Did you ever imagine your life with eerie silence, a world without a melodious birds chirping, the soothing sounds of raindrops, a gentle conversation with people, no music, no laughter but just silence? But it is a reality for people living with hearing impairment.
Congenital hearing impairment is defined as a hearing loss present from birth which is a chronic condition observed in children. There are various factors involved in newborns with hearing impairment which includes: Genetics, birth injuries, infections (such as HSV/Rubella), premature birth, preeclampsia, anoxia., etc.1 However, genetics play the major in hearing impairment, where 50% cases are mostly related to it. Carrier gene may be from both the parents or anyone of them or may be formed due to mutation.
Types of diagnosis in congenital hearing impairment:
Approximately 70% of genetic hearing loss is non-syndromic and the GJB2 gene (encoding connexin 26), is the most common genetic cause of congenital hearing loss. If in case of suspected non-syndromic hearing loss, molecular diagnostic testing should consider single-gene testing for GJB2 gene analysis.
Syndromic hearing loss diagnosis requires a syndrome-specific genetic work-up. The most common aetiologies are:
Usher syndrome (associated with visual loss).
Pendred syndrome (characterized by enlarged vestibular aqueducts and potential hypothyroidism manifesting in teenage years).
Advances in high-throughput sequencing enable simultaneous analysis of multiple sensorineural hearing loss (SNHL) causing genes. A two-tiered approach is often used:
Tier 1: Evaluate GJB2 (connexin 26) and GJB6 (connexin 30), the most prevalent SNHL causing genes.
Tier 2: Utilize next-generation sequencing to screen multiple genes linked to hearing loss, if first-tier results are negative.
A comprehensive medical history is essential to determine the aetiology of congenital hearing loss, particularly in non-genetic cases such as infectious factors (e.g., maternal rubella, cytomegalovirus, toxoplasmosis), perinatal factors (prematurity, NICU stay), other causes (e.g., birth asphyxia, congenital anomalies).
Congenital cytomegalovirus (CMV) infection is the leading non-genetic cause of hearing loss, accounting for 10-21% of congenital cases.
NICU infants are at elevated risk for hearing loss due to associations with low birth weight, birth asphyxia/hypoxia, hyperbilirubinemia, extracorporeal membrane oxygenation (ECMO) therapy, sepsis history, exposure to ototoxic medications.
Diagnostic imaging (CT, MRI) plays a crucial role in evaluating congenital hearing loss to identify anatomical structure, inner ear morphology, temporal bone anomalies.
Computed Tomography (CT) scans for congenital hearing impairment:
Evaluate bony anomalies.
Radiation exposure is a consideration.
Alternative imaging modalities (e.g., MRI) may be preferred, especially for children.
Magnetic Resonance Imaging (MRI) scans for congenital hearing impairment:
Provide high-resolution soft tissue images.
Improve visualization of inner ear structures.
Enhance detection of soft tissue abnormalities.
Radiation free imaging modality.
MedBound Times reached out to Dr Neha Sood on her insights on congenital hearing impairment.
Treatment for restoring the hearing loss:
Hearing restoration can be achieved through: Hearing aids, Cochlear implants, Bone-anchored hearing aids.
Hearing aids: The American Academy of Audiology recommends behind the ear (BTE) hearing aids for paediatric patients due to minimized swallowing risk in young children and bilateral hearing aids recommended for bilateral hearing loss for the improvement of binaural hearing, enhanced auditory localization, and easier communication in noisy environments.
Paediatric working group (audiologists, paediatricians, otolaryngologists, and genetic counsellors) suggests regular audiologic assessments for every 3 months in the first 2 years of hearing aid use to monitor auditory development, hearing aid fitting accuracy, ear canal growth, and timeline for this can be adjusted for emerging concerns and elevated risk of progressive hearing loss.2
Cochlear implants: Cochlear implantation is the first effective standard care for children with severe profound congenital hearing loss which is not only clinically effective but also cost effective. Unilateral cochlear implants significantly improve hearing and quality of life. whereas, Bilateral cochlear implants provide substantial benefits in sound localization and hearing in noise.
Bone-anchored hearing aids (BAHA): Bone-anchored hearing aids offer varying levels of benefit depending on underlying cochlear function. Children with pure tone bone-conduction averages better than 45 dB typically experience excellent benefits, while those with averages between 45-60 dB receive intermediate benefits. However, those with averages above 60 dB may have limited benefits. It plays a crucial role in the rehabilitation of unilateral sensorineural hearing loss. This innovative device improves hearing and communication abilities, significantly enhancing the quality of life for affected individuals.3
Dr Neha says once hearing loss is detected, it should be corrected or treated as early as possible. Because hearing is one of the senses which is needed to learn speech, mental development, emotional skills, and many other things. If not treated, children lack behind in school and they fail to develop language and thus get dependent on the society even for day-to-day activities.
References:
American Speech-Language-Hearing Association. "Congenital Hearing Loss." Accessed November 26, 2024. https://www.asha.org/public/hearing/congenital-hearing-loss/.
Stevenson, Jennifer, et al. "Parent-Initiated Assessment for Congenital Hearing Loss: A Population-Based Study." Pediatrics, vol. 139, no. 1, 2017, pages 138–144. Accessed November 26, 2024. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5222593/.
Schendel, D. E., et al. "Neurodevelopmental Effects of Early Hearing Loss in Congenital Conditions." Developmental Medicine & Child Neurology, vol. 59, no. 6, 2017, pages 587–595. Accessed November 26, 2024. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5675031/.
MSM
