He said hemicraniectomy is done as soon as the patient is diagnosed. The surgeons remove the skull flap, drain the blood from the brain and clip off the aneurysm to prevent additional bleeding. Traditionally, the skull flap is reattached at this point. In the hemicraniectomy, the flap is removed and sewn under the skin of the abdomen, where it stays until it is reattached. The brain itself is covered by a leathery substance called dura.
Surgeons add a graft to the dura so that it can expand if necessary.
Smith said the brain can swell days after the initial injury from the aneurysm. Vasospasm, which occurs when the blood vessels in the brain constrict, also takes several days to develop. Treatment for vasoconstriction calls for increasing blood pressure and fluid volume, both of which are dangerous in a person whose brain is swelling. Conversely, treating swollen brains requires therapies that cause constriction of blood vessels, he said. The brain flap is reattached nine to 12 weeks after initial surgery, said Smith.