Imaging Findings of CNS Atypical Teratoid/Rhabdoid Tumors

Fig. 39.1

Axial CT and MRI posterior fossa images of a 3 years old boy. CT section without contrast through the midpons level shows a hyperattenuated heterogeneous midline mass with foci of calcification (a). Corresponding T2 weighted image reveals a T2 hyperintense mass filling the forth ventricle with eccentric multiple cysts (b).There is a slight heterogeneity within mass containing a minimal peripheral vasogenic edema. It is hard to depict calcification with T2 weighted images alone. However, T1 weighted axial image at the same level demonstrate calcification as a small foci of hyperintensity, which is unusual (c). It is easy with FLAIR (fluid attenuated inversion recovery) to separate solid component, cysts and surrounding edema (d). There is avid heterogeneous enhancement after contrast administration including the eccentric cyst wall (e)

Fig. 39.2

Coronal T1 weighted image after contrast administration of a 2 years old female. There is a strong wavy rim of peripheral contrast enhancement of a AT/RT in posterior fossa. Central necrotic or cystic zone is seen. Although rare, this sign could be specific to AT/RT

Fig. 39.3

A heterogeneous extra-axial mass located in cerebellopontine angle with avid but patchy enhancement is seen on axial post-contrast T1-weighted image of a year old boy with a posterior fossa AT/RT

Fig. 39.4

Axial CT section through the posterior fossa without contrast (a), axial T2 (b), axial T1 (c), sagittal T1 without contrast (d) and axial T1 with contrast (e) demonstrate hyperattenuated inta-axial masses with tiny foci of calcifications extending to the cerebellopontine angle in a 3 years old female. Eccentric cystic component, intratumoral hemorrhage as a T1 hyperintense foci, avid but heterogeneous enhancement are seen

Fig. 39.5

A large cystic cerebellar mass and diffuse leptomenengial spreading including the bilateral seventh cranial nerves are seen in a an infant

39.2 Calcification and Hemorrhage

CT is usually demonstrated foci of calcification (Figs. 39.1a and 39.4a). Although it can be seen hypointense foci on all sequences and may demonstrate blooming on gradient echo sequences, susceptibility-weighted imaging (SWI) is very sensitive to it and readily demonstrates both calcification and intratumoral hemorrhage as intratumoral susceptibility dots (Fig. 39.6). In addition to that, phase images of SWI may make a differentiation between them.

Fig. 39.6

A large midline posterior fossa mass including cerebellum, mesencephalon and pineal gland extending to supratentorial area in a 6 year old boy with AT/RT is seen on axial T2 (a), T1 (b), T1 with contrast (c), SWI (d), DWI (e), and ADC map (f). Heterogeneous midline mass includes eccentric cysts and surrounding marked vasogenic edema. There is an excessive hemorrhage within it. But it is hard to pick up these hemorrhages with conventional sequences including DWI. However, SWI clearly depicts them as intratumoral susceptibility dots. Strong diffusion restriction is seen as hyperintensity on DWI and hypointensity on ADC map

39.3 CT

The increased cellularity of the solid part of tumor may make the appearance on CT to have increased attenuation without contrast (Figs. 39.1a and 39.4a). But it can be iso- or hypodense comparing to adjacent brain parenchyma. Calcification, hemorrhage, and intratumoral cysts are giving an CT appearance to AT/RT rather heterogeneous.

39.4 MRI

Findings on T1- and T2-weighted images are variable (Figs. 39.1, 39.2, 39.4, and 39.6). AT/RT is typically iso- to hypointense compared to white matter on T1-weighted sequences; however, intratumoral hemorrhage will demonstrate regions of T1 hyperintensity, which are more characteristic of AT/RT compared to medulloblastoma (Fig. 39.1). T2 signal intensity is variable and usually heterogeneous; more cellular components are T2 hypointense, while less cellular components are iso- to mildly hyperintense compared to white matter (Figs. 39.1 and 39.6). Despite the aggressive features, there is often little or no vasogenic edema within the surrounding parenchyma (Fig. 39.1b). Peripherally located and relatively large eccentric cysts are frequently seen and are T2 hyperintense (Figs. 39.1, 39.4, and 39.7). T1 signal intensity of the cyst is usually hypointense but can be variable. T1 hyperintense cysts which have protein rich content can be seen (Fig. 39.4d).

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