Dural tail sign adjacent to different intracranial lesions on contrast-enhanced MR images

Introduction: The aim of this study is to determine the prevalence of dural tail sign (DTS) in meningiomas, glioblastomas multiforme, metastasis, pituitary macro-adenomas, acoustic neuromas, medulloblastomas, lymphomas and Wegener’s granulomatosis, and to reveal if DTS is specifi c for meningiomas. Methods: In this retrospective, cross sectional study 96 patients were included with 95 intracranial and 1 extracranial lesions. The study was conducted in the period from January 2008 to May 2010 and the group pattern was made consecutively. The patients underwent surgery and all 96 lesions were examined by histopathology analysis. DTS was analysed on contrast T1- weighted spin echo images after injection of 0.1 mmol/kg gadolinium contrast medium. The presence of this sign was defi ned using Goldsher et al’s criteria. Results: Histopathology results of the 96 lesions revealed the presence of: 35 meningiomas, 25 glioblastomas multiforme, 13 metastasis, 10 pituitary adenomas, 5 acoustic neuromas, 4 medulloblastomas, 3 lymphomas and 1 Wegener’s granulomatosis. On the contrast-enhanced T1 MR images, DTS was noted in 31 (32.3%) lesions, in the following histological samples: meningioma, GBM, adenoma, schwannoma, medulloblastoma and Wegener’s granulomatosis, while in the cases of metastasis and lymphomas DTS was not noted. We found the dural tail sign to have a sensitivity of 68.6% and specifi city of 88.5% in the diagnosis of meningioma. Conclusion: The dural tail is a common but not a pathognomic sign of meningioma on contrast-enhanced T1 MR images. Other intracranial lesions, such as glioblastoma multiforme, pituitary adenoma, schwannoma, medulloblastoma and Wegener’s granulomatosis may also be represented with this sign. © 2011 All rights reserved


Introduction
"Dural tail sign" (DTS), also known as the "meningeal sign", "dural thickening" or "fl are sign", was fi rst described by Wilm et al. in 1989. It is a linear thickening of the dura adjacent to an intracranial pathology on contrast-enhanced T1 MR images (1) (Figures 1, 2, 3). Th e exact histological nature of DTS is controversial. It was initially proposed that DTS is a result of direct tumour extension within or at the surface of the dural membrane (1,2), but some other authors have been able to show little or no direct tumour in-volvement. Th ey suggested that DTS might be attributed to fi brous tissues with loose connective tissue proliferation, hypervascular reaction and vascular dilatation (2,3). It is possible that two mechanisms (tumour invasion and hypervascular reaction) may be responsible for DTS (4). In 1990, Goldsher et al. (2) devised the following three radiological criteria to reliably establish the presence or absence of DTS: 1) Th e tail should be identifi ed on two successive sections through the tumour, 2) the tail should taper smoothly away from the tumour, and 3) the tail must have an enhancement greater than that of the tumour itself. If present, as imaging slices tend to be less than 5 mm, there should always be at least three sections showing the dural tail, depending on the slice thickness (5). DTS was fi rst thought to be pathognomonic of SVJETLANA MUJAGIĆ ET AL.: DURAL TAIL SIGN ADJACENT TO DIFFERENT INTRACRANIAL LESIONS ON CONTRAST-ENHANCED MR IMAGES meningioma, but many later studies demonstrated DTS adjacent to various intra and extra-cranial pathologies as well as in spinal lesions (4,6). Th e aim of this study is to determine the prevalence of DTS in meningiomas and some other intracranial lesions, and to reveal if DTS is specifi c for meningiomas.

