Congenital extradural cyst of the orbital optic nerve: case report

A rare congenital arachnoid cyst of the orbital optic nerve affecting a 5-year-old boy is described and the relevant literature is reviewed. On the basis of the macro- and microscopic features of the reported case, an analogy is suggested between the observed optic nerve cyst and the extradural arachnoid cyst of the spinal canal. Moreover, the hypotheses put forward to explain the pathogenesis of spinal extradural arachnoid cysts may also account for the exceptional appearance of a similar cyst in the orbital portion of the optic nerve.