Ears

Ears

Deafness and the ageing ear

Deafness is a common, debilitating complaint that increases with age. 6% of adults, 33% of retired people and 80% of octogenarians in the UK have impaired hearing. Deafness is often ignored (‘part of getting older’) yet it prevents communication, causes social isolation, anxiety, depression, and can contribute to functional decline.

Around half of sufferers could be helped by a hearing aid, yet less than a quarter have one. Generally patients with unilateral, mild bilateral, or profound bilateral deafness do not benefit from conventional hearing aids.

▶Be alert to hearing loss. A quick assessment directs appropriate referral to audiology or ENT when necessary.

Normal ageing

Presbyacusis

Describes the decline in hearing that commonly occurs with age— ‘degenerative deafness’
Males > females
Usually detectable from age 60-65
Both the sensory peripheral (cochlea) and central (neural) components of the auditory system are affected with peripheral degeneration being accountable for at least 2/3 of the clinical features of presbyacusis
A variety of possible mechanisms exist—cellular degeneration gives rise to a reduction in the numbers of hair cells particularly at the basal end of the cochlea (the part responsible for high frequency sound appreciation). Circulatory changes such as atherosclerosis, microangiopathy, and atrophy of the stria vascularis contribute
The relative contributions of ‘normal ageing’ and cumulative exposure to noxious stimuli (noise, toxins, oxidative stresses, otological disease, poor diet, vascular disease) are unclear, but not all older people have hearing problems
The high frequencies are lost first—usually noticed when high-pitched female voices become hard to hear. As consonants are high frequency, the patient can often hear noise, but not understand, feeling that everyone is ‘mumbling’ (loss of discrimination)
‘Recruitment’ is a common problem, where the thresholds for hearing and discomfort are very close (‘Speak up … don’t shout’)
Busy, noisy environments make hearing harder, so patients may avoid social situations
There is no treatment to halt progression, but hearing aids may help

Other ear changes with age

These include:

Thinner walls to the external auditory canal, with fewer glands, making it dry and itchy
Drier wax due to decreased sweat gland activity, making accumulation (a cause of reversible hearing impairment) more common
Degenerative changes of the inner ear and vestibular system contributing to increase in deafness, vertigo, and tinnitus

Classifying deafness

Conductive

A disturbance in the mechanical attenuation of sound waves in outer/middle ear, preventing sound from reaching the inner ear.

It can be caused by outer ear obstruction (eg wax, foreign body, otitis externa), some types of tympanic membrane perforation, tympanosclerosis, or middle ear problems (effusion, otosclerosis, ossicular erosion secondary to infection or cholesteatoma)
It may be surgically correctable, and can be helped by a hearing aid

Sensorineural

A problem with the cochlea or auditory nerve so impulses are not transmitted to the auditory cortex.

Caused by genetic or perinatal factors in children
In adults may be traumatic, infective (viral, chronic otitis media, meningitis, syphilis), noise induced, degenerative (presbyacusis), ototoxic (eg aminoglycosides, cytotoxics), neoplastic (acoustic neuroma) or others such as Ménière’s disease
Usually irreversible
The appropriate hearing aid can be helpful
Cochlear implants can be considered in severe sensorineural deafness, but seem less effective than in younger patients, perhaps due to limitations in cerebral processing

Mixed

A combination of both conductive and sensorineural—probably the most common cause in older people.

HOW TO … Communicate with a deaf person

Ensure hearing aids are inserted correctly, turned on and have working batteries
Speak clearly and at a normal rate
Use sentences, not one word answers—this gives contextual cues to lip readers
Increase volume, but do not shout
Lower the pitch of the voice
Minimize background noise
Maximize face-to-face visual contact—look straight at the person, and ensure there are not bright lights behind you that will dazzle
Use visual cues when talking (eg hand gestures)
Be patient—repeat things if asked, changing the sentence slightly if possible
If confusion arises, write things down—do not give up

HOW TO … Assess hearing

General

Conversation will give an informal idea of hearing ability.

Clarify by performing free field speech tests by asking the patient to repeat words spoken in a whispered voice, conversation voice and shouted at 60cm from the ear. The non-test ear is masked by pressing the tragus backwards and rotating it with the index finger. Sit the patient next to you so that lip reading is not possible.

Examination

External ear and canal (looking for wax, inflammation, discharge, blood, abnormal growths, etc.)
Drum (perforations, myringitis, retraction, bulging of drum, etc.)
Tuning fork tests (with a 512kHz fork) may be helpful. Both are based on the principle of improved bone conduction perception with a conductive hearing loss
- Rinne’s—compares air and bone conduction. Hold tuning fork in front of ear then place on mastoid, to compare air and bone conduction. Air > bone is normal. Bone > air implies defective middle and outer ear function
- Weber’s—assesses bone conduction only. Hold tuning fork at vertex of the head and ask which ear hears the sound most loudly. With conductive deafness, it is heard loudest in the deafer ear; with sensorineural deafness it is heard most loudly in the normal ear

Who to refer?

