What is Sensorineural Hearing Loss?
Hearing loss, a prevalent issue, often requires specialist advice from an ear, nose, and throat doctor, also known as an otolaryngologist. There are two main types of hearing loss: conductive and sensorineural. Sensorineural hearing loss, often shortened to SNHL, is the most frequent type, making up most cases of hearing loss. SNHL refers to any kind of hearing loss caused by issues with the inner ear, the hearing nerve, or the central nervous system.
When a person experiences newly developed hearing loss, a thorough examination should be done by a team of specialists to figure out the cause. This team might include an otolaryngologist, an audiologist who specializes in hearing and balance disorders, a radiologist who operates imaging equipment for diagnosis, and a speech/language therapist who can help manage communication difficulties.
What Causes Sensorineural Hearing Loss?
The most common reasons for sensorineural hearing loss, a type of hearing loss that occurs when there’s damage to the inner ear or the nerve pathways from the inner ear to the brain, include:
* Congenital – these are hearing loss conditions you’re born with. Syndromic means they’re grouped with other medical conditions, while nonsyndromic means they stand alone.
* Presbycusis – this is age-related hearing loss, and it’s fairly common amongst older adults.
* Noise-induced hearing loss – this can happen after exposure to very loud noises.
* Head injury – any injury to the head can potentially cause hearing loss.
* Meniere’s disease – a disorder related to the inner ear that leads to dizziness and ringing in the ear.
* Ototoxicity – this refers to damage caused by certain medications and substances like aminoglycosides, loop diuretics, and some chemotherapeutic agents which are harmful to the ear or nerve supply to the ear.
* Systemic conditions – certain diseases that affect the whole body, like meningitis or diabetes, may also affect hearing.
* Vestibular schwannoma – a benign, often slow-growing tumor in the inner ear.
* Others – other causes include autoimmune disorders, barotrauma (injury caused by changes in air or water pressure), and perilymphatic fistula (an abnormal opening between the inner ear and the middle ear).
Risk Factors and Frequency for Sensorineural Hearing Loss
Sudden sensorineural hearing loss, also known as SNHL, affects between 5 to 27 out of every 100,000 people in the US each year. This results in around 66,000 new cases annually. However, different studies have different standards for what constitutes hearing loss, which makes it hard to agree on the specifics of how presbycusis, or age-related hearing loss, affects people. With presbycusis, the number of people affected tends to double every 10 years from the second through to the seventh decade of life and is almost universal after the eighth decade.
Another major cause of hearing loss in adults is noise-induced hearing loss, which is responsible for an estimated 16% of disabling hearing loss cases worldwide. Despite laws in most developed countries meant to prevent this, it still remains a common work-related disease.
- Sudden sensorineural hearing loss affects 5 to 27 out of every 100,000 people each year in the US.
- This results in around 66,000 new cases annually.
- Different studies have different measures for hearing loss, creating a lack of agreement on the specifics of presbycusis, or age-related hearing loss.
- In presbycusis, the prevalence doubles every 10 years from the second through the seventh decade and is nearly universal past the eighth decade of life.
- Noise-induced hearing loss (NIHL) is responsible for about 16% of disabling hearing loss in adult populations worldwide, and remains a common occupational problem despite existing laws to prevent it.
The type of hearing loss that is present from birth, also known as congenital hearing loss, is usually sensorineural and can happen due to various reasons. When prenatal care is thorough, infection-related causes like cytomegalovirus infection are rare and the most common causes are genetic. There are many genetic syndromes that include hearing loss as a symptom, and sensorineural hearing loss appearing in childhood calls for a detailed examination.
Signs and Symptoms of Sensorineural Hearing Loss
If someone is showing signs of Sensorineural Hearing Loss (SNHL), it’s crucial to understand their full health history. Key information includes when their symptoms started, if it affects both ears, how quickly it developed, if symptoms come and go, and related symptoms like ringing in the ears, feeling like their ear is full, balance problems, or dizziness. It’s also important to know what their hearing was like before, to understand whether this is a new problem or an existing one that’s getting worse. Previously having ear surgery, exposure to noisy environments, head injuries, sudden change in air pressure, or use of certain drugs known to harm the ear might be relevant.
