Sensorineural Hearing Loss (SNHL)
Post date: 15/09/2023
Hearing is the ability to perceive sounds. The decrease of hearing ability call hearing loss.
There are many different types of hearing loss, but they are typically classified into three main categories:
There is an organ in the inner ear called - The cochlea, which is a fluid-filled, spiral-shaped cavity found in the inner ear that plays a vital role in the sense of hearing and participates in the process of auditory transduction. Sound waves are transduced into electrical impulses that the brain can interpret as individual sound frequencies. Inside the cochlea are tiny hair cells whose job it is to turn sound into a signal.
Sensorineural hearing loss SNHL happens when there is damage to tiny hair cells in the cochlear and/or the auditory nerve. Sound energy reaches the cochlea, but damaged hair cells are unable to convert sound waves into neural signals that pass through the auditory nerve to the brain.
Some sounds seem overly loud in one ear.
You have problems following conversations when two or more people are talking.
You have problems hearing in noisy areas.
It is easier to hear men's voices than women's voices.
It is hard to tell high-pitched sounds (such as "s" or "th") from one another.
Other people's voices sound muffled or slurred.
Other Associated symptoms may include:
Feeling of being off-balance or dizzy (more common with Meniere disease and acoustic neuromas)
Ringing or buzzing sound in the ears (tinnitus)
There is an organ in the inner ear called - The cochlea, which is a fluid-filled, spiral-shaped cavity found in the inner ear that plays a vital role in the sense of hearing and participates in the process of auditory transduction. Sound waves are transduced into electrical impulses that the brain can interpret as individual sound frequencies. Inside the cochlea are tiny hair cells whose job it is to turn sound into a signal.
Sensorineural hearing loss SNHL happens when there is damage to tiny hair cells in the cochlear and/or the auditory nerve. Sound energy reaches the cochlea, but damaged hair cells are unable to convert sound waves into neural signals that pass through the auditory nerve to the brain. Auditory nerve abnormalities will also cause SNHL.
The causes of Sensorineural hearing loss may include:
Virus
Aging: Sensorineural hearing loss cause by aging that cannot be reversed (most common)
Acoustic trauma, noise induced hearing loss when exposure to loud noises (e.g., industrial/machinery or explosion/gunfire close to the ear; can be prevented with proper protection)
Illnesses: Viruses,diabetes, and high blood pressure are all common causes of hearing loss.
Head trauma or abrupt changes in air pressure—this can cause the space that contains inner ear fluid to rupture
Autoimmune inner ear disease when the body’s immune system mistakenly attacks the inner ear and causes progressive hearing loss in both ears.
Ménière’s disease is a condition characterized by fluctuating hearing loss, dizziness, ear fullness, or ringing in the ears (called tinnitus)
Central nervous disease damage caused by a condition such as multiple sclerosis
Cochlear otosclerosis abnormal bone growth in the cochlear of inner ear
Congenital inner ear malformation genetic or environmental abnormalities (very common cause in children)
Benign tumor, called “vestibular schwannoma,” this is a noncancerous tumor on the adjacent balance nerve that compresses the hearing nerve that connects the inner ear to the brain, causing Sensorineural hearing loss SNHL
Another important cause of hearing loss in the adult population is noise-induced hearing loss (NIHL). It has been estimated that 16% of adults worldwide disabling hearing loss is occupational noise related.This remains a common occupational disease despite legislation in place in most developed countries to prevent NIHL.
Congenital hearing loss is nearly always sensorineural in nature, and can have various etiologies. In patients with robust prenatal care, congenital infectious causes such as cytomegalovirus are rare and the most common causes are genetic. There are many genetic syndromes with hearing loss as a component, and SNHL developing in childhood warrants a thorough workup
Bilateral (both ears)
Hearing loss that is somewhat even in both ears is called bilateral. The National Institute on Aging estimated that bilateral hearing loss is the most common type experienced by older adults.16
Unilateral
Unilateral hearing loss occurs when one ear can hear within the normal range, but the other ear has some degree of hearing loss. You may also see the term single-sided deafness, or SSD, which refers to one ear completely lacking hearing ability.
Asymmetrical (one ear)
The term asymmetrical hearing loss refers to hearing loss that occurs in both ears, but it’s greater in one ear than the other. The shape of the audiogram, which shows how loud you need various sound frequencies to be in order to hear them, may also look different for one ear than the other.
