What it is treating

Radicular pain is driven by inflammation around a nerve root as much as by mechanical contact with it. Extruded disc material is chemically irritating in its own right, and the inflammatory response it provokes is what sensitizes the root. That inflammatory component is what steroid addresses.

Which explains both the strength and the limit. Reduce the inflammation and the pain frequently falls substantially, letting you move, sleep and let the natural history proceed — and a large proportion of disc herniations do resorb on their own given that time. The steroid did not resorb it. It made the interval survivable.

The route matters more than most people are told

All of them are done under fluoroscopic guidance with contrast confirming spread before medication is given. A blind epidural in the lumbar spine misses its target often enough that image guidance is not a refinement, it is the standard.

When it is worth doing

• Radicular pain with a matching examination and, where imaged, a matching level. Radiculopathy.
• Severe enough to prevent sleep, work or movement — because the cost of the untreated interval is what the injection is being weighed against.
• As a level-confirming test where the imaging shows more than one candidate.
• In stenosis, to reduce the inflammatory component around compressed roots and open a window for the conditioning work. It does not widen the canal. Stenosis.

When it is not

Axial low back pain without a radicular component is the big one. If your pain is across the back and does not travel in a nerve distribution, an epidural is aimed at a structure that is not generating your symptoms — and the likely candidates are the facet joints or the sacroiliac joint, which need different tests entirely. A large share of the epidurals that disappoint were given for this.

It is also not the answer to a progressive neurological deficit. Weakness that is worsening is a surgical conversation, and using an injection to buy time there costs function that does not return.

On steroid, honestly

Corticosteroid is a systemic drug given locally, and it does not stay entirely local. In a population where most patients are metabolically unwell, that is worth stating rather than glossing over: a steroid injection raises blood glucose for days, and in a diabetic patient that can be substantial. If you are diabetic, monitor closely for about a week and tell us in advance so the dose and the plan account for it.

Repeated steroid exposure over time also has effects on bone density and on the adrenal axis. This is one of the reasons this practice does not run standing courses of three. There is no magic in a series, quantity is a clinical decision measured against what the previous injection achieved, and where a durable non-steroid answer exists — as it does for confirmed facet pain, in radiofrequency neurotomy — we would rather go there.

The wider point is the one this practice keeps returning to. Injecting an anti-inflammatory into a body that is generating inflammation systemically is asking a local intervention to hold against a whole-body process. Insulin resistance and metabolic inflammation raise the baseline the local response starts from, impair the microcirculation the nerve root depends on, and slow the resorption that the window is supposed to permit. Which is why bloodwork is part of this consultation and not a separate program you get sold afterward.

What happens on the day

Common questions

How long does it take to work?

Local anesthetic gives relief within the hour and it wears off; that early window tells us the medication reached the right place. The steroid effect typically builds over two to seven days and is assessed at two weeks.

That is the subject of A joint this deep cannot be injected by feel. If it was not imaged, it was not necessarily treated..

How long does it last?

Highly variable — weeks to many months. In a herniation that resorbs during the window, the relief can simply persist because the problem resolved underneath it.

The detail is in The only test that finds facet pain. There is no scan for it..

How many can I have?

There is no fixed number and no pre-booked course here. Each one is a decision made against what the last one achieved, weighed against the cumulative effects of steroid.

See You can draw the line where it goes. That line is most of the diagnosis..

Does it hurt?

The skin anesthetic stings. Most people describe pressure after that. Some feel a brief reproduction of their leg pain as the needle nears the root, which is uncomfortable and informative.

That is the subject of A joint this deep cannot be injected by feel. If it was not imaged, it was not necessarily treated..

Will it interfere with surgery later?

Generally no, and there is usually a recommended interval between an injection and an operation at the same site. If surgery is being planned, tell us and we will coordinate the timing.

See You can draw the line where it goes. That line is most of the diagnosis..

Related reading

• Lumbar radiculopathy
• Is it actually the disc?
• Spinal stenosis
• Sciatica, and what impersonates it
• Before you agree to the operation