See related separate article Deafness in Children.
The normal lower limit of the hearing range is 0-20 decibels (dB), where 0 dB is the threshold for the perception of sound at a given frequency for people with normal hearing. Deafness is a partial or complete loss of hearing, also known as hearing impairment. Hearing loss is measured in decibels hearing loss (dB HL). It can be graded as follows:
- 20-40 dB HL: mild, cannot hear whispers.
- 41-70 dB HL: moderate, cannot hear conversational speech.
- 71-95 dB HL: severe, cannot hear shouting.
- >95 dB HL: profound, cannot hear sounds that would be painful to listen to for a hearing person.
There are two types of deafness and patients may present with one or both of these:
- Conductive hearing loss - this occurs when there is a problem in the transmission of sound waves from the external ear, through the middle ear. The disease processes can occur at any level along this part of the ear.
- Sensorineural hearing loss - this refers to problems occurring in the cochlea (the most common site of disease), cochlear nerve or brain stem, resulting in abnormal or absent neurosensory impulses. Sensorineural problems are more common in adults.
There are more than 10 million people in the UK with some form of hearing loss. That is approximately one in six of the population. From the total figure, around 6.4 million are of retirement age and about 3.7 million are of working age.More than 800,000 of those with hearing loss are severely or profoundly deaf.
- Age-related damage to the cochlea is the single biggest cause of hearing loss. Numbers of people with hearing loss rise sharply from age 50 onwards.
- 71.1% of those aged over 70 and 41.7% of those aged over 50 have some form of hearing loss.
- There are 36,000 people aged 16-49 who are severely or profoundly deaf, and a total of around 1.15 million with any hearing loss in the same age group.
- Deafness occurs slightly more commonly in males than in females.
- Deafness may occur more commonly in immigrant populations from regions with greater levels of poverty, poor healthcare and low levels of immunisation against diseases such as rubella.
- The main risk factors for adult hearing impairment are age and excessive noise exposure.
- There are certain risk factors contributing to specific types of deafness (see 'Aetiology', below) such as previous ear infections, trauma, viral illness and so on.
There are many causes of congenital or childhood deafness that may persist into adulthood. Acquired causes are outlined below.
Conductive hearing loss
- Nature - occlusion may occur as a result of cerumen (notorious for getting impacted with the use of cotton-tipped buds), foreign body impaction (more often occurring in the young child and in patients with mental health problems), oedema (if severe, this may limit the action of the ossicles) or exostosis (benign bony growth in the external auditory canal, sometimes precipitated by frequent cold water swimming).
- Presentation - this may be a unilateral (eg, foreign body) or bilateral painless loss of hearing (unless there is impaction and associated infection of the foreign body) which is usually sudden as the canal finally occludes.
- Management - if there is no history of otitis media, tympanic perforation or inner ear surgery, cerumen can be safely irrigated out with body-temperature warm water; it may need to be softened first with several days' application of vegetable - particularly olive - oil. If you have a good view with the otoscope, it is possible to curette it out. If the patient is co-operative, non-impacted foreign bodies can be irrigated or removed in the same manner as for cerumen. If in doubt, refer to the ENT team. Oedema needs to have its underlying cause treated. Large exostoses can lead to impairment of normal cerumen migration - surgical removal is only indicated if they are symptomatic.
- Prognosis - this is good for these conditions and normal hearing should be restored in the absence of complications or underlying disease.
- Nature - there are different types of infection that concern the outer and middle ear but the principal conditions are otitis externa (most commonly caused by Pseudomonas aeruginosa and Staphylococcus aureus), otitis media (which can cause middle-ear effusions that decrease the mobility of the tympanic membrane and the ossicular chain) and, less commonly with regards to hearing loss, sinusitis which can cause a temporary hearing loss if there is associated swelling of the Eustachian tube.
