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 diagnostic hearing assessment. During this process, we determine the amount of volume, or intensity needed to stimulate your hearing system at various pitches. We then compare this data to individuals with normal auditory systems, giving us your hearing loss severity.
We measure sound in decibels (dB), and the softest decibel level you can hear is considered to be your hearing thresholds. Normal hearing thresholds for adults are considered to be 20dB or less.
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.
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.
Common Causes of Conductive Hearing Loss include:
- Outer ear infection (otitis external or "swimmer's ear")
- Middle ear infection (otitis media)
- Negative middle ear pressue (Eustachian tube dysfunction)
- Complete cerumen occlusion (wax blockage)
- Deterioration of the middle ear ossicles (bones)
- Otosclerosis - fixation of the ossicles
- Perforated tympanic membrane (TM) - hole in the eardrum
- Absence of the outer ear or middle ear structure (e.g. atresia)
Individuals with conductive hearing loss may report that sounds are muffled or quiet. Most individuals with conductive hearing losses do extremely well with amplification (i.e.hearing aids) because their inner ears are unaffected. This means that once sounds reach the inner ear, their hearing system works very well. In rare cases, individual get limited benefit from acoustic hearing aids because there is too much damage to the middle ear or because of chronic drainage. In these instances, a referral for a Bone Anchored Hearing System (BAHA) is made.
If a conductive hearing loss is diagnosed, a referral to an Otolaryngologist (ENT) is recommended to investigate the cause, prognosis and explore any available medical treatments (e.g. surgery, medications, etch.)
Sensorineural Hearing Loss
Sensorineural (sen-sory-nuhral) hearing loss occurs when there is a problem with the sensory receptors of the hearing system, specifically in the cochlea of the inner ear. 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. When the damage is related to the sensory receptors in the inner ear we classify it as a "sensory"hearing loss. When the damage is attributable to the nerve pathways beyond the cochlear (i.e. in the nerves that travel from the inner ear to the brain) we refer to it as a "neural" hearing loss. However, it is usually impossible to determine how much of hearing loss is directly related to sensory damage and how much is related to neural damage - this is where we get the name sensorineural (sensory + neural).
Common Causes of Sensorineural Hearing Loss:
- Presbycusis - hair cells in the inner ear are damaged as a result of the aging process. Certain parts of the inner ear simply "wear out" over time, resulting in age-related hearing loss.
- Noise exposure - damage to the hair cells and sensitive nerve endings in the inner ear as a result of exposure to intense sound pressure (i.e. loud sound). This damage usually occurs over a period of time, but can also be instantaneous if the sound is intense enough (acoustic trauma).
- Other hair cell damage - hair cells in the inner ear can also become damaged due to genetics, infection, drugs (ototoxic medications) trauma or other medical conditions such as diabetes, kidney disease, thyroid function and hypertension.
- Congenital - inner ear damage present from birth.
Sensorineural hearing losses are usually 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), is usually the best treatment option.
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.
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. As with conductive hearing losses, a referral to an Otolaryngologist/ENT is recommended to investigate the conductive portion of the hearing loss to explore medical treatment options. However, the sensorineural portion of the hearing loss is best treated with hearing aids. Typical treatment involves both amplification (hearing aids) and a medical work-up by an ENT
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 but it is somewhere in the nerves that carry auditory information from the inner ear to the brain.
Common Causes of Neural Hearing Loss;
- Head trauma
- In-utero exposure to certain infections
- Low birth weight associated with premature birth
Individual with neural hearing loss often have difficulty understanding speech, even when it is loud enough, as well as in background noise. Amplification may be recommended in some cases of neural hearing loss depending on the severity of the damage to the hearing nerve. Diagnosing neural hearing loss is extremely difficult - for this reason it usually get grouped under the category of sensorineural hearing loss.
Sudden Hearing Loss
Sudden changes to hearing can occur for a multitude of factors and are considered a Medical Emergence. Ranging from less severe causes such as a wax blockage in the ear canal to more severe causes such as viral infections, membrane ruptures, or tumors. If you experience a sudden drop in your hearing, you should seek medical attention IMMEDATELY. The effectiveness of certain treatments for sudden sensorineural hearing loss (SSNHL) greatly reduce if they are not started within 48 hours of onset. For some sudden sensorineural hearing losses, our likelihood of treating the loss greatly worsens the longer we wait.
SSNHL is usually unilateral in nature (i.e. only in one ear). Some medical doctors and other health practitioners are unaware of the severity and time sensitivity of sudden hearing losses. Unfortunately treatment is often missed or prolonged because of misdiagnosis. If you or someone you know has experienced a sudden change in hearing, call us to book an appointment immediately or seen medical attention as soon as possible.