Conductive hearing loss is a type of hearing loss caused by the inability of sound to pass through the outer or middle ear to reach the inner ear. In people with conductive hearing loss, the inner ear works perfectly, but because no sound reaches it from the outer and middle ear, hearing loss results. This is because no sound signals are transmitted by the inner ear to the brain to be interpreted. In a normally functioning ear, the outer ear picks up sounds from the environment and transmits them to the eardrum of the middle ear. The middle ear then transmits the sound to the inner ear, from where it is sent to the brain. In people with conductive hearing loss, this normal flow of sound is interrupted, either in the outer ear or in the middle ear. In most cases of conductive hearing loss, the problem is in either the outer ear or the middle ear. Cases where both the outer ear and the middle ear malfunction at the same time are quite rare. If the outer ear is damaged or the ear canal is blocked, the transmission of sound to the middle ear becomes difficult. Even if the middle ear is healthy enough to receive and transmit sounds, it cannot do so properly since no sound reaches it from the outer ear. Conductive hearing loss can be unilateral or bilateral. Unilateral conductive hearing loss affects only one ear. If a person suffers from conductive hearing loss in both ears, it is called bilateral conductive hearing loss. Bilateral conductive hearing loss can itself be symmetrical or asymmetrical. "Symmetrical" means that the severity of symptoms is identical in both ears. Asymmetrical bilateral conductive hearing loss is characterized by more severe symptoms in one ear than in the other. Most people with conductive hearing loss experience low-frequency hearing loss. This article tells you everything you need to know about low-frequency conductive hearing loss and possible treatments.
What is low-frequency conductive hearing loss?
Low-frequency conductive hearing loss, also known as reverse slope hearing loss, is a rare form of hearing loss that affects people with conductive hearing loss more than those with other types of hearing loss. It is called reverse slope hearing loss because of the shape it draws on the audiogram. Low-frequency conductive hearing loss is defined as the inability to hear low-pitched sounds (sounds below 2,000 hertz (Hz)). Affected people have difficulty perceiving low-pitched sounds such as bass in music, male voices, or thunder. Low-pitched vowels are also more difficult to hear than low-pitched consonants. Low-frequency conductive hearing loss is characterized by sensitivity to speech volume. If the volume is amplified, the affected person will hear low-pitched sounds better. People with low-frequency conductive hearing loss understand speech normally. They even tend to have excellent language skills, as they are more sensitive to high-pitched sounds. The only difficulty they encounter concerns low-pitched sounds, and this is why most of them prefer face-to-face conversations. These exchanges allow them to hear better. This is not the case, however, when they are spoken to in noisy or crowded environments. Low-frequency conductive hearing loss can range from mild to profound. People with a mild form do not always know they have it. It can go unnoticed for years or until an audiological examination is performed, as it is so discreet. It is quite different for people with severe or profound forms. Their symptoms are more marked and easily detectable.
Symptoms of low-frequency conductive hearing loss
Like any other form of hearing loss, low-frequency conductive hearing loss manifests itself through certain symptoms. These symptoms and their severity vary from person to person, as no two cases of hearing loss are ever identical. If you suffer from low-frequency conductive hearing loss, you may experience some or all of the symptoms below:
1. Difficulty hearing low-pitched sounds
As its name suggests, low-frequency conductive hearing loss prevents the perception of low-pitched sounds. Indeed, these sounds are below 2,000 hertz, the frequency that people with this type of hearing loss cannot hear. Among the low-pitched sounds that these people cannot perceive: male voices, the hum of a refrigerator, thunder, bass in music, the rumble of trucks, car and airplane engines, and vowels. This hearing loss is limited to low-pitched sounds, as affected people perceive very high-pitched sounds surprisingly well, which others do not even notice. They hear high-pitched sounds such as women's and children's voices without difficulty.
2. Difficulty following group conversations
People with low-frequency conductive hearing loss prefer one-on-one conversations to group conversations. They have difficulty following collective exchanges, as these create more complex sound environments. A group conversation involves different voice pitches and several people speaking at the same time. It then becomes difficult for the hearing-impaired person to distinguish the voices around them. Moreover, due to this mix of sound pitches, high-pitched voices are perceived faster than low-pitched voices. The hearing-impaired person may thus miss important information. This difficulty in following the conversation can lead them to misunderstand what is being said, to constantly ask for repetition, or to raise their voice during the exchange. This can be embarrassing for them and, in most cases, they choose to withdraw from or avoid group conversations.
3. Difficulty hearing in noisy environments
Most people with low-frequency conductive hearing loss have difficulty hearing in noisy environments. Like group conversations, these environments create a complex listening situation. They avoid conversing in noisy places or places rich in background noise: surrounding conversations, ambient music, noises from appliances such as coffee machines, refrigerators, or cash registers. Noisy places such as clubs, bars, cafes, and restaurants generally mix sounds of very different pitches. The hearing-impaired person will more easily pick up high-pitched sounds than low-pitched sounds. If their interlocutor has a low voice, they may not hear what is being said to them. They have difficulty filtering competing sounds to focus on the conversation. To communicate effectively with them in a noisy place, it may be necessary to speak to them face-to-face and loudly. Inviting them aside, to a quieter place, for a one-on-one exchange is also very helpful.
