Chapter 8. Pain Management Techniques Flashcards Preview

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Flashcards in Chapter 8. Pain Management Techniques Deck (111):

626. Which of the following is the most common
microbe that grows in cultures of infected
intrathecal pump wounds?
(A) Pseudomonas species
(B) Escherichia coli
(C) Staphylococcus aureus
(D) Staphylococcus epidermidis
(E) None of the above

626. (D)
A. Pseudomonas species grew in 3% of infected
wound cultures.
B. Escherichia coli is probably among the
unknown or not reported 20% or the multiple
or other species (7%).
C. and D. Staphylococcus species grew in cultures
of infected sites 59% of the time. Most
reports did not specify whether the cultured
Staphylococcus organisms were S aureus
or S epidermidis. However one study specifically
emphasized S epidermidis, which
arises from the skin of the patient or operating
room personnel, as the most likely
culprit. No growth took place in 9% of the
infected-wound cultures. No positive fungal
cultures were reported.


627. You think a patient has developed an intrathecal
catheter-tip inflammatory mass. What signs
and symptoms would support this finding?
(A) Diminishing analgesic effects
(B) Pain that mimics nerve root
(C) Pain that mimics cholecystitis
(D) A and B
(E) A, B, and C

627. (E)
A. Subtle prodromal signs and symptoms
during early growth of a catheter-tip mass
include decreasing analgesic effects (loss
of previously satisfactory pain relief) and
unusual increase in the patient’s underlying
pain. Another occurrence was that
patient required unusually frequent or
high dose escalations to obtain analgesia.
In certain instances, dose increases and
large drug boluses reduced the patient’s
pain only temporarily or to a lesser degree
than previous experiences predicted.
B. Catheter-tip masses in the lumbar region
sometimes simulated nerve root compression
from a herniated intervertebral disc
or spinal stenosis.
C. When the catheter tip is located in the thoracic
region, early signs and symptoms of
an extra-axial inflammatory mass sometimes
included thoracic radicular pain that
stimulated intercostal neuralgia or cholecystitis.
Gradual, insidious neurologic deterioration
weeks or months after the appearance
of subjective symptoms was the most
common clinical course before the onset of
myelopathy or cauda equina syndrome.
Myelopathy is a term that means that
there is something wrong with the spinal
cord itself. This is usually a later stage of
cervical spine disease, and is often first
detected as difficulty while walking
because of generalized weakness or problems
with balance and coordination. This
type of process occurs most commonly in
the elderly, who can have many reasons for
troubled walking or problems with gait
and balance. However, one of the more
worrisome reasons that these symptoms
are occurring is that bone spurs and other
degenerative changes in the cervical spine
are squeezing the spinal cord. Myelopathy
affects the entire spinal cord, and is very
different from isolated points of pressure
on the individual nerve roots. Myelopathy
is most commonly caused by spinal stenosis,
which is a progressive narrowing of the
spinal canal. In the later stages of spinal
degeneration, bone spurs, and arthritic
changes make the space available for the
spinal cord within the spinal canal much
smaller. The bone spurs may begin to press
on the spinal cord and the nerve roots, and
that pressure starts to interfere with how the nerves function normally. Myelopathy
can be difficult to detect, because this disease
usually develops gradually and also
occurs at a time in life when people are
beginning to slow down a little bit anyway.
Many people who have myelopathy will
begin to have difficulty with activities that
require a fair amount of coordination, like
walking up and down the stairs or fastening
the buttons on clothing. If a patient has
had a long history of neck pain, changes in
coordination, recent weakness, and difficulty
doing tasks that used to be easier
because your body seemed more responsive
in the past, are definite warning signs
that they should see a doctor. Surgery is
usually offered as an early option for people
with myelopathy who have evidence of
muscle weakness that is being caused by
nerve root or spinal cord compression. This
is because muscle weakness is a definite
sign that the spinal cord and nerves are
being injured (more seriously than when
pain is the only symptom) and relieving
the pressure on the nerves is more of an
urgent priority. However, the benefits of
nerve and spinal cord decompression have
to be weighed against the risks of surgery.
Many people who have myelopathy
caused by degenerative cervical disorders
are older and often a bit frail. Spine surgery
can be a difficult stress for someone who is
old or who has many different medical
problems. However, a surgeon will be able
to discuss the risks and benefits of surgery,
and what the likely results are of operative
versus nonoperative treatment.
Cauda equina syndrome is a serious
neurologic condition in which there is
acute loss of function of the neurologic
elements (nerve roots) of the spinal canal
below the termination (conus) of the
spinal cord. After the conus the canal contains
a mass of nerves (the cauda equina—
horse tail—branches off the lower end of
the spinal cord and contains the nerve
roots from L1-5 and S1-5. The nerve roots
from L4-S4 join in the sacral plexus which
affects the sciatic nerve which travels caudally
(toward the feet). Any lesion which
compresses or disturbs the function of the
cauda equina may disable the nerves
although the most common is a central
disc prolapse. Other causes include protrusion
of the vertebra into the canal if
weakened by infection or tumor and an
epidural abscess or hematoma. Signs
include weakness of the muscles innervated
by the compressed roots (often
paraplegia), sphincter weaknesses causing
urinary retention and postvoid residual
incontinence. Also, there may be
decreased rectal tone; sexual dysfunction;
saddle anesthesia; bilateral leg pain and
weakness; and absence of bilateral ankle
reflexes. Pain may, however, be completely
absent; the patient may complain
only of lack of bladder control and of saddle-
anesthesia, and may walk into the
consulting-room. Diagnosis is usually
confirmed by an MRI scan or a CT scan,
depending on availability. If cauda equina
syndrome exists, early surgery is an
option depending on the etiology discovered
and the patient’s candidacy for major
spine surgery.
Awareness of these two phenomena and
maintenance of an index of suspicion are
important factors to help physicians detect
such inflammatory masses early in the clinical
An inflammatory mass or granuloma is
resulted from a buildup of inflammatory
material at the tip of the catheter. Signs and
symptoms that warrant prompt diagnosis
to rule out the presence of a catheter-tip
mass include changes in the patient’s neurologic
condition, including motor weakness,
such as gait difficulties; sensory loss,
including proprioceptive loss; hyper- or
hypoactive lower extremity reflexes; and
any evidence of bowel or bladder sphincter
dysfunction. The practitioner should also
be suspicious of new or different reports of
numbness, tingling, burning, hyperesthesia,
hyperalgesia, or the occurrence of pain
(especially radicular pain that corresponds
to the level of the catheter tip) during
catheter access port injections or programmed
pump boluses. The latter finding should alert the physician to discontinue
the procedure and perform a diagnostic
imaging study as soon as possible.
If signs and symptoms suggestive of a
catheter-tip mass are detected, the practitioner
should first review the patient’s
current issues, history, and neurologic
examination. Then, a nonsurgical pain practitioner
should review imaging studies with
a neurosurgeon. Third, the physician should
arrange the performance of a definitive
diagnostic imaging procedure to confirm or
rule out the suspected diagnosis. Treatment
should be started in a timely fashion.
Laboratory tests and electromyography or
nerve conduction studies are not apparently
useful in this situation.


628. Advantages of intrathecal drug-delivery are
(A) the first-pass effect can be avoided
(B) intrathecal morphine is 300 times as
effective as oral morphine for equipotent
pain treatment
(C) the number of central nervous system
(CNS) derived side effects can be
(D) B and C
(E) A, B, and C

628. (E)
A. The premise behind intrathecal drug
delivery is that by directly depositing
drugs into the CSF, the first-pass effect is
B. Intrathecal morphine is 300 times as effective
as oral morphine for equipotent pain
treatment. From spinal to epidural morphine
the conversion is in the ratio of 1:10.
From epidural to IV morphine the conversion
is in the ratio of 1:10. From IV to oral
morphine the conversion is in the ratio of
1:3, hence 10 × 10 × 3 = 300.
C. By the direct action of the medication, the
number of CNS-derived side effects can be


629. Which one of the following is not an item to contemplate
prior to placing an intrathecal pump?
(A) Does the patient have an acceptable
physiologic explanation for the pain
(B) Does the patient have a life expectancy
of 3 months or longer
(C) Psychologic clearance is not needed in
the patient with cancer pain
(D) How old is the patient
(E) Has the patient been reasonably
compliant with past treatment

629. (D) In choosing the right patient for an intrathecal
drug-delivery system, several important
questions must be asked, like
A. Does the patient have an adequate physiologic
explanation for the pain syndrome?
Does the diagnosis require aggressive pain
B. Does the patient have a life expectancy of
3 months or longer (required for both cancer
and noncancer patients)?
C. Is the patient psychologically stable? A
psychologist should assess the patient’s
mental status and stability prior to the
procedure. Outcomes have been shown to
deteriorate with the presence of untreated
depression, untreated anxiety disorders,
and suicidal or homicidal ideation. Results
have also been negatively influenced by
the presence of untreated illicit substance
dependence. The presence of a personality
disorder such as borderline, antisocial, or
multiple personality disorder should
cause extreme caution, with these patient
receiving implants only in extenuating circumstances.
Psychologic clearance is not
needed in the patient with cancer pain, but
many of these patients may benefit from
counseling to better cope with the disease
E. Has the patient been reasonably compliant
with past treatments? Has the patient failed
other, less invasive therapies? What were
they? Were they documented? Do they
include physical therapy and oral medications?
Are more conservative therapies unacceptable,
not desired, or contraindicated? Do
the symptoms of pain affect the patient’s
ability to function? Does the patient have a
contraindication, such as a bleeding diathesis,
or a localized or systemic infection? Has
the patient had a successful intrathecal medication
trial? The physician should write a
detailed note regarding symptom relief, side
effects, and overall patient acceptance. Does
the patient have a realistic view of expectations?
Does the patient accept the risks of the
procedure/device and future medications?


630. Prior to implanting an intrathecal pump many
practitioners perform an intrathecal medication
trial. Significant parameters to consider
(A) delivery site
(B) type of medication
(C) whether the patient should be admitted
(D) A and B
(E) A, B, and C

630. (D)
A. and B. There is a definite justification for a
trial that mimics the conditions that will be
achieved by the implanted system. Important
parameters include
• Site of medication delivery (intrathecal
versus epidural, and spinal level)
• Whether the medication is delivered as a
bolus or an infusion
• Infusion rate
• Dose/concentration range
• Length of trial
• Medication selected for trial
C. The patient should always be admitted
and observed after an intrathecal medication
trial. There was a comparison of trial
methods in pain patients (nociceptive,
neuropathic, or mixed) selected to have
intrathecal pump placement. In the final
analysis at 12 months after implantation, it
was determined that there was no significant
difference in trial method (single-shot
intrathecal, continuous intrathecal, or continuous
epidural) in outcomes with nociceptive
pain. However, in neuropathic
pain syndromes, the initial success of trial
was significantly better if a continuous
method was used. There was no difference
noted in trial through the epidural route
versus trial through the intrathecal route.
The main difference between successful
trials in patients with neuropathic pain
and mixed pain syndromes was the inclusion
of more than one medication to
improve the success of the trial.
Morphine has been approved by the
FDA for intrathecal drug-delivery systems,
and is often the first choice of drug
for trial. Local anesthetics or α-receptor–
acting drugs are sometimes added to the
trial in patients with burning or lancinating
extremity pain with hopes of improving
the success of the trial.
To be considered a success, the trial
should induce significant pain relief, with
minimal side effects, and noncancer patients
should obtain purposeful improvement of


631. When dealing with an infection, which of the
following would favor explanting the intrathecal
(A) Associated bleeding
(B) The presence of a seroma
(C) The presence of a hygroma
(D) The presence of necrotic tissue around
the wound
(E) All of the above

631. (D)
A. Bleeding at the wound site will be obvious
with seepage into the dressing. Associated
signs include edema, discoloration, and
rubor. It can usually be treated with ice and
compression; however, surgical exploration
may be necessary. The presence of an active
bleed does not necessitate the explantation
of the intrathecal drug-delivery system.
B. A seroma is a collection of noninfectious
fluid. It is usually treated with pressure
dressings and conservatively allowing for
resorption. If conservative treatment is not
efficacious, sterile aspiration may be necessary.
Its presence does not require the
removal of the intrathecal pump.
C. A hygroma is a collection of CSF. Its most
common cause is leakage of fluid around
the catheter entry point and into the
pocket. It can be treated with abdominal
pressure, caffeine, and increased fluid
D. Infection of the wound may be minor and
superficial, or it may be severe enough to
warrant the removal of the pump. An
infection may present with fever, redness,
frank pus, or purulent wound drainage.
Incision and drainage, qualification of
pathogenic culprit, and antibiotic therapy
must be undertaken immediately. The
decision to excise the pump is made based
on the presence of necrotic tissue, the overall
condition of the wound, and the condition
of the patient.
The two most disastrous complications
are epidural hematoma and neuraxial
infection. An epidural hematoma may
result in paralysis and should be suspected
with any change in neurologic status
postoperatively. This is an emergency
and an immediate MRI and neurosurgical
consultation should be obtained. The presence
of an intrathecal pump is not a contraindication
to MRI, and should not delay
its use. A neuraxial infection can include
meningitis or an epidural abscess and they
must both be diagnosed immediately so
that treatment can be started expeditiously.


