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Background
Dural tail sign (DTS), first described by Wilms in 1989, is the thickening and enhancement of the dura mater seen adjacent to various CNS lesions on contrast enhanced T1-weighted MRI. Three criteria must be met for a positive dural tail sign. It must be seen on at least two successive images (or more depending on slice thickness), it must smoothly taper away from the tumor, and it must enhance to a greater degree than the tumor. Although originally considered pathognomonic for meningioma, it has since been reported in a wide range of diseases including CNS lymphoma, metastases, neuroma and granulomatous disorders. Despite not being pathognomonic, DTS is most commonly seen in meningioma with a reported frequency of 52 - 72%. The pathology of DTS is still debated and is likely multifactorial. Local inflammation, hypervascularity due to vessel blockage by tumor, and tumor extension within the dura have all been proposed as causes.

Educational Goals / Teaching Points
Describe dural tail sign and the criteria that must be met to constitute a “positive” instance. Recognize the differential diagnosis associated with dural tail sign. Understand proposed pathophysiological basis for dural tail sign. Review the importance of dural tail sign for surgical management.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Although originally used for both spinal and intracranial meningioma, today the term “dural tail sign” is exclusively used for intracranial lesions. Though it is no longer considered pathognomonic for meningioma, it may be helpful in suggesting the diagnosis. Additionally, recent research has shown up to 88.3% of dural tails are invaded by tumor, and there is a significant association between dural enhancement and malignancy of the underlying lesion. Given this association, DTS is an important finding to note on radiological reports due to the implications it has for surgical resection.

Conclusion
DTS is a thickening and enhancement of the dura adjacent to some intracranial lesions on contrast enhanced T1 MR images. DTS was originally thought to be a sensitive finding in meningioma though contemporary research has shown it is likely present in only about 60% of these lesions. It also may be seen with non-meningiomatous malignancies such as CNS lymphoma and metastases as well as non-malignant lesions such as sarcoidosis. Still, the sign is helpful in suggesting the diagnosis of meningioma. The exact etiology is incompletely understood but it has been associated with local invasion in the literature and thus has implications when considering surgical management.