I respect the medical pro standpoint, but from a fighters standpoint: If my hands and feet are wrapped in my opponent's guard, I have one weapon left. The head can be trained just like a hand and foot, if used by an amateur they can hurt themselves badly, but if you know what you're doing then you can use it properly.
Proper headbutt form: Use the crown of the head to strike the face of your opponent. That way you won't damage the soft spots on your face or the base of your spine.
Sig by Toxic
Barnett - Toquinho -Werdum - "Nurmie"
Z. Gurgel - Morango - Rocha - Tiequan