Intracranial Lesions: MRI Signs for Localization

Transcription

1 Intracranial Lesions: MRI Signs for Localization Poster No.: C-1574 Congress: ECR 2017 Type: Educational Exhibit Authors: M. Cucos, A. Puiu, S. Manole ; Cluj-Napoca/RO, Cluj napoca/ RO Keywords: Cerebrospinal fluid, Localisation, Education, Diagnostic procedure, MR, Neuroradiology brain DOI: /ecr2017/C Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 14

2 Learning objectives 1. To discuss the reliability of MRI criteria of differentiation of intra-axial and extra-axial lesions. 2. To suggest a simple MRI protocol adjustment which might prove useful in case of uncertainty of intra-axial versus extra-axial lesion location. Background MRI is the imaging technique of choice for the majority of non-acute intracranial lesions. The attempt to predict the histology of a lesion such as a brain tumor by using MRI is obviously a commendable endeavor. Such attempt, however, is non-essential. MRI prediction of tumor histology rarely leads to diagnostic or therapeutic adjustments, which most commonly consist of tumor biopsy or surgical excision. Nevertheless, accurate and detailed MRI characterization of intracranial lesions is positively essential. In this respect, it is recommendable to always begin with locating the lesion into the intra-axial or extra-axial compartment; this is the most important question for the radiologist when confronted with an intracranial lesion, especially if the lesion has the appearance of a tumor: intra-axial lesions are located in the brain parenchyma, which they may expand extra-axial lesions originate from tissues outside the brain parenchyma, such as the skull, dura, or arachnoid, which they may compress. Determining the intra-axial or extra-axial location of an intracranial lesion is of the utmost importance for an appropriate differential diagnosis, which in turn will dictate treatment planning and prognosis: most intra-axial lesions are malignant: cerebral metastases, malignant astrocytomas most extra-axial lesions are benign: meningiomas, cystic lesions. Findings and procedure details Page 2 of 14

3 Occasionally, MRI allows straightforward location of an intracranial lesion in the intraaxial or the extra-axial compartment. Fig. 1 on page 3 Nevertheless, systematic search for a number of signs is required in the majority of cases. The most reliable signs of extra-axial location: cerebrospinal fluid (CSF) cleft between the lesion and the brain parenchyma Fig. 2 on page 4 interposition of pial vessels between the lesion and the brain parenchyma. Fig. 3 on page 5 The aforementioned signs can be seen most clearly on T2-weighted images. The CSF cleft can be confirmed on T1-weighted images and on FLAIR images. Fig. 4 on page 5 There are additional signs of extra-axial location, but they may either be absent in extraaxial lesions or accompany intra-axial lesions: cerebral cortex interposition Fig. 5 on page 6 white matter buckling Fig. 6 on page 6 broad dural base Fig. 7 on page 8 Fig. 8 on page 8 dural tail Fig. 9 on page 8 bone reaction - hyperostosis or lysis Fig. 10 on page 9 vasogenic edema Fig. 11 on page 10 enhancement pattern Fig. 12 on page 11 Fig. 13 on page 12 Fig. 14 on page 12 Despite the abundance of these MRI criteria, differentiation of intra-axial lesions from extra-axial lesions may occasionally still be challenging. In case of uncertainty of lesion compartment, a simple protocol adjustment may be helpful: the acquisition of high-resolution T2-heavily weighted slices of 2 or 3 mm thickness, focused on the region of interest. This sequence may allow better visualization of the CSF cleft or of displaced pial vessels. Fig. 15 on page 12 Images for this section: Page 3 of 14

4 Fig. 1: a. Intra-axial lesion: breast cancer metastasis (arrow). b. Extra-axial lesion: meningioma (arrow). Page 4 of 14

5 Fig. 2: The drawing illustrates a CSF cleft (arrow) interposed between the extra-axial lesion and the brain parenchyma. The T2 image and the inset show a CSF cleft (arrows) due to a convexity meningioma. Fig. 3: The drawing illustrates displacement of pial vessels (arrows) between the extraaxial lesion and the brain parenchyma. The T2 image shows displacement of the anterior cerebral arteries (circle) due to an olfactory groove meningioma. Displaced pial vessels are seen as flow voids, most easily on T2-weighted images. Page 5 of 14

