Types of Hearing Loss

Suffering From Hearing Loss?

What are the types of hearing loss?

There are three main types of hearing loss. In the last few years a fourth type of hearing loss called auditory processing disorder has become recognised. We will discuss it here, but first, let’s take a look at the three main types of hearing loss are:

  • Sensorineural hearing loss
  • Conductive hearing loss
  • Mixed hearing loss

Sensorineural Hearing Loss

Sensorineural hearing loss is a problem of the hearing nerves of the inner ear or the nerve of hearing. Damage occurs to the sensory structures in the cochlea and auditory nerve. These hair cells are the nerves that send the electrical signals to the brain that the auditory cortex recognises as sound. Damage alters the neural code reaching the brain. Most types of sensorineural hearing loss are permanent.

Sensorineural hearing loss can have many causes, it can be genetic, caused by the aging process, diseases, exposure to loud noises, certain kinds of chemicals and medications and finally head injury. Diagnosis of sensorineural hearing loss
Sensorineural hearing loss is diagnosed through Audiometry and Oto-acoustic emissions. A healthy cochlea emits measurable sounds when stimulated. If the sounds are absent or reduced, it suggests damage to the outer hair cells.

Treatment of sensorineural hearing loss

There are no medical treatments for typical sensorineural hearing loss. The only treatment available is using hearing aids or cochlear implants. Hearing aids will help to reduce the impact of the hearing loss on your life. Sudden hearing loss is often treated with steroids and pressure therapy.

Auditory Processing Disorder

Auditory Processing DisorderWithout the brain, it is impossible to hear. In some cases, more often in smaller children, the auditory portion of the brain does not properly utilise the signals delivered by the ear. Called an auditory processing disorder (APD). Our awareness of Auditory Processing Disorder (APD) has increased over the last few years. APD occurs when there is little or no hearing problems but the brain has problems processing the information contained in sound, such as understanding speech and working out where sounds are coming from. Many people who have APD have little or no hearing loss. At this stage, APD is little understood and there are no definitive treatment options. There are sound training options that seems to help train the brain to better process sound. Hearing aids are not an ideal solution in cases of APD, however, some people have reported improvements.

Diagnosis: Auditory processing disorders are diagnosed through a serious of audio tests. These evaluate the ability to understand in difficult situations, such as in the presence of competing sounds. Testing is time-intensive and may be accompanied by electrophysiological tests such as the Auditory Brain Stem Responses (ABR).

Treatment: Auditory processing disorders are also treated by utilising effective communication strategies. For children with APD preferential seating at school is required. In some listening situations, listening devices may be helpful.

VIIIth Nerve Tumor

Eustachian Tube Dysfunction
Once the auditory stimulus makes its way through the ear, it travels along the VIIIth cranial nerve to the brainstem and then up to the brain for processing. In some instances the ear may be healthy, but a significant hearing loss is caused by damage to the nerve itself. A tumour on the VIII the cranial nerve can cause this type of hearing loss

Diagnosis: Auditory brainstem response testing (ABR) is used to rule out the presence of an VIIIth nerve tumor. However, an MRI is the gold standard. Suspicion of an acoustic tumor occurs when it manifests itself as a unilateral hearing loss, often accompanied by tinnitus and dizziness

Treatment: VIIIth nerve tumors are slow-growing and benign. Depending on the size, a physician may choose to simply monitor its growth. Tumours are removed surgically. This carries significant risk to the auditory nerve. Hearing aids may also be helpful.

Conductive Hearing Loss

Conductive Hearing Loss is a problem of the middle or outer ear. More often than not, it occurs when there is a problem in the middle ear which interferes with the passing sound to the cochlea (inner ear). Conductive hearing loss is caused by something as simple as too much ear wax. The problem is also caused by ear infections, punctured eardrums, abnormal bone growth in the middle ear (otosclerosis). It is most common in children and because of problems in delivery of healthcare in indigenous populations.

Often conductive hearing loss can be medically treated. That treatment can vary from simple antibiotics to different surgeries. If a person does not want to undergo surgery, several types of hearing technology can be used to treat the problem. Depending on the state of the outer ear, traditional hearing aids can help. If the state of the outer ear is such that traditional hearing aids are not the best option, well then bone conduction hearing aids and bone anchored hearing aids (BAHA) are the best options.

