“I’ve been suffering from low back pain for a few months now, and an MRI scan shows that I’ve got a bulging disc. I’ve been told that it won’t go back in by itself, so I should try to get surgery. Is this true?”
Let’s start with a bit of heavily over-simplified anatomy. Your spine is a stack of bones (vertebrae) sitting on top of each other, and a spinal disc lies in between each pair of vertebrae. These discs are a little bit like jelly donuts; they have a fibrous outer layer, with some squishy stuff in the middle. If you squeeze the donut, you might start to get some damage to the bit on the outside – it might start to tear or bulge outwards; take it far enough, and eventually the jam might start to leak out.

As with our donut, there are a variety of different kinds of damage that can happen to a spinal disc. There may just be damage to the outer layers of the disc, causing some back pain; but in other cases the disc can start to bulge outwards into the spinal canal. If this bulge becomes large enough, then it may put pressure on the spinal nerves. In the worst cases the jelly-like nucleus starts to protrude from the disc; this is known as a herniated disc (sometimes called a slipped disc). Pressure from the disc on the nerve, or inflammation around the nerve root, can cause pain right down the leg, numbness or pins and needles, and sometimes muscle weakness.

This also illustrates an important point about disc injuries; once the jelly is out of the donut, there’s no way to “just pop it back in again” (If someone has told you they can do this, they are either ethically challenged or badly informed. Either way, you should avoid seeing them.)

So, surgery it is then…?

Not so fast. First of all, depending on how you define it, disc degeneration and disc bulges are actually very common. So common, in fact, that if you take MRIs of enough people, you’ll find that a sizeable proportion of the population show signs of some kind of disc damage without having any symptoms of back pain at all. So you shouldn’t be immediately alarmed if a scan result suggests that your discs have a bit of wear and tear. It may even be that the findings on the MRI scan are not related to your back pain; in some cases the results can be very poorly correlated with clinical symptoms.

Disc injuries also recover well by themselves in most cases. Hold on a second – didn’t we just say that you can’t put the jelly back in the donut? That’s true, but it is thought that fragments of the disc can be cleared up by the immune system over time, with the result that the herniated material will reduce in size. Symptoms will also improve in most cases, and this is often true even with very large disc herniations. Overall, it’s thought that 70-95 percent of these patients will recover within 12 months with no major intervention.

It’s important to remember that surgery comes with some risks attached, and while it often gives relief of nerve symptoms (such as leg pain), it’s generally considered to be less effective when back pain is the main symptom. In fact, when lumbar fusion operations (a common type of lower back surgery) are performed for chronic lower back pain, the outcomes are no better than those achieved by conservative care. In a few cases, it may even make the pain worse. Nowadays, patients are usually advised to try conservative treatment first, before considering surgery.

Does that mean surgery is a bad idea?

On the other side of the coin, you may have read articles that suggest that spinal surgery is “useless,” giving the impression that these operations are advocated by surgeons who are deluded at best and fraudsters at worst. Is that true? Before taking this sort of headline at face value, it’s important to do some digging and look at the evidence on which it’s based. Often the studies used to reach that conclusion are based on one particular subgroup of patients (in this case, patients suffering from back pain, rather than leg pain). Even when a study concludes that two different interventions have similar outcomes, it doesn’t necessarily mean that the two interventions are equally effective for every patient. Suppose a survey showed that on average, people found loud parties and long walks in the country equally pleasurable activities; would you conclude that your elderly and introverted aunt would enjoy accompanying you to a nightclub as much as her usual Sunday afternoon stroll? (Of course, the tricky bit lies in figuring out which patients will benefit most from which intervention – and in practice this is a difficult problem).

It’s always important to get advice about your individual case before making a decision. There are some situations in which a surgeon would be justified in operating sooner rather than later; in particular if the nerve symptoms are severe, and especially if they affect muscle function. If a nerve is compressed for a long period of time, it may not recover well even when the compression is removed.

The most extreme case of this is a very rare condition called cauda equine syndrome, where in addition to severe pain there is numbness around the buttock and genital area (called “saddle anaesthesia,” because it’s the area that would be in contact with a saddle if you were riding a horse), leg weakness and bowel or bladder dysfunction. If any of these symptoms are present, then it should be assessed urgently; delay may increase the chance of permanent damage to the nerves.

The verdict: not necessarily

A bulging or herniated disc on its own isn’t a sign that you’ll need surgery, and most people with that condition won’t. Whether it’s something that should be considered will depend on the symptoms you’re getting, the exact nature of the injury, how long you’ve had the problem and what else has already been tried. Consult a spinal specialist for individual advice on your case, and if you’re not completely confident in the answer then don’t be afraid to seek out a second opinion.