Hearing loss

Hearing loss is a reduction in the ability to detect or understand sound, measured by audiometry. Most cases are age related or noise related sensorineural loss or wax and middle ear effusion.

Clinical relevance. Untreated loss reduces communication and is associated with social isolation, depression and cognitive decline. In children, early loss damages speech and language development, and identification before 3 months with intervention by 6 months gives the best outcomes. Loss developing within 72 hours or less is an emergency: arrange same day audiometry and specialist review, with oral prednisolone 1 mg/kg (maximum 60 mg) each morning started at once when sensorineural loss is confirmed.

Anatomy and physiology. The outer and middle ear conduct sound to the cochlea; the cochlea transduces it; the cochlear nerve, brainstem and auditory cortex process it. Loss at each level has a characteristic pattern.

Classification.

• Conductive: outer or middle ear disease, with a reduced air conduction threshold and a normal bone conduction threshold (air bone gap of 15 dB or more).
• Sensorineural: cochlear or neural, with equal reduction in air and bone conduction.
• Mixed: both.
• Central and functional (non-organic).
• By degree, using the better ear average of thresholds at 500, 1,000, 2,000 and 4,000 Hz: normal under 20 dB, mild 20 to 34 dB, moderate 35 to 49 dB, moderately severe 50 to 64 dB, severe 65 to 79 dB, profound 80 to 94 dB, complete 95 dB or more.
• By onset: congenital, progressive, fluctuating, sudden.

Key distinctions. Rinne negative with Weber to the affected ear means conductive loss. Rinne positive with Weber to the better ear means sensorineural loss in the affected ear. Asymmetric sensorineural loss needs retrocochlear exclusion.

History. Onset and speed, laterality, fluctuation, progression, hearing in noise and on the telephone, tinnitus, vertigo, aural fullness, otalgia, otorrhoea, facial weakness, headache and neurological symptoms. Noise exposure (occupation, firearms, music, headphones), head injury, barotrauma, ear surgery, swimming, previous infection (meningitis, mumps, measles, syphilis, HIV), family history, cognitive complaints, and effect on work and social life.

Children. Pregnancy infections (cytomegalovirus, rubella, toxoplasmosis, syphilis), prematurity, neonatal jaundice requiring exchange, neonatal intensive care and ventilation, ototoxic drugs, meningitis, craniofacial anomalies, delayed speech or language, poor school performance, inattention, and failed newborn screening.

Drug history. Aminoglycosides, loop diuretics, platinum agents, salicylates (high dose), quinine, macrolides, vancomycin, phosphodiesterase inhibitors and ototoxic topical drops with a perforation.

Examination.

• Pinna and periauricular area, canal (wax, foreign body, swelling, exostoses, discharge) and tympanic membrane (perforation, retraction, effusion, cholesteatoma, tympanosclerosis, mass).
• Tuning fork tests at 512 Hz (Rinne and Weber), whispered voice test, and facial nerve and other cranial nerves.
• Nasopharynx and oropharynx (palate, adenoids in children), neck, cervical nodes, and parotid.
• Eyes and skin for features of syndromes (blue sclera, pigmentary change, branchial pits, pre-auricular tags).
• Gait, nystagmus and head impulse test when vestibular symptoms exist.

Red flags

• Sudden loss over 72 hours or less
• Asymmetric or unilateral progressive sensorineural loss
• Vertigo, facial weakness, other cranial nerve signs, or papilloedema
• Otalgia with discharge, mastoid swelling or fever
• Painless chronic otorrhoea with granulation or foul discharge
• Head injury or temporal bone trauma
• Hearing loss in a child who failed newborn screening, has speech delay or has had meningitis
• Systemic disease features (rash, sinus disease, arthritis, red eyes)
• Pulsatile tinnitus with loss

Special groups. Pregnancy: otosclerosis can progress; treat cause as for others. Older adults: presbycusis, wax and cognitive screening. Children: otitis media with effusion is the commonest cause and glue ear can persist for months. Region specific: chronic suppurative otitis media, mumps, measles, meningitis, congenital rubella and syphilis, and ototoxic drug exposure (aminoglycosides and quinine) are common.

