To scan or not to scan…?

A question I’m often asked by patients is:

“Should I get an MRI scan to find out what is going on?”

Most of the time I end up explaining that a scan is not needed as they rarely shows ‘what’s going on’ and there is evidence to suggest that getting an MRI scan can lead to worse outcomes for the patient.

This may seem counter-intuitive especially as imaging is becoming more advanced and easily available. However, an MRI scan is just a series of photos of the inside body, a black and white snapshot of the physical state of the tissues. It is not the magic diagnostic tool some people would like to believe!

It’s a bit like trying to figure out what’s wrong with your computer by taking the case off and photographing the inside. That photo will tell you about the physical state of the computer and you might see some scratches, dust or even cracks, but you’ve no way of knowing how long they’ve been there or how relevant they are to the problem with the computer. That photo cannot tell us how well all the systems are working or if all the software is running smoothly. If there is a large crack in the hard drive or something obviously out of place then the photo can help identify that, but otherwise it’s not really much use.

Computer
How useful is this photo in helping fix the computer? (Remember human bodies are far more complex than computers!)

The story is much the same with MRI scans. They cannot tell us how the nervous system and muscles are working, how those body parts look when you’re moving or anything about the complex physiology that leads to pain.  However, you will definitely find changes and ‘abnormalities’ on a scan of any body part but large scale studies in people without pain have shown that these findings are very common:

Did you know that over 50% of people in their 30s without back pain have ‘disc degeneration’ on MRI scan? (1).

Or that 88% of people aged 51 – 89 had some sort of ‘pathology’ found on an MRI scan of their knee yet reported no knee pain at all? (2)

This leads us to the biggest danger of scans: they lead to the over-medicalisation of normal ageing processes and people becoming scared that they are ‘damaged’ or ‘broken’. A study in the USA showed that people who had an MRI soon after the onset of back pain had worse outcomes and higher levels of reported disability than similar people with back pain who did not have an MRI (3).

This is not to say scans are not useful, just that we need to carefully consider how and when we use them. Most importantly the results need to be interpreted in the context of the normal findings across the population.

Scans are very good for ruling out pain caused by serious pathology such as fracture, infection or cancers. However these are very rare and usually present with other signs & symptoms that would lead to a scan being ordered.

So, if you’re thinking of getting a scan (or have already had one!) to ‘find out what’s going on’ remember that what we see on the scans doesn’t always match up with the symptoms, many of the findings may also be found in pain-free people and pain is rarely fully explained by scan findings in the absence of serious pathology.

Your body is constantly adapting and ‘abnormal findings’ on a scan may in fact be evidence of your body adapting to the demands you place on it!