An ESI, or epidural steroid injection, is a common pain management procedure that delivers anti-inflammatory medication directly into the epidural space surrounding the spinal nerves. It’s primarily used to treat radiating pain caused by compressed or irritated nerve roots in the spine, most often from herniated discs or spinal stenosis. If your doctor has recommended one, or you’re researching options for back or leg pain, here’s what you need to know.
How an ESI Works
The epidural space is a fat-filled area between the bones of your spine and the protective membrane covering your spinal cord. When a disc herniates, bone spurs develop, or the spinal canal narrows, nearby nerve roots can get pinched and inflamed. That inflammation is what causes the shooting, radiating pain many people describe as sciatica, where pain travels from the lower back down through the buttocks and into one or both legs.
An ESI places a corticosteroid (a powerful anti-inflammatory) right next to those irritated nerves. The steroid calms the inflammation, which reduces swelling around the nerve and decreases pain signals. Most injections also include a local anesthetic that provides immediate but temporary numbness, giving you a brief window of relief while the steroid takes effect over the following days.
Conditions Treated With ESIs
The most common reason for an ESI is a herniated disc pressing on a spinal nerve root. This is the condition with the strongest evidence supporting the injection’s effectiveness. Spinal stenosis, where the spinal canal or the openings where nerves exit the spine gradually narrow, is the second most common indication, though patients with stenosis generally respond less well than those with disc herniations.
ESIs are also used for a broader range of spinal problems, including:
- Bone spurs pressing on nerve roots
- Spondylolisthesis, where one vertebra slips forward over the one below it
- Post-surgical pain that persists after a spinal procedure
- Compression fractures causing nerve irritation
- Scoliosis that irritates nearby nerve roots
In all of these cases, the common thread is nerve root irritation and inflammation. If your pain stays localized to your back without radiating into your arms or legs, an ESI may be less likely to help.
Three Approaches to the Injection
There are three ways a doctor can access the epidural space, and the choice depends on where your pain originates and your specific anatomy.
An interlaminar injection goes in between the bony plates (laminae) on the back of the spine. It’s the most traditional approach and delivers medication broadly across the epidural space. A transforaminal injection targets a specific nerve root by entering through the foramen, the small opening where the nerve exits the spine. This approach puts the steroid closer to the source of irritation. A caudal injection enters through the sacral opening at the base of the spine and is sometimes preferred for patients who have had previous spinal surgery.
Research comparing all three approaches in trials of 120 patients each found no clear superiority of one method over the others for overall pain relief. Interlaminar injections did show improvement in a slightly higher proportion of patients, and had a lower rate of non-responders when steroid was included.
What the Procedure Feels Like
The entire procedure takes about 10 to 20 minutes. You’ll lie face down on a table while the doctor uses fluoroscopy, a type of live X-ray, to guide the needle to the correct spot. The skin is numbed first with a local anesthetic, so the main sensation most people describe is pressure rather than sharp pain as the needle advances.
Once the needle is in position, contrast dye is injected to confirm proper placement before the steroid mixture is delivered. You’ll be monitored briefly afterward and can typically go home the same day. The numbing medication wears off within a few hours, and it’s normal for pain to temporarily return, or even feel slightly worse, before the steroid kicks in over the next several days.
Recovery After an ESI
Most people can return to their daily routine within a day or two. You may want to take it easy for the first 24 to 48 hours, avoiding strenuous activity. Showers are generally fine the same day if your doctor approves, but baths are typically off limits for the first 24 hours. Some soreness at the injection site is common and usually resolves quickly.
How Well ESIs Work
Effectiveness varies depending on the underlying condition. For herniated discs, studies show encouraging numbers. One trial found that 84% of patients receiving transforaminal ESIs reported success at about 1.4 years, compared to 48% in the control group. Another study showed 70% of patients in the steroid group improved at the two-year mark, versus 60% in the control group receiving only local anesthetic. Patients commonly report greater than 50% improvement in radiating pain, disability scores, and even sleep quality within two weeks of the injection.
For spinal stenosis, the results are less consistent. Patients with narrowing of the spinal canal tend to have weaker responses to ESIs than those with disc problems. A systematic review of 70 studies on lumbar ESIs rated the evidence as good for disc herniations, fair for spinal stenosis, and poor for failed back surgery syndrome.
Pain relief duration varies widely. Some patients experience relief lasting six months or longer, while others see benefits for only a few weeks. The injection is not a cure. It reduces inflammation to create a window of reduced pain, which ideally allows you to participate more fully in physical therapy and rehabilitation.
How Many ESIs You Can Have
There are limits on how often you can receive these injections because repeated steroid exposure carries cumulative risks. Medicare guidelines cap ESIs at 4 sessions per spinal region in a rolling 12-month period. Broader guidance suggests no more than 6 epidural injections total across all spinal regions in a 12-month period. Your doctor will typically start with one injection and assess your response before scheduling additional ones.
Risks and Side Effects
Most side effects are mild and temporary. A “steroid flush,” where your face or chest feels warm and flushed for a day or two, is relatively common. Temporary increases in blood sugar can occur, which is worth monitoring if you have diabetes. Some people experience a mild headache or increased pain at the injection site for a few days.
Serious complications are rare but real. The FDA has issued a safety communication noting that epidural corticosteroid injections have, in rare cases, been associated with severe neurological events including stroke, spinal cord injury, paralysis, vision loss, and death. These events are most often linked to injections in the cervical (neck) region and to the use of particulate steroids, which form tiny crystals that can potentially block blood flow to delicate neural tissue. Non-particulate formulations like dexamethasone are water-soluble and considered lower risk for these complications.
If you experience sudden vision changes, severe headache, facial weakness, numbness or tingling in your limbs, or seizures after an ESI, seek emergency medical attention immediately.