What is Conductive Hearing Loss?
Hearing loss typically falls into three categories: conductive, sensorineural, and mixed. Conductive hearing loss refers to problems with the passage of sound from the outer ear, through the middle ear, to the inner ear, which is also known as the cochlea. It can occur due to issues anywhere from the external ear area to internal bone structures.
A broad age range, from young children to the elderly, can experience conductive hearing loss due to various conditions. Causes might be as common as middle ear infections in children, or as serious as a condition caused by a tumor in adults. Therefore, it’s crucial for healthcare professionals like ear, nose, and throat specialists, general doctors, nurses, and hearing specialists to thoroughly understand conductive hearing loss. They often deal with this common type of hearing loss in their practices.
What Causes Conductive Hearing Loss?
Conductive hearing loss comes about when there are issues in the parts of the ear that help sound travel, like the outer ear, ear canal, eardrum, and tiny bones in the ear. Issues with the outer ear and ear cana can be from birth defects that lead to a poorly formed outer ear, or due to blockages in the ear from things like earwax or foreign objects. The eardrum can also be punctured, which can lead to hearing loss. This can happen due to cleaning the ears with cotton swabs, due to pressure changes from deep-sea diving, or from an ear infection.
Conditions of the middle ear that lead to hearing loss include sudden or chronic ear infections, with the latter also known as glue ear. Glue ear is the most common reason children might lose their hearing. While this usually goes away on its own and doesn’t need treatment besides keeping an eye on it, in some kids, the hearing loss may affect their speech and language development. If an adult has glue ear, it could point to a tumor in the area right behind the nose and should be checked out. Another serious reason for hearing loss is a condition called cholesteatoma, which is when skin cells grow in the middle ear or other air-filled areas in the bone around the ear. Although not a tumor, it can damage the area and needs to be surgically removed.
A fault in the tiny bones in the middle ear can also lead to hearing loss. This could be because of a head injury causing these bones to disconnect, or it could be because of a condition like otosclerosis. Otosclerosis happens when the spongy bone in the ear capsule is replaced by hardened bone. This mostly affects the area around the oval window in the ear, leading to the hardening of the stapes (one of the tiny bones) or the ring-shaped ligament. This condition is seen twice as often in women and starts in early adulthood, leading to gradual hearing loss because of the stapes becoming fixed.
Risk Factors and Frequency for Conductive Hearing Loss
Conductive hearing loss, which is a type of hearing impairment, is often seen in younger people due to conditions like otitis media with effusion, a type of ear infection. Research has indicated that this type of hearing loss is prevalent among school-aged children. One study of primary school children revealed 15% had some hearing loss, and of those, nearly 89% were suffering from conductive hearing loss. Similar results were observed in a study of preschool kids in South Africa, where 19% had some hearing impairment and among them, 65% experienced conductive loss. Additionally, the study found 9% of these children were impacted by cerumen (ear wax build-up), which was the cause of hearing loss for 19% of them.
A similar study in Canada showed that 19% of school children from kindergarten to grade 6 had some hearing loss; a staggering 93% of these cases were conductive. The study also found that if there was a hole in the eardrum (tympanic membrane), it contributed to hearing loss in 37% of cases with loss in one ear and 46% of cases with loss in both ears.
In countries with lower to middle incomes, cases of hearing loss due to ear infections can be quite high, up to 26%. Another condition that can lead to conductive hearing loss is Otosclerosis, which is particularly prevalent among the white population (0.04% to 1%) and significantly higher in Asians (5%). It’s also worth noting that this condition can cause hearing loss in both ears in up to 80% of cases. Lastly, in older people, a common cause of hearing loss is presbycusis, a condition related to aging that affects the nerves involved in hearing.
Signs and Symptoms of Conductive Hearing Loss
To identify the cause of hearing loss, a careful look at medical history is crucial. It’s important to find out whether a child has achieved the expected speech and language development milestones on time. Hearing issues can be indicated by repeated upper respiratory infections, as this could mean the child has otitis media with effusion, a condition causing fluid buildup in the middle ear. Hearing loss can sometimes appear as inappropriate behavior or inattention in school.
