Total lymphoid irradiation uses radiation to limit the production of white blood cells (lymphocytes). These cells help the body's immune system destroy foreign cells and fight infection. The treatment was first developed to treat Hodgkin's lymphoma, a form of cancer, and has been used successfully to treat people with rheumatoid arthritis, which, like multiple sclerosis (MS), is an autoimmune disease.

In theory, total lymphoid irradiation may help prevent progression of MS by limiting the production of lymphocytes and thus limiting the activity of the immune system. The results of studies done so far have failed to show any benefit.

Total lymphoid irradiation remains an experimental treatment for MS. The treatment may be toxic and potentially dangerous and, in general, is not recommended.

Side effects of this treatment may include:

• Absence of menstrual periods in women.
• Nausea.
• Fatigue.
• Depression.
• Minor bone fractures.
• Impaired immune system.