632. You have separately tried maximum doses of
morphine and hydromorphone, in a patient’s
intrathecal pump without any efficacy. According
to the 2007 Polyanalgesic Consensus Guidelines,
which one of the following would not be an
accepted “next” step?
(A) Switch to morphine plus bupivacaine
(B) Switch to ziconotide
(C) Switch to clonidine
(D) Switch to fentanyl
(E) Switch to hydromorphone plus

632. (C) For the 2007 Polyanalgesic Consensus
Guidelines, baclofen and midazolam were
moved to special consideration categories.
Midazolam may be used in end of life situations
but only minimal/anecdotal evidence
exists. Baclofen is to be used in patients that
have spasticity-related pain, diseases associated
with dystonia, or unrelenting spasms in
muscle. It works via blockade of GABAB receptors
in the spinal cord. Indications for intrathecal
baclofen therapy: patient is intolerant of
oral agents, pain is inadequately treated with
oral agents, need exact control of dosing that only intrathecal delivery allows. Efficacy in
neuropathic pain has been noted through case
reports at doses of 100 to 460 μg/d (maximum
FDA dosing is 900 μg/d). If significant dose
increases are taking place, consider mechanical
problems. Very good for exceptional long-term
tolerability is expected. However, baclofen is
not without complications. Withdrawal can
occur secondary to catheter disruption, battery
failure, or human error. There is a very wide
spectrum of presentation ranging from asymptomatic
to death. Granulomas are very rare.
Overdose is usually results from human error
and can be reversed with physostigmine, and


633. Ziconotide was approved for infusion into the
cerebrospinal fluid (CSF) using an intrathecal
drug-delivery system by the Food and Drug
Administration (FDA) in 2004. Its proposed
mechanism of action is
(A) it blocks sodium channels
(B) it blocks α2δ voltage-gated calcium
(C) it blocks N-type calcium channels
(D) it blocks γ-aminobutyric acid (GABAB)
receptors in the spinal cord
(E) none of the above

633. (C)
A. Numerous medications work by blocking
sodium channels. Ziconotide is not one of
B. Pregabalin and gabapentin work by acting
on α2δ voltage-gated calcium channels. Their
exact mechanism of action is unknown, but
their therapeutic action on neuropathic pain
is thought to involve voltage-gated N-type
calcium ion channels. They are thought to
bind to the α2δ subunit of the voltagedependent
calcium channel in the CNS.
C. Ziconotide is a nonopioid, non-NSAID
(nonsteroidal anti-inflammatory drug),
nonlocal anesthetic used for the amelioration
of chronic pain. Derived from the cone
snail Conus magus, it is the synthetic form
of the cone snail peptide ω-conotoxin MVII-
A. Previously known as SNX-111, it is a
neuronal-specific calcium-channel blocker
that acts by blocking N-type, voltage-sensitive
calcium channels.
Scientists have been intrigued by the
effects of the thousands of chemicals in
marine snail toxins since the initial investigations
in the late 1960s by Baldomero
Olivera, who remembered the deadly
effects from his childhood in the
Philippines. Ziconotide was discovered in
the early 1980s by Michael McIntosh, at
the time barely out of high school and
working with Olivera. It was developed
into an artificially manufactured drug by
Elan Corporation. It was approved for
sale under the name Prialt by the FDA in
the United States on December 28, 2004,
and by the European Commission on
February 22, 2005.
The mechanism of ziconotide has not
yet been discovered in humans. Results in
animal studies suggest that ziconotide
blocks the N-type calcium channels on the
primary nociceptive nerves in the spinal
As a result of the profound side effects
or lack of efficacy when delivered through
more common routes, such as orally or
intravenously, ziconotide must be administered
intrathecally (directly into the
spine). As this is by far the most expensive
and invasive method of drug delivery and
involves additional risks of its own,
ziconotide therapy is generally considered
appropriate (as evidenced by the range of
use approved by the FDA in United States)
only for management of severe chronic
pain in patients for whom intrathecal (IT)
therapy is warranted and who are intolerant
of or refractory to other treatment,
such as systemic analgesics, adjunctive
therapies or IT morphine.
The most common side effects are dizziness,
nausea, confusion, and headache.
Others may include weakness, hypertonia,
ataxia, abnormal vision, anorexia, somnolence,
unsteadiness on feet, and memory
problems. The most severe, but rare side
effects are hallucinations, suicidal ideation,
new or worsening depression, seizures, and
meningitis. Therefore, it is contraindicated
in people with a history of psychosis, schizophrenia,
clinical depression, and bipolar
D. Baclofen’s proposed mechanism of action
is by blocking the GABAB receptors in the
spinal cord.


634. Neurology consults you on a 65-year-old female
with breast cancer that has diffusely metastasized
to her bones. She has had an intrathecal
pump for 4 months, and has just been diagnosed
with meningitis. Which of the following
is true?
(A) The pump must be removed
(B) Enteral antibiotics must be initiated
(C) If the infection is sensitive to vancomycin,
and the patient refuses pump
removal, intrathecal vancomycin may be
(D) Intravenous (IV) vancomycin plus
epidural vancomycin has not been
found to be effective in resolving infection
(E) All of the above

634. (C)
A. The diagnosis of aseptic or viral meningitis
in the cancer patient with an intrathecal
pump should not be an automatic reason
for explantation of the device. Supportive care and neurologic monitoring should be
provided until the symptoms resolve, but
the pump and catheter do not need to be
removed. If the meningitis is of a bacterial
etiology, risk assessment, pain stratification,
and life expectancy should be considered.
Removal of the pump is suggested,
but is not required because there is a
potential for severe, uncontrolled pain.
B. Parenteral (IV) not enteral (via the GI tract)
antibiotics should be started immediately
if bacterial meningitis is suspected. More
specific antibiotics should be administered
after cerebrospinal bacterial cultures and
sensitivities are obtained.
C. If the infection is vancomycin sensitive,
and the patient refuses pump explantation,
intrathecal vancomycin may be administered
at 10 mg/d. Intrathecal vancomycin
has been used successfully for 6 months in
such patients.
D. The same group found that IV vancomycin
combined with epidural vancomycin
(150 mg/d for 3 weeks) abolished infection.


635. A 72-year-old male with end-stage metastatic
prostate cancer has a life expectancy of 6 months.
Which of the following is true with regards to
managing his intrathecal drug-delivery system?
(A) Treatment decisions should be made
based on the 2007 Polyanalgesic
Consensus Guidelines for management
of chronic, severe pain
(B) Fentanyl is considered a first-line
(C) Droperidol may be used, intrathecally,
as a first-line medication for nausea
(D) A different algorithm is applied when a
patient’s life expectancy is less than
18 months
(E) None of the above

635. (C)
B. and C. Morphine or hydromorphone should
be used for nociceptive pain. Bupivacaine
should be used for neuropathic pain.
Morphine or hydromorphone plus bupivacaine
should be used for mixed pain.
Droperidol is 95% efficacious in the treatment
of nausea and vomiting secondary to opioid
intolerance, abdominal tumors, and/or
chemotherapy/radiation therapy, and can be
added at this point (dose: 25-250 μg/d).
Morphine, hydromorphone, or fentanyl/
sufentanil with bupivacaine and
clonidine for nociceptive or mixed pain.
Morphine, hydromorphone, or fentanyl/
sufentanil with bupivacaine for neuropathic
Morphine, hydromorphone, or fentanyl/
sufentanil with more than two adjuvants:
the physician should use opiate
plus local anesthetic plus clonidine and
• Baclofen for spasticity, myoclonus, or
neuropathic pain
• Bupivacaine for neuropathic pain
• Second opioid (lipophilic/hydrophilic)
as an adjuvant
Morphine, hydromorphone, or fentanyl/
sufentanil with more than three
adjuvants: in addition to second-line adjuvants,
the physician should add
• Ketamine for neuropathic pain secondary
to cord compression
• Midazolam for neuropathic pain
• Droperidol for neuropathic pain
Tetracaine may be used for chemical
paralysis for inoperable cord compression,
tachyphylaxis, or emergency hyperalgesia
Some cases may necessitate six adjuvants
to control pain at the end of life with
minimal side effects.


636. Granulomas have been found to occur with all
medications used intrathecally, EXCEPT
(A) clonidine
(B) sufentanil
(C) baclofen
(D) fentanyl
(E) B and D

636. (B) The 2007 Polyanalgesic Consensus
Guideline panelists have addressed this topic
fully. All panelists felt that catheter-related
granulomas still remains one of the most grave
adverse effects and risks of intrathecal pain
management and impediments to the widespread
use of the therapy. Several factors contribute
to the development of granuloma,
including the agent used, catheter position
(majority of granulomas occur in thoracic
area—where CSF volume and flow are
reduced), CSF volume (especially if low), and
the dose and concentration of the drug (low
CSF volume means higher concentrations of
drug). With morphine, the preponderance of
cases have been described in patients receiving
concentrations of 40 mg/mL or greater. In cases
where hydromorphone was implicated, the
majority of cases received concentrations of
10 mg/mL or greater. Even though some panelists
felt that positioning the catheter into the
larger CSF volume of the dorsal intrathecal
space of the low thoracic cord, granulomas do
occur even in cases where catheters have been
inserted into that space. However, concentration
of the agent used appears to be the major
causal factor of intrathecal, catheter-related
granulomas. A., B., C., and D. Inflammatory masses
have been reported to be associated with all
medications administered in the intraspinal
space except for sufentanil and rarely for fentanyl.
As of this writing, there have been at
least three reports published in the literature
of baclofen-related granulomas. Even though
the literature suggests a granuloma protective
effect of clonidine, there have been reports of
patients with intrathecal clonidine, alone, or
in combination with other intrathecal agents
developing granulomas.


Match the associated side effects with the intrathecal
medication that causes it. Each choice can be used
once, more than once, or not at all, and each question
can have more than one answer.
637. Urinary retention
638. Extrapyramidal side effects
639. Hypotension
640. Auditory disturbances
641. Sedation
642. Nausea
643. Worsening of depression
(A) Opioids
(B) Bupivacaine
(C) Baclofen
(D) Clonidine
(E) Droperidol
(F) Ketamine
(G) Midazolam

637 to 643. 637 (A and B); 638 (E); 639 (B and D);
640 (C); 641 (A, D, and G); 642 (A); 643 (D)
Opioids can cause sedation, edema, constipation,
nausea, and urinary retention.
Bupivacaine can cause urinary retention,
weakness, and hypotension.
Baclofen can cause loss of balance, and auditory
Clonidine can cause orthostatic hypotension,
worsening of depression, edema, and sedation.
Droperidol can cause extrapyramidal side
effects such as tremor, slurred speech, akathisia,
dystonia, anxiety, distress, and paranoia.
Ketamine can cause increased anxiety and
irritability, delusional ideation, and facial
Midazolam can cause sedation.
If a medication is not therapeutic for a
patient or is causing significant adverse effects,
it should be properly weaned, and the patient
should be informed of likely withdrawal
symptoms and arrange for outpatient interventions.
Acute baclofen or clonidine termination
can result in hemodynamic derangements,
seizures, or death. To avoid these untoward
effects, physicians should introduce oral
replacement therapy on the stoppage of
intrathecal medications and provide an appropriate
weaning schedule to the patient.


644. A 43-year-old female has 8-month history of
axial low back pain and pain radiating to the
left leg. The magnetic resonance imaging (MRI)
of lumbosacral spine shows severe degenerative
disc disease at L3-4 through L5-S1 with
mild disc protrusions at these levels. She is a
possible candidate for
(A) transforaminal epidural steroid injection
(B) facet joint medial branch diagnostic
(C) spinal cord stimulator (SCS) trial
(D) all of the above
(E) none of the above

644. (D)
A. The epidural steroid injections (ESI) and
SCS are treatment choices for radicular
pain caused in particular by disc herniation causing mechanical and chemical irritation
of the nerve root.
B. Presence of axial low back pain even in
absence of MRI changes can indicate possible
facet arthropathy. Facet and medial
branch diagnostic blocks are likely the
most sensitive and specific diagnostic test
for facet pain. Facet radiofrequency (RF)
denervation seems to be the best treatment
choice for patients with short-term relief
with facet blocks.
C. The SCS trial may be an excellent choice
for radiating pain down the leg.


