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Hearing Defects

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Hearing Defects

Auditory or hearing defects cause partial or total hearing impairment. Hearing loss is defined as the reduced ability to perceive sounds. The severity or degree of hearing loss is categorised according to the increase in the intensity of sound above the normal level required for the person to detect it.

Types of hearing problems

There are three types of hearing loss: conductive, mixed, and sensorineural. Conductive hearing loss is associated with sound problems in the outer or middle ear, sensorineural hearing loss with damage to the auditory nerve itself, and mixed hearing loss has both conductive and sensorineural elements.

Common problems may include blockage in the inner ear, eardrum deformation, fluid in the eardrum, etc.

Ageing, injury, noise exposure, genetics, and viral diseases are the most common causes of hearing loss.

Congenital hearing defects and the cardiovascular system

Congenital hearing defects are caused by congenital cardiovascular diseases associated with structural defects of the heart that are almost always present from birth. These structural defects usually involve the walls, valves, arteries, or veins near the heart. Some congenital cardiovascular diseases cause hearing defects, as they reduce blood flow in the body, including to the ear, which damages different parts of the auditory system.

These types of hearing loss are permanent but can be managed using amplification devices such as hearing aids.

Anatomical hearing defects

Around 80% per cent of congenital hearing loss is caused by defects related to the structure of membranes in the inner ear and, more specifically, the cochlea. A minority of congenital hearing loss is caused by the deformation of the bony labyrinth in the inner ear. If the problem causing hearing defects is the structure of the cochlea, cochlear implants or hearing aids are used for treatment, as shown in figure 1.

Hearing Defects, Cochlear implants, StudySmarterFigure 1. Cochlear implant.

Meniere’s disease

Meniere’s disease is related to the pressure on the inner ear. Some causes of Meniere’s disease include fluid drainage, abnormal immune responses, or viral infections. The disease usually only affects one ear but can affect both. It is a progressive disease that can cause either temporary or permanent hearing loss that worsens over time. It also results in sudden side effects like a spinning sensation and ringing noises in the ear.

Treatments include hearing aids, pressure therapy, and surgery to reduce the level of fluid in the inner ear to relieve the pressure.

Acoustic neuroma

An acoustic neuroma is a progressive, noncancerous tumour that is located on the nerve connecting the inner ear and the brain. The tumour may apply pressure on the nerve, which may lead to hearing loss, balance problems, or tinnitus, which is a ringing noise in the ear.

If the tumour is projected to cause hearing problems, it is usually surgically removed.

Hearing Defects: Down syndrome

Down syndrome is caused when a person is born with an extra copy of the 21st chromosome. This condition sometimes causes heart defects, which may also affect hearing. In the majority of adults with down syndrome, the condition causes conductive hearing loss due to narrow ear canals without affecting the heart. People with down syndrome, therefore, usually have regular hearing tests and sometimes use hearing aids.

Vestibular neuritis and labyrinthitis

Vestibular neuritis occurs when the nerve responsible for sending motion and balance signals to the brain is inflamed or swollen. Labyrinthitis, on the other hand, is the result of the labyrinth, a spiral-shaped canal filled with fluid in the inner ear, being inflamed. Both conditions are usually caused by a viral infection. Labyrinthitis affects both hearing and balance and is treated by physical therapy to help restore balance and treat the underlying viral condition.

Benign paroxysmal positional vertigo (BPPV)

This is a very common form of vertigo caused by a head injury or by debris collected in the inner ear at the semi-circular canals. Vertigo disease has side effects such as dizziness and head spinning. Treatments include the canal repositioning technique, which moves particles from the semi-circular canals to the vestibule, a larger area that can absorb them. The particles can also be moved surgically, using a plug to block fluid flow in the area.

Superior semi-circular canal dehiscence (SSCD)

This condition is relatively rare and occurs where the bony area covering the semi-circular canal is either absent or deformed (see figure 2). Symptoms include hearing loss, balance problems, and dizziness. This condition can be treated surgically to fill or reform the area of the missing bone.

Hearing Defects, Superior semi-circular canal, StudySmarterFigure 2. Superior semi-circular canal.

Hearing Defects: Signs of hearing loss

Hearing loss is usually progressive, and several symptoms or signs may identify when someone is experiencing it. The first sign of hearing loss is difficulty hearing weak sounds. This may be due to age-related hearing loss. Another common sign is the inability to hear high-pitched sounds, such as birdsong. The inability to have conversations in crowded places due to being unable to differentiate speech may also indicate hearing loss.

Hearing Defects: Hearing loss tests

Hearing loss tests are used to identify hearing conditions for either hearing loss or balance problems. When structural defects are causing hearing problems, usually imaging is used for proper diagnoses such as computed tomography, CT scans, magnetic resonance imaging, or MRI. For hearing issues, the following tests are performed:

  • Pure-tone test or audiometry test: different sounds are played through headphones to identify the quietest sounds that can be heard at different frequencies or pitches.
  • Tuning fork tests: a two-pronged metal fork is positioned behind the ear or on the head. The fork is struck so that a sound is produced. This is used to identify whether one specific ear is having problems or whether there is hearing loss in both ears. It can also show the type of hearing loss, i.e., whether it is conductive or sensorineural.

