Hearing Loss

The Ageing Ear

In this article we will discuss the  predominant issues with the ageing ear.

Wax Impaction

Wax impaction is one of the most  frequent ear related presentations to the GP. Age related atrophy of the ceruminous  glands, anatomical changes as well as the use of cotton buds and the wearing of hearing aids all contribute to an impairment of the self cleaning mechanism of the canal. While a significant hearing loss is rare, even with severe impaction, it can be uncomfortable, predisopose to infections, contribute to hearing loss and interfere with the proper function of hearing aids.

Wax removal is arguably the most common ENT intervention by a GP. (4). The use of cerumenolytics and syringing of the ears remains a safe method, although not without complications and is not always successful. Once clear the regular use of olive oil or baby oil can help in minimising further impaction and treat itch. Not infrequently dermatitis can play a role, with topical mometasone lotion efficacious. In recalcitrant cases or with concurrent ear pathology, patients should be referred to an ENT surgeon for microscopic removal.

With age, the pinna and cartilaginous canal tend to prolapseforward creating anything from a mild to almost complete soft tissue stenosis. This exacerbates wax impaction and can prevent the proper fitting of hearing aids. When this is responsible for recurrent problems and frequent medical attendances a Z-plasty meatoplasty can be performed. This is very minor surgery and involves removal of a small piece of cartilage, significantly widening the external canal.

Hearing Loss

In a recent Australian study in those over 60 years of age,  21.7% reported a loss of hearing, with 14.6% reporting a hearing disability, encompassing a hearing loss and a communication disability and/or the use of hearing aid. (1)

 Obviously there are a long list of disease processes that must be considered when investigating hearing loss, with asymmetry and rapid progression key pointers to further investigation.

As a general rule any conductive loss should be referred to a specialist. Most importantly when there is more than 10dB difference in contiguous frequencies of neural hearing a vestibular schwannomas must be excluded. An MRI scan is the most sensitive investigation  in this setting. (5) A large percentage of these tumours, especially in the elderly, do not require active intervention, but need to be monitored on a regular basis. (6,7)

Age-related hearing loss (presbycusis) is the most common form of hearing loss, and the predominant neurodegenerative disease of ageing. It is generally slowly progressive, symmetric and irreversible, and in some has a genetic predisposition. (8)

 Noise induced hearing loss is related to the length of time exposed to loud noise, especially above 85dB. Worldwide, 16% of disabling hearing loss in adults is attributed to occupational noise. (9) Importantly, this is essentially a preventable problem, but there is good evidence to suggest some people are more prone to damage than others. (10). Due to the mechanics of the external ear, the pattern of hearing loss is often maximal at 4000Hz. Obviously, noise induced and age related hearing loss often co-exist, and when occupational  compensation is being considered, hearing loss attributed to noise is adjusted for age.

 

Management of Hearing Loss

Assistive listening devices

These are very important in hearing rehabilitation, and are usually an adjunct  to hearing aids. They include FM systems; amplified telephones; alerting signals (doorbells, vibrating alarm clocks, smoke detectors), SMS and email.

Hearing aids

Properly fitted and tuned hearing aids make a significant improvement to an ability to communicate and to overall quality of life, and are the mainstay in the management of hearing loss. (1) The role of the audiologist is paramount, not only in the assessment and fitting of a hearing aid, but in the ongoing adjustment which is essential in maintaining optimal results and compliance; this often requires time and patience from both patient and audiologist. Newer digital aids continue to improve hearing results, but there is still good utility to be had from analogue aids(11), given that they are significantly cheaper. The advantage of digital aids is their ability to filter out many extraneous sounds which may also be helped by using directional microphones. Digital aids also enable  the patient to give feedback regarding sound quality, allowing the audiologist  to make appropriate changes.

 It is important for patients to realise the limitations of hearing aids, however, which will minimise dissatisfaction and poor compliance. These limitations revolve around  underlying speech discrimination. With poor discrimination, amplification will simply magnify a distorted sound. Other issues are feedback, and occasional problems due to underlying ear disease, as outlined above Cosmesis and the stigma of hearing aids remains a problem, but the newer age of digital music devices are improving overall acceptance, especially in the younger age groups.