Sudden sensorineural hearing loss
Sudden sensorineural hearing loss (SSNHL) is considered a medical emergency situation, this type of hearing loss that occurs within a 72-hour window due to sensorineural causes rather than a physical blockage (due to excess fluid or earwax, for example). It can be caused by an injury, illness, or exposure to a loud noise, like gunfire or an explosion. Research shows COVID-19 may also increase the risk of SSNHL.
In-person hearing exams
An in-person hearing exam at a hearing care clinic is a thorough assessment that takes about an hour and includes both a physical exam and several hearing tests.
Pure tone audiometry
Pure tone testing consists of several types of hearing tests that measure how well each ear can hear low, medium, and high sound frequencies.
Air and bone conduction testing:
Both of these types of sound conduction are measured to determine whether a person has SNHL, conductive hearing loss, or mixed hearing loss (a combination of both types).
Speech audiometry
Speech audiometry consists of several parts that when combined, provide an overall picture of any hearing deficits that may affect your understanding of speech and conversations.
Speech reception threshold (SRT) testing: This part of the exam tests the lowest volume at which you can hear and understand speech.
Speech discrimination testing: In this section, you’ll repeat words that are spoken to you to determine how well you understand speech.
Speech in noise testing: This test determines how well you can hear and understand speech in the presence of background noise.
After your exam is complete, you’ll receive a graph called an audiogram with the results from your pure tone audiometry tests. It shows the lowest volume at which you can hear different sound frequencies half of the time in each ear.
Audiogram results can be used in the following ways:
To serve as the basis for a hearing professional to program your prescription hearing aids
To calculate your pure tone average (PTA) ⓘ, or Hearing Number
To track changes in your hearing ability over time
Online hearing screenings
A number of online hearing screenings are now available. Most of them are free and take less than five minutes to complete. Online screenings can’t be used for diagnostic purposes, but they’re a great way to get a general idea of your hearing ability.
The Hearing Number
The Johns Hopkins Cochlear Center for Hearing and Public Health has developed an easy method of monitoring your hearing health, similar to the way many people keep track of other health numbers such as blood pressure or cholesterol.
The Hearing Number is equivalent to the PTA from an audiogram. If you haven’t had an audiogram, you can check your hearing and get your Hearing Number by installing the free Mimi Hearing Test app on your smartphone.
The app is currently available only for Apple devices. After a three-minute hearing check called the Pure Tone Threshold test, the Mimi app provides your audiogram and Hearing Number. You can also keep track of your hearing results over time.
Hearing loss is the most common congenital sensory disorder, often requiring pediatricians' expertise in conjunction with medical geneticists and pediatric otolaryngologists.
Congenital causes of hearing loss can be divided into genetic and environmental. Genetic causes can be further divided into non-syndromic (70%) and syndromic (30%).
Genetic Non-syndromic
Of the nonsyndromic causes, the most common inheritance pattern is autosomal recessive, followed by autosomal dominant. More than 60 autosomal recessive genes have been identified, the most common being the gap junction beta 2 (GJB2) gene, which accounts for half of nonsyndromic hearing loss cases. GJB2 encodes connexin 26, a protein important for the proper functioning of the cochlea's potassium ion channels. In these patients, due to an absence of other physical findings or relevant history, diagnostic workup remains a challenge but primarily consists of genetic testing, electrocardiogram (ECG), and testing for cytomegalovirus infection.
Genetic Syndromic
In children who have hearing loss due to syndrome, determining the underlying cause is often more important as the other clinical features can be severe.
More than 400 syndromes have been identified with hearing loss as a feature; however, only a small number of these account for most cases of SNHL.Outlined below are the key features of the most common syndromes seen in children.
Waardenburg syndrome is the most common, with SNHL being a significant feature found in over two-thirds of patients.[26] The other key feature is pigmentation abnormalities of the eyes, skin, and cochlea.
Usher syndrome is one of the most common autosomal recessive causes of syndromic hearing loss. This condition is characterized by hearing loss and visual loss due to a progressive SNHL and retinitis pigmentosa.
Pendred syndrome classically presents with a varying degree of SNHL, vestibular dysfunction, and a thyroid goiter. Along with Usher syndrome, it is another one of the most common autosomal recessive causes of syndromic hearing loss. A specific mutation in SLC26A4 occurs in around half of the affected patients.
Jervell and Lange-Nielsen syndrome is also inherited with an autosomal recessive pattern. The key feature, along with SNHL, is a prolonged QT interval seen on the ECG. These patients can suffer from or have a family history of syncope, sudden death, or long QT syndrome.