Patients with ‘presbycusis’ (age-related hearing loss) tend to have a history of their hearing gradually getting worse. You might notice that they’ve been turning up the volume on the TV or asking others to speak louder. It’s often the person’s family who notice these changes first. In cases where hearing loss was caused by exposure to loud noise, the person might have a history of being around loud noise at home or work. Understanding a person’s daily life can provide insight into how hearing loss is impacting them and their family. Many people with hearing loss can feel cut off from the world. Activities they used to enjoy, such as watching movies, dining out, or seeing friends and family can become stressful, leading them to avoid these activities.
When a patient comes in with new symptoms of hearing loss, a comprehensive head and neck examination is needed, which includes checking the 12 pairs of nerves that come from the brain, even though these are usually unaffected.
Testing for Sensorineural Hearing Loss
If you’re experiencing loss of hearing, your doctor is going to want to get to the bottom of it. One way to do this is with a complete audiometric evaluation. This test, sometimes referred to as a hearing test, is the best way to get a proper look at your hearing.
Before doing the full hearing test, your doctor may perform some quick and easy tests at your bedside with a tuning fork. This may sound odd, but it’s actually a good way to get some initial information about your hearing.
The two tuning fork tests are known as the Rinne and Weber tests. Both of these are used to figure out if you have a certain type of hearing loss, either conductive (where sound can’t get into your ear properly) or sensorineural (where there is damage to the inner ear or nerves from the ear to the brain).
In the Weber test, the doctor hits a tuning fork and puts it in the center of your forehead. Then you’ll be asked which ear you hear the sound the loudest in. If you have sensorineural hearing loss in one ear, the sound will seem louder in your good ear. If you have conductive hearing loss, you’ll hear the sound louder in the ear with the hearing problem.
The Rinne test involves hitting the tuning fork and placing it on the bone behind your ear, then next to your ear. If it sounds louder when it is next to your ear, it’s a sign that you do not have conductive hearing loss. If it’s louder on the bone, you might have conductive hearing loss.
If these tuning fork tests show a potential problem, you’ll usually be sent for a full hearing test, also known as a pure tone audiogram. This test checks how well you hear sounds at different pitches and volumes, pressing a button each time you hear a sound.
Other tests might also be used. Tympanometry measures how flexible your eardrum is; a more rigid eardrum can be a sign of a middle-ear problem. In otoacoustic emissions testing, a small microphone is put in the ear canal to check for sounds that the ear produces when stimulated by a click or tone. Another test is speech audiometry, which measures your ability to hear and understand speech.
Imaging tests such as a CT scan or MRI of the head might also be used to look for any physical abnormalities that might be causing hearing loss, such as a tumor. Lab tests aren’t typically needed unless your doctor suspects that your hearing loss might be due to an autoimmune disease.
Treatment Options for Sensorineural Hearing Loss
When it comes to sensorineural hearing loss (a type of hearing loss where there’s damage to the inner ear), treatment usually focuses on figuring out the root cause of the issue. If it comes on suddenly and doctors aren’t sure why, they’ll often recommend an MRI scan of the brain to look for any abnormalities. They might also prescribe a course of corticosteroids, a class of drug that helps reduce inflammation.
It’s important to point out that the evidence supporting this treatment is not definitive, and every patient’s situation is unique. So, your doctor will need to consider the potential benefits and drawbacks of this treatment for you individually. That said, if there’s going to be an improvement in hearing, it’s most likely to happen in the first two weeks. After 10 to 14 days, your doctor will probably suggest another hearing test to see how well the treatment is working. If there hasn’t been an improvement, they might suggest a different type of steroid treatment, applied directly inside the ear.
