Defending a traditional practice in the modern era: The use of lumbar puncture in the investigation of subarachnoid haemorrhage.

Introduction: Acute severe headache is a common medical presentation, and a common area of diagnostic uncertainty. Subarachnoid haemorrhage (SAH) is the cause in a minority of patients and has a high rate of morbidity and mortality. Therefore, its conclusive diagnosis with computed tomography (CT) or lumbar puncture (LP) is paramount.