Alport syndrome is inherited in an X-linked manner and occurs due to a defect in type IV collagen. It classically presents with glomerulonephritis, end-stage kidney disease, eye abnormalities, and a bilateral SNHL. The hearing loss is initially in high frequency, but the lower frequencies begin to get affected as it worsens. Hematuria and proteinuria are key signs as the condition progresses.
Acute Sensorineural Hearing Loss
Acute sensorineural hearing loss is defined as a hearing loss greater than 30 dB in at least three consecutive audiometric frequencies over 72 hours.
This is usually classified as an otolaryngologic emergency condition, which requires prompt management.
There are several possible causes of acute SNHL, including trauma, infection, malignancy, and Meniere's disease; however, there is no identifiable cause of their hearing loss in most patients and will be classed as idiopathic. As part of the work-up, patients should have a pure tone audiogram as soon as possible. Often routine blood tests and an autoimmune screen are sent off, although practice varies between departments.
Presbycusis - age-related hearing loss
Presbycusis or age-related hearing loss can be defined as a progressive bilateral SNHL of mid to late adult-onset. The diagnosis of presbycusis is one of exclusion, and primary causes such as otosclerosis, Meniere's disease, and cytotoxicity, amongst many others, must be excluded first.
It is commonly associated with degeneration of cochlear hair cells, mainly OHCs in the cochlea's basal portion, and the changes begin in the basal end of the cochlea and spread towards the apex as the condition worsens. Patients typically present with a slowly deteriorating hearing loss, especially in the presence of background noise. It is often a lack of clarity rather than a loss of volume that the patient describes. Tinnitus is frequently an accompanying symptom and can be the most challenging aspect for the patient.
A typical PTA will show a gradual downsloping hearing loss towards higher frequencies. It has been shown that once a certain amount of hearing loss has occurred (roughly 70-80 dB), further progression is slow, especially in the higher frequencies. In terms of management options, hearing aids often benefit patients and prevent social isolation and depression.
Noise-induced Hearing Loss
This condition occurs when a patient experiences hearing loss due to excessive noise exposure, either recreational or occupational. Occupational noise exposure is one of the most prevalent, potentially preventable health conditions. It has a slight male predominance and usually affects the middle-aged population. The symptoms present similar to most SNHL conditions, with the insidious progression of worsening hearing loss over many years, often accompanied by tinnitus. Hyperacusis is found in 40% of tinnitus sufferers, and its severity can be determined using a hyperacusis questionnaire. Bedside otological examination is usually normal, and the diagnosis is generally based on the history combined with the classical finding of a notched appearance at 4kHz, which appears to start recovering at 8kHz on a pure tone audiogram. This is known as the Carhart's notch; however, it is not always present. Without a previous noise exposure history, it is not indicative of NIHL. Once a diagnosis is reached, it is essential to reduce further noise exposure as much as possible using ear protection. The Control of Noise at Work Regulations of 2005 sets out a framework for employers to ensure their employees' safety based on their average occupational sound exposure.
Others
Meniere's disease is characterized by a triad of spontaneous episodic vertigo, hearing loss, and tinnitus. Patients may also experience aural fullness. Their PTA usually shows an up sloping curve indicating a low-frequency moderate SNHL. PTA remains the most useful investigation, but a brain MRI is done to rule out lesions such as a vestibular schwannoma. Treatment ranges from conservative such as alcohol, coffee, and salt restriction, to treatments targeted at the symptoms most affecting the patients. Vestibular suppressants such as prochlorperazine can be helpful. Hearing aids and tinnitus retraining therapy can also be used. Psychological support can be key in those patients who suffer from the psychological complications of the condition.
Autoimmune Sensorineural hearing loss SNHL, Autoimmune inner ear disease (AIED) was described in 1979 by McCabe as a rapidly progressive bilateral SNHL that responded to steroid therapy. Several antigens have been implicated in the etiology. Many systemic autoimmune disorders have been reported, such as Wegener's granulomatosis, rheumatoid arthritis, and systemic lupus erythematosus. Patients usually present in their early twenties. The condition has a female predominance. Symptoms often start in one ear before becoming bilateral in the majority of patients. Aside from audiometric evaluation, blood tests (erythrocyte sedimentation rate, antinuclear antibody) looking specifically at autoimmune conditions are sent off. Treatment is directed by rheumatologists and includes steroid therapy, long-term intratympanic steroid injections, cyclophosphamide, and IL-1 receptor antagonists.
