When you first visit your GP with back pain, you’ll be asked how long you’ve had the pain, when it started, what provokes it and what helps relieve it. Then a physical examination can help your GP to rule out a few things that might be causing the pain.
Accurate diagnosis is important because if your back pain is caused by damage to a muscle or ligament, then it’s likely it will eventually heal itself. However, other back conditions don’t improve by themselves and need further treatment.
Sometimes the cause of back or neck pain is clear — a fracture, a compressed disc, a pinched nerve for example. But if your doctor isn’t sure what’s causing your back pain, or if they suspect something serious could be behind it, they may send you to have one or more of these diagnostic procedures to help narrow down the cause.
These show the bony structures of your spine and can be good for ruling out scoliosis, instability, tumours, fractures, osteoporosis and osteoarthritis. Because X-rays don’t show intervertebral discs or nerves, they won’t be helpful if your problem is due to a herniated disc or a pinched nerve. X-rays do use radiation, but the amount of radiation used for spine imaging is relatively low. If you’re pregnant, however, you should avoid having an X-ray.
A CT scan
A CT scan (computerised tomography) is a type of X-ray that provides cross section views through your body. A CT scan can show a large herniated disc or spinal stenosis. It doesn’t show nerves.
To view nerves as well, the radiologist can inject an opaque dye that is picked up by X-rays into the area around the nerves. This is called a CT with myelogram. A CT with myelogram is rarely done anymore. It‘s largely superseded by magnetic resonance imaging (MRI) which is better at showing up disc prolapse and possible nerve compression.
CT scans use more radiation than ordinary X-rays, and also shouldn’t be had if you’re pregnant.
Back pain from damage to the nerves can be caused either by bony or disc degeneration or compression. An EMG or electromyogram is useful when your doctor wants to distinguish these two conditions. During the procedure, small needles are put into your muscles, which can be briefly painful. An EMG is normally performed by a neurologist.
Somatosensory evoked potentials
This non-invasive test performed by a neurologist, uses small electric pulses to show how quickly signals from your spine are reaching your brain. It’s sometimes used for neck or thoracic pain, but not normally for lumbar (low back) pain. It’s not a painful procedure, although you’ll feel a slight buzzing sensation from the electric pulses. It can be a useful test to work out if nerve pain is really coming from your back or if it’s originating in your brain.
If your doctor suspects that your pain is coming from a herniated disc, they may refer you for a discogram. During the procedure, a radiologist injects the affected disc with dye that shows up on an X-ray. If the injection provokes your pain, then it’s likely that your pain is being caused by that disc. This is known as a discal block. Often more than one disc will be injected, and the radiologist then takes CT images of the discs. This is known as provocative discography. This is a painful procedure but it’s useful if you’re contemplating disc surgery because it can help to ensure that the surgeon operates on the correct disc. This test is usually performed when your doctor believes that surgery is imminent. It helps to isolate which level(s) of your spine needs to be operated on.
A bone scan
A bone scan can be used to rule out a tumour, infection or hidden fracture as the cause of your pain. If you have osteoporosis, a bone scan can grade its severity but you’ll need a bone mineral density scan as well. During a bone scan, a radiologist injects a radioactive marker into a vein and, after about 3 hours it will be concentrated in any areas of your spine where there’s a high turnover of bone. A scan is then performed to see where the marker has concentrated. Often a CT scan is done at the same time and the images of each test “fused” together. This is called a CT/spectroscopy. You shouldn’t have a bone scan if you’re pregnant.
A spine surgeon or rheumatologist may require further details of your injured disc or nerves, especially if you have leg pain (sciatica) that could be radiating from a herniated disc. An MRI (magnetic resonance image) can be a good way to diagnose which disc is causing the pain. If you’re considering surgery, an MRI is the most useful test for locating the problem. Because MRIs use powerful magnets you may not be able to have one if you have a cardiac pacemaker or other metal in your body. Because an MRI doesn’t use X-ray radiation, it may be preferable if you’re pregnant.
MRI imaging is provided at radiology clinics and can be expensive. Depending on your condition, MRIs may not be claimable on Medicare when they’re ordered by your GP. You may get a better rebate with a specialist referral but the cost in seeing the specialist may offset that saving.