645. The causes of axial low back pain are
(A) sacroiliac (SI) arthropathy
(B) internal disc disruption
(C) quadratus lumborum and psoas
(D) all of the above
(E) none of the above

645. (D)
A. SI joint injection with local anesthetics and
steroids may have good diagnostic and
possibly therapeutic value if the pain is
located in the SI joints.
B. Internal disc disruption or discogenic
pain can be diagnosed with provocative
C. Quadratus lumborum and psoas muscle
pain represent a form of myofascial pain
that can be a cause of low back pain.
Diagnostic blocks may have a value in diagnosis
of this type of myofascial pain.


646. The false-positive rate of diagnostic lumbar
facet medial branch blocks are
(A) 8% to 14%
(B) 15% to 22%
(C) 3% to 5%
(D) 25% to 41%
(E) 41% to 50%

646. (D) Diagnostic medial branch blocks have a
very high false-positive rate as reported in
studies. This can potentially decrease the success
rate of RF denervation of facet joints since
this procedure is based on good short-term
results with diagnostic medial branch blocks.
For this reason repeated confirmatory diagnostic
block and use of small dose of local anesthetics
(0.3-0.5 mL) is recommended by many.


647. Percentage of cases where the pain relief is
caused by placebo response following interventional
procedures are
(A) 12%
(B) 35%
(C) 20%
(D) 15%
(E) 28%

647. (B) Placebo effect is responsible for pain relief
in up to 35.2% interventional procedures.
Despite the high rates of placebo response it is
not recommended for routine clinical use.


648. The complication of sphenopalatine ganglion
radiofrequency thermocoagulation is
(A) infection
(B) epistaxis
(C) bradycardia
(D) all of the above
(E) none of the above

648. (D)
A. Infection is a rare complication that can be
difficult to treat.
B. It seems that the epistaxis is more common
than thought and can occur if too much pressure is applied to the RF cannula.
Hematoma can occur if maxillary artery of
venous plexus is punctured.
C. Bradycardia is likely caused by reflex similar
to the oculocardiac reflex.


649. The complication of third occipital nerve (TON)
radiofrequency thermocoagulation is
(A) change in taste
(B) ataxia
(C) dysphagia
(D) all of the above
(E) none of the above

649. (B)
A. Change in taste would more likely be associated
with glossopharyngeal nerve, lingual
nerve, and chorda tympani.
B. Ataxia can occur in up to 95% cases of RF
denervation of the TON, numbness in 97%,
dysesthesia in 55%, hypersensitivity in
15%, and itching in 10% of cases. Third
occipital neurotomy almost always partially
denervates semispinalis capitis muscle
and so interferes with tonic neck
reflexes and causes ataxia in particular on
looking downward. The sensation is readily
overcome by relying on visual cues such
as fixing on the horizon.
C. Dysphagia is not associated with TON


650. Positive lumbar provocative discogram for
mechanical disc sensitization includes reproduction
of patient’s pain with injection of the
contrast in nucleus pulposus at what pressure
above the “opening pressure”?

650. (D)
A. Provocative discography is best done while
pressure of contrast has been continuously
measured. Reproduction of pain at 6/10
and pain location and quality should be
similar to the chronic low back pain.


651. The technique of cervical discography includes
needle entry through the skin from the
(A) anterior right side of the neck
(B) posterior right side of the neck
(C) anterior left side of the neck
(D) posterior left side of the neck
(E) median posterior side of the neck

651. (A) Cervical discography is performed with
patient in supine position, using oblique
approach, similar to the stellate ganglion block.
The esophagus is normally positioned slightly toward the left side of the neck. To prevent
puncturing it, the best technique for needle
insertion for cervical discography is anterior
right-sided approach.


652. When performing intralaminar cervical epidural
steroid injections without fluoroscopic guidance,
the chances of having false positive loss
of resistance are close to
(A) 15%
(B) 25%
(C) 35%
(D) 50%
(E) 40%

652. (D) The ligamentum flavum is discontinuous
in cervical levels, therefore allowing for very
high chances of false loss of resistance technique
and therefore mandates the use of fluoroscopy
and contrast administration. The use of
fluoroscopy may improve the safety of this procedure,
medication delivery to the site of
pathology, and potential outcomes. In lumbar
levels it seems that the false loss of resistance in
nonfluoroscopically performed epidural
steroid injections occurs in up to 30% of cases.


653. When performing intralaminar cervical epidural
steroid injections, the unilateral contrast (and
medication) spread is expected in what percentage
of cases?
(A) 50%
(B) 30%
(C) 25%
(D) 10%
(E) 40%

653. (A)
A. Although there is no median septum of fat
in cervical epidural levels the unilateral
medication spread is common. Therefore
injections should be performed toward the
laterality of pathology.
B. False loss of resistance technique when not
performed under fluoroscopy is 30% in
lumbar levels and 50% in cervical levels.
C. Ventral epidural spread in cervical levels is
close to 25%.
D. Too low.
E. Unilateral contrast spread in intralaminar
cervical epidural injections may occur in
roughly 50% of all cases.


654. Which of the following is a complication of
lumbar sympathetic block?
(A) Genitofemoral neuralgia
(B) Retrograde ejaculation
(C) Intravascular injection
(D) All of the above
(E) None of the above

654. (D)
A. Genitofemoral neuralgia is very rare complication
of lumbar sympathetic block but
can occur since the genitofemoral nerve
originates from L1 and L2 nerve root.
B. In retrograde ejaculation, the bladder
sphincter does not contract and the sperm
goes to the bladder instead of penis. This
can lead to infertility.
C. Intravascular injection of large dose of
local anesthetics can lead to seizures.


655. What is the best method for evaluating the adequacy
of lumbar sympathetic block?
(A) Increase in temperature by 2°F
(B) Increase in temperature by 5°F
(C) Increase in temperature by 10°F
(D) Temperature change
(E) Decrease in temperature by 2°F

655. (D) Any temperature change in comparison to
preprocedure temperatures is adequate enough
to assess the adequacy of successful block.


656. Stellate ganglion is located between the
(A) C6-C7
(B) C7-T1
(C) C5-C7
(D) C5-C6
(E) T1-T2

656. (B) The stellate ganglion is formed by fusion of
inferior cervical ganglion resting over the anterior
tubercle of C7 and first thoracic ganglion
resting over the first rib.


657. In relation to the stellate ganglion the subclavian
artery is located
(A) anteriorly
(B) posteriorly
(C) laterally
(D) medially
(E) none of the above

657. (A) In relation to stellate ganglion the subclavian
artery is located anteriorly. For this reason,
care should be taken not to inject


658. Despite satisfactory stellate ganglion block for
sympathetic-mediated pain, the pain relief in
upper extremity is inadequate. The technical explanation for this may lie in inadequate
spread of local anesthetics to
(A) C5 nerve root
(B) inferior cervical ganglion
(C) first thoracic ganglion
(D) T2 and T3 gray communicating rami
(E) C7 nerve root

658. (D)
A. C5 nerve root injection may provide analgesia
by sensory block.
B. Inferior cervical ganglion is part of the stellate
C. First thoracic ganglion is part of the stellate
D. The T2 and T3 gray rami do not pass through
the stellate ganglion but join the brachial
plexus and innervate the upper extremity.
Failure to block these structures may result in
inadequate block (Kuntz nerves).


659. When performing lumbar discography, the
“opening pressure” is the recorded pressure
(A) first appearance of the contrast in
nucleus pulposus
(B) opening of the annular tear to the contrast
(C) reproduction of concordant pain
(D) resting pressure transduced from the
(E) a dural leak

659. (A)
A. The opening pressure is always subtracted
from pressure reproducing pain in final
calculations (eg, positive discography
means: pressure with pain reproduction—
opening pressure


660. Intradiscal electrothermal coagulation (IDET)
outcomes are adversely affected by
(A) appearance of the disc on T2-weighted
MRI images
(B) obesity
(C) age
(D) coexisting radicular pain
(E) gender

660. (B)
A. Discs are usually dark (dehydrated) on T2-
weighted MRI images and this can only
suggest discogenic pain.
B. Morbid obesity can decrease the success
rate and increase the risks of IDET.
C. There are no studies proving that age
influences outcomes of IDET but it seems that advanced age may decrease the rate of
success of IDET treatment.
D. Radicular pain directly does not predict
the outcome of IDET. Discogenic pain
(referred pattern) can sometimes mimic
radicular pain.


661. When performing lumbar discography, in relation
to the laterality of pain, which of the following
should be the needle entry site?
(A) Ipsilateral
(B) Contralateral
(C) Laterality does not make a difference
(D) Guided by MRI images
(E) None of the above

661. (C) It does not seem that the outcomes of
discography are affected by laterality of needle
insertion site.


662. Apatient with painful sacroiliac joint syndrome
had only short-term relief with two sacroiliac
(SI) injections using local anesthetics and
steroids. Which of the following is the next treatment
(A) SI joint fusion
(B) S1, S2, S3, S4 radiofrequency
(C) L5, S1, S2, S3 radiofrequency
(D) L4, L5, S1, S2, S3 radiofrequency
(E) None of the above

662. (D) SI joint fusion has been used in the past as
a treatment of SI pain with unfavorable results.
The L4, L5, S1, S2, and S3 radiofrequency
denervation is shown to be beneficial longterm
treatment option in patients with SI pain.


663. Which of the following includes published
complications that may follow cervical transforaminal
epidural steroid injection?
(A) Epidural abscess
(B) Neuropathic pain
(C) Quadriplegia and death
(D) All of the above
(E) None of the above

663. (D)
A. Epidural abscess should be suspected if
increased pain and new neurologic symptoms
occur after the cervical epidural
steroid injection.
B. Neuropathic pain may occur following
epidural steroid injection.
C. If the steroid solution is injected intravascularly
serious complications including
possible spinal cord infarction may occur.
The digital subtraction fluoroscopy and
blunt needle use may help to minimize its
occurrence if this procedure is performed.


664. In order to minimize the risk for complications
when cervical transforaminal epidural steroid
injection is performed how should the needle be
positioned in relation to the neural foramina?
(A) Anteriorly
(B) Posteriorly
(C) Superiorly
(D) Inferiorly
(E) None of the above

664. (B) Placing needle posteriorly may minimize
the risk of intravascular injection.


665. The single-needle approach to medial branch
block diagnosis in comparison to standard
multiple-needle approach
(A) causes less discomfort for the patient
(B) decreases the volume of local anesthetics
used for the skin and subcutaneous
(C) takes less time to perform
(D) all of the above
(E) none of the above

665. (D)
A. The use of single-needle technique may
decrease procedural discomfort during
medial branch blocks.
B. By minimizing the amount of local anesthetics
for the skin and subcutaneous tissues
the rate of false-positive blocks caused
by treatment of myofascial pain may be
C. This approach may take less time to perform
than the traditional multiple-needle


666. The incidental intrathecal overdose of intrathecal
morphine while performing a pump refill
should be treated by
(A) intrathecal and IV naloxone
(B) airway protection
(C) possible irrigation of the CSF with saline
(D) all of the above
(E) none of the above

666. (D)
A. If IV naloxone is inadequate, intrathecal
naloxone may be considered.
B. Airway protection may be needed because
of respiratory depression.
C. Possible irrigation of CSF with saline may
be necessary.


667. While analyzing a malfunctioning SCS implanted
device, a sign of lead breakage or disconnect is a
measured impedance of
(A) 1500 Ω
(C) 4000 Ω

667. (D) Increased impedance may mean that there
is lead fracture, disconnect, fluid leakage causing
short circuit. The exactly same impedance
at multiple leads may mean that there is a
communication and short circuit between the


668. Accurate placement of a stimulator lead for
occipital nerve peripheral stimulation is
(A) posterior to the C3 spinous process
(B) lateral to the pedicles of C2 and C3
(C) 2 mm lateral to the odontoid process
(D) posterior to the C2 spinous process
(E) none of the above

668. (D) The lead should be positioned subcutaneously
posterior to the C2 spinous process
and perpendicular to the cervical spine.


669. Adequate SCS introducer needle epidural
space at entry level for the desired coverage of
the foot pain is
(A) L3-4 interspace
(B) L1-L2 interspace
(C) T12-L1 interspace
(D) T8-T9 interspace
(E) T10-T11 interspace

669. (A) For the coverage of the foot, the SCS electrode
position should be at the T11-T12 level.
The more caudal entry level is desired in order
to leave enough of the SCS lead in the epidural
space and prevent dislodgement.


