One of the main causes of sinus drainage is simply being alive. Every day the human body produces several liters of sinus fluid and mucus, and all of that natural liquid must go somewhere.
It is a area of tenderness of the scalp in which people also sometimes feel stabbing headaches. Others just feel very sore and tender to the touch. It is felt to be caused by irritation of the connective tissue which attaches the muscles of the scalp to the skull (cranium).
Tenderness on the top of the head and scalp can also be caused by occipital neuralgia, a condition caused by inflammation of the nerves that travel from the spinal cord to the top of the head become inflamed or injured, according to WebMD.