Mixed Hearing Loss Causes
What causes mixed hearing loss, and is it correctable? To provide a thorough diagnosis, it’s important to understand the causes of mixed hearing loss and how it may happen.
Hearing loss can occur early, from the degeneration of aging or environmental factors such as prolonged exposure to loud noise. Other causes still may stem from severe disease, head trauma, or other factors. And anyone who’s experienced even temporary hearing loss knows that the experience can be quite unsettling.
Mixed hearing loss is defined as a combination of damage to the outer or middle ear, coupled with damage to the inner ear and auditory nerves.
To understand Mixed Hearing Loss and the potential for permanent damage, understanding the three types of hearing loss is crucial for treatment. A detailed examination should discover what may cause every kind of damage and solutions for each one.
The Three Types Of Hearing Loss
There are three most common forms of hearing loss are Conductive, Sensorineural, and Mixed. Causation ranges from natural causes to the more serious such as disease or trauma to the head. Sometimes hearing loss can be temporary, and a simple evaluation will determine if it’s temporary and possibly for the duration of the damage or whether it’s more serious. Having an audiologist examine your hearing is essential for hearing health.
Regardless of what type of hearing loss experience may have occurred, the loss of any level of hearing can be both uncomfortable and disorienting for the sufferer.
The main types of hearing loss are conductive, sensorineural, and mixed hearing loss.
Typically conductive hearing loss happens when there is damage to the outer or middle-ear, while sensorineural occurs when damage is to the inner-ear.
- Conductive Hearing Loss: With conductive hearing loss, hearing is difficult, sounds are muffled, and loud sounds are incredibly tricky. This type of experience can be disorienting and discomforting for the sufferer, but it is often easier to diagnose and treat.
- Sensorineural Hearing Loss: Sensorineural hearing loss (SNHL) makes soft sounds challenging to hear and often leads to permanent hearing loss. This type of damage is more subtle than Conductive Hearing Loss for the sufferer but can be just as disorienting as Conductive Hearing Loss. This is a more severe form of hearing loss and often leads to some level of permanent damage.
- Mixed Hearing Loss: Mixed Hearing loss is when there is damage to the hearing in both the outer/mid-ear and the inner-ear. There is a combination of blockage (conductive) and inner-ear or auditory nerve pathway injury (sensorineural). Damage to the ear’s nerve pathways toward the brain may also cause mixed hearing loss. With Mixed Hearing Loss, both loud and soft sounds may appear muffled, making hearing overall tricky.
With any type of hearing loss, the cause can be natural, genetic, or environmental. To understand the specific type of hearing loss, it’s vital to understand the cause of the hearing damage.
The Four Degrees of Hearing Loss
Four hearing loss degrees range from mild to severe; each recognizes the severity of the ear and hearing damage.
The four levels of hearing loss are classified as mild, moderate, severe, and profound.
- Mild: With mild hearing loss, a regular conversation is not too difficult, but with surrounding noise can be challenging to follow every word. The typical hearing function is impacted in the 25-40 db range, and soft sounds may be challenging.
- Moderate: Sounds less than 40-75 dB’s may be difficult to hear and process. Examples of sounds in this range may be a doorbell ringing, and phone conversations may be garbled.
- Severe: With severe hearing loss, even loud conversations are incomprehensible. A patient will need hearing aids to assist, and middle ear or cochlea implants may be necessary with severe hearing loss.
- Profound: Noise and sound less than 100db’s are impossible to hear. Loud noises such as airplane engines can’t be heard. With profound hearing loss, a cochlea implant may be one of the only remedies available to help the sufferer understand even regular speech.
Conductive Hearing Loss Causes
Most forms of Conductive Hearing Loss (CHL) may be natural or genetic. The various forms of natural hearing loss may be:
- Genetic Factors: Otosclerosis, Usher’s Syndrome, and Pendred Syndrome are common genetic factors in hearing loss.
- Aging: after 65 years old, over 1/3rd of adults experience a form of hearing loss
- Ear wax build-up: Sometimes it’s the production of too much ear wax, but often the cause is due to ear wax being pushed deeper into the ear canal by at-home cleaning or heavy use of ear-phones.