670. The placement of SCS electrodes for coverage
of intractable chest pain caused by angina
should be at the epidural level of
(A) T6
(B) C4-C5
(C) T1-T2
(D) C6-C7
(E) C3-C4

670. (C) In order to position the lead at T1-T2 level
commonly the entry site may be at lower thoracic
levels owing to the narrow space in
between the laminae in thoracic spine.


671. Most effective approach for performing lumbar
epidural steroid injections is
(A) caudal
(B) interlaminar
(C) paramedian approach
(D) transforaminal
(E) Taylor approach

671. (D) Although there is insufficient evidence, one
study reported that transforaminal approach
has better outcomes in comparison to interlaminar
approach for epidural steroid injections.
The caudal approach requires diluted
solution and may not reach the area of pathology
in some cases.


672. During interlaminar epidural steroid injections
contrast should be
(A) used in the anteroposterior view
(B) used in the lateral view
(C) used in oblique view
(D) no contrast should be used
(E) A, B, and C

672. (A) Contrast media should be administered in
anteroposterior view in order to rule out
intravascular uptake.


673. Which of the following is the most likely complication
after successful SCS implant?
(A) Infection
(B) Persistent pain at the implant site
(C) Lead breakage or migration
(D) CSF leak requiring surgical intervention
(E) Paralysis or severe neurologic deficit

673. (C)
A. Infection rate of implanted hardware has
been estimated at 3% to 5%.
B. Persistent pain at the implant site has been
estimated at approximately 5%.
C. Lead breakage or migration has been estimated
at 11% to 45%.
D. CSF leak requiring surgical intervention
has been reported.
E. Paralysis or severe neurologic deficit is
possible as with any type of spine surgery,
but is not cited as a frequent occurrence.


674. Which of the following is the most accurate
statement regarding efficacy of SCS?
(A) For failed back surgery patients, SCS in
addition to conventional medical management
can provide better pain relief
and improve health-related quality of
life as compared to conventional medical
management alone
(B) SCS is inefficacious for the indication of
angina pectoris
(C) SCS for CRPS is efficacious for only
about a year only then the efficacy
(D) SCS is not an effective treatment for
sympathetically mediated pain
(E) Nociceptive pain is considered a better
indication for SCS than neuropathic

674. (A)
A. One study which validates this statement
was published in the journal Pain in 2007. A
randomized, crossover study was performed
with intent-to-treat analysis for
more than 12 months. One hundred
patients were randomized to either SCS
and conventional medical management or
conventional medical management only.
More patients in the SCS group achieved
the primary outcome of 50% or more pain
relief in the legs. Other secondary measures
were also improved in the SCS group.
[Kumar K, Taylor RS, Jacques L, et al. Spinal
cord stimulation versus conventional medical
management for neuropathic pain: a
multicenter randomized controlled trial in
patients with failed back surgery syndrome.
Pain. 2007;132(1-2):179-188.]
B. In a 2009 review article it was determined
that SCS decreases use of short-acting
nitrates, improves quality of life, and
increases exercise capacity. [Deer TR.
Spinal cord stimulation for the treatment of
angina and peripheral vascular disease.
Curr Pain Headache Rep. 2009;13(1):18-23.]
C. Many follow-up studies have been published
showing efficacy with short-term follow-
ups such as 6 months. A recent 5 year
follow-up of a randomized, controlled trial
of SCS for CRPS revealed that 95% of
patients would repeat the treatment for the
same result. Aretrospective telephone questionnaire
study was performed in 21 CRPS
patients with average follow-up at 2.7 years.
Reduced pain and improved quality of life
was sustained at long-term follow-up.
[Kemler MA, de Vet HC, Barendse GA, et al.
Effect of spinal cord stimulation for chronic
complex regional pain syndromes type I:
five-year final follow-up of patients in a randomized controlled trial. J Neurosurg.
D. SCS is effective for the treatment of sympathetically
mediated pain.
E. This is a false statement. Neuropathic pain
has traditionally been considered an indication
for SCS. Nociceptive pain is considered
not amenable to treatment with SCS.


675. Which of the following is not a relative contraindication
to SCS?
(A) Unresolved major psychiatric
(B) A predominance of nonorganic signs
(C) Spinal cord injury or lesion
(D) Alternative therapies with a risk to benefit
ratio comparable to that of SCS
remain to be tried
(E) Occupational risk

675. (C) In 2007, an article published an evidencebased
literature review and consensus statement
which addressed over 60 questions
relating to clinical use of SCS. Spinal cord
injury or lesion, is an etiology of neuropathic
pain and is an indication for SCS. Certain occupations
such as an electrician’s are considered
a relative contraindication to SCS therapy.


676. Which of the following statements is most
accurate regarding cost-effectiveness of SCS?
(A) Nobody opines of its cost-effectiveness
and the issue has not been addressed in
(B) The literature is clear and consistent;
SCS is not cost-effective
(C) Although published conclusions may
vary, a consensus of professionals has
determined that SCS stimulation is not
(D) Although published conclusions may
vary, a consensus of professionals has
determined that SCS is cost-effective for
certain indications
(E) All published literature on the topic
concludes that SCS is cost-effective

676. (D) Some published articles concluded that
SCS is cost-effective. Some have concluded that
SCS is not cost-effective, at least in certain
patient populations. Variation may relate to
specific parameters and patient inclusions in
the study. Recent practice parameters concluded
that SCS is cost-effective in the treatment of
failed back surgery syndrome and CRPS and
might be cost-effective in the treatment of other
neuropathic pain indications. Furthermore it
was concluded that cost-effectiveness can be
optimized by adjusting stimulation parameters
to prolong battery life, by minimizing complications,
and by improving equipment
design. [Mekhail NA, Aeschbach A, Stanton-
Hicks M. Cost benefit of neurostimulation for
chronic pain. Clin J Pain 2004;20(6):462-468.
Klomp HM, Steyerberg EW, van Urk H,
et al. Spinal cord stimulation is not cost-effective
for non-surgical management of critical
limb ischemia. Eur J Vasc Endovasc Surg.
2006;31(5): 500-508.
North R, Shipley J, Prager J, et al. Practice
parameters for the use of spinal cord stimulation
in the treatment of chronic neuropathic
pain. Pain Med 2007;8(suppl 4):S200-S275.]


677. Which of the following are specifications for
current SCS systems?
(A) Constant voltage, pulse width up to
2000 milliseconds
(B) Constant current, volume less 10 cm3
(volume less than a standard matchbook)
(C) Constant resistance, pulse width up to
1000 milliseconds, cordless recharging
(D) Constant current, pulse width up to
1000 milliseconds, cordless recharging
(E) Constant current and constant resistance,
cordless recharging, pulse width
up to 1000 milliseconds

677. (D)
A. One of the three commonly used manufacturers
does use a constant voltage technology.
None of the three manufacturers have
a system allowing pulse width much over
1000 milliseconds.
B. Two of the three commonly used manufacturers
do use a constant current technology.
Although battery sizes as small as
22 cm3 are available with two companies,
no company currently has a battery
smaller than that in current clinical usage.
This may change in the near future.
C. No SCS system relies on maintaining constant
resistance. Resistance is not in the
physician’s control and varies with factors
such as scar tissue formation. Cordless
recharging is available with several manufacturers’
D. This is a specification set that is currently
available. Aconstant voltage system is also
now available with pulse widths up to
1000 milliseconds.
E. Maintaining both constant current and
constant resistance would not be achievable
because resistance is not a controllable
factor. Voltage, current, and resistance vary
according to Ohm’s law: voltage = current ×
New batteries have reached the market
including ones with constant voltage,
pulse width of 1000 milliseconds, and battery
size of about 22 cm3.


678. Which of the following is true?
(A) Dorsal column pathways do not play a
role in visceral pain and therefore there
is no role of SCS for visceral pain
(B) Pelvic pain has been demonstrated to
consistently fail treatment with SCS
(C) The midline dorsal column pathway has
been the proposed target for stimulation
for chronic visceral pain
(D) Pelvic pain stimulation can best be
achieved by first targeting the S2 foramen
in a retrograde approach
(E) There is no therapeutic potential for
treatment of chronic visceral pelvic pain
with SCS

678. (C)
A. Dorsal column pathways have been
demonstrated to play a role in transmission
of visceral pain.
B. Case reports have been published showing
successful treatment of pelvic pain with
SCS. One such report was a case series of
six patients with pelvic pain of multiple
diagnoses all treated successfully with
SCS. Diagnoses included vulvar vestibulitis,
endometriosis, pelvic adhesions,
uterovaginal prolapsed, and vulvodynia.
C. Midline myelotomy may relieve visceral cancer
pain. This is a deep pathway and therefore
a tightly spaced lead which can drive the
stimulation deeper would be advantageous
for attempted SCS for visceral pain.
D. The stimulation “sweet spot” for pelvic
pain has been reported to be around T12.
E. Case study evidence supports the role for
SCS for chronic visceral pelvic pain.
Further well-designed studies are needed.


679. Which of the following is the best answer
regarding lead geometry and spacing?
(A) The goal of SCS in treatment of bilateral
lower extremity neuropathy pain is
most frequently to stimulate the dorsal
roots rather than the dorsal columns
(B) Tight lead spacing increases the ratio of
dorsal column to dorsal root stimulation
(C) Too much stimulation of the dorsal
columns results in motor side effects
(D) As the distance from the contact to the
spinal cord increases, stimulation
becomes more specific for the dorsal
columns as opposed to the dorsal
(E) Rostrocaudal contact size (contact
length) is less important than lateral
contact size (contact width)

679. (B)
A. The dorsal columns contain the primary
cutaneous afferents which are the usual
targets. Stimulation of a nerve root will
lead to segmental paresthesia and will not
be likely to encompass the entire area of
the bilateral lower extremity neuropathic
B. This is a correct statement and was supported
by computer-modeled analysis.
C. To the contrary, motor side effects usually
indicates stimulation of dorsal roots rather
than the dorsal column.
D. This statement is incorrect because as the
contact to spinal cord distance increases,
stimulation becomes less specific and
there is an increased chance of dorsal root
E. This is a false statement because fiber
type preference is more sensitive to rostrocaudal
contact size then to lateral contact


680. The gate control theory is one postulated mechanism
of action for SCS. Which of the following
is the most accurate application of SCS to this
postulated mechanism of action?
(A) Activation of large-diameter afferents
thereby “closing the gate”
(B) Activation of large-diameter afferents
thereby “opening the gate”
(C) Activation of small-diameter afferents
thereby “closing the gate”
(D) Activation of small-diameter afferents
thereby “opening the gate”
(E) Activation of both large- and smalldiameter
afferents equally

680. (A) Ronald Melzack and Patrick Wall published
the landmark gate control theory in the
journal Science in 1965. According to this theory
as published in 1965, large and small fibers
project to the substantia gelatinosa. The substantia
gelatinosa exerts an inhibitory effect on
afferent fibers. Large fibers increase the
inhibitory effect, “close the gate,” and decrease
the afferent pain signal. Small fibers decrease
the inhibitory effect, “open the gate,” and
increase the afferent pain signal.
This gate control theory is commonly
cited as the mechanism of action of SCS, but a
2002 review concludes that other mechanisms
must also play a role. [Oakley JC, Prager JP.
Spinal cord stimulation: mechanisms of
action. Spine. 2002;27(22):2574-2583.
Melzack R, Wall PD. Pain Mechanisms: a
new theory. A gate control system modulates
sensory input from the skin before it evokes pain perception and response.


681. Which of the following is most accurate regarding
indications for SCS?
(A) Nociceptive pain is traditionally considered
a better indication than neuropathic
(B) Receptor mediated pain is traditionally
considered a better indication than neurogenic
(C) SCS tends to more effectively treat sympathetically
mediated pain than pain of
the somatic nervous system
(D) Intractable angina is not effectively
treated with SCS
(E) Persisting neuropathic extremity pain
following spinal surgery is a better indication
than pain of CRPS

681. (C)
A. The opposite of the given statement would
be more accurate (ie neuropathic pain is
traditionally considered a better indication
than nociceptive pain).
B. This is a restatement of (A). The term
“receptor mediated” is substituted for and
synonymous with nociceptive. The term
“neurogenic” is substituted for and synonymous
with neuropathic.
C. Multiple authors have described beneficial
results of SCS for sympathetic-mediated
pain [Stanton-Hicks M. Complex regional
pain syndrome: manifestations and the role
of neurostimulation in its management. J
Pain Symptom Manage. 2006;31(suppl 4):
Kumar K, Nath RK, Toth C. Spinal cord
stimulation is effective in the management of
reflex sympathetic dystrophy. Neurosurgery.
Harke H, Gretenkort P, Ladlef HU, et al.
Spinal cord stimulation in sympathetically
maintained complex regional pain syndrome
type I with severe disability. A prospective
clinical study. Eur J Pain. 2005;9(4):363-373.]
D. This is a false statement as some consider
intractable angina to be the pain most
effectively treated with SCS, with up to
90% effectiveness.
E. Both persisting neuropathic pain of the
extremity following spinal surgery and
pain of CRPS are indications for SCS.
However, persisting neuropathic extremity
pain following spinal surgery is not a better
indication. In fact, SCS is considered by
some to be a more effective treatment of
CRPS than persisting neuropathic pain of
the extremity following spinal surgery.