A head injury that results in a temporal bone fracture can lead to conductive hearing loss or mixed SNHL. Otic capsule fractures cause a severe SNHL through various mechanisms, including disruption of the membranous labyrinth, hemorrhage into the cochlea, perilymph fistula, and avulsion or trauma of the cochlear nerve. In those cases that result in bilateral deafness, a cochlear implant is a treatment option.
Ototoxic agents can cause SNHL in many ways. Aminoglycosides such as gentamicin cause hair cell death resulting in permanent hearing loss and balance dysfunction. This can occur after repeated administration of systemic therapy. The hearing loss initially affects the higher frequencies but continues progressively to the lower frequencies as more hair cells are damaged. Loop diuretics are thought to affect the stria vascularis and cause acute but completely reversible effects.
With sudden SNHL, four factors have been shown to help predict the outcome.
Time since onset - the earlier it presents, the better the prognosis
Age - worst prognosis in older patients
Vertigo - poor prognostic indicator
Degree of hearing loss - if profound and with a downward sloping audiogram indicates a poorer prognosis.
Patients who seek early medical attention and engage with their treatment will likely have better outcomes.
In Sensorineural hearing loss SNHL, 32% to 65% of the cases resolve without intervention.
The cause is unknown at the presentation in 80-90% of the cases. Even after a thorough investigation, it is possible to identify a cause in only one-third of the patients. It has been shown that improvement within the first two weeks may predict an excellent long-term outcome.
Tinnitus and dizziness, which they often find more challenging to tolerate than hearing loss. Studies have been done to evaluate the impact tinnitus can have on patients' lives. Prevalent responses included inability to concentrate, constant awareness, the effect on sleep, intrusiveness, and overall loss of control over their lives.
Fear: Patients reported fear of the tinnitus itself, fear of living with tinnitus long term, and a fear of doing activities that may exacerbate their symptoms.
Cognitive decline: Various studies have shown a correlation between uncorrected hearing loss and cognitive decline, strengthening the argument for early auditory rehabilitation with hearing aids. A prospective 25-year longitudinal study confirms this correlation and suggests that social isolation and depression facilitates this decline.
A critical part of the evaluation will be a hearing test (audiogram) performed by an audiologist to determine the severity of your hearing loss, as well as whether it is conductive, sensorineural, or a combination of both.
Your ENT specialist may recommend specific treatment options based on the results of your hearing test, or other potential tests such as a CT or MRI imaging scan.
Treatment options can include:
Keyword:
Sensorineural Hearing Loss (SNHL), hearing loss, Difficulty hearing soft sounds, Ear drainage, dizziness, Presbycusis, age-related hearing loss, Noise-induced Hearing Loss, Meniere's disease, Autoimmune inner ear disease (AIED),
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keyword: Hearing loss, Degrees of Hearing Loss, Normal hearing, Sensorineural Hearing Loss (SNHL), Difficulty hearing soft sounds, dizziness, presbycusis, age-related hearing loss, noise-induced hearing loss (NIHL), meniere's disease, autoimmune inner ear disease (AIED),
There are many different types of hearing loss, but they are typically classified into three main categories:
- Conductive hearing loss occurs when there is a problem with the outer or middle ear, which blocks sound from reaching the inner ear. This type of hearing loss can be caused by earwax buildup, ear infections, or damage to the eardrum or bones of the middle ear.
- Sensorineural hearing loss occurs when there is damage to the inner ear or the auditory nerve, which sends sound signals to the brain. This type of hearing loss is often caused by aging, noise exposure, or certain diseases, such as Meniere's disease.
- Mixed hearing loss is a combination of conductive and sensorineural hearing loss. This type of hearing loss can be caused by a combination of factors, such as earwax buildup and age-related hearing loss.
In addition to these three main categories, there are also other types of hearing loss, such as:
- Central hearing loss occurs when there is a problem with the way the brain interprets sound signals. This type of hearing loss is rare and can be caused by certain diseases, such as stroke or multiple sclerosis.
- Functional hearing loss is a type of hearing loss that is not caused by any physical damage to the ears or the auditory system. This type of hearing loss is often caused by stress, anxiety, or depression.
What is Sensorineural hearing loss (SNHL)
Sensorineural hearing loss (SNHL) happens when there is damage to tiny hair cells in the cochlear and/or the auditory nerve.There is an organ in the inner ear called - The cochlea, which is a fluid-filled, spiral-shaped cavity found in the inner ear that plays a vital role in the sense of hearing and participates in the process of auditory transduction. Sound waves are transduced into electrical impulses that the brain can interpret as individual sound frequencies. Inside the cochlea are tiny hair cells whose job it is to turn sound into a signal.