- Presentation - otitis presents with a sudden painful loss of hearing. A narrow auditory canal with debris suggests otitis externa, and a normal lumen canal with a red, immobile tympanic membrane suggests otitis media.
- Management - this involves removal of any debris and application of local antibiotic drops (possibly applied to a wick which sits in the ear canal if there is severe otitis externa). Systemic antibiotics are only recommended in severe cases. Severe or recurring cases of otitis media may lead to middle-ear effusions. Refer patients with chronic otitis media (see referral criteria under 'Management', below).
- Prognosis - recovery is generally good but chronic otitis media may lead to middle-ear effusion or tympanic membrane perforation.
Tympanic membrane perforation
- Nature - this can arise as a result of chronic otitis, trauma (including barotrauma, water accidents, explosions, penetrating injuries or temporal bone fracture) and from surgery (eg, radical mastoidectomy).
- Presentation - the history may be suggestive, coupled with (usually) painful hearing loss and tympanic membrane perforation on examination of the ear.
- Management - small perforations (<2 mm) often heal spontaneously with topical antibiotic cover and instructions to keep the ear dry. If visibility is poor or there is suspicion of more extensive injury, refer to the ENT team.
- Prognosis - this depends on the extent of the perforation and causative factor. Recovery should be complete in the absence of complicating factors.
- Nature - benign cysts, benign and malignant tumours (fibromas, papillomas, adenomas, sarcomas, carcinomas and melanomas) and neurofibromatosis type 1 can all cause tumours within the ear canal. Obstruction of the ear canal may cause conductive hearing loss. (NB neurofibromatosis type 2 is associated with bilateral schwannomas (vestibular tumours) and therefore bilateral sensorineural hearing loss).
- Presentation - they tend to be associated with gradual, painless, unilateral hearing loss.
- Management - refer promptly for biopsy ± imaging. If a malignant tumour is confirmed, treatment will include invasive surgery ± radiation therapy.
- Prognosis - depending on the nature of the growth, this ranges from excellent (eg, benign papilloma) to very poor (eg, carcinoma of the bony ear canal).
- Cholesteatoma - this is a three-dimensional collection of epidermal and connective tissues within the middle ear. Patients characteristically present with chronic, suppurative otitis media and a progressive deafness. The tympanic membrane may be seen to be retracted or perforated with an epithelial lining to it. The cholesteatoma grows independently and can be locally invasive and destructive: if you suspect this, refer the patient for surgery.
- Adenoids - occasionally, rather than regressing (this usually occurs at about 5 years of age), these carry on growing, eventually to block off the Eustachian tube, so causing a painless, bilateral hearing loss in young adults. Refer for surgery.
- Otosclerosis (otospongiosis) - this occurs when there is abnormal bone deposition at the base of stapes so preventing normal ossicular vibration. Typical patients are middle-aged white women who present with painless, progressive, bilateral hearing loss and a positive family history of this condition. Many manage with hearing aids alone but some need to be referred on for surgery.
- Myringosclerosis - this is characterised by the deposition of irregular, white, calcium patches on the tympanic membrane. It is not generally problematic when isolated, but if it extends to cover associated structures (tympanic membrane, ossicular chain and middle-ear mucosa), ie tympanosclerosis, then significant hearing impairment can ensue. Refer for confirmation of diagnosis.
- Temporomandibular joint syndrome - patients suffer from pain in the jaw, face, and head, especially around the ears; clicking or popping in the jaw and ears; 'locking' of the jaws, and pain in opening the mouth. It may be associated with bilateral hearing loss, thought to be due to muscular spasms of the muscles of the inner ear. This is usually a self-limiting condition but a short course of non-steroidal anti-inflammatory drugs (NSAIDs) is sometimes helpful.
Sensorineural hearing loss
Presbyacusis (age-induced hearing loss)
See separate article on Presbyacusis.
