A penetrating head injury, or open head injury, is a head injury in which the dura mater, the outer layer of the meninges, is breached.University of Vermont College of Medicine. http://web.archive.org/web/20050309165318/http://cats.med.uvm.edu/cats_teachingmod/pathology/path302/np/home/neuroindex.html "Neuropathology: Trauma to the CNS." Accessed through web archive. Retrieved on February 6, 2007.