What typical MRI characteristics are associated with meningiomas?

Meningiomas are typically associated with extra-axial lesions, which means they are located outside the brain parenchyma or the intra-axial structures of the brain itself. On MRI, meningiomas usually present as well-circumscribed masses that are isointense or slightly hyperintense to brain tissue on T2-weighted images and can enhance significantly with contrast due to their extra-axial location and dural origin. This characteristic distinction helps in differentiating meningiomas from other types of brain tumors, which may invade the brain tissue and appear as intra-axial lesions.

When evaluating other characteristics mentioned in the options, intra-axial lesions typically refer to tumors that originate within the brain substance itself, which does not apply to meningiomas. Diffuse infiltrative lesions are those that tend to invade surrounding tissues and do not have clear borders; meningiomas are well-defined due to their origin from the dura mater, showing a clear demarcation from adjacent brain tissue. Vascular malformations, such as arteriovenous malformations, are entirely different entities and do not share the typical imaging features seen with meningiomas.

Thus, the defining characteristic of meningiomas being well-circ