Sensorineural hearing loss SNHL happens when there is damage to tiny hair cells in the cochlear and/or the auditory nerve. Sound energy reaches the cochlea, but damaged hair cells are unable to convert sound waves into neural signals that pass through the auditory nerve to the brain.
What Are the Symptoms of Sensorineural Hearing Loss SNHL?
Symptoms of Sensorineural Hearing Loss may include:Some sounds seem overly loud in one ear.
You have problems following conversations when two or more people are talking.
You have problems hearing in noisy areas.
It is easier to hear men's voices than women's voices.
It is hard to tell high-pitched sounds (such as "s" or "th") from one another.
Other people's voices sound muffled or slurred.
Other Associated symptoms may include:
Feeling of being off-balance or dizzy (more common with Meniere disease and acoustic neuromas)
Ringing or buzzing sound in the ears (tinnitus)
Etiology - What Causes Sensorineural hearing loss SNHL?
There is an organ in the inner ear called - The cochlea, which is a fluid-filled, spiral-shaped cavity found in the inner ear that plays a vital role in the sense of hearing and participates in the process of auditory transduction. Sound waves are transduced into electrical impulses that the brain can interpret as individual sound frequencies. Inside the cochlea are tiny hair cells whose job it is to turn sound into a signal.Sensorineural hearing loss SNHL happens when there is damage to tiny hair cells in the cochlear and/or the auditory nerve. Sound energy reaches the cochlea, but damaged hair cells are unable to convert sound waves into neural signals that pass through the auditory nerve to the brain. Auditory nerve abnormalities will also cause SNHL.
The causes of Sensorineural hearing loss may include:
Virus
Aging: Sensorineural hearing loss cause by aging that cannot be reversed (most common)
Acoustic trauma, noise induced hearing loss when exposure to loud noises (e.g., industrial/machinery or explosion/gunfire close to the ear; can be prevented with proper protection)
Illnesses: Viruses,diabetes, and high blood pressure are all common causes of hearing loss.
Head trauma or abrupt changes in air pressure—this can cause the space that contains inner ear fluid to rupture
Autoimmune inner ear disease when the body’s immune system mistakenly attacks the inner ear and causes progressive hearing loss in both ears.
Ménière’s disease is a condition characterized by fluctuating hearing loss, dizziness, ear fullness, or ringing in the ears (called tinnitus)
Central nervous disease damage caused by a condition such as multiple sclerosis
Cochlear otosclerosis abnormal bone growth in the cochlear of inner ear
Congenital inner ear malformation genetic or environmental abnormalities (very common cause in children)
Benign tumor, called “vestibular schwannoma,” this is a noncancerous tumor on the adjacent balance nerve that compresses the hearing nerve that connects the inner ear to the brain, causing Sensorineural hearing loss SNHL
Epidemiology
The incidence of sensorineural hearing loss varies in different countries. In the United States, sudden SNHL affects between 5-27 per 100,000 people each year, with approximately 66,000 new annual cases.Another important cause of hearing loss in the adult population is noise-induced hearing loss (NIHL). It has been estimated that 16% of adults worldwide disabling hearing loss is occupational noise related.This remains a common occupational disease despite legislation in place in most developed countries to prevent NIHL.
Congenital hearing loss is nearly always sensorineural in nature, and can have various etiologies. In patients with robust prenatal care, congenital infectious causes such as cytomegalovirus are rare and the most common causes are genetic. There are many genetic syndromes with hearing loss as a component, and SNHL developing in childhood warrants a thorough workup
Types of sensorineural hearing loss
Just as eyesight can vary between the right and left eye, hearing ability is often different in each ear.Bilateral (both ears)
Hearing loss that is somewhat even in both ears is called bilateral. The National Institute on Aging estimated that bilateral hearing loss is the most common type experienced by older adults.16
Unilateral
Unilateral hearing loss occurs when one ear can hear within the normal range, but the other ear has some degree of hearing loss. You may also see the term single-sided deafness, or SSD, which refers to one ear completely lacking hearing ability.
Asymmetrical (one ear)
The term asymmetrical hearing loss refers to hearing loss that occurs in both ears, but it’s greater in one ear than the other. The shape of the audiogram, which shows how loud you need various sound frequencies to be in order to hear them, may also look different for one ear than the other.
Sudden sensorineural hearing loss
Sudden sensorineural hearing loss (SSNHL) is considered a medical emergency situation, this type of hearing loss that occurs within a 72-hour window due to sensorineural causes rather than a physical blockage (due to excess fluid or earwax, for example). It can be caused by an injury, illness, or exposure to a loud noise, like gunfire or an explosion. Research shows COVID-19 may also increase the risk of SSNHL.
