Sensorineural Hearing Loss
Sensorineural hearing loss is by far the most common type of hearing loss, with statistics showing that more than 90 percent of people with hearing loss fit into this category. While aging is one of the major causes, there are other situations which can lead to this kind of hearing loss. Sensorineural hearing loss occurs when there is damage to, or deterioration of, the cochlea or auditory nerve. Sensorineural hearing loss is often referred to as “nerve damage” because of its connection to the auditory nerve. In actuality, this type of hearing loss is most often caused by damage to the hair cells on the cochlea. There are two types of sensorineural hearing loss – acquired and congenital. Acquired sensorineural hearing loss develops later; congenital sensorineural hearing loss refers to a loss that is present at birth or right after birth.
What causes acquired sensorineural hearing loss?
The aging process: Presbycusis is the term used to describe sensorineural hearing loss that is result of the aging process. It is the most common type of sensorineural hearing loss in North America and in most cases it occurs gradually, affects both of your ears, and impairs your ability to hear high frequency sounds. To learn more about prebycusis, click here.
Noise: Individuals who live and work in noisy environments are at risk of sensorineural hearing loss. Thankfully, this type of hearing loss can be prevented. To learn more about noise induced hearing loss and prevention, click here.
Diseases and infections: Viral infections, such as measles, mumps and meningitis can cause damage to the inner ear. Meniere’s disease is also connected to sensorineural hearing loss.
Head Injury: A severe blow to the head, sudden changes in pressure, brain hemorrhage or stroke can all cause sensorineural hearing loss.
Certain Medications: A number of drugs can cause hearing loss by affecting the auditory system. The loss may be temporary or permanent depending on the dosage and length of time the drug is taken.
Tumors: Examples include Acoustic Neuroma, a benign tumor that effects the auditory system; and Cholesteatoma, an abnormal skin growth in the middle ear.
What causes congenital sensorineural hearing loss?
Sensorineural hearing loss can also be congenital, meaning that the hearing loss is present at birth. Genetics, premature birth and lack of oxygen during birth are some of the causes of congenital sensorineural hearing loss.
Conductive Hearing Loss
Conductive hearing loss generally occurs in the middle ear. It occurs when sound is not conducted properly as it travels from the outer ear canal to the eardrum and through the three bones of the middle ear (the hammar, anvil, and stirrup). Like sensorineural hearing loss, causes of conductive hearing loss vary but can include:
- fluid in the inner ear
- otoscleroisis – new bone growth around the stapes (stirrup) that affixes to the oval window
- poorly functioning Eustachian tubes
- ear infections
- impacted ear wax
- a foreign object in the ear canal
- a physical malformation within the outer ear, ear canal, or middle ear.
Conductive hearing loss is generally caused by a physical problem within the ear and as a result it can often be corrected or improved by medical means. In other cases individuals with conductive hearing loss may benefit from the use of hearing aids, assistive listening equipment, or cochlear implants.
Mixed Hearing Loss
Sometimes a conductive hearing loss occurs in combination with a sensorineural hearing loss. In other words, there may be damage in the outer or middle ear and also in the inner ear or auditory nerve. When this occurs, the damage is referred to as mixed hearing loss.