An epidural injection delivers steroids into the epidural space around spinal nerve roots to relieve pain – back pain, leg pain, or other pain—caused by irritated spinal nerves. The steroid used in the epidural steroid injection reduces the inflammation of those nerves, which is often the source of the pain. It is important to note that an epidural steroid injection should not be considered a cure for back pain or leg pain: rather, the goal is to
help patients get enough pain relief in order to be able to progress with their rehabilitation program. An epidural steroid injection  significantly reduces pain for approximately 50% of patients. It works by delivering steroids directly to the painful area to help decrease the inflammation that may be causing the pain. It is thought that there is also a flushing effect from the injection that helps remove or “flush out” inflammatory proteins from around the structures that may cause pain. In addition to relieving pain, the process of natural healing can occur more quickly once the inflammation is reduced.
Spinal nerves can become inflamed due to irritation from a damaged disc or from contact with a bone spur.
Depending on which part of the spine the inflamed nerves are located in, pain and/or other symptoms (such as
numbness, tingling) may be experienced in different areas of the body, as shown:

Nerve irritation in the cervical spine

• Neck pain, or tingling, numbness
• Shoulder pain, or tingling, numbness
• Arm pain, or tingling, numbness

Nerve irritation in the thoracic spine

• Upper back pain
• Pain along the ribs to the chest wall
• Pain in the abdomen (rarely)

Nerve irritation in the lumbar spine

• Low back pain
• Hip pain
• Buttock pain
• Leg pain, or numbness, tingling

Anatomy of the spinal nerves and dura
There is a membrane called the dura covering the nerve roots in the spine. Around the dura is a sleeve-like space
called the epidural space. Before nerves can travel from the spine into the arms, chest, and legs, they travel through
the epidural space, and exit through small nerve holes. The medication from the epidural steroid injection is placed
in the epidural space.

Epidural steroid injection procedure
The injection procedure for an epidural includes the following steps:

• An IV is started so that medicine can be given for relaxation if desired.
• The patient lies face down on an x-ray table and the skin is well cleaned with an antiseptic.
• The area where the epidural needle will be inserted is numbed with a local anesthetic.
• Fluoroscopy (a guided X-ray procedure where the doctor can watch the placement and
  movement of the needle) will be used to direct a small needle into the epidural space. The patient
  will feel some pressure during this part. Fluoroscopy is important in this procedure to help ensure
  correct placement of the medications.
• A contrast dye is injected to confirm that the medicine spreads to the affected nerve(s) in
  the epidural space.
•  A combination of numbing medicine (an anesthetic) and time released anti-inflammatory
  medicine (a steroid) is injected.

The procedure usually takes approximately 30 minutes, followed by about 45 minutes of recovery time at the clinic.
On the day of the epidural steroid injection the patient should not drive. Rest is needed and strenuous activities
must be avoided on the day of the epidural steroid injection.

Epidural injection results and follow-up
Following the epidural injection, some partial numbness from the anesthetic may occur in the patient’s arms or legs.
Any partial numbness usually subsides after a few hours. Any remaining pain needs to be reported to the physician,
and ideally the patient should keep a “pain diary” to record the pain relief experienced over the next week. After the
pain diary is returned to the treating physician, the physician should be kept informed of the results in order to plan
future tests and/or treatment if needed.
There may be an increase in the patient’s pain that may last for up to several days. This may occur after the
numbing medicine wears off but before the steroid has had a chance to work. Ice packs may help reduce the
inflammation and will typically be more helpful than heat during this time. Improvements in pain will generally occur
within 10 days after the epidural injection, and may be noticed as soon as one to five days after the injection.
Regular medicines may be taken after an epidural steroid injection. On the day following the procedure, the patient
may return to his or her regular activities. When the pain has improved, regular exercise may be resumed in
moderation. Even if improvement is significant, activities should be increased slowly over one to two weeks to avoid
recurrence of pain.

Epidural results and precautions
As with any medical procedure, there are certain drawbacks and potential risks associated with an epidural steroid
injection for back pain, leg pain or arm pain. One of the most important issues to consider is that the procedure only
tends to significantly lessen the patient’s pain in about 60-75% of the patients.

Effectiveness of epidural injections
Unfortunately, epidural steroid injections are not always effective—it is estimated that they help relieve the pain in
about 65%-75% of the patients. In some cases the pain relief will be permanent. In others, the pain will be lessened
enough to allow the patient to progress with rehabilitation and exercise, which helps the patient heal and find pain
relief on a long-term basis.
If excellent, complete pain relief is obtained from the first epidural injection, there will be no need to repeat it. If there
is a partial benefit (greater than 30% relief from pain) the epidural injection can be repeated for possible additional
benefit, or it may be necessary to conduct additional tests to more accurately determine what is causing the patient’s
pain. Up to three epidural steroid injections may be performed within a one-year period, spaced at least two to four
weeks apart. If the initial injection provides minimal benefit (less than 30% pain relief) the physician may either
repeat the injection, or try a different type of injection or treatment.

• Potential risks and complications
  As with all invasive medical procedures, there are potential risks associated with epidural steroid injections.
  However, in general the risk is low, and complications are rare. Potential risks include:
  Infection. Minor infections occur in 1% to 2% of all injections. Severe infections are rare, occurring in 0.1% to
  0.01% of injections.
• Bleeding. A rare complication, bleeding is more common for patients with underlying bleeding disorders.
• Nerve damage. While extremely rare, nerve damage can occur from direct trauma from the needle, or
  secondarily from infection or bleeding.
• Dural puncture (“wet tap”). A dural puncture occurs in 0.5% of injections. It may cause a post-dural puncture
  headache (also called a spinal headache) that usually gets better within a few days. Although rare, a blood patch
  may be necessary to alleviate the headache from a dural puncture.

For a lumbar epidural injection, paralysis is not a risk since there is no spinal cord in the region of the epidural
steroid injection. In addition to risks from the injection, approximately 2% of patients will experience side effects from
the steroid medication, such as:

• Transient flushing with a feeling of warmth (‘hot flashes’) for several days
• Fluid retention, weight gain, or increased appetite
• Elevated blood pressure
• Mood swings, irritability, anxiety, insomnia
• High blood sugar—diabetic patients should inform their primary care physicians about the injection prior to
  their appointment
• Transient decrease in immunity
• Cataracts—a rare result of excessive and/or prolonged steroid usage
• Severe arthritis of the hips or shoulders (avascular necrosis)—a rare result of excessive and/or prolonged
  steroid usage

Lumbar epidural steroid injections should not be performed on patients who have a local or systemic bacterial
infection, are pregnant (if fluoroscopy is used) or have bleeding problems. Epidural injections should also not be
performed for patients whose pain is from a tumor or infection, and if suspected, an MRI scan should be done prior
to the injection to rule out these conditions.
Injections may be done, but with extreme caution, for patients with allergies to the injected solution, uncontrolled
medical problems (such as congestive heart failure and diabetes), and those who are taking aspirin or other
antiplatelet drugs (e.g. Ticlid, Plavix).