What are potential risks and side effects of an epidural steroid injection?

Risks of an epidural steroid injection
As with all invasive medical procedures, there are potential risks associated with lumbar (lower back) epidural steroid injections. Generally, however, there are few risks associated with epidural steroid injections and they tend to be rare. Risks may 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. Bleeding is a rare complication and 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.

Paralysis is not a risk since there is no spinal cord in the region of the epidural steroid injection.

Side effects of an epidural steroid injection
In addition to risks from the injection, there are also potential risks and side effects from the steroid medication. These side effects from an epidural steroid injection tend to be rare. Side effects from steroids are more common when taken daily for several months. Risks and side effects may include:

A transient decrease in immunity
High blood sugar
Stomach ulcers
Severe arthritis of the hips (avascular necrosis)
Cataracts
Transient flushing
Increased appetite.

Who should avoid epidural steroid injections
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 steroid injections should also not be performed on 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).