Understanding Hearing Loss: An Interview with ENT Surgeon Dr. Gayathri (Part-1)

Dr. Gayathiri: Hi all! I am Dr.Gayathiri. I pursued my MBBS from Tirunelveli Government Medical College in 2007. I did my MS (ENT) from Government Stanley Medical College in 2016. I am currently working as a Consultant ENT surgeon in Virudhunagar.

Dr. Gayathiri: Hearing loss is a very common worldwide problem affecting all age groups and thus leads to marked disability. Hearing loss is of three main types namely

• Conductive hearing loss

• Sensorineural hearing loss

• Mixed hearing loss

Any disease process that interferes with the conduction of sound to reach the cochlea causes conductive hearing loss. Sensorineural hearing loss (SNHL) results from lesions of the cochlea, VIIIth nerve (vestibulocochlear nerve), or central auditory pathways. It may be present at birth (congenital) or start later in life (acquired).

Dr. Gayathiri: Most infants with a Permanent Congenital Hearing Impairment (PCHI) have an SNHL. About 70% of children with PCHI are non-syndromic and the remaining 30% have one of a large variety of syndromic conditions, such as Waardenburg syndrome, Usher syndrome, and Apert syndrome.

Children who have purely conductive hearing loss may have some congenital conditions such as ossicular abnormalities and bilateral aural atresia, congenital middle ear abnormalities. In children, especially during the first 5–6 years of life, acute otitis media (AOM) and middle ear effusions (glue ear) are common with a much greater prevalence. Infections causing hearing loss include congenital conditions such as rubella and cytomegalovirus (CMV) and acquired childhood infections such as mumps, measles, meningitis, and chronic otitis media.

In adults, common causes of hearing loss are impacted wax, chronic suppurative otitis media (CSOM), keratosis obturans, External auditory canal (EAC) cholesteatoma, malignant otitis externa, osteoma of EAC, exostosis of EAC, secretory otitis media, acute and chronic suppurative otitis media, otosclerosis, otitic barotrauma, Meniere’s disease, cochlear otosclerosis, noise-induced hearing loss, and ototoxicity. In the elderly, presbycusis Is the most common cause which is nothing but sensorineural hearing loss associated with physiological aging. It usually manifests at the age of 65 years but may do so early if there is a hereditary predisposition, chronic noise exposure, or generalized vascular disease.

Dr. Gayathiri: Hearing loss in a child may develop from courses before birth (prenatal), during birth (perinatal), or thereafter (post-natal).

1. Prenatal factors may pertain to the infant or the mother. An infant may be born with inner ear anomalies, such as Michel aplasia, Scheibe dysplasia, Mondini dysplasia, and semicircular canal malformations. Maternal factors such as infections during pregnancy, drugs during pregnancy, and radiation to the mother in the first trimester also play a role.

2. Perinatal factors include anoxia, prematurity & low birth weight, birth injuries, neonatal jaundice, neonatal meningitis, and sepsis.

3. Post-natal factors are categorized into genetic and non-genetic causes. In genetic causes, though deafness is genetic, it manifests later in life. Deafness may occur alone as in familial progressive sensorineural deafness or in association with certain syndromes e.g. Alport and Klippel feil syndrome.

Dr. Gayathiri: For all infants, regular surveillance of developmental milestones, auditory skills, parental concerns, and middle ear status should be performed. Hearing loss is suspected if the child sleeps through loud noises unperturbed, fails to startle to loud sounds, or fails to develop speech at 1–2 years. A partially hearing child may have defective speech and perform poorly in school and be labeled mentally retarded.

Risk factors for hearing loss in children are

• Family history of hearing loss

• Prenatal infections (TORCHES)

• Craniofacial anomalies including those of the pinna and ear canal

• Birth weight less than 1500 g

• Hyperbilirubinaemia requiring exchange transfusion

• Ototoxic medications

• Bacterial meningitis

• Apgar score of 0–4 at 1 min or 0–6 at 5 min

• Mechanical ventilation for 5 days or longer

• Stigmata or other findings associated with a syndrome known to include sensorineural and/or conductive hearing loss

It is essential that all children at risk for hearing loss should be screened early and followed.

Dr. Gayathiri: Communication is a two-way process, depending on the receptive and expressive skills. Reception of information is through visual, auditory, or tactile faculties while expression is through oral or written speech or manual sign language.

