About Hearing Loss
Approximately 28 Million Americans are estimated to have some type of hearing impairment. Hearing loss affects people of all ages and from all walks of life. Among older people, it is the most common health problem, second only to arthritis.
There are many causes of hearing loss. In many cases, hearing loss happens gradually and generally worsens with age. Hearing loss caused by aging is known as presbycusis. Disease, infection, heredity, head trauma, exposure to loud noise and certain medications may also cause hearing loss. In some cases, the cause of hearing loss is unknown.
Types of Hearing Loss
Hearing loss is described by varying degrees, not percentages. Hearing loss may be mild, moderate, moderately-severe, severe or profound and vary across pitches. It is determined by a simple hearing test as the amount of volume loss you experience compared to an average of many other adult listeners with normal auditory systems. The volume, or intensity, of sounds you hear is measured in decibels (dB), 0 dB being the softest whisper and 120 dB being a jet engine. The softest sounds one can hear are called thresholds. Normal hearing thresholds for adults are considered 0 to 25 dB.
Sensorineural Hearing Loss
Sensorineural (sen-sory-nuhral) hearing loss is caused by inner ear damage. Sometimes referred to as “nerve losses”, these comprise 95% of all hearing losses. Some causes include aging, noise exposure, heredity, viral infection to the brain such as meningitis, and in rare cases, ototoxic medications. The majority of sensorineural hearing loss occurs as a result of an abnormality or damage to the hair cells in the cochlea. This abnormality prevents sound from being transmitted to the brain normally, resulting in a hearing loss.
Sensorineural hearing losses are generally permanent and may stay stable or worsen over time. Routine hearing tests are needed to monitor the hearing loss. Amplification, including hearing aids or cochlear implants in the most severe cases, is a common treatment recommendation.
Individuals with sensorineural hearing loss may report muffled speech, ringing in the ears (tinnitus), difficulty hearing in background noise or that others do not speak clearly.
Conductive Hearing Loss
Conductive hearing loss occurs when there is a problem with the way sound is conducted to the inner ear or cochlea. The problem may lie in the outer ear (pinna or ear canal), eardrum (tympanic membrane), or the middle ear (ossicles and Eustachian tube). The inner ear remains unaffected in this type of hearing loss.
Some causes of conductive hearing losses are obstruction of the ear canal by impacted earwax, head trauma affecting the middle ear bones, perforation of the eardrum, fluid build up in the middle ear, and otosclerosis (a stiffening of the middle ear bones). About 5% of hearing losses are conductive in nature, and many can be treated medically.
Conductive hearing losses may be temporary or permanent, depending on the source of the problem. Medical management can correct some cases of conductive hearing loss, while amplification may be a recommended treatment option in more long-standing or permanent cases.
Individuals with conductive hearing loss may report that sounds are muffled or quiet. Generally, when sounds are made louder, these individuals can hear well again.
Mixed Hearing Loss
Mixed hearing loss occurs when a person has an existing sensorineural hearing loss in combination with a conductive hearing loss. It is, very literally, a mix of sensorineural and conductive hearing losses. This means there is a problem in the inner ear as well as in the outer or middle ear. The conductive hearing loss may be temporary or permanent, depending on the source of the problem.
Mixed hearing loss can sometimes be treated with medical management, and hearing aids are a common treatment recommendation.
Neural Hearing Loss
Neural hearing loss occurs when the auditory nerve that carries impulses from the cochlea to the brain is missing or abnormal. It is difficult to determine the exact location of neural hearing loss. Some causes of neural hearing loss include genetics, acoustic tumors, in-utero exposure to certain infections, severe jaundice in infancy and low birth weight associated with premature birth.
Amplification may be recommended in some cases of neural hearing loss depending on the severity of the damage to the hearing nerve.
Individuals with neural hearing loss often have difficulty understanding speech, even when it is loud enough, as well as in background noise.