What Causes Frequent Severe Headaches?

hello Doctor, my name is Amit (from India). My sister has been experiencing severe headache for the last six months. She gets frequent (two to four times a day) attacks of severe headache, they start slowly but quickly becomes severe. During this time, she feels as if something is hitting from inside her central part of the head/over the brain. She has been supposedly tested and being treated for chronic migraine and bacterial infection, but no improvement. We are have consulted some of the renowned neurologists in India, including doctors are AIMMS and Appolo. None of them have been been to diagnose the problem. We are not at another hospital, where the doctor is saying that the problem might be because of some sort of Sinus infection. But given the type of headache, I am not sure if that cause could explain the headache. What would be your advise? I am also thinking that she might have a brain worm, would that be a possibility? Thanks