The cost of hearing aids is also an important consideration for many patients, especially when bilateral aids are needed. The Commonwealth Hearing Services Program exists to provide free hearing assessment, rehabilitation and selection and fitting of hearing aids, if necessary, to eligible people, including pensioners and veterans.

Cochlear Implantation

When hearing aids lose their effectiveness, consideration of cochlear implantation should be made. As with the improvement in digital hearing aids, advances in implantable hearing aid technology has significantly increased the number of those who will gain benefit from their use. The following list is a useful screening tool for those who despite appropriate use of hearing aids, should be considered for cochlear implantation: inability to follow the TV without subtitles, can only hear on the telephone with well known speakers, worried about losing their job, avoidance of social situations, inability to follow a group conversation, unable to hear in noisy environments, concern about social isolation loneliness or depression. Formal assessment should then be conducted by a specialised audiologist, conducted with maximally tuned hearing aids.

Importantly, there is solid evidence to support the benefit of implantation even when there is a moderate degree of residual hearing.

 

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Further expansion of the indication for implantation has occurred with the introduction of hybrid devices which combine electrical and acoustic stimulation. For patients with severe-to-profound highfrequency hearing loss combined EAS appears to offer a significant, everyday, long-term benefit This allows the optimum benefit of preserving residual low tone hearing, but more efficiently rehabilitating high tone loss. (12)

 In the same way that bilateral aiding is beneficial so to is bilateral implantation, especially improving speech discrimination in noisy situations. (13)

Age in and of itself is not a contra-indication to implantation, which is now routine surgery. (14) However, whilst the implantation process itself is straightforward, the patient and their family must be motivated to essentially relearn how to hear. The period of sound deprivation and the degree of residual speech recognition are the most reliable predictors of post-implantation results. (15)

Middle Ear Implants

The recent development of middle ear implants  introduces another option for people with moderate to severe sensorineural hearing loss. A floating mass transducer is attached to the incus which converts a signal into mechanical vibrations. The internal component is attached to the external microphone via a transcutaneous magnet. Signal processing is highly advanced, and is especially beneficial for those who have problems wearing standard hearing aids, and avoids most problems with feedback. (16,17)

Single Sided Neural Deafness A quick mention should be made of the scenario where the hearing on one side is reasonable and there is very little residual hearing in the other ear. A standard hearing aid in this situation is of no benefit. The only option for hearing  rehabilitation is that of a bone anchored hearing aid. This utilises the very low attenuation of sound through bone conduction. A slight delay in the sound signal to the good ear allows the brain to create the illusion of binuaral hearing. It is especially helpful when hearing in background noise and for directional sense. 

 Tinnitus

Tinnitus is the perception of sound in the absence of external acoustic stimulation. For the patient it may be trivialor it may be a debilitating condition. Whilst the pathophysiology is complicated, it is usually a  sequelae of hearing loss, so the incidence increases with age.

The neurophysiological model is useful for assessment and management. Tinnitus is  generated when a signal within the auditory system which is normally suppressed by the subconscious brain becomes noticed. Reinforcement can occur due to the formation of a positive feedback loop either from a linkage to the limbic system or the trigeminal nucleus. This means that emotional or physical stress, temporomandibular or cervical problems can amplify the sensation of tinnitus. Management is multifactorial, including treating the hearing loss, sound therapy, and tinnitus retraining therapy (a form of cognitive behavioural therapy). (18,19)

Dizziness

Up to 50% of dizziness can be attributed at least in part to vestibular dysfunction.(20,21) Uncompensated vestibular hypofunction results in postural instability, visual blurring, and subjective complaints of imbalance. The assessment and management of dizziness is a multi-disciplinary challenge, but treatment of the vestibular dysfunction centres around vestibular rehabilitation. True rotational vertigo is more specific for peripheral vestibular pathology, with BPPV and vestibular migraine being the most common diagnosis. 

