Magnetic resonance imaging (MRI) and MS

What is an MRI scan for?

An MRI scan is used to create a detailed image of inside your brain or spinal cord. They’re very accurate and can pinpoint inflammation, damage or scarring. MRI scans confirm a diagnosis in over 90% of people with MS. 

What does an MRI look like?

An MRI scanner is a large machine, which looks like a giant doughnut (the scanner part) and a sliding bed (which you lie on). The bed moves into the short tunnel through the middle of the ‘doughnut’ and stays there while the scan happens. Some hospitals have an ‘open MRI’ which have a more open space for the bed.

What happens during an MRI scan?

Before your MRI scan

When your doctor refers you for an MRI, tell them if:

• you have metal in or on your body
• you’re pregnant or breastfeeding
• you’re allergic to contrast agent (a substance you take that makes things on your scans show up more clearly)
• you have kidney problems.

You normally won’t have to fast (not eat or drink) before your MRI scan unless they tell you to.

Before your scan, you’ll need to remove all metal items like jewellery and any clothes with metal zips and fastenings. 

During your MRI scan

During an MRI scan you’ll be asked to lie flat on a bed that’s then moved inside the scanner. You’ll be asked to keep as still as possible, so it’s important to get comfortable at the start.

Read Nicola's tips on having an MRI scan

After your MRI scan

An MRI scan is normally what we call an ‘outpatient procedure’. This means it’s something you have, then you go home the same day. If you’ve had a sedative, someone will need to take you home.

It might take a few weeks for your results to come back to your doctor or neurologist. 

The McDonald criteria are used to decide on an MS diagnosis and will include the results of your MRI. 

How long does an MRI scan take?

MRI scans usually last for 15 to 90 minutes.

What are the side effects of MRI scans?

If you have a gadolinium injection before your MRI scan, it's possible to have side effects from this. The gadolinium is used to show up certain details on the scan. For example, it can help doctors see the difference between old and new MS damage. The hospital might also call the gadolinium a ‘contrast medium’.

You might get a small bruise in the area where you had the gadolinium injection. And the NHS mentions some possible side effects which are usually mild and don’t last long:  

• feeling sick or being sick
• a skin rash
• a headache
• a metallic taste in your mouth
• feeling dizzy   

The NHS also notes that rarely there can be allergic reactions to the gadolinium injection, including:

• coughing, wheezing or sneezing
• fainting
• difficulty breathing or swallowing
• a rash, hives or itchy red skin

The hospital will ask you to wait for about half an hour after the scan, just to check there’s no reaction to the gadolinium injection. 

Read the NHS page about MRI scans

How does an MRI scan work?

An MRI scan uses powerful magnets and radio waves to take images of your brain or spinal cord.

MRI measures how much water there is in the body. Because different parts of the brain have different amounts of water, we can use MRI to distinguish them and build up pictures of the central nervous system, your brain and spinal cord.

The protective myelin coating is a fatty substance, so it repels water. This means we can measure how much myelin is present because it looks different to nerves and other cells in the brain or spinal cord on a scan.

Is an MRI scan scary?

MRI scans are painless but some people can find them claustrophobic and the machine can be noisy. There’ll be medical staff with you to keep you as comfortable as possible. MRI scans are not invasive (no medical object goes into your body).  

To make it more pleasant, you might be able to play music through hospital headphones while you’re in the scanner. Check in advance if they can connect to your own phone or CDs so you can choose what you listen to. They might have a selection of music to choose from. 

The moving magnets in the MRI scanner make a loud banging noise, so you’ll be given ear plugs to wear even if you don’t listen to anything on their headphones.

Are MRI scans safe?

MRI scans are one of the safest medical procedures available, but may not be suitable for everyone. If you have a metal implant, such as a pacemaker or artificial joint, you might not be able to have an MRI scan. If you’re pregnant, you should speak to your doctor about whether an MRI scan is suitable for you.