Supracerebellar arachnoid cyst

Case contributed by Frank Gaillard


Epilepsy for investigation. Incidental finding.

Patient Data

Age: 40 years
Gender: Female

MRI brain


A supracerebellar CSF intensity cyst measuring 33 x 34 x 29 mm produces mass effect on the cerebellum and elevates the tentorium cerebelli and displaces the pineal gland a little superiorly and anteriorly. It is slightly eccentric to the right, resulting in slightly greater inferior cerebellar tonsillar herniation on the right (6 mm) than on the left (3 mm). The tectum is not significantly compressed and no hydrocephalus is present. 

Annotated images

Annotated image

Supracerebellar arachnoid cyst (yellow) is located posterior to the tectum (blue) and inferior to the pineal gland (red). 

On coronal imaging not only are the two pairs of colliculi visible (blue) but so are the paired internal cerebral veins (green) located above the pineal gland (red) and the basal veins of Rosenthal (orange) on either side of the superior colliculi in the ambient cistern

Case Discussion

Although somewhat atypical in location, this case demonstrates typical appearances of an arachnoid cyst displacing the pineal gland. 

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