Personality changes can include many things. Most of these changes will be based on deficiencies resulting from brain injuries. They will contribute to associated behaviors and these behaviors will contribute to changes in a personality.
Becoming 'stuck' on a notification such as the 'dog with a bone' attitude is one such change; mood changes are another. A change that I found rather disconcerting was my partner's tendency, following his injury, to make up stories. This, I believe is the result of his short-term memory difficulties – if he can not remember the whole story, he makes up what he can not remember. In spite of the fact that he does not appear to remember the original story, he does remember his 'made up' version and will argu it vehemently.
While doing my research, I read that personality changes will sometimes be an exaggeration of the person's pre-injury personality (an amplification of their negative behaviors increased by frustration and a sense of loss); or at other times the personality change can be a complete reversal of the pre-injury personality. ie Where once the person may have been easy-going and thoughtful, they may now be easily angered and self-absorbed.
Also, according to my research, some changes may be due to the brain injured person's copying style and responses to stressful situations pre-injury, ie their adaptability to change, or their tendencies towards minimizing or magnifying their emotional situation.
In frontal lobe injuries, the changes are mostly in the emotional and behavioral area with some relating to cognitive impairments. In my partner's case, a couple of the behavioral shortcomings he has left with are his difficulty to tolerate frustrations and his decreed social skills. One of the symptoms of this is he does not participate in conversations as he once did.
In the words of a brain injury survivor – 'each person has personality traits, habits, strengths and weaknesses before they sustain a traumatic brain injury. If a person was disorganized before their injury, they'll look like a train wreck after; if they were cranky before, they'll be ruthless after; if they were low maintenance before, they'll completely disengage after; if they were extremely bright before, they'll have some 'cognitive reserves' to help make up for the shortcomings; if they were of low or average intelligence, they're going to struggle to keep up; if they had interpersonal problems before, they'll have chaotic relationships after. ' She said each of us is flawed in some way and a brain injury makes those flaws worse.
Extreme fatigue is another change. When my partner required what seemed to be an excess amount of sleep, I assumed his body was still healing from his many other injuries. But through my research, I discovered that fatigue is a very common symptom of brain injury. Because the brain is not working in the same way, the survivor has to work much harder to be able to accomplish less than what he once did. Also the extra effort that is required to compensate for short-term memory loss has an intense fatiguing effect. Added to this is the effort of trying to keep up with a conversation; the difficulty of paying attention or analyzing what is being said, thinking of a response and trying to look interested all at the same time.
And then there is the change that is difficult to describe. There is a song by Johnny Reid about an angel who has fallen from heaven. Before my partner's accident, he used to say I was his angel. But something has been lost since his brain injury. I believe the caring is still there but the ability to show it, and certainly the ability to articulate it, is gone. It is another change in his personality.