Hearing Loss: Assessment and Management

Introduction

Hearing loss is extremely common, affecting around 1 in 6 adults in the UK and rising sharply with age, alongside a smaller but important group of children with congenital or early-onset loss.¹ It is broadly divided into conductive hearing loss, where sound fails to reach the inner ear efficiently, and sensorineural hearing loss, where the cochlea or auditory nerve itself is damaged; the two can also coexist as a mixed loss.

Getting the classification right at the bedside, using history and simple tuning fork tests, points directly to the likely cause and the urgency of referral - most conductive causes are benign and often treatable, while some patterns of sensorineural loss, particularly sudden or asymmetric loss, need urgent specialist assessment.

Classification and pathophysiology

Conductive hearing loss

Sound is normally transmitted through the external canal, across the tympanic membrane, and amplified through the ossicular chain to the oval window. Anything that obstructs the canal, stiffens or perforates the drum, or fixes or disrupts the ossicles causes a conductive loss, in which the cochlea and nerve are functioning normally but sound simply cannot reach them efficiently.²

Sensorineural hearing loss

This results from damage to the cochlear hair cells (sensory) or the auditory nerve and central pathways (neural). Hair cells do not regenerate in humans, which is why most sensorineural hearing loss is permanent. Causes range from cumulative age-related and noise-related damage to acute events such as vascular occlusion, viral cochleitis or a compressive lesion of the auditory nerve.²

Presbycusis is cumulative, age-related loss of outer hair cells, beginning at the high-frequency (basal) end of the cochlea and progressing towards lower frequencies, which is why older adults typically struggle first with consonants and speech clarity in noisy environments before losing awareness of pure volume. Noise-induced hearing loss damages outer hair cells in the region of the cochlea tuned to 3-6 kHz, producing the classic "noise notch" on audiometry, and is cumulative and dose-related, making it substantially preventable with hearing protection.

Otosclerosis

Otosclerosis deserves separate mention as an important cause of progressive conductive (and sometimes mixed) hearing loss in young adults. Abnormal bone remodelling fixes the stapes footplate within the oval window, preventing normal ossicular movement. It is inherited in an autosomal dominant pattern with variable penetrance, is twice as common in women, and classically worsens during pregnancy. The tympanic membrane is typically normal on otoscopy, occasionally with a pink hue from vascularity over the promontory (Schwartze sign), and the family history is often positive.²

Risk factors

• Increasing age (presbycusis)
• Cumulative or occupational noise exposure
• Family history of early-onset or progressive hearing loss
• Ototoxic medication exposure, particularly with renal impairment
• Recurrent otitis media or chronic ear disease
• Perinatal risk factors for congenital loss: prematurity, NICU admission, congenital infection (e.g. CMV), family history
• Cardiovascular risk factors, which are also implicated in sudden sensorineural hearing loss
• Head trauma

Clinical features and history

Key features to establish are the speed of onset (sudden versus gradual), whether the loss is unilateral or bilateral, and any associated symptoms such as tinnitus, aural fullness, otalgia, discharge, or vestibular symptoms (vertigo or imbalance).¹

• Sudden unilateral loss - think sudden sensorineural hearing loss or, if painful, a mechanical or infective cause
• Gradual bilateral loss in an older adult - presbycusis is most likely
• Fluctuating loss with tinnitus and vertigo - suggests Meniere's disease
• Progressive unilateral loss with tinnitus and unsteadiness - raises concern for a vestibular schwannoma
• Loss after starting a new medication - consider ototoxicity
• Occupational or recreational noise history - relevant to noise-induced loss and to compensation claims

In children, parental concern about a lack of response to sound, delayed speech and language development, or poor progress at school should always be taken seriously and prompt formal audiological assessment rather than reassurance alone.

Examination

Otoscopy first, to look for wax, canal disease, or a drum abnormality (perforation, retraction, effusion). If the canal and drum are normal, the loss is more likely sensorineural, although normal otoscopy does not exclude conductive pathology such as otosclerosis.

Rinne and Weber tuning fork tests (512 Hz) are quick bedside tools to classify the loss before formal audiometry:

Cranial nerve examination, including facial nerve function, and assessment for nystagmus complete the bedside assessment, particularly when a retrocochlear cause such as vestibular schwannoma is being considered.

