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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 21:1664-1669 (10 2000)
© 2000 American Society of Neuroradiology

ARTICLE

MR Imaging of the Enlarged Endolymphatic Duct and Sac Syndrome by Use of a 3D Fast Asymmetric Spin-echo Sequence: Volume and Signal-intensity Measurement of the Endolymphatic Duct and Sac and Area Measurement of the Cochlear Modiolus

Shinji Naganawa^,a, Tokiko Koshikawa^a, Eriko Iwayama^a, Hiroshi Fukatsu^a, Tsuneo Ishiguchi^a, Takeo Ishigaki^a, Mitsuru Ikeda^a, Tsutomu Nakashima^a and Nobuyasu Ichinose^a

^a From the Departments of Radiology (S.N., T.K., E.I., H.F., Ts.I., Ta.I), Medical Information and Records (M.I.), and Otolaryngology (T.N.), Nagoya University School of Medicine, Nagoya, Japan; and Toshiba Nasu Works, Tochigi, Japan (N.I.).

BACKGROUND AND PURPOSE: In enlarged endolymphatic duct (EED) and sac (EES) syndrome, deformity of the EED and EES is congenital; however, hearing loss is acquired. To investigate the pathophysiology of progressive sensorineural hearing loss in EED and EES syndrome, we measured the volume of the EED and EES, the diameter of the EED and EES, the area of the cochlear modiolus, and the signal intensity of the EES and compared our findings against degree of hearing loss.

METHODS: Thin-section MR images of 33 ears in 17 patients with EED and EES syndrome were studied. All studies were obtained on a 1.5-T MR unit using a quadrature surface phased-array coil. Heavily T2-weighted 3D fast asymmetric spin-echo images were obtained with a voxel size of 0.3 x 0.3 x 0.8 mm without zero-fill interpolation. Two radiologists traced the areas of the EED and EES manually, and the volume was calculated. The area of the cochlear modiolus, diameter of the EED and EES, and signal intensity of the EES were also measured by drawing regions of interest manually. The signal intensity ratio of EES/CSF was calculated. These measured values were compared against audiographic data, and the degree of linear correlation was determined.

RESULTS: The volume of the EED and EES, the area of the modiolus, the diameter of the EED and EES, and the signal intensity of the EES did not show significant correlation with degree of hearing loss.

CONCLUSION: These findings suggest that there is a microscopic area of damage or fragility in the inner ear not visible even with thin-section heavily T2-weighted MR imaging.