audiometry

Auditory disorders and pathologies


Pathology is the study of diseases and disorders and their effect. Many, many problems can manifest themselves in the ear. Some malfunctions are of a minor, temporary nature, or can be treated with minimal medical intervention. Other disturbances to the hearing organ can require surgery or their pathology is irreversible, ie permanent. A hearing loss can be caused by any number of pathologies at any stage along the hearing pathway.

Hearing loss can be caused by trauma, infection, tumours and medications. They can be related to the process of ageing or be congenital. Sometimes they are caused by environmental factors and sometimes it is not known what causes a hearing loss. It is the role of a medical practitioner to make a decision about the pathology of hearing loss.

Audiometrists are not medically trained so they cannot make a judgement about the cause of hearing loss. It is possible that the client comes to your clinic having already been diagnosed with a particular pathology; however, it is much more likely that you will not have this information available. There are a number of specialists that may comment on the pathology of hearing loss. These include the Ear, Nose and Throat specialist, the paediatrician and the geneticist.

If a client expresses a desire to establish why they have a hearing loss then you should advise them to speak to their family doctor for more information. If there is a problem with the ear then it is likely that it will cause some hearing loss. Whether the hearing loss is temporary or permanent will depend on where in the hearing mechanism the problem occurs, ie the site of lesion. The main effect of a hearing loss is on communication. The communication effect of the hearing loss will depend on when the hearing loss started, the degree of the hearing loss and how soon habilitation or rehabilitation occurs.

Suggested learning resources

There are many textbooks that can help you with this topic. The following textbooks are all relevant and you may decide to refer to them as you study this topic. You may also like to access the internet. There are hundreds of internet sites that describe pathologies of the ear.

TITLE Clinical Audiology: An Introduction
AUTHOR Stach, B.A.
PUB DATE 1998
PUBLISHER Singular Publishing Group Inc, San Diego
ISBN 156593346X

TITLE Hearing in Children
AUTHOR Northern, J.L. & Downs, M.P.
PUB DATE 5th Edition, 2002
PUBLISHER Lippincott Williams & Wilkins, Philadelphia
ISBN 0683307649

ISBN 06830062TITLE Handbook of Clinical Audiology
AUTHOR Katz, J. et al.
PUB DATE 6th Edition, 2007
PUBLISHER Williams & Wilkins, Baltimore. Md.
TITLE Audiology: The Fundamentals.
AUTHOR Bess, F.H. & Humes, L.E.
PUB DATE 2nd Edition, 1995
PUBLISHER Williams & Wilkins, Baltimore. Md.
ISBN 0683006207

TITLE Introduction to Audiology
AUTHOR Martin, F.N. & Clark, J.G.
PUB DATE 11th Edition, 2011
PUBLISHER Allyn & Bacon, Boston
ISBN 0205366414

TITLE Basic Principles of Audiology Assessment
AUTHOR Hanley, M.
PUB DATE 1991
PUBLISHER Prentice-Hall, USA
ISBN 0205135528

TITLE Audiology
AUTHOR Newby, Hayes.
PUB DATE 1992
PUBLISHER Prentice-Hall, New York
ISBN 0130519219

Hearing loss present from birth

Hearing loss that is present from birth is referred to as congenital. There are many causes of congenital hearing loss some of which are hereditary but many are related to other factors and for many babies born with a hearing loss there will be no known reason.

Congenital hearing loss can be of any degree and of any configuration. That is, the hearing loss can be mild, moderate, severe or profound. It may be that only one ear is affected or there may be a difference between the ears.

About one to three babies out of every thousand are born with a permanent hearing loss. The hearing loss may remain stable or may become worse over time, so children with hearing loss are monitored carefully. Some babies have a temporary condition that may improve over time with or without treatment.

There are Neonatal Hearing Screening Programs in some states of Australia. The New South Wales Department of Health started the State-wide Infant Screening – Hearing Program in December 2002. For more information about this you can visit the NSW neonatal screening for hearing loss program website: http://www.health.nsw.gov.au/hearing/statewide.html

Any hearing loss can have an impact on the child’s development of speech and language skills. Therefore, it is considered very important that paediatric audiologists test babies that do not pass the screening program.

