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 March 2008 Case of the Month 

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Compiled by: Ramit Mendi, M.D.                                                                                                        

 

History: 79-year-old female with history of headaches and vertigo
 

Findings: 2.1-cm oval-shaped mass along the roof of the 3rd ventricle with signal characteristics as demonstrated below.   The smooth diffuse dural enhancement on postcontrast imaging is the result of chronic dural irritation in this patient with a ventricular shunt catheter.

Images: Axial T1 (Figure 1), Axial T2 (Figure 2), Axial FLAIR (Figure 3), Coronal T1 post contrast (Figure 4), and Axial T1 post contrast (Figure 5)


Figure 1                                                                                                        Figure 2
         

Figure 3                                                                                                        Figure 4
         

Figure 5

Diagnosis: Colliod Cyst

 

Discussion: Colloid cysts are a form of neuroepithelial cyst that typically arise in the anterior aspect of the 3rd ventricle. Its position in the anterior aspect of the 3rd ventricle near the foramen of Monro makes this mass clinically significant although it is benign, because it often causes acute hydrocephalus.  

 

On CT, a colloid cyst may appear as hypodense or hyperdense. MRI generally reveals a well-defined, round mass with a thin rim. The center of the mass is often heterogeneous in signal. The most common appearance is that of heterogeneously high signal on T1- and isointense signal on T2-weighted images. 25% have a mixed hypo/hyperintense signal as this in the current case.

 

The appearance of hyperdensity on CT and hyperintensity on T1 MR images may be explained by the cholesterol content of the cyst.   Another proposed explanation is that paramagnetic effects from metallic contents of the cyst cause high signal on T1-weighted images. Colloid cysts may contain calcifications.


 

References:

Maeder PP, Holtas SL, Basibuyuk LN, et al.   Colloid Cysts of the 3rd Ventricle:   Correlation of MR and CT Findings with Histology and Chemical Analysis.   American Journal of Roentgenology 1990; 155:135-141.

 

Osborn A [et. al].   Diagnostic Imaging: Brain .   Salt Lake City.   Amirsys 2004.





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