Intraventricular arachnoid cyst

Case contributed by Mehmet Yağtu
Diagnosis almost certain


Follow-up of an incidental lesion.

Patient Data

Age: 7 years
Gender: Male

There is a large cystic lesion in the temporal horn of right lateral ventricle. It has high signal intensity on T2 images and low intensity on T1 images; with these findings, the cyst has the same intensity to CSF. No diffusion restriction on DWI and ADC. In post-contrast images, there is no mural enhancement or solid component.

With large cystic shape, laterally it has a mass effect on temporal bone ending with remodeling convexity and medially it makes a loss of thickness in the medial temporal lobe, uncus and parahippocampus. The especially thin cyst wall can be seen in all sequences. But it has no related gliosis or vasogenic edema on FLAIR or T2 image.

Case Discussion

MRI demonstrates a large cystic lesion located in the temporal horn of the right lateral ventricle. The differential diagnosis of intraventricular cystic lesion is commonly an arachnoid cyst, whereas others are ependymal cyst, neuroepithelial cyst or a very large choroid plexus cyst could be thought. Distinguishing between them on conventional MRI imaging is difficult. 

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