There are no laboratory tests, symptoms, or physical findings that can, by themselves, determine if a person has multiple sclerosis. Furthermore, there are many symptoms of MS that can also be caused by other diseases. Therefore, the MS diagnosis can only be made by carefully ruling out all other possibilities.

The long-established criteria for diagnosing MS are:

• There must be objective evidence of two attacks (i.e. two episodes of demyelination in the central nervous system). An attack, also known as an exacerbation, flare, or relapse, is defined clinically as the sudden appearance or worsening of an MS symptom or symptoms, which lasts at least 24 hours. The objective evidence comes from findings on the neurologic exam and additional tests.

• The two attacks must be separated in time (at least one month apart) and space (indicated by evidence of inflammation and/or damage in different areas of the central nervous system).

• There must be no other explanation for these attacks or the symptoms the person is experiencing.

Over the last twenty years, tests such as magnetic resonance imaging, examination of cerebrospinal fluid, and evoked response testing have played an increasingly important role in the diagnostic process.

Additional testing can be very helpful in establishing a diagnosis of MS. Nearly everyone with MS has characteristic MRI changes in MS. Still, the diagnosis of MS cannot be made solely on the basis of MRI. There are other diseases that cause changes in the brain that look like those caused by MS. There are also spots found in healthy individuals, particularly in older persons, which are not related to any ongoing disease process.

In addition to the MRI other tests are often helpful and may be required to establish a defitive diagnosis of MS. Cerebrospinal fluid, sampled by a spinal tap, is tested for levels of certain immune system proteins and for the presence of oligoclonal bands. These bands indicate an immune response within the central nervous system. Oligoclonal bands are found in the majority of people with MS. However, like the MRI, oligoclonal bands cannot be relied on as positive proof of MS. Evoked potentials are another test which is sometimes needed in the evaluation of MS. Blood tests can rule out other causes for various neurologic symptoms. Some other conditions that cause symptoms similar to those of MS are Lyme disease, a group of diseases known as collagen-vascular diseases, certain rare hereditary disorders, and AIDS.

NMSS Sourcebook: diagnosis