What are the Effects of Radiation Therapy on the Brain?

Brain tumors may need to be treated with radiation therapy. Using radiation therapy can have both desired and unwanted effects on the brain. The desired result of radiation therapy on the brain is to eradicate the tumor. The treatment may have other, unwanted effects on the brain, however. Side effects may include speech and hearing difficulties, nausea, headaches, and brain swelling.

Radiation therapy on the brain works by killing the cells that make up the tumor. The radiation destroys the genetic material in the cell, which kills the cells and also prevents them from reproducing. Because the radiation can also damage healthy cells, radiation therapy on the brain also can have damaging results.

Certain side effects may develop immediately and may be temporary. Other side effects are delayed and may be lasting in some people. The type and severity of unwanted effects on the brain depends on the area of the brain receiving radiation, the duration of treatment, and type of radiation therapy used. There are a few types of radiation therapy for brain cancer. Certain types of radiation therapy may cause fewer side effects.

Traditional radiation therapy uses gamma rays or x-rays directed at an area of the brain from an external beam. Intensity-modulated radiation therapy is a relatively new form of radiation therapy on the brain. It is more precise and can deliver the radiation to a specific area within the brain, while sparing other areas. This may reduce unwanted effects.

Although certain types of radiation therapy may reduce the chances of unwanted effects on the brain, they still may occur. Swelling of the brain is a common side effect. When this occurs, a patient may develop a headache, seizures, and vomiting from the increased pressure inside the head. Medication is available to help reduce brain swelling.

Other effects on the brain depend on what area of the brain received radiation therapy. For instance, if an area of the brain that controls speech is radiated, language skills may be affected. If an area near the hypothalamus received radiation therapy, pituitary function and hormone production may be affected. This can cause changes with sleep, appetite, and libido.

Since healthy cells can be damaged during radiation therapy on the brain, cognitive impairments may develop. This may include trouble concentrating, difficultly learning new skills, and problems with memory. In patients who are children, cognitive side effects may be more severe and long lasting because their brains are still developing.