682. Which of the following correctly arranges
intraspinal elements from highest to lowest
(A) CSF, longitudinal white matter, gray
matter, transverse white matter, dura
(B) Longitudinal white matter, gray matter,
CSF, transverse white matter, dura
(C) Longitudinal white matter, transverse
white matter, dura, gray matter, CSF
(D) Gray matter, longitudinal white matter,
transverse white matter, CSF, dura
(E) Dura, transverse white matter, gray
matter, longitudinal white matter, CSF

682. (A) The conductivity of intraspinal elements has
clinical significance. While some tissues have
sufficient conductivity to allow stimulation to
reach afferent fibers and initiate a depolarization,
other tissues provide an insulation-like
effect to protect visceral organs. One would not have to know the actual conductivities of
intraspinal elements to answer this question.


683. Which of the following is the most accurate
explanation why thoracic level cord stimulator
leads do not commonly stimulate intrathoracic
structures such as the heart?
(A) Thoracic placement of SCS leads is contraindicated
and is therefore not a clinically
used technique
(B) The CSF is highly conductive and therefore
diverts the stimulation into a different
(C) The stimulation is very specific for neural
tissues rather than visceral tissues
(D) The dura has a very low conductivity
and therefore insulates visceral structures
from stimulation
(E) The vertebral bone has a very low conductivity
and therefore insulates visceral
structures from stimulation

683. (E)
A. Thoracic placement of SCS leads is very
common. Contacts are often placed at the
T8 level for instance for treatment of lower
extremity pain.
B. While it is true that CSF is highly conductive,
it does not divert the stimulation
away from thoracic structures.
C. While it is true that various fibers have differing
thresholds for recruitment, a negatively
charged electrode (a cathode) will
cause a neuron to become more electrically
charged and depolarized, regardless of the
tissue of origin.
D. It is true that dura has a very low conductivity
similar to vertebral bone. However,
because the dura is so thin, it does not present
significant resistance. This should also
be instinctively false because if the dura
insulated structures from stimulation, then
it would not be possible to stimulate the
neural structures of the spinal cord.
E. This is a true statement. The conductivity
of vertebral bone is very low compared to
other intraspinal tissues.


684. Which of the following best describes the proposed
mechanism of action of SCS?
(A) There is evidence that during SCS large
myelinated afferent fibers are activated
in an antidromic manner
(B) There is a measurable increase in
endogenous opioids in response to SCS
(C) Spinothalamic tract activation during
SCS leads to an analgesic effect
(D) SCS causes an inhibition of ascending
and descending inhibitory pathways
(E) SCS has no effect on abnormal A-β

684. (A)
A. Antidromic responses can be measured at
the sural nerve during SCS. This was
described in a 2002 review of SCS mechanisms
and also demonstrated in 21 measurements
in 16 patients in another study in
2008. [Oakley JC, Prager JP. Spinal cord
stimulation: mechanisms of action. Spine.
Buonocore M, Bonezzi C, Barolet G.
Neurophysiological evidence of antidromic
activation of large myelinated fibers in
lower limbs during spinal cord stimulation.
Spine. 2008;33(4):E90-E93.]
B. SCS efficacy is not reversed by naloxone
and there is no relation of SCS to endogenous
opioid levels.
C. This would be a mechanism of algesic effect.
In fact, one of the proposed mechanisms
of action of SCS is spinothalamic tract
D. This would be a mechanism of algesic effect.
In fact, one of the proposed mechanisms of
action of SCS is activation of ascending and
descending inhibitory pathways. On review
of the mechanisms of action of SCS, one possible
mechanism of action was cited as activation
of supraspinal loops relayed by the
brain stem or thalamocortical systems
resulting in ascending and descending inhibition.
[Oakley JC, Prager JP. Spinal cord
stimulation: mechanisms of action. Spine.
E. According to a 2002 review, the predominant
effect of SCS is on abnormal activity in
A-β neurons related to the perception of
pain. [Oakley JC, Prager JP. Spinal cord
stimulation: mechanisms of action. Spine.


685. Which of the following is true?
(A) Phenol theoretically carries a higher risk
for neuroma formation than alcohol
(B) Radiofrequency ablation is particularly
useful for field neurolysis
(C) Phenol is a particularly useful neurolytic
agent for localized targets
(D) Alcohol is a particularly useful neurolytic
agent because there is no pain
upon injection
(E) Phenol causes wallerian degeneration

685. (A) Because phenol destroys the basal neurolemma,
wallerian degeneration does not
occur and there is a higher risk for neuroma
formation. Lesion size is more difficult to precisely
control with a liquid neurolytic injectate
as compared to radiofrequency ablation in
which the lesion size occurs in a known distance
around the needle tip. On the other hand,
when a field lesion is needed, a liquid neurolytic
may be a more practical approach.


686. Which of the following is most painless upon
(A) Phenol
(B) Alcohol
(C) Radiofrequency
(D) Cryoanalgesia
(E) Cold knife excision of a nerve

686. (A) Phenol is not painful upon injection
whereas the other listed techniques are painful.


687. Which of the following neurolytic techniques is
most concerning for the side effect of
(A) Laser neurolysis
(B) Cryoanalgesia
(C) Radiofrequency
(D) Alcohol
(E) Phenol

687. (E) Phenol is concerning for arrhythmias, seizure,
destruction of Dacron grafts, vasospasm, and
vascular proteins. Alcohol is more concerning
for vasospasm than phenol. Caution when considering
radiofrequency neurolysis includes
interference with electrical implants. Risks of
cryoneurolysis include frostbite to adjacent


688. Which of the following statements is the most
accurate comparison of radiofrequency ablation
and cryoablation?
(A) Cryoanalgesia probes are generally
smaller in diameter than the large-diameter
probes used for radiofrequency
(B) One disadvantage of cryoanalgesia technique
is the operator must support a
heavier instrument while maintaining
the probe tip in accurate position
(C) The cryolesion and the radiofrequency
lesion are similar in size
(D) Cryoanalgesia and radiofrequency
lesion techniques have equal precision
(E) Cryoanalgesia is inferior to radiofrequency
ablation because cryoanalgesia
causes wallerian degeneration

688. (B)
A. Cryoanalgesia probes are generally larger
in diameter than radiofrequency probes.
Current cryoanalgesia probes range in size
from 1.4 to 2 mm. The 1.4-mm cryoprobe is used with a 14- or 16-gauge catheter. A
2-mm cryoprobe is inserted into a 12-
gauge catheter. Radiofrequency procedures
are commonly performed using a
22-gauge needle. A22-gauge needle has an
outside diameter of about 0.7 or 0.72 mm.
B. The cryoanalgesia instrument may be cumbersome
to support while simultaneously
maintaining accurate needle-tip position.
The smaller and lighter probes used with
radiofrequency lesioning machines are less
cumbersome to manage.
C. The ice ball formed at the tip of the cryoprobe
is larger in size than what can be
obtained with radiofrequency lesions.
D. Because of the smaller obtainable lesion
size with the radiofrequency techniques, a
more precise target lesion can be achieved.
E. Both cryoanalgesia and radiofrequency
techniques cause wallerian degeneration
and therefore less risk for neuroma formation
compared to phenol.


689. Which of the following is most accurate regarding
the electric field generated at the tip of a
radiofrequency electrode?
(A) Flat conductors generate larger, stronger
electric fields than round conductors
(B) With round conductors, the charge density
is directly proportional to the radius
of the circle
(C) The electric field around a radiofrequency
cannula is more dense around
the exposed shaft and becomes less
dense at the tip
(D) Voltage, current, and power are the
three basic variables governing formation
of heat surrounding a radiofrequency
cannula tip
(E) The heat lesion formed around the
radiofrequency cannula is slightly pearshaped
with the base of the pear around
the proximal end of the active tip and less
projection of the heat at the needle tip

689. (E)
A. Round conductors generate larger, stronger
electric fields than flat conductors.
B. With round conductors, the charge density
is inversely proportional to the radius of
the circle.
C. The electric field around the exposed shaft
of a radiofrequency cannula is less dense
and becomes more dense at the tip.
D. The three basic variables of electric current
are voltage, current, and resistance. These
are the three factors in Ohm’s law.
E. Although the electric field is less dense
around the shaft but more dense around
the tip of the cannula, the shape of the heat
lesion is different. The heat lesion is
slightly larger around the proximal end of
the active tip and smaller at the needle tip.


690. Which of the following is the most accurate
statement regarding neuraxial neurolysis?
(A) Phenol has significant proven benefit
over alcohol
(B) The technique is 100% efficacious
(C) The average pain relief is less than
6 months
(D) Bladder paresis and motor weakness
occurs in close to 100% of those treated
with neuraxial neurolysis
(E) Epidural neurolysis has a proven favorable
risk to benefit ratio compared to
subarachnoid neurolysis

690. (C)
A. While phenol may be useful for its hyperbaric
property, there is no clear benefit versus
B. Excellent results are reported in 50% to
75% of patients.
C. The average duration of pain relief after
neuraxial neurolysis has been reported at
4 months.
D. Bladder paresis and motor paresis occurs
in approximately 5% of treated patients.
Bowel paresis occurs in approximately 1%
of treated patients.
E. There is no evidence for greater efficacy or
lower risk for epidural neurolysis compared
to subarachnoid neurolysis.


691. While performing an intradiscal radiofrequency
procedure using a posterior-oblique approach,
the needle tip is advanced into the annulus
fibrosus using fluoroscopic guidance. Impedance
is noted. The needle tip is then advanced a little
further. Adrop in impedance is noted. Which of
the following is the most likely explanation?
(A) Malfunction of radiofrequency machine
(B) Needle-tip entry into CSF
(C) Needle-tip entry into spinal cord
(D) Needle-tip has dry blood on it
(E) Needle-tip entry into nucleus pulposus

691. (E) From the described approach, further
advancement of the needle tip should either
remain in annulus fibrosis or enter the next
tissue layer, nucleus pulposus. CSF and spinal
cord are not expected in the described trajectory.


692. Which of the following is appropriate safety
consideration when performing a radiofrequency
ablation procedure?
(A) Motor stimulation is not needed if
meticulous fluoroscopic technique is
(B) A radiofrequency probe should be the
length of the cannula or shorter, but
never longer than the cannula
(C) The pain physician should always turn
off a patient’s sensing pacemaker prior
to a radiofrequency procedure
(D) Complications during radiofrequency
ablation are rare and need not be considered
prior to the procedure
(E) A SCS should be turned off prior to a
radiofrequency procedure

692. (E)
A. Motor stimulation can detect and prevent
unexpected improper heat lesioning. For
example, a break in the insulation of the
needle shaft can allow current to leak into
unexpected tissues.
B. The radiofrequency probe should extend
to the tip of the cannula. Too short of a
radiofrequency probe will result in temperature
measurements that are lower than
the actual tissue temperature. This is especially
concerning as a radiofrequency unit
with automatic temperature control would
increase the output in this situation, leading
to even higher tissue temperatures.
C. It is usually best to consult a cardiologist
prior to radiofrequency procedures when
the patient has a pacemaker. If the pacemaker
is a sensing pacemaker, then changing
the setting to a fixed rate is suggested.
D. It is best to prevent complications rather
than treat complications.
E. The SCS should be turned off prior to
radiofrequency procedures.


693. Coulomb per kilogram (C/kg) is
(A) the unit used to measure electrical
charge produced by x- or γ-radiation
similar to previous roentgen unit
(B) used to measure dose equivalent
(C) the daily radiation exposure per kilogram
of body weight
(D) the intensity of radiation
(E) used to measure the amount of radiation

693. (A) Coulomb per kilogram is used to measure
electrical charge produced by x- or γ-radiation
similar to previous roentgen unit in a standard
volume of air by ionization. Sievert (Sv) is used
to measure dose equivalent


694. Gray (Gy) is used to measure
(A) yearly background exposure
(B) absorbed dose
(C) dose equivalent
(D) daily radiation exposure
(E) yearly radiation exposure

694. (B) Gray (Gy) measures absorbed dose (energy
deposited per unit mass). One gray is equal to
1 J/kg.