- Infections: Bacterial or Viral infections can cause pain, discomfort, and may impact hearing in the middle ear.
- An injury to the outer, middle, or inner ear and eardrum perforation.
As opposed to Conductive Hearing Loss, the more severe and complex hearing loss of Sensorineural Hearing Loss can be attributable to the following causes:
- Disease and/or cancerous tumors: As with infections, tumors such as acoustic neuroma affect the vestibular and cochlear nerves. Some diseases, such as diabetes, may also harm hearing.
- Head Trauma
- Birth Conditions and malformation of the ear canal: Anotia and microtia occur during the first few weeks of pregnancy and may cause hearing complications.
- Medications, side effects: Aspirin and NSAID’s in large doses, as well as some antibiotics and chemotherapy, may impact hearing.
- Illicit Drug Use
Causes of Mixed Hearing Loss And The Solutions
As discussed, mixed hearing loss occurs when both conductive and sensorineural hearing loss happens. There can be an underlying issue within the ear, and a secondary form of hearing loss happens.
Mixed Hearing Loss’s primary description occurs when there is a combination of external and/or middle ear damage coupled with inner ear cochlea or auditory nerve damage.
Symptoms of mixed hearing loss can range from lower hearing in one ear, known as unilateral hearing loss, or in both ears with a reduction in hearing, known as bilateral hearing loss.
When someone experiences Mixed Hearing Loss, they have symptoms of both Conductive and Sensorineural Hearing Loss (SNHL). That means that similar to SNHL, the inner ear is damaged. Often that damage is irreversible as the cochlea hairs or the auditory nerves have deteriorated.
The Ear Formation and Mixed Hearing Loss
Mixed hearing loss is a combination of both conductive and sensorineural hearing loss, often stemming from a physical blockage in the outer or middle ear, with nerve damage occurring in the inner ear. An examination of the ear, the ear canal, and then the inner ear will damage the patients’ hearing.
The outer ear is the ear lobe, ear canal, and tympanic membrane that separate the outer and middle ear.
The middle ear is defined as the eardrum and the ossicles, three tiny bones that help vibrate sound toward the inner ear.
The inner ear is made of the spiral-shaped cochlea, the cochlea’s small hairs, and the auditory nerves that transmit vibrations to the brain.
The cochlea is spiral and comprises hairs that pass sound waves. The ear with the brabrain’s auditory deterioration is usually gradual, and certain sounds and frequencies may be difficult to hear. Over time this process will continue to deteriorate until the damage is lasting.
Conductive Hearing Loss is the other type of damage that comprises Mixed Hearing Loss. Often this type of hearing is caused by a blockage in the ear canal with various root causes. When both blockage and cochlea damage occurs, this is known as Mixed Hearing Loss.
With conductive hearing loss, corrective procedures such as a medical or surgical correction, while SNHL, or sensorineural hearing loss can be rectified with the utilization of hearing aids.
While too often Mixed Hearing Loss can lead to permanent hearing damage, some corrective procedures are available. These options, however, depending on the range of hearing loss and level of permanent hearing damage that has occurred.
Treatment for Mixed Hearing Loss
With mixed hearing loss, the audiologist must determine the extent of the damage to the outer and middle ear before determining the auditory nerve and inner ear’s damage. Most often, addressing the internal ear damage will create the best path to remedying the issue, often with a surgical procedure.
Once the severity of the hearing loss is determined, treatment toward the outer or middle ear’s blockage will need to be addressed. Depending on the internal ear damage seriousness, a traditional hearing aid or a cochlea implant may be required.
An audiologist will best assess the level of damage and discuss options that may be available.
Drew Sutton M.D.
Drew Sutton, MD is a board-certified otolaryngologist. He has extensive experience and training in sinus and respiratory diseases, ear and skull base surgery, and pulmonary disorders. He has served as a Clinical Instructor at Grady Hospital Emory University for more than 12 years.