Such a finding is mostly made by observing someone's behavior. However, experts say a brain autopsy could help support such a diagnosis by showing patterns of brain damage consistent with a persistent vegetative state.

"If there's very extensive brain injury, it would be hard to accept another diagnosis as being conceivable," said Dr. Roger Albin, a neurology professor and director of the brain bank at the University of Michigan Medical School.

An autopsy can detect whether bones have broken and healed, even many years ago. It can't determine when the injury occurred. But comparisons with X-rays from previous dates could help get a fix on that.

© 2005 Associated Press.

Editor's note: