I was mistaken. According to the CNN report just now, Kennedy did have surgery, in May, to remove the tumor, and underwent chemo and radiation therapy subsequently. Because a seizure led to the discovery of the tumor he was on anti-seizure medication as a prophylactic measure. He will have a new brain scan in the hospital to determine if any of the tumor has regenerated. Chances are, also, that the tumor and subsequent removal created what's called a "focal point" that can, when activated, lead to further seizures.
The article also said that he left the Hall in a wheelchair, not a stretcher, as previously reported.