DIAGNOSIS OF MS

There is no laboratory test, symptom, or physical finding which, when present or positive, always means a person has MS. In addition, some of the symptoms of MS could also be caused by other diseases. Consequently, the diagnosis of MS must be made by a careful process which demonstrates findings that are consistent with MS, and that also rules out other causes.

The basic "rule" for diagnosing MS relies on two criteria:

• There must have been two attacks at least one month apart. An attack, also known as an exacerbation, flare, or relapse, is a sudden appearance of or worsening of an MS symptom or symptoms which lasts at least 24 hours.
• There must be more than one area of damage to central nervous system myelin—the sheath that surrounds and protects nerve fibers. The damage to myelin must have occurred at more than one point in time and not have been caused by any other disease that can cause demyelination or similar neurologic symptoms.

MRI is the preferred method of imaging the brain

MRI (magnetic resonance imaging) is currently the preferred method of imaging the brain to detect the presence of plaques or scarring caused by MS. It is better at detecting plaques than CT scanning. Often brains that appear to be normal on CT scans will be shown to have plaques on MRI.

Still, the diagnosis of MS cannot be made solely on the basis of MRI. There are other diseases that cause lesions—areas of damage—in the brain that look like those caused by MS. There are also spots found in healthy individuals, particularly in older persons, that are not related to any ongoing disease process.

On the other hand, a normal MRI does not absolutely rule out a diagnosis of MS. About 5% of patients who are confirmed to have MS on the basis of other criteria, do not show any lesions in the brain on MRI. These people may have lesions in the spinal cord or may have lesions which cannot be detected by MRI.

Clinical exam includes history and tests of function

Other symptoms of MS will be evaluated during the clinical examination conducted by a physician. This covers an extensive review of mental, emotional, and language functions, movement and coordination, vision, balance, and the functions of the five senses. Sex, birthplace, family history, and age of the person when symptoms first began are also taken into consideration.

Sometimes, other tests are needed

It is not usually necessary to do all diagnostic tests for every patient. If, however, a clear-cut diagnosis cannot be made based on the tests above, additional tests may be ordered. These include tests of evoked potentials, cerebrospinal fluid, and blood.

Evoked potential tests are electrical diagnostic studies which can show if there is a slowing of messages in the various parts of the brain. They often provide evidence of scarring along nerve pathways that is not apparent on a neurologic exam.

Cerebrospinal fluid, usually taken by a spinal tap, is tested for levels of certain immune system proteins and for the presence of oligoclonal bands. These bands indicate an abnormal autoimmune response within the central nervous system, meaning the body is producing an immune response against itself. Oligoclonal bands are found in the spinal fluid of about 90-95% of people with MS, but since they are present in other diseases as well cannot be relied on as positive proof of MS. They may also take some years to develop.

While there is no definitive blood test for 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.