A 47 year old woman presented to the emergency department with a two week history of a global headache and a one day history of vomiting, photophobia, and blurred vision. She also reported night sweats during that period. Her general practitioner had prescribed simple analgesics for the headache, but they had had little effect.

She had been healthy previously and was on no regular medication. General examination revealed temperature 36.8 °C, pulse 84 per minute, and BP 120/90 mm Hg, bilateral subconjunctival haemorrhages, and left axillary lymphadenopathy. Chest and abdominal examinations were unremarkable. …