Patients with sinister features should be referred to an ENT surgeon:

Recent or abrupt hearing loss
Unilateral hearing loss or tinnitus
Variable hearing loss
Ear pain

▶Sudden onset sensorineural deafness is an ENT emergency, and requires urgent referral (causes include infection, vascular event, tumour, leaking canals, etc.)

ALL other patients with suspected hearing loss should be referred routinely to an audiologist for further assessment and management.

Audiology

The majority of patients with hearing impairment are managed by audiologists and hearing therapists. They do the following.

Specialized hearing tests

Audiometry—quantifies the degree and pattern of loss. May be ‘pure tone’ (using signals at varying frequencies and intensities) or ‘speech’ (discriminating spoken words at differing intensities). The hearing thresholds are charted on an audiogram and interpreted by the audiologist (indicates conduction or sensorineural deafness, which frequency and which ear)
Impedance tympanometry—indirectly measures the compliance of the middle ear, identifying infection and effusion in the middle ear and eustachian tube dysfunction
Evoked response audiometry—measures action potentials produced by sound. No conscious response is required by the patient and so tests are less open to bias. (Before MRI, this was the main diagnostic test for acoustic neuromas)

Recommend and fit hearing aids

Many types. Help patients to have realistic expectations about their hearing aids (rarely a ‘miracle cure’) and train them how to use them optimally (eg minimizing background noise). Programme digital hearing aids.

Offer practical advice

About assistive listening devices such as:

Alternative signals—buzzers and flashing lights instead of doorbell or telephone ring; vibrating devices that attach to the wrist and alert the wearer to environmental noises. Hearing dogs can also be used
Television—subtitles, or devices that connect to the hearing aid allowing the television signal to be amplified
Telephones—with high/low volume control and ‘T’ settings that amplify the telephone noise without the background noise
Transmitter and receiver devices (infrared or FM radio wave) for use in theatres, etc. with transmission from the sound source. The listener can adjust the volume in their receiver
Advise about better communication

Run aural rehabilitation programmes—age-matched group sessions that help with adjustment to the sudden reintroduction of noise with a hearing aid (after what is usually a gradual hearing loss), teach skills (eg blocking out background noise, lip reading) and share practical tips (eg eating in a booth at a restaurant to limit background noise).

Other

Train people to lip read
Help manage tinnitus
Counsel about psychosocial implications of hearing impairment

Hearing aids

The past decade has seen many advances in hearing aid technology and performance. Modern hearing aids offer improved fidelity, greater amplification, and frequency-specific amplification. Patients who have tried hearing aids in the past and not found them beneficial should be encouraged to try them again.

What do hearing aids do?

Generally consist of a microphone that gathers sound, an amplifier that increases the volume and a receiver that transmits amplified sound. Most hearing aids also include circuitry that filters and processes sound prior to amplification.

Whom do they help?

Help many to some degree, but not all
Does not restore normal hearing—the wearer needs to learn to interpret the new auditory input efficiently
Conductive hearing loss is helped more than sensorineural loss

What are the different types?

Different sizes

Smaller units (eg completely-in-the-canal devices) are cosmetically more appealing and give good reception for mild—moderate hearing loss, but are fiddly and expensive
Medium-sized units (eg in-the-ear devices) are more visible, and have more feedback, but can be used for worse hearing loss
Larger units (eg behind-the-ear) provide the most amplification and are easier to handle, but suffer from feedback if the ear mould deforms

Monaural versus binaural—binaural hearing aids yield a subjective improvement in sound clarity, but monaural may be considered for unilateral loss.

Analogue devices

Cheapest, with least processing of sound
Set to hearing loss at the time of fitting
Audiologist adjusts amplification and tonality settings at time of fitting, but these are then fixed
Patient can adjust the volume manually (turn the device volume up when the noise is quiet, and down when it is loud)

Digitally programmable devices

More expensive, with moderate sound processing
Analogue circuit that can be adjusted at the time of fitting by a computer programme to best fit the patient’s needs
Automatic volume control

Digital devices

Most health authorities have projects underway to fit digital hearing aids for all new referrals and exchange old analogue aids. All but the most expensive are funded by the NHS where clinically indicated, and it is likely that a suitable device will be provided for most
Most expensive, most advanced, with the highest amount of sound processing
Programmable with flexible digital circuits that manipulate each sound according to pitch and volume to give the clearest sound for that individual
Higher clarity of sound, less circuit noise, faster processing, and automatic volume control

Disposable devices