Observational study of headache among adult patients presenting to emergency departments

We enrolled 4536 patients (67 hospitals, 10 countries). ‘Thunderclap’ onset was noted for 14.2% of cases (644/4536). Headache was rated as severe in 27.2% (1235/4536). New neurological examination findings were uncommon (3.2%; 147/4536). Head CT was performed in 36.6% of patients (1661/4536), of which 9.9% showed clinically important pathology (165/1661). There was substantial variation in CT scan utilization between countries (15.9%-75.0%). More than 30 different diagnoses were made. Presumed non-migraine benign headache accounted for 45.4% of cases (2058/4536) with another 24.3% classified as migraine (1101/4536). A small sub-group have a serious cause for their headache (7.1%; 323/4536) with subarachnoid haemorrhage (SAH), stroke, neoplasm, non-SAH intracranial haemorrhage/haematoma and meningitis accounting for about 1% each. Most patients were treated with simple analgesics (paracetamol, aspirin or non-steroidal anti-inflammatory agents). Most patients were discharged home (83.8%; 3792/4526). In-hospital mortality was 0.3% (11/4526).