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MR Evaluation of Vestibulocochlear Anomalies Associated with Large Endolymphatic Duct and Sac

H. Christian DavidsonGo,a, H. Ric Harnsbergera, Marc M. Lemmerlinga, Anthony A. Mancusoa, David K. Whitea, Karen A. Tonga, Richard T. Dahlena and Clough Sheltona

a From the Department of Radiology, 1A 71 Medical Center, University of Utah, Salt Lake City, UT 84132.



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  		FIG 1. Large endolymphatic duct and sac.

A, High-resolution axial temporal bone CT scan of the left ear in a patient with LEDS shows enlargement of the bony vestibular aqueduct (large arrow). The scalloped contour of the posterior temporal bone (small arrows) is created by the enlarged endolymphatic sac, although the sac itself is not discernible on the CT scan.

B, Corresponding high-resolution axial temporal bone T2-weighted FSE MR image shows enlargement of the endolymphatic duct (arrow) and sac (arrowhead).

(Reprinted from [22] with permission.)



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  		FIG 2. Axial high-resolution T2-weighted FSE MR image of a normal right inner ear at the midmodiolar level shows the normal cochlea and vestibule. The fluid-filled chambers of the cochlea are hyperintense and display the characteristic cochlear outline. The modiolus (white arrow with black outline) appears as a hypointense soft-tissue plug at the base of the cochlear spiral. Single straight white arrow indicates interscalar septum. The membranous vestibule (V) is ovoid in shape. The lateral (solid white arrowhead) and posterior (open white arrowhead) semicircular canals are visible. Double arrows indicate small segment of the normal endolymphatic duct; cochlear nerve (solid black arrowhead) and inferior vestibular nerve (open black arrowhead) are branches of the eighth cranial nerve; the tympanic segment of the seventh cranial nerve (curved arrow) is faintly seen; and the anterior inferior cerebellar artery (black arrow) is seen in its typical location near the porus acusticus.(Reprinted from [22] with permission.)



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  		FIG 3. Modiolar deficiency with LEDS.

A, Axial T2-weighted FSE MR image of the left inner ear in a patient with LEDS shows mild modiolar deficiency. The modiolus (arrow) appears attenuated and flattened, unlike the normal modiolus seen in figure 2. The endolymphatic duct (section mark) and sac (asterisk) are markedly enlarged.

B, Axial T2-weighted FSE MR image in another patient shows moderate modiolar deficiency with near absence of the normal soft-tissue core at the central cochlear axis (arrow). Asterisk indicates endolymphatic sac.

(Reprinted from [22] with permission.)



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  		FIG 4. Cochlear dysplasia with LEDS.

A, Axial T2-weighted FSE MR image of the right inner ear in a patient with LEDS shows mild dysplasia. The cochlear outline is distorted, and the normal notch between the middle and apical turns laterally (white arrow) is blunted. Note that the modiolus is deficient (black arrow).

B, Axial T2-weighted FSE MR image in another patient shows severe dysplasia. The cochlea (C) appears as a common cavity, the internal architecture is lost, and the modiolus is absent. The vestibule also shows severe dysplastic changes, including gross vestibular enlargement (V) and hypoplasia of the lateral semicircular canal (arrowhead). A portion of the enlarged endolymphatic duct is also apparent (asterisk).

(Reprinted from [22] with permission.)



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  		FIG 5. Scalar asymmetry with LEDS.

A, Axial T2-weighted FSE MR image of the left inner ear in a patient with LEDS shows enlargement of the anterior scalar chamber (arrow). The anterior chamber is composed of the scala vestibuli and scala media. The endolymphatic sac (asterisk) is markedly enlarged.

B, Axial image 2 mm below A also shows asymmetric enlargement of the anterior chamber (arrow). The posterior chamber (arrowhead) comprises the scala tympani, which is normal in size. Asterisk indicates endolymphatic sac.

(Reprinted from [22] with permission.)



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  		FIG 6. Vestibular dysplasia with LEDS.

A, Axial T2-weighted FSE MR image of the right inner ear in a patient with LEDS shows enlargement of the membranous vestibule. The ratio of the transverse dimension of the membranous vestibule (black arrow) to the inner diameter of the lateral semicircular canal (white arrow) is increased. Dysplasia of the cochlea is also apparent, manifest as a scala communis, or unpartitioned scalar chamber at the apex (arrowhead).

B, Axial T2-weighted FSE MR image in another patient shows severe vestibular dysplasia. The membranous vestibule (V) is enlarged and distorted, and the lateral semicircular canal (arrowhead) is hypoplastic. Marked enlargement of the endolymphatic duct and sac is apparent (asterisk).

(Reprinted from [22] with permission.)





Copyright © 2009 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X