UNDERSTANDING BACK TROUBLE: FURTHER TESTS-MYELOGRAPHY OR RADICULOGRAPHY
Depending on what has been learned so far, and on your symptoms, further tests may be carried out. In most cases, however, it is unlikely that they will have to be done; at any rate, not all of them.
Most surgeons insist on some such investigation before deciding whether to recommend an operation. Some of these tests may require you to be admitted to hospital for a couple of days.
Myelography or radiculography-This is a method of making the dural tube show up in X-rays, by injecting a contrast medium – a radio-opaque liquid – into the cerebrospinal fluid around the spinal cord. This is done under local anaesthesia, by lumbar puncture, the
needle being inserted through the skin of the back between a pair of vertebrae at the appropriate level. It is not a pleasant experience and is usually only recommended if surgery is thought likely.
Using an image-intensifying screen, the radiologist can see whether the spinal canal is abnormally narrow and whether anything is obstructing it – such as the bulge of a prolapsed disc, or a degenerated joint. These show up as an indentation on the dural tube, or an obliteration of part of a dural root sleeve. In rare cases, back pain may be caused by a tumour on the spinal cord, and this, too, would be shown up by myelography. As a matter of routine, a sample of the cerebrospinal fluid is taken for laboratory testing.
The lumbar puncture is done while you lie on a table which can be raised to the vertical, so that the radiologist can observe the movement of the contrast medium in the dural tube as you are tilted up and down. The table may also tilt sideways, or the apparatus rotate in relation to the table, so that the radiologist can view the spine from different angles. He will probably take still radiographs to record the significant findings. Most of the time, however, he will be studying the picture on a television monitor which you may be able to see, too.
When the myelography is finished, you may be sent to a ward, with instructions to rest quietly for up to 24 hours and may be warned of the possibility of getting severe headache or nausea for a while, as an after-effect. Myelography is, to say the least, uncomfortable. Nowadays, a
water-based contrast medium is used. This is soon eliminated by the body, and does not usually cause irritation in the tissues of the spine.
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