Noise-induced hearing loss (NIHL)
- Nature - exposure to excessive sounds (acoustic trauma) produces a temporary shift in the stimulus threshold of the outer hair cells within the inner ear, so allowing them to recover. Sufficiently intense and repeated exposure results in a permanent threshold shift. Occupational hearing loss is the principal culprit but any noise, including military, social and firework noises, can all be implicated. High frequencies (typically 4 kHz) are the first to be affected, followed by progressively lower frequencies.
- Presentation - usually gradual hearing loss (unless exposure was to a sudden noise such as an explosion) associated with tinnitus in 60% of cases. The problem is bilateral ± symmetrical, and examination of the tympanic membrane is normal.
- Management - if hearing does not recover within a few days of sudden noise exposure, refer for audiometric testing. Patients complaining of occupational NIHL need referral, as there may be legal implications.
- Prognosis - if the exposure was moderate (such as at a loud pop concert), recovery may be complete. Prolonged or excessive exposure results in permanent damage. This is not progressive, however, and any further hearing loss after exposure ceases is not due to NIHL (it is often due to overlying presbyacusis).
Ototoxic hearing loss
- Nature - there are several classes of drugs that are known consistently to damage the inner ear. These include aminoglycosides, cis-platinum, salicylates, quinine and some loop diuretics. Macrolide antibiotics can cause hearing loss and glycopeptide antibiotics can also affect balance. More details of which drugs are ototoxic and their safe dosage levels can be found under 'Further reading & references', below.
- Presentation - tinnitus, hearing loss and balance problems may occur following administration of these drugs. The feeling of pressure within the ears is also a common complaint. The symptoms are often insidious and may occur weeks to months after use of these drugs.
- Management - avoid prescription of these drugs in pregnancy, consider lowest dose and check comorbidity (such as renal function) before prescribing. Symptoms are not reliable signs but, should they occur, review the drug regime, considering alternative doses and alternative drugs. If the offending agent has already been stopped, refer for audiometry; these patients may need some supportive measures such as fitting of a hearing aid.
- Prognosis - these patients are often left with long-term hearing impairments but in patients with associated balance disturbances, all but the most severe of cases improve due to central compensation (although the elderly may continue to be unsteady for the rest of their lives).
- Nature - this is being increasingly diagnosed in the context of autoimmune disease (where the diagnosis is confirmed by improvement with the administration of steroids) and in HIV where it may be associated with cytomegalovirus infection (see below).
- Presentation - autoimmune hearing loss presents with rapidly progressing, possibly fluctuating, bilateral hearing loss or attacks of hearing loss and tinnitus resembling Ménière's disease. About 50% of patients also complain of dizziness.
- Management - these patients respond to oral prednisolone. In some patients, low-dose methotrexate may be an alternative to long-term steroids.
- Prognosis - patients should fully recover between episodes but these are recurring.
See separate article on Acoustic Neuromas.
See separate article on Ménière's disease.
Idiopathic unilateral sudden sensorineural hearing loss
- Nature - this is a sudden sensorineural hearing loss of 30 dB within three days, which may be associated with tinnitus, vertigo and aural fullness. Its aetiology is not well known but it may be associated with viral infection or vascular insults.
- Presentation - hearing loss as above and there may be a history of upper respiratory tract infection in the previous month.
- Management - refer urgently. These patients are started on oral steroids within three weeks of onset; however, there is still a paucity of quantity and quality of evidence supporting this commonly used approach.
- Prognosis - best for those with minimal hearing loss, no vestibular symptoms and early treatment.
- Nature - this is an abnormal connection between the perilymphatic space of the inner ear and the middle ear cavity. It may be congenital or acquired (such as with barotrauma or straining - lifting, coughing, sneezing).
- Presentation - there is a sudden, unilateral hearing loss associated with vertigo and tinnitus. The history may be suggestive.
- Management - three to six weeks of bed rest. If symptoms do not improve, surgery may be recommended.
- Prognosis - this is variable, depending on the cause and size of the leak.
