MRI Scans
Most people being investigated for MS are now given an MRI scan. As it is the only test that actually shows up MS-type lesions (areas of damage) in the nervous system, it is an extremely useful diagnostic tool. However, even an MRI scan cannot conclusively prove whether or not you have MS. While 90% of people with MS have lesions that show up on a scan, the other 10% do not. Also, other diseases can produce identical looking lesions. Researchers have even found lesions in completely healthy people who have volunteered to act as controls in studies.
MRI stands for magnetic resonance imaging. It uses a combination of powerful magnets and pulses of radio waves to produce signals that are processed into a computer image of the brain and spinal cord. The way in which different body tissues show up on MRI depends on their water content. Lesions have a higher water content than normal nerve tissue, and show up as abnormal patches on the scan. The procedure is painless and does not involve X-rays or any other type of harmful radiation.
When you go for an MRI scan you will be asked to lie on a bed which is then moved inside the cylindrical body of the scanner. Some people find this claustrophobic. The part of the body to be scanned must be kept completely still, and the technician may immobilise your head with straps or padding. There is usually a buzzer and/or intercom inside the scanner, so you can communicate with medical staff if you need to.
When the scanner is switched on there is a loud clanking sound as the magnets are powered up. The noise is normal and does not mean the machine is broken! You may be given earplugs or headphones to block it out. The doctor will want to scan at various different angles and settings, and you will probably be in the machine for about 30 minutes. Sometimes he or she may want to use a contrast agent to enhance the image. This is given into your vein (intravenously), and is later expelled from the body in the urine.
One of the major advantages of MRI is that it can be used to track the progress of the disease. Scans taken months or years apart can be compared to see whether and where any new lesions have developed. For this reason it is often used in clinical trials to assess the effectiveness of treatments. The technology of MRI is still evolving, and offers the prospect of new breakthroughs in our understanding of MS.