Can MS Be Diagnosed After One Attack?

Current guidelines allow for earlier diagnosis

Multiple sclerosis affects the nerves.
Multiple sclerosis causes the destruction of the myelin sheath. BSIP/UIG/Getty Images

Diagnosing multiple sclerosis (MS) can be a difficult and often lengthy process. This is because there are no symptoms or lab tests that can, in and of themselves, determine if a person has MS.

The term multiple sclerosis itself describes a disease that causes multiple areas of cellular damage (hence, the term sclerosis meaning "scarring" or "hardening"). As such, you cannot point to a single event or test to definitively say that the person has MS.

With that being said, new guidelines have greatly streamlined the process, allowing us to deliver a definitive diagnosis in a relatively short space of time following the first appearance of the symptoms.

Progression of MS

Multiple sclerosis is a progressive inflammatory immune disorder which causes damage to the protective covering of nerve cells (called the myelin sheath).

This damage, known as demyelination, can disrupt nerve impulses between cells and lead to the formation of lesions on the brain and/or spinal cord. The formation and spread of these lesions can trigger an array of physical and cognitive symptoms that vary by where the location of the damage.

Clinically isolated syndrome (CIS) is the term used to describe the first symptom of MS that lasts for at least 24 hours and is accompanied by signs of inflammation and/or demyelination. CIS can be classified as one of two things:

  • A monofocal episode where one symptom is caused by one lesion
  • A multifocal episode where more than one symptom is caused by lesions in different locations

Current Criteria for Diagnosis

While it may seem reasonable to assume that a multifocal episode of CIS is enough to diagnose MS—given the evidence of cause and symptoms—the simple fact is that as many as 15 percent of people who have CIS never go on to develop MS.

We’re not entirely sure why this is, but what it does tell us is that a definitive diagnosis can only be made the disease is shown to be progressive

Under updated guidelines issued in 2010, MS can today be diagnosed based on the following criteria:

  • Two or more attacks (lasting for at least 24 hours and separated by at least 30 days) plus two lesions on an MRI scan
  • Two or more attacks, one lesion, and evidence that new lesions are starting to form on different parts of the brain and/or spinal cord (referred as the "dissemination in space")
  • One attack, two or more lesions, and evidence that new lesions have started to form since the last MRI (referred to the "dissemination in time")
  • One attack, one lesion, and evidence of dissemination in space and time
  • A worsening of symptoms or lesions plus dissemination in space (confirmed by either MRI or a spinal tap)

The guidelines overcome many of the shortcomings of the previous criteria (namely having to wait for multiple relapses before making a diagnosis). While the guidelines still don’t allow for diagnosis on one attack, they do greatly shortcut the process. Instead of waiting for another attack, doctors can now order a second MRIs in three months.

If there is evidence of additional lesions, it can often satisfy the definition of "dissemination in time" or "dissemination of space."

The Importance of Early Diagnosis

Early diagnosis has its benefits in the form of early treatment. Most research today strongly suggests that early treatment can significantly reduce the number of relapses a person may experience as well as the risk of disability over the short term.

Scientists, however, have yet to determine whether early treatment will improve the long-term outcome 10 or more years down the road. Future research will hopefully answer these questions as diagnostic technologies continue to improve.

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Article Sources
  • Polman, C.; Reingold, S.; Banwell, B. et al. “Diagnostic criteria for multiple sclerosis: 2010 Revisions to the McDonald criteria.” Annals of Neurology. 2011; 69(2):292-302.