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Radiofrequncy Ablation in Chronic Pain Management
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Radiofrequncy Ablation in Chronic Pain Management Joel Chang MD CASE 67 y/o M Lumbago, facet arthropathy, lumbar spondylolithesis, post-laminectomy Attempted Tx: TENS ... – PowerPoint PPT presentation
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Title: Radiofrequncy Ablation in Chronic Pain Management
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Radiofrequncy Ablation in Chronic Pain Management
- Joel Chang MD
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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
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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
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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
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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
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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
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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 patients
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)
- 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.
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RF tidbits
- 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)
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Technique
- 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
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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
- 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
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Cervical RFA
- 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
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Other Applications
- RFA MB of thoracic Z joint pain, but evidence not
as reassuring - Also evidence for sacroiliac joint also not strong
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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.
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References
- 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.
