Presentation
Chronic headache.
Patient Data
A well defined extra-axial spindle-shaped right frontoparietal cystic lesion is noted measuring 4 x 2 cm. It showed a thin wall and clear watery content. It follows CSF in all pulse sequences including free diffusion. It exerts a mild mass effect in the form of compression upon the underlying brain parenchyma but no midline shift. No associated cerebral edema. It is splaying the overlying inner table of the skull.
Case Discussion
Arachnoid cyst is a benign extra-axial cyst that follows CSF in all pulse sequences including FLAIR and DWI. It implies mild mass effect as compression on the surrounding structures. It can remodel the overlying bone over time and if large in size.