Pseudotumour of the corpus callosum due to subarachnoid haemorrhage from pericallosal aneurysm.

Two patients were scanned 2-5 weeks following onset of subarachnoid haemorrhage. A similar CT appearance was seen in each case. A ring enhancing mass lesion was present within the corpus callosum, suggesting an underlying tumour. However subsequent angiography showed that each case was in fact due to rupture of a pericallosal artery aneurysm. The enhancing membrane of the haematoma gave the false impression of a corpus callosum tumour.