What Causes Terrible Night Mares?

My husband is a Korean War Veteran, Marine - UDT in fact. Walt started having severe PTSD, with severe nightmares in 2007. He would frequently bang his head in the process, on the floor, wall or whatever happened to be there. One night during a nightmare he threw himself out of the bed and caught his ear on the night stand. He nicked an artery during this nightmare episode,( hospital documented). These nightmares went on up until he had a hemorrhagic stroke, July 13, 2012. Funny the nightmares stopped after the stroke. I am fighting the VA for his full benefits. I am trying to establish the fact that continual blows to the head can certainly be a contributing factor to a stroke. Could you share some information regarding blows to the head being a contributing factor stroke