Patients with uncontrolled epilepsy have an evaluation that usually begins with electrical studies of the surface of the brain.... A hole is drilled in the skull, and electrical measurements made from within the depths of the brain. A large flap of the skull is then lifted up, electrodes placed on the surface of the brain, and the flap sewn back into place so that more electrical studies can be done. The risks... are far greater than those associated with the ventricular taps needed for hormone studies.... If the team of doctors.. can help... areas of the brain that are sending 'bad' signals would be identified and removed... large portions of the brain might be taken away.

The Fabric of Mind (1985)