A 46-year-old right-handed man presented to the emergency department with a 1-week history of headache. The headache was bilateral, predominantly posterior, worsened transiently on Valsalva manoeuvre and was refractory to simple analgesia. It did not vary with posture or time of day. He felt nauseated but had not vomited. There were no visual symptoms and specifically no blurring, obscuration or diplopia.
A few hours before presenting, there had been an unwitnessed collapse without prodrome, and he sustained a soft tissue injury to his neck. His partner had found him confused and drowsy and so called an ambulance.
He had previous episodic migraine, depression and gastro-oesophageal reflux. Borderline hypertension (143/90 mmHg) had been found at a neurology consultation for headache 18 months before; an MR scan of the brain at this time was normal.
He smoked 20 cigarettes per day and drank alcohol excessively (100 units per week). He did not use…