Balance testing is more complex, as it involves a series of examinations to properly diagnose one of the following underlying conditions:

  • Vestibular testing: this includes a series of tests examining the vestibular system using electronystagmography or videonystagmography. Both of these tests record eye movements, which provide critical information for the function of the inner ear. Electronystagmography is a test to determine if vertigo is present in the patient. Electrodes are positioned around the eyes to record electrical activity. Videonystagmography measures involuntary eye movement. Depending on the frequency of these movements balancing problems can be identified.
  • Computerised dynamic posturography: this test evaluates three different types of senses vestibular, somatosensory, and vision. This test, combined with the results of others, allows identifying which of the three senses is the problem to find a targeted treatment. The process includes standing barefoot and secured with a safety harness to test balance in various circumstances.
  • Vestibular-evoked myogenic potential: this test identifies how the patient is responding to sound and whether the vestibular nerves are working well. Electrodes are placed on the forehead and neck to record electric activity. This is done by applying a repetitive sound stimulus to one ear and then averaging the reaction of the muscle activity. It is also done for both ears to see any abnormal muscle reaction in the ear.
  • Video head impulse testing: this test identifies the function of the semi-circular canals and whether they work well enough. Special goggles are worn, and the patient must follow a target with their eyes to record specific movements that stimulate specific parts of the inner ear to identify whether there is a problem with the inner ear.

Hearing loss severity

The severity of the hearing loss is classified based on the range of frequencies that can be heard compared to what can be heard by a person with a normal hearing range. Sound is measured in decibels, a measuring unit of loudness. The larger the decibel, the louder the sound. If the patient can only hear at a large number of decibels, they cannot hear quiet sounds and thus are experiencing some hearing loss.

  • Mild hearing loss: only sounds above 30 dB can be heard.
  • Moderate hearing loss: only sounds above 50 dB can be heard.
  • Severe hearing loss: only sounds above 70 dB can be heard.

See also the table below.

Degree of hearing loss
Hearing loss range (dB HL)
Normal
–10 to 15
Slight
16 to 25
Mild
26 to 40
Moderate
41 to 55
Moderate to Severe56 to 70
Severe
71 to 90
Profound
91+

Hearing Defects - Key takeaways

  • Hearing loss can be divided into three types: cognitive, sensorineural, and mixed.

  • There are a variety of factors that can cause hearing defects or hearing loss.

  • Structural defects can be tested using a CT scan or MRI, but there are also some other physical tests to identify hearing problems.

  • Hearing loss is classified into categories depending on the severity.

Frequently Asked Questions about Hearing Defects

Some common hearing problems are Meniere’s disease, otosclerosis, presbycusis, acoustic neuroma, and autoimmune inner ear disease.

Yes, it does in the majority of people.

Inability to hear high-pitched sounds, inability to hear weak sounds, and being unable to have conversations in a loud environment.

Defects that cause partial or total hearing impairment.

Mixed, conductive, and sensorineural hearing loss.

Final Hearing Defects Quiz

Question

What are hearing defects?

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Answer

They are defects that cause partial or total hearing impairment. 

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Question

What are the main types of hearing loss? 

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Answer

Sensorineural, conductive, and mixed.

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Question

What is sensorineural hearing loss?

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Answer

It is the hearing loss associated with damage to the tiny hair located in the cochlea, also called cilia. 

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Question

List the most common hearing defects.

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Answer

Ageing, injuries, noise exposure, genetics, viral diseases.

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Question

What is vestibular neuritis and labyrinthitis?

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Answer

Vestibular neuritis occurs when the cranial nerve is inflamed or swollen. Labyrinthitis occurs when the labyrinth is filled with fluid and the in the inner ear gets inflamed. 

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Question

What  is BPPV?

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Answer

It is the most common form of vertigo caused from injury or dust in the inner ear.

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Question

What is the treatment for acoustic neuroma?

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Answer

Surgery.

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Question

What are the most common signs of hearing loss?

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Answer

Difficulty hearing consonants and high-pitched sounds, and to have conversations in loud environments.

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Question

What are the two types of hearing loss tests ? 

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Answer

Pure-tone and tuning fork test.

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Question

What is vestibular testing? 

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Answer

It is a test used to examine the extent of functionality of the vestibular system using electronystagmography or videonystagmography.

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Question

What are the different levels of hearing loss? 

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Answer

Normal, slight, mild, moderate, severe, and profound.

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Question

What level of hearing loss is a loss in the range of 26-40 dB?

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Answer

Mild.

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Question

What level of hearing loss is a loss in the range of -10 to 15?

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Answer

Normal.

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Question

Which of the following is true?

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Answer

The highest dB hearing loss range indicates the most severe hearing loss.

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Question

Which of the following is not true?

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Answer

The treatment of hearing loss caused by down syndrome defect is surgical.

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Question

List some hearing defects. 

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Answer

Meniere’s disease, anatomical defects, congenital hearing defect, SSCD, BPPV, etc.

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