Colloid cyst

Case contributed by Assoc Prof Frank Gaillard


Adult patient presenting with headache

Patient Data

Age: Adult

CT brain

Non-contrast CT demonstrates a rounded hyperdense mass at the level of the foramen of Monro. The ventricles are enlarged, more-so than the sulci although there is certainly a degree of cerebral volume loss.  


MRI brain

The rounded structure at the foramen of Munro is confirmed. The content of the cyst is hyperintense on T1, hypointense on T2 and demonstrates no central enhancement or restricted diffusion. 

The ventricles are a little prominent with likely a minor degree of hydrocephalus, although the degree of cerebral volume loss and expected ex-vacuo dilatation of ventricles does make this a little difficult to determine. 


Annotated images

A hyperdense (on CT) rounded colloid cyst (green arrow) is present int he roof of the third ventricle (yellow dotted line).  The content of the cyst is hyperintense on T1 and markedly hypointense on T2 and FLAIR.

Case Discussion

This case demonstrates typical appearances of a colloid cyst

This case elegantly illustrates two potential traps of interpreting MRI signal intensities:

  1. just because a cystic structure appears to have CSF signal on FLAIR does not mean that this is true - in this case the content is very T2 hypointense
  2. density of MRI is relative, not absolute (unlike CT) and thus care should be taken when interpreting post contrast sequences - note how in this case the center of the cyst appears less bright than pre-contrast
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Case information

rID: 10638
Published: 29th Aug 2010
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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