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

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Fig 1.
Representative 3D MR images of cochlear nerve (N) aplasia (A), hypoplasia (B), and the normal cochlear nerve (C). Arrows indicate the cochlear nerve and facial nerve in the internal auditory canal. B, The caliber of the cochlear nerve is smaller than that of the facial nerve, which is the diagnostic criterion for cochlear nerve hypoplasia.
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Fig 2.
A, A sample DTI at the level of the LL and the selected region of interest (3 × 3 × 2 mm rectangular box). Note that in the DTIs, the most basic red-green-blue color-coded scheme attributes a color to each orientation of the fibers: Fibers crossing from left to the right are shown in red, fibers crossing anteroposteriorly are visualized in green, and fibers crossing inferosuperiorly are visualized in blue.³⁰ B, In the corresponding T1-weighted MR image at the same sectional level, long arrows pinpoint the anatomic sites of lateral lemniscus. C, The corresponding T2-weighted image at the same section level.
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Fig 3.
A, A sample DTI at the level of the IC and the selected area of region of interest. B, In the corresponding T1-weighted MR image at the same sectional level, long arrows pinpoint the anatomic sites of the IC. C, The corresponding T2-weighted image at the same sectional level.

Table 1:

Basic clinical data of all subjects with unilateral cochlear nerve deficiency (aplasia and hypoplasia)

Case	Age (yr)	Sex	Cochlear Nerve Deficiency		Hearing Threshold (PTA) dB HL
Case	Age (yr)	Sex	Right	Left	Right	Left
1	12	M	Aplasia	Normal	100	10
2	10	F	Aplasia	Normal	>100	20
3	8	F	Aplasia	Normal	>100	10
4	9	F	Aplasia	Normal	>110	15
5	14	F	Hypoplasia	Normal	100	5
6	8	M	Hypoplasia	Normal	>110	10
7	12	M	Normal	Aplasia	5	>110
8	25	F	Aplasia	Normal	100	10
9	9	M	Normal	Aplasia	10	>110
10	11	M	Normal	Aplasia	10	>110
11	29	M	Normal	Aplasia	15	>110
12	9	F	Hypoplasia	Normal	90	10

Table 2:

Summary of the diffusion indices at the LL and IC for the unilateral CND group*

Note:—LL indicates lateral lemniscus; IC, inferior colliculus; CND, cochlear nerve deficiency; SEM, standard error of the mean; λ_‖, axial diffusivity; l⊥ _, radial diffusivity; MD, mean diffusivity; FA, fractional anisotropy.
* The contralateral side of the patients was compared with that in the control group.
† Statistically significant.

Table 3:

Summary of the diffusion indices (mean and SEM) at the LL and IC for the unilateral CND group*