4. Difficulty hearing on the phone
Phone calls are a particularly difficult form of conversation for people with low-frequency conductive hearing loss. Indeed, most telephone conversations (whether male or female voices) are transmitted at low or medium frequencies. The hearing-impaired person may constantly ask for repetition or ask their interlocutor to speak louder. Most of the conversation escapes them, as they only perceive snippets of it. This is why most of them prefer face-to-face exchanges to phone conversations. When face-to-face is not possible, they often prefer written messages.
Causes of low-frequency conductive hearing loss
Low-frequency conductive hearing loss is often due to a problem with the outer ear or middle ear. Here are the two most common causes
1. Otosclerosis
Otosclerosis is an abnormal hardening of the ear tissues caused by bone remodeling of the middle ear. Bone remodeling is a natural process that continues throughout life. It involves the renewal of bone tissue, with old tissue being replaced by new tissue. Otosclerosis occurs when abnormal remodeling hinders the ability of sound to travel from the middle ear to the inner ear.
The ossicles affected by otosclerosis are the stapes. The stapes normally vibrates when sound reaches it, but otosclerosis locks it in a fixed position, preventing it from vibrating. This stiffness, or absence of vibration, makes it impossible for sound to pass from the middle ear to the inner ear, resulting in conductive hearing loss. The exact cause of stapes stiffening remains unknown, but some studies suggest a link to an immune disorder, a previous measles infection, or stress fractures of the bone tissues surrounding the ear. Hearing loss caused by otosclerosis is often progressive and begins in only one ear. It usually begins with the inability to hear low-pitched sounds. It is also accompanied by symptoms such as tinnitus (ringing in the ear), dizziness, and balance problems. Otosclerosis can be treated with surgery and hearing aids. The surgical procedure, called stapedectomy, involves inserting a prosthesis into the middle ear to bypass the abnormal bone and allow sound waves to reach the inner ear.
Hearing aids can also be used to amplify sound when otosclerosis is mild. To date, there is no medication for otosclerosis.
2. Serous otitis media
Serous otitis media corresponds to an accumulation of fluid behind the eardrum, due to an incomplete resolution of acute otitis media or to the obstruction of the Eustachian tube without infection.
Serous otitis media is more common in children aged three months to three years and often results from a blocked Eustachian tube or a previous ear infection. It rarely causes pain, but can cause other symptoms such as a feeling of pressure or fullness in the ear and low-frequency conductive hearing loss. Even if the patient feels no pain, the eardrum (or tympanic membrane) often has an amber or grey tint on examination. Mild to severe retraction is observed, displacement of the light reflex, and accentuated anatomical features. Air bubbles or a fluid level may also be visible through the tympanic membrane. Only the doctor can observe all these signs. Most cases of serous otitis media resolve without any treatment. Hearing usually returns to normal within two to three weeks.
If there is no improvement after one to three months, an intervention consists of placing a tympanostomy tube in the middle ear. The middle ear is ventilated three to four times per minute. The goal is to open the Eustachian tube and allow oxygen to be absorbed by the vessels in the middle ear mucosa.
Once the accumulated fluid is evacuated, the eardrum can vibrate normally and allow sound transmission again.
Treatments for low-frequency conductive hearing loss
There is no universal treatment for low-frequency conductive hearing loss. In most cases, hearing loss disappears when the cause of the problem is treated. If low-frequency conductive hearing loss is due to otosclerosis, treating it surgically can restore normal hearing. The same applies to low-frequency conductive hearing loss caused by serous otitis media. This often disappears without treatment and, as a result, hearing returns to normal. If, however, the low-frequency loss proves irreversible, hearing aids will be prescribed. Hearing aids are the reference treatment for low-frequency conductive hearing loss that persists for too long.
Hearing aids amplify low-pitched sounds while maintaining high-pitched sounds at a normal level. Hearing aids are medical devices and should only be fitted by an experienced audiologist. Since no two cases of hearing loss are ever identical, all hearing aids are customized to meet your specific hearing needs. Due to the complexity and rarity of low-frequency conductive hearing loss, fitting and adjusting hearing aids may require several sessions before they exactly match the characteristics of your hearing loss.
Conclusion
Even if low-frequency conductive hearing loss is less disabling than high-frequency hearing loss, it nevertheless has repercussions on the life of the affected person. This is why it is important to consult a professional. Given the rarity of this condition, only an audiologist will be able to offer you the ideal solution. Have you ever suffered from low-frequency conductive hearing loss? What impact did it have on your ability to communicate? Share your experience with us in the comments.