695. Maximum total permissible dose equivalents
(in mSv) for a year is
(A) 75 mSv
(B) 100 mSv
(C) 150 mSv
(D) 50 mSv
(E) 25 mSv

695. (D) Individual doses may vary (eg, eye 12.5 mSv).


696. How low should a clinician’s hourly radiation
exposure be?
(A) Less than 0.01 mSv/h
(B) Less than 0.05 mSv/h
(C) Less than 0.15 mSv/h
(D) As low as reasonably achievable
(E) Less than 0.25 mSv/h

696. (D) As low as reasonably achievable is also
known as ALARA (As low as reasonably


697. Most operator exposure during fluoroscopically
guided blocks is when
(A) the lateral views are taken
(B) the x-ray tube is above the patient
(C) the patient is obese
(D) the anteroposterior views are taken
(E) none of the above

697. (B) The x-ray tube above the patient provides
most operator exposure because the scattered
beam is greater at the entrance site of the skin
compared to exit site.


698. The intensity of scattered beam is greater at the
radiation entrance on the skin than exit site
(A) 3 times
(B) 10 times
(C) 30 times
(D) 985 times
(E) 1000 times

698. (D) As the intensity of scattered beam is greater
at the radiation entrance on the skin than exit
site the radiation exposure to the operator is
significantly increased when the x-ray tube is
above the patient.


699. Average patient radiation exposure dose
during pain procedures is
(A) 10 times less than during angiography
(B) same as during angiography
(C) 10 times more than during angiography
(D) less than computed tomographic (CT)
(E) 20 times more than during angiography

699. (C) The patient radiation doses of angiography
are on the other hand 10 times higher than gastrointestinal
fluoroscopy and CT imaging.


700. Radiation dose to the patients and medical personnel
can be reduced by
(A) decreasing the distance between the
image intensifier and the patient
(B) increasing the distance between the
image intensifier and the patient
(C) using continuous fluoroscopy
(D) oblique views
(E) none of the above

700. (A) Oblique views can also increase the radiation
to the patients and operators.


701. Personnel radiation protection can be achieved
(A) lead aprons
(B) glasses
(C) increased distance from the x-ray
(D) all of the above
(E) none of the above

701. (D) Lead aprons contain equivalent of 0.5 mm
of lead and can reduce the radiation exposure
by 90% from scatter.


702. Lead aprons should be always hung:
(A) So that space is saved
(B) As the lead can be broken if folded
(C) They can be safely folded as well
(D) So they can be conveniently available
(E) None of the above

702. (B) Broken lead in aprons can provide suboptimal
radiation protection.


703. A patient with severe spasticity is a candidate
for an intrathecal baclofen pump. He and his
family have heard that “these pumps get
infected.” How do you respond?
(1) Device-related infection is the most
common, potentially reducible, serious
adverse event associated with intrathecal
(2) The majority of infections occur at the
lumbar site
(3) Management of infections associated
with drug-delivery systems usually
involves the administration of antibiotics
and explantation of the device
(4) The chances of the pump getting
infected are minimal and the family
should only focus on the benefits that
the device provides

703. (B) The diagnosis of an implantable devicerelated
surgical-site infection is definitively
made by identification or culture of microorganisms
(most commonly bacteria) or both on
specimens from a clinically suspected surgical
wound or implant site. Signs of wound infection
include fever, erythema, edema, pain,
wound exudates, poor healing, or skin erosion
at the implant site. Meningismus indicates CSF
1. Infections related to the implantation of a SCS
or an intrathecal drug-delivery system is the
most common, potentially reducible, serious
adverse events associated with these devices.
2. In the comparison of drug-delivery devicerelated
infections in multicenter studies the
pump pocket was the site of infection
between 57.1% and 80% of the time, the
lumbar site was the infection location
between 13% and 33% of the time, and
meningitis was the infection between 10%
and 14.3% of the time.
3. Management of infections associated with
drug-delivery and SCS systems typically
involves administration of antibiotics and
explantation of the devices.
4. You should always worry about potential
The infection rates, based on the number of
infections that occurred and the number of
patients that were evaluated have varied from
2.5% to 9.0% of implanted patients. The highest
infection rate (9%), occurred in the 10-mL
SynchroMed pump that was used in pediatric
patients with spasticity of cerebral origin
(n = 100), predominantly spastic cerebral palsy.
The lowest infection rate, (2.5%), occurred in
the group that received intrathecal recombinant
methionyl human brain-derived neurotrophic
factor (BDNF) to treat amyotrophic
lateral sclerosis. 36 infections in 35 patients
were described in a total of 700 patients (5%
overall infection rate).


704. When trialing intrathecal medication and placing
intrathecal pumps, which of the following
is considered good technique?
(1) Antibiotics are given during the course
of the trial, and for 7 to 10 days after
permanent implant
(2) If the entry point is above L2, the
patient should be conversant, and the
angle of entry should be as shallow as
(3) Placing the patient in the lateral decubitus
position with the hips flexed, and
the knees bent
(4) Electrocautery is now considered the
gold standard for controlling bleeding

704. (A)
1. The most common antibiotics used are a
third-generation cephalosporin or vancomycin.
Intraoperatively, many physicians
irrigate the wound with antibiotic
solution. Adjustments to antibiotic regimens
should be made based on the most
common pathogens seen in the community
and medical center.
2. In most instances the needle entry point
into the intrathecal space is below L2.
Sometimes, although rare, the entry point is
at the level of the cord. If the entry point is
above L2, the patient should be communicating
with the physicians and nurses, and
the angle of entry should be as small as
possible. If any paresthesia is experienced,
the needle should be removed and repositioned. Once the catheter is properly
positioned, a purse-string suture should be
fashioned to secure the tissue around the
catheter. Then, an anchor should be used to
fasten the catheter to fascia. Given recent
studies on inflammatory masses at catheter
tips, whether the distal end of the catheter
should be placed near the supposed pain
generator or not is still up for debate.
3. While the patient may be positioned prone
for catheter placement, placing them in the
lateral decubitus position precludes having
to reposition them for pocket creation. The
usual site for pump placement is the lateral
anterior abdominal wall at the level of the
umbilicus. The pump should be anchored
in a manner to prevent flipping.
4. The physician should meticulously obtain
proper hemostasis during the case. Small
venous and arterial bleeders can be recognized
by retracting the wound after antibiotic
irrigation. Numerous techniques exist
to obtain hemostasis:
• Simple pressure
• Sponges soaked in 3% hydrogen peroxide
solution may be packed into the
wound for 3 to 5 minutes (may be very
helpful with small vessels)
• Electrocautery for more pronounced
bleeding [Note: overheating tissue can
cause trauma or seroma formation,
which can lead to delayed healing, dehiscence,
or infection of the wound]
• Suturing a vessel is still the gold standard
A large sterile pressure dressing should be
applied over the wound plus/minus an abdominal
binder to reduce the risk of seroma formation
and bleeding. Antibiotic ointment is also frequently
used immediately over the incision; it
may help in preventing the spread of infection.
When considering dressing changes, the
physician should be judicious—they can take
place daily or only if the dressing is excessively


705. Which of the following is (are) disease state(s)
that are amenable to treatment by intrathecal
drug-delivery system?
(1) Intractable spasticity related to cerebral
palsy and spinal cord injuries
(2) Interstitial cystitis
(3) Cancer-related syndromes
(4) Rheumatoid arthritis

705. (E) In the early 1980s intrathecal drug-delivery
was initiated for the treatment of intractable
spasticity related to cerebral palsy and spinal
cord injuries. This therapy eventually evolved
to use in implacable cancer pain. Intrathecal
preservative-free baclofen and morphine are
FDAapproved for the treatment of moderate to
severe spasticity and moderate to severe pain,
respectively. A study in oncology patients
showed a major improvement using intrathecal
medication delivery in cancer pain versus thorough
medical management in the areas of
tiredness, level of consciousness, and survival.
[Smith TJ, Staats PS, Deer T et al. Randomized
clinical trial of an implantable drug delivery
system compared with comprehensive medical
management for refractory cancer pain:
impact on pain, drug-related toxicity, and survival.
J Cli. 2002;20(19):4040-4049.]
Other disease states found to be responsive to
intrathecal drug-delivery systems are
• Spinal stenosis
• Radiculitis
• Compression fractures
• Spondylosis
• Spondylolisthesis
• Foraminal stenosis
• Arachnoiditis
• Syrinx
• Ankylosing spondylitis
• Spinal cord trauma
• Spinal infarction
• Paraplegia
• Cauda equina syndrome
• Peripheral neuropathy
• Phantom limb pain
• Rheumatoid arthritis
• Radiation neuritis
• Postherpetic neuralgia
• Postthoracotomy syndrome
• Interstitial cystitis
• Chronic pain of the abdomen and pelvis


706. A 56-year-old female who had an intrathecal
pump placed secondary to metastatic renal cell
carcinoma is having pain equivalent to a 6 on the visual analog scale (VAS). What is the
proper titration regimen?
(1) Increase dose 10% to 25% over 3 to 4 days
(2) Increase dose 25% to 50% daily
(3) Hourly rates should be adjusted 35% to
50% twice daily until pain relief is
(4) A therapeutic bolus should be considered

706. (C) Patients with a VAS pain scale of 7 to 10 may
necessitate inpatient/hospice care for pain treatment.
For those who wish to remain in a home
environment, a 50% to 100% increase in their
medication dose may be in order. Therapeutic
boluses should be administered to an end point of pain relief, as well as daily medication adjustments
to the same end point. Significant, abrupt
increase in medication may cause severe side
effects, and physicians should be available in
the first 12 hours following the modification, to
manage potential complications.


707. A 52-year-old female with pancreatic cancer
and her family are trying to decide between
continued medical management for pain versus
an intrathecal drug-delivery system. Believing
that this patient would most benefit from an
intrathecal pump, you tell them that studies
have shown that
(1) overall toxicity is better with intrathecal
(2) pain relief is better with intrathecal pumps
(3) intrathecal pumps improve fatigue and
level of consciousness in patients versus
medical management
(4) there is a trend to increased survival in
patients who have intrathecal pumps
versus those continuing with medical

707. (E) A multicenter, randomized, prospective
study compared intrathecal drug delivery to
comprehensive medical management. The
results showed a statistically significant advantage
of intrathecal pumps on
• Overall toxicity
• Pain relief
• Fatigue and level of consciousness
• Improved survivability
The study hinted that more patients with
moderate to severe cancer pain should be considered
for intrathecal pumps. [Smith TJ,
Staats PS, Deer T et al. Randomized clinical
trial of an implantable drug delivery system
compared with comprehensive medical management
for refractory cancer pain: impact on
pain, drug-related toxicity, and survival. J
Clin. 2002;20(19):4040-4049.]


708. Third occipital nerve
(1) innervates C2-3 facet joint
(2) curves around superior articular process
of the C2 vertebrae
(3) curves around superior articular process
of the C3 vertebrae
(4) innervates C3-4 facet joint

708. (B) The third occipital headache is caused by
third occipital neuralgia. The TON innervates
the C2-3 zygapophysial joint and curves
around the superior articular process of the C3
vertebral body. Among patients with whiplash
injuries, third occipital headache is common,
with a prevalence of 27%.


709. For the peripheral stimulation of the occipital
(1) the electrode should be parallel to the
occipital nerve in the occipital area of
the scull
(2) only a “paddle-” type electrode should
be used
(3) the entry site of the introducer needle
should be at T1-T2 level
(4) the electrode should be placed subcutaneously
at the C1-C2 level

709. (D) The occipital nerve stimulator is a useful
tool in managing occipital neuralgia. Although
paddle electrodes are not necessary they may
provide better coverage than the regular


710. T2 and T3 sympathetic block
(1) is used for treatment of upper extremity
complex regional pain syndrome (CRPS)
(2) will help by denervating the Kuntz
(3) can lead to pneumothorax
(4) should avoid radiofrequency of T2 and
T3 sympathetic ganglia

710. (A) T2 and T3 sympathetic blocks are a useful
tool in conjunction with stellate ganglion block
for upper extremity CRPS. By blocking them,
Kuntz nerves will be blocked that bypass the
stellate ganglion. RF denervation of these
nerves may lead to prolonged pain relief.


