Some experts have written that fabricated posttraumatic stress disorder should be considered when a patient's symptoms are suspicious or unusual. These experts (specifically, the "American Psychiatric Association" DSM IV manual; expert witnesses such as Eli S. Chesen, M.D.; and the textbook "Comprehensive Textbook of Psychiatry," by Freedman & Kaplan) have suggested that it should raise a "red flag" if a patient claims to be suffering from both PTSD and a Traumatic Brain Injury (TBI) as a result of the same accident. They suggest that TBI - a physical injury to the brain - causes amnesia, or memory loss, for the event that caused the brain injury. Without memory of the traumatic event, they reason, a patient probably could not experience certain symptoms of PTSD, like nightmares or flashbacks about the event, because they do not remember what happened. They conclude that in typical cases, Traumatic Brain Injury "trumps" the diagnosis of PTSD.