Diagnosing sensorineural Hearing loss
An audiologist at a hearing care clinic can conduct testing to diagnose your type and degree of hearing loss. Hearing instrument specialists can also evaluate hearing loss for the purpose of fitting and dispensing hearing aids.22 And if you’re unable to get to a hearing care clinic or simply want a general idea of how good your hearing is, you can take an online hearing screening.In-person hearing exams
An in-person hearing exam at a hearing care clinic is a thorough assessment that takes about an hour and includes both a physical exam and several hearing tests.
Pure tone audiometry
Pure tone testing consists of several types of hearing tests that measure how well each ear can hear low, medium, and high sound frequencies.
Air and bone conduction testing:
Both of these types of sound conduction are measured to determine whether a person has SNHL, conductive hearing loss, or mixed hearing loss (a combination of both types).
Speech audiometry
Speech audiometry consists of several parts that when combined, provide an overall picture of any hearing deficits that may affect your understanding of speech and conversations.
Speech reception threshold (SRT) testing: This part of the exam tests the lowest volume at which you can hear and understand speech.
Speech discrimination testing: In this section, you’ll repeat words that are spoken to you to determine how well you understand speech.
Speech in noise testing: This test determines how well you can hear and understand speech in the presence of background noise.
After your exam is complete, you’ll receive a graph called an audiogram with the results from your pure tone audiometry tests. It shows the lowest volume at which you can hear different sound frequencies half of the time in each ear.
Audiogram results can be used in the following ways:
To serve as the basis for a hearing professional to program your prescription hearing aids
To calculate your pure tone average (PTA) ⓘ, or Hearing Number
To track changes in your hearing ability over time
Online hearing screenings
A number of online hearing screenings are now available. Most of them are free and take less than five minutes to complete. Online screenings can’t be used for diagnostic purposes, but they’re a great way to get a general idea of your hearing ability.
The Hearing Number
The Johns Hopkins Cochlear Center for Hearing and Public Health has developed an easy method of monitoring your hearing health, similar to the way many people keep track of other health numbers such as blood pressure or cholesterol.
The Hearing Number is equivalent to the PTA from an audiogram. If you haven’t had an audiogram, you can check your hearing and get your Hearing Number by installing the free Mimi Hearing Test app on your smartphone.
The app is currently available only for Apple devices. After a three-minute hearing check called the Pure Tone Threshold test, the Mimi app provides your audiogram and Hearing Number. You can also keep track of your hearing results over time.
Differential Diagnosis
CongenitalHearing loss is the most common congenital sensory disorder, often requiring pediatricians' expertise in conjunction with medical geneticists and pediatric otolaryngologists.
Congenital causes of hearing loss can be divided into genetic and environmental. Genetic causes can be further divided into non-syndromic (70%) and syndromic (30%).
Genetic Non-syndromic
Of the nonsyndromic causes, the most common inheritance pattern is autosomal recessive, followed by autosomal dominant. More than 60 autosomal recessive genes have been identified, the most common being the gap junction beta 2 (GJB2) gene, which accounts for half of nonsyndromic hearing loss cases. GJB2 encodes connexin 26, a protein important for the proper functioning of the cochlea's potassium ion channels. In these patients, due to an absence of other physical findings or relevant history, diagnostic workup remains a challenge but primarily consists of genetic testing, electrocardiogram (ECG), and testing for cytomegalovirus infection.
Genetic Syndromic
In children who have hearing loss due to syndrome, determining the underlying cause is often more important as the other clinical features can be severe.
More than 400 syndromes have been identified with hearing loss as a feature; however, only a small number of these account for most cases of SNHL.Outlined below are the key features of the most common syndromes seen in children.
Waardenburg syndrome is the most common, with SNHL being a significant feature found in over two-thirds of patients.[26] The other key feature is pigmentation abnormalities of the eyes, skin, and cochlea.
Usher syndrome is one of the most common autosomal recessive causes of syndromic hearing loss. This condition is characterized by hearing loss and visual loss due to a progressive SNHL and retinitis pigmentosa.
Pendred syndrome classically presents with a varying degree of SNHL, vestibular dysfunction, and a thyroid goiter. Along with Usher syndrome, it is another one of the most common autosomal recessive causes of syndromic hearing loss. A specific mutation in SLC26A4 occurs in around half of the affected patients.
