Multiple sclerosis is an autoimmune disease caused by the immune system attacking parts of the central nervous system (CNS) — which includes the brain, spinal cord, and optic nerves. An early diagnosis of the disease is important but can be challenging. Clinicians may use something called the McDonald criteria to make a definitive MS diagnosis.
The McDonald criteria are a set of guidelines that incorporate clinical and laboratory evaluations, as well as magnetic resonance imaging (MRI) data, to establish an MS diagnosis.
The first version of the criteria was published in 2001 by an international team led by neurologist Ian McDonald. The criteria have since been extensively updated several times, most recently in 2017 revisions.
To fulfill a diagnosis of MS based on the 2017 McDonald criteria, an individual must have:
If the individual does not meet these two criteria, then the clinical case will be considered not MS.
Dissemination in space means that neurological damage is occurring in multiple parts of the CNS. Specifically, the 2017 criteria define dissemination in space as disease lesions in at least two of four regions in the nervous system. These regions include three areas of the brain (periventricular, juxtacortical or cortical, and infratentorial) and the spinal cord.
Notably, while lesions in the optic nerves are common in MS, the criteria for dissemination in space cannot be fulfilled with optic nerve lesions in a person with symptoms of optic neuritis, or inflammation in the optic nerves.
Similarly, dissemination in time means that neurological damage is happening at more than one point in time. This can be evidenced either by a second disease exacerbation, the appearance of new lesions on MRI scans, or by clear-cut evidence of brain damage that happened at different times — specifically, new inflammatory lesions alongside older lesions that are no longer actively inflamed.
A contrast agent called gadolinium can be used during an MRI to better distinguish active and inactive lesions. Gadolinium enhancing lesions represent areas of active inflammation.
Oligoclonal bands are antibodies (also called immunoglobulins) that are characteristically detected in the cerebrospinal fluid (CSF) — the fluid surrounding the brain and spinal cord — in people with MS.
The presence of these proteins is indicative of CNS inflammation and is an independent predictor of relapse in individuals with clinically isolated syndrome (CIS). Those with CIS experience a single episode of MS-like symptoms.
Thus, under the 2017 McDonald criteria, testing positive for oligoclonal bands can be sufficient to fulfill the criteria for dissemination in time, even if a patient only has evident damage from one time point.
For a definitive MS diagnosis, dissemination in time must be shown by one of the following:
Dissemination in space also must be demonstrated by one of the following:
The updated 2017 version of the McDonald criteria, which follows a 2010 revision, does not invalidate an MS determination for those previously diagnosed based on older versions of these criteria.
The main goal of this new version was to simplify or clarify elements of the previous criteria. The updates are designed to facilitate earlier diagnoses in cases in which the disease was considered only “possible MS,” and to help improve diagnostic accuracy and avoid misdiagnosing MS.
Similar to the previous revision, the 2017 McDonald criteria continue to apply primarily to patients with CIS. The three main updates to the criteria, focused on typical CIS, were that:
Most people with the disease experience MS relapses, also called exacerbations or attacks. These are times of suddenly worsening symptoms that are accompanied by inflammation in the CNS, followed by remissions when symptoms ease.
A person who has experienced at least two clinical attacks, and has clear-cut evidence of damage in at least two distinct brain areas, can be definitively diagnosed with MS, as that individual fulfills requirements for both dissemination in space and time.
If a person has experienced at least two relapses but has objective evidence of damage in only one brain region, then that individual has fulfilled the criteria for dissemination in time, but not in space. Damage in another brain region — either demonstrated by a subsequent relapse implicating a different brain region, or by an MRI scan — must be detected before MS can formally be diagnosed.
Similarly, someone with lesions in two or more brain regions who experienced only one MS-like exacerbation fulfills the criteria for dissemination in space, but not in time. New damage occurring over time, evidenced by a new lesion on MRI scans or by another relapse, is needed for a formal diagnosis. Alternatively, testing positive for oligoclonal bands can be enough to fulfill the criteria for an MS diagnosis in such patients.
If a person has had one MS-like attack and has evidence of damage in one brain region, then that individual has not fulfilled the criteria for dissemination in space or in time. A formal diagnosis of MS cannot be made without clear evidence of further damage in other brain regions occurring over time.
Unlike the more common relapsing forms, primary progressive MS (PPMS) is not characterized by disease relapses. Instead, this disease type is defined by disability that gradually gets worse over time, starting from the onset of the disorder.
According to the 2017 McDonald criteria, PPMS may be formally diagnosed in people who experience worsening disability for at least one year (based on previous symptoms or ongoing observation), and who exhibit at least two of the following:
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Yes. The McDonald criteria are a formal set of guidelines that enable an accurate diagnosis of MS as early as possible. Depending on the clinical presentation of each patient, or the symptoms the person experiences, the criteria determine which additional tests should be performed before a formal diagnosis can be made. Therefore, using the criteria can allow MS to be diagnosed as quickly as possible.
Dissemination in time means that there is MS-like neurological damage that is occurring at multiple points in time. Similarly, dissemination in space means that the damage is affecting multiple parts of the brain and/or spinal cord. Under the McDonald criteria, only patients meeting both of these requirements can receive a formal MS diagnosis.
Relapses are important clinical factors that help establish a formal MS diagnosis. For example, tracking relapses can be useful for telling whether or not a person meets the criterion of dissemination in time: If a person has had at least two relapses, this is clear evidence of inflammatory brain damage happening at multiple points in time. The symptoms that appear during relapses also may indicate damage to different parts of the central nervous system, which can be used to fulfill the criterion of dissemination in space.
Optic neuritis refers to inflammation in the optic nerves, which transmit information from the eyeballs to the brain. According to the 2017 McDonald criteria, the optic nerves are not one of the regions that can be considered when determining whether or not a person with optic neuritis fulfills the criterion of dissemination in space.
The 2017 updates to the McDonald criteria aimed to simplify and clarify elements of older versions of the criteria, to help facilitate an earlier diagnosis of MS. A key update was the inclusion of oligoclonal bands in the cerebrospinal fluid as a possible surrogate of dissemination in time. That inclusion takes into account both symptomatic and asymptomatic lesions when determining dissemination in space or time. The updated version also counts lesions in the brain’s cortex, in addition to juxtacortical ones, when assessing for dissemination in space.
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