6 Fig. 4: CSF cleft (arrows) on T2, FLAIR, and T1-weighted images. T2-weighted image shows a high signal intensity cleft between the lesion and the brain parenchyma. On FLAIR images, the CSF cleft may not attenuate, due to the presence of tumor products in the CSF. On T1-weighted images, the CSF cleft is of low signal intensity. Fig. 5: Cerebral cortex interposition (arrow) is noted on the T2-weighted image between the rest of the brain parenchyma and an extra-axial lesion. Non-enhanced (NE) T1weighted image and T2*GRE show evidence of blood products. This was a rare case of bleeding metastasis due to splenic lymphoma. Page 6 of 14

7 Fig. 6: The drawing illustrates compression and displacement of the white matter, with loss of its normal folded appearance (arrow). The T2 image shows white matter buckling (arrow) in the left temporal lobe. Low T1 signal intensity and restricted diffusion on DWI are diagnostic for epidermoid cyst. Page 7 of 14

8 Fig. 7: Sphenoid wing meningioma (arrows) with broad dural base. Sagittal T2-weighted image shows CSF cleft and pial vessels interposition, thereby confirming extra-axial location. Fig. 8: Giant partially thrombosed aneurysm (yellow arrow) of the supraclinoid internal carotid artery (green arrow). This, obviously, is an extra-axial lesion with no dural base. The dural base sign is not infallible. Page 8 of 14

9 Fig. 9: a. Anaplastic meningioma with intraorbital extension showing adjacent dural enhancement (arrow). b. Glioblastoma showing adjacent dural enhancement (arrow). Intra-axial lesions may occasionally show dural enhancement if they are peripherally located. Page 9 of 14

10 Fig. 10: a. T1-weighted image shows bone hyperostosis (arrow) adjacent to a convexity meningioma. b. CT scan shows bone lysis (arrow) due to a psammomatous meningioma. Bone reaction certifies contact between the lesion and the bone, but is no reliable proof of the extra-axial origin of a lesion. Page 10 of 14

11 Fig. 11: Extensive vasogenic edema may accompany extra-axial lesions. a. Extra-axial lung cancer metastasis with extensive vasogenic edema (arrow). b. Intra-axial lung cancer metastasis with mild vasogenic edema (arrow). Page 11 of 14

12 Fig. 12: Intra-axial brain metastases showing ring enhancement (arrows). The majority of intra-axial lesions enhance inhomogeneously, following disruption of the blood-brain barrier. Fig. 13: Homogeneous enhancement (T1+C) of meningioma, an extra-axial lesion with a CSF cleft (arrow). The majority of extra-axial lesions enhance homogeneously due to the absence of the blood-brain barrier in the extra-axial compartment. Fig. 14: Meningioma showing inhomogeneous enhancement (T1+C). Occasionally, extra-axial lesions show inhomogeneous enhancement due to intralesional necrosis or cystic transformation. Arrow points to CSF cleft. Page 12 of 14

13 Fig. 15: The upper pannel shows 4 mm thick T2-weighted images. Arrows indicate an intracranial lesion, with no discernible CSF cleft or interposition of pial vessels between the lesion and the brain parenchyma. The lower pannel shows the same lesion on 3 mm thick T2-heavily weighted images. Arrows sequentially indicate the CSF cleft, cerebral cortex interposition, and insinuation of CSF between the lesion and the cerebral cortex. The lesion proved to be a meningioma. Page 13 of 14

14 Conclusion MRI determination of the intra-axial or extra-axial location of a lesion requires the systematic search for a number of imaging signs. Knowledge of the reliability and pitfalls of these signs makes MRI the most sensitive imaging techique for defining the compartment of origin of intracranial lesions. Personal information Cucos M - Resident in training, Department of Radiology, Emergency County Hospital, Cluj Napoca, Romania. Chief of department, Sorin M Dudea MD PhD. References rd 1.Brant WE, Helms CA. Fundamentals of Diagnostic Radiology. 3 edition. Philadelphia: Lippincott Williams & Wilkins, Google books. Web. 3 Oct books.google.com 2.Parizel PM et al. Clinical MR Imaging: A Practical Approach. Berlin: Springer, Google books. Web. 3 Oct Drevelegas A. Extra-axial brain tumors. Eur Radiol George AE, Russell EJ, Kricheff II. White matter buckling: CT sign of extraaxial intracranial mass. AJR Sartor K. MR Imaging of the Skull and Brain: A Correlative Text-Atlas. Berlin: Springer Google books. Web. 3 Oct Intra-axial versus extra-axial intracranial tumors: key facts in case of uncertainty. Cucos M, Manole S. Annual Meeting of the Romanian Society of Radiology and Medical Imaging. Iasi, 6-7 October, Page 14 of 14