Dural tail sign | Radiology Signs

Answer:

The dural tail sign is a tapering, enhancing extension of thickened dura extending away from the margin of an extra-axial mass on post-contrast T1-weighted images. It is a classic feature of meningioma, present in roughly 60 to 70 per cent of cases, but it is not specific and has been reported with dural metastases, lymphoma, sarcoidosis, tuberculosis, extramedullary haematopoiesis, chloroma, schwannoma, glioblastoma abutting the dura and even with idiopathic hypertrophic pachymeningitis. Its practical value is in localisation rather than histology: it confirms that the lesion is extra-axial and dural-based, which together with a broad dural base, a cerebrospinal fluid cleft, cortical buckling and displaced pial vessels separates a meningioma from an intra-axial mass. Histologically the tail may contain tumour cells or may be purely reactive vascular dura, which is why current surgical practice removes an adjacent margin of dura where feasible, the basis of the Simpson grading of resection completeness. The sign should be reported alongside features that raise concern for an atypical or higher-grade lesion, such as an indistinct brain-tumour interface, marked peritumoural oedema, heterogeneous enhancement, mushrooming growth and bone destruction rather than the usual hyperostosis.

Why is it called so?

The thickened enhancing dura tapers away from the mass like the tail of an animal.

Pathophysiology

Two mechanisms produce the tail. In many cases the adjacent dura is thickened by reactive hypervascularity and oedema, without tumour cells, as a response to the meningeal blood supply that the tumour has recruited; the dura has no blood-brain barrier so it enhances avidly and the recruited vessels amplify this. In other cases the tail represents genuine dural invasion by tumour spreading along the meningeal planes. Because the two cannot be distinguished by imaging, the tail predicts neither behaviour nor grade. Meningiomas themselves arise from arachnoid cap cells of the arachnoid granulations, which explains their preference for the parasagittal convexity, sphenoid ridge, olfactory groove and tuberculum sellae, and their supply from meningeal rather than cerebral arteries.

Alternative names: Meningeal tail sign; flare sign

Other associated named signs: Cerebrospinal fluid cleft sign, the sunburst vascular pattern at angiography, and hyperostosis of the adjacent inner table

References

1. Guermazi A, Lafitte F, Miaux Y, Adem C, Bonneville JF, Chiras J. The dural tail sign–beyond meningioma. Clin Radiol. 2005;60(2):171-88. PMID: 15664571.