What Is Sensorineural Hearing Loss?
The ears have three portions, namely the outer, middle, and inner ear. Sensorineural hearing loss (SNHL) occurs when the inner ear is damaged. It is referred to as sensorineural because the inner ear and hearing nerve need to work together for proper hearing. SNHL accounts for around 90 percent of hearing loss cases. It might be permanent and can be mild, moderate, severe, and total.
Sensory hearing loss is usually a consequence of damaged cochlear hair cells. These hair cells can be abnormally formed at birth or damaged after birth. Some of the causes include infections, certain drugs, and genetic mutations. Neural hearing loss is a consequence of a damaged cochlear nerve. This nerve is responsible for the transmission of impulses to the brain. SNHL usually results in a gradual deterioration of a person’s hearing over many years and can be accompanied by symptoms such as tinnitus (ringing in the ears) and vertigo. SNHL can be either:
-
Unilateral - Affecting only one ear.
-
Bilateral - Affecting both ears.
The common kinds of sensorineural hearing loss are presbycusis (age-related) and noise-induced hearing loss. The frequent symptoms of SNHL include the inability to distinguish voices in a noisy environment, difficulty following a conversation over the phone, a few sounds that are very loud, feeling that people are mumbling, and difficulty following and understanding speech. The symptoms are common to all types of hearing loss, so it is important to consult a doctor and run necessary tests to rule out other causes and conditions.
Diagnosis is generally made by an audiologist with the help of an audiogram, tympanometry, and speech audiometry. As of now, there is no cure for SNHL, and treatment is done with the help of hearing aids. In severe cases, a cochlear implant is indicated.
What Are the Different Types of Sensorineural Hearing Loss?
There are three types, these are
-
Bilateral Hearing Loss: This can be caused due to genetics, exposure to loud noises, or diseases like measles.
-
Unilateral Hearing Loss: This condition usually affects only one ear. This can be caused by a tumor, Meniere’s condition, or loud sounds.
-
Asymmetrical Hearing Loss: In this condition, both ears will be affected, but one ear will be worse than the other.
What Causes Sensorineural Hearing Loss?
There are many different conditions which can damage the inner ear, but they are broadly grouped into two types:
Congenital: Congenital SNHL is a type of hearing loss seen at birth. Reasons include -
-
Low birth weight.
-
Premature birth.
-
Inherited deafness.
-
Maternal infections such as rubella and German measles during pregnancy.
Acquired Hearing Loss: Acquired SNLH is developed at a later stage in life, unlike the congenital type. Reasons include -
-
Presbycusis (Age-Related Hearing Loss) - It usually affects both ears in people between the ages of 65 and 74 years.
-
Noise-Induced Hearing Loss (NIHL) - Prolonged exposure to loud noise higher than 85 decibels or exposure to a single loud noise like gunfire or explosion.
-
Viral Infections - Such as measles, meningitis, and mumps.
-
Other Disorders - Such as Meniere’s disease, bacterial meningitis, diabetes, and inflammatory ear conditions.
-
Acoustic Trauma - Due to exposure to loud sounds such as firearms or explosions.
-
Medicines - Ototoxic drugs such as certain antibiotics, chemotherapy drugs, and anti-inflammatory drugs.
-
Tumors - Ear tumors and growths may also affect hearing health.
What Are the Signs and Symptoms of SNHL?
-
Those with sensorineural hearing loss can hear muffled sounds but not understand the context of what is being spoken, and this leads to gradual isolation.
-
Problems with hearing in a noisy environment.
-
There is reduced sensitivity to soft sounds. This causes problems with communication and interpersonal skills. It also affects learning and school performance in young children.
-
Balance problems.
-
Perception of loud sounds is altered, causing social withdrawal and loneliness.
-
Tinnitus (ringing or buzzing sound in the ear).
-
Brain stroke.
-
Iodine deficiency and hypothyroidism (underactive thyroid).
-
Dizziness.
What Is the Pathophysiology of Sensorineural Hearing Loss?
The abnormal formation or function of the hair cells present in the inner ear results in sensory hearing loss. Any damage to the vestibulocochlear nerve or the eighth cranial nerve results in neural hearing loss.
When Is the Right Time to Test The Child’s Hearing?
It is not easy to know if a child has hearing problems or not. Children can develop hearing loss due to infections at birth. In the following situations, it is best to get the children tested for hearing loss:
-
If the child does not look like they understand the language.
-
If they do not attempt to form words.
-
If they develop frequent ear infections.
-
If they have balancing problems.
-
If they do not get startled by sudden noises.
How Is Sensorineural Hearing Loss Diagnosed?
The specialist will ask you questions to understand the symptoms and medical history. Then, the specialist will perform a physical examination and ask about any previous medical conditions and the medications that the child is currently taking. The tests include:
-
Physical Examination - The child will have to cover one ear at a time while the doctor plays sounds at different volumes. They will also conduct tests using a tuning fork, which measures the vibrations in the ear.
-
Audiometry - This test can detect hearing loss more accurately. Here, a number of different sounds at different volume levels are sent individually to each ear.
-
MRI - To check for any abnormalities in the ear, such as cysts or tumors.
How is Sensorineural Hearing Loss Treated?
A thorough evaluation of the extent of the hearing loss must be conducted by a hearing health professional who can diagnose the actual type of hearing loss and suggest appropriate treatment.
In the case of bilateral hearing loss, which is mild to moderate, hearing aids may help. However, in case of severe hearing loss, even using hearing aids will not help as they would just amplify the distorted sounds, and in the presence of background noise, it would lead to more confusion and frustration.
In that case, cochlear implants may be the solution. A cochlear implant is an electronic device that is placed in the ear surgically and stimulates the hearing nerve by converting sound waves directly to electrical impulses.
Is This Condition Permanent?
Unfortunately, Sensorineural hearing loss is permanent because it is impossible to repair or replace the hair cells in the inner ear. Hearing does not recover over time on its own. The percentage of hearing that has already been lost will remain permanent. Some types of sudden sensorineural hearing loss (SSHL) can be cured with immediate medical help.
What Is the Prognosis of SSHL?
The prognosis of SSHL depends on the extent and cause of the condition. This is a very common form of permanent hearing loss.
Conclusion
SSHL is a natural part of aging in many people, but some loud sounds can damage the inner ear or the auditory nerve permanently. Some causative factors of this condition are loud sounds, genetics, tumors, or the aging process. It is not a serious condition, but it can impact a person's normal life.
