I hadn't heard this one, but according to a 2005 article, George Clooney sustained a Traumatic Brain Injury while filming the movie "Syriana." Click below to read the article:
George Clooney and TBI
On a related note, George Clooney's aunt Betty Clooney, died of brain trauma caused by an aneurysm. The Betty Clooney Foundation (est. 1983) in Long Beach, CA helps people with cognitive disabilities. Click HERE for details on the foundation.