Some babies are born with a syndrome or a malformation that may impact on hearing. These may or may not affect the baby immediately but these babies will probably be monitored to make sure that the hearing is not affected.

There are risk factors for hearing loss. These include in utero infections such as rubella, toxoplasmosis and cytomegalovirus. Some of these have an immediate impact on the hearing but some do not.

Another risk factor for hearing loss is if a member of the family has a hearing loss that has no known cause. For example, if the grandfather of the child has a hearing loss that was present from a young age then it is considered that the child has a family history of hearing loss. However, if the family member has a hearing loss caused by an environmental factor or age then it is not considered a family history. For example, if the grandfather has a hearing loss caused by noise exposure then it is not considered to be family history.

For more information about the causes of hearing loss you can visit this website:
http://www.aussiedeafkids.com/Phidcoz/causes.html

Common physical abnormalities of the ear

Occasionally children are born with some abnormality of the ear. This may be obvious such as ear tags and pits, microtia and atresia. These are seen easily at birth and these babies will be asked to go to a paediatric audiology clinic for testing as they may indicate that a hearing loss exists.

Some abnormalities of the ear cannot be seen. Mondini and Michel deformity affect the cochlea and cannot be seen unless special scans are done. You can find more information about these from many books. One excellent reference for this is Northern, J.L. & Downs, M.P. (2002) Hearing in Children.

Sometimes a Paediatrician will say that a baby has dysmorphic features. This means that the baby has unusually shaped features.

Syndromes

There are many syndromes that can include hearing loss. If you have a client with a particular syndrome it is worthwhile taking the time to find out if hearing loss is considered a possibility with that syndrome. You should also try to find out what type of hearing loss is associated with the syndrome and whether it is likely that the hearing loss is progressive because this will affect how you manage the client’s care. You will find information from many sources but the following books will give you a starting point:
• Northern, J.L. & Downs, M.P. (2002) Hearing in Children.
• Shprintzen, R.J. (2001) Syndrome Identification for Audiology, an Illustrated Pocket Guide
• Shprintzen, R.J. (2000) Syndrome Identification for Speech-Language Pathology, An Illustrated Pocket Guide

Syndromes will affect the ear in different ways. For example, common syndromes that affect the middle ear include Achondroplasia, Treacher Collins Syndrome, BOR Syndrome, Cleft Lip/Palate and Down Syndrome. These syndromes may be related to malformations of the outer or middle ear that cannot be treated surgically or may be related to fluctuating middle ear problems that can be treated medically.

Some syndromes will effect both the middle and inner ears. For example, Turner Syndrome, CHARGE Association.

Some syndromes will effect the inner ear and may be progressive: Usher Syndrome; Waardenburg Syndrome; Marshall Syndrome; Neurofibromatosis Type II.

Achondroplasia

People with achondroplasia have a skeletal abnormality that means they will be very short and the head will be large and the arms and legs are short. It is also referred to as Dwarfism. You can find more information at http://www.sspa.org.au/sspa.htm the official website of the Short Statured People of Australia.

Cleft Lip/Palate

Babies born with clefts of the palate and lip are often tested. This is because they are at risk for hearing loss. This hearing loss may be of a permanent nature or may be related to middle ear problems. If babies develop middle ear problems at a very young age it is likely that they will be under the care of an Ear, Nose and Throat Specialist and have their hearing monitored closely. There is information, photos and links to other websites on the website http://www.cleftpals.org.au/ that is maintained by The Cleft Lip and Palate Society, an Australian volunteer, non-profit organisation.

CHARGE Association

Information from the Australasian CHARGE Syndrome Association is at http://www.austcharge.com.au/. The ear is often malformed and there may be a hearing loss.

Usher Syndrome

There are a few different types of Usher Syndrome. Hearing loss co-exists with a visual impairment. The type relates to the severity and onset of the syndrome. Information is available at http://www.retinaaustralia.com.au/AssocConditions.htm.

Neurofibromatosis

There are two types of neurofibromatosis. Hearing loss is common in the Type 2. The hearing loss usually starts after childhood and is related to acoustic neuroma (discussed later in this Learning guide).

