Question category: Neurology
A 44 year old female presents with a headache. This has been present for a couple of days and has been gradually gettting worse. It is mainly localised behind and around the eye. She states that her right eye is also painful. She is otherwise fit and well although she gives a history of having had 4 miscarriages. On examination there is evidence of chemosis, proptosis and periorbital oedema of the right eye. There is also a lateral gaze palsy. Which of the following is the most likely diagnosis?