Preoperative MRI findings. Axial T1-weighted image (a) shows a 3.7 × 2.2 × 2.7 cm well-circumscribed complex cystic lesion in the region of the pineal gland, causing significant mass effect on the surrounding structures. There is inferior compression and thinning of the tectal plate, posterior displacement and deformity of the superior cerebellar vermis. T1 postcontrast images ((b) and (e)) show the thin septation posteriorly. There is no enhancement of the cyst wall. On T2-weighted images (c), the signal characteristics are similar to CSF, but the cyst fluid is isointense to slightly hyperintense on FLAIR images ((d) and (f)).
