Conductive hearing loss is caused by a problem in the outer or middle ear that prevents sound from reaching the inner ear. Environmental sound travels through the outer ear to the middle ear, from which it is transmitted to the inner ear. From the inner ear, sound is sent to the brain for interpretation. In a person with conductive hearing loss, this normal hearing process is interrupted. If the problem is in the outer ear, environmental sound cannot enter the ear. If a problem causes hearing loss in the middle ear, external sounds can be picked up by the outer ear, but the sound is blocked in the middle ear and does not reach the inner ear. Even if the inner ear is functioning perfectly, the lack of sound input from the outer or middle ear prevents it from sending signals to the brain. Conductive hearing loss can be bilateral or unilateral. Bilateral conductive hearing loss is hearing loss that affects both ears. Bilateral hearing loss can be symmetrical or asymmetrical. Symmetrical bilateral hearing loss is hearing loss with identical symptoms in both ears. Asymmetrical bilateral conductive hearing loss occurs when symptoms are more severe in one ear than in the other.
What is unilateral conductive hearing loss?
Unilateral conductive hearing loss is hearing loss that affects only one ear. In this case, hearing remains within normal limits on one side, while the other ear is affected. This is also referred to as single-sided hearing loss. People with unilateral conductive hearing loss have a "good" ear (the healthy ear) that they rely heavily on for hearing. The affected ear may have reduced hearing or be completely unable to hear. Unilateral conductive hearing loss can be mild, severe, or profound. A severe or profound form is called total unilateral hearing loss. People with unilateral conductive hearing loss have difficulty determining the direction from which a sound is coming and often struggle to distinguish speech from background noise.
Symptoms of unilateral conductive hearing loss
Symptoms of unilateral conductive hearing loss most often occur in the affected ear. Hearing in the healthy ear is usually normal. The most common symptoms are:
1. Difficulty locating sounds
Most people with unilateral conductive hearing loss have difficulty localizing a sound, i.e., identifying where it comes from. Sound localization plays an essential role in our urban survival. Indeed, reacting effectively to our environment and the people around us is, to a large extent, a matter of survival. In some dangerous situations, it is necessary to identify the exact direction from which a sound is coming to avoid danger. This is the case, for example, with an approaching car, a falling object, a collapsing building, an animal's cry, or a gunshot. New electric cars pose an additional problem for people with hearing loss, as it can be difficult, if not impossible, to hear a vehicle approaching from a given direction. In addition to allowing the identification and avoidance of the direction of danger, sound localization is also necessary for conversations. When someone calls you, your ability to respond quickly depends on how fast you locate them. And if you are looking for an object or someone, the sound you hear helps you find them easily.
2. Difficulty following group conversations
Due to this inability to localize sounds, people with unilateral conductive hearing loss have difficulty following group conversations. In a group, everyone takes turns speaking, which can be problematic in cases of unilateral hearing loss. Indeed, when the conversation shifts from one person to another, the person with hearing loss must first locate the new speaker. If they don't spot them immediately, they risk missing the beginning of each intervention. Their understanding of what is being said is thus reduced. Often, they will complain of having difficulty hearing in meetings, when the real problem is that they miss information while trying to figure out who is speaking.
3. Difficulty understanding speech in noise
Background noise is ambient noise that is not the sound you are paying attention to. A common difficulty for people with conductive hearing loss is precisely understanding speech in the presence of background noise. Even when speech is amplified to improve its audibility, the problem persists. Most people with hearing loss cannot communicate effectively in noise, as it interferes with the sound they are trying to focus on, leading them to misunderstand what is being said.
4. Difficulty hearing with the affected ear
Unilateral conductive hearing loss affects only one ear. Hearing in this ear can be muffled or non-existent, depending on the severity of the hearing loss. People with unilateral conductive hearing loss must turn their healthy ear towards the sound source to hear properly. If you start a conversation with someone with conductive hearing loss, you may see them change position before responding. This movement aims to orient their good ear towards your voice to understand you better.
Causes of unilateral conductive hearing loss
As previously mentioned, unilateral conductive hearing loss is due to a problem in the outer or middle ear. Possible causes are discussed below.
1. Otitis media
Otitis media occurs when fluid builds up in the middle ear. This buildup is caused by swelling or obstruction of the Eustachian tubes. The Eustachian tubes are small canals that connect each ear to the back of the throat. They are responsible for draining fluid from the middle ear. When the Eustachian tube in one ear fails to drain this fluid, otitis media can develop. Obstruction or swelling of the Eustachian tube can be caused by excess mucus, sinusitis, a cold, or allergies. Children are more prone to otitis media than adults, as they are more exposed to Eustachian tube dysfunction. In children, these tubes are shorter and narrower than in adults, which slows the drainage of fluid from the middle ear. Bottle feeding and pacifier use also increase the risk of otitis media in children. However, adults exposed to cigarette smoke, climate changes, and altitude variations are also prone to otitis media. In addition to the conductive hearing loss that appears in the infected ear, other symptoms may occur: a feeling of pressure in the affected ear, irritability in infants, discomfort in the affected ear, and purulent discharge.