 In summary, the impact of hearing loss is significant, but appropriate rehabilitation greatly improves quality of life.

 Hellen Keller:

“… blindness separates you from things,  deafness separates you from people.”

 

References

1.            Hogan A OLK, Miller P, Kendig H. The Health Impact of a Hearing Disability on Older People in Australia. Journal of Aging and Health 2009;1098.

2.            Mulrow D, Murphy  A. Review: Screening for hearing impairment in elderly patients is useful [Diagnosis]. Cochrane Database of Systematic Reviews

 1991.

3.            Newman CW, Weinstein BE, Jacobson GPet al. The Hearing Handicap Inventory for Adults: psychometric adequacy and audiometric correlates. Ear and hearing 1990;11:430-3.

4.            Burton MJ, Doree C. Ear drops for the removal of ear wax. Cochrane Database of Systematic Reviews 2009;4.

5.            Obholzer RJ, Rea PA, Harcourt JP. Magnetic resonance imaging screening for vestibular schwannoma: analysis of published protocols. The Journal of laryngology and otology 2004;118:329-32.

6.            Bakkouri WE, Kania RE, Guichard JPet al. Conservative management of 386 cases of unilateral vestibular schwannoma: tumor growth and consequences for treatment. Journal of neurosurgery 2009;110:662-9.

7.            Sandooram D, Grunfeld EA, McKinney Cet al. Quality of life following microsurgery, radiosurgery and conservative management for unilateral vestibular schwannoma. Clinical otolaryngology and allied sciences 2004;29:621-7.

8.            Ohlemiller K. Age-related hearing loss: the status of Schuknecht’s typology. Current Opinion in Otolaryngology & Head & Neck Surgery 2004;12:439–43.

9.            Verbeek JH, Kateman E, Morata TCet al. Interventions to prevent occupational noise induced hearing loss. Cochrane Database of Systematic Reviews 2009;4.

10.          Luebke AE, Foster PK. Variation in inter-animal susceptibility to noise damage is associated with alpha 9 acetylcholine receptor subunit expression level. J Neurosci 2002;22:4241-7.

11.          Taylor R S, Paisley S. The clinical and cost effectiveness of advances in hearing aid technology: report to the National Institute for Clinical Excellence (Structured abstract). Cochrane Database of Systematic Reviews 2001.

12.          Talbot K, Hartley D. Combined electro-acoustic stimulation: a beneficial union? Clinical otolaryngology and allied sciences 2008;33:536–45.

13.          Eapen RJ, Buss E, Adunka MCet al. Hearing-in-noise benefits after bilateral simultaneous cochlear implantation continue to improve 4 years after implantation. Otology & Neurotology 2009;30:153-9.

14.          Eshraghi A. Cochlear Implant Surgery in Patients More Than Seventy-Nine Years Old. Laryngoscope 2009.

15.          Leung J, Wang NY, Yeagle JDet al. Predictive models for cochlear implantation in elderly candidates. Archives of otolaryngology–head & neck surgery 2005;131:1049-54.

16.          Truy E, Philibert B, Vesson JFet al. Vibrant soundbridge versus conventional hearing aid in sensorineural high-frequency hearing loss: a prospective study. Otol Neurotol 2008;29:684-7.

17.          Mosnier I, Sterkers O, Bouccara Det al. Benefit of the Vibrant Soundbridge device in patients implanted for 5 to 8 years. Ear and hearing 2008;29:281-4.

18.          Hobson J, Chisholm E, Loveland M. Sound therapy (masking) in the management of tinnitus in adults. Cochrane Database of Systematic Reviews 2009;4.

19.          Phillips JS, McFerran D. Tinnitus Retraining Therapy (TRT) for tinnitus. Cochrane Database of Systematic Reviews 2009;4.

20.          Ruckenstein MJ, Staab JP. Chronic Subjective Dizziness. Otolaryngologic Clinics of North America 2009;42:71-7.

21.          Hall CD, Cox LC. The Role of Vestibular Rehabilitation in the Balance Disorder Patient. Otolaryngologic Clinics of North America 2009;42:161-9.