Mikeladze, Espinal, et al. Pulsed Radiofrequency
application in treatment of chronic zygapopyseal
joint pain. The Spine Journal 3 (2003) 360-362.
Niemisto, Kalso, et al. RF Denervation for Neck
and Back Pain: A Systemic Review Within the
Framework of the Cochrane Collaboration Back
Review Group. Spine Vol 28, Number 16, pp
1877-1888.
Sluijter, M., Racz, G. Technical Aspects of
Radiofrequency. Pain Practice, Vol 2, Number 3,
195- 200.