Diagnosis - other tests
Other tests used in diagnosis
A variety of other tests may be used to find out more about a brain tumour, such as:
Lumbar puncture
This test is only used for some types of brain tumour. It involves getting a sample of cerebrospinal fluid (the fluid which is found in the spaces inside the brain) and examining it for cancer cells.
Doctors can't always do this test on people with brain tumours because if the pressure inside the brain and spinal canal (the intracranial pressure) is too high, it would be too risky to carry out.
To have the test, you lie on the examination couch on your side with your knees drawn up to your chest. This curves your back and makes it easier for the doctor to get the needle into the right place. The doctor will numb the area with a little local anaesthetic. Then, the doctor will slowly and carefully push the needle into your spine. Once the tip of the needle is in the right place, the doctor pulls the needle out, leaving a tube (cannula) in place.
A collecting bottle is placed under this tube and some of the cerebrospinal fluid drips out. The doctor sends this fluid to the lab to be looked at under a microscope.
After the lumbar puncture, you have to stay lying down for at least a couple of hours. If you get up too soon, you may get a bad headache.
Myelogram
This test looks at the spinal cord.
First you have a lumbar puncture. Then the doctor injects a dye into the space around the spinal cord: cerebrospinal fluid flows through this space, and the dye therefore spreads through this fluid.
You will then have X-rays taken. If a tumour is blocking the flow of the fluid, the dye cannot get past it, and so the position of the tumour will show up on the X-rays.
Angiogram
This test examines the blood supply to the area being scanned. Angiograms are not done as often as they once were, but they are an important test for some types of brain tumour. This is because the surgeon may need to know:
- which blood vessels are supplying the tumour
- whether the tumour is attached to any major blood vessels in the brain.
Angiograms are sometimes used when a tumour is growing very deep inside the brain.
For this test you will usually have to come into hospital overnight. You will need a sedative or a general anaesthetic. You have the angiogram in the X-ray department.
First, you will have a tube (catheter) put into a blood vessel in your groin. The doctor injects a dye into the tube. After a minute or so, the dye will have circulated through your blood vessels into your brain.
The dye shows up on an X-ray. Your surgeon will look at your brain on an X-ray screen to see exactly how near the tumour is to the blood vessel.
Depending on the type of brain tumour you have, your surgeon may then inject something to block the blood vessels that carry blood to the tumour. This will help to shrink the tumour before you have surgery to remove it. This procedure is called embolisation or interventional angiography.
There is a small risk of a stroke from this procedure. But the risk is usually small compared to the benefit of treating the tumour.
Before you have this treatment, your specialist will explain all this to you and you will be able to ask questions or talk through any worries that you have.
Electroencephalogram (EEG)
This is a recording of the electrical activity within the brain.
During the test, wires connected to small plastic discs are attached to your head using a special gel. The activity in your brain (nerve impulses) is recorded and then printed out on paper. The test takes about an hour. It is safe and completely painless. Your hair does not need to be cut, and the gel will wash out easily afterwards.
