There isn't a specific test available to diagnose multiple sclerosis. Instead, your signs and symptoms must meet certain criteria. But even this system isn't 100% accurate.

A diagnosis of MS is based on your medical history, a neurological exam (which is an examination of how well your brain and spinal cord are functioning), and possibly other tests. These other tests may include things like blood tests, an MRI, a spinal tap, or an electrical test called "evoked potentials," which tests the function of your sensory nerves.

The specific criteria doctors look at when determining if a person has MS include:

* The signs and symptoms begin between the ages of 15 and 60.

* The signs and symptoms indicate a disease of the brain or spinal cord.

* A doctor's exam finds evidence of a diseased brain or spinal cord.

* An MRI scan shows at least two separate areas of scar tissue, or "sclerosis."

* The disease has followed one of two patterns:

First, there have been two or more episodes of symptoms that last at least 24 hours and happen more than a month apart. Or, second, your signs and symptoms have progressively increased over the past six months.

* Finally, there can be no other explanation for your symptoms.

Based on these factors, a diagnosis of multiple sclerosis can be made.