Conductive

• Outer ear: cerumen, foreign body, otitis externa, canal exostoses and osteoma, atresia, tumour of the canal
• Middle ear: otitis media with effusion, acute otitis media, chronic suppurative otitis media, tympanic perforation, cholesteatoma, tympanosclerosis, ossicular discontinuity (trauma, erosion)
• Otosclerosis
• Eustachian tube dysfunction, barotrauma, nasopharyngeal carcinoma causing effusion, adenoidal hypertrophy
• Glomus tympanicum, Paget disease, Langerhans cell histiocytosis, granulomatosis with polyangiitis, tuberculous otitis media

Sensorineural, cochlear

• Presbycusis, noise induced hearing loss
• Ototoxicity (aminoglycosides, loop diuretics, platinum agents, salicylates, quinine)
• Meniere disease
• Genetic and syndromic loss (connexin 26 or GJB2, Pendred, Usher, Alport, Waardenburg, branchio-oto-renal)
• Congenital infection (cytomegalovirus, rubella, toxoplasmosis, syphilis), acquired infection (meningitis, mumps, measles, labyrinthitis, HIV, Lyme disease, syphilis)
• Autoimmune inner ear disease, Cogan syndrome, vasculitis, systemic lupus erythematosus
• Temporal bone fracture, perilymph fistula, barotrauma
• Large vestibular aqueduct
• Diabetes, chronic kidney disease, hypothyroidism, vascular disease, leukaemia, sickle cell disease
• Sudden sensorineural hearing loss

Retrocochlear and central

• Vestibular schwannoma, meningioma, other cerebellopontine angle lesions
• Multiple sclerosis, brainstem stroke
• Auditory neuropathy spectrum disorder
• Neurosyphilis, cryptococcal and other chronic meningitis

Other

• Functional (non-organic) hearing loss
• Auditory processing disorder
• Severe loss from head injury

Reasoning. Decide conductive or sensorineural from the tuning forks and otoscopy, confirm with audiometry, and then decide on tests for cause and imaging from the pattern.

First line. Otoscopy after wax removal, tuning forks, pure tone audiometry (air and bone conduction), tympanometry (type A normal; type B flat with effusion, or with a large canal volume in perforation; type C negative pressure in Eustachian tube dysfunction; shallow type As in otosclerosis; deep type Ad in ossicular discontinuity), speech audiometry and acoustic reflexes.

Imaging.

• MRI of the internal acoustic meatus and cerebellopontine angle with gadolinium: unilateral or asymmetric sensorineural loss (threshold difference of 15 dB or more at two or more adjacent frequencies, or poor speech discrimination), progressive unilateral loss, associated vertigo or other neurological signs.
• High resolution CT temporal bone: conductive loss with a normal tympanic membrane (otosclerosis, ossicular discontinuity, dehiscence), suspected cholesteatoma, trauma, chronic suppurative otitis media with complications, congenital malformation, and cochlear implant assessment. MRI with diffusion weighted sequences for cholesteatoma and intracranial complications.
• MRI brain for central causes and demyelination.

Blood and other tests. Glucose or HbA1c, full blood count, thyroid stimulating hormone, lipids, treponemal serology, HIV, urea and creatinine. Add ESR, antinuclear antibody, ANCA and complement for rapidly progressive loss when autoimmune or vasculitic disease is suspected, Lyme serology in endemic areas, and urine for protein and blood in suspected Alport syndrome. Genetic testing for congenital or familial loss after counselling.

In children: otoacoustic emissions, auditory brainstem response, behavioural audiometry by age, cytomegalovirus PCR on dried blood spot or urine within 3 weeks of birth, and ophthalmology, ECG (long QT in Jervell and Lange-Nielsen syndrome) and renal tests as needed.

Limitations. Tuning forks miss mild loss and do not replace audiometry. Tympanometry is unreliable in infants under 6 months. A normal MRI does not exclude a very small intracanalicular lesion. Many genetic panels leave a large fraction of congenital loss unexplained.

Urgent causes. Sudden sensorineural loss: prednisolone 1 mg/kg orally each morning (maximum 60 mg) for 7 to 14 days started within 72 hours, with same day ENT review (monitor glucose in diabetes and give gastric protection). Bacterial meningitis with loss: ceftriaxone 2 g IV every 12 hours with dexamethasone 10 mg IV every 6 hours for 4 days, first dose before or with the antibiotic, and early audiology. Malignant otitis externa and mastoiditis: admission with IV antibiotics and ENT surgical review.

