title: Posterior fossa ependymal cyst and atlantoaxial subluxation in a patient with Down syndrome: CT findings.
abstract: A 61-year-old woman with Down syndrome presented with progressive deterioration of gait over 9 months. Cranial CT without and with intravenous administration of contrast material demonstrated a posterior fossa cyst. The cyst did not communicate with the fourth ventricle or subarachnoid spaces as proven by CT following a metrizamide ventriculogram. Surgical fenestration of the cyst into the fourth ventricle was done. In addition, a moderate atlantoaxial subluxation with 2 mm movement from extension to flexion was present, which was thought not to be clinically significant, but which might require a spinal fusion at a future time. Ependymal cells were found as a result of a biopsy of the cyst wall.
mesh_terms: D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging* / Q000293:injuries; D003388:Cranial Fossa, Posterior; D003560:Cysts / Q000000981:diagnostic imaging*; D004314:Down Syndrome / Q000150:complications*; D004805:Ependyma / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000000981:diagnostic imaging*; D008875:Middle Aged; D014057:Tomography, X-Ray Computed