title: Computed tomography in the diagnosis of extra-axial posterior fossa masses.
abstract: Extra-axial posterior fossa masses can be diagnosed reliably by computed tomography (CT) in most cases. Acoustic and trigeminal neurinomas, meningiomas, cholesteatomas, and other extra-axial masses can usually be distinguished from intra-axial masses by asymmetric widening of the basal subarachnoid spaces, bone destruction, continuity of the tumor mass with the tentorium or bone, and more sharply defined margins. Multiple-cut study of the posterior fossa improved visualization of the fourth ventricle and basal cisterns. Interpretation of cisternal changes in association with changes in the fourth ventricle and abnormal attenuation coefficients permits accurate diagnosis of posterior fossa masses.
mesh_terms: D000783:Aneurysm / Q000000981:diagnostic imaging; D001368:Axis, Cervical Vertebra / Q000000981:diagnostic imaging; D002551:Cerebral Ventricle Neoplasms / Q000000981:diagnostic imaging; D002781:Cholesteatoma / Q000000981:diagnostic imaging; D003388:Cranial Fossa, Posterior / Q000000981:diagnostic imaging*; D003936:Diagnosis, Computer-Assisted; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D004806:Ependymoma / Q000000981:diagnostic imaging; D006801:Humans; D008579:Meningioma / Q000000981:diagnostic imaging; D009442:Neurilemmoma / Q000000981:diagnostic imaging; D010524:Peripheral Nervous System Neoplasms / Q000000981:diagnostic imaging; D012886:Skull / Q000000981:diagnostic imaging*; D012888:Skull Neoplasms / Q000000981:diagnostic imaging*; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging; D014056:Tomography, X-Ray; D014276:Trigeminal Nerve / Q000000981:diagnostic imaging; D000159:Vestibulocochlear Nerve / Q000000981:diagnostic imaging