Signs and symptoms of multiple sclerosis vary widely, depending on the location of affected nerve fibers. Also, many people experience relapses of symptoms, particularly in the beginning stages of the disease, which are followed by periods of complete or partial remission. Signs and symptoms of multiple sclerosis often are triggered or worsened by an increase in body temperature.

Most patients first seek medical help after an initial inflammatory event (known as a clinically isolated syndrome) originating from demyelination in the eye, the spinal cord, or the brain. About 30% of these individuals will develop progressive MS within the year. At this time, however, experts cannot predict who among these patients are at highest risk for rapid progression.

No single test can accurately diagnose MS, and a number of other conditions may mimic its symptoms. Some doctors use a set of factors, called the McDonald criteria, for diagnosing multiple sclerosis in early stages. The criteria include the presence of specific symptoms, spinal fluid evaluation, and magnetic resonance imaging techniques for detecting lesions within the central nervous system and tracking them over time. The criteria show high reliability in identifying MS in patients with a variety of disease stages or states, including having only one episode, a typical relapsing-remitting course, or a slow insidious progression without clear attacks or remissions. Other tests for MS include:

• Blood tests
  Analysis of your blood can help rule out some infectious or inflammatory diseases that have symptoms similar to multiple sclerosis.
• Spinal tap (lumbar puncture)
  In this procedure, a doctor or nurse removes a small sample of cerebrospinal fluid from within your spinal canal for laboratory analysis. This sample can show abnormalities associated with multiple sclerosis, such as abnormal levels of white blood cells or proteins. This procedure can also help rule out viral infections and other conditions that can cause neurological symptoms similar to those of multiple sclerosis.
• MRI
  This test uses a powerful magnetic field and radio waves to produce detailed images of internal organs. MRI can reveal lesions, indicative of the myelin loss caused by multiple sclerosis, on your brain and spinal cord. However, these types of lesions can also be caused by other conditions, such as lupus or Lyme disease, so the presence of these lesions isn't definitive proof that you have multiple sclerosis.

Generally, there is no way to prevent multiple sclerosis or its attacks. For people with relapsing-remitting MS, treatment with interferon beta or glatiramer acetate may reduce the frequency of relapses, and interferon beta may delay disability.
Claims have been made that MS may be brought on by injury, shock, pregnancy, or vaccinations, but there is no scientific evidence to prove these claims. If you already have MS, a viral infection (such as the flu) may trigger a relapse. During pregnancy, women with MS often have fewer relapses. In the first few months after delivery, however, they may temporarily have more relapses.
If you have MS, avoid overheating your body whenever possible. Increased body temperature can temporarily make your symptoms worse by causing the nerves already affected by MS to function even more poorly.