Unraveling Hearing Loss: The Difference Between Conductive and Sensorineural Hearing Loss
The Basics: What is Conductive Hearing Loss?
Conductive hearing loss occurs when sound waves cannot efficiently travel through the outer and middle ear to reach the inner ear. This impairment is often due to blockages such as earwax, fluid buildup, or structural damage, leading to difficulties in hearing faint sounds and causing louder sounds to feel muffled or distorted.
Conductive hearing loss is relatively common and affects people of all ages, though it is particularly prevalent among children, especially during winter, due to ear infections or blockages. In adults, conductive hearing loss is less frequent but can still occur due to conditions like otosclerosis. Unlike sensorineural hearing loss, it often has treatable causes, making timely intervention crucial.
Individuals with conductive hearing loss often describe sounds as muffled, as if they are listening through a barrier or underwater. Lower and moderate frequencies may be harder to discern, making speech sound unclear, especially in noisy environments. While many cases are temporary and treatable, such as those caused by earwax or infections, others, like those resulting from chronic ear disease or genetic conditions like otosclerosis, may lead to permanent hearing loss if left untreated. Treatment options such as surgery or hearing aids can often provide relief.
In severe cases, conductive hearing loss can be considered a disability, especially if it significantly impacts communication and daily activities. The degree of impact varies based on the severity and duration of the hearing loss. Addressing the root causes promptly is essential to prevent further deterioration and maintain quality of life.
The Fundamentals of Sensorineural Hearing Loss
Sensorineural hearing loss (SNHL) occurs due to damage to the inner ear (cochlea) or the auditory nerve, often caused by aging, prolonged noise exposure, certain medications, or underlying health conditions. This type of hearing loss affects the clarity of both soft and loud sounds, making it particularly challenging to understand speech in noisy environments. High-frequency sounds, such as children's voices or birds chirping, are often harder to hear, while lower frequencies may remain relatively unaffected.
As the most common type of permanent hearing loss, SNHL affects approximately one in six people, with age-related hearing loss, or presbycusis, being a leading cause among older adults. However, it can also occur in younger individuals due to genetic factors, sudden hearing loss events, or prolonged exposure to loud noises. Those with a family history of hearing loss are at an increased risk of developing SNHL, even if it occurs gradually over time.
Sensorineural hearing loss is permanent, as damage to the inner ear hair cells or auditory nerve cannot be reversed. While some cases, such as sudden hearing loss, may show partial recovery with early treatment, most individuals benefit from hearing aids or cochlear implants to improve their hearing and quality of life. Regular monitoring and timely intervention are crucial, as SNHL can worsen over time due to ongoing noise exposure or untreated conditions.
The impact of SNHL on daily life can be profound, from difficulty communicating in social settings to challenges enjoying activities like music or TV. Left unmanaged, it may lead to social isolation, frustration, or even cognitive decline. While hearing loss can qualify as a disability if it significantly affects daily life, hearing devices and other accommodations can help mitigate its effects and enhance overall well-being.
Symptoms and Signs of Conductive and Sensorineural Hearing Loss
Identifying Conductive Hearing Loss Symptoms
Conductive hearing loss in young children can often be evident by the child appearing to ‘not listen.’ Hearing loss may also cause a deterioration in a child’s behavior, speech, and language development and cause them to get more tired. In children, this often occurs in the context of a recent cold or ear infection. However, it can occur without any specifically recognizable trigger.
Adults with conductive hearing loss may report that their ears feel blocked or muffled like the sound has been turned down. They may also report that their voice feels echoey.
Recognizing Sensorineural Hearing Loss Symptoms
In the early stages of sensorineural hearing loss, it often sounds like people are mumbling. This is because the high frequencies are usually affected first, making the beginnings and ends of words harder to hear—this can be mistaken for feeling like people are not pronouncing their words. This often shows up at first by having trouble hearing in noisy environments. As the hearing loss progresses, there are other signs, such as the person asking for things to be repeated more often, the TV being louder, and communication generally being more challenging.
It is important to note that you may be unable to tell the difference between conductive and sensorineural hearing loss based on symptomology alone. A diagnostic hearing test is the best way to determine the nature and degree of hearing loss.
Diagnostic Procedures: Understanding Hearing Tests
The best way to determine if you have hearing loss and whether it is conductive or sensorineural is to have a diagnostic hearing test. During this test, your hearing care professional will evaluate your hearing, hearing health, and middle ear function. Audiometry, one part of this test, produces an audiogram, a graph showing how well you hear.
Conductive vs Sensorineural Hearing Loss Audiograms
An audiogram shows the lowest sound level you respond to through air and bone conduction. When testing with air conduction, the hearing care professional will use headphones that play sounds in your ears. These sounds must travel along the whole hearing pathway and will, therefore, show if there is hearing loss anywhere along that pathway. They will also play sounds to you with a particular type of headphone that sits on the bone behind your ear. This is called a bone conductor. The bone conductor bypasses the outer and middle ear and evaluates the hearing in the inner ear and nerve pathway. By comparing the air conduction results and the bone conduction results, your hearing care professional can obtain information about the degree of your hearing loss and whether it is sensorineural or conductive.
Bone conduction thresholds are presented on an audiogram using < or [ for the right ear and > or ] symbols for the left ear. Air conduction thresholds are represented using O for the right ear and X for the left ear.
Interpreting a Conductive hearing loss audiogram
If you have conductive hearing loss, the bone conduction results will be in the normal range as the inner ear is still working well. However, the air conduction results will be elevated outside the normal range because something in the outer or middle ear is blocking the sound and causing conductive hearing loss.