Investigations

Pure tone audiometry is the gold standard investigation, plotting hearing thresholds across frequencies for air and bone conduction in each ear, and distinguishes conductive, sensorineural and mixed patterns objectively.¹ Tympanometry assesses middle ear compliance and supports the diagnosis of effusion or ossicular fixation.

MRI of the internal auditory meatus is indicated for any unilateral or significantly asymmetric sensorineural hearing loss, to exclude a vestibular schwannoma or other retrocochlear pathology.³ Blood tests (FBC, ESR/CRP, glucose, lipids, thyroid function) and autoimmune or infective screens are considered in sudden sensorineural loss or atypical presentations, and genetic testing has a role in congenital or early-onset sensorineural loss.

In neonates and infants, otoacoustic emissions (OAE) and automated auditory brainstem response (AABR) testing form the basis of the newborn hearing screening programme, since behavioural testing is not reliable at this age.

Congenital and paediatric hearing loss

Around 1-2 in 1,000 babies are born with permanent hearing loss, which is why the UK newborn hearing screening programme tests every baby, usually within the first few weeks of life. Early identification is important because untimely detection can delay speech, language and cognitive development at a critical window.¹

Roughly half of congenital sensorineural hearing loss is genetic, most commonly non-syndromic and inherited in an autosomal recessive pattern (mutations in the GJB2 gene, encoding connexin 26, are the single most common identifiable cause). Syndromic causes include Usher syndrome (with retinitis pigmentosa) and Pendred syndrome (with goitre). Non-genetic causes include congenital cytomegalovirus infection, prematurity and NICU admission, and perinatal hypoxia.¹

A child who passes newborn screening can still develop hearing loss later from causes such as recurrent otitis media with effusion, meningitis, or progressive genetic conditions, so ongoing parental and health visitor vigilance for speech and language delay remains important throughout early childhood.

Sudden sensorineural hearing loss

Sudden sensorineural hearing loss (SSNHL) is defined as a loss of at least 30 dB across 3 or more consecutive frequencies developing within 72 hours. Most cases are idiopathic, though proposed mechanisms include viral cochleitis, vascular occlusion of the labyrinthine artery, and autoimmune inner ear disease.⁴

It is an otological emergency because early treatment improves the chance of recovery. Any patient with sudden unilateral hearing loss needs same-day or next-working-day ENT assessment, audiometry to confirm the diagnosis, and MRI to exclude a vestibular schwannoma, which can occasionally present this way.

Management

Management follows the underlying cause. Ear wax is removed by irrigation, microsuction or manual instrumentation. Otitis media with effusion is managed as described separately, with active observation and grommets if persistent. Otosclerosis, a hereditary condition causing progressive fixation of the stapes footplate, is managed with hearing aids or stapedectomy/stapedotomy surgery.

For established sensorineural hearing loss, the mainstay of treatment is amplification with hearing aids, which are effective for mild to severe loss and are provided free through NHS audiology services. Bone-anchored hearing aids (BAHA) bypass a diseased or absent outer/middle ear by transmitting sound directly via bone conduction, and are useful in conductive or mixed loss where a conventional hearing aid is unsuitable, such as chronic discharging ears or aural atresia.

Cochlear implants are considered for severe to profound sensorineural hearing loss when hearing aids provide insufficient benefit, converting sound into electrical signals that directly stimulate the auditory nerve. They are used in both children (including early implantation for congenital deafness, to support speech and language development) and adults.

Complications

• Speech and language delay if congenital or early-onset loss is not identified and managed promptly
• Social isolation and an association with cognitive decline in older adults with untreated hearing loss
• Educational and occupational impact of unaddressed hearing loss
• Permanent loss if treatable causes (e.g. sudden sensorineural hearing loss) are not recognised and treated within the relevant window
• Tinnitus, which frequently accompanies both conductive and sensorineural hearing loss

Red flags

Prognosis

Conductive causes are frequently reversible - wax removal, resolution of an effusion, or repair of a perforation or ossicular chain often restores hearing close to normal. Otosclerosis responds well to surgery in appropriately selected patients.

Most sensorineural hearing loss, including presbycusis and noise-induced loss, is permanent because cochlear hair cells do not regenerate, but hearing aids and, where appropriate, cochlear implants provide substantial functional benefit. Sudden sensorineural hearing loss has a variable prognosis: roughly a third recover fully, a third partially, and a third have little or no recovery, with earlier treatment associated with better outcomes.⁴