It is not possible to do justice to the topic of syndromes in this learning guide. You should spend some time exploring ways of obtaining information about syndromes so that if you are asked to see someone with a syndrome then you will be able to get some idea of the type of hearing loss associated with the syndrome and whether the hearing loss is progressive. If you cannot find information about a syndrome you can ask the client or their caregivers if they know whether there is any hearing loss associated with the syndrome. The internet, even a Google or Yahoo search often yields quite good and easily-accessible information about syndromes (as long as you spell it correctly).

Pathologies of the outer ear=

Can pathologies in the outer ear cause significant hearing loss? Generally the answer is no. The deficit, if any, resulting from an outer ear pathology, is minor and temporary.

Can pathologies of the outer ear be treated medically? Generally the answer to this is yes.

The pinna

If the pinna has been damaged through accident or partially removed through surgery, there is no effect on the ear’s ability to hear. However if the pinna is congenitally malformed, it may be associated with malformations of other parts of the ear or other syndromes that cause hearing impairment.

The condition where there is a small or malformed pinna is referred to as microtia. If the ear canal is very narrow it is called a stenosis of the EAM. If the ear canal doesn’t exist or is blocked by bone, it is called an atresia of the EAM.

If there is no external auditory meatus sound cannot reach the inner ear as easily and therefore there will be some hearing loss. The cochlea, however, is usually not affected.

Perichondritis

This is where there has been damage to the cartilage of the pinna. This can happen through trauma or infection. It usually results in a malformed pinna that is commonly referred to as cauliflower ear. If the trauma or infection has not affected any other part of the ear then it will not cause hearing loss. However, there is a possibility that whatever has caused the perichondritis has also affected the inner ear and/or middle ear..

Otitis externa

An infection occurring in the skin of the external auditory canal. Sometimes referred to as “swimmer’s ear”, otitis externa can be very painful and itchy. It can be treated with oral (ie, taken by mouth) antibiotics or ear drops. The skin can become quite swollen and inflamed. The condition is often accompanied by a rise in body temperature. When the condition is advanced, the tympanic membrane can also become inflamed and may develop blood blisters on its surface. Usually it is difficult to assess a person’s hearing with this condition, as the placement of earphones is painful. However, hearing loss, if present, would usually be minimal and temporary.

Occluding cerumen

Cerumen is the term we use to describe wax. You can use either term but your clients are more likely to understand the word wax. Cerumen in the ear canal is normal. It is only when the cerumen blocks the ear canal that it becomes a problem.

Excessive cerumen that is blocking the ear canal can cause some hearing loss particularly if it is hard and impacted.

The doctor may need to remove occluding cerumen prior to a hearing assessment to obtain exact threshold levels. The cerumen can be softened with ear drops that have been applied over several days and indeed this may be enough for the cerumen to dislodge itself and move out of the ear canal. Wax drops should be used with caution and it is best if you advise your client to ask their Doctor’s advice.

Under no circumstances should the client try and remove the cerumen with cotton buds or other such implements as they can tend to force the cerumen deeper into the ear canal and may perforate the TM.

Perforations of the tympanic membrane

Holes or perforations may appear in the tympanic membrane through a variety of incidents. The tympanic membrane may rupture through excessive pressure in the middle ear cavity or it may be pierced by a foreign object in the ear canal such as a bobby pin or cotton bud. Sudden pressure in the external auditory canal may also perforate the tympanic membrane. This is called barotrauma. This pressure may be caused by something as severe as a blast or by something as simple as clapping a hand over the ear. Perforations generally heal by themselves over a period of weeks. However, perforations caused by continuous infections may not heal and surgery may be required. A tympanoplasty is an operation that involves grafting a piece of skin over the hole. Providing the perforation heals, hearing should improve once the tympanic membrane is intact.


The effect of pathologies of the outer ear

Pathologies of the outer ear do not normally cause a permanent hearing problem.

It is very likely medical treatment will be possible, and will restore the hearing.

Hearing loss caused by pathologies of the outer ear is called conductive loss.

The hearing loss caused by pathologies of the outer ear is usually of a mild degree. At worst, the hearing loss may be of a moderate degree.

