MRI in acute subarachnoid haemorrhage; findings with a standardised stroke protocol.

There is doubt as to whether acute haemorrhage is visible on MRI. We carried out MRI within 6 h of symptom onset on five patients with minor (low Hunt and Hess grades 1 or 2) subarachnoid haemorrhage (SAH) diagnosed by CT to search for any specific pattern. We used our standard stroke MRI protocol, including multiecho proton density (PD)- and T2-weighted images, echoplanar (EPI) diffusion- (DWI) and perfusion- (PWI) weighted imaging, and MRA. In all cases SAH was clearly visible on PD-weighted images with a short TE. In four patients it caused a low-signal rim on the T2*-weighted source images of PWI, and DWI revealed high signal in SAH. In the fifth patient SAH was perimesencephalic; susceptibility effects from the skull base made it impossible to detect SAH on EPI DWI and T2*-weighted images. Perfusion maps were normal in all cases. MRA and conventional angiography revealed an aneurysm in only one patient. Stroke MRI within 6 h of SAH thus shows a characteristic pattern.