Clinics in diagnostic imaging (91). Subarachnoid haemorrhage.

Computed tomography (CT) is the initial radiological investigation of patients with an acute neurological event. A 64-year-old woman presenting with generalised weakness and headache for two days was diagnosed on CT to have subarachnoid haemorrhage. Digital subtraction angiography confirmed the cause to be a ruptured posterior communicating artery aneurysm. The patient was treated by neuroradiological intervention using occlusive coils. The CT features of subarachnoid haemorrhage are discussed. Accurate CT interpretation is essential to direct appropriate investigations and management in patients with stroke, particularly as acute cerebral infarction may occasionally mimic subarachnoid haemorrhage. The role of magnetic resonance (MR) imaging in evaluation of cerebral infarct is also discussed.