Hearing Pathology - a Few Key Pathologies

 

 

Middle ear infection / OTITIS MEDIA

 

Causes and Onset -

 

Middle ear infection (otitis media) is one of the most common illnesses amongst children under the age of five. During the infection the child’s middle ear is filled with fluid. This causes a distortion in the sound reaching the child’s inner ear. As a result the child experiences a temporary hearing loss. Middle ear infection is the most common cause of conductive hearing loss. Otitis Media usually develops from a common cold or upper respiratory tract infection. Untreated allergies and parents who smoke increase the child’s risk of developing an infection.

 

When a child suffers from chronic middle ear infection its hearing abilities will most likely fluctuate from normal to a mild or even moderate hearing loss. Due to this the child runs the risk of developing poor listening skills, which in return can cause or worsen other problems, for instance:

 

  • Speech and language development delays

  • School and learning problems

  • Attention problems

  • Emotional and social problems

  • Behavioural problems

  • The possibility of a permanent hearing loss if the infection is left untreated 

 

Otitis Media may be classified in terms of the duration of inflammation with the following being its major categories of classification:

 

  • Acute Otitis Media – occurs suddenly and only for a short period of time. This form is caused by a bacterial or viral infection of the fluid of the middle ear. The pus resultant from the acute form will last fewer than 21 days

  • Chronic Otitis Media – occurs repeatedly and over a long period of time. This form is a blockage that repeatedly occurs due to allergies, multiple infections, ear trauma or swelling of the adenoids. Chronic

  • Otitis Media may cause permanent damage to the middle ear Otitis Media is far more prevalent in younger persons (under the age of two). The reasons for this may be:

  • In younger children the tube is shorter, more horizontal, and straighter, making it easier for bacteria to enter.

  • The tube is floppier, with a tinier opening that's easy to block

  • Young children get more colds because it takes time for the immune system to be able to recognise and ward off cold viruses

 

Medical Findings

 

Otitis Media is primarily diagnosed using an Otoscope to inspect both the outer and middle ear – although an examination of one’s medical history as well as a physical examination will be conducted. The Otoscope is an instrument that the physician uses to visualise the inside of the ear – it is a lightweight device capable of protruding into the ear cavity. In addition to the standard Otoscope, a pneumatic Otoscope may also be used, which discharges a puff of air into the ear so as to test the eardrum movement.

 

Tympanometry is a further medical test which can be performed. It is an examination used to test the condition of the middle ear and mobility of the eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal.

 

These tests alone cannot provide answers to the question of hearing impairment though – which requires complete audiological testing to be conclusive.

 

Audiological Findings

 

Otitis Media testing should include the complete process of audiological evaluation. This format of testing includes a number of components aimed at establishing the audiometric profile of the individual – extending to the degree of hearing loss for each ear independently. Tests will include Otoscopic evaluation, Tympanometry and air/bone pure tone conduction testing. Findings for these tests which would hint at Otitis Media are as follows:

 

  • Medical history: Allergies/chronic colds/influenza/Cleft lip and palate/HIV/Aids etc.

  • Otoscopic findings: Obscured light reflex/red, inflamed eardrum/retracted eardrum/effusion

  • Tympanometry: Type B tympanogram (no movement of the eardrum due to middle ear infection) or type C tympanogram (negative air pressure in the middle ear system)

  • Air and bone conduction audiometry: An air-bone gap exists between air and bone conduction graphs 

 

Prognosis and Treatment Options

 

Due to the differences in the two forms of Otitis Media (Acute and Chronic), it is necessary to distinguish in terms of prognosis:

 

Acute Otitis Media: A number of symptoms/conditions being more prevalent are eardrum perforations, infections in the mastoid bone, meningitis and brain abscess. Hearing problems are experienced by those who suffer from the acute form, although the difficulties in hearing are not necessarily permanent.