Jervell and Lange-Nielsen syndrome is also inherited with an autosomal recessive pattern. The key feature, along with SNHL, is a prolonged QT interval seen on the ECG. These patients can suffer from or have a family history of syncope, sudden death, or long QT syndrome.
Alport syndrome is inherited in an X-linked manner and occurs due to a defect in type IV collagen. It classically presents with glomerulonephritis, end-stage kidney disease, eye abnormalities, and a bilateral SNHL. The hearing loss is initially in high frequency, but the lower frequencies begin to get affected as it worsens. Hematuria and proteinuria are key signs as the condition progresses.
Acute Sensorineural Hearing Loss
Acute sensorineural hearing loss is defined as a hearing loss greater than 30 dB in at least three consecutive audiometric frequencies over 72 hours.
This is usually classified as an otolaryngologic emergency condition, which requires prompt management.
There are several possible causes of acute SNHL, including trauma, infection, malignancy, and Meniere's disease; however, there is no identifiable cause of their hearing loss in most patients and will be classed as idiopathic. As part of the work-up, patients should have a pure tone audiogram as soon as possible. Often routine blood tests and an autoimmune screen are sent off, although practice varies between departments.
Presbycusis - age-related hearing loss
Presbycusis or age-related hearing loss can be defined as a progressive bilateral SNHL of mid to late adult-onset. The diagnosis of presbycusis is one of exclusion, and primary causes such as otosclerosis, Meniere's disease, and cytotoxicity, amongst many others, must be excluded first.
It is commonly associated with degeneration of cochlear hair cells, mainly OHCs in the cochlea's basal portion, and the changes begin in the basal end of the cochlea and spread towards the apex as the condition worsens. Patients typically present with a slowly deteriorating hearing loss, especially in the presence of background noise. It is often a lack of clarity rather than a loss of volume that the patient describes. Tinnitus is frequently an accompanying symptom and can be the most challenging aspect for the patient.
A typical PTA will show a gradual downsloping hearing loss towards higher frequencies. It has been shown that once a certain amount of hearing loss has occurred (roughly 70-80 dB), further progression is slow, especially in the higher frequencies. In terms of management options, hearing aids often benefit patients and prevent social isolation and depression.
Noise-induced Hearing Loss
This condition occurs when a patient experiences hearing loss due to excessive noise exposure, either recreational or occupational. Occupational noise exposure is one of the most prevalent, potentially preventable health conditions. It has a slight male predominance and usually affects the middle-aged population. The symptoms present similar to most SNHL conditions, with the insidious progression of worsening hearing loss over many years, often accompanied by tinnitus. Hyperacusis is found in 40% of tinnitus sufferers, and its severity can be determined using a hyperacusis questionnaire. Bedside otological examination is usually normal, and the diagnosis is generally based on the history combined with the classical finding of a notched appearance at 4kHz, which appears to start recovering at 8kHz on a pure tone audiogram. This is known as the Carhart's notch; however, it is not always present. Without a previous noise exposure history, it is not indicative of NIHL. Once a diagnosis is reached, it is essential to reduce further noise exposure as much as possible using ear protection. The Control of Noise at Work Regulations of 2005 sets out a framework for employers to ensure their employees' safety based on their average occupational sound exposure.
Others
Meniere's disease is characterized by a triad of spontaneous episodic vertigo, hearing loss, and tinnitus. Patients may also experience aural fullness. Their PTA usually shows an up sloping curve indicating a low-frequency moderate SNHL. PTA remains the most useful investigation, but a brain MRI is done to rule out lesions such as a vestibular schwannoma. Treatment ranges from conservative such as alcohol, coffee, and salt restriction, to treatments targeted at the symptoms most affecting the patients. Vestibular suppressants such as prochlorperazine can be helpful. Hearing aids and tinnitus retraining therapy can also be used. Psychological support can be key in those patients who suffer from the psychological complications of the condition.
Autoimmune Sensorineural hearing loss SNHL, Autoimmune inner ear disease (AIED) was described in 1979 by McCabe as a rapidly progressive bilateral SNHL that responded to steroid therapy. Several antigens have been implicated in the etiology. Many systemic autoimmune disorders have been reported, such as Wegener's granulomatosis, rheumatoid arthritis, and systemic lupus erythematosus. Patients usually present in their early twenties. The condition has a female predominance. Symptoms often start in one ear before becoming bilateral in the majority of patients. Aside from audiometric evaluation, blood tests (erythrocyte sedimentation rate, antinuclear antibody) looking specifically at autoimmune conditions are sent off. Treatment is directed by rheumatologists and includes steroid therapy, long-term intratympanic steroid injections, cyclophosphamide, and IL-1 receptor antagonists.
