Huge subarachnoid haemorrhage – CT angio

Subarachnoid haemorrhage and berry aneurysm. The non-contrast CT on the left shows a massive subarachnoid haemorrhage – you can see high attenuation haemorrhage in the classic ‘five-pointed star’ pattern. You will also notice that the majority of the blood appears to be located anteriorly, a finding which often provides a clue to the source of the haemorrhage. In this case, the CT angiogram on the right clearly demonstrates an aneurysm arising from the anterior communicating artery (arrow) – the portion of the circle of Willis that connects the two anterior cerebral arteries (ACA). The MCA and basilar arteries are also labeled.