A 35 year old woman presents to her GP with a several month history of pounding headache which is at its worst in the morning. She also reports feeling nauseated. She has a background of asthma and has a BMI of 35. Neurological examination but fundoscopy shows swelling of the optic disc. Brain imaging is unremarkable and LP shows raised opening pressure but is otherwise normal. Given the likely diagnosis what is the most appropriate treatment?