An Epidural Steroid Injection (ESI) is an anesthetic injection given into the epidural space in the spine, between the bony outer walls of the spinal canal and the membrane which covers the spinal cord.
The epidural space is essentially the space between the dura mater and the vertebral wall and is filled with fat and small blood vessels, located outside the dural sac.
Sometimes, a flushing solution, such as the lidocaine or normal saline is also inserted in addition to the anesthetic, as a part of the epidural, which ‘flush out’ the pain-causing inflammatory proteins from around the area.
When is it used?
An epidural is often considered to be the best non-surgical treatment option in cases where lumbar disc herniation, degenerative disc disease and lumbar spinal stenosis cause severe acute or chronic low back pain.
Used as the last pharmacologic measure in conservative treatment before surgical intervention is sought, epidurals provide adequate pain relief to enable patients to progress with their rehabilitation.
For an epidural to be most effective, it is important that it is given in the first weeks of the onset of pain. Usually, two to three injections over a course of one to two weeks are administered.
How does it work?
Epidural steroid injections are most effective if a nerve root compression is present. Patients with lower back pain are often diagnosed with inflammation of the spinal nerves following a prolonged compression, leading to irritation and swelling. This irritation usually occurs at the level of the root of the lumbar nerves.
An epidural works by delivering corticosteroids directly to this painful area. The injection, carrying potent anti-inflammatories, causes reduction in the inflammation that may be a causative factor of pain.
Studies show strong correlation between the resolution of nerve root inflammation and improvement of symptoms in general.
Research shows that when used to treat acute low back pain, accompanied with sciatica, the epidural corticosteroids are more likely to completely relieve pain after 3 months than do the local anesthesia injections under the skin.
Epidurals are also considered to have better effects if the problem is triggered by lumbar disc herniations. Results are better if fluoroscopy is used to guide the injection directly to the affected nerve roots.
A study reported by McQuay and Moore states that patients normally experienced a 75% short-term pain relief with epidural steroids as against a low of 50% long-term pain relief. However, epidurals were shown to have the same effect as placebo in treating chronic back pain.
Overall, ESIs, administered along with analgesics and physical therapy are known to have brought relief to a vast number of patients with back pain, providing them with a highly effective alternative to surgery.