Re-Examining the Cochlea in Branchio-Oto-Renal Syndrome: Genotype-Phenotype Correlation

Etiology of Childhood Profound Sensorineural Hearing Loss: The Role of Hearing Loss Gene Panel Testing

OBJECTIVE

Establishing the cause of hearing loss (HL) is important and rewarding, though not without its challenges. While our ability to identify the etiology for HL has improved with advances in scientific knowledge, a significant proportion of cases remain of unknown etiology. Recent protocol changes within the NHS Genomic Medicine Service support the utilization of the HL gene panel test, rather than individual gene tests. In light of these changes, determining the yield of these more extensive panel tests is important in informing future practice.

STUDY DESIGN

Retrospective study.

SETTING

The Cochlear Implant (CI) Department at Great Ormond Street Hospital (GOSH).

METHODS

Four hundred seventy-six children with profound HL were identified from a database of referrals to the GOSH CI Department. Data on etiology of HL including genetic diagnosis was collected from hospital notes on an electronic patient records system and hospital genetics database.

RESULTS

We identified a positive result in 163/476 (34%) cases through the gene panel test, representing an additional 19% yield to current level 1 investigations. Genetic HL, including both syndromic (including those not covered by the HL gene panel) and nonsyndromic (209/476, 44%) was the most common etiology in our cohort. Perinatal, intrauterine, ototoxicity, meningitis, and encephalitis categories altogether comprised 97/476 (20%) cases.

CONCLUSION

Gene panel testing provides significant additional yield over current level 1 investigations which include GJB2 testing only. This has far-reaching implications for how we optimize investigations into HL in children and counsel families, and for future early interventions.

Conductive Hearing Loss in Children

A variety of congenital and acquired disorders result in pediatric conductive hearing loss. Malformations of the external auditory canal are invariably associated with malformations of the middle ear space and ossicles. Isolated ossicular malformations are uncommon. Syndromes associated with external and middle ear malformations are frequently associated with abnormal development of first and second pharyngeal arch derivatives. Chronic inflammatory disorders include cholesteatoma, cholesterol granuloma, and tympanosclerosis.

Syndromic Hearing Loss in Children

Pattern recognition of specific temporal bone radiological phenotypes, in association with abnormalities in other organ systems, is critical in the diagnosis and management of syndromic causes of hearing loss. Several recent publications have demonstrated the presence of specific radiological appearances, allowing precise genetic and/or syndromic diagnosis, in the right clinical context. This review article aims to provide an extensive but practical guide to the radiologist dealing with syndromic causes of hearing loss.

The spectrum of cochlear malformations in CHARGE syndrome and insights into the role of the CHD7 gene during embryogenesis of the inner ear

PURPOSE

We reviewed the genotypes and the imaging appearances of cochleae in CHARGE patients from two large tertiary centres and analysed the observed cochlear anomalies, providing detailed anatomical description and a grading system. The goal was to gain insight into the spectrum of cochlear anomalies in CHARGE syndrome, and thus, in the role of the CHD7 gene in otic vesicle development.

METHODS

We retrospectively reviewed CT and/or MR imaging of CHARGE patients referred to our institutions between 2005 and 2022. Cochlear morphology was analysed and, when abnormal, divided into 3 groups in order of progressive severity. Other radiological findings in the temporal bone were also recorded. Comparison with the existing classification system of cochlear malformation was also attempted.

RESULTS

Cochlear morphology in our CHARGE cohort ranged from normal to extreme hypoplasia. The most common phenotype was cochlear hypoplasia in which the basal turn was relatively preserved, and the upper turns were underdeveloped. All patients in the cohort had absent or markedly hypoplastic semicircular canals and small, misshapen vestibules. Aside from a stenotic cochlear aperture (fossette) being associated with a hypoplastic or absent cochlear nerve, there was no consistent relationship between cochlear nerve status (normal, hypoplasia, or aplasia) and cochlear morphology.

CONCLUSION

Cochlear morphology in CHARGE syndrome is variable. Whenever the cochlea was abnormal, it was almost invariably hypoplastic. This may shed light on the role of CHD7 in cochlear development. Accurate morphological description of the cochlea contributes to proper clinical diagnosis and is important for planning surgical treatment options.

Subtle Malformation of the Cochlear Apex and Genetic Abnormalities: Beyond the "Thorny" Cochlea

With the routine use of high-resolution heavily T2-weighted sequences to evaluate patients with hearing deficits, new, subtle phenotypes of cochlear malformations are being discovered and an increasing number of genotype-phenotype correlations are being found through a reverse phenotype approach, which can help guide geneticists. In this brief report, we present subtle malformations of the apical turn of the cochlea related to 3 genetic mutations, emphasizing the importance of a careful assessment of the cochlear apex.

The Cochlea in Branchio-Oto-Renal Syndrome: An Objective Method for the Diagnosis of Offset Cochlear Turns

BACKGROUND AND PURPOSE

An "unwound" or "offset" cochlea has been described as a characteristic imaging feature in patients with branchio-oto-renal syndrome, and recently recognized to be associated in particular to those with EYA1 gene mutations. Determination of this feature has traditionally relied on subjective visual assessment. Our aim was to establish an objective assessment method for cochlear offset (the cochlear turn alignment ratio) and determine an optimal cutoff turn alignment ratio value that separates individuals with EYA1-branchio-oto-renal syndrome from those with SIX1-branchio-oto-renal syndrome and healthy controls.

MATERIALS AND METHODS

Temporal bone CT or MR imaging from 40 individuals with branchio-oto-renal syndrome and 40 controls was retrospectively reviewed. Cochlear offset was determined visually by 2 independent blinded readers and then quantitatively via a standardized technique yielding the cochlear turn alignment ratio. The turn alignment ratio values were compared between cochleae qualitatively assessed as "not offset" and "offset." Receiver operating characteristic analysis was used to determine the ability of the turn alignment ratio to differentiate between these populations and an optimal cutoff turn alignment ratio value. Cochlear offset and turn alignment ratio values were analyzed for each branchio-oto-renal syndrome genotype subpopulation and for controls.

RESULTS

The turn alignment ratio can accurately differentiate between cochleae with and without an offset (P < .001). The optimal cutoff value separating these populations was 0.476 (sensitivity = 1, specificity = 0.986, J = 0.986). All except 1 cochlea among the EYA1-branchio-oto-renal syndrome subset and all with unknown genotype branchio-oto-renal syndrome had a cochlear offset and a turn alignment ratio of <0.476. All except 1 cochlea among the SIX1-branchio-oto-renal syndrome subset and all controls had no offset and a turn alignment ratio of >0.476.

CONCLUSIONS

There is a statistically significant difference in turn alignment ratios between offset and nonoffset cochleae, with an optimal cutoff of 0.476. This cutoff value allows excellent separation of EYA1-branchio-oto-renal syndrome from SIX1-branchio-oto-renal syndrome and from individuals without branchio-oto-renal syndrome or sensorineural hearing loss. The turn alignment ratio is a reliable and objective metric that can aid in the imaging evaluation of branchio-oto-renal syndrome.