The Morphology Study Of Internal Auditory Canal And Assessment Of Auditory Pathway By Diffusion Tensor Imaging Of Cogenital Sensorineural Hearing Loss Children

Objective:To investigate the development status of bilateral cochlear nerve (CN) and internal auditory canal (IAC) in children with congenital sensorineural hearing loss, and to explore the relationship between development of CN and age. To assess the central auditory pathway in children with CSNHL by diffusion tensor imaging (DTI). To investigate integrity and damage of the auditory fiber bundle and changes of micro structure white matter in after congrntal hearing loss.Methods:43 children with CSNHL and 15 controls were scaned by German company Siemens Magnetom Trio Tim MR 3.0T scanner. The examine sequence include T1-weighted sequence, T2-weighted sequence, T2-SPACE sequence (CISS) and EPI.3D-FLASH sequence [TR/TE 300/2.5 ms, matrix 320×320], T2WI sequence [TR/TE 6000/93 ms, matrix 640x640]. T2-SPACE sequence parameters:[TR/TE 1000/132ms, matrix 200x200]. EPI sequence parameters included TR/TE 10500/103ms, spatial resolution 1.8×1.8×1.8LP/mm, b values were 0 and 1000 s/mm2. Transverse diameter, cross-sectional area and cross section perimeter were measured for bilateral CN of all subjects; transverse diameter and vertical diameter of bilateral IAC were also measured. DTI parameters were measured on the trapezoid body (TB), superior olivary nucleus (SON), the inferior colliculus (IC), medial geniculate body (MGB), white matter of transverse temporal gyri (WTG). The DTI parameters include fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial diffusivity (λ〃), mean diffusivity (λ⊥). The difference between the size of left and right of CN and IAC was compared using t-test. The CSNHL patients were grouped according to two standard:①IAC structure②the sensation to sound. The different size of CN among the groups were compared using LSD-test. To analyze the correlation between the CN and IAC size using Pearson correlation. The difference between left and right side of DTI parameters of 5 ROIs was compared using t-test. The different of DTI parameters among the groups were compared using LSD-test. To analyze the correlation between the FA and age using Pearson product moment.Results:1.Among the 43 cases of CSNHL group,16 cases had inner ear malformations.2. Of two groups, the difference between left and right of the indexes was no significant (P>0.05). The indexes included diameter, cross-sectional area, perimeter of CN and cross-sectional diameter, vertical diameter of IAC.3. Patients with CSNHL which had the normal IAC structure was definited GroupⅠ. Patients with CSNHL which had abnormal IAC structure was definited GroupⅡ. The NC group was definited GroupⅢ. The difference of CN's diameter, cross-sectional area and perimeter among the groups has statistical significance (P<0.05). CN size of groupⅠ,Ⅱwere smaller than the groupⅢ(P<0.05). Left CN cross-sectional area of groupⅠwas larger than it of groupⅡ(P<0.05).4. Group A was the CSNHL patients who can feel sound. Group B was the patients who totally can not feel sound. Group C was NC group. The difference of CN size among the groups has statistical significance (P<0.05).5. Compared with NC group, cross-sectional area of CSNHL group had no significant relationship with age.6. The left CN area of CSNHL group had linear relationship with IAC size.7. In CSNHL group, the difference between left and right of FA, ADC,λ〃,λ⊥of IC, WTG was significant (P> 0.05). In NC group, the difference between left and right of FA, ADC,λ〃,λ⊥of WTG was significant (P> 0.05).8. Expect TB, the difference of FA of other 4 ROIs among the three group was significant (P> 0.05). The FA value of group A and B were smaller the it of group C. Expect WTG, the difference ofλ⊥of other 4 ROIs among the three group was significant (P> 0.05). Theλ⊥alue of group A and B were larger the it of group C. The difference of DTI parameters of 5 ROIs has no statistical significance (P>0.05).9. In NC group, FA of 5 ROIs has had linear relationship with age. While in CSNHL group, FA of 5 ROIs had no significant relationships with age.Conclusion:CN's size of CSNHL patients changed, slightly smaller than the NC group. IAC structure may affect the development of the auditory nerve. FA values of left, right brain asymmetry of children is inherent. Auditory nerve fibers of CSNHL group destroyed, but the fibers were still intact.IC is the most sensitive parts of the nerve injury. Weak sound stimulation had no significant effect on development of auditory pathway.