MS lesions

What are MS lesions?

MS lesions are areas of damage and scarring in the brain or spinal cord. The name multiple sclerosis means ‘many scars’. MS damage happens when the immune system attacks the protective coating around nerves (called myelin).

This damage can cause MS symptoms, though symptoms and lesions don’t always match up. Someone might have new lesions without noticing symptoms, or new symptoms without obvious lesions. The lesion can be a sign of active damage or damage that has happened previously.

Not all lesions are MS lesions. For example, migraine and ageing can also cause lesions which show up on an MRI scan.

What do MS lesions do?

The damage that shows up in an MS lesion slows down or stops messages travelling along nerves. And this affects your control over parts of your body, causing MS symptoms. MRI scans can show different kinds of lesions, including ‘active’ and ‘non-active' lesions:

• An active MS lesion is a sign of inflammation that’s going on now. For example, with an MS relapse
• a non-active MS lesion is a sign of older damage. Older lesions aren’t highlighted by a gadolinium enhanced MRI. They can be seen with other MRI techniques

Lesions, PIRA and smouldering MS

You might hear the words ‘smouldering MS’ and ‘PIRA’ when talking about lesions and the way MS can change over time. PIRA stands for ‘progression independent of relapse activity’. Both PIRA and smouldering MS describe when MS symptoms get worse, but not because of a relapse.

This kind of MS activity can show up on MRI scans. Neurologists can see differences in the lesions compared to relapse lesions. The have a dark rim around their outside – sometimes called a paramagnetic rim. Researchers are working to understand more about this kind of lesion and what causes them. They’re also improving the ways we can see them on MRI. This will help us to find new treatments.

Read more about smouldering MS and PIRA

Read more about active MS and MS with progression

How do I know if I have MS lesions?

With an MRI scan, a neurologist or radiologist can see MS lesions on the spinal cord or brain (which includes your optic nerve that connects to your eyes). An MRI scan is usually done to help diagnose MS. MRI scans are part of the McDonald criteria for diagnosing MS.

If you’re diagnosed with MS, you might also have scans to monitor your MS or see how a treatment is working for you. For example, a scan could show if you have any new or changing lesions since the last scan.

In a similar way, researchers often look at MRI scans of people taking part in clinical trials to see if a new drug reduces the number or size of MS lesions.

Different kinds of MRI scans

An MRI machine can scan in different ways to see different kinds of lesions. For example, you might hear about T1 or T2 scans. Some MRI scanners can detect extra detail about lesions, like the ‘central vein sign (CSV)’ or ‘paramagnetic rim lesion (PRL)’.

The detail neurologists can see helps them make a correct diagnosis or understand how MS is behaving inside the brain and spinal cord.

Gadolinium enhanced lesions

You might have an injection before your MRI, to highlight any active lesions. That’s called a gadolinium enhanced MRI or an MRI scan with contrast. On an MRI, the gadolinium highlights areas of the brain where inflammation is happening.

Read more about MRI scans

MS lesions in the brain or spinal cord

MS lesions in the brain and spinal cord can cause different symptoms, depending on where they are.

But lesions on an MRI don’t always match up to symptoms. For example, an MRI scan might show new lesions without you experiencing new or worsening symptoms.

People with relapsing remitting MS often have lesions mostly or only in their brain. Lesions in the spinal cord tend to be more common for people with progressive MS.

Read more about types of MS