Treat the cause

• Cerumen impaction: sodium bicarbonate 5 percent ear drops or olive oil 3 to 4 drops two or three times daily for 5 to 7 days, then microsuction or irrigation. Avoid irrigation with a perforation, grommet or previous ear surgery.
• Otitis media with effusion: watchful waiting for 3 months in children and adults with audiometry, then grommet insertion for persistent effusion with hearing loss of 25 to 30 dB or more or developmental effects. In adults with unilateral effusion examine the nasopharynx to exclude carcinoma.
• Acute otitis media: analgesia first, then antibiotics when indicated: amoxicillin 500 mg orally three times daily for 5 to 7 days in adults (maximum 3 g daily), or children 40 to 90 mg/kg daily in 2 or 3 divided doses (maximum 3 g daily) for 5 days or 10 days when under 2 years or severe; penicillin allergy: clarithromycin 500 mg orally twice daily for 5 days in adults (halve when creatinine clearance is under 30 mL/min), or children 7.5 mg/kg twice daily (maximum 500 mg a dose).
• Chronic suppurative otitis media and cholesteatoma: aural toilet, topical ciprofloxacin 0.3 percent ear drops 4 drops twice daily for 7 to 14 days (no aminoglycoside drops with a perforation), ENT referral for tympanoplasty and mastoid surgery.
• Otosclerosis: hearing aid or stapedotomy, with ENT referral.
• Ossicular discontinuity and perforation: tympanoplasty and ossiculoplasty.
• Autoimmune inner ear disease and vasculitis: prednisolone 1 mg/kg orally daily (maximum 60 mg) with specialist immunotherapy.
• Syphilis with ear involvement: benzylpenicillin 3 to 4 million units IV every 4 hours (18 to 24 million units daily) for 10 to 14 days, with prednisolone 1 mg/kg daily for the first days to limit the Jarisch Herxheimer reaction.
• Symptomatic congenital cytomegalovirus infection with hearing loss: valganciclovir 16 mg/kg orally twice daily for 6 months, started within the first month of life by a paediatric infectious disease team, with neutrophil count and liver function monitoring.
• Meniere disease and vestibular schwannoma: specialist care.
• Ototoxicity: stop the drug when possible, and monitor audiometry for patients on aminoglycosides, platinum agents or prolonged loop diuretic therapy.
• Hypothyroidism, diabetes, hyperlipidaemia and hypertension: usual control of the underlying disease.

Rehabilitation

• Hearing aids for mild to profound loss when it causes difficulty in daily life; fit early in children (within the first months of life).
• Bone anchored or implantable devices for conductive loss that cannot be corrected, canal atresia and single sided deafness.
• Cochlear implant for severe to profound bilateral sensorineural loss with limited benefit from hearing aids (children from 12 months, earlier after meningitis because of cochlear ossification).
• Assistive listening devices, speech reading, communication training, and tinnitus management when present.
• Noise protection and occupational hearing conservation.
• Audiology, speech and language therapy, and educational support for children.

Monitoring. Audiometry at 3 to 6 months for any new loss, annual audiometry for progressive or asymmetric loss under observation, MRI follow up for small schwannoma, hearing aid review, and cognitive and mood screening in older adults.

Referral and escalation. Same day: sudden loss, suspected stroke, meningitis, malignant otitis externa, mastoiditis, facial weakness with otorrhoea. Urgent ENT within 2 weeks: unilateral or asymmetric loss, suspected cholesteatoma, tumour, or retrocochlear disease. Audiology for all patients with persistent loss. Paediatric audiology and ENT for any child with suspected hearing loss. Genetics, neurology, nephrology and ophthalmology for syndromic loss.

Admission criteria. Sudden loss with neurological signs, bacterial meningitis, mastoiditis or intracranial complications, malignant otitis externa, or temporal bone fracture with CSF leak.

Discharge and safety netting. Review at 4 to 6 weeks. Return urgently for further sudden loss, vertigo, facial weakness, severe ear pain, discharge with fever, headache or neck stiffness.