There is no specific medical test that confirms multiple sclerosis (MS). A diagnosis is made by ruling out other conditions that may be causing similar symptoms, as well as analyzing the results from a series of evaluations.

The diagnostic process may begin after a patient experiences a "clinically isolated syndrome," or CIS. A CIS can be the first attack of MS, defined as a health event that may indicate nerve damage has occurred. For example, a sudden vision disturbance or numbness in the limbs, in the absence of any additional symptoms, could signal a CIS.

At first a CIS can appear to be the result of some other condition, particularly if it happens only once and goes away. But a regimen of tests to rule out other causes can help finalize a diagnosis of MS.

The types of tests that may be used to diagnose multiple sclerosis include:

• Blood analysis — A blood test can help determine if another infectious or inflammatory disease may be causing MS-like symptoms.
   
• Lumbar fluid analysis — A small sample of spinal fluid is obtained to check for abnormal levels of white blood cells or proteins. This test can also help rule out infections or other causes of MS-like symptoms.
   
• Magnetic resonance imaging (MRI) — The loss of myelin, the protective covering of the nerve cells, can appear with MRI as lesions on the brain or spine. An intravenous dye injected before MRI can help determine if lesions are in an "active" state, giving more information about the phase of the disease.
   
• Evoked potential tests — These painless tests measure electrical activity in certain areas of the brain in response to visual, auditory and sensory stimulation. Results can indicate problems along certain nerve pathways. If nerves have lost their covering, or myelin, the nerve impulses will be slowed, garbled or stopped.