What is an epidural?
An epidural is an injection that delivers steroids directly into the epidural space. The epidural space is the space between the vertebral wall and membrane, and is filled with fat and small blood vessels. It is located just outside the dural sac, which surrounds the nerve roots and the fluid that the nerve roots are bathed in (cerebrospinal fluid).
An epidural steroid injection can be highly effective because it delivers the medication directly to the site of inflammation to reduce it.
When is an epidural typically recommended?
In general, epidural injections are used to help provide pain relief to enable patients to progress with their rehabilitation. Individuals who have less pain and feel more comfortable are generally able to work on the active therapies - such as stretching, strengthening/pain relief exercises and low impact aerobic conditioning - that are critical in rehabilitating the lower back.
Several common conditions - including lumbar disc herniation, degenerative disc disease, and lumbar spinal stenosis - can cause severe acute or chronic low back and/or leg pain. For these and other conditions that can cause chronic pain, an epidural steroid injection may be a useful, effective non-surgical treatment option.
What are the benefits?
The benefits of the epidural steroid injections include a reduction in pain, primarily in leg pain. Patients seem to have a better response when the injections are coupled with an organized therapeutic exercise program.
While the effects of an epidural injection tend to be temporary—providing relief from pain for one week up to one year—an epidural can be very beneficial for patients during an episode of severe back pain. Importantly, it can provide sufficient pain relief to allow the patient to progress with their rehabilitation program.
An epidural is generally successful in relieving pain for approximately 70% of patients. If a patient does not experience any pain relief from the first injection, further injections will probably not be beneficial. However, if there is some improvement in pain, one to two additional injections may be recommended.
How is the injection performed?
An epidural steroid injection usually takes between 15 and 30 minutes. The patient lies on their front, flat on an x-ray table. Prior to the injection, the skin is numbed with a local anaesthetic. Sedation is often administered to lessen anxiety and reduce pain associated with stretching of the dura during the injection.
X-ray is considered important in guiding the needle into the epidural space, as controlled studies have found that medication is misplaced in 13% to 34% of epidural injections that are done without X-ray.
Once the needle is in the exact position, the steroid solution is injected. If a sedative is used, the patient will need to be monitored after the procedure.
The patient may experience numbness of the buttock and legs associated with the anaesthetic, which wears off within a few hours. Very occasionally, if the patient is sensitive to the anaesthetic, he or she may experience ‘weakness of the bladder’ which is again a transient phenomenon and wears off after a few hours.
Patients are usually asked to rest on the day of the epidural steroid injection. Normal activities (those that were done the week prior to the injection) may typically be resumed the following day.
How frequently can epidural steroid injections be performed?
In general, it is considered reasonable to perform up to three injections per year. If one or two injections lessen the patient’s low back and/or leg pain, it is preferable to save the third injection for any potential recurrences of back pain later in the twelve-month period.
What are potential risks and side effects?
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 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 just 0.1% to 0.01% of injections
- Bleeding - this is a rare complication and is more common for patients with underlying bleeding disorders
- Nerve damage - extremely rare
- 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.
- 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, 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:
- menstrual irregularities
- transient flushing
- iIncreased appetite
Lumbar epidural steroid injections should not be performed on patients who have a local or systemic bacterial infection, are pregnant (if xray is used) or have bleeding problems. Epidurals 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.
In general, epidural is considered a safe, simple and effective way to control back pain or leg pain for some conditions.
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