Types of deafness^[4]

There are two types of deafness which are not mutually exclusive:

• 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, which may be congenital or acquired, can occur at any level along this part of the ear and include conditions such as excess earwax, trauma, otitis externa or media with effusion and otosclerosis.
• 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. There are also a number of congenital and acquired conditions resulting in sensorineural hearing loss but by far the most common is presbyacusis: age-related hearing loss which may also be associated with tinnitus (ringing, buzzing, whistling, hissing or other noise, heard in the ear in the absence of environmental noise).

Epidemiology^[5]

Deafness to some degree is a very common problem affecting more than 10 million people in the UK. Of these, 45,000 are children. About half of all deaf children are born deaf; about as many children again suffer from temporary deafness due to such conditions as glue ear.

The term 'deafened' is used to denote people who become profoundly deaf in adulthood. There are about 150,000 such individuals in the UK.

About 70% of the over 70 year-olds have some degree of hearing impairment. 71.1% of over 70 year-olds and 41.7% of over 50 year-olds have some form of hearing loss: age-related damage to the cochlea is the single biggest cause.

Between the ages of 40-80 years the incidence of deafness is higher in men than women; this is thought to be due to greater exposure to industrial noise. After that age, the situation is reversed as more women than men survive.

It is thought that higher levels of deafness exist in ethnic minority communities, particularly in immigrants who come from countries with poor healthcare, poor lifestyle and low levels of measles, mumps and rubella (MMR) immunisation.

Assessing the patient with hearing loss

History^[6]

This should be taken as for any other problem, taking care to explore possible systemic as well as local causes. Bear in mind that conductive hearing loss is more common in the under 40 age group and sensorineural hearing loss is more likely to occur in older patients.

• Specifically ask about otalgia (earache), otorrhoea (discharge), vertigo and tinnitus (more characteristic of noise-induced hearing loss, ototoxicity, presbyacusis and Ménière's disease).^[6]
• In the systemic review, enquire about diabetes and vasculopathy and ask about use of ototoxic medication.
• Ask about a family history of early hearing loss.
• Do not forget the social history which may reveal frequent visits to noisy environments (leisure or occupational).

Examination

Examination must be both anatomical and functional. Anatomical examination involves 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. Functional assessment can be carried out in several ways:

Whispered voice test^[8]

This is a simple test to detect hearing impairment in adults and most children (although it is possibly less accurate in the latter). It involves standing at an arm's length (0.6 m) behind the patient. The patient occludes the bad ear first (eg will put finger in ear canal or rub the tragus) and the examiner whispers a number-letter combination (eg 1-T-4) as quietly as possible.

This is best done if the examiner quietly exhales and then says the sequence. If the patient incorrectly hears the sequence, try again with another sequence.

They must get at least three numbers or letters out of the six possible correct ones to deem to have passed. The same procedure is carried out in the other ear with a different sequence.

In children aged under 12, 'spondee' words can be used (two-syllable words which have the same emphasis in each syllable, eg base-ball) and in children aged under 3, spondee words can be used in combination with picture cards to which they can point. However, the younger the child, the less reliable this test is and there is generally known to be some inter-examiner variation. Despite this, it is a useful simple screening tool.

Tuning fork tests^[6]

These valuable tests of auditory function enable a distinction to be made between conductive and sensorineural hearing loss. They are based on two principles:

• The inner ear is normally twice as sensitive to sound conducted by air than that conducted by bone.
• Where there is purely conductive hearing loss, the affected ear is subject to less environmental noise, making it more sensitive to bone-conducted sound.

Any abnormal tuning fork tests should be interpreted in the light of further audiometric tests.

Audiometric tests

These enable precise quantification of the degree of hearing loss and help to identify the site of pathology. Pure tone audiometry identifies pure tone thresholds for both air and bone conduction. A tympanogram looks at tympanic membrane compliance and is helpful in the diagnosis of perforation, middle-ear effusion, ossicular fixation or disruption. Auditory evoked potentials look at nerve impulses at many sites along the auditory pathway and are helpful in evaluating hearing problems; they may also be useful in monitoring pharmacological effects of a drug or even coma.

Problems associated with deafness^[9][10]

The physical issues

Hearing impairment may be a temporary side-effect of a transient problem such as infection (otitis; viral, eg maternal rubella, mumps, cytomegalovirus) but the sequelae of these may be long-term. Furthermore, there are a variety of syndromes underlying congenital deafness which themselves may be associated with a host of other physical problems: 30-40% of children with hearing problems have associated health needs. Thus, the patient with hearing loss needs a full examination at initial assessment and a comprehensive review of their problems at further follow-up.

The psychosocial issues

There is no doubt that hearing impairment can have a significant psychosocial impact on the individual. Children's language acquisition and cognitive development can be severely affected (if mild, hearing impairment may present itself as behavioural, cognitive or educational problems) and, in adults, it can affect work prospects and normal integration into society - the elderly being particularly vulnerable.^[8] It is therefore important, on confirmation of the diagnosis, to explore explicitly how the patient is experiencing this psychologically with enquiries into symptoms of depression, as well as what support network is available to the patient. There are a very large number of support groups (see 'Internet and further reading', below) but beware of the Internet-illiterate patient who may not know how to access local help.

Overview of management options

General points^[10]

Referral through to treatment times has improved significantly in recent years and technology has advanced significantly. However, evidence gathered by Action for Hearing Loss suggests that people wait ten years or more before seeking help and that GPs fail to refer up to 45% of people who present with hearing loss.

The Medical Research Council has estimated that by 2036 there will be more than 13 million deaf and hard of hearing people in the UK. A concerted public health strategy will be required to ensure that the physical, psychological and social needs of people with this disability will be accommodated.

Research suggests that using hearing aids early in the onset of deafness produces a better long-term outcome because the longer the brain is deprived of sound stimulation, the harder it will find it to re-learn sounds when generated by an aid.^[11]

Externally worn hearing aids^[12]

These come in a variety of shapes and sizes and many are available on the NHS. They are devices that increase the volume of the sound reaching the ear (effectively, amplifiers). They sit either behind the ear (although these devices are not powerful enough for patients with severe impairment) or just inside. Hearing aids that are placed right inside the external auditory meatus are available for patients with mild hearing loss. Bone conduction hearing aids for patients with conductive hearing loss are available in the form of headbands. Furthermore, hearing aids may be analogue or digital. Analogue hearing aids are slowly being phased out as they are superseded by improving digital aids. The latter are sometimes known as digital signal processing (DSP) hearing aids, or 'DSP aids'. Aids available on the NHS usually have a digital component to them. Digital aids process sounds in a different way to analogue aids but neither is totally successful in cutting out extraneous noise.

Implantable hearing aids^[13]

• Cochlear implants consist of a microphone and sound processor which are worn behind the ear and are connected to a transmitter coil, worn on the side of the head. Data from the coil are passed to a receiver-stimulator package implanted into a surgically fashioned depression in the mastoid bone. Electrical pulses are then delivered to an array of electrodes designed to stimulate the cells of the auditory spiral ganglion to provide a sense of hearing to those with neurosensory hearing loss.
• The National Institute for Health and Clinical Excellence (NICE) recommends unilateral cochlear implantation for people with severe to profound deafness (defined as hearing only sounds that are louder than 90 dB HL at frequencies of 2 and 4 kHz without acoustic hearing aids) come into the following categories:
  • Adults who fail to achieve a score of 50% or greater on Bamford-Kowal-Bench (BKB) sentence testing (a method of assessing hearing by repeating a spoken sentence)^[14] at a sound intensity of 70 dB sound pressure level (SPL) (dB SPL).
  • Children who fail to achieve speech, language and listening skills appropriate to age, developmental stage and cognitive ability.
• A 3-month trial of auditory hearing aids should be conducted prior to considering an implant.
• For patients who qualify for implants, simultaneous bilateral devices may be considered for adults or children who are blind or have other disabilities which increase their reliance on auditory stimuli as a primary sensory mechanism for spatial awareness.
• Sequential implant fitting is not recommended, except for some patients who already have a unilateral implant and would have benefited from bilateral implants under the new NICE guidance.
• Bone-anchored hearing aids are reserved for patients with conductive and mixed hearing loss. Surgery involves the fixing of a titanium implant just behind the ear, to which is connected an external abutment and a sound processor. Thus, it allows sound to be conducted through the bone rather than through the middle ear ('direct bone conduction').^[15]

Adjunctive management

Support groups - there is a significant and active deaf patient support network which patients should be encouraged to contact. Some have an emphasis on practical support, others on emotional support and others still on communicating to deaf people the advances in research. A selection of patient support websites is provided in 'Internet and further reading', below. Action on Hearing Loss (formerly known as The Royal National Institute for Deaf People (RNID)) is a particularly valuable source of a very broad range of information for patients and healthcare professionals alike.

Additional hearing aids - there are a variety of products on the market to assist with hearing. These range from hearing loops to vibrating pagers, visual trigger units for different situations (baby monitors, doorbells, fire alarms) and specialist alarm clocks and telephones, of which Typetalk and TextDirect are examples (see Internet and further reading, below). There is also a small but growing community of users of hearing dogs.

Social considerations - children with limited hearing impairment may manage perfectly well in mainstream schools with appropriate help and support but there are specialised schools for deaf children (listed in the National Deaf Children's Society (NDCS) website - see under 'Internet and further reading', below). There are also employer legal requirements with regard to hearing-impaired people in the workplace. Again, these are outlined in the NDCS website with links to further information about patient rights.

Deafness in the consultation^[16]

Patients with hearing impairment are commonly met in the consultation room, often for unrelated problems. This can sometimes lead to discomfort (at best) and a breakdown in communication (at worst) between the patient and the healthcare professional. There are some simple steps that can be taken in order to minimise these problems and make the consultation as useful as possible for all concerned:

• Ask the patient how they prefer to communicate: don't assume that the patient wearing a hearing aid can automatically follow what you are saying. Ask if they prefer to lip-read and have pen and paper handy.
• Sit in good lighting and, if possible, away from noise and distractors.
• Make sure you have the listener's attention before you start speaking.
• Do not turn your face away when speaking.
• Speak clearly but not too slowly or using exaggerated mannerisms.
• If they do not understand what you have said, don't just repeat it but try saying it in a different way.
• Don't waffle, avoid jargon and abbreviations.
• Check that the person is following what you are saying.
• In the long term, it is worth investing in a portable hearing loop which can be used in the consulting room.
• If the patient can use British Sign Language (BSL), consider using a suitably trained interpreter or "Sign Translate" via a computer live webcam.^[17]

See separate article Dealing with Hearing-impaired Patients for more details.