Rim sign (spinal cord metastasis)

The rim sign has been described as a helpful MRI sign of spinal cord metastases, enabling them to be distinguished from other enhancing spinal cord lesions (e.g. ependymoma and astrocytoma).

Radiographic features

MRI

The rim sign is seen on sagittal post contrast T1 weighted imaging of the spinal cord and appears as a thin line of increased enhancement around the margins of the lesion. Superiorly and/or inferiorly it may extend into the cord as a region of ill-defined enhancement (flame sign).

It has been reported that in 90% of studies of patients who have spinal cord metastases one or both of the rim and flame sign are present and that this finding is fairly specific .

Differential diagnosis

Spinal hemangioblastomas sometimes demonstrate incomplete rim signs .