Pathologies of the middle ear

How do pathologies in the middle ear affect the conduction of sound through this section? How significant an impact on hearing levels do they have and are they temporary or permanent? Generally pathologies in the middle ear are temporary but many need significant medical treatment for correction. Some pathologies are genetic and result in a permanent hearing loss of a conductive nature. This may be because the structures of the middle ear, particularly the ossicles, have not formed properly.

Otitis media

Otitis media is an infection of the middle ear space. It is one of the most common pathologies of the middle ear, especially in children. Remembering that the middle ear cavity is lined with mucous membrane, it is easy to understand how the infection occurs. Any infection of this lining is referred to as otitis media. Usually organisms gain entry to the middle ear cavity via the Eustachian tube, or through a perforated tympanic membrane. The lining of the middle ear becomes swollen with the infection. The infection process may spread rapidly, with the initial appearance of a retracted tympanic membrane due to interference of the pressure-equalisation function of the Eustachian tube. Otoscopic inspection may reveal the retracted tympanic membrane and may also show a red ear due to the area becoming very vascular. If no treatment is received at this stage suppurative otitis media may result with the production of pus in the cavity. Pain is usually evident at this stage and elevated temperatures may be observed.

Treatment for otitis media may include the use of antibiotics. If the condition persists the middle ear cavity may be cleared of fluid by myringotomy, ie making an incision in the tympanic membrane. Usually grommets, also called ventilation tubes, are inserted in the tympanic membrane to aerate the middle ear. This procedure aids the ear in keeping equal air pressure on both sides of the tympanic membrane. The grommets may be in position for up to 18 months. There are many different types of grommets and if necessary there are some that are designed to stay in place (in situ) for longer.

If the condition continues without treatment, rupture of the tympanic membrane may result. This will generally coincide with relief from the pain. The pus will then seep into the external auditory meatus. Pus that does not leave the middle ear cavity in this manner may occupy the mastoid cavity. Mastoiditis may result. Aggressive treatment is required to treat this condition. If untreated it can lead to very serious complications including meningitis.

A hearing loss usually occurs with otitis media. The level of hearing loss depends on the progression of the disease. A return to previous hearing levels is expected after medical intervention.

There are certain people that are very prone to otitis media. This includes children: under 8 years of age; with Down Syndrome; with Cleft Palate and Indigenous Australians.

There are many textbooks that can help you to understand otitis media including Bess, F.H. & Humes, L.E. (1995) Audiology: The Fundamentals Williams & Wilkins, Baltimore. Md.

You can also visit the following website for more information on otitis media:
http://pediatrics.about.com/od/childhoodinfections/a/ear_infections.htm

Cholesteatoma

This is a squamous tissue tumour resulting form skin being introduced into the middle ear cavity. This may occur as a result of a perforated tympanic membrane. Perforations that occur within the attic, or pars flaccida, of the tympanic membrane are particularly susceptible to the formation of cholesteatomas. Cholesteamtomas are very aggressive and can be extremely dangerous. They can spread and may erode parts of the ear. Secondary infections generally accompany a cholesteatoma. Otorrhea, a smelly discharge, is common with this condition.

Depending on the cholesteatoma, there may or may not be a hearing loss. It is a serious medical condition as it can spread. If you ever see a cholesteatoma, and they are quite rare in adults, you should tell your client to see a doctor IMMEDIATELY.

Surgery is the best option for a favourable outcome to this condition. The surgeon must ensure all signs of the cholesteatoma are removed, otherwise the condition will still exist and will recur.

Otosclerosis

This condition refers to the over-calcification within the ossicular chain, causing a conductive hearing loss. The condition is often hereditary and causes a conductive hearing impairment. Generally only seen in adults, the condition is progressive and more aggressive in pregnant or menopausal women due to hormonal changes during these periods. Otosclerosis involves extra growth of spongy bone, normally around the stapes. The condition can be unilateral or bilateral. With this bony growth the stapes footplate becomes fixated to the oval window, unable to impress the vibrations upon it efficiently. Tinnitus often accompanies the condition. Otoscopic examination will usually be unremarkable. However the promontory may become quite vascular emanating a rosy glow that can be seen through the tympanic membrane. This glow is referred to as the Schwartze sign.