711. Vertebroplasty may be indicated for
(1) multiple myeloma
(2) chronic compression fractures of
vertebral body
(3) osteolytic metastatic tumors
(4) facet arthropathy

711. (A) Vertebroplasty is best used for acute vertebral
fracture where bone cement is percutaneously injected into a fractured vertebra in order to
stabilize it. Alternatively, kyphoplasty involves
placement of a balloon into a collapsed vertebra,
followed by injection of bone cement to
stabilize the fracture. It is not clear if one procedure
has an advantage over the other. Both
procedures may obtain almost immediate pain
relief. And they are indicated for painful compression
fractures because of osteoporosis and
metastatic tumors.


712. Complications from vertebroplasty include
(1) pulmonary embolus
(2) intradiscal leak of polymethyl
(3) paraplegia
(4) psoas muscle leak of polymethyl
methacrylate and femoral neuropathy

712. (E) Complications from vertebroplasty can be
serious. Intravascular injection of polymethyl
methacrylate can lead to pulmonary embolus
and spinal cord damage and leak into intrathecal
space can cause spinal cord injury. Lumbar
procedures may lead to leak into psoas muscle
and femoral neuropathy.


713. Which of the following is (are) correct with
regards to piriformis muscle injection?
(1) Should be done at medial part of a
(2) Botox can be used
(3) Nerve stimulation may aid in muscle
(4) Identification of the muscle can be done
through rectal examination

713. (E) Piriformis injection should be done in the
medial part of a muscle since the lateral part
contains more ligaments. If injection of local
anesthetics and steroids provides short-term
pain relief only, the injection of botulinum toxin
type Amay provide longer pain relief. The use
of nerve stimulator, fluoroscopy, and contrast
administration may help to assure proper
needle placement. Tenderness over the piriformis
muscle, positive Pace and Freiberg signs
and rectal examination can be helpful in examining
the piriformis muscle


714. SI joint pain
(1) is transmitted by the S1-S4 levels of
spinal nerves
(2) has been treated by the SI joint fusion
(3) can be relieved by blind steroid
(4) is transmitted by L4 medial branch, L5
dorsal ramus, and S1-3 lateral branches

714. (D)
1. The innervation of the SI joint is from L4
medial branch, L5 dorsal ramus, S1, S2, and
S3 lateral branches. Some authors also state
that the L3 medial branch may be involved.
2. SI joint fusion is used only in cases where
serious anatomical problems (eg, fracture)
are present in addition to pain.
3. SI joint injection should be done under fluoroscopic
guidance to assure accuracy of
needle placement.


715. Celiac plexus block can be performed by
(1) anterior approach
(2) retrocrural approach
(3) anterocrural approach
(4) lateral approach

715. (B)
1. Anterior approach was initial approach
described for blocking celiac plexus. Its
advantage is that patient can be in more
comfortable, supine position.
2. Although the retrocrural block may partially
block the nerve supply to the celiac plexus
actually blocks the splanchnic plexus.
3. Anterocrural approach is done with patient
in prone position using one or two needles.
Transaortic and transdiscal variation of this
approach has been published as well.
4. Lateral approach is not used for celiac
plexus block.


716. Ganglion impar block
(1) is indicated for testicular pain
(2) is indicated for sympathetically maintained
pain in perineal area
(3) is best performed by anococcygeal
(4) can be complicated by perforation of

716. (C)
1. Testicular pain is treated by ilioinguinal
block or lumbar sympathetic block.
2. Ganglion impar is the most caudal sympathetic
3. The ganglion impar is located at the level of
the sacrococcygeal junction that marks the termination
of the paired paravertebral sympathetic
chains. Initial approach described was
through anococcygeal ligament. However, the
trans-sacrococcygeal approach seems much
safer way to perform this procedure.
4. Perforation of rectum may occur in particular
if anococcygeal approach is used.


717. With cervical interlaminar epidural steroid
(1) loss of resistance technique can be inaccurate
in up to 50% cases
(2) unilateral medication spread can be
achieved in 50% cases
(3) contrast spread should be checked in
lateral views
(4) transforaminal approach is safer than

717. (A)
1. As a result of discontinuous ligamentum
flavum the loss of resistance is often inaccurate
in cervical levels and more often in
comparison to lumbar levels (30%).
2. The fluoroscopic guidance should be used
and medication should be deposited ipsilateral
to the pathology.
3. Final needle advancement and contrast
spread should be first checked in lateral fluoroscopic
4. Transforaminal approach (most likely
because of intravascular particulate steroid
uptake) can lead to serious complications
such as spinal cord infarction, quadriplegia,
and death.


718. Which of the following includes complication(
s) of intrathecal pump?
(1) Granuloma formation
(2) CSF leak
(3) Pump rotation
(4) Hormonal imbalance

718. (E)
1. Granuloma formation can occur at the tip
of the intrathecal catheter and can lead to
serious complications including spinal cord
2. CSF leak is a relatively common complication
of intrathecal pump placement.
3. Pump rotation can cause kinking of the
catheter and symptoms of increased pain
and withdrawal.
4. Intrathecal opioids can lead to serious hormonal
changes including weight gain.


719. In relation to increased pain in patient with
intrathecal opioid delivery which of the following
is (are) true?
(1) It can mean progression of disease
(2) Catheter kink should be considered
(3) One should look for withdrawal
(4) Opioids should be increased first

719. (A) Increased pain, in particular with withdrawal
symptoms should be considered as a
pump failure and treated promptly.


720. Which of the following is (are) drug(s) used in decompressive neuroplasty?
(1) Hyaluronidase
(2) Hypertonic saline
(3) Steroids
(4) Local anesthetics

720. (E) Combination of hyaluronidase and hypertonic
saline seems to increase the duration of
procedure effect. Intrathecal injection of hypertonic
saline can lead to serious complications
and should be performed carefully.


721. SCS been used for the treatment of
(1) interstitial cystitis
(2) postlaminectomy syndrome
(3) CRPS
(4) sympathetically mediated pain

721. (E) Traditional indications for SCS include postlaminectomy
syndrome and CRPS. Indications
have been expanding. Intestinal cystitis is now
a commonly accepted indication. SCS is an
accepted method for effective treatment of
sympathetically mediated pain.


722. Spinal cord stimulation
(1) should be used early in the course of the
postherpetic neuralgia pain syndrome
(2) has been found efficacious for the failed
back surgery syndrome
(3) has been used for peripheral vascular
disease and ischemic disease
(4) has a proven and elucidated mechanism
of action

722. (A) According to a review in 2008, SCS should
be considered early in the course of postherpetic
neuralgia and peripheral nerve stimulation
should be considered if SCS fails. SCS is
about 50% effective for failed back surgery syndrome
and more so effective for peripheral vascular
disease and ischemic disease. Although
the gate control theory is a commonly cited
mechanism of action for SCS, literature reflects
that this one mechanism alone is not sufficient
to explain the mechanism of action. According
to a 2002 review article, there are 10 proposed
mechanisms of action found in literature.
[Oakley JC, Prager JP. Spinal cord stimulation:
mechanisms of action. Spine. 2002; 27(22):


723. The transverse tripolar SCS arrangement
(1) involves a central anode surrounded by
(2) contributes maximum dorsal column
stimulation with minimal dorsal root
(3) is most frequently used to improve
stimulation of the feet
(4) usually involves an octapolar spinal
midline lead and two adjacent
quadripolar leads

723. (C) Transverse tripolar SCS on involves a central
cathode surrounded by anodes. This is proposed
to drive current deeper and thus
stimulate fibers innervating the back. Therefore
is it used to cover back pain, not foot pain.
Statement (4) is also correct as most current
SCS systems allow up to a total of 16 leads.


724. Which of the following is (are) true for SCS for
the indication of angina pectoris?
(1) Improves exercise capacity
(2) Probably only helps for a year and then
the stimulator should be removed
(3) In addition to providing antianginal
effects it also provides a reduction in
(4) Is contraindicated because it masks significant
ischemic events

724. (B) In a 2006 review article SCS was concluded
to increase exercise capacity as well as decrease
use of short-acting nitrates and improve quality
of life. The review also found that at 5 years
60% of patients still had beneficial effects.
Exercise stress testing and electrocardiogram
(ECG) monitoring evidence showed reduced
ischemia in addition to the antianginal effects.
Pain perception remains intact and patients
were still able to detect significant ischemic
events. .]


725. Which of the following is (are) the risk(s) associated
with SCS?
(1) Epidural hematoma
(2) Spinal cord injury
(3) Implanted pulse generator failure
(4) Electromechanical failure of lead or
extension cable

725. (E) All listed factors are risks of SCS. Other
risks include nerve injury, dural puncture,
infection, and electrode migration.


726. Which of the following is (are) true regarding
SCS for visceral pain?
(1) SCS suppresses visceral response to
colon distention in animal models
(2) SCS is a first-line treatment for visceral
(3) Case studies have indicated SCS may be
helpful for visceral pain but at this time
there is a lack of supporting randomized
controlled trials
(4) A good lead placement for stimulation
of chronic pancreatitis would logically
be around T12 or L1

726. (B) In animal models, SCS has been shown to
suppress visceral responses. There have been
multiple case reports of SCS being used successfully
for visceral pain; however, current
practice parameters do not address treatment
of such pain. Since the pancreas is innervated
by spinal segments around T5-T11, a lead
placement would be much too low of a logical
starting place. One case study reported placing
the lead at T6 resulting in appropriate stimulation
for treatment of chronic pancreatitis.


727. Which of the following is (are) the best
answer(s) regarding lead spacing and electrical fields created by a dual-lead stimulation system as pictured?
(1) With larger distances between anodes
and cathodes, the electric field tends to
form a sphere
(2) With tighter lead spacing and smaller
distances between anodes and cathodes,
the electric field is pulled towards the
(3) Tight lead spacing increases the ratio of
dorsal column to dorsal root stimulation
(4) The anode is the positive contact and
the cathode is the negative contact

727. (E) Anode is the correct designation for a positive
contact and cathode is the correct designation
for a negative contact. With a dual-lead
system as pictured, the electric field would be
pulled toward the anode if lead spacing were
tight. With larger lead spacing, the electric field
would tend to be more spherical and positioned
around the cathode. Tight lead spacing
increases the dorsal column to dorsal root stimulation
ratio because the less spherical electric
field would stimulate less laterally and therefore
would have less stimulation in the areas of
the nerve roots.


728. Which of the following should be considered
when selecting patients for SCS?
(1) Disease pathology
(2) Untreated drug addiction
(3) Patient comorbidities
(4) Physician’s monthly case quota

728. (A) According to a review article on selection
criteria for SCS, selection criteria may relate to
the patient’s disease state or to other important
patient characteristics. Current randomized
controlled trials or prospective trials
support efficacy of SCS for certain disease
states such as failed back surgery syndrome,
CRPS, axial back pain, postherpetic neuralgia,
neuropathy, and pelvic pain. Current case
report evidence exists for SCS in the treatment
of ischemic limb pain, and visceral pain.
Anginal pain has also been investigated.
Patient characteristics of concern include systemic
disease such as diabetes, immunocompromised,
degree of stenosis especially for
cervical placed leads, anticoagulation, psychologic
comorbidities, unrealistic outcome expectations,
and, untreated drug addictions.
[Oakley JC. Spinal cord stimulation: patient
selection, technique, and outcomes.


729. Which of the following is (are) considered indication(
s) for SCS?
(1) Phantom limb pain
(2) Spinal cord injury pain
(3) Intractable abdominal or visceral pain
(4) Neurogenic thoracic outlet syndrome

729. (E) The indications for SCS are expanding. All of the listed etiologies are now considered indications for SCS.


