The perils of over-imaging your spine: when do you really need an X-Ray, CT scan or MRI?

Back pain has a habit of making us fear the worst. An abrupt spasm after hoisting something heavy, pain radiating down the leg or an ache that won’t go away can lead quickly to one question: should I get an MRI?

The short answer is: perhaps not.

In reality, most cases of acute low back pain get better without an MRI, a CT scan or even an X-ray. Routine imaging for uncomplicated low back pain, especially in the absence of any warning signs of a serious underlying condition is not recommended by international guidelines.

When an MRI doesn’t help

An MRI is a great diagnostic tool, but more imaging isn’t necessarily better care. Spine scans can show us age-related changes such as disc bulges, disc degeneration and arthritic changes that may have nothing to do with the pain that a person is experiencing.

Sometimes these incidental findings can cause unnecessary anxiety in patients who may believe that their spine is ‘damaged’ when in fact, the finding may simply be a normal part of ageing. Imaging that does not change treatment can therefore add cost, worry and sometimes unnecessary interventions.

For many people with a simple episode of back pain, the first step is careful clinical evaluation, appropriate pain management, staying as active as possible and a structured rehabilitation or physiotherapy programme when required. Most simple cases will clear up in a few weeks.

When imaging is needed

Imaging is important when the history or examination suggests a particular structural or serious underlying problem.

A significant trauma, particularly in older patients or patients with osteoporosis where a fracture needs to be excluded, is one important situation. Imaging may also be indicated if there is a history of cancer, unexplained weight loss, fever or other signs that cause the doctor concern and need checking for an infection or malignancy.

Another significant sign is progressive neurological weakness. If you have ongoing numbness or weakness in the leg or increasing difficulty walking, or signs of significant nerve compression, you should be seen promptly.

A medical emergency is suspected if there is back pain with new problems in controlling the bladder or bowel, or numbness around the groin and inner thighs. These symptoms may be a sign of a serious condition called cauda equina syndrome, which is compression of the nerves at the bottom of the spinal canal. Urgent imaging, usually an MRI, is important in these cases.

Imaging may also be indicated if the pain persists or worsens progressively after an adequate period of conservative treatment, especially if the results will affect decisions regarding an injection, surgery or other specific intervention. The question is not just, “How long have you had back pain?” but “Is this scan going to change what we do next?”

Right scan, right time

It is also important to remember that an MRI is not the only imaging modality. If you think there is a fracture or alignment issue, X-rays may be useful. CT scans might provide better detail of bone in some situations compared to traditional X-rays. An MRI is especially helpful for examining discs, nerves, the spinal cord, infections and some tumours.

The decision must therefore be taken after a complete clinical examination, and not before.

Back pain should be taken seriously. But taking it seriously does not always mean rushing for an MRI. In most cases, a complete history and physical examination will enable the clinician to decide if imaging is really needed. When red flags are visible, timely scans can be critical. Avoidance of unnecessary imaging is just as important in their absence.

The aim is not to order more scans. It is to order the right scan, for the right patient, at the right time.

(Dr. S. R. Patil, Consultant Brain and Spine Surgeon, Hosmat Hospital, Bengaluru. drsrpatilmsmch14@gmail.com)