A head injury that results in a temporal bone fracture can lead to conductive hearing loss or mixed SNHL. Otic capsule fractures cause a severe SNHL through various mechanisms, including disruption of the membranous labyrinth, hemorrhage into the cochlea, perilymph fistula, and avulsion or trauma of the cochlear nerve. In those cases that result in bilateral deafness, a cochlear implant is a treatment option.
Ototoxic agents can cause SNHL in many ways. Aminoglycosides such as gentamicin cause hair cell death resulting in permanent hearing loss and balance dysfunction. This can occur after repeated administration of systemic therapy. The hearing loss initially affects the higher frequencies but continues progressively to the lower frequencies as more hair cells are damaged. Loop diuretics are thought to affect the stria vascularis and cause acute but completely reversible effects.
Prognosis of Sensorineural hearing loss
Sensorineural hearing loss tends to have a typical slow progression and can be managed with conservative measures and hearing aids for the vast majority of patients with regular follow-up appointments and audiograms. If patients are eligible, even profound hearing loss can be rehabilitated with a cochlear implant.With sudden SNHL, four factors have been shown to help predict the outcome.
Time since onset - the earlier it presents, the better the prognosis
Age - worst prognosis in older patients
Vertigo - poor prognostic indicator
Degree of hearing loss - if profound and with a downward sloping audiogram indicates a poorer prognosis.
Patients who seek early medical attention and engage with their treatment will likely have better outcomes.
In Sensorineural hearing loss SNHL, 32% to 65% of the cases resolve without intervention.
The cause is unknown at the presentation in 80-90% of the cases. Even after a thorough investigation, it is possible to identify a cause in only one-third of the patients. It has been shown that improvement within the first two weeks may predict an excellent long-term outcome.
Complications
Complications can include physical symptoms and the psychological impact of living with hearing loss. Many patients with SNHL suffer from other associated symptoms such as:Tinnitus and dizziness, which they often find more challenging to tolerate than hearing loss. Studies have been done to evaluate the impact tinnitus can have on patients' lives. Prevalent responses included inability to concentrate, constant awareness, the effect on sleep, intrusiveness, and overall loss of control over their lives.
Fear: Patients reported fear of the tinnitus itself, fear of living with tinnitus long term, and a fear of doing activities that may exacerbate their symptoms.
Cognitive decline: Various studies have shown a correlation between uncorrected hearing loss and cognitive decline, strengthening the argument for early auditory rehabilitation with hearing aids. A prospective 25-year longitudinal study confirms this correlation and suggests that social isolation and depression facilitates this decline.
What Are the Treatment Options for Sensorineural hearing loss
The treatment for hearing loss depends on the cause. Once a diagnosis is made, your physician will be able to talk to you about all treatment options.A critical part of the evaluation will be a hearing test (audiogram) performed by an audiologist to determine the severity of your hearing loss, as well as whether it is conductive, sensorineural, or a combination of both.
Your ENT specialist may recommend specific treatment options based on the results of your hearing test, or other potential tests such as a CT or MRI imaging scan.
Treatment options can include:
- Continuing observation with repeated hearing tests
- Medical therapy—corticosteroids (oral or injection through the eardrum) may be used to reduce cochlear hair cell swelling and inflammation after exposure to loud noises; diuretics may be used for Ménière’s disease
- Clinical diet for Sensorineural hearing loss, Low-sodium diet
- Evaluation and fitting of a hearing aid(s) or other assistive listening devices
- Preferential seating in class for school children
- Surgery to correct the cause of the hearing loss
- Surgery to implant a hearing device
- Sensorineural hearing loss SNHL can be treated with the use of conventional hearing aids or an implantable hearing device. Again, your ENT specialist and/or audiologist can help you decide which device may work best for you depending on your hearing test results and your lifestyle.
Keyword:
Sensorineural Hearing Loss (SNHL), hearing loss, Difficulty hearing soft sounds, Ear drainage, dizziness, Presbycusis, age-related hearing loss, Noise-induced Hearing Loss, Meniere's disease, Autoimmune inner ear disease (AIED),
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keyword: Hearing loss, Degrees of Hearing Loss, Normal hearing, Sensorineural Hearing Loss (SNHL), Difficulty hearing soft sounds, dizziness, presbycusis, age-related hearing loss, noise-induced hearing loss (NIHL), meniere's disease, autoimmune inner ear disease (AIED),
