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      Diffusion Tensor Imaging of the Auditory Neural Pathway for Clinical Outcome of Cochlear Implantation in Pediatric Congenital Sensorineural Hearing Loss Patients

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          Abstract

          Although conventional structural MRI provides vital information in the evaluation of congenital sensorineural hearing loss (SNHL), it is relatively insensitive to white matter microstructure. Our objective was to evaluate possible changes in microstructure of the auditory pathway in children with congenital sensorineural hearing loss (SNHL), and the possible distinction between good and poor outcome of cochlear implantation (CI) patients by using diffusion tensor imaging (DTI). Twenty-four patients with congenital SNHL and 20 healthy controls underwent conventional MRI and DTI examination using a 1.5T MR scanner. The DTI metrics of fractional anisotropy (FA) and mean diffusivity (MD) of six regions of interest (ROIs) positioned along the auditory pathway—the trapezoid body, superior olivary nucleus, inferior colliculus, medial geniculate body, auditory radiation and white matter of Heschl's gyrus—was measured in all subjects. Among the 24 patients, 8 patients with a categorie of auditory performance (CAP) score over 6 were classified into the good outcome group, and 16 patients with a CAP score below 6 were classified into the poor outcome group. A significant decrease was observed in FA values while MD values remained unchanged at the six ROIs of SNHL patients compared with healthy controls. Compared to good outcome subjects, poor outcome subjects displayed decreased FA values at all of the ROIs. No changes were observed in MD values. Correlation analyses only revealed strong correlations between FA values and CAP scores, and strong correlations between CAP scores and age at implant were also found. No correlations of FA values with age at implant were observed. Our results show that preoperative DTI can be used to evaluate microstructural alterations in the auditory pathway that are not detectable by conventional MR imaging, and may play an important role in evaluating the outcome of CI. Early cochlear implantation might be more effectively to restore hearing in SNHL patients.

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          Diffusion-tensor MR imaging of gray and white matter development during normal human brain maturation.

          Conventional MR imaging findings of human brain development are thought to result from decreasing water content, increasing macromolecular concentration, and myelination. We use diffusion-tensor MR imaging to test theoretical models that incorporate hypotheses regarding how these maturational processes influence water diffusion in developing gray and white matter. Experimental data were derived from diffusion-tensor imaging of 167 participants, ages 31 gestational weeks to 11 postnatal years. An isotropic diffusion model was applied to the gray matter of the basal ganglia and thalamus. A model that assumes changes in the magnitude of diffusion while maintaining cylindrically symmetric anisotropy was applied to the white matter of the corpus callosum and internal capsule. Deviations of the diffusion tensor from the ideal model predictions, due to measurement noise, were estimated by using Monte Carlo simulations. Developing gray matter of the basal ganglia and developing white matter of the internal capsule and corpus callosum largely conformed to theory, with only small departures from model predictions in older children. However, data from the thalamus substantially diverged from predicted values, with progressively larger deviations from the model with increasing participant age. Changes in water diffusion during maturation of central gray and white matter structures can largely be explained by theoretical models incorporating simple assumptions regarding the influence of brain water content and myelination, although deviations from theory increase as the brain matures. Diffusion-tensor MR imaging is a powerful method for studying the process of brain development, with both scientific and clinical applications.
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            Beyond cochlear implants: awakening the deafened brain.

            Cochlear implants have provided hearing to more than 120,000 deaf people. Recent surgical developments include direct electrical stimulation of the brain, bilateral implants and implantation in children less than 1 year old. However, research is beginning to refocus on the role of the brain in providing benefits to implant users. The auditory system is able to use the highly impoverished input provided by implants to interpret speech, but this only works well in those who have developed language before their deafness or in those who receive their implant at a very young age. We discuss recent evidence suggesting that developing the ability of the brain to learn how to use an implant may be as important as further improvements of the implant technology.
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              A morphometric analysis of auditory brain regions in congenitally deaf adults.

              We investigated whether variation in auditory experience in humans during development alters the macroscopic neuroanatomy of primary or auditory association cortices. Volumetric analyses were based on MRI data from 25 congenitally deaf subjects and 25 hearing subjects, all right-handed. The groups were matched for gender and age. Gray and white matter volumes were determined for the temporal lobe, superior temporal gyrus, Heschl's gyrus (HG), and the planum temporale. Deaf and hearing subjects did not differ in the total volume or the gray matter volume of HG, which suggests that auditory deafferentation does not lead to cell loss within primary auditory cortex in humans. However, deaf subjects had significantly larger gray matter-white matter ratios than hearing subjects in HG, with deaf subjects exhibiting significantly less white matter in both left and right HG. Deaf subjects also had higher gray matter-white matter ratios in the rest of the superior temporal gyrus, but this pattern was not observed for the temporal lobe as a whole. These findings suggest that auditory deprivation from birth results in less myelination and/or fewer fibers projecting to and from auditory cortices. Finally, the volumes of planum temporale and HG were significantly larger in the left hemisphere for both groups, suggesting that leftward asymmetries within "auditory" cortices do not arise from experience with auditory processing.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                20 October 2015
                2015
                : 10
                : 10
                : e0140643
                Affiliations
                [1 ]Department of Radiology, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China
                [2 ]Department of E.N.T, The Second Affiliated Hospital, Medical College of Shantou University, Shantou, China
                Duke-NUS Graduate Medical School, SINGAPORE
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: WZ. Performed the experiments: LH CW X. Wei X. Wu YW HZ. Analyzed the data: LH. Wrote the paper: LH.

                Article
                PONE-D-15-14392
                10.1371/journal.pone.0140643
                4618518
                26485661
                eb3b96e4-b37e-469f-85c9-2b4470e6b710
                Copyright @ 2015

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

                History
                : 5 April 2015
                : 29 September 2015
                Page count
                Figures: 1, Tables: 5, Pages: 9
                Funding
                This study was supported by the National Natural Science Foundation of China (grant no. 81571627), Natural Science Foundation of Guangdong Province, China (grant no. S2012010008974, 2014A030313481), and was sponsored by the Shantou University Medical College Clinical Research Enhancement Initiative (2014), Shantou China, Science and Technology Planning Project of Shantou City, China (grant no. 201424260), Shantou China. WZ received the funding. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Categories
                Research Article
                Custom metadata
                All relevant data are available on Figshare ( http://dx.doi.org/10.6084/m9.figshare.1564504).

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