What is neural hearing loss?
This is loss of hearing that results from damage to the auditory nerve, which transmits sounds from the inner ear to the brain and is also called the vestibulocochlear or eighth nerve.
People with this type of hearing loss not only have trouble hearing, but often find it difficult to make out the words other people say. Usually, the louder the sound, the more difficult it is for people with the condition to understand speech and distinguish one word from another.
Neural hearing loss can occur in both children and adults. It is the least common type of hearing problem. Of all types of hearing loss, the neural type is the most likely to be caused by a serious illness.
What causes neural hearing loss?
In children, the auditory nerve can be damaged by
- Difficulty hearing.
- Difficulty making out speech.
- Decreasing ability to distinguish words as the speech grows louder.
such diseases as mumps, rubella, and meningitis. Hereditary neurological disorders, such as a rare childhood form of multiple sclerosis, may also be associated with neural hearing loss. The nerve may also be damaged when chronic infection spreads from the middle ear to the inner ear and the brain. Certain infections (particularly rubella) contracted during pregnancy can harm the fetus, causing neural hearing loss in infants.
In adults, neural hearing loss can be caused by tumors or viral infections, including flu and herpes zoster or shingles (a painful skin condition that occurs when the chickenpox virus is reactivated). The auditory nerve can be damaged if the part of the brain through which it runs is injured. Sometimes, nerve deterioration is associated with aging.
How is neural hearing loss diagnosed and treated?
The goal of diagnosis is to establish the cause of the disorder and distinguish it from other types of hearing loss. These types include conductive hearing loss, which is caused by mechanical obstruction in the middle or external ear, and sensory hearing loss, which
results from deterioration of the cochlea, the snail-shaped structure in the inner ear. Treatment depends on the underlying cause of the hearing loss. If the disorder is caused by a tumor, the growth may be surgically removed. If the nerve damage stems from an infection, antibiotics may be prescribed.
If the auditory nerve is not severely affected, hearing may be restored after treatment. However, if the nerve damage is irreversible, a hearing aid may help.
What can I do myself?
There is no self-treatment for neural hearing loss.
When should I see my doctor?
See a doctor without delay if you have sudden or progressive hearing loss. Although there is no reason for concern in most cases, impaired hearing may sometimes indicate a serious disorder. Infants with a high risk of neural hearing loss — for example, if the mother had a viral illness during pregnancy — should have hearing tests soon after birth.
What will the doctor do?
The doctor starts by testing your hearing to establish the degree of hearing loss. He or she then attaches a sound-producing device, such as the stem of a tuning fork, to your head. In this case, sound vibrations are transmitted directly to your brain without passing through the middle or external ear. If you can hear sounds emanating from the sound source attached to your skull, you have conductive hearing loss, which means that the problem lies in the middle or external ear. If your hearing is
The auditory nerve arises in the lower portion of the brain.
as impaired with the sound conductor attached to your head as it is when the sound is carried through the air, your hearing loss is sensory or neural.
The doctor then orders a thorough medical examination to look for the cause of the hearing loss, which may include a computed tomography (CT) scan of the head. Further tests are performed to distinguish sensory hearing loss from neural hearing loss. The most revealing of these is known as brainstem response audiometry. In this method, the waves generated by the auditory nerve are recorded and examined for signs of weakness.
The course of neural hearing loss
Hearing loss due to a mother's illness during pregnancy is present at birth. When the disorder is caused by a hereditary disease, it can be present at birth or develop in childhood or early adulthood. Patients with hereditary neurological diseases usually have other symptoms in addition to hearing loss. They may, for example, exhibit poor muscle coordination. When the auditory nerve is damaged by infection or trauma, hearing loss may occur suddenly and is often accompanied by dizziness. When the nerve is compressed by a tumor, hearing loss generally affects one ear and develops gradually.
Is neural hearing loss dangerous?
This type of hearing loss is dangerous because it may be irreversible. It can also be associated with life-threatening disorders.
What can I do to avoid neural hearing loss?
- Get prompt treatment for infectious diseases.
- Treat chronic middle-ear infections to prevent their spread to the inner ear and auditory nerve.
- Be doubly cautious in avoiding infectious illness during pregnancy.