Contrast enhancement following infarct
On CT, contrast enhancement following infarct occurs in the subacute stage, and generally starts towards the end of the first week. Peak enhancement occurs at week 2 and 3, and gradually fades over the following weeks. On MRI, enhancement can be seen as early as day 1 following ictus, although available data is not as extensive as for CT.
Contrast enhancement can take the form of a gyriform pattern, but also occurs in the deep parenchyma. It is likely due to a combination of blood brain barrier breakdown, neovascularisation and impaired autoregulation. This was previously referred to as 'luxury perfusion', and can also be seen at interventional procedures for acute stroke, where the already infarcted brain demonstrates parenchymal staining. On occasions, the contrast enhancement can have a confusing and bizarre appearance, even mimicking tumours. This is especially so if prior knowledge of the infarct is not known.
At CT, enhancement is generally seen at a stage where much of the mass effect is resolving. This is a useful radiological sign, as an enhancing lesion with mass effect is not likely due to a subacute infarct, and more likely a tumour.