ADVANCED TECHNIQUES IN MAGNETIC-RESONANCE-IMAGING IN THE EVALUATION OF THE LARGE ENDOLYMPHATIC DUCT AND SAC SYNDROME

The purpose of this report is to compare temporal bone computed tomogr aphy (CT) to high-resolution magnetic resonance (MR) imaging using a n ovel thin-section fast spin echo (FSE) pulse sequence in identifying a nd characterizing patients with large vestibular aqueduct syndrome. Si xteen patients with sensorineural hearing loss and a CT diagnosis of l arge vestibular aqueduct(s) underwent high-resolution fast spin echo m agnetic resonance imaging with dual, 3-in phased array receiver coils centered over the external auditory canals. Magnetic resonance imaging parameters included axial and oblique sagittal fast spin echo with an effective slice thickness of 1 mm contiguous. Thirty-eight patients w ith 76 normal inner ears who underwent MR imaging using this technique had their endolymphatic duct measured. MR alone identified the enlarg ed endolymphatic sac seen along with the large endolymphatic duct in a ll cases. Three cases (five inner ears) with enlarged bony vestibular aqueducts on CT showed no evidence of endolymphatic duct or sac enlarg ement on MR. MR alone identified a single case of mild cochlear anomal y in conjunction with an enlarged endolymphatic duct and sac. In the n ormal population the size of the normal endolymphatic duct at its midp oint measured from 0.1 to 1.4 mm. Thin-section, high-resolution fast s pin echo MR imaging of the inner ear may be superior to CT in the eval uation of patients with the large vestibular aqueduct syndrome.