What treatment is required?
Arachnoid cysts are benign and the vast majority remain asymptomatic throughout life. If they are deemed to be causing symptoms then surgery can be contemplated. This can either take the form of a craniotomy (fenestration or excision) or placement of a cystoperitoneal shunt.
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.