In most individuals with MS, their diagnosis is established over time and the consideration of alternative causes for their symptoms. One astonishing fact about MS, is that once an individual has a typical problem associated with MS, the risk of having MS within 15 years is 90% even if all other tests show negative findings. The gold standard of diagnosis is seeing multiple problems in the nervous system come and go without another explanation.

The most useful tests for multiple sclerosis are MR imaging of the brain and sometimes spinal cord, cerebrospinal fluid examination for abnormal immune proteins, and electrical testing such as evoked responses. Other testing is often used to exclude other potential causes of the symptoms. These tests are minimally invasive and may be repeated after a period of time (usually years) if the diagnosis is inconclusive.