Cross sectional imaging of Intracranial cystic lesions Abdel Razek A

Transcription

1 Cross sectional imaging of Intracranial cystic lesions Abdel Razek A Department of Radiology. Mansoura Faculty of Medicine, Mansoura. Egypt. arazek@mans.edu.eg

2 Introduction Intracranial cystic lesions can present a diagnostic challenge. These lesions include benign tumors, malignant tumors and other lesions. Differentiation between good, bad and ugly cystic lesions is essential for treatment planning.

3 Purpose 1- To illustrate the causes of intracranial cystic lesions. 2- To review the typical and atypical MR appearance of intracranial cystic lesions. 3- To describe the role of diffusion weighted imaging in the differential diagnosis of intracranial cystic lesions.

4 Cystic lesions Variant: Virchow Robin space Cavum Septum Pellucidum Pineal cyst Rathke s cleft cyst Neuroepithelial cyst Interhemispheric cyst Developmental: Epidermoid Dermoid Arachnoid cyst Neuroeneteric cyst Colloid cyst Others: Cystic Neoplasm Hydatid cyst Leptomeningeal cyst

5 Methods of examination MR imaging DWI MRS Dynamic MR CT Metrimzinde

6 Cavum septum pellucidium The septum pellucidum consists of two thin sheets of white matter surrounded by gray matter. The persistence of this septum after birth is called cavum septi pellucidum

7 Enlarged Virtchow Robins Spaces (VRS) VRS are pial-lined interstitial fluid-filled structures that accompany penetrating arteries and veins Normal variant. Appear as smoothly demarcated fluid-filled cysts, of variable size. May be isolated or occur in clusters in basal ganglia. They are isointense to CSF on all sequences. No enhancement, no focal mass effect, no restricted diffusion on DWI. Etat Crible- cluster of very large VR spaces-look ugly, but are benign.

8 Dilated Pervascular Spaces

9 Pineal cyst seen in up to 10% of cases at routine imaging and in 20% 40% of cases at autopsy unilocular fluidfilled mass within the pineal gland. SI varies with cyst contents. Rim or nodular calcium (25%). Rim or nodular enhancement. T1WI: ~60% are slightly hyperintense to CSF. Most do not appear hypointense on FLAIR images, and 60% enhance.

10 Pineal Cyst

11 Interhemispheric cyst Commonly seen in patient with corpus callosum agenesis and other midline defects. The origin of the interhemispheric cyst in agenesis of the corpus callosum is controversial.

12 Neuro-epithelial Cyst Neuroepithelial cyst similar to ependymal cyst Follow CSF signal on MR Oval or round ranging from a few mm to 2 cm in size Minimal mass effect

13 Ependymal cyst Rare, benign, ependymal-lined neuroepithelial cysts that can occur anywhere in the central nervous system. They may seen in subarachnoid spaces, brainstem, cerebellum, and spinal cord. Intrinsically benign, but may cause problems secondary to mass effect or obstruction of CSF circulation MRI shows intraparenchymal, fluid filled space occupying lesions usually located close to a ventricle. They are thin walled, follow CSF signal on all sequences (although occasionallymay be hyperintense relative to CSF due to high protein content), do not enhance and do not have restricted diffusion.

14 Rathke s cleft cyst Arise from remnants of embryonic Rathke cleft. Usually an incidental finding imaging clue is a nonenhancing noncalcified intra- and/or suprasellar cyst with an intracystic non enhancing mural nodule. T1WI: hyperintense (50%), hypointense (50%). T2WI: hyperintense (70%), iso- hypointense (30%). If within an otherwise normal pituitary gland, no clinical significance If in suprasellar location may impinge on optic chiasm

15 Epidermoid Epidermoid cysts comprise 0.2% 1.8% of primary intracranial tumors and are four to nine times as common as dermoid cysts. Site: cerebellopontine angle cistern (40% 50%),4 th ventricle (17%), sellar regions (10% 15%) All are located off the midline. The best diagnostic clue is a CSF-like mass that insinuates within cisterns, encasing adjacent nerves and vessels. On CT scans, most epidermoid cysts are well-defined hypoattenuated masses that resemble CSF and do not enhance. Calcification is present in 10% 25% of cases. Most epidermoid cysts are isointense or slightly hyperintense to CSF on T1 & T2WI.