Other important aspects of a patient’s history – both in children and adults – include when the hearing loss started, any trauma that occurred, and any other symptoms such as dizziness, ear discharge, ear pain, or face muscle weakness. In older patients, nasal discharge and weight loss could indicate a tumor in the nasal space. A child who had ear infections during their first two or three years is at risk for hearing loss that can impact how they speak, resulting in the inability to hear and pronounce certain sounds, like sibilants.
- Speech and language development history
- Incidence of upper respiratory infections
- Behavior or attention issues at school
- Onset of hearing loss and any occurrence of trauma
- Addition symptoms such as vertigo, ear discharge, or facial weakness
- Nasal discharge or weight loss in older patients
- Early life history of ear infections
Family and birth history can help rule out genetic syndromes. Otosclerosis, a bone growth disorder in the ear, usually appears in the early years of adulthood, is more common in women and inherited in families. Patients might say their hearing is better in loud environments. This condition impacts both ears in most cases.
A full examination by an ear, nose, and throat specialist is needed for patients with hearing loss. This includes a close inspection of both ears to spot any abnormalities like blockage, inflammation, or damage to the ear drum. In many cases, a condition called otosclerosis usually leaves the ear drum intact but can sometimes cause a pinkish discoloration. If fluid buildup is noticed in adults, further examination of the nasal space is required.
The Weber and Rinne tuning fork tests can help evaluate the type of hearing loss at a basic level. These tests are more effective for hearing loss on one side and are not as good for mixed hearing loss. Audiometry testing provides a more accurate diagnosis in these cases. When properly conducted, the tests help in identifying the type of hearing loss i.e., conductive or sensorineural.
Testing for Conductive Hearing Loss
Pure tone audiometry is a key test for investigating hearing loss. It helps confirm if there is a hearing loss, measure how severe it is and determine what type of hearing loss it is. In this test, patients wear headphones and are exposed to sounds of varying loudness between 250 to 8000 Hz. The patients need to tell the tester when they can hear the sounds half of the time. This measures the air conduction threshold, which is recorded in decibels.
The bone conduction threshold is determined by placing a device on the bony bump behind the ear, called the mastoid process. There is something called an air-bone gap when the ability to hear via bone conduction is better than air conduction. This is important when the gap is over 10dB and shows conductive hearing loss. Typically, an air-bone gap over 40dB indicates a problem within the small bones of the middle ear rather than only the eardrum.
A Carhart notch is a dip in bone conduction of about 10 to 15dB at 2kHz. This suggests a condition where one of the small bones in the ear, the stapes, is stuck, as seen in a condition called otosclerosis.
Pure tone audiometry is suitable for patients over four years old. There are other tests for younger children, like play audiometry and visual reinforcement audiometry. All these hearing tests involve the patient’s response. Tympanometry is a more objective test that gives useful information about the pressures in the middle ear. It creates a graph showing the eardrum’s ability to move.
If a cholesteatoma (a skin growth that occurs in the middle ear) is suspected, the patient should get a computed tomography (CT) scan of the hard bone around the ears. If needed, magnetic resonance imaging (MRI) with gadolinium may be recommended to rule out tumor conditions of the rear part of the brain, the bone around the ears, and the neck throat areas.
Treatment Options for Conductive Hearing Loss
The treatment for conductive hearing loss, or trouble hearing due to problems in the outer or middle ear, depends on the specific problem that’s causing it. If something is stuck in the ear, it should be removed with care, sometimes with the help of a microscope. Ear wax and debris blocking the ear canal can usually be removed with micro-suction. Holes in the eardrum often heal on their own – doctors only need to check that they’re healing properly about 6-8 weeks after they occur. However, if the hole hasn’t healed by itself, a procedure called a myringoplasty may be needed, but this doesn’t always improve hearing.
