We should be aware that hearing loss could be only a part of a symptom of a more sinister underlying health diagnosis
BY DR JOHNSON NG WEI SIANG
Hearing loss occurs when the ability to hear is impaired compared to someone with normal hearing. Humans can detect sounds from a range of frequency from 20Hz to 20kHz, while its loudness is measured in decibel (dB).
A normal hearing for each frequency is defined as having a hearing threshold of 25dB or better. Some level of hearing loss is said to occur below this threshold.
Hearing loss can be mild (26- 40dB), moderate (41dB-55dB), moderately severe (56-70dB), severe (71-90dB) and profound (>91dB). Deafness in an ear usually refers to at least a profound or total hearing loss.
Our ear is divided into three parts which are outer, middle and inner ear.
The outer and middle ear are responsible for conducting and amplifying the sound from the environment, while the inner ear is responsible for converting mechanical sound energy into electrical impulses to be sent for processing in the auditory cortex of the brain.
Hearing loss can occur when there is disruption in the conduction of sound due to the outer and middle ear problems, which results in Conductive type hearing loss. Pathology in the inner ear will result in a Sensorineural type hearing loss. A combination of both Conductive and Sensorineural type hearing loss is referred to as Mixed hearing loss.
The most common cause of Conductive hearing loss is impacted ear wax in the outer ear. Other common conditions that cause conductive hearing loss include:
Outer ear: otitis externa (swollen ear canal), foreign body or congenital causes such as ear canal atresia (failure of normal external ear development).
Middle ear: middle ear effusion/otitis media (fluid in the middle ear), ossicular dislocation from trauma and otosclerosis
For Sensorineural hearing loss, the most common cause is presbyacusis (degeneration from ageing). In adults, it can also happen from damage to the inner ear because of prolonged exposure to noise hazards which can be work-related, head injury or ototoxicity (drug-induced).
Sensorineural hearing loss can also occur in a child. In such cases, it could either be congenital (from birth) or developmental (after birth). Conditions that can cause Sensorineural hearing loss in a child include prematurity, certain syndromes with craniofacial anomalies, meningitis and hyperbilirubinaemia (jaundice).
The presentation of a person with hearing loss depends on age. A child with hearing loss may present with speech delay or other learning disabilities, while an adult may have difficulty communicating while also speaking inappropriately loud.
Having a hearing impairment is also shown to affect an individual’s self-confidence. This would lead to social withdrawal and depression. Tinnitus (ringing in the ear) is also a common symptom in patients with hearing loss.
While newborn hearing screening is commonly done before discharge, parents need to be always vigilant if they suspect hearing loss in their child. This is because speech-language development is crucial in the first two years of a child’s life.
The earlier it is recognised, the earlier intervention could be instituted, the better the chances of normal development for the child. This is mainly for a child with bilateral (both ear) deafness and may require a cochlear implant.
One should also be aware that hearing loss could be only a symptom of a more sinister underlying health diagnosis. A unilateral (one-sided) ear block sensation that does not resolve over a week warrants further assessment. It could also be an early symptom of NPC (nasopharyngeal carcinoma) due to the mass in the nasopharynx obstructing the Eustachian tube opening.
Sinusitis can also cause a similar hearing loss although it is usually transient, while underlying adenoid hypertrophy may cause a child with persistent middle ear effusion.
To diagnose hearing loss in an adult, a pure tone audiogram is commonly performed to assess the level and severity of the hearing loss. A BSER (Brainstem Evoked Response) to detect the brain wave activity to a given sound stimulus is preferred for a younger child.
Management of hearing loss depends on the cause. Clearing of impacted ear wax may resolve the hearing loss.
Middle ear effusion may be treated medically or if it persist surgically with myringotomy and grommet insertion. Hearing loss that lasts or of sensorineural type may require a hearing aid if the hearing loss is indeed impairing quality of life. Types of hearing aids depend on an individual’s level of hearing loss, preference and dexterity in handling the minor type hearing aid.
For a child with bilateral profound hearing loss, a cochlear implant early in a child’s speech-language development would be crucial for the best outcome.
Optimal management of hearing loss also aims to restore binaural hearing. Binaural hearing (hearing with both ears) has the advantage of localising the direction of a sound. Hence, a person with single-sided hearing loss may have difficulties determining the direction of sound and reduced sound clarity.
Non-medical treatment of hearing loss aims at prevention and slow its progress. Individuals should practice good ear care in avoiding prolonged exposure to loud noises, which can damage the inner ear’s hair cells.
Earplugs should be used if noise hazard in the work environment cannot be avoided. Consumption of certain vitamin supplements may also help slow the progression of nerve degeneration. — The Health
Dr Johnson Ng Wei Siang is Consultant ENT/Head & Neck Surgeon at Sri Kota Specialist Medical Centre, Klang.