Not Sure How it is Caused

When I was talking to one of my friends on the phone the other day, she told me that she had just found out that her son could have dyslexia.  I asked her how they found out, and she told me about how they had taken him to see the doctor.  I asked her if they knew what causes dyslexia, and she told me that it is a neurological defect, and they are not sure when it happens for sure.  They just know that he could have it, and they will have to start taking him to treatment.  I could tell that she was very upset.