Fluid in the middle ear, a condition called otitis media with effusion, usually clears up by itself and doctors just keep an eye on it every three months. However, if the condition doesn’t improve after three months, and the hearing loss in the better ear is over 25-30dB, small tubes called grommets may be inserted into the eardrum to help the fluid drain out. This drains the middle ear to the outer ear canal, rather than to the throat via the Eustachian tubes. Doctors may also remove the adenoids if they’re aggravating the problem. Occasionally, grommets can cause ear infections or rarely, a condition called tympanosclerosis, where scar tissue forms in the middle ear. However, they are still preferred over T-tubes, which have higher rates of complications.
Cholesteatomas, growths in the middle ear, need to be removed surgically. The two main methods for this operation, known as a mastoidectomy, either involve cutting into the ear canal or behind the ear. If there’s been trauma to the ear and the small bones in the middle ear are displaced, a procedure called an ossiculoplasty may be needed. For otosclerosis, a condition where the small bones in the middle ear stiffen, treatment options include simply monitoring the condition, using a hearing aid, and taking fluoride supplements. Surgery may be required if the difference between a person’s air and bone conducting hearing is over 20 dB.
If a person’s conductive hearing loss can’t be improved with medicine or surgery, they can use a hearing aid. There are three main kinds: air conduction hearing aids, bone conduction hearing aids, and bone-anchored hearing aids.
What else can Conductive Hearing Loss be?
When trying to identify the cause of hearing loss that’s due to problems with the ear canal, eardrum, or middle ear, a range of conditions need to be considered. These conditions may affect different parts of the ear, like the ear flap (pinna), the ear canal, the eardrum (tympanic membrane), and the small bones in the ear (ossicles).
Some of the conditions that can cause this type of hearing loss include:
- An underdeveloped or closed ear canal (aural atresia)
- An obstruction in the ear canal
- A hole in the eardrum (tympanic membrane perforation)
- An ear infection (acute otitis media)
- A fluid-filled middle ear (otitis media with effusion)
- A tumor in the back of the nose (nasopharyngeal tumor)
- Growth of skin cells in the middle ear causing a mass or cyst (cholesteatoma)
- An abnormal bone growth in the ear (otosclerosis)
- Separation of the ossicles caused by a head injury
The first step to detect these conditions usually involves a detailed history and physical examination, complemented by a hearing test known as pure tone audiometry. This helps to confirm whether the hearing loss is due to problems with the ear canal or middle ear (conductive hearing loss), or issues related to the inner ear or nerves leading to the brain (sensorineural hearing loss). This distinction guides further testing and treatment strategies.
What to expect with Conductive Hearing Loss
The outlook largely depends on what’s causing the conductive hearing loss. Simple issues like ear wax build-up or otitis media (fluid in the middle ear) can often be resolved with excellent results. Even if the hearing loss can’t be reversed or treated with medicine or surgery, many patients report high satisfaction with the use of hearing aids.
Possible Complications When Diagnosed with Conductive Hearing Loss
Here are some complications that can happen:
- Conductive hearing loss in kids can cause severe delays in their speech and language development, affecting their education if the problem isn’t quickly diagnosed and treated.
- Cholesteatomas, a specific type of skin cyst, can cause serious damage and destruction to nearby structures in the ear.
- Some conditions that cause conductive hearing loss can lead to permanent hearing loss if they’re not treated.
Preventing Conductive Hearing Loss
If you notice that your hearing ability is diminishing, especially if sounds seem muffled or distant, you should know that this can often be treated and it’s important to seek medical advice. Hearing aids can be incredibly helpful if the loss of hearing can’t be remedied. Recognizing this is not only important for individuals, but also for parents and teachers. Sometimes, a child’s misbehavior or lack of attention at school could be due to hearing problems. Early detection can prevent delays in speech and language development.
Another key point to remember is to never use sharp objects to clean your ears. The use of cotton swabs should also be limited to the very outer part of your ear canal. This is because cotton swabs can actually push the wax further into your ear. In most circumstances, there’s no need to use a cotton swab to clean the inside your ear as wax normally works its way out naturally.