Interpreting a Sensorineural hearing loss audiogram
If you have a sensorineural loss, the air and bone conduction thresholds will be elevated outside the normal range for at least some of the frequencies.
Causes Behind the Conditions: Conductive vs Sensorineural Hearing Loss
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Yes, otitis media is a common cause of conductive hearing loss, especially in young children. It often resolves on its own, but surgical intervention is possible if it is causing significant hearing loss on an ongoing basis.
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Acoustic neuroma causes sensorineural hearing loss by interfering with the transmission of auditory information along the nerve. Removing the acoustic neuroma may alleviate any impingement on the nerve, which can improve hearing. However, often, people are left with some ongoing sensorineural hearing loss due to either damage from the acoustic neuroma or damage from removing it.
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Allergies typically do not cause sensorineural hearing loss. However, they can lead to conductive hearing loss by causing fluid buildup or inflammation in the middle ear, which affects how sound is conducted. In rare cases, if severe inflammation or infections spread to the inner ear, there may be some impact on the auditory nerve, but this is uncommon. Sensorineural hearing loss is more commonly caused by damage to the inner ear due to factors like aging, noise exposure, or genetic conditions rather than allergies.
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Yes, head trauma can cause sensorineural hearing loss (SNHL). A severe blow to the head can damage the inner ear structures, including the cochlea, or disrupt the auditory nerve, which are essential for transmitting sound signals to the brain. Traumatic brain injuries (TBI) can also affect the blood flow to the inner ear, leading to hearing loss. Depending on the severity of the injury, the hearing loss may be temporary or permanent. In some cases, head trauma can also lead to a combination of conductive and sensorineural hearing loss.
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Otitis media, an infection or inflammation of the middle ear, typically causes conductive hearing loss due to fluid buildup or pressure behind the eardrum. However, untreated or chronic otitis media can lead to sensorineural hearing loss in rare and severe cases. If the infection spreads from the middle ear to the inner ear, it can damage the cochlea or auditory nerve, resulting in permanent sensorineural hearing loss. This is more likely to occur in chronic or recurrent otitis media cases, especially when complications arise.
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Temporomandibular joint (TMJ) disorders can indirectly contribute to hearing problems but are not typically a direct cause of sensorineural hearing loss. TMJ disorders can cause ear-related symptoms like ear pain, tinnitus (ringing in the ears), or a feeling of fullness in the ear due to the proximity of the jaw joint to the ear canal. However, these symptoms are usually unrelated to inner ear or auditory nerve damage, which are responsible for sensorineural hearing loss. In most cases, TMJ-related hearing issues are temporary and improve with treatment of the TMJ disorder.
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Yes, sensorineural hearing loss can sometimes contribute to headaches. The strain of trying to hear and process sounds, particularly in challenging listening environments, can lead to mental fatigue, stress, and tension, which may result in headaches. Additionally, if sensorineural hearing loss is accompanied by tinnitus (ringing in the ears), the constant noise can also be a source of stress and discomfort, potentially leading to headaches.
Treatment Pathways
Conductive Hearing Loss Treatment
Hearing aids can help with conductive hearing loss if it is ongoing. Depending on the cause of the conductive hearing loss, bone-conduction hearing aids may be the best option. A hearing care professional is the best person to guide you on the appropriateness of hearing aids for your circumstances.
Conductive Hearing Loss Surgery
Depending on the cause of the conductive hearing loss, surgery may be an option to improve hearing. In otitis media, this may involve the insertion of ventilation tubes (grommets) to help keep the middle ear full of air instead of fluid.
In cases of otosclerosis, surgery can remove the fixation of the middle ear bones or use prostheses to replace the middle ear bones.
The type of surgery will depend on the cause of the hearing loss. An Ear, Nose, and Throat surgeon is the best person to advise whether surgery is an option for your conductive hearing loss.
Sensorineural Hearing Loss Treatment
Hearing aids are the primary treatment for sensorineural hearing loss. Hearing aid technology has progressed enormously in recent decades, and they are now much more effective at helping people hear. Your hearing care professional can guide you as to which hearing aids are the best option for you.
Sensorineural Hearing Loss Surgery
If your hearing loss progresses to a point where hearing aids are no longer adequate in helping you hear, you may benefit from a cochlear implant. A cochlear implant bypasses the damaged hair cells in sensorineural hearing loss to stimulate the auditory nerve.
FAQ: Conductive vs Sensorineural Hearing Loss
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Yes, conductive hearing loss can cause tinnitus. Tinnitus, which is the perception of ringing or buzzing in the ears, can occur when there is a disruption in how sound is transmitted through the ear. With conductive hearing loss, blockages or issues in the outer or middle ear, such as earwax buildup, fluid from infections, or damage to the eardrum, can alter sound perception and lead to tinnitus.
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Otosclerosis primarily causes conductive hearing loss. It occurs when abnormal bone growth in the middle ear affects the movement of the stapes bone, which is crucial for transmitting sound to the inner ear. This disrupts the passage of sound from the outer ear to the inner ear, leading to conductive hearing loss.
In some cases, if the otosclerosis progresses and affects the cochlea (the inner ear), it can also lead to sensorineural hearing loss, resulting in a combination of conductive and sensorineural hearing loss. This is called mixed hearing loss.
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Age-related hearing loss (Presbycusis) occurs when the inner ear wears out over time. Therefore, this is a sensorineural hearing loss.
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Noise-induced hearing loss is usually sensorineural. This is especially true of noise-induced hearing loss, which occurs over a long period. However, if you are exposed to a sudden bang like a blast noise, then this can cause damage to your eardrum or middle ear bones and cause conductive hearing loss.
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