Epidural hygroma of the posterior fossa.
D002675:Child, Preschool; D003388:Cranial Fossa, Posterior / Q000000981:diagnostic imaging; D006801:Humans; D008202:Lymphangioma / Q000000981:diagnostic imaging*; D008297:Male; D011859:Radiography; D012888:Skull Neoplasms / Q000000981:diagnostic imaging*