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Intraventricular arachnoid cyst

Case contributed by Royal Melbourne Hospital


Increasing headaches.

Patient Data:

Age: 40 years
Gender: Female
Race: Caucasian
Modality: CT
Modality: MRI

Case Discussion:

Non contrast CT demonstrates expansion of the posterior part of the body of the right lateral ventricle. It is above the trigone and does not appear to have a colpocephaly configuration. The temporal horn is also distended but to a lesser degree. 

MRI demonstrates that the expansion is caused by a very thin walled (best seen on T2 fast spine echo sequences) cystic lesion which follows CSF on all sequences, including FLAIR and DWI. 

Except for the location, the appearances are characteristic for an arachnoid cyst. Intraventricular arachnoid cysts, sometimes referred to (perhaps more accurately in these cases) as CSF cysts, are rare but well described. 

The absence of an enhancing component makes other lesions most unlikely. 

The patient went on to have endoscopic fenestration of the cyst, with histological confirmation of the diagnosis. 


Specimen Type: Arachnoid cyst fluid

MACROSCOPIC  DESCRIPTION: 1 air-dried slide received.

MICROSCOPIC  DESCRIPTION: The smear contains foamy macrophages, leptomeningeal cells and red blood cells. No malignant cells are identified.


This case was part of Royal Melbourne Hospital Radiology Department Quiz (May 2011). 

Case discussion by: Dr Frank Gaillard, consultant neuroradiologist, Royal Melbourne Hospital. 

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