Sensorineural hearing loss is the most frequent sensory deficit of childhood and is of genetic origin in up to 75% of cases. It has been shown that mutations of the SLC26A4 (PDS) gene were involved in syndromic deafness characterized by congenital sensorineural hearing impairment and goitre (Pendred's syndrome), as well as in congenital isolated deafness (DFNB4). While the prevalence of SLC26A4 mutations in Pendred's syndrome is clearly established, it remains to be studied in large cohorts of patients with nonsyndromic deafness and detailed clinical informations. In this report, 109 patients from 100 unrelated families, aged from 1 to 32 years (median age: 10 years), with nonsyndromic deafness and enlarged vestibular aqueduct, were genotyped for SLC26A4 using DHPLC molecular screening and sequencing. In all, 91 allelic variants were observed in 100 unrelated families, of which 19 have never been reported. The prevalence of SLC26A4 mutations was 40% (40/100), with biallelic mutation in 24% (24/100), while six families were homozygous. All patients included in this series had documented deafness, associated with EVA and without any evidence of syndromic disease. Among patients with SLC26A4 biallelic mutations, deafness was more severe, fluctuated more than in patients with no mutation. In conclusion, the incidence of SLC26A4 mutations is high in patients with isolated deafness and enlarged vestibular aqueduct and could represent up to 4% of nonsyndromic hearing impairment. SLC26A4 could be the second most frequent gene implicated in nonsyndromic deafness after GJB2, in this Caucasian population.

A 100 Hz bone conducted vibration (BCV) applied to either mastoid induces instantaneously a predominantly horizontal nystagmus, with quick phases beating away from the affected side in patients with a unilateral vestibular loss (UVL). The same stimulus in healthy asymptomatic subjects has little or no effect. This is skull vibration induced nystagmus (SVIN) and it is a useful, simple, non-invasive, robust indicator of asymmetry of vestibular function and the side of the vestibular loss. The nystagmus is precisely stimulus-locked: it starts with stimulation onset and stops at stimulation offset, with no post-stimulation reversal. It is sustained during long stimulus durations; it is reproducible; it beats in the same direction irrespective of which mastoid is stimulated; it shows little or no habituation; it is permanent – even well compensated UVL patients show SVIN. A SVIN is observed under Frenzel-goggles or videonystagmoscopy and recorded under videonystagmography in absence of visual-fixation and strong sedative drugs. Stimulus frequency, location, and intensity modify the results and a large variability in skull morphology between people can modify the stimulus. SVIN to 100 Hz mastoid stimulation is a robust response. We describe the optimum method of stimulation on the basis of the literature data and testing more than 18,500 patients. Recent neural evidence clarifies which vestibular receptors are stimulated, how they cause the nystagmus, why the same vibration in patients with semicircular canal dehiscence (SCD) cause a nystagmus beating towards the affected ear. This review focuses on the optimal parameters of the stimulus and response of UVL and SCD patients, but also shows how other vestibular dysfunctions affect SVIN. We conclude that the presence of SVIN is a useful indicator of the symmetry of vestibular function between the two ears, but in order to identify which is the affected ear, other information and careful clinical judgement is needed.

To compare the incidence of dislocation of precurved versus straight flexible cochlear implant electrode arrays using cone-beam computed tomography (CBCT) image analyses. Consecutive nonrandomized case-comparison study. Tertiary referral center. Analyses of patients' CBCT images after cochlear implant surgery. Precurved and straight flexible electrode arrays from two different manufacturers were implanted. A round window insertion was performed in most cases. Two cases necessitated a cochleostomy. The patients' CBCT images were reconstructed in the coronal oblique, sagittal oblique, and axial oblique section. The insertion depth angle and the incidence of dislocation from the scala tympani to the scala vestibuli were determined. The CBCT images and the incidence of dislocation were analyzed in 54 patients (61 electrode arrays). Thirty-one patients were implanted with a precurved perimodiolar electrode array and 30 patients with a straight flexible electrode array. A total of nine (15%) scalar dislocations were observed in both groups. Eight (26%) scalar dislocations were observed in the precurved array group and one (3%) in the straight array group. Dislocation occurred at an insertion depth angle between 170 and 190 degrees in the precurved array group and at approximately 370 degrees in the straight array group. With precurved arrays, dislocation usually occurs in the ascending part of the basal turn of the cochlea. With straight flexible electrode arrays, the incidence of dislocation was lower, and it seems that straight flexible arrays have a higher chance of a confined position within the scala tympani than perimodiolar precurved arrays.

Hearing loss is the most frequent sensory deficit. One child in 1000 is born with severe or profound deafness, and another 1 in 1000 becomes deaf before adulthood. Recent work in human genetics indicates that 60% to 80% of cases of congenital deafness are of genetic origin in developed countries1 and that nonsyndromic sensorineural hearing loss (NSSNHL) is mainly autosomal recessive. Since 1994, more than 80 loci for NSSNHL have been identified, and 35 different genes have been cloned.1 Despite extensive genetic heterogeneity, a single locus on chromosome band 13q12 has been recognized to account for a large proportion of cases of nonsyndromic autosomal recessive deafness (DFNB1). Furthermore, the gene that encodes connexin 26, GJB2, has been identified as causative in DFNB1.1 The GJB2 gene is also involved in an autosomal dominant form of deafness, DFNA3, and in syndromes such as Vohwinkel or keratitis-ichtyosis-deafness syndrome. The GJB6 gene, which encodes connexin 30, maps close to GJB2. The GJB6 gene was first described as causative in a rare dominant form of deafness, DFNA3, and its implication in NSSNHL was ascertained through the identification of a large deletion that includes the GJB6 5′-end noncoding region and most of the coding region. This genetic alteration was found in patients with hearing impairment who carry a GJB2 mutation in trans and at a homozygous state in some families.2-4 In those patients, it is still not clear whether the deafness is due to a digenic pattern of inheritance or whether the deletion removes common GJB6 and GJB2 regulatory elements.5