Extradural endodermal cyst of posterior fossa: case report, review of the literature, and embryogenesis.

Abstract

Posterior fossa endodermal cysts are rare. They are located in the midline, in ventral or ventrolateral locations, or intrinsic to the neural axis. Accordingly, various theories of embryogenesis have been proposed. We report the first case of an extradural, dorsolaterally situated endodermal cyst. An adult male patient presented with a short history of headache and cerebellar ataxia. Neuroimaging revealed an extra-axial cystic posterior fossa mass. An entirely extradural cyst was found and was totally excised. Immunohistochemistry confirmed the diagnosis of endodermal cyst. The extradural, dorsal location of the endodermal cyst suggests gaps at the cranial end of the notochord causing ectodermal-endodermal adhesions during early gastrulation and the persistence of endodermal remnants in the dorsal mesenchyme of the blastemal cranium. The literature is reviewed, and proposed theories of embryogenesis are discussed.