2. Earwax impaction
Earwax buildup is a common cause of single-sided conductive hearing loss. The ear canal produces an oily substance called cerumen (earwax). This wax protects the ear canal from microorganisms, foreign particles, and water that could cause infection. Normally, earwax naturally moves out of the ear canal to the ear opening. But in some cases, the ear produces more earwax than it can eliminate. Over time, this excess accumulates and hardens. Trying to clean the ear with cotton swabs can push accumulated earwax deeper into the ear canal and create an impaction. This impaction prevents sound from reaching the middle ear, leading to hearing loss. If the accumulation affects only one ear, the conductive hearing loss is unilateral. Other symptoms of unilateral conductive hearing loss related to earwax impaction include severe pain in the affected ear, a feeling of fullness in the ear, and tinnitus. If the earwax is not removed quickly, it can cause otitis media and lead to more severe symptoms: fluid discharge, dizziness, a bad smell from the affected ear, and fever.
3. Ruptured eardrum
A ruptured eardrum is also called tympanic perforation. It is a small hole or tear in the eardrum. The eardrum is a thin membrane located between the external ear canal and the middle ear. It vibrates when sound waves enter the ear. This vibration is an essential link in hearing: without it, sound is not transmitted to the middle ear, from where it is then sent to the inner ear. When the eardrum is torn or perforated, it can no longer vibrate from sound waves, causing hearing loss. This tear or hole can have the following origins:
Pressure changesWhen the pressure outside the ear differs from the pressure inside, the eardrum can tear. This is called barotrauma. A direct and violent blow to the ear, scuba diving, shock waves, driving at high altitudes, and air travel can cause barotrauma.
Otitis media Otitis media that causes fluid to build up behind the eardrum can lead to its rupture. This is due to the pressure exerted on the eardrum by the accumulated fluid.
Injury or trauma Any trauma or injury to the ear or side of the head can cause a ruptured eardrum. This trauma can result from a blow to the head, a fall on the ear, inserting objects into the ear, a car accident, etc.
Acoustic trauma Acoustic trauma refers to damage to the eardrum caused by exposure to loud noise. Any exposure to loud noise, whether sudden or prolonged, should be avoided: beyond the eardrum, it can also damage the hair cells of the inner ear.
Unilateral conductive hearing loss caused by a ruptured eardrum is often temporary. In most cases, the tear or hole closes naturally within a few weeks. A ruptured eardrum is accompanied by symptoms such as bloody, clear, or purulent discharge from the affected ear, as well as pain.
4. Otitis externa
Otitis externa is an infection of the ear canal and the external ear opening. A common form of otitis externa is "swimmer's ear." It gets its name because it is caused by exposure to moisture and is common in swimmers. When you swim or wash, water enters the ear. If this water remains in the ear canal, it creates an environment conducive to bacterial growth. In addition to the presence of moisture in the ear, otitis externa can be caused by damage to the thin layer of skin lining the ear canal. The use of headphones, cotton swabs, and repeated scratching can damage this fragile skin. Damaged or inflamed skin then becomes a breeding ground for bacteria. Skin irritations and eczema can also cause otitis externa. In addition to the general symptoms of unilateral conductive hearing loss, people whose hearing loss is due to otitis externa experience swelling and redness of the ear. Other signs may appear: pain or discomfort in the affected ear, abundant discharge, muffled hearing on that side, itching, a feeling of warmth, and pus discharge.
5. Microtia
Microtia is a congenital malformation of the external ear. Children born with microtia have an underdeveloped auricle, or external ear. Microtia is a common cause of congenital unilateral conductive hearing loss. It usually occurs during the first trimester of pregnancy, during the development of the fetal ear. Although its exact cause remains unknown, it has been associated with drug or alcohol consumption during pregnancy, a diet poor in carbohydrates and folic acid during this period, and the use of acne treatments. Due to the underdevelopment of the affected ear and the severity of the malformation, total hearing loss is possible.
6. Anotia
Anotia, which means "absence of ear," is a rare cause of unilateral conductive hearing loss. It is a congenital malformation characterized by the absence of the auricle and the narrowing or absence of the ear canal. Anotia is often considered a severe form of microtia. As with microtia, its exact cause is not known. But it occurs during the first few weeks of pregnancy. The reference treatment for anotia is complete ear reconstruction. This procedure is usually performed by a multidisciplinary team of specialists, consisting of a plastic surgeon, a speech therapist, and an otolaryngologist.
Conclusion
Most cases of unilateral conductive hearing loss discussed above are not permanent. In other words, hearing can return to normal if the underlying cause is treated. With the exception of microtia and anotia, no surgery is necessary to treat the causes mentioned above. Some require medical attention, while others, such as Eustachian tube dysfunction or a ruptured eardrum, heal spontaneously. If you have difficulty hearing in one ear, we advise you to consult a doctor. Do not try to treat yourself without their approval. By trying to solve the problem, you risk making it worse: it is therefore better to act with the approval and under the supervision of your doctor. Have you ever suffered from unilateral conductive hearing loss? What symptoms did you experience? Share your experience with us.
