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.  In 2001, the International Panel on the Diagnosis of Multiple Sclerosis, chaired by W.I. McDonald, FRCP (Royal College of Physicians, London), issued a revised set of diagnostic criteria (Annals of Neurology 2001; 50:121-127).  In addition to the traditional requirements, the revision provides specific guidelines for using findings on MRI, cerebrospinal fluid analysis, and visual evoked potentials to provide evidence of the second attack and thereby confirm the diagnosis more quickly.  These guidelines also facilitate the diagnostic process in those patients who have had steady progression of disability without distinct attacks.

MRI Is the Preferred Method of Imaging the Brain

MRI (magnetic resonance imaging) is the preferred method of imaging the brain to detect the presence of plaques or scarring caused by MS. This technology is able to detect lesions in different parts of the central nervous system and differentiate old lesions from those that are new or active.

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, which are not related to any ongoing disease process.

On the other hand, a normal MRI cannot 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 that cannot be detected by MRI.  Eventually, however, the vast majority of people with MS will have brain and/or spinal lesions on MRI.  The longer the MRI remains negative, the more questionable the diagnosis becomes.  If the MRI findings continue to be negative more than a year or two after the initial diagnosis is made, every effort should be made to identify another possible cause for the symptoms. 

Clinical Exam Includes History and Tests of Function

During the clinical examination, the physician takes a careful history to identify any past events that might be indicative MS-related disease activity, and performs a variety of tests.  These tests evaluate 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.

Other Tests Are Needed Sometimes

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 that can show if there is a slowing of nerve transmissions (messages) in various parts of the brain. They often provide evidence of scarring along nerve pathways that is not apparent on a neurologic exam. 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 spinal fluid of about 90-95% of people with MS. Since, however, they are present in other diseases as well, oligoclonal bands cannot be relied on as positive proof of MS. 

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. 

The Importance of a Timely and Accurate Diagnosis

Making the diagnosis of MS as quickly and accurately as possible is important for several reasons:  People who are living with frightening and uncomfortable symptoms want and need to know the reason for their discomfort.  This enables them to begin the adjustment process and relieves them of worries about other diseases such as cancer.  Since we now know that permanent neurologic damage can occur even in the earliest stages of MS, it is important to confirm the diagnosis so that the appropriate treatment(s) can be initiated as early in the disease process as possible.