What is sensorineural hearing loss?

Sensorineural hearing loss (SNHL) happens when the sensitive, hair-like cells within the cochlea (inner ear) or the hearing nerve become damaged. These hairs convert sound wave vibrations into neural signals for the auditory nerve to carry to your brain. This affects the pathway needed for the brain to interpret sound signals, and therefore how well we can hear. Sensorineural hearing loss occurs when one, or both, of these functions of the inner ear, are damaged.

Sensorineural hearing loss can vary from mild to severe loss, depending on the degree of damage to the inner ear:

  • Mild — unable to hear sounds quieter than 25 decibels for adults and 15 decibels for children
  • Moderate — unable to hear sounds between 41-55 decibels
  • Severe — a loss of hearing of more than 71 decibels

There are also different types of sensorineural hearing loss. These include:

  • Bilateral SNHL — hearing loss in both ears
  • Unilateral SNHL — hearing loss in one ear
  • Asymmetrical SNHL — hearing loss in both ears, but one is worse than the other

What is sudden sensorineural hearing loss?

Sudden sensorineural hearing loss (SSHL) is a rapid, unexplained loss of hearing. When there is something wrong with the sensory organs of the inner ear, sudden hearing loss can occur. Only 10-15% of people with sudden sensorineural hearing loss have an identifiable cause.1

Symptoms of sensorineural hearing loss

Symptoms of sensorineural hearing loss can vary depending on the underlying cause, and the severity of hearing loss. Some common symptoms include:

  • Difficulty hearing high-pitched sounds
  • Difficulty understanding what is being said when having conversations in speech, especially with background noise and particularly children’s/female voices
  • Trouble hearing the television or radio and having to increase the volume
  • Tinnitus — a buzzing or ringing sound in the ear
  • Dizziness
  • Balance problems
  • Ménières disease
  • You can’t differentiate between certain sounds (like ‘s’ or ‘th’ sounds)

Different noises vibrate at different frequencies, and these are what our ears pick up for our brain to process as sound. This means that if your ears aren’t picking up certain vibrations because of hearing loss, there may be certain types of sound you might not be able to hear as well as others.

Symptoms of high-frequency hearing loss

The symptoms of this can include not being able to hear:   

  • High pitched voices of children, women, and birdsong
  • Sounds like ‘s’, ‘sh’, ‘f’, ‘v’, ‘th’, p
  • Certain subtle sounds of timers, clocks, car signal and ovens

Symptoms of low-frequency hearing loss 

This is a less common form of hearing loss and the symptoms are opposite to high-frequency loss. These can include not being able to hear:   

  • Deep voices, such as men’s voices
  • Low-pitched music or natural sounds, like the wind
  • Phone conversations (but a face-to-face one is easier)

Causes of sensorineural hearing loss

Sensorineural hearing loss can be caused by a variety of factors, including genetics, exposure to loud noise, infection or certain medications. It can be treated with hearing aids or cochlear implants, but it is often permanent. Some common causes include:

Ageing

Presbycusis, or hearing loss due to ageing, is a common type of sensorineural hearing loss. If you are over 60 years old and have hearing problems, there is a chance you could have presbycusis.

Presbycusis reduces the high-frequency hearing of those affected — so if you’ve noticed your hearing isn’t quite what it used to be, make sure you see an audiologist. They’ll check your hearing, and will be able to recommend treatment to help improve your hearing and get you back to normal.

Loud noises

The most common cause of sensorineural hearing loss is loud noises directly damage your cochlear structures. You can avoid being affected by loud noises by protecting your ears.

Ménière’s disease

Ménière’s disease is an inner ear condition that is typically associated with tinnitus (ringing noise inside the ear), vertigo (room spinning), and hearing loss. This condition can cause hearing loss to come and go as it progresses.

Otosclerosis

Otosclerosis, or abnormal bone growth inside the ear, is a common cause of hearing loss in young people. It begins in a person’s 20s with mild hearing loss that progresses with age.

Certain conditions, such as diabetes or conditions that involve your blood pressure, can also put you at a higher risk of developing sensorineural hearing loss.

Infections

Viral infections can cause what is known as sudden sensorineural hearing loss (SSHL). These cases require urgent medical attention and are treated with a class of steroids known as corticosteroids. Viral infections during pregnancy, such as Cytomegalovirus, could also cause hearing loss in the child.

