¿Necesito una resonancia magnética para mi dolor de espalda?

If you’ve had weeks of persistent back or spine pain coupled with vague advice to ‘rest and see’ or anxiety over what might be wrong, you’re probably wondering what happens next. Do you need a scan? If so, which one, and how do you go about getting one? Should you wait for an NHS appointment, or should you opt for a private back MRI scan?

Here’s everything you need to know.

What is an MRI scan and how does it work?

resonancia magnética (RM) stands for magnetic resonance imaging, and an MRI uses powerful magnetic fields and radio waves to create detailed images of the inside of the body. An MRI scanner is a large, doughnut-shaped machine, and during the scan, patients lie flat on a table that slowly moves into the scanner.

Once in the machine, the magnetic field is switched on and off, and as it does so, hydrogen atoms in the body temporarily misalign. This creates energy that computers detect and turn into an image. Different tissue types produce distinct levels of energy, and the resulting images clearly show the bones, soft tissues, organs, and fluids. Consultant radiologists can then differentiate healthy from unhealthy tissue on these images and identify areas of concern.

Unlike CTs and X–rays, MRIs don’t use radiation, and you won't feel anything as the scan takes place. However, due to the closed-in nature of the scanning machine and the loud noise from the magnets, they may be unsuitable for people with claustrophobia. MRIs take 30-90 minutes, and you’ll be required to remain still throughout.

If you struggle to remain still for any length of time, you may find an MRI difficult. Patients with magnetic metal implants, plates, and screws cannot undergo MRI scans because of the dangers posed by the magnets used in the procedure.

What can an MRI actually show in your back?

Any part of the spine can be scanned, but the most common type of back scan is a lumbar spine MRI that visualises the lower back.

MRIs cannot always detect the source of pain and discomfort, and they can sometimes be inconclusive. In these cases, another scan, such as a CT, might be recommended. MRIs can also increase the risk of incidental findings, unexpected, symptomless findings that are usually harmless, but that can lead to unnecessary treatment.

MRI vs. X-rays vs. CT: which scan is right for back pain?

Doctors use different scans to diagnose the cause of back pain: MRIs, CTs, and X-rays.

resonancia magnética

MRI is the gold standard scan for imaging the back and spine. It creates high-quality images of soft tissues, is non-invasive, doesn’t use radiation, and is safe for most people.

MRI scans are used to diagnose conditions affecting the vertebrae, discs, spinal cord, and nerves, including fractures, spinal cord abnormalities, slipped discs, narrowing of the spinal canal, nerve pain, muscular damage, infections, and cáncer.

However, they can take an hour or longer and aren’t suitable if you have certain metallic implants, stents, or plates and may be difficult if you have claustrophobia or struggle to remain still for any length of time.

tomografía computarizada

CT scans are quick and take just a few minutes, and are often used in emergencies to assess spinal damage following accidents and collisions.

They can detect minute fractures, but as they use radiation, they’re less likely to be used to diagnose non-emergency or soft tissue injuries. However, if you’re unsuitable for an MRI scan, your doctor may suggest you have a CT scan instead.

radiografía

rayos X are sometimes used as a ‘first-line’ scan, as they’re quick and useful for detecting fractures, breaks, and degeneration.

They can also show artritis, inflammation, and tumours and can be used to diagnose abnormalities in the curvature of the spine. However, they use radiation, and they’re not reliable for diagnosing problems with the discs, spinal cord, or nerves.

When it comes to CT vs MRI vs X-ray for back pain, MRI remains the gold standard if back pain needs investigating.

When do doctors recommend an MRI for back pain?

Most back pain doesn’t warrant an immediate investigation, and knowing what does and when to get a back scan can be difficult.

If you have back pain that has persisted for six weeks or more, or hasn’t responded to conservative treatments such as rest, over-the-counter pain relief, or physiotherapy, a back pain MRI scan could benefit you.

You can also benefit from an MRI if you have a condition such as ciática, osteoporosis, or arthritis that needs monitoring or is getting worse, your doctor suspects you have a condition affecting your spine or spinal cord, you’ve previously had cancer, you’re going through cancer treatment or you have a family history of cancer.

When an MRI probably won’t change anything

If you’ve had back pain for less than six weeks and you don’t have any red flags that require urgent diagnostic testing - see below - having an MRI scan is unlikely to be of any benefit. Having an unnecessary scan may cause anxiety due to the risk of incidental findings and may lead to over-treatment.

Red flags: symptoms that mean you should act now

Certain symptoms should be investigated urgently.

If you have any of these symptoms, speak to your GP or seek urgent medical attention. The sooner anything serious is discovered, the sooner treatment can start.

How to get an MRI: NHS vs private scans

If you have back pain that’s persistent and not getting better, your GP may refer you for a diagnostic MRI scan. NHS waiting times for diagnostics vary by region in the UK, but they can be long, and you may find yourself waiting several weeks or months. Waiting for a scan delays your diagnosis and treatment.

Private scans offer a fast alternative to NHS waiting lists. You can book a private MRI scan without a GP referral through Scan.com, and you’ll have your scan images and radiologist’s report within a few days.

Understanding MRI results

Once you’ve had your scan, the images are sent to a consultant radiologist for interpretation. They’ll write a report that includes a diagnosis, if appropriate, and details of any suggested further investigations.

It’s advised that you take your MRI images and report to your GP or specialist to discuss your next steps.

What comes next: treatment options after diagnosis

Most back pain eases with treatment, and once you have a diagnosis, knowing what treatment will benefit you the most is easier. Treatment options range from physiotherapy and pain management to interventional injections of nerve blockers. Surgical options can be offered, but they are typically used as a last resort when other options haven’t been successful.