 

Chronic Otitis Media: Due in part to the extended period for which this form is active in the individual, the medical outcome is far less standardised or predictable. The patient will in all likelihood receive outpatient treatment and his/her condition will be monitored to determine the need for reconstructive and other forms of intervention. The chronic form or Otitis Media in most cases requires the use of:

 

  • Reconstruction of the perforated eardrum (tympanoplasty)

  • Clearing the mastoid air cells of infection (mastoidectomy)

  • Removing the growth of excess tissue in the ear canal (removal of cholesteatoma)

 

In terms of treatment, Otitis Media is generally

approached with a strategy built around the

use of antibiotic therapy.

Should the condition, however, not respond to antibiotics,

it may be  decided to take a surgical route in treatment. 

Surgery Myringotomy is performed which entails the

passing of a needle through the tympanic membrane

aimed at removing effusion. Once the needle is in

place, a tube is placed though the opening –

as a replacement (temporary) for the

Eustachian Tube in functioning as an

equaliser of pressure in the middle ear.

The following referenced diagram depicts

the surgical process:

 

 

 

ACOUSTIC TRAUMA

 

Causes and Onset Acoustic trauma is a condition of sensorineural hearing loss characterised by damage to the hearing mechanisms within the inner ear. This damage is generally caused by sound wave events and is very common – second only in occurrence to age related hearing loss.

 

Some examples of damaging causing events:

 

  • An explosion near the ear

  • Gunshots

  • Long-term exposure to loud noises (such as loud music or machinery)

 

From the examples provided above, one may easily deduce that the condition is entirely preventable and certainly is linked to one’s environmental factors. These factors are in most cases linked to occupation, yet the condition can affect people across the spectrum of demographics. Hearing loss resultant from trauma could be permanent or indeed temporary. Should the hearing loss be temporary, it is termed temporary threshold shift or TTS – whereas a permanent damage is described as permanent threshold shift or PTS. Acoustic trauma and the resultant hearing loss is functionally explained as the over-stimulation of hair cells and supporting structures. The damage to these hair cells specifically the outer placed cells results in hearing distortion – basically, the auditory stimulus is distorted and the process of decoding derailed.

 

There is a distinction between the mechanics of permanent and gradual hearing loss as a result of trauma. In permanent hearing loss – as a result of singular events (excessive sound) the organ of Corti is destroyed by the pressure waves. Gradual hearing loss, however, targets the outer hair cells in the cochlea through repeated onslaught, which can lead to inner hair cell loss over time.

 

Beyond the mechanics of damage, we must also regard the general symptoms of noised induced hearing loss:

 

  • Partial hearing loss

  • Hearing loss involving high-pitched sounds

  • Hearing loss slowly getting worse

  • Ringing in the ears (tinnitus)

Medical Findings

 

A physician will in all likelihood suspect noise induced hearing loss as a result of medical history provided by the patient (did he/she experience an acoustically traumatic event). In cases where the medical history does show a possible risk for hearing loss, there are many tests that can be performed by an audiologist. This does, however, not imply that the physician does not have his own battery of test which can be performed (including CT scan and MRI).

 

Audiological Findings

 

A patient will in cases of suspected hearing loss due to trauma be referred to an audiologist. Should this referral be performed, a full audiological evaluation will be done. The tests that an audiologist can perform are well suited to the investigation of the hearing loss in that a wide spectrum of frequencies can be tested. It is also important that the audiologist seeks answers in terms of whether the loss is sensorineural, conductive or indeed mixed. Answers to the typology of loss can be provided by measuring air and bone conduction in the patient. Audiologists furthermore, have the ability to test the whole spectrum of the acoustic process (speech and hearing) and can determine which elements of the process have been affected. A characteristic sign of Noise Induced Hearing Loss is a configuration of the audiogram with a high frequency loss greater than 3000Hz which peaks around 4000Hz with some recovery in the higher frequencies.

 

Prognosis and Treatment Options

 

The prognosis for noise induced hearing loss is pretty grim especially the permanent variation of the condition. Currently, the treatment of permanent noise-induced hearing loss is limited to hearing amplification and counselling. Hearing aids can amplify sounds but, despite technologic advances, often cannot fully correct problems of speech discrimination. In the case of temporary hearing loss, there seems to be an approach of wait and see – in hopes of the return to normal thresholds.

