Thirty years ago, Kerri Walker, now a coordinator for a domestic violence shelter in Phoenix, found herself inexplicably driving down the left side of the road into oncoming traffic. “It felt totally normal,” she said, recalling how she was oblivious to the danger. Walker escaped an accident that day, but looking back now, it was the first clue she had an undiagnosed brain injury. At the time, Walker, 51, was in the throes of an abusive relationship, she said.