Spinemathema podcast · Episode 3 · About 7 minutes · 6 October 2026

Episodes are narrated using an AI model of Mr Sadek’s own voice, from scripts he has written and approved.

Read the full article with references: Microdiscectomy or Injection for Sciatica? The NERVES Trial

Transcript

Hello and welcome to the Spinemathema podcast. I’m Ahmed Sadek, a neurosurgeon, and this is a Research Spotlight, where I take one important study and go through it in plain English.

Today I want to talk about a British trial called NERVES, which stands for Nerve Root Block Versus Surgery. It was run across eleven National Health Service, or NHS, spinal units and published in the journal Lancet Rheumatology in twenty twenty one. It asked a very practical question. If you have sciatica from a slipped disc that isn’t settling, should your first step be an operation, or an injection?

A quick reminder of the problem. A slipped disc happens when part of one of the cushions between the bones of your spine bulges out and presses on a nerve. That causes sciatica, which is pain, tingling or numbness running down the leg. Most people improve with time, painkillers and keeping active. But when the leg pain doesn’t settle, there are two main options in the NHS.

The first is an operation called a microdiscectomy. The surgeon uses a microscope to remove the piece of disc pressing on the nerve. The second is a transforaminal epidural steroid injection. That’s a mouthful, so I’ll call it a nerve root injection. Under X-ray guidance, steroid and local anaesthetic are placed right next to the irritated nerve, to calm the inflammation.

Before NERVES, there wasn’t much good evidence comparing these two directly. The few earlier studies came from single hospitals. And the costs are very different. The authors noted that a microdiscectomy cost the NHS about four and a half thousand pounds, compared with about seven hundred pounds for an injection.

So here’s how the trial worked. Between twenty fifteen and twenty seventeen, just over a thousand patients were screened, and one hundred and sixty three took part. They were aged sixteen to sixty five. Their slipped disc had been confirmed on an MRI scan, that’s magnetic resonance imaging. They’d had symptoms for between six weeks and twelve months, and their leg pain hadn’t settled with at least one simpler treatment. People with significant weakness in the ankle, or signs of a surgical emergency called cauda equina syndrome, weren’t included.

A computer then randomly decided each person’s treatment. Eighty three were assigned to surgery and eighty to the injection. If the first treatment didn’t work, people were allowed to switch to the other one, which is what would happen in normal practice.

The main thing the researchers measured was a disability questionnaire called the Oswestry score. It runs from nought to one hundred, and lower is better. They measured it eighteen weeks after people joined the trial. They then followed people for about a year, looking at leg pain, back pain, side effects and costs.

So what did they find? Both groups improved, and by a similar amount. In the surgery group, the average disability score went from about forty nine down to about twenty two. In the injection group, it went from about fifty four down to about thirty. Once the researchers allowed for the different starting points, surgery came out about four points better. But that wasn’t statistically significant, and it was smaller than the ten point difference the trial was designed to detect.

Leg pain did improve somewhat more after surgery. But across the whole year, that difference wasn’t statistically significant either.

Now, safety is where the two treatments really differed. All four serious adverse events in the trial happened after surgery. These included a longer hospital stay, a repeat operation, and repair of a fluid leak around the nerves. One person out of the hundred and five who had surgery during the trial developed foot drop, which is weakness lifting the foot. There were no serious adverse events after the injection.

And then there’s cost. Over the year, surgery cost the NHS on average about six thousand seven hundred pounds per patient, compared with about four thousand four hundred pounds for the injection group. When the health economists worked it through, surgery as a first treatment was unlikely to be good value for the NHS.

One more number I find really useful for patients. Of the eighty people who were offered an injection first, forty seven, which is fifty nine percent, hadn’t needed surgery by the end of the trial.

Now let’s be fair about the limitations, because every trial has them. First, it’s a fairly small trial. Only one hundred and twenty four people had complete results at eighteen weeks. The authors themselves say that a ten point difference in favour of surgery could have been missed. Second, about a quarter of the main results were missing. Third, everyone knew which treatment they’d had, and that can colour how people fill in questionnaires. Fourth, eighteen weeks is quite early, and the trial only followed people for about a year. And fifth, there was crossover. Forty one percent of the injection group had surgery at some point. So really, that group was injection first, then surgery if needed.

So what does this mean for you? If you have sciatica from a slipped disc that has lasted up to a year, and you don’t have significant weakness or emergency symptoms, NERVES suggests a nerve root injection is a very reasonable first step. Many people improve enough to avoid an operation, and in this trial the serious complications only happened after surgery. That fits with guidance here in the UK from the National Institute for Health and Care Excellence, known as NICE, which suggests considering an epidural injection for acute and severe sciatica, and considering surgery when other treatment hasn’t helped.

But surgery still matters. The authors themselves say many patients will still need it, and leg pain tended to improve more after surgery. Other studies, such as the large American SPORT trial, have found that surgery gives faster relief of leg pain.

So, as with most things in spinal surgery, this is a decision we make together. It depends on how severe your pain is, how long it’s gone on, how it’s affecting your work and your life, and how you feel about the risks of each option.

Before I finish, one important safety message. If you develop numbness around your bottom or genitals, new trouble controlling your bladder or bowels, or leg weakness that’s getting rapidly worse, please seek urgent medical help. Those can be signs of cauda equina syndrome, which needs emergency assessment.

Thank you for listening. Please remember that this podcast is general information and not personal medical advice. If you’d like to read the full article, see the diagrams and check the references, you’ll find it all at spinemathema dot com.

This podcast is general information and is not a substitute for advice about your own situation. Please speak to your GP or specialist.