Patients
In this cross-sectional study, we retrospectively examined the magnetic resonance fi ndings of 95 intracranial lesions and 1 extracranial lesion in 96 patients (mean age 51.9 years, ranging from 5 to 76 years) with no history of previous intracranial surgery, trauma or intracranial haemorrhage. In the study, which was conducted in the period from January 2008 to May 2010, we included all patients with discovered intracranial and extracranial lesions which may be associated with DTS. We studied patients with meningiomas, glioblastomas multiforme, metastasis, pituitary macroadenomas, acoustic neuromas, medulloblastomas, lymphomas and Wegener's granulomatosis. We did not have patients with some other lesions which could be associated with DTS such as chloroma, multiple myeloma, aspergillosis, chordoma, pituitary apoplexy, hypophysitis, pleomorphic xanthoastrocytoma, eosinophilic granuloma, Erdheim-Chester disease, sarcoidosis, giant posterior cerebral artery aneurysm, dural cavernous hemangioma, hemangiopericytoma. We excluded patients with cerebellar stroke. All patients included in this study underwent surgery and all of 96 lesions were examined by histopathology analysis.

Procedure
MR were performed at the Department of Radiology and Nuclear Medicine, surgical treatment at the Department of Neurosurgery, and pathohistological analysis at the Department of Pathology of the Polyclinic for Laboratory Diagnostics of the University Clinical Centre, Tuzla. MRI was performed on a 1.5 T MR scanner (Avanto, Siemens, Erlangen Germany). DTS was analysed on contrast T1-weighted spin echo images aft er 0.1mmol/kg gadolinium contrast medium injection with the following parameters: TR 500 ms, TE 8.1 ms, 5mm section thickness, 230 mm fi eld of view, 256x256 matrix. MR images were obtained on three planes: axial, coronal and sagital plane. Th e presence of DTS was defi ned using Goldsher et al's criteria (2): a) the tail was identifi ed on two successive sections through the tumour, b) the tail was taper smoothly away from the tumour, c) the tail had an enhancement greater than that of the tumour itself. Th e MR fi ndings were interpreted by one of two radiologists.

Statistical analysis
Th e sensitivity and specifi city (95% confidence interval-CI) of DTS in diagnosis of meningioma were calculated with diagnostic test analysis (2 by 2) in "Arcus Quickstat Biomedical" soft ware (Version 1.0-build 88; 1997).

