While doctors know that Sen. Ted Kennedy has the most common form of brain cancer, the positioning, type and size of the tumor will determine the degree of danger and side effects from surgery, CNN reports. Kennedy’s glioma is in the left parietal lobe, which is involved in speaking and understanding speech as well as motor control for the body's right side.
Experts say surgery in such an area near “high-risk real estate” is itself dangerous: "It's nearly impossible to tell what is tumor and what is brain cells, because this is a tumor of the brain cells," said one neurosurgeon. As a result, the surgeries themselves can sometimes cause brain damage. Normal prognosis ranges from months to 5 years, CNN adds.