Diagnostic tests for brain tumours

Your doctor will assess your nervous system to check how different parts of your brain and body are working, including your speech, hearing, vision and movement. This is called a neurological examination and may cover:

• checking your reflexes (e.g. knee jerks)
• testing the strength in your limb muscles
• walking, to show your balance and coordination
• testing sensations (e.g. your ability to feel pinpricks)
• brain exercises, such as simple arithmetic or memory tests.

The doctor may also test eye and pupil movements, and may look into your eyes using an instrument called an ophthalmoscope. This allows the doctor to see your optic nerve, which sends visual information from the eyes to the brain. Swelling of the optic nerve can be an early sign of raised pressure in the skull.

You are likely to have blood tests to check your overall health. Blood tests can also be used to check whether the tumour is producing unusual levels of hormones, which could indicate that the pituitary gland is affected.

A CT (computerised tomography) scan is a procedure that uses x-rays to take many pictures of the inside of the body and then compiles them into detailed, cross-sectional pictures.

A contrast dye may be injected into a vein to help make the scan pictures clearer. It may make you feel hot all over and leave a bitter taste in your mouth. You may also feel the need to pass urine. These side effects usually ease within minutes.

The CT scanner is a large, doughnut-shaped machine. You will lie on a table that moves in and out of the scanner. It may take about 30 minutes to prepare for the scan, but the actual test is painless and takes about 10 minutes. You will be able to go home when the scan is complete.

An MRI (magnetic resonance imaging) scan uses a powerful magnet and a computer to make cross-sectional pictures of your body. It may not be safe to have an MRI if you have a pacemaker or any other metallic object in your body. Some types of metal are MRI-compatible, however, so discuss this with your medical team.

For an MRI, you may be injected with a dye that highlights the organs in your body. You will then lie on an examination table inside a large metal tube that is open at both ends.

The test is painless, but the machine can be noisy and some people feel anxious or claustrophobic in the tube. If you think you may become distressed, mention it beforehand to your medical team. You may be given medicine to help you relax or you might be able to bring someone into the room with you for support. You will usually be offered headphones or earplugs. The MRI scan takes 30–90 minutes and you will be able to go home afterwards.

The pictures from an MRI scanner are generally more detailed than pictures from a CT scanner. Many people who first have a CT scan will also need to have an MRI.

You may also have some of the tests below to estimate how quickly the tumour is growing (the grade) and whether it has spread into nearby tissue. This information helps your doctor plan treatment.

MRS scan – An MRS (magnetic resonance spectroscopy) scan can be done at the same time as a standard MRI. It looks for changes in the chemical make-up of the brain.

MR tractography – This MR (magnetic resonance) scan helps show the message pathways (tracts) within the brain, e.g. the visual tracts. It can be useful in planning treatment for gliomas.

MR perfusion scan – This type of MR scan shows the amount of blood flowing to various parts of the brain. It can also be used to help identify the type of tumour.

SPET or SPECT scan – A SPET or SPECT (single photon emission computerised tomography) scan takes three-dimensional pictures showing blood flow in the brain. You will be injected with a small amount of radioactive fluid and then your body will be scanned with a special camera. Areas with higher blood flow, such as a tumour, will show up brighter on the scan.

PET scan – For a PET (positron emission tomography) scan, you will be injected with a small amount of radioactive solution. Cancer cells absorb the solution at a faster rate than normal cells do and show up brighter on the scan.

Lumbar puncture – Also called a spinal tap, a lumbar puncture uses a needle to collect a sample of cerebrospinal fluid from the spinal column. The fluid is checked for cancer cells in a laboratory.

Surgical biopsy – If scans show an abnormality that looks like a tumour, some or all of the tissue may be removed for examination under a microscope. This is called a biopsy. In some cases, the neurosurgeon makes a small opening in the skull and inserts a needle to take a sample. In other cases, a larger part of the skull has to be removed (craniotomy) to get to the tumour.

Genetic tests − Every kind of cancer, including brain cancer, changes the genes of the affected cells. These gene faults are not the same thing as genes passed through families. The fault is only in the structure of the tumour cells, not in the normal cells. The study of these gene changes is called cytogenetics or molecular genetics. A pathologist may run special tests on cells from the tumour to look for these gene changes. The results can help your doctors tailor the treatment for that particular tumour.