Eustachian Tube Dysfunction

Tympanic Membrane Perforation
The eustachian tube connects the space behind the eardrum to back of the throat. It’s purpose is to prevent the build up of air pressure behind the ear. The tube is typically closed and opens with yawning and swallowing. Eustachian tube dysfunction is a condition where that tube either doesn’t open properly or doesn’t close properly. Causes on Eustachian tube disfunction include a muscle problem or excessive mucous.

Diagnosis: Dysfunction of the eustachian tube is symptomatically diagnosed by a physician. It can be confirmed by an audiologist using an immittance bridge.

Treatment: Eustachian tube dysfunction is often treated by medication designed to decreased the amount of mucous in the tube. Severe cases are usually treated with pressure-equalizing tubes or severing the muscle keeping the eustachian tube open.

Otitis Media

Otitis media is an infection of fluid in the middle ear space. If the eustachian tube remains closed (see Eustachian Tube Dysfunction), significant negative pressure can build up behind the eardrum. That pressure can cause seepage from the surround tissue that may eventually fill the space behind the eardrum. The fluid prevents proper transmission of sound and can become infected if not drained.

Diagnosis: Otoscopy and tympanometry is used to diagnose otitis media. A tympanogram tests the eardrums flexibility. If fluid is behind the eardrum its flexibility is significantly decreased.

Treatment: Otitis media is often treated with antibiotics. This treats the infection and alleviates the pain. However, antibiotics do not always permit proper drainage of the trapped fluid. In severe cases, an ENT surgeon will drain the fluid by placing a small incision in the eardrum.

Otosclerosis

Otosclerosis is a condition where movement of the middle ear bones is impeded. The footplate of the stapes (or stirrup) can become fixated, which prevents the proper transmission of sound. Otosclerosis occurs gradually and is linked to family history.

Diagnosis: Otosclerosis is diagnosed using tympanometry and the audiogram. Fixation of the stapes effects air and bone conduction thresholds differently. This is also indicated by a particular shape on the audiogram.

Treatment: Otosclerosis often warrants replacement of the stapes through surgery. In cases surgery may be contraindicated. Hearing aids can be very effective to overcome the conductive component of the hearing loss.

Tympanic Membrane Perforation

The tympanic membrane, also known as the eardrum, vibrates when sound hits it. It is made up of three layers of skin and is water-tight. A hole in the eardrum prevents proper vibration and is usually perceived as a mild hearing loss.

Diagnosis: A tympanic perforation can be seen by an otoscopic examination. It is confirmed using Tympanometry that measures middle ear canal volume, pressure and mobility.

Treatment: Perforations often heal on their own, but not always. A Tympanoplasty, or patching of the perforation is often performed by an ENT surgeon.

Cerumen (Ear Wax) Impaction

Cerumen (ear wax) is found in the outer third of the ear canal. It moisturizes the ear, repels insects, and traps dust. The hair of the ear canal naturally push the wax outward. Excessive hair, a small ear canal, or the use of Q-tips can disrupt this natural cleaning process and cause the wax to build up. If it completely blocks the ear canal, sound will not be able to get to the eardrum. Hearing loss caused by cerumen can occurs suddenly. It is easily treated.

Diagnosis: An examination with an otoscope will reveal cerumen (instead of an eardrum). Tympanometry is also used to confirm that the wax is impacted.

Treatment: Use of a softening agent, such as Waxsol or Audiclean can help prior to removall. Cerumen can be also be removed using a curette (small spoon), suction system, or flushing with water.

Mixed Hearing Loss

A Mixed Hearing Loss occurs when both conductive hearing Loss and sensorineural hearing loss are present. Mixed hearing loss is relatively rare in the general population. The sensorineural part of the hearing loss is permanent, however, the conductive part can be permanent or temporary.

In general, the treatment for this type of hearing loss is hearing aids. If there is a good possibility for treatment of the conductive element to be successful, well then it is worthwhile to consider treatment.

However, even if the treatment is effective, the sensorineural part of the hearing loss will remain unchanged.