What could be the cause of increased T2 and FLAIR perilesional signal in this case?
Lesional mass effect compresses the adjacent parenchymal vessels, resulting in white matter ischemic changes and subsequent gliosis. Alternatively, this may represent oedema.
A well-defined rounded cystic lesion is seen involving the subcortical white matter of the right temporal pole. It follows fluid signal intensity on all sequences with CSF-like high T2 signal and complete central suppression on FLAIR. It is surrounded by moderate perilesional increased T2 signal. No overlying cortical involvement. On high-resolution T2 weighted images, additional smaller cystic/tubular fluid-filled lesions of similar MR appearances are present, likely representing dilated perivascular spaces.
No perilesional or intralesional enhancement is seen after contrast administration and no signal loss on SWI to suggest calcification or haemorrhage.
Anterior to the lesion a prominent loop of the right middle cerebral artery (best seen on axial high-resolution T2, coronal T2 and sagittal post-contrast T1) indents the adjacent cortex.