Proper Use of Epidural Injections
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True or false?
Every
patient who receives lumbar epidural injections should always get three
of them, because this is the most effective treatment?
Lumbar epidural injections are the best treatment for chronic low back pain?
All
pain that radiates into the buttocks or thighs is caused by nerve root
irritation and is treated with lumbar epidural injections?
Answers: False, False and False.
There
can be no doubt that lumbar epidural injections are one of the
mainstays of modern pain management and are extremely effective for
certain, well-defined pain conditions.
However, as the field
of pain medicine continues to evolve, we are discovering that we have
the ability to identify specific pain generators in the spine. These
areas can be much more effectively treated with techniques other than
lumbar epidural injections.
There are numerous possible
sources of chronic low back pain, but the most common causes
(especially in today's aging population) are facet joint arthritis and
degenerative disc disease.
To make the diagnostic picture
harder, both of these problems can present as low back pain with
radiation into the thigh, imitating lumbar radiculopathy.
So, what are practical guidelines for use of epidural injections?
1)
Lumbar epidural injections should be performed chiefly for radicular
symptoms, not low back pain. (There are numerous other procedures for
acute or chronic low back pain.)
2) The number of epidural
injections performed on a patient is solely a function of response to
the first injection. If pain relief is greater than 70%, usually no
further injections are performed. If no pain relief is obtained, then
no further epidural injections are performed, but the investigation for
the etiology of the pain continues. If the pain falls between these
values, further injections may be beneficial.
3) All radicular
pain is not an indication of nerve root irritation caused by
intervertebral disc disease. Radiating symptoms may be caused by facet
joint arthropathy, degenerative disc disease, sacroiliac joint problems
or piriformis syndrome.
More on Epidural Steroids
The
use of epidural steroids has become one of the most common conservative
methods for the management of back pain. All types of back pain can
show good initial response to epidural steroids. The best long-term
results are found in those syndromes in which nerve root irritation or
compression is present. Epidural steroids can be used at all levels of
the spinal cord: cervical, thoracic and lumbar. For patients who have
undergone a lumbar laminectomy, it is possible to place steroids into
the epidural space using a caudal approach.
Mechanism of action
Steroids
relieve pain by reducing inflammation and by blocking transmission of
nociceptive C fiber input. Steroids decrease inflammation by inhibiting
the action of phospholipase A2, which has been found to induce membrane
injury and edema in the experimental model. Additionally, steroids
prevent the development of ectopic neural discharges which may be
responsible for back pain. This has been thought to be a direct
membrane action of the steroid. Placing steroids directly into the
epidural space versus systemic administration creates the advantage of
being able to use a much smaller dose with less risk of side effects
and longer duration of relief.
Epidural injections are
typically a local anesthetic-steroid mixture. The local anesthesia
supplements the pain control by providing a rapid onset of pain relief
and breaking the pain cycle. Additionally, local anesthetics will block
any neuropathic pain of sympathetic origin. The transient analgesia
associated with the anesthetic effect may allow a freer range of motion
and thereby alter adhesions interfering with the mobility of the dural
sleeve of the nerve root. Anesthetics also produce muscle relaxation ,
thus allowing proper realignment of facet joints. A mechanical effect
for the pain relief has been suggested as well. The volume of solution
injected has been thought to contribute to the breakdown of adhesions
that may be present.
Indications
Epidural
steroid injections have been recommended to deliver the drug directly
to the area of the affected nerve roots, thereby decreasing the
systemic effect of the administered steroid. Epidural steroids are
indicated in the treatment of nerve root irritation resulting in back
pain and neurologic symptoms. Signs of nerve root irritation include
radicular pain, dermatomal hypesthesia, weakness of muscle groups
innervated by the involved nerve roots, decreased deep tendon reflexes
and lumbar pain with passive straight leg raising.
Response to
the epidural steroid injection is related to the duration of symptoms.
Patients who have had symptoms less than 3 months have response rates
of 83-100%. When radiculopathy has been present for 6 months or less,
response decreases to between 67-81%. Patients with symptoms over one
year have a response rate of approximately 46%. Additionally, patients
with shorter duration of symptoms will have a more sustained relief
than those with chronic pain.
Technique
Epidural
steroids can be introduced into the epidural space anywhere from C-6 to
the sacral hiatus. The injection is usually done at the level of the
affected nerve roots. Complications of epidural steroid injections
fortunately are rare. The rate of dural puncture is usually 0.5% or
less. Some of these patients may develop a post-dural puncture
headache. Systemic steroid effects are infrequent, although in some
patients suppression of plasma cortisol levels may occur.
Summary
In
conclusion, epidural steroid injection is a valuable technique in the
treatment of back pain. It has its highest success if combined with
other modalities such as bed rest, analgesics, muscle relaxants,
physical therapy, training in proper body mechanics and management of
any associated psychological, financial or work-related problems.
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