Medical evidences demonstrate that football headers can cause damage to the brain in football players especially as the ball moves at high rates of speed .
PSV Eindhoven coach Phillip Cocu has criticised his side's lack of concentration and motivation after they let slip yet another lead in a Dutch league.
First half goals handed Ajax a 2-0 away win at fellow frontrunners Heracles Almelo on Saturday and a two-point advantage at the top of the Dutch league.