There is dense subarachnoid blood, predominantly in the anterior interhemispheric fissure, also in both sylvian fissures, and in the suprasellar cistern extending to the left side of the interpeduncular cistern. No intraparenchymal or intraventricular extension.
Ventricles and cortical sulci within normal limits for a patient of this age. No evidence of hydrocephalus.
No evidence of acute vascular territory infarct.
Visualised paranasal sinuses and mastoid air cells are well-aerated. No concerning bone lesion.
CTA COW (aortic arch to vertex)
There is a 1.1 x 0.8.x 0.8 cm lobulated aneurysm arising from the anterior communicating artery. This has a wide - 5 mm - neck. It fills from supply via the left A1 segment.
The right A1 segment is hypoplastic.
Both the left and right A2 segments arise from the base of the aneurysm.
No other aneurysm is demonstrated.
Conclusion:
Lobulated wide neck anterior commuting artery aneurysm.
Acute subarachnoid haemorrhage with distribution of blood compatible with rupture of the ACom aneurysm.