730. Which of the following is (are) true regarding
the history of electrical stimulation for the treatment
of pain?
(1) Electrical stimulation for the treatment
of pain dates back to the first century ad
when electrical fish were documented to
be used in the treatment of gout
(2) Implantable SCS were used for treatment
of pain for a decade prior to the
published gate control theory of pain
(3) Early stimulation case reports were of
peripheral nerve stimulation; later
emphasis turned toward SCS
(4) Psychiatric and/or psychologic screening
evaluation prior to implants was a
new idea imposed upon physicians by
health maintenance organizations in the

730. (B)
1. Scribonius Largus documented application
of the live black torpedo fish under the foot
for treatment of the pain of gout. “For any
type of gout a live black torpedo should, when the
pain begins, be placed under the feet. The patient
must stand on a moist shore washed by the sea
and he should stay like this until his whole foot
and leg up to the knee is numb. This takes away
present pain and prevents pain from coming on if
it has not already arisen. In this way Anteros, a
freedman of Tiberius, was cured.”
2. The gate control theory of pain was published
in 1965. This laid the theoretical foundation
for electrical stimulation for pain.
The first modern case report of electrical
stimulators for treatment of pain was 2 years
later. It described eight cases in which sensory
nerves or roots were stimulated resulting
in relief of pain. [Melzack R, Wall PD.
Mechanisms: a new theory. A gate control
system modulates sensory input from the
skin before it evokes pain perception and
response. Science. 1965;150(3699).
Wall PD, Sweet WH. Temporary abolition
of pain in man. Science. 1967;155(758):108-109.]
3. In the peripheral nerves, motor and sensory
fibers are within closer vicinity. The window of amplitude available to provide analgesia
without excessive motor stimulation is
therefore much less than in the spinal cord
where sensory and motor fibers run in more
discrete and separate pathways. This
played a role in switching emphasis from
peripheral nerve stimulation toward SCS.
4. The first documented cases of modern day
stimulation for pain was a case series of eight
patients published in 1967. This case series
reported three of the eight patients received
psychiatric evaluation prior to the procedures.
The psychiatric/psychologic evaluation
gives the patient an opportunity to belay
anxiety, ask questions, address body image
issues, and communicate expectations


731. Which of the following is (are) accurate statement(
s) regarding neuromodulation of the
sacral nerves?
(1) Sacral neuromodulation is not effective
for idiopathic urinary frequency
(2) Both percutaneous and surgical lead
placement techniques have been
(3) Must be performed by a surgeon
because only a surgical technique is
(4) Urgency and urge incontinence are

731. (C) Sacral neuromodulation has been reported
as effective for idiopathic urinary frequency,
urgency, and urge incontinence. Both percutaneous
and surgical sacral neuromodulation
procedures have been described. Percutaneous
techniques include (1) placement of a lead
directly into the sacral nerve root foramen and
(2) a percutaneous retrograde approach.
Surgical techniques include (1) performing a
sacral laminectomy and attaching the electrodes
directly to the sacral nerve roots and
(2) dissection to sacral periosteum where a
plastic anchor is used to affix a transforaminal
lead. Techniques that are limited to one lead
placement may have limitations in terms of
efficacy for certain indications. While a single
lead has been generally efficacious for voiding
dysfunctions, chronic neuropathic pain syndromes
may benefit from a more extensive field
of neuromodulation with additional electrodes


732. Which of the following is (are) true regarding
radiofrequency procedures?
(1) Pulsed radiofrequency lesioning temperature
goal is generally around 42°C
to 43°C
(2) Prior to application of the radiofrequency
lesion, sensory testing should be
applied at 2 Hz
(3) The standard pulsed radiofrequency
lesion is 500,000 Hz for 20 milliseconds
pulses once every 0.5 second for 90 to
240 seconds
(4) Prior to application of the radiofrequency
lesion, motor testing should be
applied at 50 Hz

732. (B)
1. Temperatures above 45°C cause irreversible
neural tissue damage. If temperatures of
45°C are reached, then the voltage should
be decreased to compensate.
2. Sensory testing is applied at 50 Hz.
3. The pulsed technique allows tissues to
cool somewhat between cycles. A voltage of 45 V generally corresponds to a 43°C
tip temperature. If the tip temperature
exceeds 43°C, then the voltage should be
4. Motor testing is applied at 2 Hz.


733. Which of the following element(s) is (are) necessary
to complete a radiofrequency circuit?
(1) The radiofrequency generator
(2) Insulated needle cannula with radiofrequency
(3) Dispersive electrode (grounding pad)
(4) The patient

733. (E) All the options mentioned in the question
are required elements to complete the circuit.
The current goes from the probe tip, through
the patient and to the grounding pad which
carries the current back to the radiofrequency


734. Which of the following is (are) the possible
mechanism(s) of action of radiofrequency
(1) Vascular injury causing endoneural
(2) Formation of a static electric field
(3) Lipid extraction with protein precipitation
(4) Generation of heat

734. (C) Formation of a static electric field and generation
of heat are two phenonemon that have
been postulated as possible mechanisms of
action of radiofrequency ablation. The mechanism
of action of cryoablation involves vascular
injury which causes severe endoneural
edema. The mechanism of action of alcohol
ablative techniques is lipid extraction with protein


735. Which of the following is (are) the most accurate
answer(s) regarding radiofrequency treatment
of the SI joint?
(1) Evidence is strong for efficacy of
radiofrequency ablation techniques for
SI joint pain
(2) The universally accepted screening protocol
prior to SI joint injection involves
SI tenderness, positive SI provocative
maneuvers, and two positive local anesthetic–
only SI joint injection procedures
(3) There is no evidence for the role of
pulsed radiofrequency treatment of SI
joint pain
(4) Radiofrequency treatment of sacral lateral
branches have been proposed for
efficacious treatment of SI joint pain

735. (D)
1. Although there are several studies looking
at radiofrequency neuroablation for the SI
joint, according to a recent systematic
review evidence is still limited for its therapeutic
2. Although there are guidelines such as those
posed by International Association for the
Study of Pain (IASP), evidence and universal
acceptance are still lacking. Some studies
have refuted SI provocative maneuvers
as predictive at all while others found that
three of five positive provocative maneuvers
provide predictive value. The role of
adding steroids to diagnostic SI injections is
similarly debated.
3. Pulsed radiofrequency treatment was given
to 22 patients with injection evidence of SI
pain. Sixteen patients (73.9%) had 50% or
better relief for more than 3 months.
4. In a 2003 pilot study, 8 of 9 patients experienced
50% or better pain relief after
radiofrequency lesioning at L4 primary
dorsal rami and S1-S3 lateral branches.
Relief persisted at 9 month follow-up.


736. Purported advantages of percutaneous radiofrequency
lesions over other neuroablative techniques
(1) predictable and quantifiable lesions
(2) avoids the extensive soft tissue damage
of surgical techniques
(3) ability to confirm needle-tip proximity
to sensory and motor nerves
(4) ability to cover a wide field

736. (A) Other advantages of radiofrequency lesions
include avoids sticking and charring (in contrast
to direct current electrical lesions), no gas formation
(in contrast to direct current electrical
lesions), impedance monitoring, and amenable
to fluoroscopic and CT guidance. Ability to identify
needle-tip proximity to motor and sensory
nerves is a characteristic of radiofrequency procedures,
although cryoanalgesia probes are also
available with built-in nerve stimulators. Ability
to cover a wide field is not an advantage of percutaneous
radiofrequency lesion. Percutaneous
radiofrequency techniques deliver relatively
smaller, more defined treatment areas and therefore
a great deal of lesions would be needed in
order to cover a wide field target.


737. Which of the following is (are) accurate regarding
the history of ablation techniques?
(1) Norman Shealy reported the first use of
radiofrequency lesioning for treatment
of facet pain in 1975
(2) The first report of percutaneous
radiofrequency lesioning for treatment
of pain came in 1981
(3) Slappendel reported the first clinical use
of pulsed radiofrequency lesioning in
(4) Although a modern cryoneuroablation
device was developed and refined in the
1960s, the application for pain management
gained popularity in the 1980s

737. (E) These are all accurate historical events as
described and cited in current literature
reviews. Pulsed radiofrequency techniques
have received growing interest since 1997,
when treatment of the cervical spinal dorsal
root ganglions with pulsed radiofrequency
suggested efficacy and safety. In 1961, Cooper
described a device which used liquid nitrogen
in a hollow tube that was insulated at the tip
and achieved temperatures as low as −190°C.
He published his description in a hospital bulletin.
Six years later an ophthalmic surgeon by
the name of Amoils improved on the device.
Lloyd coined the term “cryoanalgesia” in 1976.
The technique was popularized in the 1980s,
but publications have declined since. [Cooper
IS, Lee AS. Cryostatic congelation: a system for
producing a limited, controlled region of cooling
or freezing of biologic tissues.


738. Which of the following is (are) accurate regarding
lesion size?
(1) The size of a continuous radiofrequency
lesion depends on temperature induced
(2) The size of a continuous radiofrequency
lesion depends on the width of the needle
(3) A 2 mm cryoanalgesia probe forms an
ice ball about 5.5 mm thick
(4) A 1.4 mm cryoanalgesia probe forms an
ice ball about 3.5 mm thick

738. (E) The size of a continuous radiofrequency
lesion depends on temperature, width of
needle, and length of exposed (uninsulated)
cannula. The 1.4-mm cryoanalgesia probe
forms an ice ball about 3.5 mm thick, while the larger 2-mm probe forms and ice ball about 5.5 mm thick. Thus the ice ball is about 2.5 to 2.75 times larger than the probe for these size probes.


739. Which of the following is (are) components of
a cryoanalgesia system?
(1) Outer tube with smaller inner tube
(2) Pressurized gas in inner tube
(3) Fine aperture in tip of inner tube which
allows gas to rapidly expand in tip of
outer tube
(4) Fine aperture in tip of outer tube which
allows gas to escape the tube system

739. (A) Acryoprobe is comprised of a tube within
a tube. The inner tube is pressurized with a
gas such as nitrous oxide or carbon dioxide at
600 to 800 psi. As the gas escapes through a
narrow aperture at the tip of the inner tube, it
(the gas) abruptly expands in the larger outer
tube at a lower pressure of about 10 to 15 psi.
As the gas expands, it (the gas) cools. This is
known as the Joule-Thompson effect. An ice
ball then forms at the tip of the probe. The gas
does not escape out through a fine aperture in
the tip of the outer tube. This would allow the
gas to enter the patient’s tissues. Instead, gas
escapes back up the larger outer tube in a
closed system design


740. Which of the following is (are) potential neuroablative
procedure treatment options?
(1) Radiofrequency ablation of the L2
ramus communicans for treatment of
L4-L5 discogenic pain
(2) Phenol neurolysis for treatment of the
lumbar sympathetic plexus for treatment
of CRPS of the lower extremity
(3) Radiofrequency ablation for treatment
of the lumbar sympathetic plexus for
treatment of CRPS of the lower
(4) Cryoablation for the treatment of pain
owing to superior gluteal nerve

740. (E)
1. It has been postulated that the sinuvertebral
nerves at each lumbar level transmit
sensory information from the intervertebral
discs to the paravertebral chain on each
side. The rami communicans then communicate
this sensory information to the dorsal
root ganglia at L1 and L2.
2. and 3. Both radiofrequency and phenol
lumbar sympathetic neurolytic techniques
have been described for the treatment of
lower extremity CRPS.
4. Cryoablation has been utilized for pain of
the superior gluteal nerve. (Trescot, Pain
Physician, 2003, v. 6, p. 345-360, Cryoanalgesia
in interventional pain management)


741. Which of the following is (are) potential advantage(
s) of pulsed radiofrequency procedure
over continuous radiofrequency ablation?
(1) Pulsed radiofrequency procedure is virtually
painless as compared to continuous
radiofrequency ablation during
which patients often complain of pain
(2) Overwhelming evidence of greater efficacy
with pulsed radiofrequency procedure
over continuous radiofrequency
(3) As compared to pulsed radiofrequency
ablation, continuous radiofrequency
ablation of lumbar medial branches carries
a higher risk of inducing spinal
instability secondary to multifidus
muscle denervation
(4) Complications caused by needle injury
of tissues is less with pulsed radiofrequency
procedure compared to continuous
radiofrequency ablation

741. (B)
1. Pulsed radiofrequency procedure is virtually
painless. Continuous radiofrequency
ablation is painful with application.
2. There is debate in literature as to whether
pulsed radiofrequency procedure is as efficacious
as radiofrequency ablation.
3. In addition to innervating the zygapophysial
joint, the medial branch of the dorsal ramus
also innervates the multifidus, interspinales, and intertransversarii mediales muscles, the
interspinous ligament, and, possibly, the ligamentum
4. In both cases a cannula and radiofrequency
probe of similar size are inserted.


742. Which of the following is (are) correct regarding
impedance measurement during radiofrequency
(1) While performing a radiofrequency procedure,
the lower the impedance value
the better the expected outcome
(2) Impedance measurement can detect
needle-tip entry into different mediums
such as vascular structures or periosteum
(3) Impedance values are neither customary
nor necessary when using fluoroscopic
(4) Impedance measurement can detect
breaks or short circuits in the electrical

742. (C)
1. Too low an impedance may indicate the
needle tip is in nontarget tissues such as
vasculature, CSF, or nucleus pulposus.
2. This statement is correct.
3. It is traditional to use impedance information
in assisting needle-tip placement even
during fluoroscopically guided procedures.
4. This statement is correct. Superior gluteal
nerve entrapment is amenable to cryoablation.