Hearing loss is progressive but the cochlea is usually unaffected.

Another phenomena that occurs with otosclerosis is the paracusis willisii affect. It is common for hearing impaired clients to mention difficulty in hearing in background noise. However with hearing losses caused by the middle ear, speech is easier to hear when there is background noise. This happens because we tend to raise our voices when in noise but the loss caused by the middle ear is essentially a loss in amplitude. A person with otosclerosis will enjoy being in surroundings where people talk louder!

Otosclerosis can be treated surgically. The fixated stapes is removed and replaced with a prosthesis, ie, a plastic piece that acts as a replacement for the stapes. This procedure is referred to as a stapedectomy.

The hearing loss associated with this condition may be moderate to severe. Surgery can improve the condition of the middle ear to near-normal status. Surgery is not always successful and some clients may opt to be fitted with hearing aids.

Ossicular discontinuity

When a blow or blast to the ear occurs, trauma to the middle ear can result. The tympanic membrane can be perforated, but the ossicular chain can also be disturbed. Ossicular discontinuity occurs when there is a break or breaks in the ossicular chain. The tympanic membrane may also be significantly ruptured, leaving the ossicles hanging ‘in mid air’, so to speak! Otoscopic inspection may reveal a torn tympanic membrane and visible ossicles attached to their tendons in the middle ear space. The accompanying conductive hearing loss is moderately-severe and the middle ear will need to be repaired surgically. Complete reconstruction of the ossicular chain and tympanic membrane is difficult and some permanent hearing loss may result.

The effect of pathologies of the middle ear

Pathologies of the middle ear do not normally cause a permanent hearing problem. However, if there is a congenital malformation of the middle ear it may lead to a permanent hearing loss.

It is likely medical treatment will be possible which may restore the hearing.

Hearing loss caused by pathologies of the middle ear is called conductive loss.

The hearing loss caused by pathologies of the middle ear may be of a mild or moderate degree.


Pathologies of the inner ear

The most common type of hearing loss in adults is called sensorineural hearing loss. Sensorineural hearing loss occurs in the inner ear or along the neural pathway and is permanent. It most commonly involves permanent damage within the cochlea.

How are sensorineural losses different from conductive losses? A sensorineural hearing loss will cause a loss of sensitivity to sound but will also cause a loss of clarity. That is, the person will have discrimination problems.

Common symptoms of sensorineural hearing loss include dizziness, vertigo and tinnitus.

Meniere’s syndrome

Meniere’s syndrome is sometimes also referred to as Meniere’s disease and endolymphatic hydrops. Some people make a distinction between these 3 terms.

This disease is typified by a sudden loss of hearing in one ear, of a sensorineural nature but predominantly in the low frequencies. The hearing loss usually fluctuates until the condition stabilises. The hearing loss tends to increase in severity and although the hearing may recover in between episodes there is often some residual hearing loss. The person is usually left with a permanent hearing loss even after they stop having episodes.

Violent vertigo and nausea attacks of sudden onset may also accompany Meniere’s syndrome but different people with experience different degrees of these symptoms. The condition usually begins with an episode sensation of fullness in one ear, including vertigo, a dull roaring tinnitus, difficulty with speech discrimination, sensation of extreme turning in space and vomiting. An episode can last for several days. An episode (Menieres attack) can occur at any time without warning. Meniere’s syndrome is thought to originate in the labyrinth and is related to the over-secretion of endolymph. Pressure builds up in the cochlea duct causing the vertigo. Medical treatment of Meniere’s syndrome is less than satisfactory as there is no cure and the client tends to ‘grow out’ of the condition with the attacks becoming less violent and frequent as time passes. Some treatments limit fluid retention and sodium intake. No one treatment has significant results hence the development of Meniere’s syndrome support groups to help clients with this truly debilitating affliction. Nonetheless, clients should be encouraged to see an Ear Nose and Throat Specialist as certain treatments can help reduce symptoms and the frequency of attacks.

