Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 88. Tumors of the Nervous System

Topics: Introduction | Brain Tumors | Spinal Cord Tumors | Neurofibromatosis | Radiation Damage to the Nervous System

Radiation Damage to the Nervous System

Although doctors try to prevent radiation from damaging the nervous system during cancer treatments, such damage is sometimes unavoidable. Symptoms of injury due to radiation can appear suddenly or slowly, can remain the same or worsen, and can be temporary or permanent. Sometimes symptoms do not appear until months or years after radiation therapy is completed.

Exposing the brain to radiation can cause acute encephalopathy, with fluid accumulation in the brain (cerebral edema) and neurologic symptoms such as headaches, nausea, vomiting, drowsiness, and confusion. Acute encephalopathy usually begins shortly after the first or second dose of radiation is administered, but sometimes it begins 2 to 4 months after radiation therapy is completed. Usually, symptoms diminish during the radiation treatments, and corticosteroids such as dexamethasone may help prevent or reduce cerebral edema.

Symptoms of brain damage that appear many months or years after radiation therapy are called late (delayed) radiation damage. These effects may occur after treatment of brain tumors in adults or after preventive radiation therapy for leukemia in children. Such symptoms include progressively worsening dementia, memory loss, difficulty thinking, mistaken perceptions, personality changes, and unsteadiness in walking.

If radiation therapy to the neck or chest encompasses the spine, radiation myelopathy may result. This disorder sometimes causes a sensation like an electric shock. The sensation begins in the neck or back, usually when the neck is bent forward, and shoots down to the legs. People with this type of radiation myelopathy usually improve without treatment.

Radiation myelopathy that develops many months or years after radiation therapy is called late (delayed) radiation myelopathy. This disorder causes weakness, loss of sensation, and sometimes the Brown-Séquard syndrome. In this syndrome, one side of the spinal cord is damaged, resulting in weakness on one side of the body and loss of pain and temperature sensation on the other side. On the weak side of the body, people may lose the ability to know where the hands and feet are without looking at them (position sense). Late radiation myelopathy usually does not subside and often results in paralysis.

Nerves near the site of the radiation therapy may also become damaged. For example, radiation to the breast or lung may damage nerves in the arms, and radiation to the groin may damage nerves in the legs. Weakness or loss of sensation may result.