In cases where hearing loss is long-term, hearing aids are usually the go-to treatment. There are many different types available, but the one that’s right for you will depend on your individual circumstances. In older people struggling with hearing loss, hearing aids can be helpful even in mild to moderate cases. Once you have permanent hearing loss, you can’t reverse it, so the sooner you get diagnosed, the earlier you can start treatment and minimize its impact on your life.
One of the most common types of hearing aid sits behind the ear and picks up sounds through a microphone. These sounds are then boosted using electrical energy, before being converted back into sounds and played into your ear. They are widely used, relatively cheap, and easy to replace, but they might not be suitable for everyone, particularly if you have a deformity of the outer ear or ongoing infection.
Another kind of hearing aid, known as a Contralateral Routing of Signal (CROS) hearing aid, works by picking up sounds with a microphone in the ear that has the worst hearing, and then transmitting these sounds wirelessly to your other ear. This approach also can be enhanced by using a second microphone in the better hearing ear for a more balanced sound.
Bone conduction hearing systems, which use vibration to transmit sound directly to the cochlea (inner ear), bypassing the middle ear, are often recommended for those with conductive hearing loss (where sounds can’t get through your outer or middle ear), mixed hearing loss (a combination of conductive and sensorineural hearing loss), or single-sided deafness.
For people with severe hearing loss who can’t benefit from hearing aids, cochlear implants might be an option. A cochlear implant is a small electronic device that gets surgically implanted into the ear and can stimulate the auditory nerve directly to provide a sense of sound. Who qualifies for a cochlear implant and the level of hearing loss that would necessitate such a device varies around the world. For example, in the UK, it might be recommended for people with very poor hearing in both ears, whereas in the US, the threshold for consideration is slightly lower.
In terms of other hearing aids, some people might find personal frequency modulation systems or “Roger pens” helpful. These are wireless microphones that can be used alongside hearing aids to help cut out background noise and focus on specific sounds or speech. These are just a few of the options available. As always, to find the one that’s right for you, it’s best to get a full hearing test done and discuss the results and options with your doctor or audiologist.
What else can Sensorineural Hearing Loss be?
Hearing loss from birth, known as congenital hearing loss, is the most common sensory disorder children are born with. This condition can stem from genetic and environmental factors. Congenital hearing loss originating from genetics can be either non-syndromic (70% of cases), meaning only hearing is impaired, or syndromic (30% of cases), where hearing loss is part of a syndrome or collection of other symptoms.
Non-syndromic genetic causes usually are due to autosomal recessive genes, with the gap junction beta 2 (GJB2) gene the most common. This gene creates a protein necessary for the cochlea’s potassium ion channels to work correctly. Diagnosis can be challenging, as there are no other physical symptoms, but testing generally includes genetic testing, electrocardiogram (ECG), and testing for cytomegalovirus infection.
For children with syndromic genetic hearing loss, identifying the underlying cause is crucial, as the other symptoms can be severe. The causes of this type of hearing loss include:
- Waardenburg syndrome: Accompanied by abnormalities in eye, skin, and cochlea pigmentation.
- Usher syndrome: Characterized by hearing loss and progressive visual loss due to SNHL and retinitis pigmentosa.
- Pendred syndrome: Often presents with varying degrees of SNHL, dysfunction of balance, and a thyroid goiter.
- Jervell and Lange-Nielsen syndrome: Along with SNHL, patients show prolonged QT interval on the ECG, which can lead to syncope or fainting, sudden death, or long QT syndrome.
- Alport syndrome: Normally presents with kidney inflammation, end-stage kidney disease, eye abnormalities, and bilateral SNHL.
Environmental factors that can cause congenital hearing loss include: intrauterine infections (such as toxoplasmosis, cytomegalovirus, herpes, rubella), alcohol, smoking, ototoxic drugs, and complications from premature births, lack of oxygen, or neonatal jaundice.
Acute sensorineural hearing loss, defined as a considerable loss of hearing over 72 hours, is an otolaryngologic emergency needing immediate management. The causes can include trauma, infection, malignancy, and Meniere’s disease. However, most patients have no identifiable cause of their hearing loss and will be classified as idiopathic. Work-up testing usually includes a pure tone audiogram.
