About Hearing Loss
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 (PTA) 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 to range from 0 to 20 dB although some people have hearing measured in the negative dB range
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 loss can include outer or middle ear infections, complete earwax blockage, deterioration of the middle ear bones (ossicles), fixation of the ossicles (otosclerosis), a hole in the tympanic membrane, or absence of the outer ear or middle ear structures.
Conductive hearing losses may be temporary or permanent, depending on the cause. Medical or surgical 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.
Sensory Hearing Loss
Sensorineural (sen-sory-nuhral) hearing loss occurs when there is a problem with the sensory receptors of the cochlea (inner ear). The majority of sensory hearing loss occurs as a result of an abnormality or damage to the nerve cells in the cochlea.
The inner ear nerve cells may have been abnormal since birth (congenital), damaged as a result of genetic defects, infection or drugs during pregnancy. It may be caused by trauma to the ear or head, over-exposure to noise, or most commonly, due to the natural degeneration of the ageing process, known as presbycusis (pres-be-cue-sis).
Sensory hearing losses are generally permanent and may remain 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, are common treatment options.
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.
Neural Hearing Loss
Neural hearing loss occurs as a result of abnormalities of the auditory nerve that carries impulses from the cochlea nerve cells to the auditory centre in the brain. It is difficult to determine the exact location of neural hearing loss. Some causes of neural hearing loss include genetic defects, infections or benign tumours of the auditory nerve, 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.
Sensorineural Hearing Loss
It is often difficult to determine whether the cause of a loss is in the inner ear (cochlea) or the neural pathway from the ear to the auditory centre in the brain and so it is commonly referred to as sensorineural hearing loss.
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.