In the hearing impaired, auditory faculty is poor or absent. Thus, for proper communication, there is a need either to improve hearing through amplification of the residual hearing or cochlear implants; and in the absence of the feasibility of developing the auditory faculty, one has to develop visual or tactile means of communication.

Dr. Gayathiri: Sense of balance involves a delicate interplay between visual, auditory, and somatosensory receptors. Older adults with hearing loss may experience falls more often than those with normal hearing. This is because hearing loss disrupts this sensorimotor system, impairs processing time, and causes a slower reaction to external stimuli thus prevents from preparing our body for danger.

The vestibular system sends signals to the brain about head motion helping us to maintain our balance and stabilizing our gaze. The auditory system works in tandem by listening out for signs of threat so that our body can prepare to react appropriately. Hearing loss can also be caused by an underlying condition, such as neuritis of inner ear inflammation, which can impact the vestibular system and one’s sense of position.

Dr. Gayathiri: Interventions include digital hearing aids, implantable devices (cochlear implants, bone-conduction hearing implants on soft band for young children, middle ear implants), and assistive technologies such as FM systems and wireless technology.

Optimum initial management is with the early fitting of binaural hearing aids. If hearing aids are not appropriate early referral should be made for assessment of otological implants including cochlear implantation. The earlier that hearing aids or implantable devices are provided for a deaf child, the more effective they are known to be in the long term. The early intervention team is key to their acceptance and use daily.

For the family of a young deaf infant, adapting to the use of this technology can be challenging when coming to terms with the diagnosis and the implications of hearing loss. All children with PCHI should have a full history and clinical examination, with audiological testing appropriate to the child’s age. Families should be offered etiological investigations to include imaging, genetic testing, and other investigations, followed by appropriate management of associated conditions and skilled genetic counselling.

Dr. Gayathiri: As genetic causes are responsible for 50-60% of hearing loss, gene therapy, and genome editing are the possible emerging therapies for genetic causes of deafness, which involves replacing or supplementing a dysfunctional gene with normal or functional genes, Adenovirus Associated Virus (AAV) is one of the most widely used vector.

Dr. Gayathiri: While both hearing aids and cochlear implants are capable of providing great benefits, there are situations in which many users find them inadequate. The two problems are intrusive background noise and distance. Additional technology goes some way towards solving all of these difficulties.

Additional technology can broadly be divided into two categories: assistive listening devices (ALDs), which are designed to improve audibility, and alerting devices, which use visual or tactile signals as a substitute for sound. Collectively they are sometimes known as hearing assistance technology (HAT).

1. ASSISTIVE LISTENING DEVICES: Frequency modulation (FM) systems, induction loop systems, and personal amplifiers can improve sound clarity and reduce background noise for individuals with hearing loss. These devices can be particularly beneficial in educational settings or group environments.

   FM systems - They are particularly valuable in classrooms and lecture theatres, where the speaker tends to be at a distance from the listener and maybe moving about, and they are often used by hearing-impaired children at school.

   Infrared systems - Sound can be converted to an infrared signal which is then transmitted wirelessly to a receiver worn by the hearing aid user with a neck loop attached. This is another neat and convenient option for TV watching, but it has the disadvantage that the signal can easily be interrupted if the user moves around.

   Streamers - By giving access to Bluetooth, streamers can be used with compatible hearing aids as portable amplifiers with wireless microphones or plugged into personal music players. An additional adapter is needed for a streamer to be used as a TV listener.

2. ALERTING DEVICES: There are quite simple and inexpensive devices that can be used to alert people with hearing loss to telephone ringers, doorbells, alarm clocks, smoke alarms, and baby monitors, They produce an extra loud sound signal or relay the signal to an area closer to the individual. A “hearing dog” is one such simple device. The dog is trained to bark loudly at the sound of a doorbell or the cry of a baby to alert its master. It is a helpful companion for the hearing impaired.

   For people with severe to profound or total deafness, even these devices that produce extra loud sounds may not be useful. They need assistive signaling devices where the sound (as of doorbell, telephone, alarm clock, baby crying) is changed into a light signal or vibrations. Alarm clocks with flashing lights or those devices which produce strong vibrations to awaken the individual are also available