Age-related hearing loss or presbycusis is a gradual bilateral SNHL occurring in mid to late adulthood. It usually involves degeneration of cochlear hair cells and is often associated with a decline in the ability to hear, especially in the presence of background noise. It is typically described as a lack of clarity rather than a loss of volume, often accompanied by ringing in the ears or tinnitus.
Noise-induced hearing loss occurs when a patient’s hearing is damaged by excessive noise exposure. Patients often experience worsening hearing loss over many years, often accompanied by tinnitus. Once diagnosed, the further noise exposure should be reduced as much as possible.
Other types of hearing loss include Meniere’s disease, autoimmune SNHL, and hearing loss due to head injuries or ototoxic agents. In Meniere’s disease, patients experience spontaneous episodic vertigo, hearing loss, and tinnitus. Autoimmune SNHL rapidly progresses and responds to steroid therapy. Head injuries resulting in temporal bone fractures can lead to conductive hearing loss or mixed SNHL. Ototoxic agents can cause SNHL, for example, aminoglycosides such as gentamicin result in hair cell death, and loop diuretics affect the stria vascularis, causing acute but reversible effects.
What to expect with Sensorineural Hearing Loss
Sensorineural hearing loss usually gets worse slowly over time. However, most patients can manage this with the help of hearing aids and regular check-ups and hearing tests. For those who qualify, a cochlear implant can help restore hearing even in significant cases.
If this hearing loss happens suddenly, four factors can help predict how well the patient will recover:
* When the loss occurred – the sooner it’s noticed, the better the chances of improvement
* Age – the outcomes tend to be worse for older patients
* Vertigo – having this can suggest a worse outcome
* How severe the hearing loss is – if it’s severe and the hearing test shows a downward trend, this can suggest a tougher road ahead.
Patients who get medical help early and follow their treatment plan closely will probably do better.
In cases of sensorineural hearing loss, 32% to 65% get better without needing treatment. The cause of this condition stays unknown in 80-90% of cases when they first see the doctor. Despite thorough medical examination, doctors can only figure out the cause in about one-third of cases.
Studies show that if a patient shows improvement within the first two weeks, they may have an excellent long-term outcome.
Possible Complications When Diagnosed with Sensorineural Hearing Loss
: Living with hearing loss can lead to both physical and mental challenges. For many people with SNHL (sensorineural hearing loss), the associated symptoms like tinnitus (ringing in the ears) and dizziness can be even more difficult to cope with than the hearing loss. Research shows that tinnitus can significantly disrupt people’s daily lives. This can manifest in several ways:
- Difficulty focusing
- Constant awareness of the noise
- Disturbed sleep
- An overall feeling of loss of control over their lives
Notably, fear also plays a big part in people’s experiences. People often express fear about the noise itself, the prospect of living with it long-term, and worry about activities that might make their symptoms worse.
Research has also found a link between untreated hearing loss and declining mental abilities. This supports the idea that early treatment with hearing aids can be beneficial. One long-term study confirms this link, suggesting that withdrawal from social activities and feelings of depression can contribute to this mental decline.
People with hearing loss often find it hard to participate in social situations and enjoy their usual activities, which can lead to isolation from friends and family. While support groups exist, they may not always be easily accessible, and some people feel a social stigma attached to hearing loss. As the population ages, hearing loss is becoming an increasingly common problem, particularly in developed countries.
Preventing Sensorineural Hearing Loss
Having sensorineural hearing loss can greatly affect a person’s day-to-day life and their ability to do normal activities. It’s important not only for these individuals to learn how to manage and live with this condition, but also for their loved ones to understand the challenges they’re facing.
If the hearing loss is caused by noise, the main treatment method is to avoid loud sounds as much as possible. When working in noisy environments, it’s crucial to use hearing protection. Regular hearing tests should also be done to keep track of any changes in hearing. Hearing aids can greatly improve how well individuals can hear, so it’s important they’re used consistently to get the most benefit.
