Epidural Steroid Injection

What is it?

An epidural steroid injection delivers a corticosteroid (an anti-inflammatory medicine related to cortisone), usually together with a local anaesthetic, into the epidural space. This is a thin space just outside the membrane (the dura) that surrounds the spinal cord and nerve roots. The procedure is carried out under fluoroscopy (live X-ray), and contrast dye is used to confirm that the medicine spreads to the right place.

The medicine can reach this space by three routes:

• Interlaminar: the needle passes between the back parts of two vertebrae into the epidural space.
• Transforaminal: the needle is directed towards the opening where the nerve root leaves the spine (the foramen), so the medicine is delivered close to the affected root.
• Caudal: the needle enters through a natural opening near the tailbone to reach the lower back.

The route is chosen according to where the pain is, the level of the herniation and individual risks. In the neck, the choice of technique needs particular care because the spinal cord and major blood vessels are close by.

When is it considered?

Epidural steroid injections are mainly used for radiculopathy, meaning radiating pain from an irritated nerve root. The most common uses are leg pain (sciatica) from a lumbar disc herniation and arm pain from a cervical disc herniation. The UK's National Institute for Health and Care Excellence (NICE) states that this injection can be considered for acute and severe sciatica.

Spinal stenosis is different. For leg pain that comes on with walking, eases with rest and often affects both legs (neurogenic claudication), the benefit is limited and NICE advises against this use. It may still be considered in selected people with one-sided nerve root pain caused by narrowing of the nerve opening.

The evidence shows that the injection usually gives a small, short-term reduction in leg pain. It is therefore not used as a stand-alone solution but to bring pain down to a level that makes exercise and physiotherapy possible. To see where it fits in a stepwise plan, see non-surgical lumbar disc treatment and non-surgical cervical disc treatment.

How does it work?

Herniated disc material does not just press on the nerve root mechanically; it also triggers inflammation and swelling around it. The corticosteroid aims to dampen this inflammatory response and so reduce irritation of the nerve root and pain. The local anaesthetic provides short-lived relief lasting a few hours.

The injection does not shrink or move the herniation. However, while the pain is calmer, the body's natural healing continues, and some herniations shrink on their own over time.

Before the procedure

Your examination and MRI findings are reviewed together to decide which level to treat and which route to use. You and your doctor will plan how to manage blood thinners before the procedure; please do not stop them on your own. If you have diabetes, your blood sugar needs to be well controlled beforehand.

Let the team know about any allergy to contrast dye or medicines, possible pregnancy, a fever or a recent infection. The aim of the procedure, its expected benefits, possible risks and the alternatives are explained before you give your consent.

What happens during the procedure?

For a lumbar injection you lie face down; for the neck, either lying face down or sitting may be used. After the skin is cleaned and numbed, the needle is advanced to the target under fluoroscopy. A small amount of contrast dye is injected to check on the images that the medicine will spread in the right space and that the needle is not in a blood vessel; the medicine is then injected slowly.

You may feel pressure, or a brief sense of fullness spreading into your leg or arm. If you feel a sharp or electric-shock-like pain, tell the team straight away. The procedure usually takes fifteen to thirty minutes.

After the procedure

You will be observed for a short time and can go home the same day. The local anaesthetic can make the leg or arm feel numb for a few hours, so do not drive on the day of the procedure. Rest on the first day, then return gradually to your usual activities from the next day.

Facial flushing, difficulty sleeping or a rise in blood sugar may occur for a few days. Seek help without delay if you develop a fever, severe or worsening back pain, new weakness or a change in bladder control, as these can be signs of a rare infection or bleeding.

When might you notice results?

You may feel relief in the first few hours because of the local anaesthetic; once this wears off, the pain may temporarily return. The corticosteroid usually starts to work within two to seven days. How long the effect lasts varies from person to person: it may last from a few weeks to a few months, and some people notice no clear benefit.

If the first injection helped and the pain later returns, a repeat may be considered. Because of the total steroid dose, frequent repeats at short intervals are not recommended. If pain and loss of function persist, other treatment options or a surgical opinion are considered. To arrange an assessment, you can request a consultation.