- Inflammation ± infection (such as encephalitis, meningitis, labyrinthitis, scarlet fever, typhoid, varicella zoster, otitis interna).
- Trauma (temporal bone fractures).
- Auditory neuritis.
- Multiple sclerosis.
- Muscular dystrophies.
- Paget's disease of bone.
- Charcot-Marie-Tooth disease.
Functional hearing loss
- Nature - this is deafness that results from psychological or emotional factors, rather than from physical causes. Diagnosis is sometimes complicated by the presence of a real physical hearing loss, either 'overlaid' by the functional loss or in one ear while the other ear has the functional loss (unilateral functional deafness).
- Presentation - this may be in many forms. Look for inconsistencies in responses to tuning fork tests. A quiet question in history taking whilst turning away or moving round the back of the patient may reveal a better hearing than described.
- Management - ultimately, diagnosis can only be confirmed on formal audiometric testing. These patients need to be managed sensitively. An emphasis on how very difficult emotional difficulties can result in very real impressions of hearing loss is helpful.
- Prognosis - this depends on the outcome of the underlying psychological problems.
Presentation may be with sudden or gradual, unilateral or bilateral hearing loss, depending on the aetiology. A history should be taken as with any other problem.
Questions to assess whether there is a hearing problem
- Do you have any difficulty with your hearing?
- Do you find it very difficult to follow a conversation if there is background noise (eg, TV)?
- How well do you hear someone talking when that person is sitting on your RIGHT SIDE in a quiet room?
- With no difficulty
- With slight difficulty
- With moderate difficulty
- With great difficulty
- Cannot hear at all
- How well do you hear someone talking when that person is sitting on your LEFT SIDE in a quiet room?
- With no difficulty
- With slight difficulty
- With moderate difficulty
- With great difficulty
- Cannot hear at all
If the answer to Q1 or Q2 is yes and the response to Q3 and Q4 is at least slight, then hearing aids would give benefit and would be more likely to be used.
Questions to assess what the problem might be
- Onset (when, progressive or sudden) and progression since.
- Unilateral or bilateral.
- Presence or absence of otalgia (earache), otorrhoea (discharge), vertigo and tinnitus.
- Past history of ear infections, ear injury, or straining to hear.
- Past medical history of stroke, diabetes, or heart disease.
- Current medication (see 'Further reading & references', below, for a complete list of ototoxic drugs).
- Previous need for intravenous antibiotics, diuretics, salicylates, or chemotherapy.
- Exposure to noisy environments (at work or in leisure time).
- Social history to rule out the need to contact professional governing bodies with regards to their impairment (such as pilots following an episode of Ménière's disease).
This should include inspection of the external ear (note minor disfigurements, as the development of the different components of the canal is closely related), and examination of the tympanic membrane, looking for obstructions (cerumen, foreign bodies), evidence of infection, perforation, tympanosclerosis, cholesteatoma or effusion.
The whispered voice test and tuning fork tests (Rinne's and Weber's tests) can be carried out simply and effectively but, ultimately, if these reveal hearing impairments, patients need to be referred on for audiometric testing which will enable precise quantification of the degree of hearing loss and help identify the site of pathology.
The separate article Hearing Tests may also be of use.
See also the separate article on Dealing with Hearing-impaired Patients.
- In patients aged 50-80 years (70% of first-time referrals) - in the absence of pathology, refer for an 'assess and fit' (for a hearing aid) appointment:
- The assess and fit appointment may either be a one-stop appointment where a universal hearing aid is offered, or a two-stop process where the first visit is to create an ear mould and provide information and the next is to fit the aid.
- Existing patients may also be referred to upgrade their hearing aid.
- Depending on local practices, there may be a telephone follow-up.
- Visually impaired/problems with dexterity or communication/older age group - refer for a primary assessment with audiology service (unless you think that they will manage with a simple assess and fit).
