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AJNR - American Journal of Neuroradiology

Published ahead of print on July 2, 2009
doi: 10.3174/ajnr.A1681

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American Journal of Neuroradiology 30:1773-1777, October 2009
© 2009 American Society of Neuroradiology

HEAD AND NECK

Diffusion Tensor Imaging of the Subcortical Auditory Tract in Subjects with Congenital Cochlear Nerve Deficiency

C.-M. Wu^a, S.-H. Ng^b,c, J.-J. Wang^b,c and T.-C. Liu^d

^aFrom the Department of Otolaryngology (C.-M.W.), College of Medicine
^bMolecular Imaging Center (S.-H.N., J.-J.W.) and Departments of Diagnostic Radiology, and Medical Imaging
^cRadiological Sciences (S.-H.N., J.-J.W.), Chang-Gung University, Linkou, Taiwan
^dDepartment of Otolaryngology (T.-C.L.), National Taiwan University Hospital, Taipei, Taiwan.

Please address correspondence to: Tien-Chen Liu, MD, Department of Otolaryngology, National Taiwan University Hospital, Taipei, Taiwan; e-mail: liuent{at}ntu.edu.tw

BACKGROUND AND PURPOSE: Cochlear nerve deficiency (CND), including aplasia and hypoplasia, is a rare cause of congenital hearing loss. The purpose of this study was to evaluate the neuronal integrity of the subcortical auditory pathway in subjects with CND by diffusion tensor MR imaging (DTI).

MATERIALS AND METHODS: Twelve subjects with unilateral congenital CND were included in this prospective study. Twelve normal-hearing subjects served as controls. DTIs were acquired from these subjects on a 3T MR imaging scanner. Several indices including axial diffusivity (_||), radial diffusivity (), mean diffusivity (MD), and fractional anisotropy (FA) along the auditory pathway were extracted. Two regions of interest were selected bilaterally for evaluation: the lateral lemniscus (LL) and inferior colliculus (IC). The mean values of _||, , MD, and FA at both regions of interest were compared between the ipsilateral and contralateral sides of subjects with CND with those in the control group.

RESULTS: Significant decrease of FA and increase of MD on both the ipsilateral and contralateral sides of patients with CND as compared with normal subjects in both LL and IC were found. The decrease of FA was due to the increase of , whereas _|| remained unchanged.

CONCLUSIONS: The maintained axial diffusion implied that the orientation of neural fibers along the subcortical auditory pathway in subjects with unilateral CND is intact. However, the reduction in FA and increase in on both the ipsilateral and contralateral sides might be attributed to axonal loss and/or demyelination of the subcortical auditory tract in these subjects.