16 They do not suppress completely on FLAIR images and have restricted diffusion (show high signal intensity) on DWI Most epidermoid cysts do not enhance Rare white epidermoids have high protein content and may appear hyperattenuated on CT scans. show reversed signal intensity on MR images, with high SI on T1- and low SI on T2WI

17 Epidermoid cyst

18 Epidermoid cyst

19 Dermoid On CT have lower attenuation then a epidermoid ( HU) Contain lipid material from sebaceous and apocrine sweat glands Dystrophic calcifications Layering: fat fluid level MR:T1: hyperintense fat T2: low signal with loculations & inhomogenous Chemical Shift artifact The fat signal suppresses on STIR or other fat suppression sequences Rupture: Fat/csf levels in subarachnoid spaces and ventricles Ventriculomegally Chemical meningitis.

20 Dermoid cyst

21 Arachnoid cyst Most commonly seen in middle cranial fossa (60%), suprasellar cistern & posterior fossa (10%). The best diagnostic clue is a sharply demarcated extraaxial cyst with scalloping of the adjacent. The classic arachnoid cyst has no identifiable internal architecture and does not enhance. The cyst typically has the same signal intensity as CSF at all sequences. Benign unless so large they are causing mass effect on adjacent structures

22 Arachnoid cyst

23 Colloid cyst 15% 20% of intraventricular masses Size: cm. The mean size is 1.5 cm Often more easily identified on non contrast enhanced CT-round sharply marginated hyperattenuating mass in roof of third ventricle near foramen of Monroe T1: hyperintense in 2/3 of cases. May be very subtle T2: isointense to brain may peripheral rim enhamcnet. Dangerous lesion: may cause sudden ventricular obstruction and death

24 Colloid cyst

25 Neuroeneteric cyst (NEC) Develop from persistent neuroenetric canal Lesions in midline, anterior to brainstem. Diagnostic clue is a round and/or lobulated, nonenhancing, slightly hyperintense mass anterior to medulla. High SI on T1 & T2WI due to its protein content. Hyperintense on FLAIR with restricted diffusion Rarely show rim enhancement.

26 Leptomeingeal cysts After a skull fracture associated with a dural tear, meninges and brain tissue may herniate into a diastatic fracture site. This prevents osteoblastic migration and healing and can result in a growing fracture or leptomeningeal cyst. Leptomeningeal cyst

27 Hydatid cyst Appears as unilocular cyst w/thick wall, unilocular mother cyst with multiple vesicles arranged along its wall, or multiple daughter cysts filling the maternal cyst. A B

28 Cyst associated with benign extra axial tumor Large non neoplastic cysts seen with extraaxial tumors such as meningioma, schwannoma, craniopharyngioma It has SI similar to CSF at all pulse sequnces 2-10% of adult & 25% of pediatric meningiomas.

29 Cystic tumor

30 Craniopharyngioma Craniopharyngiomas arise from remnant of Rathke s pouch and typically demonstrate calcification in children Approximately 90% have nodular, globular, or rim enhancement. The presence of solid enhancing nodules in the cyst wall also favors the diagnosis of craniopharyngioma. The rare noncalcified cystic nonenhancing craniopharyngioma is more commonnly seenin adults than in children.

31 Conclusion 1) MR imaging is essential for diagnosis and characterization of intracranial cystic lesions as well as differentiating malignant from benign lesions. 2) Advanced MR imaging techniques helps in refining diagnosis of intracranial cystic lesions. This information is essential for treatment planning

32 References Ajtai B, Bertelson JA. Imaging of Intracranial Cysts. Continuum 2016;22: Taillibert S, Le Rhun E, Chamberlain MC. Intracranial cystic lesions: a review. Curr Neurol Neurosci Rep 2014;14:481. Osborn A, Preece M. Intracranial Cysts: Radiologic-Pathologic Correlation and Imaging Approach. Radiology 2006;239: Kwee RM, Kwee TC. Virchow- Robin spaces at MR imaging. Radiographics. 2007;27: Hu X, Hu C, Fang X, et al. Intraparenchymal epidermoid cysts in the brain: diagnostic value of MR diffusion-weighted imaging. Clin Radiol 2008;63: Park KJ, Kang SH, Chae YS, et al. Supratentorial arachnoid cyst located in the brain parenchyma: case report. Neurosurgery 2011;68:E Brown JY, Morokoff AP, Mitchell PJ, et al. Unusual imaging appearance of an intracranial dermoid cyst. AJNR 2001;22: Rao G, Anderson R, Feldstein NA, Brockmeyer DL. Expansion of Chang,Song, Kim, et al. In Vivo Single Voxel Proton MR Spectroscopy in Intracranial Cystic Masses. AJNR 1998;19:

33