- Slight difficulty in one ear and/or unwillingness to have an aid - watchful waiting with counselling and information.
- Tinnitus that lasts for more than five minutes and doesn't simply occur after loud sounds - refer for primary assessment with the audiology services.
- Other problems reported and/or aged under 50 years - refer to the medical consultant-led ENT/audio-vestibular medicine outpatient service.
- Sudden hearing loss - refer to the emergency ENT/audio-vestibular medicine outpatient service.
Other patients you may wish to consider for referral include:
- Patients presenting with asymmetric sensorineural hearing loss.
- Patients with recurrent acute otitis media (more than three episodes in six months or four episodes in one year), chronic middle-ear effusions (more than three months in duration), or significant hearing impairment (greater than 30 dB along with an effusion) should be referred to consider the possibility of surgical drainage using myringotomy tubes.
- Tympanic membrane perforations that are >2 mm, where a full view of the problem is not possible, where associated injury is suspected or in patients where the perforation or hearing loss lasts more than two months.
- Suspicion of a tumour either in the external auditory canal or more central tumours such as an acoustic neuroma.
This depends on the aetiology of the disease process. Underlying treatable causes should be addressed but patients who go on to develop a long-term hearing problem have several options open to them:
- Externally worn hearing aids - these are amplifiers that come in a variety of shapes and sizes and are available on the NHS. They may be analogue or (more commonly these days) digital.
- Implantable hearing aids - cochlear implants, bone-anchored hearing aids and auditory brainstem implants are available to different, well-defined patient groups.
- Additional hearing aids - these range from hearing loops to vibrating pagers, visual trigger units, specialist alarm clocks and telephones, of which Typetalk and Textdirect are examples (see 'Further reading & references', below).
- Support groups - there is a significant and active deaf patient support network which patients should be encouraged to contact.
Where there is no known treatment to restore hearing, efforts should be concentrated on maximising what hearing there is left and limiting the psychosocial impact, through access to patient support groups (of which there are many - some listed below in 'Further reading & references') where there is a wealth of information available on social network, practical support tips and information about patient rights.
The general complications of deafness may be physical or psychosocial.
This depends on the aetiology as outlined above.
This depends on the underlying cause:
- Noise trauma is the most common, preventable cause of sensorineural hearing loss.
- Avoidance of other causes when possible - eg, ototoxic medications.
- Early and effective treatment of other causes - eg, meningitis.
- Screening (particularly of the elderly population) has been advocated in order to optimise early intervention and minimise the consequences of hearing loss, but there is currently little evidence for any overall benefit of screening.
Further reading and references
Types and Causes of Hearing Loss; Action on Hearing Loss
Facts and figures on hearing loss and tinnitus; Action on Hearing Loss
Isaacson J and Vora N; American Family Physician Review: Differential Diagnosis and Treatment of Hearing Loss Am Fam Phys 2003 Sep 15
Otitis media with effusion; NICE CKS, March 2011 (UK access only)
Wei BP, Stathopoulos D, O'Leary S; Steroids for idiopathic sudden sensorineural hearing loss. Cochrane Database Syst Rev. 2013 Jul 27:CD003998. doi: 10.1002/14651858.CD003998.pub3.
Schreiber BE, Agrup C, Haskard DO, et al; Sudden sensorineural hearing loss. Lancet. 2010 Apr 3375(9721):1203-11.
Edmiston R, Mitchell C; Hearing loss in adults. BMJ. 2013 Apr 25346:f2496. doi: 10.1136/bmj.f2496.
Hearing aids and how to get one; ENT UK
Hearing impairment - cochlear implants; NICE Technology Appraisal Guidance, January 2009
Chou R, Dana T, Bougatsos C, et al; Screening for Hearing Loss in Adults Ages 50 Years and Older: A Review of the Evidence for the U.S. Preventive Services Task Force. Agency for Health Care Research and Quality (US) 2011 Mar. Report No.: 11-05153-EF-1.
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