Cochlear implantation and single-sided deafness.

Purpose Of Review: Recently, more patients with single-sided deafness (SSD) have been undergoing cochlear implantation. We review recent studies and case reports to provide an overview of the efficacy of cochlear implants to rehabilitate patients with SSD with regards to sound localization, speech discrimination, and tinnitus suppression.

Recent Findings: There are a growing number of studies evaluating the effect of cochlear implantation for rehabilitation of the deficits associated with SSD over the past several years as more centers offer this treatment modality to patients with SSD.

Resection of the innominate artery to prevent an impending tracheoinnominate fistula and to permit tracheotomy in a patient with subglottic stenosis and high-riding innominate.

Objective: This study aimed to determine the long-term viability of innominate artery resection and tracheotomy for a patient at high risk of developing a tracheoinnominate fistula (TIF) in the setting of subglottic stenosis and a high-riding innominate artery.

Methods: Chart review with 2-year follow-up.

Results: A 45-year-old diabetic man with obstructive sleep apnea and multiple admissions for coma and delirium tremens associated with alcohol abuse developed subglottic stenosis.

The mechanotransduction machinery of hair cells.

Mechanotransduction, the conversion of mechanical force into an electrochemical signal, allows living organisms to detect touch, hear, register movement and gravity, and sense changes in cell volume and shape. Hair cells in the vertebrate inner ear are mechanoreceptor cells specialized for the detection of sound and head movement. Each hair cell contains, at the apical surface, rows of stereocilia that are connected by extracellular filaments to form an exquisitely organized bundle.

Tip links in hair cells: molecular composition and role in hearing loss.

Purpose Of Review: Tip links are thought to be an essential element of the mechanoelectrical transduction (MET) apparatus in sensory hair cells of the inner ear. The molecules that form tip links have recently been identified, and the analysis of their properties has not only changed our view of MET but also suggests that tip-link defects can cause hearing loss.

Recent Findings: Structural, histological and biochemical studies show that the extracellular domains of two deafness-associated cadherins, cadherin 23 (CDH23) and protocadherin 15 (PCDH15), interact in trans to form the upper and lower part of each tip link, respectively.

A mouse model for nonsyndromic deafness (DFNB12) links hearing loss to defects in tip links of mechanosensory hair cells.

Deafness is the most common form of sensory impairment in humans and is frequently caused by single gene mutations. Interestingly, different mutations in a gene can cause syndromic and nonsyndromic forms of deafness, as well as progressive and age-related hearing loss. We provide here an explanation for the phenotypic variability associated with mutations in the cadherin 23 gene (CDH23).

Dynamic compartmentalization of protein tyrosine phosphatase receptor Q at the proximal end of stereocilia: implication of myosin VI-based transport.

Hair cell stereocilia are apical membrane protrusions filled with uniformly polarized actin filament bundles. Protein tyrosine phosphatase receptor Q (PTPRQ), a membrane protein with extracellular fibronectin repeats has been shown to localize at the stereocilia base and the apical hair cell surface, and to be essential for stereocilia integrity. We analyzed the distribution of PTPRQ and a possible mechanism for its compartmentalization.

Cadherin 23 and protocadherin 15 interact to form tip-link filaments in sensory hair cells.

Hair cells of the inner ear are mechanosensors that transduce mechanical forces arising from sound waves and head movement into electrochemical signals to provide our sense of hearing and balance. Each hair cell contains at the apical surface a bundle of stereocilia. Mechanoelectrical transduction takes place close to the tips of stereocilia in proximity to extracellular tip-link filaments that connect the stereocilia and are thought to gate the mechanoelectrical transduction channel.

Unbiased stereological estimation of the spiral ligament and stria vascularis volumes in aging and Ménière's disease using archival human temporal bones.

The present study applies the unbiased stereological technique-Cavalieri principle to measure the volumes of the stria vascularis (SV) and the spiral ligament (SL) using postmortem archival human temporal bones from normal young and older subjects and subjects with Ménière's disease. Normative data was obtained from subjects without ages ranging from 15 to 84 years old who had no history of audiovestibular disease (N=25). For comparison purposes, the normative specimens were divided into three groups: group 1 (n=8) had ages ranging from 15 to 38 years old, average age=23.

Regional estimates of hair cells and supporting cells in the human crista ampullaris.

Regional estimates of type I and type II vestibular hair cells (HC) and supporting cell (SC) numbers were obtained from the horizontal crista ampullaris by using design-based stereology in human. Cristae were microdissected from temporal bones obtained post-mortem (N=16, age range 26-98 years). Three groups were made according to age: group 1, n=5, ages between 26 and 67 years, average age 51 years; group 2, n=4, average age 84 years; and group 3, n=7, average age 94 years.