You should take the time to find out more about Meniere’s syndrome. The Meniere’s Support Group of NSW maintains a website with links to more information at http://www.hinet.net.au/~nswmsg/links.htm. You could also look at this website for additional information: http://oto.wustl.edu/men/.

Meningitis

The meninges are the lining of the brain. Meningitis is an infection of the meninges. The meninges may become infected with a virus or bacteria. Meningitis has the potential to result in very serious complications. One of these complications can be a loss of hearing. The hearing loss can be unilateral (one sided) or bilateral (two sided). The loss can be a profound, ie of great significance, sensorineural hearing impairment. Meningitis is a common cause of permanent acquired hearing loss in children.

Noise Induced Hearing Loss

When the human ear is exposed to excessive noise over a period of time, a hearing loss can occur. Currently in most states of Australia, excessive noise is described as noise which is greater than 85dBA over an eight hour period. Hearing loss through noise injury can occur in two ways. It can be slow and progressive over a period of time or it can be instantaneous through an acoustic trauma such as a blast.

The term that is usually used with progressive hearing loss associated with noise is NIHL or Noise Induced Hearing Loss.

It is often characterised by periods of TTS followed by PTS. That is, temporary threshold shift followed by permanent threshold shift.

The temporary threshold shift will occur when the outer hair cells of the cochlea are able to recover. Many people experience this after being in a noisy place and will describe the sensation of feeling like their ears are stuffed with cotton wool. They will also usually experience tinnitus. It may take the ears up to 16 hours, and sometimes even longer, to recover. If the ears are continually exposed to excessive noise causing a TTS then recovery cannot take place and a permanent threshold shift occurs. That is, a permanent hearing loss.

If the ear is not able to recover from the noise a permanent hearing loss of a sensorineural nature will develop. The hearing loss is characterised in the initial stages by normal hearing in the low and mid frequencies with a mild loss occurring in the high frequencies. As the pathology progresses the high frequencies become more depressed and the hearing loss spreads to the mid and low frequencies. The shape of the audiogram for noise injuries is characterised by a ‘noise notch’ configuration. This is where the greatest point of the hearing loss will occur at either 3000, 4000 or 6000Hz and the hearing will have recovered to some extent at 8000Hz. This gives the audiometric results a V or notch configuration.

Acoustic Trauma

Hearing loss through noise injury can result in a profound or complete loss through trauma, although this is uncommon.

So how does the noise damage the inner ear? Remember that our hair cells are arranged in four rows, ranging from high frequency cells at the basal (oval window) end of the cochlea, and they wind up to low frequency cells at the apical end of the cochlea. When excessive noise bombards these cells, it is the high frequency ones that receive the brunt of the noise. After a significant period the cells can take no more so they ‘lie down’ to rest - much like walking over a lawn and trampling down some grass blades. This is often referred to as a temporary threshold shift. After a period of rest from the noise, (usually sleep or a weekend break from the noise), the hair cells will recover - as does lawn grass when no-one is trampling on it and stand up to discriminate the sounds again. Eventually over time the hair cells will not be able to recover from repeated noise exposure and a permanent threshold shift will result. This is much like people repeatedly walking across a strip of lawn and eventually the grass will die, leaving a brown path through the lawn.

A condition known as recruitment can sometimes be apparent in noise injury sufferers. Recruitment results from a reduced dynamic range where the difference between a sound that is perceived as soft and a sound that is perceived as loud is reduced. This condition makes it difficult when fitting hearing aids as the loudness of the hearing aid must be closely monitored. However, knowing of its existence explains why some hearing impaired people ask you to speak up and when you do, you are accused of shouting. Loud sounds ‘hurt’, even if they are only slightly louder than threshold levels. Recruitment is also evident in other forms of sensorineural hearing loss.

Head Trauma

We know that a blow to the head can cause middle ear loss through perforation of the tympanic membrane and/or dislodgment of the ossicular chain. Further damage in the inner ear can also occur from head trauma. The inner ear may be harmed in any number of ways, from being torn or stretched, or from loss of oxygen causing deterioration to the hair cells. The cochlea itself can become fractured, presenting a severe to profound hearing loss. The Organ of Corti may be flattened or destroyed completely. Rupture of the round window is also possible, especially from diving accidents or acoustic trauma. A fistula can also result from trauma allowing fluid to leak out from the cochlea. A fistula is an abnormal opening in the oval or round windows. Any of these conditions will result in a significant sensorineural hearing loss.

