Bright rim sign (DNET)

Last revised by Frank Gaillard on 4 Oct 2023

The bright rim sign, also known as the hyperintense ring sign, is an MRI sign described most frequently in dysembryoplastic neuroepithelial tumors (DNET) but is also seen in some other tumors.


Although the sign is most associated with DNETs, and should probably be reserved in cases where DNET is the suspected diagnosis, it is also seen in other pathologies such as myxoid glioneuronal tumors 3.

It is also visually equivalent to T2/FLAIR mismatch sign seen in some astrocytomas, IDH-mutant.


On pathologic examination, this bright rim sign corresponds to glioneuronal elements loosely packed at the margin of the tumor surrounding an area so replete with fluid that it partially suppresses on FLAIR 1.

Radiographic features


It is described as a well-defined rim of high signal around the DNET on FLAIR sequences. This T2/FLAIR hyperintense ring, whether complete or incomplete, is fairly sensitive and specific for DNET 2. On postoperative imaging, this sign may be a helpful clue for residual tumor or tumor recurrence 2

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