i have been getting headaches for a few years and was told i had an arachnoid cyst but only a small one that was about 18mnths ago and have been taking mertazipine and amytriptiline and ibroprufen but over the last few weeks my headaches have got considerably worse and the headache i hav now has lasted over a week and i feel constantly sick and have been sick quite alot in the last few days which i think is from my headaches do i need to go back and have another scan? is it likely to be that the cyst has grown?