Presbycusis

Presbycusis is also sometimes written as Presbycusis. It is an acquired loss of hearing associated with the aging process.

It is reasonable to presume that this process actually begins early in life as our ability to hear ultra high frequencies has deteriorated by the age of 18. However, this does not explain why some of us lose our hearing through the aging process and some of us retain relatively good hearing well into our 80’s or 90’s. The process of losing one’s hearing through age can be equated to the condition of baldness. Some of us lose our hair, some of us don’t. Those of us that are losing our hair, lose only some of it, others all of it. Some of us lose our hair quickly, others much more slowly. The same can be said of losing our hearing.

Presbycusis involves the cochlea but probably also involves a deterioration of the neural pathways. The resultant hearing loss may vary from mild to profound and again begins in the high frequencies, but usually does not produce the ‘notch’ characteristic of noise injury. Hearing loss from presbycusis is usually bilateral, gently sloping high frequency and of a sensorineural nature.

Recruitment is also common in presbycusis. Poor speech discrimination is often a feature of presbycusis. That is, even when speech is made loud enough to be heard the person still has trouble understanding what is said.

Acoustic Schwannoma or Acoustic Neuroma

This generally benign tumour grows on the eighth nerve usually in the internal auditory meatus at the brain stem. The area known as the cerebellopontine angle provides a perfect space for this type of tumour to develop from the internal auditory canal. Tumours are usually unilateral but may be bilateral.

The larger the acoustic neuroma, the more likely it will cause disruptions to the hearing and balance. The tumour can also put pressure on the facial nerve as this is also situated within the internal auditory canal. Symptoms of unilateral or asymmetrical hearing loss, balance problems (usually falling to one side) and facial palsy are strongly indicative of an acoustic neuroma. Unilateral tinnitus and a feeling of fullness or pressure on one side of the head will also be alarming to the clinician if reported. Speech discrimination is usually worse than would be expected for the degree of hearing loss.

Surgery is one option for a neuroma. Occasionally, neuromas are monitored to see whether their removal is necessary or whether removal will cause more problems. Ear, Nose and Throat Specialists and/or Neurosurgeons make these sorts of decisions.

During surgery the acoustic nerve might be damaged, resulting in partial or complete hearing loss on that side. If the facial nerve is involved and also has to be severed, facial palsy will result along with over-lacrimation (ie, excessive production of tears) of the eyes and alterations in the sense of taste, as these functions are managed by branches of the facial nerve. However, there is intra-operative monitoring of the facial nerve that usually means that its function is retained.

Ototoxic medications

Ototoxic literally means poisonous to the ears. There are many medications that can result in a hearing loss. Most of these will cause a permanent hearing loss but some hearing loss from ototoxic medication is reversible. Some ototoxic medications will also cause tinnitus and/or vestibular problems.

Some medications that may cause hearing loss and or tinnitus are:
• Aminoglycosides: these are a group of antibiotics that include Gentamycin
• Salicylates: aspirin is a salicylate that, when high doses are used, causes a hearing loss that is reversible
• Quinine is an anti-malarial that causes a reversible hearing loss
• Anti-cancer medications especially Cisplatin.

You may wonder why a medication would be used if it causes a permanent hearing loss. The answer is usually that there is no other choice. Hearing will often be monitored if the person is well enough to be tested.

Large Vestibular Aqueduct Syndrome

LVAS refers to an anomaly of the inner ear. The vestibular aqueduct is attached to the inner ear at the vestibule and is filled with perilymph. The name of the syndrome is self-explanatory – the vestibular aqueduct is larger than it should be. The diagnosis of this syndrome has been made possible with the sophisticated scanning that is now available.

It is not clear exactly how the large vestibular aqueduct causes a hearing loss but it is well documented that people with LVAS can lose their hearing suddenly from minor trauma, ie a small bump to the head may cause an immediate and significant loss of hearing. If treated immediately there can be some recovery. Treatment can involve steroids so an urgent doctor’s appointment should be encouraged.

