Neurologycommon
A 41-year-old woman presents with a headache that began abruptly while she was lifting weights at the gym yesterday evening, reaching maximum intensity within seconds; she describes it as the worst headache of her life. She vomited twice. It has eased a little with paracetamol but persists 20 hours later. She has no history of migraine. On examination she is alert, has mild neck stiffness and no focal neurological deficit. A non-contrast computed tomography scan of the brain, performed on arrival, is reported as normal.
Which one of the following is the most appropriate next step?