 

 

 

PRESBYACUSIS

 

Causes and Onset

 

Presbyacusis is the decline in hearing loss due to the aging process and by far the most common cause of hearing loss. It increases with age, with around a quarter of people aged between 65 and 75 and half of those over 75 suffering from it. The distinction between gradual noise induced hearing loss and age related hearing loss lies in the fact that no specific event based acoustic trauma is attributable as cause to age related hearing loss. It follows then that the hearing loss is also bilateral and symmetrical (both ears are affected) and that the effects are experienced as being progressive over time.

 

There are four types of Presbyacusis:

 

  • Sensory Presbyacusis: This refers to a rapidly sloping, slowly progressive high frequency hearing loss

  • Neural Presbyacusis: This refers to big decrease in speech discrimination and onset hearing loss relatively late in adulthood

  • Metabolic (i.e., strial) Presbyacusis: This condition results from atrophy of the stria vascularis and results in a flat, lowly progressive hearing loss

  • Mechanical (i.e., cochlear conductive) Presbyacusis: This condition results from thickening and secondary stiffening of the basilar membrane of the cochlea. This result in a rapidly decrease in hearing which involves both low and high frequencies

 

Having made the distinction between different types of age related hearing loss as well as providing extensive definitions; one must consider the risk factors that determine the probability of onset. There seems to be consensus that both hereditary and environmental factors play a role in determining the risk for this type of hearing loss. The mix of factors that indicate risk include the patient’s family history, occupational exposure to noise, smoking and possible medical conditions which affect the hearing apparatus. Obviously this form of hearing loss causes considerable cost, frustration and loss of abilities to the patient – all of which is gradual (this is a barrier to early detection and treatment). Common symptoms that hint at this condition include:

 

  • Certain sounds seem overly loud

  • Difficulty hearing things in noisy areas

  • High-pitched sounds such as "s" or "th" are hard to distinguish from one another

  • Men's voices are easier to hear than women’s

  • Other people's voices sound mumbled or slurred

  • Ringing in the ears (Tinnitus)

 

Medical Findings

 

In much the same vein as acoustic trauma related hearing loss, the patient will in all likelihood visit the physician first and be diagnosed through basic tests. Again, the physician will utilise medical history and risk factors to do a first order diagnosis and then rely on the expertise of the audiologist for in depth testing. The physician does, however, have certain tests at his/her disposal such as tuning fork tests (Rinne, Weber, Bing and Schwabach) which can indicate hearing loss. Ultimately though, the patient will be referred to an audiologist for evaluation.

 

Audiological Findings

 

A progressive bilateral symmetrical sensorineural hearing loss occurs. The hearing loss is most marked at higher frequencies.

 

Prognosis and Treatment Options

 

Age related hearing loss shares the same fate as acoustic trauma caused loss in that there is no cure at present available to medical professionals. What is important to note about Presbyacusis is that it is entirely gradual and progressive which implies that over time the effects will become more and more severe. Some interventions do, however, make the condition more manageable to the patient including:

 

  • Hearing aids

  • Telephone amplifiers and other assistive devices

  • Sign language (for those with severe hearing loss)

  • Speech reading (such as lip reading and using visual cues to aid communication)

 

Coupled to the use of hearing aids, certain patients may be deemed fit for a cochlear implant – the sounds are amplified, yet no hearing ability is restored and the condition certainly not reversed.

 

 

 

TINNITUS AND HYPERACUSIS 

 

What is Tinnitus?

 

Tinnitus from the Latin word tinnītus meaning "ringing" is the perception of sound within the human ear (ringing of the ears) when no actual sound is present. Despite the origin of the name, "ringing" is only one of many sounds the person may perceive.