Idiopathic Sudden Hearing Loss

Idiopathic means that the reason for the hearing loss is not exactly known. That is, for some reason that particular person has a sudden loss of hearing that does not relate to any external cause and there is nothing obvious causing the loss.

This type of hearing loss can be very difficult for the person because it is not able to be explained and the effect of the loss is dramatic. If a person came to you describing that their hearing has dropped suddenly you could do a hearing test but you would encourage the person to go to their doctor immediately because occasionally doctors can take steps to stop further deterioration or to help recover some of the hearing.

The effects of pathologies of the inner ear

Pathologies of the inner ear normally cause a permanent hearing problem.

It is unlikely medical treatment will restore the hearing.

Hearing loss caused by pathologies of the inner ear is called sensorineural loss.

The extent of the hearing loss can range from mild to profound.

Summary


PATHOLOGY
SYMPTOMS
OTOSCOPIC INSPECTION
HEARING LOSS
Otitis Externa
Pain, itchiness
Redness, flaky skin, swelling
Minimal, temporary conductive
Occluding Wax / Cerumen
Reduced hearing
Cannot see the tympanic membrane
Minimal, temporary conductive
Perforation
Reduced hearing
A hole in the tympanic membrane
Temporary conductive, may be mild or moderate
Otitis Media
Pain, fever, reduced hearing
Tympanic membrane is red and perhaps bulging
Temporary conductive. The level of hearing loss depends on the progression of the disease.
Cholesteatoma
Reduced hearing or there may be no symptoms.
Whitish growth in the tympanic membrane, possibly with a smelly discharge.
There may or may not be a hearing loss.
Otosclerosis
Reduced hearing, possibly tinnitus
Normal tympanic membrane and ear canal, sometimes a rosy glow on the TM.
Unilateral or bilateral, conductive, progressive, medically treatable
Ossicular Discontinuity
Reduced hearing
Malleus may not be visible behind the tympanic membrane, possibly a torn tympanic membrane
Conductive, moderate
Meniere’s Syndrome
Dull roaring tinnitus, severe nausea and vertigo, sensation of fullness, sudden hearing loss that fluctuates, difficulty with speech discrimination
Normal tympanic membrane and ear canal
Sudden onset, fluctuating, sensorineural, affects the low frequencies to a greater degree
Meningitis
Hearing loss following illness
Normal tympanic membrane and ear canal
Unilateral or bilateral, profound sensorineural hearing loss
Trauma
Sudden hearing loss
Tympanic membrane may be ruptured
Permanent, sensorineural, possibly profound loss
Noise Injury
Gradual hearing loss
Normal tympanic membrane and ear canal
Permanent, sensorineural, possibly a noise notch
Presbycusis
Gradual hearing loss
Normal tympanic membrane and ear canal
Bilateral, high frequency, gently sloping, of varying degrees
Acoustic Schwanoma/ Neuroma
Asymmetrical hearing loss, unilateral tinnitus
Normal tympanic membrane and ear canal
Asymmetrical hearing loss, ie a difference in hearing between the ears. Sensorineural.


Pseudohypoacusis


The aim of a hearing test is to establish the softest sound or threshold for each ear at different frequencies. A very small number of people are unable to do this. Occasionally, a person will deliberately not respond to the softest sound that they can hear. There are many terms that are used to describe this.

Pseudohypoacusis is one of the terms we use to describe this. Other terms that are used include nonorganic hearing loss and malingering.

These terms are usually used to differentiate those people who will not respond to threshold from those who are not capable of completing a hearing test.

In other words, these terms are used to describe people who could do the hearing test if they were motivated to do so. Therefore, there is usually some motivation for not responding to threshold. The motivations for exaggerating hearing levels usually fall under three broad categories: attention seeking; genuine belief that they cannot hear or financial gain.

The people who exaggerate a hearing loss may genuinely believe they cannot hear the sounds being presented so they need very careful handling. There are many tests that can help you to determine if a person is exaggerating their hearing levels. These tests and your developing experience with performing hearing tests will help you to determine the person’s actual hearing thresholds.