A Study on the Malformation of Large Vestibular Aqueduct with High-Resolution MR

Objective To evaluate the morphologic and signal changes occrring in the labyrinth's fine structure of patients with large vestibular aqueduct syndrome. Methods In 26 patients with malformation of large vestibular aqueduct,hihg-resolution MR imaging was adopted with 3D-FIESTA or 3D-FSE sepquence,and slice thickness of less than 1mm,to evaluate the morphologic and signal changes of the fine structure. Results (1) In all of the patients the isthmus of the vestibular aqueduct and endolymphatic sac were dilated at the medial wall of the common crus of semicircular canals.There existed a low-signal-intensity septum between the isthmus and common crus.The dilated vestibular aqueduct could also be identifed when it came into vestibule.(2) In 3D-FIESTA sequence,there was an low-signal-intensity area in the extra-osseous parts of all the enlarged endolymphatic sacs,compared with the signal intensity of vestibule or cochlear duct.(3) A case with malfomation of large vestibular aqueduct was also complicated with abnormal hypointensity in vestibule,some semicircular canals and cochlear duct. Conclusion The malformation of large vestibular aqueduct is not only associated with morphologic change but also with signal changes,which indicates the abnormality of the endolymphatic fluid.