Intracranial arachnoid cyst can be classified as primary developmental cysts or secondary cysts. Primary cysts arise from the splitting of the arachnoid membranes in utero, resulting in the development of anomalous collections of cerebrospinal fluid (CSF). Secondary cysts are less common, often appearing after trauma, surgery, infection, or intracranial hemorrhage.
Intracranial cysts are classified as supratentorial, infratentorial, and supra-infratentorial (tentorial notch) 1).
50-66% occurring within the middle cranial fossa in most series. Ten percent occur in the suprasellar and quadrigeminal regions and approximately 5% each in the posterior fossa and over the frontal convexities.