How is MS diagnosed?

If you’re worried you have MS, you should speak to your GP. If they can’t diagnose the cause of your symptoms, they can refer you to specialists to look into it further. That could include a neurologist if they think your symptoms are to do with nerves or the nervous system. 

What does a neurologist do to diagnose MS?

Neurologists follow guidelines called the McDonald criteria to diagnose MS. A neurologist is a specialist in nerves and the nervous system. They'll use the symptoms you describe, and the results of their examination, to build up a picture of what’s happening. Then they’ll arrange tests to check for damage in the central nervous system (the brain, spinal cord and optic nerves).

A diagnosis of MS is based on finding evidence of damage in different parts of your central nervous system. Usually to diagnose MS they need to see that this damage has happened at different times, not just once. 

A neurologist puts all the evidence together to make the right diagnosis.

Read more about the McDonald criteria

Tests to diagnose MS

There are a few ways that a neurologist will test for MS. There's no single test for MS, but added together they help them make the diagnosis. The tests include:

Examination

Your neurologist will ask you lots of questions about your health problems and symptoms, now and in the past. They'll also give you a physical examination. This will check for changes or weaknesses in your eye movements, leg or hand coordination, balance, speech or reflexes.

All this gives your neurologist a better picture of where in your brain or spinal cord the problem is. It can also identify something else behind your symptoms that's not MS.

While your neurologist may strongly suspect MS at this stage, they won't be able to give you a diagnosis until other test results confirm that it's MS.

Magnetic resonance imaging (MRI)

An MRI scanner uses a strong magnetic field to create a detailed image of inside your brain and spinal cord. It's very accurate and can pinpoint the exact location and size of inflammation, damage or scarring (lesions). MRI scans confirm a diagnosis in over 90 per cent of people with MS.

To get the image of your brain and spinal cord you'll be asked to lie down and enter a small tunnel in the centre of the MRI scanner. The process can take between 10 and 60 minutes and is painless. But some people can feel a little claustrophobic in the scanner. 

Read 7 things to know about MRI and MS

Evoked potentials tests

These painless tests are used less now than in the past but you still might have one. To test for MS, they measure the time it takes for your brain to receive messages or signals from your eyes, ears and skin.

To measure these signals, someone will put small electrodes on your head. These check how your brain reacts to sounds you hear in headphones or patterns you see on a screen. To measure signals between your brain and skin, electrodes will be put on your arm or leg. It can help neurologists diagnose MS if signals to and from your brain are slower. That could be a sign MS has damaged the protective covering around some of your nerves (called myelin).

Lumbar puncture or spinal tap

For this test the medical staff give you a local anaesthetic. Then they put a needle in your lower back. It goes into the space around your spinal cord and collects a small sample of the fluid there. This is then tested for signs of MS. 

After this type of test, you might get a headache that can last several days but then goes away. Your medical team will talk to you about how to manage this. 

Blood tests and tests for other conditions

Your neurologist might also want to rule out conditions that are similar to MS by running some other tests. These could include blood tests to check for particular antibodies, and inner ear tests to check your balance.

How long does it take to diagnose MS?

Unfortunately there's no simple answer to how long it takes to diagnose MS. It can vary a lot between people, and for lots of reasons.

Most people will notice symptoms and first speak to their GP. It can take many weeks or months from that point to investigate possible causes. Different tests and specialists can be involved to get to the right answer.

If the diagnosis is MS, that can only be made by a neurologist. But other specialist doctors might have been involved to rule out other causes too. Waiting for referrals, tests and test results can all take time. There is support if you're waiting for a diagnosis.

Occasionally, an MS diagnosis happens quickly. For example, if someone stays in hospital for treatment of their symptoms and tests reveal the MS has been active in their brain in the past. This is not most people's experience of diagnosis, but it can be a shock to be diagnosed so unexpectedly. 

Whether you've just been diagnosed or you're waiting for answers, our MS Help service has information and support for you and your loved ones/