 

Tinnitus is not a disease, but a condition that can result from a wide range of underlying causes. The most common cause is noise-induced hearing loss. Other causes include: neurological damage (multiple sclerosis), ear infections, oxidative stress, emotional stress, foreign objects in the ear, nasal allergies that prevent (or induce) fluid drain, wax build-up, and exposure to loud sounds. Withdrawal from benzodiazepines may cause tinnitus as well. Tinnitus may be an accompaniment of sensorineural hearing loss or congenital hearing loss, or it may be observed as a side effect of certain medications (ototoxic tinnitus).

 

Tinnitus is usually a subjective phenomenon, such that it cannot be objectively measured. The condition is often rated clinically on a simple scale from "slight" to "catastrophic" according to the difficulties it imposes, such as interference with sleep, quiet activities, and normal daily activities.

 

If there is an underlying cause, treating it may lead to improvements. Otherwise typically management involves tinnitus retraining therapy. As of 2013, there are no effective medications. It is common, affecting about 10-15% of people. Most however tolerate it well with it being a significant problem only in 1-2% of people.

 

Prevention

 

Tinnitus and hearing loss can be permanent conditions. Prolonged exposure to sound or noise levels as low as 70 dB can result in damage to hearing (see noise health effects). This can lead to tinnitus. Ear plugs can help with prevention.

 

Avoid potentially ototoxic medicines. The ototoxicity of multiple medicines can have a cumulative effect, and can increase the damage done by noise. If ototoxic medications must be administered, close attention by the physician to prescription details, such as dose and dosage interval, can reduce the damage done.

 

Treatment and Prognosis

 

There is some evidence that Cognitive behavioural therapy (CBT), which can be delivered via the internet or in person, can decrease the amount of stress those with tinnitus feel. However, it has no effect on tinnitus volume and the beneficial effects may not persist once counselling has ended. These benefits appear to be independent of any effect on depression or anxiety in an individual. Relaxation techniques may also be useful.

 

Recent research has indicated that Clonazepam may have a reductive effect on tinnitus loudness, though more research is required. There is not enough evidence to determine if antidepressants or acamprosate is useful. Anticonvulsants have not been found to be useful. The use of sound therapy by either hearing aids or tinnitus maskers is usual practice but poorly supported by evidence. There is some tentative evidence supporting tinnitus retraining therapy. There is little evidence supporting the use of transcranial magnetic stimulation. Ginkgo biloba does not appear to be effective. Tentative evidence supports zinc supplementation and in those with sleep problems, melatonin.

 

Most people with tinnitus get used to it. A small percentage remains significantly bothered.

 

 

 

TYPES OF PAEDIATRIC HEARING LOSS

 

There are two primary categories of hearing loss in children, congenital (present at birth) and acquired (occurring after birth). These hearing losses may be sensorineural, conductive or mixed.

 

Possible Causes of Congenital Hearing Loss may include the following -

 

  • Infections during pregnancy (German measles, toxoplasmosis and cytomegolavirus)

  • Ototoxic medication used during pregnancy

  • Birth complications such as serious infection present at birth, such as toxoplasmosis, herpes, rubella or cytomegolavirus; baby required neonatal intensive care; birth weight less than 3 lbs.; unusual appearance of baby's head, face or ears; baby required blood transfusion; or drugs used for respiratory life-sustaining measures on premature infant.

  • Disorder of the brain or nervous system

  • Genetic syndromes, such as Ushers, Down's and Waardenburg's syndromes

  • Family history of hearing loss

 

Possible Causes of Acquired Hearing Loss

 

  • Untreated middle-ear infections

  • Other infections, such as meningitis, mumps, measles or whooping cough

  • Perforation of the eardrum

  • Excessive noise, such as fireworks or loud music

  • Serious injury to the head

  • Ototoxic medication

 

Frequently, hearing loss in young children is conductive (temporary), and caused by earwax or middle-ear infections. Many children with temporary hearing loss can have their hearing restored through medical treatment or minor surgery.

 

Some children have sensorineural hearing loss, which is permanent. Most of these children have some usable hearing, and children as young as four weeks of age can be fitted with hearing aids.