Discussion
Th e aim and task of every radiologist is not only to reveal intracranial pathology but also to give a diagnosis of the revealed lesion as close as possible to the histopathology diagnosis. Th e majority of meningiomas exhibit highly stereotypic imaging characteristics, when combined with their select intracranial dural-adherent localizations, which oft en facilitates their diagnosis, especially on MRI (7). However, it may sometimes be diffi cult to diff erentiate between meninigomas and other tumours in some intracranial locations. For example, a meningioma in the CPA near to the internal auditory canal may be mistaken for an acoustic neurinoma, while a meningioma in the parasellar region may be mistaken for a pituitary adenoma. DTS describes a linear enhancement along the dura mater on contrast T1-weighted resonance images (Figure 1, 2, 3). Th is sign is considered as common and useful for distinguishing meningioma from other intracranial lesions and was at fi rst thought to be pathognomonic of meningioma. Many later studies demonstrated the presence of this sign adjacent to other intra-and extra-cranial pathologies: lymphoma, chloroma, metastasis, multiple myeloma, GBM, aspergillosis, chordoma, schwannoma, pituitary adenoma, pituitary apoplexy, hypophysitis, pleomorphic xanthoastrocytoma, eosinophilic granuloma, Wegener's granulomatosis, Erdheim-Chester disease, sarcoidosis, medulloblastoma, giant posterior cerebral artery aneurysm, dural cavernous hemangioma, hemangioperi-FIGURE 1. The coronal contrast-enhanced T1-weighted image shows a right temporal meningioma with the "dural tail sign" below and lateral to the lesion, along the right tentorium.     by Aoki et al. (30). For diagnosis of meningioma, we found that DTS has a specifi city of 88.5%. Th is specifi city is 5.52% lower than the specifi city noted by Rokni-Yazdi and Sotoudeh (12). DTS has been reported in only a few gliomas. In the published literature, we found only eight cases of GBM associated with DTS (5,9,33,34). In all eight cases, the dura mater had a normal appearance on the histological examination, without tumoural invasion (9,33). Also, because GBM is rarely fed by the vessels of the dura mater, the enhanced DTS is not likely to develop from vascular congestion or proliferation (5). In our study we found DTS in 2 of 25 GBM cases (Figure 3, 4, 5, 6, 7). In one of the GBM, the fi rst MR exam showed nonspecifi c radiological fi ndings for GBM. Th e tumour appeared as a few smaller intra-axial lesions in the right frontal lobe, slightly hypointense on the T1-weighted image and slightly hyperintense on the T2-weighted image, with strongly contrast enhancement and linear enhancement along the dura mater around the lesions (Figure 5, 6). On the second MRI, control scans showed the classic appearance of GBM (Figure 7). Th e diagnosis of GBM was confi rmed by the pathologic examinations. An acoustic neuroma, which arises from the vestibular portion of the 8th cranial nerve, is the most common of all CPA neoplasms, followed by meningiomas. Aoki et al. (30) in their study reported 4 meningiomas in the CPA with linear enhancement along the internal auditory canal. It was suggested that this DTS might be useful in the diff erential diagnosis of dural-based and other neoplasms. Some other studies reported DTS adjacent to an acoustic neuroma that can mimic a meningioma, but its hypersignal intensity in the T2-weighted image and narrower dural attach-FIGURE 11. The coronal contrast-enhanced T1-weighted image shows a homogeneously enhancing sellar and left parasellar mass with a dural tail sign. The lesion corresponds to a pituitary macro-adenoma. ment can diff erentiate this tumour from a meningioma (6,10,11,35). In our study 7 tumours were located in the CPA (5 acoustic neuromas and 2 meningiomas). We noted DTS in both meningiomas ( Figure 8) and 1 neuroma (Figure 9, 10). Although DTS is a useful sign for diff erentiating between pituitary adenomas and meninigomas in the sellar region, in this case DTS is also not specifi c for meningioma. DTS can be seen adjacent to pituitary adenomas in 30% of cases. Th e pathophysiology of dural thickening in a pituitary adenoma is not clear. It is probably the result of venous congestion and meningeal infl ammation (6,17,36). Cases of DTS with pituitary adenomas have been reported mainly with haemorrhagic adenomas (18). In study conducted by Catin et al. (36), DTS was common with both haemorrhagic and non-haemorrhagic adenomas. DTS mostly extends into the planum sphenoidale and carotid sulcus. Catin et al. noted slight dural thickening in the presellar region in 50% and marked thickening in 40% of all cases of pituitary adenomas (36,17,36). In our study we noted DTS in 2 (20%) of 10 pituitary adenomas ( Figure 11). In the published literature we found DTS adjacent to medulloblastoma in two cases (37,38). In our study we noted DTS in 1 of 4 medulloblastomas (Figure 12). Wegener's granulomatosis of the paranasal sinuses, with cerebral and meningeal involvement, may present with DTS (24,40). In our study we also had one patient with Wegener's granulomatosis with DTS present (Figure 13). DTS has also been reported in dural-based metastasis and cortical intraparenchymal metastasis, mostly in prostate and neuroblastoma metastasis (9,39), but in our study in the 13 cases of metastasis we did not note DTS. Also we did not fi nd DTS in any of the 3 cases of lymphomas.

Conclusion
Our study suggests that the dural tail is a common but not a pathognomic sign of meningioma on contrast-enhanced T1 MR images. Other intracranial lesions, such as glioblastoma multiforme, pituitary adenoma, schwannoma, medullobastoma and Wegener's granulomatosis, also can present with this sign. In our study we found the dural tail sign to have a sensitivity of 68.6% and specifi city of 88.5% in diagnosis of meningioma.