What is sensorineural hearing loss?

Causes of sensorineural hearing loss

While the most common cause of SNHL is age-related presbycusis, which is caused by the degeneration of tiny hair cells in the inner ear, there are several other causes. Some of these can be prevented, while others are simply a matter of genetic predisposition.

Congenital

Congenital sensorineural hearing loss is something a person is born with. Generally, this hearing loss is present at birth in roughly one out of every 1,000 newborns. Babies who are born prematurely or spend extended periods in the NICU are more likely to have congenital hearing loss due to issues like lack of oxygen or maternal infections during pregnancy.

Genetic syndromes can also cause congenital hearing loss, such as Pendred Syndrome (the most common), which creates SNHL as well as an enlarged thyroid.

Acquired

Unlike congenital SNHL, acquired hearing loss occurs after birth or sometime during a person’s life. It can be caused by aging, head trauma, and prolonged exposure to loud noises. Additionally, acquired SNHL can be caused by medications like aspirin and loop diuretics, as well as infections such as measles.

Hearing and balance disorders, such as Ménière’s Disease, and disorders like Parkinson’s can also create SNHL. Ménière’s Disease, in particular, is a more common cause of acquired SNH, which is typically unilateral, and the inner ear disease also leaves the individual with vertigo and tinnitus.

Genetic Factors

Like many other health concerns, sensorineural hearing loss can often have genetic factors. It’s common for SNHL to run in families, even if it’s not noted at birth.

One common genetic SNHL condition is late-onset sensorineural hearing loss, which usually happens after childhood. Another rare type of SNHL is cookie bite hearing loss, a mid-frequency hearing loss, which is hereditary and affects less than 1% of the SNHL population.

Symptoms and diagnosis of sensorineural hearing loss

Common symptoms

The most common symptoms of SNHL include comprehension issues, difficulty hearing high pitches, dizziness, a feeling of pressure in the ear, muffled hearing, and tinnitus, or a constant ringing or buzzing sound.

How is SNHL diagnosed?

Just presenting with potential symptoms of sensorineural hearing loss isn’t enough to diagnose it. Instead, the individual should undergo official diagnostic exams to pinpoint the cause of hearing loss.

Audiometry tests

An audiometry test is a medical test done by a doctor or audiologist that evaluates hearing ability and determines what kind of hearing loss you may be suffering from. Different types of these tests include pure-tone audiometry, which plays frequencies and the patient says whether they can hear them or not, and speech audiometry, which presents a patient with spoken words at varying volumes.

Another audiometry test is tympanometry, which measures the movement and pressure of the eardrum and the bones in the middle ear to determine sound transmission. And, finally, there is the auditory brainstem response test or ABR, which measures the brain’s electrical activity in response to various sounds.

MRI and CT scans

Both CT and MRI scans are effective tools for determining hearing loss when the loss is caused by damage to the tissue or bone in the inner ear. This can be helpful for patients with SNHL looking into potential cochlear implants and if the existing cochlea is suitable for the surgery. These scans can see the interior of the patient’s inner ear to identify the damage and determine how significant the SNHL could be.

Treatment options for sensorineural hearing loss

Hearing aids

Hearing aids are an excellent treatment option for mid to profound SNHL. They help a patient hear more clearly by amplifying specific pitches to improve speech clarity. There are a few types of hearing aids:

• Behind-the-ear: The receiver is placed behind the ear with just a small tip that enters the ear canal
• In-the-ear: This device sits in the ear opening itself and takes up most of that space. It’s larger than in-the-canal hearing aids.
• Receiver-in-the-ear: Similar to a behind-the-ear device, the receiver-in-the-ear loops over the back of the ear as well.  This hearing aid loops around the back of the ear with the amplification device placed inside the ear.
• In-the-canal: Like the in-the-ear hearing aid, this device sits deeper inside the ear canal. It’s smaller than its counterpart and goes just inside the ear opening.
• CROS/BiCROS: CROS, or Contralateral Routing of Signals, and BiCROS, or Bilateral Contralateral Routing of Signals, are hearing aids for those suffering from asymmetric hearing loss in which one ear is unusable for hearing. For the patient to have access to sounds from the unusable ear’s side, CROS and BiCROS devices wirelessly send the incoming sound to the better hearing ear.

Cochlear implants

A cochlear implant may be a good solution for individuals with more profound hearing loss. These implants serve as a replacement cochlea, transmitting electrical signals caused by sound to the brain to bypass the faulty inner ear.

Assistive listening devices

Although hearing aids and cochlear implants are both assistive listening devices, there are additional devices to consider to help with hearing loss.

For instance, audio induction loops can connect to an individual’s hearing aid to transmit sound directly to them. There are also devices such as amplified telephones, alerting devices, personal amplification systems, and infrared systems, which are most often used in public settings.

Medical and surgical interventions

In addition to the more common cochlear implant surgery, there are a few other surgeries that can help restore hearing loss in SNHL patients. These include auditory brainstem implants, which transmit signals directly to the brainstem, a myringotomy, which installs a tube into the eardrum, or a stapedectomy, which places a prosthetic bone in the inner ear to correct sound transmission.

For individuals living with SNHL, assistive devices and surgical interventions can dramatically improve quality of life. Not only does it improve one’s ability to communicate, but the reduction in hearing loss may also improve cognitive function, according to the latest research from the University of Melbourne.

The best way to avoid preventable noise-induced SNHL is to be mindful of loud noises. You should always wear ear protection when attending loud worksites or concerts, avoid listening to headphones at any level higher than 60%, and reduce your listening time to 60 minutes.