Manage Your Pain: Practical and Positive Ways of Adapting to Chronic Pain - Michael K. Nicholas, Allan Molloy, Lee Beeston, Lois Tonkin (2012)

Chapter 4. What X-rays, CT and MRI Scans Tell Us

The word ‘imaging’ is a term used to describe tests that provide pictures or scans of parts of the body. As these tests have become more advanced they have allowed us to look inside the body without the need for an operation. Where the cause of pain might once have been put down to a condition such as ‘lumbago’ or a ‘strain’, new tests are helping doctors to work out exactly what is wrong. Scans are particularly helpful in excluding worrying conditions such as cancer and infections.

The scans have to be interpreted very carefully by experts taking into account the problem that the patient has. Because the techniques are very sensitive, findings on the scan that seem to be abnormal and of concern may in fact be normal for that person or a person’s age group. This is particularly true as we get older and wear and tear inevitably occurs. Even in the younger age group a disc bulge may be found on a scan of a person with back pain and it might be assumed that this was the cause of the pain. Recent scientific studies have found similar disc bulges in people without pain, however. Also, conditions where the disc is damaged such as an internal disc disruption or an annular tear, are often painful but are also seen on scans in people who are not reporting pain. Damage to intervertebral discs can certainly be the cause of back pain but this diagnosis has to be made with caution before treatment is recommended.

It is important to remember that scans do not show pain. At one extreme a person may have severe degeneration (wear and tear) of the spine that shows up on an X-ray but no pain, while someone who is very disabled by back pain may have little to find on any tests.

Geoff was a senior radiologist and had worked as a hospital specialist for many years. To liven up a teaching session with a group of doctors, he had an MRI scan performed on himself and presented this to the audience. He made up a history of someone who was unable to work because of pain. The scan showed marked wear and tear and surgery was considered an option. The surgeons were very surprised when Geoff told them the scan was of his back and that although he had some pain he worked long hours and was physically active in his garden at the weekends.

Scans are important but provide only part of the picture. It is necessary first of all to assess the person and their problem by talking to the person, finding out about the nature of their problem, how it started and then undertaking a thorough examination.

Accepting negative scans in a positive way

Scans play an important part in trying to pinpoint where the pain is coming from but often no abnormality shows up. This can be a very disappointing result as both you and your doctor know that to cure the pain you need to know what is causing it. The doctor may present the scan as being negative and apologise for that by saying, ‘I am sorry that the scans are negative, I cannot find where the pain is coming from’.

A more helpful way of looking at it, however, is to think of the scans as ‘positive’ if they do not show any abnormality. That means that you should be reassured that you are okay and that you are unlikely to have a serious problem such as a fracture, an infection or cancer.

It is true that doctors are getting better at identifying the cause of the pain but the cause of every pain that people experience is not yet known. For example, in many cases of back pain, doctors can’t be sure where the pain is coming from. And although the doctor may be absolutely sure where the pain is coming from, there is no certainty that this pain can be fixed.

Current imaging techniques

X-rays

The discovery of X-rays and their use in medicine was a significant breakthrough. X-rays are absorbed by different parts of the body and produce ‘shadows’ on the film. Bone absorbs X-rays and appears white on the film, whereas soft tissue appear dark. Fractures are most frequently diagnosed with X-rays but they do not help with seeing detail such as a disc pressing on a nerve or on the spinal cord. And X-rays do not show pain.

CT scans

For this type of scan the patient is placed in the CT (computerised axial tomography) tube. X-rays are passed through the body and picked up on the other side. The way in which the X-rays have been ‘changed’ by the body is fed into a computer that makes a series of complex calculations. The result is a picture of the body in cross-section. Bony problems in particular are sensitive to this technique.

MRI scans

The MRI (magnetic resonance imaging) scanner consists of a large magnet. This interacts with particular properties of your body to produce signals that are processed by a computer to form detailed images. The scanner allows us to look inside any part of the body. It is particularly useful for ‘seeing’ the spinal cord and nerve roots, without having to operate. The technique also provides an idea of the chemical make-up of the disc and allows us to recognise conditions like disc degeneration at an early stage. A clear advantage over CT scanning is that as X-rays are not used there is no risk from radiation. 

Bone scans

In this type of scan tiny amounts of radioactive material are injected into the body. Areas where there is damaged tissue, an injury or an infection accumulate more of the material and can be detected by a special scanner. This is a very sensitive method of pinpointing problem areas. At times, these scans will reveal things that don’t show up with other methods. They are not always necessary, however, and their use must be governed by the clinical judgment of your doctor.

Myelography

This refers to the injection of a special dye into the fluid around the spinal cord. The dye enables the structures inside the spinal canal to be seen on an X-ray or CT scanner. This test does carry some risks and in many ways it has been replaced by the advent of MRIs.