Purpose: To prospectively compare diffusion tensor imaging (DTI) measures of axial diffusivity (), radial diffusivity (Ќ), mean diffusivity (MD), and fractional anisotropy (FA) along the auditory pathway of patients with sensorineural hearing loss (SNHL) and normal controls. Materials and Methods:In 37 individuals with SNHL and 10 healthy controls, two regions of interest (ROIs) positioned along the auditory pathway-the lateral lemniscus (LL) and the inferior colliculus (IC)-were investigated bilaterally using diffusion tensor imaging at 3 T. SNHL patients were divided into three groups: patients with bilateral hearing loss, patients with unilateral hearing loss, and patients with partial hearing loss. DTI measures (, Ќ, MD, FA) of both ROIs were determined in all subjects. Results:The FA value was reduced and the Ќ was increased both at the lateral lemniscus and the inferior colliculus of patients with SNHL compared with controls. Similar changes were seen between the ipsilateral and contralateral LL and IC for patients of unilateral profound hearing loss. No changes were observed in any other parameters. Conclusion:In SNHL patients DTI showed a high radial diffusivity that consequently led to a decreased fractional anisotropy in the LL and the IC. HEARING IS ONE OF the most significant of human senses and represents a crucial link in communication with the outside world. The primary acoustic circuit in humans consists of the auditory nerve, brainstem, thalamus, and auditory cortex. The transduction of sound into a neural signal occurs in the cochlea, a snail-shell-like structure located within the inner ear. Auditory impulses then travel via the cochlear nerve along the internal acoustic canal through the cerebellopontine angle to synapse at the dorsal and ventral cochlear nuclei within the medulla oblongata. From there, fibers project into the ipsilateral superior olivary nucleus or decussate into the contralateral superior olivary nucleus via the trapezoid body. Both crossed and uncrossed fibers then ascend via the lateral lemniscus to the inferior colliculus in the mid-brain. Subsequently the fibers project to the medial geniculate body in the thalamus and terminate to the auditory cortex in the superior temporal Heschl gyrus.Sensorineural hearing loss (SNHL) is a disabling condition that accounts for about 90% of all hearing loss. It can be divided audiometrically into sensory (cochlear loss) and neural (retrocochlear) loss. Individuals with sensory SNHL have damage to the cochlea at a macroscopic or microscopic level. In contrast, individuals with neural SNHL have involvement of the remainder of the auditory pathway exclusive of the cochlea. Neural SNHL requires the study of the internal auditory canal, cerebellopontine angle, brain stem, thalamus, and temporal lobe (1). In this regard, the auditory pathway can be studied in the clinical setting by means of computed tomography (CT) or conventional magnetic resonance imaging (MRI). However, the causes of unilateral or bilateral SNHL may be identified by co...

Cochlear implantation is currently the treatment of choice for children with severe to profound hearing impairment. However, the outcomes with cochlear implants (CIs) vary significantly among recipients. The purpose of the present study is to identify the genetic determinants of poor CI outcomes. Twelve children with poor CI outcomes (the “cases”) and 30 “matched controls” with good CI outcomes were subjected to comprehensive genetic analyses using massively parallel sequencing, which targeted 129 known deafness genes. Audiological features, imaging findings, and auditory/speech performance with CIs were then correlated to the genetic diagnoses. We identified genetic variants which are associated with poor CI outcomes in 7 (58%) of the 12 cases; 4 cases had bi-allelic PCDH15 pathogenic mutations and 3 cases were homozygous for the DFNB59 p.G292R variant. Mutations in the WFS1, GJB3, ESRRB, LRTOMT, MYO3A, and POU3F4 genes were detected in 7 (23%) of the 30 matched controls. The allele frequencies of PCDH15 and DFNB59 variants were significantly higher in the cases than in the matched controls (both P < 0.001). In the 7 CI recipients with PCDH15 or DFNB59 variants, otoacoustic emissions were absent in both ears, and imaging findings were normal in all 7 implanted ears. PCDH15 or DFNB59 variants are associated with poor CI performance, yet children with PCDH15 or DFNB59 variants might show clinical features indistinguishable from those of other typical pediatric CI recipients. Accordingly, genetic examination is indicated in all CI candidates before operation.