Brain injury or head trauma

Trauma can cause the inner ear to rupture and leak its fluid, which can impact hearing. It is sometimes possible to repair this damage through emergency surgery

Ototoxic drug

These types of drugs are damaging to the ear and can cause varying degrees of hearing loss, from ‘mild’ to ’profound’. If you have been advised to take any ototoxic drug, be careful not to take more than the recommended dosage and speak to your GP about any side effects.2

Genetics 

Numerous genetic conditions are associated with hearing loss, with severity ranging from ‘mild’ to complete deafness. It is believed that there are over 400 types of genetic hearing loss.3

Malformations of the inner ear 

The inner ear is where you’ll find the organ for hearing (known as the cochlea). This is what helps to send sound signals to our brains to allow us to hear. Malformations in this area result in ‘severe’ to ‘profound’ hearing loss, usually in both ears. Cochlear implants may be recommended as treatment.

How is sensorineural hearing loss diagnosed?

A physical exam will be conducted to determine whether you have sensorineural hearing or conductive hearing loss. Your doctor will look at a number of factors, including earwax buildup, inflammation, damage to the inner ear and foreign bodies.

Audiogram

An audiogram is a graph showing the sounds a person can hear at various pitches and frequencies. During the test, you’ll be given headphones, where a series of different frequencies and volumes will be played. You will indicate when you can hear each tone by raising your hand or pressing a button. 

Weber test

The Weber test is performed by striking a 512 Hz tuning fork and placing the base of the fork on the middle of your forehead, or front teeth. You will then be asked to indicate which ear you hear the tone louder in. If the sound is louder in the unaffected ear, hearing loss is most likely to be sensorineural. 

Rinne test

The Rinne test is used to determine the relative ability of how well you can hear sound via air conduction and bone conduction. The test is performed by placing a 512 Hz tuning fork on your mastoid bone and then holding the fork next to the ear. You will be asked if the sound is louder when the fork is on the bone, or next to the ear. 

A positive Rinne test is when the sound is louder when heard through the air than by bone conduction. A negative test is when the sound is louder through bone conduction, rather than through the air, and this is indicative of conductive hearing loss.

Treatment for sensorineural hearing loss

Treatment for sensorineural hearing loss typically involves the use of hearing aids or cochlear implants. An audiologist will be able to recommend the best option for you, but the most common treatment is wearing hearing aids. 

When your hearing loss is more profound, you may be referred to a specialist to discuss the option of cochlear implants to help improve your hearing. If sudden hearing loss has been caused by infection or an ototoxic drug, you should see your GP first. Unlike gradual loss or congenital causes, sudden onset hearing loss can be reversed — as long as it’s identified  and treated immediately.

Hearing aids

Hearing aids may be worn to amplify sounds and improve communication. Hearing aids can help to alleviate specific hearing loss symptoms. A hearing aid fitting takes around 45 minutes, during which time your audiologist will check the health of your ears and show you how to use your hearing aids. 

Browse our range of hearing aids

Cochlear implants

Cochlear implants can help people with severe sensorineural hearing loss to hear sounds and improve communication. Cochlear implants are devices surgically implanted into the ear. They convert sound waves into electrical impulses, stimulating the inner ear nerve cells and sending information to the brain.

Corticosteroid (oral or injection)

For sudden sensorineural hearing loss, your doctor may prescribe treatment with steroids to alleviate the hearing loss. These come in two forms: tablets or an injection through the eardrum (intratympanic injection).

Oral steroid is usually the first-line therapy, while the steroid injection would be the choice when the oral steroid alone is not sufficient. 

Studies have shown both the oral and injection forms of steroid therapy are equally effective in treating hearing loss.

Hearing loss information hub
Causes of hearing loss
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Symptoms of hearing loss
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Conductive hearing loss
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References
  1. Hearing Loss Association of America https://www.hearingloss.org/hearing-help/hearing-loss-basics/sudden-deafness/
  2. Bisht M, & Bist S.S., Ototoxicity: the hidden menace, Indian J Otolaryngol, Head Neck Surg. 2011;63(3):255-9
  3. Shearer A.E., Hildebrand M.S., Smith R.J.H., ‘Hereditary Hearing Loss and Deafness Overview’, in Adam M.P., Ardinger H.H., Pagon R.A., et al (ed), GeneReviews [internet], Seattle (WA): University of Washington, Seattle; 14 Feb 1999 [updated 27 July 2017], https://www.ncbi.nlm.nih.gov/b... (accessed 16 July 2020)