Acute subarachnoid haemorrhage
Acute subarachnoid haemorrhage. This noncontrast image shows the classic appearance of an acute subarachnoid haemorrhage (SAH) – high density blood surrounding the circle of Willis (where the majority of berry aneurysms arise). The shape of the high attenuation abnormality is often likened to a 5-pointed star. Note that this patient has developed one of the potential complications of SAH – obstructive hydrocephalus. The temporal horns of the lateral ventricles are abnormally dilated.