There is evidence that significant head injury may initiate cerebral disease. Appropriate equipment and supervision is needed and parents should take all precautions, make sure to use the appropriate safety equipment when participating in football, boxing, soccer or sports where head injury may be a factor.
Parents should be diligent in having their boys wear helmets when riding a bicycle, skiing, etc..
It is recommended that your child avoid participating in sports that are known to cause significant head injury and to always wear protective head gear when enjoying sports and activities.
Article from the National Library of Medicine on head trauma