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13 March 2020

McDonald MS criteria: Everything you need to know

When you are diagnosed with MS, the McDonald criteria may have been used. We explain everything you need to know.

What is the McDonald MS criteria?

MS can be difficult to diagnose, because the symptoms can be mistaken for other medical issues. There is no single test that is completely diagnostic of MS. You may find that you are in and out of your doctor’s office for a while with curious symptoms, and some symptoms you may have simply disregarded for another explanation. While the wait can be unsettling, and wanting answers to your questions and to start treatment as soon as possible, you also don’t want to be diagnosed with MS in error — it has to be a careful process. MS diagnosis is complex, and it involves:

  • Your medical history
  • MRI imaging of the brain and sometimes the spinal cord
  • Evidence from a clinical examination
  • Laboratory tests

It is reassuring to know that the McDonald criteria can speed up the diagnosis process so that people with MS can get access to the appropriate treatment. The McDonald MS criteria is a tool that a doctor will use to make an accurate and sensitive MS diagnosis as quickly as possible. The criteria guides the doctor into the right tests to make sure that the diagnosis is thorough.

Professor Ian McDonald first published the McDonald MS criteria in 2001 and since then a panel of MS experts have considered the latest research to make regular updates.

Revised versions of the McDonald criteria

The McDonald criteria were originally introduced in 2001 and revised in 2005, 2010 (MS diagnosed on first presentation to a doctor), 2016 by Magnetic Resonance Imaging in MS (MAGNIMS), and most recently in 2017. The McDonald criteria must be revised as an ongoing process, so that the information is current and reflects our expanding knowledge of MS, and the diagnostic resources available.

If you were diagnosed with MS before a revision, the newest version will not affect your diagnosis, it just means that a doctor may be able to diagnose MS sooner, offering treatment earlier.

Speeding up diagnosis

The latest revision was in 2017 and was revised by an international panel of 30 MS experts, co-chaired by Alan Thompson, MD (University College London) and Jeffrey Cohen, MD (Cleveland Clinic). This revision aims to reduce the possibility of misdiagnosis and also speeds up the diagnostic process.

The 2017 revision kept the key criteria, with no changes:

  • The McDonald criteria continues to apply to people with clinically isolated syndrome (CIS).
  • MS should be diagnosed by a clinician with MS expertise.
  • Dissemination of lesions in the nervous system in time and space  need to be seen.
  • There is no better explanation than MS for the symptoms.

However, the panel added that:

  • The MS course and type of MS should not be given at the time of diagnosis. When they are given, they need to be re-evaluated regularly.
  • Cerebrospinal fluid (CSF) and paired serum samples need to be examined to find out if the oligoclonal bands are unique to the CSF.
  • Brain MRI and spinal MRI should be collected if further information is needed.

Clinically isolated syndrome (CIS) refers to a first episode of neurological symptoms that you may feel when you go to the doctors seeking a diagnosis. The symptoms must last at least 24 hours and are caused by inflammation or loss of myelin that covers the nerve cells in the central nervous system (CNS).

There were also key changes in the 2017 McDonald criteria for those with clinically isolated syndrome (CIS):

  • The site of lesions – as well as juxtacortical lesions, cortical lesions were added to the MRI criteria (for dissemination of lesions in space)
  • The types of lesions – the 2017 revision added that symptomatic MRI lesions are now also considered in determining dissemination in space or time.
  • CSF oligoclonal bands – oligoclonal bands in the spinal fluid can be used as an example of dissemination of lesions in time.

Unfortunately, misdiagnosis of MS is not uncommon. If the person seeking diagnosis is at an age where MS is less common, for example older people or children, MS may not be initially considered. The McDonald criteria helps to collect the evidence needed to conclude that the person has MS, or indeed something else, that requires a different treatment.

Future research

In 2017, the panel recommended that the research continue so that the diagnostic process continues to be improved in the future.